diff --git a/src/db/unit_tests/dbAsIfFlatRegionTests.cc b/src/db/unit_tests/dbAsIfFlatRegionTests.cc
new file mode 100644
index 000000000..8cabfa716
--- /dev/null
+++ b/src/db/unit_tests/dbAsIfFlatRegionTests.cc
@@ -0,0 +1,1712 @@
+
+/*
+
+  KLayout Layout Viewer
+  Copyright (C) 2006-2023 Matthias Koefferlein
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+
+#include "dbHierarchyBuilder.h"
+#include "dbReader.h"
+#include "dbTestSupport.h"
+#include "dbRegion.h"
+#include "dbEdges.h"
+#include "dbRegionUtils.h"
+#include "dbRegionProcessors.h"
+#include "dbEdgesUtils.h"
+#include "dbDeepShapeStore.h"
+#include "dbOriginalLayerRegion.h"
+#include "dbCellGraphUtils.h"
+#include "dbTestSupport.h"
+#include "tlUnitTest.h"
+#include "tlStream.h"
+
+TEST(1_Basic)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+
+  db::Layout target;
+
+  //  deliberately using vector to force reallocation ...
+  std::vector<db::Region> regions;
+  std::vector<unsigned int> target_layers;
+
+  for (db::Layout::layer_iterator li = ly.begin_layers (); li != ly.end_layers (); ++li) {
+
+    unsigned int li1 = (*li).first;
+    db::RecursiveShapeIterator iter (ly, ly.cell (top_cell_index), li1);
+    target_layers.push_back (target.insert_layer (*(*li).second));
+
+    regions.push_back (db::Region (iter));
+
+    size_t n = 0, nhier = 0;
+    db::CellCounter cc (&ly);
+    for (db::Layout::top_down_const_iterator c = ly.begin_top_down (); c != ly.end_top_down (); ++c) {
+      size_t ns = 0;
+      for (db::Shapes::shape_iterator is = ly.cell (*c).shapes (li1).begin (db::ShapeIterator::Regions); !is.at_end (); ++is) {
+        ++ns;
+      }
+      n += cc.weight (*c) * ns;
+      nhier += ns;
+    }
+
+    EXPECT_EQ (db::Region (iter).count (), n);
+    EXPECT_EQ (regions.back ().count (), n);
+    EXPECT_EQ (regions.back ().hier_count (), nhier);
+    EXPECT_EQ (regions.back ().bbox (), db::Region (iter).bbox ());
+    EXPECT_EQ (regions.back ().is_merged (), false);
+
+  }
+
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  for (std::vector<db::Region>::const_iterator r = regions.begin (); r != regions.end (); ++r) {
+    target.insert (target_top_cell_index, target_layers [r - regions.begin ()], *r);
+  }
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au1.gds");
+
+  //  some operations
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  db::Region r2 (db::RecursiveShapeIterator (ly, ly.cell (top_cell_index), l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, ly.cell (top_cell_index), l3));
+
+  EXPECT_EQ (r2.is_merged (), false);
+  r2.merge ();
+  EXPECT_EQ (r2.is_merged (), true);
+  r2 += r3;
+  EXPECT_EQ (r2.is_merged (), false);
+  EXPECT_EQ (r2.merged ().is_merged (), true);
+  EXPECT_EQ (r2.is_merged (), false);
+  r2.merge ();
+  EXPECT_EQ (r2.is_merged (), true);
+  r2.flatten ();
+  EXPECT_EQ (r2.is_merged (), true);
+  r2.insert (db::Box (0, 0, 1000, 2000));
+  EXPECT_EQ (r2.is_merged (), false);
+}
+
+TEST(2)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+
+  db::Layout target;
+
+  //  deliberately using vector to force reallocation ...
+  std::vector<std::pair<db::Region, unsigned int> > regions;
+
+  for (db::Layout::layer_iterator li = ly.begin_layers (); li != ly.end_layers (); ++li) {
+
+    unsigned int li1 = (*li).first;
+    unsigned int tl = target.insert_layer (*(*li).second);
+
+    db::RecursiveShapeIterator iter1 (ly, ly.cell (top_cell_index), li1, db::Box (2000, -1000, 6000, 4000));
+    regions.push_back (std::make_pair (db::Region (iter1), tl));
+
+    db::RecursiveShapeIterator iter2 (ly, ly.cell (top_cell_index), li1, db::Box (14000, 0, 20000, 3000));
+    regions.push_back (std::make_pair (db::Region (iter2), tl));
+
+  }
+
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  for (std::vector<std::pair<db::Region, unsigned int> >::const_iterator r = regions.begin (); r != regions.end (); ++r) {
+    target.insert (target_top_cell_index, r->second, r->first);
+  }
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au2.gds");
+}
+
+TEST(3_BoolAndNot)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  unsigned int l42 = ly.get_layer (db::LayerProperties (42, 0));
+
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r42 (db::RecursiveShapeIterator (ly, top_cell, l42));
+  db::Region box (db::Box (2000, -1000, 6000, 4000));
+
+  db::Region r2minus3   = r2 - r3;
+  db::Region r2minusbox = r2 - box;
+  db::Region r2minus42  = r2 - r42;
+  db::Region rboxminus3 = box - r3;
+  db::Region r42minus3  = r42 - r3;
+  db::Region r42minus42 = r42 - r42;
+
+  db::Region tr2minus3   = r2.andnot (r3).second;
+  db::Region tr2minusbox = r2.andnot (box).second;
+  db::Region tr2minus42  = r2.andnot (r42).second;
+  db::Region trboxminus3 = box.andnot (r3).second;
+  db::Region tr42minus3  = r42.andnot (r3).second;
+  db::Region tr42minus42 = r42.andnot (r42).second;
+
+  db::Region r2and3   = r2 & r3;
+  db::Region r2andbox = r2 & box;
+  db::Region r2and42  = r2 & r42;
+  db::Region rboxand3 = box & r3;
+  db::Region r42and3  = r42 & r3;
+  db::Region r42and42 = r42 & r42;
+
+  db::Region tr2and3   = r2.andnot (r3).first;
+  db::Region tr2andbox = r2.andnot (box).first;
+  db::Region tr2and42  = r2.andnot (r42).first;
+  db::Region trboxand3 = box.andnot (r3).first;
+  db::Region tr42and3  = r42.andnot (r3).first;
+  db::Region tr42and42 = r42.andnot (r42).first;
+
+  EXPECT_EQ (r2and3.is_merged (), false);
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2minus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2minusbox);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2minus42);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), rboxminus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r42minus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), r42minus42);
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r2and3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r2andbox);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r2and42);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), rboxand3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (24, 0)), r42and3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (25, 0)), r42and42);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au3.gds");
+  }
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), tr2minus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), tr2minusbox);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), tr2minus42);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), trboxminus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), tr42minus3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), tr42minus42);
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), tr2and3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), tr2andbox);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), tr2and42);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), trboxand3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (24, 0)), tr42and3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (25, 0)), tr42and42);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au3b.gds");
+  }
+}
+
+TEST(4_Add)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  unsigned int l42 = ly.get_layer (db::LayerProperties (42, 0));
+
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r42 (db::RecursiveShapeIterator (ly, top_cell, l42));
+  db::Region box (db::Box (2000, -1000, 6000, 4000));
+  db::Region r2box (db::RecursiveShapeIterator (ly, top_cell, l2, box));
+  db::Region r3box (db::RecursiveShapeIterator (ly, top_cell, l3, box));
+
+  //  intra-layout
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2 + r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r42 + r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2 + r42);
+
+    db::Region rnew2 = r2;
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), rnew2);
+    rnew2 += r3;
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), rnew2);
+    rnew2 += r42;
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), rnew2);
+
+    db::Region rnew42 = r42;
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), rnew42);
+    rnew42 += r2;
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), rnew42);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au4a.gds");
+  }
+
+  //  inter-layout
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2box + r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2 + r3box);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2box + r3box);
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), box + r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r2 + box);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au4b.gds");
+  }
+}
+
+TEST(5_BoolXOR)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  unsigned int l42 = ly.get_layer (db::LayerProperties (42, 0));
+
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r42 (db::RecursiveShapeIterator (ly, top_cell, l42));
+  db::Region box (db::Box (2000, -1000, 6000, 4000));
+
+  db::Region r2xor3   = r2 ^ r3;
+  db::Region r2xorbox = r2 ^ box;
+  db::Region r2xor42  = r2 ^ r42;
+  db::Region rboxxor3 = box ^ r3;
+  db::Region r42xor3  = r42 ^ r3;
+  db::Region r42xor42 = r42 ^ r42;
+
+  EXPECT_EQ (r2xor3.is_merged (), false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2xor3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2xorbox);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2xor42);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), rboxxor3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r42xor3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), r42xor42);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au5.gds");
+}
+
+TEST(7_Merge)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l6 = ly.get_layer (db::LayerProperties (6, 0));
+
+  db::Region r6 (db::RecursiveShapeIterator (ly, top_cell, l6));
+
+  db::Region r6_merged = r6.merged ();
+  db::Region r6_merged_minwc = r6.merged (false, 1);
+
+  db::Region r6_minwc = r6;
+  r6_minwc.merge (false, 1);
+
+  r6.merge ();
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r6);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r6_minwc);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r6_merged);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r6_merged_minwc);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au7.gds");
+}
+
+TEST(8_AreaAndPerimeter)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  EXPECT_EQ (r1.area (), db::coord_traits<db::Coord>::area_type (9722000000));
+  EXPECT_EQ (r1.perimeter (), db::coord_traits<db::Coord>::perimeter_type (1360000));
+
+  EXPECT_EQ (r1.area (r1.bbox ()), db::coord_traits<db::Coord>::area_type (9722000000));
+  EXPECT_EQ (r1.perimeter (r1.bbox ()), db::coord_traits<db::Coord>::perimeter_type (1360000));
+
+  EXPECT_EQ (r1.area (db::Box (40000, -90000, 50000, -80000)), db::coord_traits<db::Coord>::area_type (100000000));
+  EXPECT_EQ (r1.perimeter (db::Box (40000, -90000, 50000, -80000)), db::coord_traits<db::Coord>::perimeter_type (0));
+  EXPECT_EQ (r1.area (db::Box (-40000, -90000, -50000, -80000)), db::coord_traits<db::Coord>::area_type (0));
+}
+
+TEST(9_SizingSimple)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l6 = ly.get_layer (db::LayerProperties (6, 0));
+
+  db::Region r6 (db::RecursiveShapeIterator (ly, top_cell, l6));
+  db::Region r6_sized = r6.sized (-50);
+  EXPECT_EQ (r6_sized.is_merged (), true);
+  db::Region r6_sized_aniso = r6.sized (-20, -100, 2);
+  EXPECT_EQ (r6_sized_aniso.is_merged (), true);
+  db::Region r6_sized_plus = r6.sized (50);
+  EXPECT_EQ (r6_sized_plus.is_merged (), false);
+  db::Region r6_sized_aniso_plus = r6.sized (20, 100, 2);
+  EXPECT_EQ (r6_sized_aniso_plus.is_merged (), false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r6);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r6_sized);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r6_sized_aniso);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r6_sized_plus);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r6_sized_aniso_plus);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au9a.gds");
+}
+
+TEST(10_HullsAndHoles)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r1_sized = r1.sized (2000);
+  r1_sized -= r1;
+
+  db::Region hulls = r1_sized.hulls ();
+  db::Region holes = r1_sized.holes ();
+  EXPECT_EQ (hulls.is_merged (), false);
+  EXPECT_EQ (holes.is_merged (), false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1_sized);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), hulls);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), holes);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au10.gds");
+}
+
+TEST(11_RoundAndSmoothed)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r1_sized = r1.sized (2000);
+  r1_sized -= r1;
+
+  db::Region rounded = r1_sized.rounded_corners (3000, 5000, 100);
+  db::Region smoothed = rounded.smoothed (100, false);
+  db::Region smoothed_keep_hv = rounded.smoothed (100, true);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1_sized);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), rounded);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), smoothed);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), smoothed_keep_hv);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au11.gds");
+}
+
+TEST(12_GridSnap)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r3snapped = r3.snapped (50, 50);
+  EXPECT_EQ (r3snapped.is_merged (), false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r3snapped);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au12.gds");
+}
+
+TEST(13_Edges)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Edges r3edges = r3.edges ();
+  EXPECT_EQ (r3edges.is_merged (), false);
+
+  db::EdgeLengthFilter f (0, 500, true);
+  db::Edges r3edges_filtered = r3.edges (f);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r3edges);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r3edges_filtered);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au13.gds");
+}
+
+TEST(13b_Edges)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_edges.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Edges r1edges = r1.edges ();
+  EXPECT_EQ (r1edges.is_merged (), false);
+
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Edges r2edges = r2.edges ();
+  EXPECT_EQ (r2edges.is_merged (), false);
+
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), r2);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r1edges);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2edges);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au13b.gds");
+}
+
+TEST(14_Interacting)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l6 = ly.get_layer (db::LayerProperties (6, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r6 (db::RecursiveShapeIterator (ly, top_cell, l6));
+  db::Region r1f (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r1r = r1;
+  r1r.set_merged_semantics (false);
+  db::Region r2r = r2;
+  r2r.set_merged_semantics (false);
+  db::Region r6r = r6;
+  r6r.set_merged_semantics (false);
+
+  db::Edges r1e = r1.edges ();
+  db::Edges r1ef = r1f.edges ();
+  db::Edges r1er = r1r.edges ();
+  r1er.set_merged_semantics (false);
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2.selected_interacting (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.selected_not_interacting (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2.selected_inside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r2.selected_not_inside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r2.selected_outside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), r2.selected_not_outside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (16, 0)), r2.selected_overlapping (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (17, 0)), r2.selected_not_overlapping (r1));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r6.selected_interacting (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r6.selected_not_interacting (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r6.selected_inside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), r6.selected_not_inside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (24, 0)), r6.selected_outside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (25, 0)), r6.selected_not_outside (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (26, 0)), r6.selected_overlapping (r1));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (27, 0)), r6.selected_not_overlapping (r1));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r2.selected_interacting (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), r2.selected_not_interacting (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (32, 0)), r2.selected_inside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (33, 0)), r2.selected_not_inside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (34, 0)), r2.selected_outside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (35, 0)), r2.selected_not_outside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (36, 0)), r2.selected_overlapping (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (37, 0)), r2.selected_not_overlapping (r1f));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (40, 0)), r6.selected_interacting (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (41, 0)), r6.selected_not_interacting (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (42, 0)), r6.selected_inside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (43, 0)), r6.selected_not_inside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (44, 0)), r6.selected_outside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (45, 0)), r6.selected_not_outside (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (46, 0)), r6.selected_overlapping (r1f));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (47, 0)), r6.selected_not_overlapping (r1f));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (50, 0)), r2r.selected_interacting (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (51, 0)), r2r.selected_not_interacting (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (52, 0)), r2r.selected_inside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (53, 0)), r2r.selected_not_inside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (54, 0)), r2r.selected_outside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (55, 0)), r2r.selected_not_outside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (56, 0)), r2r.selected_overlapping (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (57, 0)), r2r.selected_not_overlapping (r1r));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (60, 0)), r6r.selected_interacting (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (61, 0)), r6r.selected_not_interacting (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (62, 0)), r6r.selected_inside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (63, 0)), r6r.selected_not_inside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (64, 0)), r6r.selected_outside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (65, 0)), r6r.selected_not_outside (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (66, 0)), r6r.selected_overlapping (r1r));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (67, 0)), r6r.selected_not_overlapping (r1r));
+
+    EXPECT_EQ (r2.selected_interacting (r1).is_merged (), true);
+    EXPECT_EQ (r2r.selected_interacting (r1).is_merged (), false);
+    EXPECT_EQ (r2r.selected_interacting (r1.merged ()).is_merged (), false);
+    EXPECT_EQ (r2.selected_interacting (r1r).is_merged (), true);
+    EXPECT_EQ (r2.selected_inside (r1).is_merged (), true);
+    EXPECT_EQ (r2r.selected_inside (r1).is_merged (), false);
+    EXPECT_EQ (r2.selected_inside (r1).is_merged (), true);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au14a.gds");
+  }
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r6);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r1e);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r6.selected_interacting (r1e));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r6.selected_not_interacting (r1e));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r6.selected_interacting (r1ef));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), r6.selected_not_interacting (r1ef));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (32, 0)), r6r.selected_interacting (r1er));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (33, 0)), r6r.selected_not_interacting (r1er));
+
+    EXPECT_EQ (r6.selected_interacting (r1e).is_merged (), true);
+    EXPECT_EQ (r6.selected_interacting (r1er).is_merged (), true);
+    EXPECT_EQ (r6r.selected_interacting (r1e).is_merged (), false);
+    EXPECT_EQ (r6r.selected_interacting (r1er).is_merged (), false);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au14b.gds");
+  }
+}
+
+TEST(15_Filtered)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::RegionAreaFilter af1 (0, 1000000000, false);
+  db::Region af1_filtered = r1.filtered (af1);
+  db::RegionAreaFilter af1inv (0, 1000000000, true);
+  db::Region af1_else = r1.filtered (af1inv);
+  EXPECT_EQ (af1_filtered.is_merged (), true);
+  EXPECT_EQ (af1_else.is_merged (), true);
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), af1_filtered);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), af1_else);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au15a.gds");
+  }
+
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::RegionBBoxFilter bwf (0, 50000, false, db::RegionBBoxFilter::BoxWidth);
+  db::RegionBBoxFilter bhf (0, 50000, false, db::RegionBBoxFilter::BoxHeight);
+  db::Region r2_bwf = r2.filtered (bwf);
+  db::Region r2_bhf = r2.filtered (bhf);
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2_bwf);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2_bhf);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au15b.gds");
+  }
+}
+
+TEST(16_MergeWithMinWC)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r1_merged_wc0 = r1.merged (true, 0);
+  db::Region r1_merged_wc1 = r1.merged (true, 1);
+  db::Region r1_merged_wc2 = r1.merged (true, 2);
+  EXPECT_EQ (r1_merged_wc0.is_merged (), true);
+  EXPECT_EQ (r1_merged_wc1.is_merged (), true);
+  EXPECT_EQ (r1_merged_wc2.is_merged (), true);
+
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1_merged_wc0);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r1_merged_wc1);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r1_merged_wc2);
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au16.gds");
+  }
+}
+
+TEST(17_SinglePolygonChecks)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  unsigned int l6 = ly.get_layer (db::LayerProperties (6, 0));
+  unsigned int l4 = ly.get_layer (db::LayerProperties (4, 0));
+
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r6 (db::RecursiveShapeIterator (ly, top_cell, l6));
+  db::Region r4 (db::RecursiveShapeIterator (ly, top_cell, l4));
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (3, 0)), r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (4, 0)), r4);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (6, 0)), r6);
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r3.width_check (260, db::RegionCheckOptions (false, db::Euclidian, 90, 0)));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r3.width_check (260, db::RegionCheckOptions (true, db::Projection, 90, 2000)));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r6.notch_check (1300, db::RegionCheckOptions (false, db::Euclidian, 90, 0)));
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au17.gds");
+  }
+}
+
+TEST(18_MultiPolygonChecks)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+  unsigned int l6 = ly.get_layer (db::LayerProperties (6, 0));
+  unsigned int l4 = ly.get_layer (db::LayerProperties (4, 0));
+
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r6 (db::RecursiveShapeIterator (ly, top_cell, l6));
+  db::Region r4 (db::RecursiveShapeIterator (ly, top_cell, l4));
+
+  {
+    db::Layout target;
+    unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (3, 0)), r3);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (4, 0)), r4);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (6, 0)), r6);
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r3.space_check (500, db::RegionCheckOptions (false, db::Projection, 90, 0)));
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r3.space_check (500, db::RegionCheckOptions (true, db::Projection, 90, 300)));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r3.separation_check (r4, 200, db::RegionCheckOptions (false, db::Projection, 90, 0)));
+
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r6.enclosing_check (r4, 100, db::RegionCheckOptions (true, db::Projection, 90, 0)));
+
+    CHECKPOINT();
+    db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au18.gds");
+  }
+}
+
+TEST(19_GridCheck)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r3_gc1;
+  r3.grid_check (25, 25).polygons (r3_gc1, 100);
+  db::Region r3_gc2;
+  r3.grid_check (40, 40).polygons (r3_gc2, 100);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r3);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r3_gc1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r3_gc2);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au19.gds");
+}
+
+TEST(20_AngleCheck)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/angle_check_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::EdgePairs ep1_ac1 = r1.angle_check (0, 91, true);
+  db::EdgePairs ep1_ac2 = r1.angle_check (0, 45, false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), ep1_ac1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (3, 0)), ep1_ac2);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au20.gds");
+}
+
+TEST(21_Processors)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1.processed (db::CornersAsDots (-180.0, true, 180.0, true)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r1.processed (db::CornersAsDots (0.0, true, 180.0, true)));
+  db::Region ext;
+  r1.processed (db::CornersAsDots (0.0, true, 180.0, true)).extended (ext, 1000, 1000, 2000, 2000);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), ext);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r1.processed (db::CornersAsRectangles (-180.0, true, 180.0, true, 2000)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r1.processed (db::CornersAsRectangles (0.0, true, 180.0, true, 2000)));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r1.processed (db::extents_processor<db::Polygon> (0, 0)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r1.processed (db::extents_processor<db::Polygon> (1000, 2000)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r1.processed (db::RelativeExtents (0, 0, 1.0, 1.0, 0, 0)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), r1.processed (db::RelativeExtents (0.25, 0.4, 0.75, 0.6, 1000, 2000)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (24, 0)), r1.processed (db::RelativeExtentsAsEdges (0, 0, 1.0, 1.0)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (25, 0)), r1.processed (db::RelativeExtentsAsEdges (0.5, 0.5, 0.5, 0.5)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (26, 0)), r1.processed (db::RelativeExtentsAsEdges (0.25, 0.4, 0.75, 0.6)));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r1.processed (db::minkowski_sum_computation<db::Box> (db::Box (-1000, -2000, 3000, 4000))));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), r1.processed (db::minkowski_sum_computation<db::Edge> (db::Edge (-1000, 0, 3000, 0))));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (40, 0)), r1.processed (db::TrapezoidDecomposition (db::TD_htrapezoids)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (41, 0)), r1.processed (db::ConvexDecomposition (db::PO_vertical)));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (42, 0)), r1.processed (db::ConvexDecomposition (db::PO_horizontal)));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au21.gds");
+}
+
+TEST(22_TwoLayoutsWithDifferentDBU)
+{
+  db::Layout ly1;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly1);
+  }
+
+  db::cell_index_type top_cell_index1 = *ly1.begin_top_down ();
+  db::Cell &top_cell1 = ly1.cell (top_cell_index1);
+
+  db::Layout ly2;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_area_peri_l1_dbu2.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly2);
+  }
+
+  db::cell_index_type top_cell_index2 = *ly2.begin_top_down ();
+  db::Cell &top_cell2 = ly2.cell (top_cell_index2);
+
+  unsigned int l11 = ly1.get_layer (db::LayerProperties (1, 0));
+  db::Region r11 (db::RecursiveShapeIterator (ly1, top_cell1, l11));
+
+  unsigned int l12 = ly2.get_layer (db::LayerProperties (2, 0));
+  db::Region r12 (db::RecursiveShapeIterator (ly2, top_cell2, l12), db::ICplxTrans (ly2.dbu () / ly1.dbu ()));
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly1.cell_name (top_cell_index1));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r11.sized (1000) ^ r12);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au22.gds");
+}
+
+TEST(27a_snap)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/scale_and_snap.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  r1.set_merged_semantics (false);
+  db::Region r2 = r1.snapped (19, 19);
+
+  r2.insert_into (&ly, top_cell_index, ly.get_layer (db::LayerProperties (100, 0)));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testdata () + "/algo/flat_region_au27.gds");
+}
+
+TEST(27b_snap)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/scale_and_snap.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  r1.set_merged_semantics (false);
+  r1.snap (19, 19);
+
+  r1.insert_into (&ly, top_cell_index, ly.get_layer (db::LayerProperties (100, 0)));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testdata () + "/algo/flat_region_au27.gds");
+}
+
+TEST(28a_snap)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/scale_and_snap.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  r1.set_merged_semantics (false);
+  db::Region r2 = r1.scaled_and_snapped (19, 2, 10, 19, 2, 10);
+
+  r2.insert_into (&ly, top_cell_index, ly.get_layer (db::LayerProperties (100, 0)));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testdata () + "/algo/flat_region_au28.gds");
+}
+
+TEST(28b_snap)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/scale_and_snap.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  r1.set_merged_semantics (false);
+  r1.scale_and_snap (19, 2, 10, 19, 2, 10);
+
+  r1.insert_into (&ly, top_cell_index, ly.get_layer (db::LayerProperties (100, 0)));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testdata () + "/algo/flat_region_au28.gds");
+}
+
+TEST(29_InteractionsWithTexts)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_texts_l2.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l8 = ly.get_layer (db::LayerProperties (8, 0));
+
+  db::Texts texts2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region polygons8 (db::RecursiveShapeIterator (ly, top_cell, l8));
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  db::Region polygons;
+  polygons = polygons8.selected_interacting (texts2);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), polygons);
+
+  polygons = polygons8.selected_not_interacting (texts2);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), polygons);
+
+  {
+    db::Region polygons8_copy = polygons8;
+    polygons8_copy.select_interacting (texts2);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), polygons8_copy);
+  }
+
+  {
+    db::Region polygons8_copy = polygons8;
+    polygons8_copy.select_not_interacting (texts2);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), polygons8_copy);
+  }
+
+  {
+    db::Texts t = polygons8.pull_interacting (texts2);
+    target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), t);
+  }
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au29.gds");
+}
+
+TEST(30a_interact_with_count_region)
+{
+  db::Layout ly;
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Cell &top = ly.cell (ly.add_cell ("TOP"));
+  db::cell_index_type ci1 = ly.add_cell ("C1");
+  db::Cell &c1 = ly.cell (ci1);
+  db::cell_index_type ci2 = ly.add_cell ("C2");
+  db::Cell &c2 = ly.cell (ci2);
+  top.insert (db::CellInstArray (db::CellInst (ci1), db::Trans ()));
+  top.insert (db::CellInstArray (db::CellInst (ci2), db::Trans ()));
+
+  c1.shapes (l1).insert (db::Box (db::Point (0, 0), db::Point (100, 200)));
+  c1.shapes (l1).insert (db::Box (db::Point (-100, -100), db::Point (0, 0)));
+
+  c2.shapes (l2).insert (db::Box (db::Point (-10, -10), db::Point (10, 0)));
+  c2.shapes (l2).insert (db::Box (db::Point (-10, 0), db::Point (10, 10)));
+  c2.shapes (l2).insert (db::Box (db::Point (-110, -10), db::Point (-90, 10)));
+  c2.shapes (l2).insert (db::Box (db::Point (-110, -210), db::Point (-90, -190)));
+
+  ly.copy_layer (l2, l3);
+  top.shapes (l2).insert (db::Box (db::Point (90, -10), db::Point (110, 10)));
+  top.shapes (l2).insert (db::Box (db::Point (-110, -110), db::Point (-90, -90)));
+
+  db::Region r (db::RecursiveShapeIterator (ly, top, l1));
+  r.set_merged_semantics (true);
+  r.set_min_coherence (false);
+
+  db::Region empty;
+
+  db::Region rr (db::RecursiveShapeIterator (ly, top, l2));
+  db::Region rr2 (db::RecursiveShapeIterator (ly, top, l3));
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 5, 5).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 2, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 4, 5).to_string (), "");
+
+  EXPECT_EQ (r.selected_not_interacting (empty).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  //  Shortcut delivers clone of original, not merged one:
+  //    EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  //  so that is:
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 4, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 5, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 2, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+
+  r.set_merged_semantics (false);
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 1, 4), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 2, 4), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+
+  EXPECT_EQ (db::compare (r.selected_not_interacting (empty), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_not_interacting (rr, 2, 1), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "(0,0;0,200;100,200;100,0)");
+}
+
+TEST(30b_interact_with_count_edge)
+{
+  db::Layout ly;
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Cell &top = ly.cell (ly.add_cell ("TOP"));
+  db::cell_index_type ci1 = ly.add_cell ("C1");
+  db::Cell &c1 = ly.cell (ci1);
+  db::cell_index_type ci2 = ly.add_cell ("C2");
+  db::Cell &c2 = ly.cell (ci2);
+  top.insert (db::CellInstArray (db::CellInst (ci1), db::Trans ()));
+  top.insert (db::CellInstArray (db::CellInst (ci2), db::Trans ()));
+
+  c1.shapes (l1).insert (db::Box (db::Point (0, 0), db::Point (100, 200)));
+  c1.shapes (l1).insert (db::Box (db::Point (-100, -100), db::Point (0, 0)));
+
+  c2.shapes (l2).insert (db::Edge (db::Point (-10, -10), db::Point (0, 0)));
+  c2.shapes (l2).insert (db::Edge (db::Point (0, 0), db::Point (10, 10)));
+  c2.shapes (l2).insert (db::Edge (db::Point (-110, -10), db::Point (-90, 10)));
+  c2.shapes (l2).insert (db::Edge (db::Point (-110, -210), db::Point (-90, -190)));
+
+  ly.copy_layer (l2, l3);
+  top.shapes (l2).insert (db::Edge (db::Point (90, -10), db::Point (110, 10)));
+  top.shapes (l2).insert (db::Edge (db::Point (-110, -110), db::Point (-90, -90)));
+
+  db::Region r (db::RecursiveShapeIterator (ly, top, l1));
+  r.set_merged_semantics (true);
+  r.set_min_coherence (false);
+
+  db::Region empty;
+
+  db::Edges rr (db::RecursiveShapeIterator (ly, top, l2));
+  db::Edges rr2 (db::RecursiveShapeIterator (ly, top, l3));
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 5, 5).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 2, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 4, 5).to_string (), "");
+
+  EXPECT_EQ (r.selected_not_interacting (empty).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  //  Shortcut delivers clone of original, not merged one:
+  //    EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  //  so that is:
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 4, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 5, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 2, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+
+  r.set_merged_semantics (false);
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 1, 4), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 2, 4), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+
+  EXPECT_EQ (db::compare (r.selected_not_interacting (empty), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_not_interacting (rr, 2, 1), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "(0,0;0,200;100,200;100,0)");
+}
+
+TEST(30c_interact_with_count_text)
+{
+  db::Layout ly;
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));
+
+  db::Cell &top = ly.cell (ly.add_cell ("TOP"));
+  db::cell_index_type ci1 = ly.add_cell ("C1");
+  db::Cell &c1 = ly.cell (ci1);
+  db::cell_index_type ci2 = ly.add_cell ("C2");
+  db::Cell &c2 = ly.cell (ci2);
+  top.insert (db::CellInstArray (db::CellInst (ci1), db::Trans ()));
+  top.insert (db::CellInstArray (db::CellInst (ci2), db::Trans ()));
+
+  c1.shapes (l1).insert (db::Box (db::Point (0, 0), db::Point (100, 200)));
+  c1.shapes (l1).insert (db::Box (db::Point (-100, -100), db::Point (0, 0)));
+
+  c2.shapes (l2).insert (db::Text ("a", db::Trans (db::Vector (0, 0))));
+  c2.shapes (l2).insert (db::Text ("b", db::Trans (db::Vector (-100, 0))));
+  c2.shapes (l2).insert (db::Text ("c", db::Trans (db::Vector (-100, -200))));
+
+  ly.copy_layer (l2, l3);
+  top.shapes (l2).insert (db::Text ("x", db::Trans (db::Vector (100, 0))));
+  top.shapes (l2).insert (db::Text ("y", db::Trans (db::Vector (-100, -100))));
+
+  db::Region r (db::RecursiveShapeIterator (ly, top, l1));
+  r.set_merged_semantics (true);
+  r.set_min_coherence (false);
+
+  db::Region empty;
+
+  db::Texts rr (db::RecursiveShapeIterator (ly, top, l2));
+  db::Texts rr2 (db::RecursiveShapeIterator (ly, top, l3));
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr, 5, 5).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 1, 4).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 2, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_interacting (rr2, 4, 5).to_string (), "");
+
+  EXPECT_EQ (r.selected_not_interacting (empty).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  //  Shortcut delivers clone of original, not merged one:
+  //    EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  //  so that is:
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 1).to_string (), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 4, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 5, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 2).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 2, 5).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr2, 4, 5).to_string (), "(-100,-100;-100,0;0,0;0,200;100,200;100,0;0,0;0,-100)");
+
+  r.set_merged_semantics (false);
+
+  EXPECT_EQ (r.selected_interacting (empty).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 0, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (r.selected_interacting (rr, 1, 2).to_string (), "(0,0;0,200;100,200;100,0)");
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 1, 4), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (db::compare (r.selected_interacting (rr, 2, 4), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_interacting (rr, 2, 1).to_string (), "");
+  EXPECT_EQ (r.selected_interacting (rr, 3, 4).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+
+  EXPECT_EQ (db::compare (r.selected_not_interacting (empty), "(0,0;0,200;100,200;100,0);(-100,-100;-100,0;0,0;0,-100)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 0, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 2).to_string (), "(-100,-100;-100,0;0,0;0,-100)");
+  EXPECT_EQ (r.selected_not_interacting (rr, 1, 4).to_string (), "");
+  EXPECT_EQ (r.selected_not_interacting (rr, 2, 4).to_string (), "");
+  EXPECT_EQ (db::compare (r.selected_not_interacting (rr, 2, 1), "(-100,-100;-100,0;0,0;0,-100);(0,0;0,200;100,200;100,0)"), true);
+  EXPECT_EQ (r.selected_not_interacting (rr, 3, 4).to_string (), "(0,0;0,200;100,200;100,0)");
+}
+
+TEST(31_in)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l31.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));  //  empty
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+  db::Region r1r = r1;
+  r1r.set_merged_semantics (false);
+  db::Region r2r = r2;
+  r2r.set_merged_semantics (false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), r2);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2.in (r1));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.in (r1, true));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2.in (r3, false));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r2.in (r3, true));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r3.in (r1, false));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), r3.in (r1, true));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r2r.in (r1));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r2r.in (r1, true));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r2.in (r1r));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), r2.in (r1r, true));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (40, 0)), r2r.in (r1r));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (41, 0)), r2r.in (r1r, true));
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au31.gds");
+}
+
+TEST(31_in_and_out)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_l31.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));  //  empty
+
+  db::Region r1 (db::RecursiveShapeIterator (ly, top_cell, l1));
+  db::Region r2 (db::RecursiveShapeIterator (ly, top_cell, l2));
+  db::Region r3 (db::RecursiveShapeIterator (ly, top_cell, l3));
+
+  db::Region r1r = r1;
+  r1r.set_merged_semantics (false);
+  db::Region r2r = r2;
+  r2r.set_merged_semantics (false);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), r2);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r2.in_and_out (r1).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.in_and_out (r1).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r2.in_and_out (r3).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r2.in_and_out (r3).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (14, 0)), r3.in_and_out (r1).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (15, 0)), r3.in_and_out (r1).second);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r2r.in_and_out (r1).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r2r.in_and_out (r1).second);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r2.in_and_out (r1r).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), r2.in_and_out (r1r).second);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (40, 0)), r2r.in_and_out (r1r).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (41, 0)), r2r.in_and_out (r1r).second);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au31.gds");
+}
+
+TEST(40_BoolWithProperties)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_40.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+  unsigned int l3 = ly.get_layer (db::LayerProperties (3, 0));  //  empty
+
+  db::RecursiveShapeIterator si1 (ly, top_cell, l1);
+  si1.shape_flags (db::ShapeIterator::All | db::ShapeIterator::RegardProperties);
+  db::Region r1 (si1);
+
+  db::RecursiveShapeIterator si2 (ly, top_cell, l2);
+  si2.shape_flags (db::ShapeIterator::All | db::ShapeIterator::RegardProperties);
+  db::Region r2 (si2);
+
+  db::RecursiveShapeIterator si3 (ly, top_cell, l3);
+  si3.shape_flags (db::ShapeIterator::All | db::ShapeIterator::RegardProperties);
+  db::Region r3 (si3);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), r2);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1.merged ());
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.merged ());
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r1 & r2);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r1.bool_and (r2, db::NoPropertyConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r1.bool_and (r2, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (23, 0)), r1.bool_and (r2, db::DifferentPropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (24, 0)), r3.bool_and (r2, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (25, 0)), r3.bool_and (r2, db::DifferentPropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (26, 0)), r1.bool_and (r3, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (27, 0)), r1.bool_and (r3, db::DifferentPropertiesConstraint));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (30, 0)), r1 - r2);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (31, 0)), r1.bool_not (r2, db::NoPropertyConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (32, 0)), r1.bool_not (r2, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (33, 0)), r1.bool_not (r2, db::DifferentPropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (34, 0)), r3.bool_not (r2, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (35, 0)), r3.bool_not (r2, db::DifferentPropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (36, 0)), r1.bool_not (r3, db::SamePropertiesConstraint));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (37, 0)), r1.bool_not (r3, db::DifferentPropertiesConstraint));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (40, 0)), r1.andnot (r2).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (41, 0)), r1.andnot (r2).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (42, 0)), r1.andnot (r2, db::SamePropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (43, 0)), r1.andnot (r2, db::SamePropertiesConstraint).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (44, 0)), r1.andnot (r2, db::DifferentPropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (45, 0)), r1.andnot (r2, db::DifferentPropertiesConstraint).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (46, 0)), r3.andnot (r2, db::SamePropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (47, 0)), r3.andnot (r2, db::SamePropertiesConstraint).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (48, 0)), r3.andnot (r2, db::DifferentPropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (49, 0)), r3.andnot (r2, db::DifferentPropertiesConstraint).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (50, 0)), r1.andnot (r3, db::SamePropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (51, 0)), r1.andnot (r3, db::SamePropertiesConstraint).second);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (52, 0)), r1.andnot (r3, db::DifferentPropertiesConstraint).first);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (53, 0)), r1.andnot (r3, db::DifferentPropertiesConstraint).second);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/flat_region_au40.gds");
+}
+