gpl: revert if diverge

src/gpl/README.md

@@ -97,6 +97,7 @@ global_placement
     [-timing_driven_net_weight_max]
     [-timing_driven_nets_percentage]
     [-keep_resize_below_overflow]
+    [-allow_revert_if_diverge]
 ```
 
 #### Options
@@ -119,6 +120,7 @@ global_placement
 | `-pad_left` | Set left padding in terms of number of sites. The default value is 0, and the allowed values are integers `[1, MAX_INT]` |
 | `-pad_right` | Set right padding in terms of number of sites. The default value is 0, and the allowed values are integers `[1, MAX_INT]` |
 | `-skip_io` | Flag to ignore the IO ports when computing wirelength during placement. The default value is False, allowed values are boolean. |
+| `-allow_revert_if_diverge` | Flag to make gpl store the placement state along iterations, if a divergence is detected, gpl reverts to the snapshot state. The default value is disabled. |
 
 #### Routability-Driven Arguments
 

src/gpl/include/gpl/Replace.h

@@ -119,18 +119,16 @@ class Replace
   void setTimingDrivenMode(bool mode);
 
   void setSkipIoMode(bool mode);
+  void setAllowRevertIfDiverge(bool mode);
 
   void setRoutabilityDrivenMode(bool mode);
   void setRoutabilityUseGrt(bool mode);
   void setRoutabilityCheckOverflow(float overflow);
   void setRoutabilityMaxDensity(float density);
-
   void setRoutabilityMaxInflationIter(int iter);
-
   void setRoutabilityTargetRcMetric(float rc);
   void setRoutabilityInflationRatioCoef(float coef);
   void setRoutabilityMaxInflationRatio(float ratio);
-
   void setRoutabilityRcCoefficients(float k1, float k2, float k3, float k4);
 
   void addTimingNetWeightOverflow(int overflow);
@@ -204,6 +202,7 @@ class Replace
   bool routabilityUseRudy_ = true;
   bool uniformTargetDensityMode_ = false;
   bool skipIoMode_ = false;
+  bool allowRevertIfDiverge_ = false;
 
   std::vector<int> timingNetWeightOverflows_;
 

src/gpl/src/nesterovBase.h

@@ -782,6 +782,7 @@ class NesterovPlaceVars
   bool timingDrivenMode = true;
   int timingDrivenIterCounter = 0;
   bool routabilityDrivenMode = true;
+  bool allowRevertIfDiverge = false;
 
   bool debug = false;
   int debug_pause_iterations = 10;

src/gpl/src/nesterovPlace.cpp

@@ -318,14 +318,16 @@ int NesterovPlace::doNesterovPlace(int start_iter)
     graphics_->cellPlot(true);
   }
 
-  // snapshot saving detection
-  bool isSnapshotSaved = false;
-
-  // snapshot info
-  float snapshotA = 0;
-  float snapshotWlCoefX = 0, snapshotWlCoefY = 0;
+  // routability snapshot info
+  bool is_routability_snapshot_saved = false;
+  float route_snapshotA = 0;
+  float route_snapshotWlCoefX = 0, route_snapshotWlCoefY = 0;
   bool isDivergeTriedRevert = false;
 
+  // divergence snapshot info
+  float diverge_snapshotA = 0;
+  float diverge_snapshotWlCoefX = 0, diverge_snapshotWlCoefY = 0;
+
   // backTracking variable.
   float curA = 1.0;
 
@@ -342,7 +344,6 @@ int NesterovPlace::doNesterovPlace(int start_iter)
 
     // here, prevA is a_(k), curA is a_(k+1)
     // See, the ePlace-MS paper's Algorithm 1
-    //
     curA = (1.0 + sqrt(4.0 * prevA * prevA + 1.0)) * 0.5;
 
     // coeff is (a_k - 1) / ( a_(k+1) ) in paper.
@@ -412,9 +413,19 @@ int NesterovPlace::doNesterovPlace(int start_iter)
 
     updateNextIter(iter);
 
+    if (npVars_.allowRevertIfDiverge) {
+      if (is_min_hpwl_) {
+        diverge_snapshotWlCoefX = wireLengthCoefX_;
+        diverge_snapshotWlCoefY = wireLengthCoefY_;
+        diverge_snapshotA = curA;
+        for (auto& nb : nbVec_) {
+          nb->snapshot();
+        }
+      }
+    }
+
     // For JPEG Saving
     // debug
-
     const int debug_start_iter = npVars_.debug_start_iter;
     if (graphics_ && (debug_start_iter == 0 || iter + 1 >= debug_start_iter)) {
       bool update
@@ -531,13 +542,10 @@ int NesterovPlace::doNesterovPlace(int start_iter)
       if (!isDivergeTriedRevert && rb_->numCall() >= 1) {
         // get back to the working rc size
         rb_->revertGCellSizeToMinRc();
-
-        curA = snapshotA;
-        wireLengthCoefX_ = snapshotWlCoefX;
-        wireLengthCoefY_ = snapshotWlCoefY;
-
+        curA = route_snapshotA;
+        wireLengthCoefX_ = route_snapshotWlCoefX;
+        wireLengthCoefY_ = route_snapshotWlCoefY;
         nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
-
         for (auto& nb : nbVec_) {
           nb->revertDivergence();
         }
@@ -548,27 +556,47 @@ int NesterovPlace::doNesterovPlace(int start_iter)
         isDivergeTriedRevert = true;
         // turn off the RD forcely
         isRoutabilityNeed_ = false;
+      } else if (npVars_.allowRevertIfDiverge) {
+        // In case diverged and not in routability mode, finish with min hpwl
+        // stored since overflow below 0.25
+        log_->warn(GPL,
+                   90,
+                   "Divergence detected, reverting to snapshot with min hpwl.");
+        log_->warn(GPL,
+                   91,
+                   "Revert to iter: {:4d} overflow: {:.3f} HPWL: {}",
+                   diverge_snapshot_iter_,
+                   diverge_snapshot_average_overflow_unscaled_,
+                   min_hpwl_);
+        curA = diverge_snapshotA;
+        wireLengthCoefX_ = diverge_snapshotWlCoefX;
+        wireLengthCoefY_ = diverge_snapshotWlCoefY;
+        nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
+        for (auto& nb : nbVec_) {
+          nb->revertDivergence();
+        }
+        isDiverged_ = false;
+        break;
       } else {
-        // no way to revert
         break;
       }
     }
 
-    if (!isSnapshotSaved && npVars_.routabilityDrivenMode
+    if (!is_routability_snapshot_saved && npVars_.routabilityDrivenMode
         && 0.6 >= average_overflow_unscaled_) {
-      snapshotWlCoefX = wireLengthCoefX_;
-      snapshotWlCoefY = wireLengthCoefY_;
-      snapshotA = curA;
-      isSnapshotSaved = true;
+      route_snapshotWlCoefX = wireLengthCoefX_;
+      route_snapshotWlCoefY = wireLengthCoefY_;
+      route_snapshotA = curA;
+      is_routability_snapshot_saved = true;
 
       for (auto& nb : nbVec_) {
         nb->snapshot();
       }
 
-      log_->report("[NesterovSolve] Snapshot saved at iter = {}", iter);
+      log_->info(GPL, 88, "Routability snapshot saved at iter = {}", iter);
     }
 
-    // check routability using GR
+    // check routability using RUDY or GR
     if (npVars_.routabilityDrivenMode && isRoutabilityNeed_
         && npVars_.routabilityCheckOverflow >= average_overflow_unscaled_) {
       // recover the densityPenalty values
@@ -582,17 +610,17 @@ int NesterovPlace::doNesterovPlace(int start_iter)
         // cutFillerCoordinates();
 
         // revert back the current density penality
-        curA = snapshotA;
-        wireLengthCoefX_ = snapshotWlCoefX;
-        wireLengthCoefY_ = snapshotWlCoefY;
+        curA = route_snapshotA;
+        wireLengthCoefX_ = route_snapshotWlCoefX;
+        wireLengthCoefY_ = route_snapshotWlCoefY;
 
         nbc_->updateWireLengthForceWA(wireLengthCoefX_, wireLengthCoefY_);
 
         for (auto& nb : nbVec_) {
           nb->revertDivergence();
           nb->resetMinSumOverflow();
         }
-        log_->report("[NesterovSolve] Revert back to snapshot coordi");
+        log_->info(GPL, 89, "Routability: revert back to snapshot");
       }
     }
 
@@ -658,6 +686,19 @@ void NesterovPlace::updateNextIter(const int iter)
 
   // For coefficient, using average regions' overflow
   updateWireLengthCoef(average_overflow_);
+
+  // Update divergence snapshot
+  if (npVars_.allowRevertIfDiverge) {
+    int64_t hpwl = nbc_->getHpwl();
+    if (hpwl < min_hpwl_ && average_overflow_unscaled_ <= 0.25) {
+      min_hpwl_ = hpwl;
+      diverge_snapshot_average_overflow_unscaled_ = average_overflow_unscaled_;
+      diverge_snapshot_iter_ = iter;
+      is_min_hpwl_ = true;
+    } else {
+      is_min_hpwl_ = false;
+    }
+  }
 }
 
 void NesterovPlace::updateDb()

src/gpl/src/nesterovPlace.h

@@ -115,9 +115,16 @@ class NesterovPlace
 
   float total_sum_overflow_ = 0;
   float total_sum_overflow_unscaled_ = 0;
+  // The average here is between regions (NB objects)
   float average_overflow_ = 0;
   float average_overflow_unscaled_ = 0;
 
+  // Snapshot saving for revert if diverge
+  float diverge_snapshot_average_overflow_unscaled_ = 0;
+  int64_t min_hpwl_ = INT64_MAX;
+  int diverge_snapshot_iter_ = 0;
+  bool is_min_hpwl_ = false;
+
   // densityPenalty stor
   std::vector<float> densityPenaltyStor_;
 

src/gpl/src/replace.cpp

@@ -118,6 +118,7 @@ void Replace::reset()
   routabilityUseRudy_ = true;
   uniformTargetDensityMode_ = false;
   skipIoMode_ = false;
+  allowRevertIfDiverge_ = false;
 
   padLeft_ = padRight_ = 0;
 
@@ -354,6 +355,7 @@ bool Replace::initNesterovPlace(int threads)
     npVars.debug_draw_bins = gui_debug_draw_bins_;
     npVars.debug_inst = gui_debug_inst_;
     npVars.debug_start_iter = gui_debug_start_iter_;
+    npVars.allowRevertIfDiverge = allowRevertIfDiverge_;
 
     for (const auto& nb : nbVec_) {
       nb->setNpVars(&npVars);
@@ -375,7 +377,20 @@ int Replace::doNesterovPlace(int threads, int start_iter)
   if (timingDrivenMode_) {
     rs_->resizeSlackPreamble();
   }
-  return np_->doNesterovPlace(start_iter);
+
+  auto start = std::chrono::high_resolution_clock::now();
+
+  int return_do_nesterov = np_->doNesterovPlace(start_iter);
+
+  auto end = std::chrono::high_resolution_clock::now();
+  std::chrono::duration<double> elapsed = end - start;
+  debugPrint(log_,
+             GPL,
+             "runtime",
+             1,
+             "NP->doNesterovPlace() runtime: {} seconds ",
+             elapsed.count());
+  return return_do_nesterov;
 }
 
 void Replace::setInitialPlaceMaxIter(int iter)
@@ -485,6 +500,11 @@ void Replace::setDebug(int pause_iterations,
   gui_debug_start_iter_ = start_iter;
 }
 
+void Replace::setAllowRevertIfDiverge(bool mode)
+{
+  allowRevertIfDiverge_ = mode;
+}
+
 void Replace::setSkipIoMode(bool mode)
 {
   skipIoMode_ = mode;

src/gpl/src/replace.i

@@ -250,6 +250,13 @@ set_skip_io_mode_cmd(bool mode)
   replace->setSkipIoMode(mode);
 }
 
+void
+  set_allow_revert_if_diverge(bool allow_revert_if_diverge)
+{
+  Replace* replace = getReplace();
+  replace->setAllowRevertIfDiverge(allow_revert_if_diverge);
+}
+
 float
 get_global_placement_uniform_density_cmd() 
 {

src/gpl/src/replace.tcl

@@ -64,6 +64,7 @@ sta::define_cmd_args "global_placement" {\
     [-timing_driven_nets_percentage timing_driven_nets_percentage]\
     [-pad_left pad_left]\
     [-pad_right pad_right]\
+    [-allow_revert_if_diverge]\
 }
 
 proc global_placement { args } {
@@ -92,7 +93,8 @@ proc global_placement { args } {
       -disable_timing_driven \
       -disable_routability_driven \
       -skip_io \
-      -incremental}
+      -incremental\
+      -allow_revert_if_diverge}
 
   # flow control for initial_place
   if { [info exists flags(-skip_initial_place)] } {
@@ -327,6 +329,14 @@ proc global_placement { args } {
   } else {
     utl::error GPL 130 "No rows defined in design. Use initialize_floorplan to add rows."
   }
+
+  # Revert to saved snapshot if a divergence is detected.
+  set allow_revert_if_diverge [info exists flags(-allow_revert_if_diverge)]
+  gpl::set_allow_revert_if_diverge $allow_revert_if_diverge
+  if { $allow_revert_if_diverge } {
+    utl::info "GPL" 153 \
+      "Allow revert to saved snapshot if a divergence is detected."
+  }
 }
 
 

src/gpl/test/simple01-rd.ok

@@ -59,7 +59,7 @@
 [NesterovSolve] Iter:  190 overflow: 0.683 HPWL: 4375212
 [NesterovSolve] Iter:  200 overflow: 0.661 HPWL: 4447293
 [NesterovSolve] Iter:  210 overflow: 0.625 HPWL: 4516566
-[NesterovSolve] Snapshot saved at iter = 216
+[INFO GPL-0088] Routability snapshot saved at iter = 216
 [NesterovSolve] Iter:  220 overflow: 0.586 HPWL: 4589913
 [NesterovSolve] Iter:  230 overflow: 0.547 HPWL: 4672006
 [NesterovSolve] Iter:  240 overflow: 0.494 HPWL: 4711101

src/gpl/test/simple02-rd.ok

@@ -59,7 +59,7 @@
 [NesterovSolve] Iter:  190 overflow: 0.683 HPWL: 4375212
 [NesterovSolve] Iter:  200 overflow: 0.661 HPWL: 4447293
 [NesterovSolve] Iter:  210 overflow: 0.625 HPWL: 4516566
-[NesterovSolve] Snapshot saved at iter = 216
+[INFO GPL-0088] Routability snapshot saved at iter = 216
 [NesterovSolve] Iter:  220 overflow: 0.586 HPWL: 4589913
 [NesterovSolve] Iter:  230 overflow: 0.547 HPWL: 4672006
 [NesterovSolve] Iter:  240 overflow: 0.494 HPWL: 4711101

src/gpl/test/simple03-rd.ok

@@ -58,7 +58,7 @@
 [NesterovSolve] Iter:  190 overflow: 0.683 HPWL: 4375212
 [NesterovSolve] Iter:  200 overflow: 0.661 HPWL: 4447293
 [NesterovSolve] Iter:  210 overflow: 0.625 HPWL: 4516566
-[NesterovSolve] Snapshot saved at iter = 216
+[INFO GPL-0088] Routability snapshot saved at iter = 216
 [NesterovSolve] Iter:  220 overflow: 0.586 HPWL: 4589913
 [NesterovSolve] Iter:  230 overflow: 0.547 HPWL: 4672006
 [NesterovSolve] Iter:  240 overflow: 0.494 HPWL: 4711101

src/gpl/test/simple04-rd.ok

@@ -58,7 +58,7 @@
 [NesterovSolve] Iter:  190 overflow: 0.683 HPWL: 4375212
 [NesterovSolve] Iter:  200 overflow: 0.661 HPWL: 4447293
 [NesterovSolve] Iter:  210 overflow: 0.625 HPWL: 4516566
-[NesterovSolve] Snapshot saved at iter = 216
+[INFO GPL-0088] Routability snapshot saved at iter = 216
 [NesterovSolve] Iter:  220 overflow: 0.586 HPWL: 4589913
 [NesterovSolve] Iter:  230 overflow: 0.547 HPWL: 4672006
 [NesterovSolve] Iter:  240 overflow: 0.494 HPWL: 4711101