Implemented fix for issue #1832 (enhancements for Netlist#simplify and Netlist#combine_devices)

src/db/db/dbCircuit.cc

@@ -825,6 +825,41 @@ void Circuit::do_purge_nets (bool keep_pins)
   }
 }
 
+static bool can_purge_device (const db::Device &device)
+{
+  if (! device.device_class ()) {
+    return false;
+  }
+
+  const std::vector<db::DeviceTerminalDefinition> &tdefs = device.device_class ()->terminal_definitions ();
+  if (tdefs.size () <= 1) {
+    return false;
+  }
+
+  const db::Net *net = device.net_for_terminal (tdefs.front ().id ());
+  for (auto t = tdefs.begin () + 1; t != tdefs.end (); ++t) {
+    if (net != device.net_for_terminal (t->id ())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void Circuit::purge_devices ()
+{
+  std::vector<db::Device *> devices_to_be_purged;
+  for (device_iterator d = begin_devices (); d != end_devices (); ++d) {
+    if (can_purge_device (*d)) {
+      devices_to_be_purged.push_back (d.operator-> ());
+    }
+  }
+
+  for (auto d = devices_to_be_purged.begin (); d != devices_to_be_purged.end (); ++d) {
+    remove_device (*d);
+  }
+}
+
 /**
  *  @brief Sanity check for device to be removed
  */

src/db/db/dbCircuit.h

@@ -732,6 +732,14 @@ public:
    */
   void purge_nets_keep_pins ();
 
+  /**
+   *  @brief Purges invalid devices
+   *
+   *  This method will purge all invalid devices, i.e. those
+   *  whose terminals are all connected to the same net.
+   */
+  void purge_devices ();
+
   /**
    *  @brief Combine devices
    *

src/db/db/dbNetlist.cc

@@ -619,6 +619,13 @@ void Netlist::purge_nets ()
   }
 }
 
+void Netlist::purge_devices ()
+{
+  for (bottom_up_circuit_iterator c = begin_bottom_up (); c != end_bottom_up (); ++c) {
+    c->purge_devices ();
+  }
+}
+
 void Netlist::make_top_level_pins ()
 {
   size_t ntop = top_circuit_count ();
@@ -651,6 +658,9 @@ void Netlist::purge ()
 
     Circuit *circuit = c.operator-> ();
 
+    //  purge invalid devices
+    circuit->purge_devices ();
+
     //  purge floating, disconnected nets
     circuit->purge_nets ();
 
@@ -684,6 +694,8 @@ void Netlist::simplify ()
 {
   make_top_level_pins ();
   purge ();
+
+  //  combine devices are purge nets that are created in that step
   combine_devices ();
   purge_nets ();
 }

src/db/db/dbNetlist.h

@@ -508,6 +508,14 @@ public:
    */
   void purge_nets ();
 
+  /**
+   *  @brief Purges invalid devices
+   *
+   *  This method will purge all invalid devices, i.e. those
+   *  whose terminals are all connected to the same net.
+   */
+  void purge_devices ();
+
   /**
    *  @brief Creates pins for top-level circuits
    *

src/db/db/gsiDeclDbNetlist.cc

@@ -1809,6 +1809,12 @@ Class<db::Circuit> decl_dbCircuit (decl_dbNetlistObject, "db", "Circuit",
     "For example, serial or parallel resistors can be combined into "
     "a single resistor.\n"
   ) +
+  gsi::method ("purge_devices", &db::Circuit::purge_devices,
+    "@brief Purges invalid devices.\n"
+    "Purges devices which are considered invalid. Such devices are for example those whose terminals are all connected to a single net.\n"
+    "\n"
+    "This method has been added in version 0.29.7."
+  ) +
   gsi::method ("purge_nets", &db::Circuit::purge_nets,
     "@brief Purges floating nets.\n"
     "Floating nets are nets with no device or subcircuit attached to. Such floating "
@@ -2176,9 +2182,15 @@ Class<db::Netlist> decl_dbNetlist ("db", "Netlist",
     "Floating nets can be created as effect of reconnections of devices or pins. "
     "This method will eliminate all nets that make less than two connections."
   ) +
+  gsi::method ("purge_devices", &db::Netlist::purge_devices,
+    "@brief Purges invalid devices.\n"
+    "Purges devices which are considered invalid. Such devices are for example those whose terminals are all connected to a single net.\n"
+    "\n"
+    "This method has been added in version 0.29.7."
+  ) +
   gsi::method ("simplify", &db::Netlist::simplify,
     "@brief Convenience method that combines the simplification.\n"
-    "This method is a convenience method that runs \\make_top_level_pins, \\purge, \\combine_devices and \\purge_nets."
+    "This method is a convenience method that runs \\make_top_level_pins, \\purge, \\combine_devices, \\purge_devices and \\purge_nets."
   ) +
   gsi::method_ext ("read", &read_netlist, gsi::arg ("file"), gsi::arg ("reader"),
     "@brief Writes the netlist to the given file using the given reader object to parse the file\n"

src/db/unit_tests/dbNetlistTests.cc

@@ -1988,3 +1988,57 @@ TEST(27_CombineSmallL)
     "end;\n"
   );
 }
+
+TEST(28_EliminateShortedDevices)
+{
+  db::Netlist nl;
+
+  db::Circuit *circuit = new db::Circuit ();
+  circuit->set_name ("TOP");
+  nl.add_circuit (circuit);
+
+  db::DeviceClass *device = new db::DeviceClassCapacitor ();
+  device->set_name ("model_name");
+  nl.add_device_class (device);
+
+  db::Net *n1 = new db::Net ("n1");
+  circuit->add_net (n1);
+
+  db::Net *n2 = new db::Net ("n2");
+  circuit->add_net (n2);
+
+  auto p1 = circuit->add_pin ("p1");
+  auto p2 = circuit->add_pin ("p2");
+
+  circuit->connect_pin (p1.id (), n1);
+  circuit->connect_pin (p2.id (), n2);
+
+  db::Device *c1 = new db::Device (device, "c1");
+  circuit->add_device (c1);
+  c1->set_parameter_value (db::DeviceClassInductor::param_id_L, 1e-15);
+
+  db::Device *c2 = new db::Device (device, "c2");
+  circuit->add_device (c2);
+  c2->set_parameter_value (db::DeviceClassInductor::param_id_L, 2e-15);
+
+  c1->connect_terminal (db::DeviceClassInductor::terminal_id_A, n1);
+  c1->connect_terminal (db::DeviceClassInductor::terminal_id_B, n1);
+
+  c2->connect_terminal (db::DeviceClassInductor::terminal_id_A, n1);
+  c2->connect_terminal (db::DeviceClassInductor::terminal_id_B, n2);
+
+  EXPECT_EQ (nl.to_string (),
+    "circuit TOP (p1=n1,p2=n2);\n"
+    "  device model_name c1 (A=n1,B=n1) (C=1e-15,A=0,P=0);\n"
+    "  device model_name c2 (A=n1,B=n2) (C=2e-15,A=0,P=0);\n"
+    "end;\n"
+  );
+
+  nl.simplify ();
+
+  EXPECT_EQ (nl.to_string (),
+    "circuit TOP (p1=n1,p2=n2);\n"
+    "  device model_name c2 (A=n1,B=n2) (C=2e-15,A=0,P=0);\n"
+    "end;\n"
+  );
+}