diff --git a/src/db/db/dbHierProcessor.cc b/src/db/db/dbHierProcessor.cc
index f13935fd9..a6af1f211 100644
--- a/src/db/db/dbHierProcessor.cc
+++ b/src/db/db/dbHierProcessor.cc
@@ -714,7 +714,6 @@ local_processor_result_computation_task<TS, TI, TR>::perform ()
 {
   mp_cell_contexts->compute_results (*mp_contexts, mp_cell, mp_op, m_output_layers, mp_proc);
 
-  //  erase the contexts we don't need any longer
   {
     tl::MutexLocker locker (& mp_contexts->lock ());
 
@@ -734,7 +733,10 @@ local_processor_result_computation_task<TS, TI, TR>::perform ()
     }
 #endif
 
-    mp_contexts->context_map ().erase (mp_cell);
+    //  release some memory
+    auto ctx = mp_contexts->context_map ().find (mp_cell);
+    tl_assert (ctx != mp_contexts->context_map ().end ());
+    ctx->second.cleanup ();
   }
 }
 
@@ -881,15 +883,6 @@ void local_processor<TS, TI, TR>::run (local_operation<TS, TI, TR> *op, unsigned
   compute_results (contexts, op, output_layers);
 }
 
-template <class TS, class TI, class TR>
-void local_processor<TS, TI, TR>::push_results (db::Cell *cell, unsigned int output_layer, const std::unordered_set<TR> &result) const
-{
-  if (! result.empty ()) {
-    tl::MutexLocker locker (&cell->layout ()->lock ());
-    cell->shapes (output_layer).insert (result.begin (), result.end ());
-  }
-}
-
 template <class TS, class TI, class TR>
 void local_processor<TS, TI, TR>::compute_contexts (local_processor_contexts<TS, TI, TR> &contexts, const local_operation<TS, TI, TR> *op, unsigned int subject_layer, const std::vector<unsigned int> &intruder_layers) const
 {
@@ -1248,7 +1241,7 @@ local_processor<TS, TI, TR>::compute_results (local_processor_contexts<TS, TI, T
         typename local_processor_contexts<TS, TI, TR>::iterator cpc = contexts.context_map ().find (&mp_subject_layout->cell (*bu));
         if (cpc != contexts.context_map ().end ()) {
           cpc->second.compute_results (contexts, cpc->first, op, output_layers, this);
-          contexts.context_map ().erase (cpc);
+          cpc->second.cleanup ();   //  release some memory
         }
 
       }
@@ -1261,6 +1254,24 @@ local_processor<TS, TI, TR>::compute_results (local_processor_contexts<TS, TI, T
     }
 
   }
+
+  //  deliver the results
+  {
+    tl::MutexLocker locker (& mp_subject_layout->lock ());
+    for (auto c = contexts.begin (); c != contexts.end (); ++c) {
+
+      db::Cell *cell = c->first;
+      auto r = c->second.result ().begin ();
+      auto rend = c->second.result ().end ();
+
+      for (auto o = output_layers.begin (); r != rend && o != output_layers.end (); ++o, ++r) {
+        if (! r->empty ()) {
+          cell->shapes (*o).insert (r->begin (), r->end ());
+        }
+      }
+
+    }
+  }
 }
 
 namespace {
diff --git a/src/db/db/dbHierProcessor.h b/src/db/db/dbHierProcessor.h
index 44705178f..c52dd372e 100644
--- a/src/db/db/dbHierProcessor.h
+++ b/src/db/db/dbHierProcessor.h
@@ -244,9 +244,20 @@ public:
     return m_contexts.end ();
   }
 
+  const std::vector<std::unordered_set<TR> > &result () const
+  {
+    return m_result;
+  }
+
+  void cleanup ()
+  {
+    m_contexts.clear ();
+  }
+
 private:
   const db::Cell *mp_intruder_cell;
   std::unordered_map<context_key_type, db::local_processor_cell_context<TS, TI, TR> > m_contexts;
+  std::vector<std::unordered_set<TR> > m_result;
 };
 
 template <class TS, class TI, class TR>
@@ -558,7 +569,6 @@ private:
   size_t get_progress () const;
   void compute_contexts (db::local_processor_contexts<TS, TI, TR> &contexts, db::local_processor_cell_context<TS, TI, TR> *parent_context, db::Cell *subject_parent, db::Cell *subject_cell, const db::ICplxTrans &subject_cell_inst, const db::Cell *intruder_cell, const typename local_processor_cell_contexts<TS, TI, TR>::context_key_type &intruders, db::Coord dist) const;
   void issue_compute_contexts (db::local_processor_contexts<TS, TI, TR> &contexts, db::local_processor_cell_context<TS, TI, TR> *parent_context, db::Cell *subject_parent, db::Cell *subject_cell, const db::ICplxTrans &subject_cell_inst, const db::Cell *intruder_cell, typename local_processor_cell_contexts<TS, TI, TR>::context_key_type &intruders, db::Coord dist) const;
-  void push_results (db::Cell *cell, unsigned int output_layer, const std::unordered_set<TR> &result) const;
   void compute_local_cell (const db::local_processor_contexts<TS, TI, TR> &contexts, db::Cell *subject_cell, const db::Cell *intruder_cell, const local_operation<TS, TI, TR> *op, const typename local_processor_cell_contexts<TS, TI, TR>::context_key_type &intruders, std::vector<std::unordered_set<TR> > &result) const;
 
   bool subject_cell_is_breakout (db::cell_index_type ci) const
diff --git a/src/db/db/dbHierProcessor2.cc b/src/db/db/dbHierProcessor2.cc
index a7909bb9b..5f7be3cc0 100644
--- a/src/db/db/dbHierProcessor2.cc
+++ b/src/db/db/dbHierProcessor2.cc
@@ -446,7 +446,12 @@ local_processor_cell_contexts<TS, TI, TR>::compute_results (const local_processo
         proc->compute_local_cell (contexts, cell, mp_intruder_cell, op, *c->first, res);
       }
 
-      if (common.empty ()) {
+      bool common_empty = true;
+      for (auto c = common.begin (); common_empty && c != common.end (); ++c) {
+        common_empty = c->empty ();
+      }
+
+      if (common_empty) {
 
         CRONOLOGY_COMPUTE_BRACKET(event_propagate)
         for (std::vector<unsigned int>::const_iterator o = output_layers.begin (); o != output_layers.end (); ++o) {
@@ -519,9 +524,30 @@ local_processor_cell_contexts<TS, TI, TR>::compute_results (const local_processo
 
   }
 
-  for (std::vector<unsigned int>::const_iterator o = output_layers.begin (); o != output_layers.end (); ++o) {
-    size_t oi = o - output_layers.begin ();
-    proc->push_results (cell, *o, common[oi]);
+  //  store the results
+
+  bool common_empty = true;
+  for (auto c = common.begin (); common_empty && c != common.end (); ++c) {
+    common_empty = c->empty ();
+  }
+
+  if (! common_empty) {
+    if (m_result.empty ()) {
+      m_result.swap (common);
+    } else {
+      if (m_result.size () < common.size ()) {
+        m_result.resize (common.size ());
+      }
+      auto t = m_result.begin ();
+      for (auto s = common.begin (); s != common.end (); ++s, ++t) {
+        if (t->empty ()) {
+          t->swap (*s);
+        } else {
+          t->insert (s->begin (), s->end ());
+          s->clear ();
+        }
+      }
+    }
   }
 }