[CP-SAT] add test; change default parameters; fix crash on shared workers

ortools/sat/BUILD.bazel

@@ -1873,6 +1873,7 @@ cc_library(
         ":sat_base",
         ":sat_parameters_cc_proto",
         "//ortools/base",
+        "//ortools/base:mathlimits",
         "//ortools/base:mathutil",
         "//ortools/base:stl_util",
         "//ortools/util:random_engine",

ortools/sat/python/cp_model_test.py

@@ -1014,6 +1014,12 @@ class CpModelTest(absltest.TestCase):
         self.assertEqual(size_expr, 2)
         self.assertEqual(str(end_expr), "(x + 2)")
 
+    def testAbsentInterval(self):
+        print("testInterval")
+        model = cp_model.CpModel()
+        i = model.new_optional_interval_var(1, 0, 1, False, "")
+        self.assertEqual(0, i.index)
+
     def testOptionalInterval(self):
         print("testOptionalInterval")
         model = cp_model.CpModel()

ortools/sat/samples/code_samples.bzl

@@ -16,7 +16,6 @@
 load("@pip_deps//:requirements.bzl", "requirement")
 load("@rules_python//python:defs.bzl", "py_binary", "py_test")
 
-
 def code_sample_cc(name):
     native.cc_binary(
         name = name + "_cc",

ortools/sat/sat_parameters.proto

@@ -1094,7 +1094,7 @@ message SatParameters {
   // Minimum number of restarts before a worker will replace a subtree
   // that looks "bad" based on the average LBD of learned clauses.
   optional int32 shared_tree_worker_min_restarts_per_subtree = 282
-      [default = 32];
+      [default = 1];
 
   // If true, workers share more of the information from their local trail.
   // Specifically, literals implied by the shared tree decisions and

ortools/sat/util.h

@@ -36,6 +36,7 @@
 #include "absl/strings/string_view.h"
 #include "absl/types/span.h"
 #include "ortools/base/logging.h"
+#include "ortools/base/mathlimits.h"
 #include "ortools/sat/model.h"
 #include "ortools/sat/sat_base.h"
 #include "ortools/sat/sat_parameters.pb.h"

ortools/sat/work_assignment.cc

@@ -626,15 +626,15 @@ bool SharedTreeWorker::AddImplications() {
   rev_num_processed_implications_.resize(level + 1, 0);
   auto& num_processed_implications = rev_num_processed_implications_[level];
   reversible_int_repository_->SaveState(&num_processed_implications);
-  absl::Span<const ProtoLiteral> implied_literals =
-      assigned_tree_.Implications(level).subspan(num_processed_implications);
+  absl::Span<const Literal> implied_literals =
+      absl::MakeConstSpan(assigned_tree_implications_[level - 1])
+          .subspan(num_processed_implications);
   bool added_clause = false;
-  for (const ProtoLiteral& impl : implied_literals) {
-    Literal lit(DecodeDecision(impl));
+  for (Literal impl : implied_literals) {
     ++num_processed_implications;
-    if (sat_solver_->Assignment().LiteralIsTrue(lit)) continue;
+    if (sat_solver_->Assignment().LiteralIsTrue(impl)) continue;
     added_clause = true;
-    if (!AddDecisionImplication(lit, level)) return true;
+    if (!AddDecisionImplication(impl, level)) return true;
   }
   if (objective_ != nullptr &&
       objective_->objective_var != kNoIntegerVariable) {
@@ -687,10 +687,19 @@ bool SharedTreeWorker::SyncWithLocalTrail() {
               << " assigned=" << assigned_tree_.MaxLevel();
       manager_->CloseTree(assigned_tree_, level + 1);
       assigned_tree_literals_.clear();
+      assigned_tree_implications_.clear();
       sat_solver_->Backtrack(0);
     } else {
       // The next level is implied by the current one.
       assigned_tree_.SetLevelImplied(level + 1);
+      if (level > 0) {
+        assigned_tree_implications_[level - 1].insert(
+            assigned_tree_implications_[level - 1].end(),
+            assigned_tree_implications_[level].begin(),
+            assigned_tree_implications_[level].end());
+      }
+      assigned_tree_implications_.erase(assigned_tree_implications_.begin() +
+                                        level);
       assigned_tree_literals_.erase(assigned_tree_literals_.begin() + level);
     }
   }
@@ -760,6 +769,7 @@ void SharedTreeWorker::MaybeProposeSplit() {
     manager_->ProposeSplit(assigned_tree_, *encoded);
     if (assigned_tree_.MaxLevel() > assigned_tree_literals_.size()) {
       assigned_tree_literals_.push_back(split_decision);
+      assigned_tree_implications_.push_back({});
     }
     CHECK_EQ(assigned_tree_literals_.size(), assigned_tree_.MaxLevel());
   }
@@ -808,9 +818,15 @@ bool SharedTreeWorker::SyncWithSharedTree() {
   VLOG(2) << "Assigned level: " << assigned_tree_.MaxLevel() << " "
           << parameters_->name();
   assigned_tree_literals_.clear();
+  assigned_tree_implications_.clear();
   for (int i = 1; i <= assigned_tree_.MaxLevel(); ++i) {
     assigned_tree_literals_.push_back(
         DecodeDecision(assigned_tree_.Decision(i)));
+    std::vector<Literal> implications;
+    for (const ProtoLiteral& impl : assigned_tree_.Implications(i)) {
+      implications.push_back(DecodeDecision(impl));
+    }
+    assigned_tree_implications_.push_back(std::move(implications));
   }
   return true;
 }

ortools/sat/work_assignment.h

@@ -67,6 +67,7 @@ class ProtoLiteral {
     return H::combine(std::move(h), literal.proto_var_, literal.lb_);
   }
 
+  // Note you should only decode integer literals at the root level.
   Literal Decode(CpModelMapping*, IntegerEncoder*) const;
   static std::optional<ProtoLiteral> Encode(Literal, CpModelMapping*,
                                             IntegerEncoder*);
@@ -324,6 +325,7 @@ class SharedTreeWorker {
 
   ProtoTrail assigned_tree_;
   std::vector<Literal> assigned_tree_literals_;
+  std::vector<std::vector<Literal>> assigned_tree_implications_;
   // How many restarts had happened when the current tree was assigned?
   int64_t tree_assignment_restart_ = -1;