From b9e439f41c1d3c8b5165378c36bf310f279115ee Mon Sep 17 00:00:00 2001
From: James Cherry <cherry@parallaxsw.com>
Date: Tue, 24 Mar 2026 18:42:47 -0700
Subject: [PATCH] delay calc clip delay to 0.0 resolves #405

Signed-off-by: James Cherry <cherry@parallaxsw.com>
---
 dcalc/DmpCeff.cc        | 14 +++++++-------
 dcalc/GraphDelayCalc.cc | 34 +++++++++++++++++-----------------
 liberty/TableModel.cc   |  4 +++-
 3 files changed, 27 insertions(+), 25 deletions(-)

diff --git a/dcalc/DmpCeff.cc b/dcalc/DmpCeff.cc
index 38c04648..1cccadaf 100644
--- a/dcalc/DmpCeff.cc
+++ b/dcalc/DmpCeff.cc
@@ -448,10 +448,10 @@ DmpAlg::showJacobian()
 {
   std::string line = "    ";
   for (int j = 0; j < nr_order_; j++)
-    line += sta::format("{:12}", dmp_param_index_strings[j]);
+    line += sta::format("{:>12}", dmp_param_index_strings[j]);
   report_->reportLine(line);
-  line.clear();
   for (int i = 0; i < nr_order_; i++) {
+    line.clear();
     line += sta::format("{:4} ", dmp_func_index_strings[i]);
     for (int j = 0; j < nr_order_; j++)
       line += sta::format("{:12.3e} ", fjac_[i][j]);
@@ -551,10 +551,10 @@ DmpAlg::loadDelaySlew(const Pin *,
     // Use the driver thresholds and rely on thresholdAdjust to
     // convert the delay and slew to the load's thresholds.
     try {
-      if (debug_->check("dmp_ceff", 4))
-        showVl();
       elmore_ = elmore;
       p3_ = 1.0 / elmore;
+      if (debug_->check("dmp_ceff", 4))
+        showVl();
       double t_lower = t0_;
       double t_upper = vlCrossingUpperBound();
       double load_delay = findVlCrossing(vth_, t_lower, t_upper);
@@ -1189,9 +1189,9 @@ DmpZeroC2::init(const LibertyLibrary *drvr_library,
 }
 
 void
-DmpZeroC2::gateDelaySlew(  // Return values.
-    double &delay,
-    double &slew)
+DmpZeroC2::gateDelaySlew(// Return values.
+                         double &delay,
+                         double &slew)
 {
   try {
     findDriverParams(c1_);
diff --git a/dcalc/GraphDelayCalc.cc b/dcalc/GraphDelayCalc.cc
index 8c12cdf1..9c95ed1b 100644
--- a/dcalc/GraphDelayCalc.cc
+++ b/dcalc/GraphDelayCalc.cc
@@ -411,27 +411,27 @@ GraphDelayCalc::seedDrvrSlew(Vertex *drvr_vertex,
     for (const MinMax *min_max : MinMax::range()) {
       for (const RiseFall *rf : RiseFall::range()) {
         InputDrive *drive = nullptr;
-  if (network_->isTopLevelPort(drvr_pin)) {
-    Port *port = network_->port(drvr_pin);
+        if (network_->isTopLevelPort(drvr_pin)) {
+          Port *port = network_->port(drvr_pin);
           drive = sdc->findInputDrive(port);
-  }
-      if (drive) {
-	const LibertyCell *drvr_cell;
-	const LibertyPort *from_port, *to_port;
-	float *from_slews;
+        }
+        if (drive) {
+          const LibertyCell *drvr_cell;
+          const LibertyPort *from_port, *to_port;
+          float *from_slews;
           drive->driveCell(rf, min_max, drvr_cell, from_port,
-			 from_slews, to_port);
-	if (drvr_cell) {
-	  if (from_port == nullptr)
-	    from_port = driveCellDefaultFromPort(drvr_cell, to_port);
-	  findInputDriverDelay(drvr_cell, drvr_pin, drvr_vertex, rf,
+                           from_slews, to_port);
+          if (drvr_cell) {
+            if (from_port == nullptr)
+              from_port = driveCellDefaultFromPort(drvr_cell, to_port);
+            findInputDriverDelay(drvr_cell, drvr_pin, drvr_vertex, rf,
                                  from_port, from_slews, to_port, scene, min_max);
-	}
-	else
+          }
+          else
             seedNoDrvrCellSlew(drvr_vertex, drvr_pin, rf, drive, scene, min_max,
-			     arc_delay_calc);
-      }
-      else
+                               arc_delay_calc);
+        }
+        else
           seedNoDrvrSlew(drvr_vertex, drvr_pin, rf, scene, min_max, arc_delay_calc);
       }
     }
diff --git a/liberty/TableModel.cc b/liberty/TableModel.cc
index 46dd6d6b..c3e8856f 100644
--- a/liberty/TableModel.cc
+++ b/liberty/TableModel.cc
@@ -116,7 +116,9 @@ GateTableModel::gateDelay(const Pvt *pvt,
     drvr_slew = findValue(pvt, slew_models_->model(), in_slew, load_cap, 0.0);
   else
     drvr_slew = 0.0;
-  // Clip negative slews to zero.
+  // Clip negative delays and slews to zero.
+  if (gate_delay < 0.0)
+    gate_delay = 0.0;
   if (drvr_slew < 0.0)
     drvr_slew = 0.0;
 }