Merge pull request #6639 from The-OpenROAD-Project-staging/gpl-avoid-…

…td-during-rd

gpl: avoid timing-driven during routability

src/gpl/src/nesterovBase.cpp

@@ -2681,7 +2681,7 @@ bool NesterovBase::checkDivergence()
   return isDiverged_;
 }
 
-bool NesterovBase::revertDivergence()
+bool NesterovBase::revertToSnapshot()
 {
   if (isConverged_) {
     return true;

src/gpl/src/nesterovBase.h

@@ -773,15 +773,15 @@ class NesterovPlaceVars
   float minPreconditioner = 1.0;            // MIN_PRE
   float initialPrevCoordiUpdateCoef = 100;  // z_ref_alpha
   float referenceHpwl = 446000000;          // refDeltaHpwl
-  float routabilityCheckOverflow = 0.30;
+  float routability_end_overflow = 0.30;
   float keepResizeBelowOverflow = 0.3;
 
   static const int maxRecursionWlCoef = 10;
   static const int maxRecursionInitSLPCoef = 10;
 
   bool timingDrivenMode = true;
   int timingDrivenIterCounter = 0;
-  bool routabilityDrivenMode = true;
+  bool routability_driven_mode = true;
   bool disableRevertIfDiverge = false;
 
   bool debug = false;
@@ -1067,7 +1067,7 @@ class NesterovBase
 
   bool checkConvergence();
   bool checkDivergence();
-  bool revertDivergence();
+  bool revertToSnapshot();
 
   void updateDensityCenterCur();
   void updateDensityCenterCurSLP();

src/gpl/src/nesterovPlace.cpp

@@ -296,7 +296,7 @@ void NesterovPlace::reset()
   wireLengthCoefX_ = wireLengthCoefY_ = 0;
   prevHpwl_ = 0;
   isDiverged_ = false;
-  isRoutabilityNeed_ = true;
+  is_routability_need_ = true;
 
   divergeMsg_ = "";
   divergeCode_ = 0;
@@ -322,9 +322,10 @@ int NesterovPlace::doNesterovPlace(int start_iter)
   bool is_routability_snapshot_saved = false;
   float route_snapshotA = 0;
   float route_snapshot_WlCoefX = 0, route_snapshot_WlCoefY = 0;
-  bool isDivergeTriedRevert = false;
+  // bool isDivergeTriedRevert = false;
 
   // divergence snapshot info
+  bool is_diverge_snapshot_saved = false;
   float diverge_snapshot_WlCoefX = 0, diverge_snapshot_WlCoefY = 0;
 
   // backTracking variable.
@@ -419,6 +420,7 @@ int NesterovPlace::doNesterovPlace(int start_iter)
         for (auto& nb : nbVec_) {
           nb->snapshot();
         }
+        is_diverge_snapshot_saved = true;
       }
     }
 
@@ -438,8 +440,16 @@ int NesterovPlace::doNesterovPlace(int start_iter)
     // timing driven feature
     // if virtual, do reweight on timing-critical nets,
     // otherwise keep all modifications by rsz.
+    const bool is_before_routability
+        = average_overflow_ > routability_save_snapshot_;
+    const bool is_after_routability
+        = (average_overflow_ < npVars_.routability_end_overflow
+           && !is_routability_need_);
     if (npVars_.timingDrivenMode
-        && tb_->isTimingNetWeightOverflow(average_overflow_)) {
+        && tb_->isTimingNetWeightOverflow(average_overflow_) &&
+        // do not execute timing-driven if routability is under execution
+        (is_before_routability || is_after_routability
+         || !npVars_.routability_driven_mode)) {
       // update db's instance location from current density coordinates
       updateDb();
 
@@ -530,31 +540,37 @@ int NesterovPlace::doNesterovPlace(int start_iter)
     }
 
     if (numDiverge > 0) {
-      divergeMsg_ = "RePlAce divergence detected. ";
-      divergeMsg_ += "Re-run with a smaller max_phi_cof value.";
-      divergeCode_ = 307;
-      isDiverged_ = true;
-
-      // revert back to the original rb solutions
-      // one more opportunity
-      if (!isDivergeTriedRevert && rb_->numCall() >= 1) {
-        // get back to the working rc size
-        rb_->revertGCellSizeToMinRc();
-        curA = route_snapshotA;
-        wireLengthCoefX_ = route_snapshot_WlCoefX;
-        wireLengthCoefY_ = route_snapshot_WlCoefY;
-        nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
-        for (auto& nb : nbVec_) {
-          nb->revertDivergence();
-        }
-
-        isDiverged_ = false;
-        divergeCode_ = 0;
-        divergeMsg_ = "";
-        isDivergeTriedRevert = true;
-        // turn off the RD forcely
-        isRoutabilityNeed_ = false;
-      } else if (!npVars_.disableRevertIfDiverge) {
+      log_->report("Divergence occured in {} regions.", numDiverge);
+
+      // TODO: this divergence treatment uses the non-deterministic aspect of
+      // routability inflation to try one more time if a divergence is detected.
+      // This feature lost its consistency since we allow for non-virtual timing
+      // driven iterations. Meaning we would go back to a snapshot without newly
+      // added instances. A way to maintain this feature is to store two
+      // snapshots one for routability revert if diverge and try again, and
+      // another for simply revert if diverge and finish without hitting 0.10
+      // overflow.
+      // // revert back to the original rb solutions
+      // // one more opportunity
+      // if (!isDivergeTriedRevert && rb_->numCall() >= 1) {
+      //   // get back to the working rc size
+      //   rb_->revertGCellSizeToMinRc();
+      //   curA = route_snapshotA;
+      //   wireLengthCoefX_ = route_snapshot_WlCoefX;
+      //   wireLengthCoefY_ = route_snapshot_WlCoefY;
+      //   nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
+      //   for (auto& nb : nbVec_) {
+      //     nb->revertToSnapshot();
+      //   }
+
+      //   isDiverged_ = false;
+      //   divergeCode_ = 0;
+      //   divergeMsg_ = "";
+      //   isDivergeTriedRevert = true;
+      //   // turn off the RD forcely
+      //   is_routability_need_ = false;
+      // } else
+      if (!npVars_.disableRevertIfDiverge && is_diverge_snapshot_saved) {
         // In case diverged and not in routability mode, finish with min hpwl
         // stored since overflow below 0.25
         log_->warn(GPL,
@@ -570,7 +586,7 @@ int NesterovPlace::doNesterovPlace(int start_iter)
         wireLengthCoefY_ = diverge_snapshot_WlCoefY;
         nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
         for (auto& nb : nbVec_) {
-          nb->revertDivergence();
+          nb->revertToSnapshot();
         }
         isDiverged_ = false;
         break;
@@ -579,8 +595,8 @@ int NesterovPlace::doNesterovPlace(int start_iter)
       }
     }
 
-    if (!is_routability_snapshot_saved && npVars_.routabilityDrivenMode
-        && 0.6 >= average_overflow_unscaled_) {
+    if (!is_routability_snapshot_saved && npVars_.routability_driven_mode
+        && routability_save_snapshot_ >= average_overflow_unscaled_) {
       route_snapshot_WlCoefX = wireLengthCoefX_;
       route_snapshot_WlCoefY = wireLengthCoefY_;
       route_snapshotA = curA;
@@ -594,16 +610,16 @@ int NesterovPlace::doNesterovPlace(int start_iter)
     }
 
     // check routability using RUDY or GR
-    if (npVars_.routabilityDrivenMode && isRoutabilityNeed_
-        && npVars_.routabilityCheckOverflow >= average_overflow_unscaled_) {
+    if (npVars_.routability_driven_mode && is_routability_need_
+        && npVars_.routability_end_overflow >= average_overflow_unscaled_) {
       // recover the densityPenalty values
       // if further routability-driven is needed
       std::pair<bool, bool> result = rb_->routability();
-      isRoutabilityNeed_ = result.first;
+      is_routability_need_ = result.first;
       bool isRevertInitNeeded = result.second;
 
       // if routability is needed
-      if (isRoutabilityNeed_ || isRevertInitNeeded) {
+      if (is_routability_need_ || isRevertInitNeeded) {
         // cutFillerCoordinates();
 
         // revert back the current density penality
@@ -614,7 +630,7 @@ int NesterovPlace::doNesterovPlace(int start_iter)
         nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
 
         for (auto& nb : nbVec_) {
-          nb->revertDivergence();
+          nb->revertToSnapshot();
           nb->resetMinSumOverflow();
         }
         log_->info(GPL, 89, "Routability: revert back to snapshot");

src/gpl/src/nesterovPlace.h

@@ -139,7 +139,8 @@ class NesterovPlace
   int64_t prevHpwl_ = 0;
 
   bool isDiverged_ = false;
-  bool isRoutabilityNeed_ = true;
+  bool is_routability_need_ = true;
+  float routability_save_snapshot_ = 0.6;
 
   std::string divergeMsg_;
   int divergeCode_ = 0;

src/gpl/src/replace.cpp

@@ -341,14 +341,14 @@ bool Replace::initNesterovPlace(int threads)
     npVars.minPhiCoef = minPhiCoef_;
     npVars.maxPhiCoef = maxPhiCoef_;
     npVars.referenceHpwl = referenceHpwl_;
-    npVars.routabilityCheckOverflow = routabilityCheckOverflow_;
+    npVars.routability_end_overflow = routabilityCheckOverflow_;
     npVars.keepResizeBelowOverflow = keepResizeBelowOverflow_;
     npVars.initDensityPenalty = initDensityPenalityFactor_;
     npVars.initWireLengthCoef = initWireLengthCoef_;
     npVars.targetOverflow = overflow_;
     npVars.maxNesterovIter = nesterovPlaceMaxIter_;
     npVars.timingDrivenMode = timingDrivenMode_;
-    npVars.routabilityDrivenMode = routabilityDrivenMode_;
+    npVars.routability_driven_mode = routabilityDrivenMode_;
     npVars.debug = gui_debug_;
     npVars.debug_pause_iterations = gui_debug_pause_iterations_;
     npVars.debug_update_iterations = gui_debug_update_iterations_;

src/gpl/src/replace.tcl

@@ -130,7 +130,7 @@ proc global_placement { args } {
     if { [info exists keys(-timing_driven_net_reweight_overflow)] } {
       set overflow_list $keys(-timing_driven_net_reweight_overflow)
     } else {
-      set overflow_list [list 79 64 49 29 21 15]
+      set overflow_list [list 79 64 29 21 15]
     }
 
     foreach overflow $overflow_list {

src/gpl/test/convergence01.ok

@@ -49,7 +49,7 @@
 [INFO GPL-0029] BinSize: (  1.377  1.350 )
 [INFO GPL-0030] NumBins: 64
 [NesterovSolve] Iter:    1 overflow: 0.127 HPWL: 397899
-[INFO GPL-0100] Timing-driven iteration 1/6, virtual: false.
+[INFO GPL-0100] Timing-driven iteration 1/5, virtual: false.
 [INFO GPL-0101] Iter: 0, overflow: 0.127, keep rsz at: 0.3
 [INFO GPL-0106] Timing-driven: worst slack 6.35e-09
 [INFO GPL-0103] Timing-driven: weighted 4 nets.

src/gpl/test/gpl_aux.py

@@ -64,7 +64,7 @@ def global_placement(
         if timing_driven_net_reweight_overflow != None:
             overflow_list = timing_driven_net_reweight_overflow
         else:
-            overflow_list = [79, 64, 49, 29, 21, 15]
+            overflow_list = [79, 64, 29, 21, 15]
 
         for ov in overflow_list:
             gpl.addTimingNetWeightOverflow(ov)