diff --git a/app/Main.cc b/app/Main.cc
index fe3a8685..12735f63 100644
--- a/app/Main.cc
+++ b/app/Main.cc
@@ -31,6 +31,10 @@ extern "C" {
 extern int Sta_Init(Tcl_Interp *interp);
 }
 
+namespace sta {
+extern const char *tcl_inits[];
+}
+
 int
 main(int argc, char **argv)
 {
@@ -44,7 +48,7 @@ main(int argc, char **argv)
   }
   else {
     Sta *sta = new Sta;
-    staMain(sta, argc, argv, Sta_Init);
+    staMain(sta, argc, argv, Sta_Init, sta::tcl_inits);
     return 0;
   }
 }
diff --git a/app/StaMain.cc b/app/StaMain.cc
index 2366fc5e..47fdcbdb 100644
--- a/app/StaMain.cc
+++ b/app/StaMain.cc
@@ -29,10 +29,10 @@ typedef sta::Vector<SwigInitFunc> SwigInitFuncSeq;
 // "Arguments" passed to staTclAppInit.
 static int sta_argc;
 static char **sta_argv;
+static const char **sta_tcl_inits;
 static SwigInitFunc sta_swig_init;
 
 static const char *init_filename = "[file join $env(HOME) .sta]";
-extern const char *tcl_inits[];
 
 static void
 sourceTclFileEchoVerbose(const char *filename,
@@ -42,7 +42,8 @@ void
 staMain(Sta *sta,
 	int argc,
 	char **argv,
-	SwigInitFunc swig_init)
+	SwigInitFunc swig_init,
+	const char *tcl_inits[])
 {
   initSta();
 
@@ -55,7 +56,7 @@ staMain(Sta *sta,
   if (threads_exists)
     sta->setThreadCount(thread_count);
 
-  staSetupAppInit(argc, argv, swig_init);
+  staSetupAppInit(argc, argv, swig_init, tcl_inits);
   // Set argc to 1 so Tcl_Main doesn't source any files.
   // Tcl_Main never returns.
   Tcl_Main(1, argv, staTclAppInit);
@@ -86,10 +87,12 @@ parseThreadsArg(int argc,
 void
 staSetupAppInit(int argc,
 		char **argv,
-		SwigInitFunc swig_init)
+		SwigInitFunc swig_init,
+		const char *tcl_inits[])
 {
   sta_argc = argc;
   sta_argv = argv;
+  sta_tcl_inits = tcl_inits;
   sta_swig_init = swig_init;
 }
 
@@ -110,7 +113,7 @@ staTclAppInit(Tcl_Interp *interp)
   sta->setTclInterp(interp);
 
   // Eval encoded sta TCL sources.
-  evalTclInit(interp, tcl_inits);
+  evalTclInit(interp, sta_tcl_inits);
 
   if (!findCmdLineFlag(argc, argv, "-no_splash"))
     Tcl_Eval(interp, "sta::show_splash");
diff --git a/app/StaMain.hh b/app/StaMain.hh
index d553e2b4..ab265c27 100644
--- a/app/StaMain.hh
+++ b/app/StaMain.hh
@@ -21,6 +21,7 @@ struct Tcl_Interp;
 
 namespace sta {
 
+class Sta;
 typedef int (*SwigInitFunc)(Tcl_Interp *);
 
 // The swig_init function is called to define the swig interface
@@ -29,17 +30,16 @@ void
 staMain(Sta *sta,
 	int argc,
 	char **argv,
-	SwigInitFunc swig_init);
+	SwigInitFunc swig_init,
+	const char *tcl_inits[]);
 
 // Set arguments passed to staTclAppInit inside the tcl interpreter.
 void
 staSetupAppInit(int argc,
 		char **argv,
-		SwigInitFunc swig_init);
+		SwigInitFunc swig_init,
+		const char *tcl_inits[]);
 
-// The variable tcl_init is an implicit argument to this function that
-// provides the definitions for builtin tcl commands encoded by
-// etc/TclEncode.tcl.
 int
 staTclAppInit(Tcl_Interp *interp);
 
diff --git a/liberty/FuncExpr.cc b/liberty/FuncExpr.cc
index 76d7e368..d157a0ed 100644
--- a/liberty/FuncExpr.cc
+++ b/liberty/FuncExpr.cc
@@ -89,6 +89,14 @@ FuncExpr::deleteSubexprs()
   delete this;
 }
 
+FuncExpr *
+FuncExpr::copy()
+{
+  FuncExpr *left = left_ ? left_->copy() : nullptr;
+  FuncExpr *right = right_ ? right_->copy() : nullptr;
+  return new FuncExpr(op_, left, right, port_);
+}
+
 LibertyPort *
 FuncExpr::port() const
 {
diff --git a/liberty/FuncExpr.hh b/liberty/FuncExpr.hh
index a605910c..c22ef602 100644
--- a/liberty/FuncExpr.hh
+++ b/liberty/FuncExpr.hh
@@ -51,6 +51,8 @@ public:
   static bool less(const FuncExpr *expr1,
 		   const FuncExpr *expr2);
 
+  // Deep copy.
+  FuncExpr *copy();
   // Delete expression and all of its subexpressions.
   void deleteSubexprs();
   // op == op_port
diff --git a/network/ConcreteNetwork.cc b/network/ConcreteNetwork.cc
index e6c81ced..9586d2d1 100644
--- a/network/ConcreteNetwork.cc
+++ b/network/ConcreteNetwork.cc
@@ -276,7 +276,7 @@ void
 ConcreteNetwork::deleteTopInstance()
 {
   if (top_instance_) {
-    deleteInstance(reinterpret_cast<Instance*>(top_instance_));
+    deleteInstance(top_instance_);
     top_instance_ = nullptr;
   }
 }
@@ -296,7 +296,7 @@ ConcreteNetwork::deleteCellNetworkViews()
 Instance *
 ConcreteNetwork::topInstance() const
 {
-  return reinterpret_cast<Instance*>(top_instance_);
+  return top_instance_;
 }
 
 ////////////////////////////////////////////////////////////////
@@ -404,9 +404,10 @@ ConcreteNetwork::libertyLibraryIterator() const
 ////////////////////////////////////////////////////////////////
 
 Library *
-ConcreteNetwork::makeLibrary(const char *name)
+ConcreteNetwork::makeLibrary(const char *name,
+			     const char *filename)
 {
-  ConcreteLibrary *library = new ConcreteLibrary(name, nullptr);
+  ConcreteLibrary *library = new ConcreteLibrary(name, filename);
   addLibrary(library);
   return reinterpret_cast<Library*>(library);
 }
@@ -1120,7 +1121,7 @@ ConcreteNetwork::makeConcreteInstance(ConcreteCell *cell,
 {
   ConcreteInstance *cparent =
     reinterpret_cast<ConcreteInstance*>(parent);
-  ConcreteInstance *inst = new ConcreteInstance(name, cell, cparent);
+  ConcreteInstance *inst = new ConcreteInstance(cell, name, cparent);
   if (parent)
     cparent->addChild(inst);
   return reinterpret_cast<Instance*>(inst);
@@ -1257,7 +1258,7 @@ ConcreteNetwork::connect(Instance *inst,
     cpin = new ConcretePin(cinst, cport, cnet);
     cinst->addPin(cpin);
   }
-  if (cinst == top_instance_) {
+  if (inst == top_instance_) {
     // makeTerm
     ConcreteTerm *cterm = new ConcreteTerm(cpin, cnet);
     cnet->addTerm(cterm);
@@ -1296,7 +1297,7 @@ void
 ConcreteNetwork::disconnectPin(Pin *pin)
 {
   ConcretePin *cpin = reinterpret_cast<ConcretePin*>(pin);
-  if (cpin->instance() == top_instance_) {
+  if (reinterpret_cast<Instance*>(cpin->instance()) == top_instance_) {
     ConcreteTerm *cterm = cpin->term_;
     if (cterm) {
       ConcreteNet *cnet = cterm->net_;
@@ -1450,19 +1451,26 @@ ConcreteNetwork::visitConnectedPins(const Net *net,
 
 ////////////////////////////////////////////////////////////////
 
-ConcreteInstance::ConcreteInstance(const char *name,
-				   ConcreteCell *cell,
+ConcreteInstance::ConcreteInstance(ConcreteCell *cell,
+				   const char *name,
 				   ConcreteInstance *parent) :
-  name_(stringCopy(name)),
   cell_(cell),
+  name_(stringCopy(name)),
   parent_(parent),
   children_(nullptr),
   nets_(nullptr)
 {
-  int pin_count = reinterpret_cast<ConcreteCell*>(cell)->portBitCount();
-  pins_ = new ConcretePin*[pin_count];
-  for (int i = 0; i < pin_count; i++)
-    pins_[i] = nullptr;
+  initPins();
+}
+
+void
+ConcreteInstance::initPins()
+{
+  int pin_count = reinterpret_cast<ConcreteCell*>(cell_)->portBitCount();
+  if (pin_count)
+    pins_ = new ConcretePin*[pin_count]{nullptr};
+  else
+    pins_ = nullptr;
 }
 
 ConcreteInstance::~ConcreteInstance()
@@ -1789,10 +1797,10 @@ ConcreteNetwork::readNetlistBefore()
 }
 
 void
-ConcreteNetwork::setTopInstance(ConcreteInstance *top_inst)
+ConcreteNetwork::setTopInstance(Instance *top_inst)
 {
   if (top_instance_) {
-    deleteInstance(reinterpret_cast<Instance*>(top_instance_));
+    deleteInstance(top_instance_);
     clearConstantNets();
     clearNetDrvPinrMap();
   }
@@ -1815,10 +1823,7 @@ ConcreteNetwork::linkNetwork(const char *top_cell_name,
     deleteTopInstance();
     Cell *top_cell = findAnyCell(top_cell_name);
     if (top_cell) {
-      top_instance_ =
-	reinterpret_cast<ConcreteInstance*>(link_func_(top_cell,
-						       make_black_boxes,
-						       report, this));
+      top_instance_ = link_func_(top_cell, make_black_boxes, report, this);
       return top_instance_ != nullptr;
     }
     else {
diff --git a/network/ConcreteNetwork.hh b/network/ConcreteNetwork.hh
index 4eeb88fe..5b1109e3 100644
--- a/network/ConcreteNetwork.hh
+++ b/network/ConcreteNetwork.hh
@@ -155,7 +155,8 @@ public:
 		      LogicValue value);
 
   // Edit methods.
-  virtual Library *makeLibrary(const char *name);
+  virtual Library *makeLibrary(const char *name,
+			       const char *filename);
   virtual LibertyLibrary *makeLibertyLibrary(const char *name,
 					     const char *filename);
   virtual Cell *makeCell(Library *library,
@@ -221,7 +222,7 @@ public:
 
   virtual void readNetlistBefore();
   virtual void setLinkFunc(LinkNetworkFunc *link);
-  void setTopInstance(ConcreteInstance *top_inst);
+  void setTopInstance(Instance *top_inst);
 
   using Network::netIterator;
   using Network::findPin;
@@ -250,7 +251,7 @@ protected:
   // Cell lookup search order sequence.
   ConcreteLibrarySeq library_seq_;
   ConcreteLibraryMap library_map_;
-  ConcreteInstance *top_instance_;
+  Instance *top_instance_;
   NetSet constant_nets_[2];  // LogicValue::zero/one
   LinkNetworkFunc *link_func_;
   CellNetworkViewMap cell_network_view_map_;
@@ -284,15 +285,16 @@ public:
 	      ConcreteNet *net);
   void deleteNet(ConcreteNet *net);
   void setCell(LibertyCell *cell);
+  void initPins();
 
-private:
-  ConcreteInstance(const char *name,
-		   ConcreteCell *cell,
+protected:
+  ConcreteInstance(ConcreteCell *cell,
+		   const char *name,
 		   ConcreteInstance *parent);
   ~ConcreteInstance();
 
-  const char *name_;
   ConcreteCell *cell_;
+  const char *name_;
   ConcreteInstance *parent_;
   // Array of pins indexed by pin->port->index().
   ConcretePin **pins_;
@@ -373,12 +375,13 @@ public:
   void mergeInto(ConcreteNet *net);
   ConcreteNet *mergedInto() { return merged_into_; }
 
-private:
+protected:
   DISALLOW_COPY_AND_ASSIGN(ConcreteNet);
   ConcreteNet(const char *name,
 	      ConcreteInstance *instance);
   virtual ~ConcreteNet();
 
+private:
   const char *name_;
   ConcreteInstance *instance_;
   // Pointer to head of linked list of pins.
diff --git a/network/Network.hh b/network/Network.hh
index a974d1c7..d064dc5f 100644
--- a/network/Network.hh
+++ b/network/Network.hh
@@ -520,7 +520,8 @@ public:
   // Called before reading a netlist to delete any previously linked network.
   virtual void readNetlistBefore() = 0;
   virtual void setLinkFunc(LinkNetworkFunc *link) = 0;
-  virtual Library *makeLibrary(const char *name) = 0;
+  virtual Library *makeLibrary(const char *name,
+			       const char *filename) = 0;
   // Search the libraries in read order for a cell by name.
   virtual Cell *findAnyCell(const char *name) = 0;
   virtual Cell *makeCell(Library *library,
diff --git a/search/Power.cc b/search/Power.cc
index eec79f9f..44ca0cc9 100644
--- a/search/Power.cc
+++ b/search/Power.cc
@@ -405,6 +405,7 @@ Power::ensureActivities()
 	  // Propagate activiities across register D->Q.
 	  seedRegOutputActivities(reg, bfs);
 	}
+	delete regs;
 	visitor.init();
 	bfs.visit(levelize_->maxLevel(), &visitor);
       }
@@ -546,7 +547,6 @@ Power::findInternalPower(const Pin *to_pin,
   debugPrint1(debug_, "power", 2, " cap = %s\n",
 	      units_->capacitanceUnit()->asString(load_cap));
   debugPrint0(debug_, "power", 2, "       when act/ns duty  energy    power\n");
-  float input_duty_sum = inputDutySum(inst);
   float internal = 0.0;
   LibertyCellInternalPowerIterator pwr_iter(cell);
   while (pwr_iter.hasNext()) {
@@ -554,26 +554,35 @@ Power::findInternalPower(const Pin *to_pin,
     if (pwr->port() == to_port) {
       const char *related_pg_pin = pwr->relatedPgPin();
       const LibertyPort *from_port = pwr->relatedPort();
-      if (from_port == nullptr)
-	// Input port internal power.
-	from_port = to_port;
       FuncExpr *when = pwr->when();
+      FuncExpr *infered_when = nullptr;
+      if (from_port) {
+	if (when == nullptr) {
+	  FuncExpr *func = to_port->function();
+	  if (func)
+	    infered_when = inferedWhen(func, from_port);
+	}
+      }
+      else
+	from_port = to_port;
       // If all the "when" clauses exist VSS internal power is ignored.
       if ((when && internalPowerMissingWhen(cell, to_port, related_pg_pin))
 	  || pgNameVoltage(cell, related_pg_pin, dcalc_ap) != 0.0) {
 	const Pin *from_pin = network_->findPin(inst, from_port);
 	Vertex *from_vertex = graph_->pinLoadVertex(from_pin);
 	float duty;
-	if (when)
+	if (infered_when) {
+	  PwrActivity from_activity = findActivity(from_pin);
+	  PwrActivity to_activity = findActivity(to_pin);
+	  float duty1 = evalActivity(infered_when, inst).duty();
+	  duty = from_activity.activity() / to_activity.activity() * duty1;
+	}
+	else if (when)
 	  duty = evalActivity(when, inst).duty();
 	else if (search_->isClock(from_vertex))
 	  duty = 1.0;
-	else {
-	  PwrActivity from_activity = findActivity(from_pin);
-	  PwrActivity to_activity = findActivity(to_pin);
-	  float duty1 = input_duty_sum - from_activity.duty();
-	  duty = from_activity.activity() * (1.0 - duty1) / to_activity.activity();
-	}
+	else
+	  duty = 0.5;
 	float port_energy = 0.0;
 	TransRiseFallIterator tr_iter;
 	while (tr_iter.hasNext()) {
@@ -596,7 +605,7 @@ Power::findInternalPower(const Pin *to_pin,
 	debugPrint8(debug_, "power", 2,  " %s -> %s %s  %.2f %.2f %9.2e %9.2e %s\n",
 		    from_port->name(),
 		    to_port->name(),
-		    pwr->when() ? pwr->when()->asString() : "    ",
+		    when ? when->asString() : (infered_when ? infered_when->asString() : "    "),
 		    to_activity.activity() * 1e-9,
 		    duty,
 		    port_energy,
@@ -604,11 +613,69 @@ Power::findInternalPower(const Pin *to_pin,
 		    related_pg_pin ? related_pg_pin : "no pg_pin");
 	internal += port_internal;
       }
+      if (infered_when)
+	infered_when->deleteSubexprs();
     }
   }
   result.setInternal(result.internal() + internal);
 }
 
+////////////////////////////////////////////////////////////////
+
+static bool
+isPortRef(FuncExpr *expr,
+	  const LibertyPort *port)
+{
+  return (expr->op() == FuncExpr::op_port
+	  && expr->port() == port)
+    || (expr->op() == FuncExpr::op_not
+	&& expr->left()->op() == FuncExpr::op_port
+	&& expr->left()->port() == port);
+}
+
+static FuncExpr *
+negate(FuncExpr *expr)
+{
+  if (expr->op() == FuncExpr::op_not)
+    return expr->left()->copy();
+  else
+    return FuncExpr::makeNot(expr->copy());
+}
+
+FuncExpr *
+Power::inferedWhen(FuncExpr *expr,
+		   const LibertyPort *from_port)
+{
+  switch (expr->op()) {
+  case FuncExpr::op_port: {
+    if (expr->port() == from_port)
+      return FuncExpr::makeOne();
+    else
+      return nullptr;
+  }
+  case FuncExpr::op_not:
+    return inferedWhen(expr->left(), from_port);
+  case FuncExpr::op_or:
+  case FuncExpr::op_xor: {
+    if (isPortRef(expr->left(), from_port))
+      return negate(expr->right());
+    if (isPortRef(expr->right(), from_port))
+      return negate(expr->left());
+  }
+  case FuncExpr::op_and: {
+    if (isPortRef(expr->left(), from_port))
+      return expr->right()->copy();
+    if (isPortRef(expr->right(), from_port))
+      return expr->left()->copy();
+  }
+  case FuncExpr::op_one:
+  case FuncExpr::op_zero:
+   return nullptr;
+  }
+}
+
+////////////////////////////////////////////////////////////////
+
 // Return true if some a "when" clause for the internal power to_port
 // is missing.
 bool
@@ -645,20 +712,6 @@ funcExprPortCount(FuncExpr *expr)
   return port_count;
 }
 
-float
-Power::inputDutySum(const Instance *inst)
-{
-  float duty_sum = 0.0;
-  InstancePinIterator *pin_iter = network_->pinIterator(inst);
-  while (pin_iter->hasNext()) {
-    const Pin *pin = pin_iter->next();
-    if (network_->direction(pin)->isAnyInput())
-      duty_sum += findClkedActivity(pin).duty();
-  }
-  delete pin_iter;
-  return duty_sum;
-}
-
 void
 Power::findLeakagePower(const Instance *,
 			LibertyCell *cell,
diff --git a/search/Power.hh b/search/Power.hh
index 8321ceb5..bbb47b9e 100644
--- a/search/Power.hh
+++ b/search/Power.hh
@@ -147,10 +147,11 @@ protected:
 			       BfsFwdIterator &bfs);
   PwrActivity evalActivity(FuncExpr *expr,
 			   const Instance *inst);
-  float inputDutySum(const Instance *inst);
   bool internalPowerMissingWhen(LibertyCell *cell,
 				const LibertyPort *to_port,
 				const char *related_pg_pin);
+  FuncExpr *inferedWhen(FuncExpr *expr,
+			const LibertyPort *from_port);
 
 private:
   PwrActivity global_activity_;
diff --git a/tcl/StaTcl.i b/tcl/StaTcl.i
index dabd06ad..42ad15f7 100644
--- a/tcl/StaTcl.i
+++ b/tcl/StaTcl.i
@@ -2652,7 +2652,6 @@ PropertyValue
 pin_property(const Pin *pin,
 	     const char *property)
 {
-  cmdGraph();
   return getProperty(pin, property, Sta::sta());
 }
 
@@ -2660,7 +2659,6 @@ PropertyValue
 instance_property(const Instance *inst,
 		  const char *property)
 {
-  cmdGraph();
   return getProperty(inst, property, Sta::sta());
 }
 
@@ -2668,7 +2666,6 @@ PropertyValue
 net_property(const Net *net,
 	     const char *property)
 {
-  cmdGraph();
   return getProperty(net, property, Sta::sta());
 }
 
@@ -2676,7 +2673,6 @@ PropertyValue
 port_property(const Port *port,
 	      const char *property)
 {
-  cmdGraph();
   return getProperty(port, property, Sta::sta());
 }
 
diff --git a/verilog/Verilog.tcl b/verilog/Verilog.tcl
index 6984c050..af9da635 100644
--- a/verilog/Verilog.tcl
+++ b/verilog/Verilog.tcl
@@ -14,8 +14,6 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-# Network commands.
-
 namespace eval sta {
 
 # Defined by SWIG interface Verilog.i.
diff --git a/verilog/VerilogReader.cc b/verilog/VerilogReader.cc
index 3753bf97..95415898 100644
--- a/verilog/VerilogReader.cc
+++ b/verilog/VerilogReader.cc
@@ -204,7 +204,7 @@ VerilogReader::init(const char *filename)
 
   library_ = network_->findLibrary("verilog");
   if (library_ == nullptr)
-    library_ = network_->makeLibrary("verilog");
+    library_ = network_->makeLibrary("verilog", nullptr);
 
   report_stmt_stats_ = debugCheck(debug_, "verilog", 1);
   module_count_ = 0;