[CP-SAT] more minor improvements

ortools/sat/2d_rectangle_presolve.cc

@@ -111,6 +111,7 @@ bool PresolveFixed2dRectangles(
       // The whole rectangle was outside of the domain, remove it.
       std::swap(rectangle, (*fixed_boxes)[fixed_boxes->size() - 1]);
       fixed_boxes->resize(fixed_boxes->size() - 1);
+      changed = true;
       continue;
     } else {
       new_size++;

ortools/sat/disjunctive.cc

@@ -871,18 +871,19 @@ bool DisjunctiveDetectablePrecedences::Propagate() {
   const auto by_shifted_smin = helper_->TaskByIncreasingShiftedStartMin();
   int rank = -1;
   IntegerValue window_end = kMinIntegerValue;
+  int* const ranks = ranks_.data();
   for (const auto [task, presence_lit, start_min] : by_shifted_smin) {
     if (!helper_->IsPresent(presence_lit)) {
-      ranks_[task] = -1;
+      ranks[task] = -1;
       continue;
     }
 
     const IntegerValue size_min = helper_->SizeMin(task);
     if (start_min < window_end) {
-      ranks_[task] = rank;
+      ranks[task] = rank;
       window_end += size_min;
     } else {
-      ranks_[task] = ++rank;
+      ranks[task] = ++rank;
       window_end = start_min + size_min;
     }
   }
@@ -1329,9 +1330,15 @@ bool DisjunctivePrecedences::PropagateSubwindow() {
 
 int DisjunctivePrecedences::RegisterWith(GenericLiteralWatcher* watcher) {
   // This propagator reach the fixed point in one go.
+  // Maybe not in corner cases, but since it is expansive, it is okay not to
+  // run it again right away
+  //
+  // Note also that technically, we don't need to be waked up if only the upper
+  // bound of the task changes, but this require to use more memory and the gain
+  // is unclear as this runs with the highest priority.
   const int id = watcher->Register(this);
   helper_->SetTimeDirection(time_direction_);
-  helper_->WatchAllTasks(id, /*watch_max_side=*/false);
+  helper_->WatchAllTasks(id);
   return id;
 }
 

ortools/sat/integer.cc

@@ -2119,10 +2119,7 @@ void GenericLiteralWatcher::UpdateCallingNeeds(Trail* trail) {
     const Literal literal = (*trail)[propagation_trail_index_++];
     if (literal.Index() >= literal_limit) continue;
     for (const auto entry : literal_to_watcher_[literal]) {
-      if (!in_queue_[entry.id]) {
-        in_queue_[entry.id] = true;
-        queue_by_priority_[id_to_priority_[entry.id]].push_back(entry.id);
-      }
+      CallOnNextPropagate(entry.id);
       if (entry.watch_index >= 0) {
         id_to_watch_indices_[entry.id].push_back(entry.watch_index);
       }
@@ -2134,10 +2131,7 @@ void GenericLiteralWatcher::UpdateCallingNeeds(Trail* trail) {
   for (const IntegerVariable var : modified_vars_.PositionsSetAtLeastOnce()) {
     if (var.value() >= var_limit) continue;
     for (const auto entry : var_to_watcher_[var]) {
-      if (!in_queue_[entry.id]) {
-        in_queue_[entry.id] = true;
-        queue_by_priority_[id_to_priority_[entry.id]].push_back(entry.id);
-      }
+      CallOnNextPropagate(entry.id);
       if (entry.watch_index >= 0) {
         id_to_watch_indices_[entry.id].push_back(entry.watch_index);
       }
@@ -2161,9 +2155,7 @@ bool GenericLiteralWatcher::Propagate(Trail* trail) {
   const int level = trail->CurrentDecisionLevel();
   if (level == 0) {
     for (const int id : propagator_ids_to_call_at_level_zero_) {
-      if (in_queue_[id]) continue;
-      in_queue_[id] = true;
-      queue_by_priority_[id_to_priority_[id]].push_back(id);
+      CallOnNextPropagate(id);
     }
   }
 

ortools/sat/integer.h

@@ -787,6 +787,7 @@ class IntegerTrail final : public SatPropagator {
   void AddAllGreaterThanConstantReason(absl::Span<AffineExpression> exprs,
                                        IntegerValue target_min,
                                        std::vector<int>* indices) const {
+    int64_t num_processed = 0;
     for (const AffineExpression& expr : exprs) {
       if (expr.IsConstant()) {
         DCHECK_GE(expr.constant, target_min);
@@ -794,6 +795,10 @@ class IntegerTrail final : public SatPropagator {
       }
       DCHECK_NE(expr.var, kNoIntegerVariable);
 
+      // On large routing problems, we can spend a lot of time in this loop.
+      // We check the time limit every 5 processed expressions.
+      if (++num_processed % 5 == 0 && time_limit_->LimitReached()) return;
+
       // Skip if we already have an explanation for expr >= target_min. Note
       // that we already do that while processing the returned indices, so this
       // mainly save a FindLowestTrailIndexThatExplainBound() call per skipped
@@ -897,7 +902,7 @@ class IntegerTrail final : public SatPropagator {
   // Returns some debugging info.
   std::string DebugString();
 
-  // Used internally to return the next conlict number.
+  // Used internally to return the next conflict number.
   int64_t NextConflictId();
 
   // Information for each integer variable about its current lower bound and

ortools/sat/intervals.cc

@@ -214,6 +214,12 @@ SchedulingConstraintHelper* IntervalsRepository::GetOrCreateHelper(
   std::vector<AffineExpression> sizes;
   std::vector<LiteralIndex> reason_for_presence;
 
+  const int num_variables = variables.size();
+  starts.reserve(num_variables);
+  ends.reserve(num_variables);
+  sizes.reserve(num_variables);
+  reason_for_presence.reserve(num_variables);
+
   for (const IntervalVariable i : variables) {
     if (IsOptional(i)) {
       reason_for_presence.push_back(PresenceLiteral(i).Index());
@@ -224,6 +230,7 @@ SchedulingConstraintHelper* IntervalsRepository::GetOrCreateHelper(
     starts.push_back(Start(i));
     ends.push_back(End(i));
   }
+
   SchedulingConstraintHelper* helper = new SchedulingConstraintHelper(
       std::move(starts), std::move(ends), std::move(sizes),
       std::move(reason_for_presence), model_);

ortools/sat/scheduling_helpers.cc

@@ -20,7 +20,6 @@
 #include <utility>
 #include <vector>
 
-#include "absl/container/flat_hash_map.h"
 #include "absl/log/check.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/str_cat.h"
@@ -47,8 +46,8 @@ SchedulingConstraintHelper::SchedulingConstraintHelper(
     std::vector<AffineExpression> sizes,
     std::vector<LiteralIndex> reason_for_presence, Model* model)
     : model_(model),
-      trail_(model->GetOrCreate<Trail>()),
       sat_solver_(model->GetOrCreate<SatSolver>()),
+      assignment_(sat_solver_->Assignment()),
       integer_trail_(model->GetOrCreate<IntegerTrail>()),
       watcher_(model->GetOrCreate<GenericLiteralWatcher>()),
       precedence_relations_(model->GetOrCreate<PrecedenceRelations>()),
@@ -64,15 +63,17 @@ SchedulingConstraintHelper::SchedulingConstraintHelper(
       cached_negated_end_max_(new IntegerValue[capacity_]),
       cached_shifted_start_min_(new IntegerValue[capacity_]),
       cached_negated_shifted_end_max_(new IntegerValue[capacity_]) {
-  minus_ends_.clear();
-  minus_starts_.clear();
   DCHECK_EQ(starts_.size(), ends_.size());
   DCHECK_EQ(starts_.size(), sizes_.size());
   DCHECK_EQ(starts_.size(), reason_for_presence_.size());
 
+  minus_starts_.clear();
+  minus_starts_.reserve(starts_.size());
+  minus_ends_.clear();
+  minus_ends_.reserve(starts_.size());
   for (int i = 0; i < starts_.size(); ++i) {
-    minus_ends_.push_back(ends_[i].Negated());
     minus_starts_.push_back(starts_[i].Negated());
+    minus_ends_.push_back(ends_[i].Negated());
   }
 
   InitSortedVectors();
@@ -84,8 +85,8 @@ SchedulingConstraintHelper::SchedulingConstraintHelper(
 SchedulingConstraintHelper::SchedulingConstraintHelper(int num_tasks,
                                                        Model* model)
     : model_(model),
-      trail_(model->GetOrCreate<Trail>()),
       sat_solver_(model->GetOrCreate<SatSolver>()),
+      assignment_(sat_solver_->Assignment()),
       integer_trail_(model->GetOrCreate<IntegerTrail>()),
       precedence_relations_(model->GetOrCreate<PrecedenceRelations>()),
       capacity_(num_tasks),
@@ -120,6 +121,16 @@ void SchedulingConstraintHelper::RegisterWith(GenericLiteralWatcher* watcher) {
     watcher->WatchIntegerVariable(sizes_[t].var, id, t);
     watcher->WatchIntegerVariable(starts_[t].var, id, t);
     watcher->WatchIntegerVariable(ends_[t].var, id, t);
+
+    // This class do not need to be waked up on presence change, since this is
+    // not cached. However given that we can have many propagators that use the
+    // same helper, it is nicer to only register this one, and wake up all
+    // propagator through it rather than registering all of them individually.
+    // Note that IncrementalPropagate() will do nothing if this is the only
+    // change except waking up registered propagators.
+    if (!IsPresent(t) && !IsAbsent(t)) {
+      watcher_->WatchLiteral(Literal(reason_for_presence_[t]), id);
+    }
   }
   watcher->SetPropagatorPriority(id, 0);
 }
@@ -352,7 +363,7 @@ IntegerValue SchedulingConstraintHelper::GetCurrentMinDistanceBetweenTasks(
 bool SchedulingConstraintHelper::PropagatePrecedence(int a, int b) {
   CHECK(IsPresent(a));
   CHECK(IsPresent(b));
-  CHECK_EQ(trail_->CurrentDecisionLevel(), 0);
+  CHECK_EQ(sat_solver_->CurrentDecisionLevel(), 0);
 
   const AffineExpression before = ends_[a];
   const AffineExpression after = starts_[b];
@@ -370,7 +381,7 @@ bool SchedulingConstraintHelper::PropagatePrecedence(int a, int b) {
     AddWeightedSumLowerOrEqual({}, {before.var, after.var},
                                {int64_t{1}, int64_t{-1}}, -offset.value(),
                                model_);
-    if (model_->GetOrCreate<SatSolver>()->ModelIsUnsat()) return false;
+    if (sat_solver_->ModelIsUnsat()) return false;
   }
   return true;
 }
@@ -609,30 +620,11 @@ bool SchedulingConstraintHelper::ReportConflict() {
   return integer_trail_->ReportConflict(literal_reason_, integer_reason_);
 }
 
-void SchedulingConstraintHelper::WatchAllTasks(int id, bool watch_max_side) {
-  // In all cases, we watch presence literals since this class is not waked up
-  // when those changes.
-  const int num_tasks = starts_.size();
-  for (int t = 0; t < num_tasks; ++t) {
-    if (!IsPresent(t) && !IsAbsent(t)) {
-      watcher_->WatchLiteral(Literal(reason_for_presence_[t]), id);
-    }
-  }
-
-  // If everything is watched, it is slighlty more efficient to enqueue the
-  // propagator when the helper Propagate() is called. This result in less
-  // entries in our watched lists.
-  if (watch_max_side) {
-    propagator_ids_.push_back(id);
-    return;
-  }
-
-  // We only watch "min" side.
-  for (int t = 0; t < num_tasks; ++t) {
-    watcher_->WatchLowerBound(starts_[t], id);
-    watcher_->WatchLowerBound(ends_[t], id);
-    watcher_->WatchLowerBound(sizes_[t], id);
-  }
+void SchedulingConstraintHelper::WatchAllTasks(int id) {
+  // It is more efficient to enqueue the propagator
+  // when the helper Propagate() is called. This result in less entries in our
+  // watched lists.
+  propagator_ids_.push_back(id);
 }
 
 void SchedulingConstraintHelper::AddOtherReason(int t) {

ortools/sat/scheduling_helpers.h

@@ -318,7 +318,7 @@ class SchedulingConstraintHelper : public PropagatorInterface {
 
   // Registers the given propagator id to be called if any of the tasks
   // in this class change. Note that we do not watch size max though.
-  void WatchAllTasks(int id, bool watch_max_side = true);
+  void WatchAllTasks(int id);
 
   // Manages the other helper (used by the diffn constraint).
   //
@@ -349,7 +349,9 @@ class SchedulingConstraintHelper : public PropagatorInterface {
   // not handle this correctly.
   bool InPropagationLoop() const { return integer_trail_->InPropagationLoop(); }
 
-  int CurrentDecisionLevel() const { return trail_->CurrentDecisionLevel(); }
+  int CurrentDecisionLevel() const {
+    return sat_solver_->CurrentDecisionLevel();
+  }
 
  private:
   // Tricky: when a task is optional, it is possible it size min is negative,
@@ -384,8 +386,8 @@ class SchedulingConstraintHelper : public PropagatorInterface {
   void ImportOtherReasons();
 
   Model* model_;
-  Trail* trail_;
   SatSolver* sat_solver_;
+  const VariablesAssignment& assignment_;
   IntegerTrail* integer_trail_;
   GenericLiteralWatcher* watcher_;
   PrecedenceRelations* precedence_relations_;
@@ -610,17 +612,25 @@ inline bool SchedulingConstraintHelper::SizeIsFixed(int t) const {
 }
 
 inline bool SchedulingConstraintHelper::IsOptional(int t) const {
-  return reason_for_presence_[t] != kNoLiteralIndex;
+  DCHECK_GE(t, 0);
+  DCHECK_LT(t, reason_for_presence_.size());
+  return reason_for_presence_.data()[t] != kNoLiteralIndex;
 }
 
 inline bool SchedulingConstraintHelper::IsPresent(int t) const {
-  if (reason_for_presence_[t] == kNoLiteralIndex) return true;
-  return trail_->Assignment().LiteralIsTrue(Literal(reason_for_presence_[t]));
+  DCHECK_GE(t, 0);
+  DCHECK_LT(t, reason_for_presence_.size());
+  const LiteralIndex lit = reason_for_presence_.data()[t];
+  if (lit == kNoLiteralIndex) return true;
+  return assignment_.LiteralIsTrue(Literal(lit));
 }
 
 inline bool SchedulingConstraintHelper::IsAbsent(int t) const {
-  if (reason_for_presence_[t] == kNoLiteralIndex) return false;
-  return trail_->Assignment().LiteralIsFalse(Literal(reason_for_presence_[t]));
+  DCHECK_GE(t, 0);
+  DCHECK_LT(t, reason_for_presence_.size());
+  const LiteralIndex lit = reason_for_presence_.data()[t];
+  if (lit == kNoLiteralIndex) return false;
+  return assignment_.LiteralIsFalse(Literal(lit));
 }
 
 inline bool SchedulingConstraintHelper::IsOptional(LiteralIndex lit) const {
@@ -629,12 +639,12 @@ inline bool SchedulingConstraintHelper::IsOptional(LiteralIndex lit) const {
 
 inline bool SchedulingConstraintHelper::IsPresent(LiteralIndex lit) const {
   if (lit == kNoLiteralIndex) return true;
-  return trail_->Assignment().LiteralIsTrue(Literal(lit));
+  return assignment_.LiteralIsTrue(Literal(lit));
 }
 
 inline bool SchedulingConstraintHelper::IsAbsent(LiteralIndex lit) const {
   if (lit == kNoLiteralIndex) return false;
-  return trail_->Assignment().LiteralIsFalse(Literal(lit));
+  return assignment_.LiteralIsFalse(Literal(lit));
 }
 
 inline void SchedulingConstraintHelper::ClearReason() {

ortools/sat/timetable.cc

@@ -21,7 +21,6 @@
 #include "absl/types/span.h"
 #include "ortools/sat/integer.h"
 #include "ortools/sat/integer_base.h"
-#include "ortools/sat/intervals.h"
 #include "ortools/sat/model.h"
 #include "ortools/sat/sat_base.h"
 #include "ortools/sat/scheduling_helpers.h"
@@ -344,7 +343,7 @@ TimeTablingPerTask::TimeTablingPerTask(AffineExpression capacity,
 
 void TimeTablingPerTask::RegisterWith(GenericLiteralWatcher* watcher) {
   const int id = watcher->Register(this);
-  helper_->WatchAllTasks(id, watcher);
+  helper_->WatchAllTasks(id);
   watcher->WatchUpperBound(capacity_.var, id);
   for (int t = 0; t < num_tasks_; t++) {
     watcher->WatchLowerBound(demands_->Demands()[t], id);

ortools/sat/timetable_edgefinding.cc

@@ -49,7 +49,7 @@ TimeTableEdgeFinding::TimeTableEdgeFinding(AffineExpression capacity,
 void TimeTableEdgeFinding::RegisterWith(GenericLiteralWatcher* watcher) {
   const int id = watcher->Register(this);
   watcher->WatchUpperBound(capacity_, id);
-  helper_->WatchAllTasks(id, watcher);
+  helper_->WatchAllTasks(id);
   for (int t = 0; t < num_tasks_; t++) {
     watcher->WatchLowerBound(demands_->Demands()[t], id);
   }