reduce time limit check frequency

ortools/util/time_limit.cc

@@ -14,12 +14,17 @@
 #include "ortools/util/time_limit.h"
 
 #include <algorithm>
+#include <cstdint>
 #include <limits>
 #include <memory>
 #include <string>
 #include <utility>
 
+#include "absl/flags/flag.h"
+#include "absl/log/die_if_null.h"
+#include "absl/log/log.h"
 #include "absl/strings/str_cat.h"
+#include "absl/time/time.h"
 
 ABSL_FLAG(bool, time_limit_use_usertime, false,
           "If true, rely on the user time in the TimeLimit class. This is "
@@ -31,6 +36,13 @@ namespace operations_research {
 const double TimeLimit::kSafetyBufferSeconds = 1e-4;
 const int TimeLimit::kHistorySize = 100;
 
+TimeLimit::TimeLimit(double limit_in_seconds, double deterministic_limit)
+    : safety_buffer_ns_(static_cast<int64_t>(kSafetyBufferSeconds * 1e9)),
+      running_max_(kHistorySize),
+      external_boolean_as_limit_(nullptr) {
+  ResetTimers(limit_in_seconds, deterministic_limit);
+}
+
 std::string TimeLimit::DebugString() const {
   std::string buffer = absl::StrCat(
       "Time left: ", (GetTimeLeft()),

ortools/util/time_limit.h

@@ -462,14 +462,26 @@ class NestedTimeLimit {
   TimeLimit time_limit_;
 };
 
-// ################## Implementations below #####################
+class TimeLimitCheckEveryNCalls {
+ public:
+  TimeLimitCheckEveryNCalls(int N, TimeLimit* time_limit)
+      : time_limit_(time_limit), count_(0), frequency_(N) {}
 
-inline TimeLimit::TimeLimit(double limit_in_seconds, double deterministic_limit)
-    : safety_buffer_ns_(static_cast<int64_t>(kSafetyBufferSeconds * 1e9)),
-      running_max_(kHistorySize),
-      external_boolean_as_limit_(nullptr) {
-  ResetTimers(limit_in_seconds, deterministic_limit);
-}
+  bool LimitReached() {
+    if (count_++ == frequency_) {
+      if (time_limit_->LimitReached()) return true;
+      count_ = 0;
+    }
+    return false;
+  }
+
+ private:
+  TimeLimit* time_limit_;
+  int count_;
+  const int frequency_;
+};
+
+// ################## Implementations below #####################
 
 inline void TimeLimit::ResetTimers(double limit_in_seconds,
                                    double deterministic_limit) {