stat.cc crashes: stats.cc:201 Check failed: seconds >= 0.0 (-0.784035 vs. 0)

[alex-klimov]

What version of OR-Tools and what language are you using?
Version: main/v9.14
Language: C++/Go

Which solver are you using
CP-SAT

What operating system (Linux, Windows, ...) and version?
Ubuntu 24

What did you do?
Hard to reproduce, timing issue.

1. Solver configured with 4 workers, fails on rather large run, which takes up to a minute to finish. Sometimes solver crashes with:

    WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
    F0000 00:00:1762346483.864814 391862 stats.cc:201] Check failed: seconds >= 0.0 (-0.784035 vs. 0)
    *** Check failure stack trace: ***
    @ 0x155dc08 (unknown)
    @ 0x155dc84 (unknown)
    @ 0x155d70c (unknown)
    @ 0x6763ec (unknown)
    @ 0x10c69d0 (unknown)
    @ 0xd2e91c (unknown)
    @ 0xd2d02c (unknown)
    @ 0xd2e56c (unknown)
    @ 0xd2e32c (unknown)
    @ 0xd2de88 (unknown)
    @ 0x6ad270 (unknown)
    @ 0x1154ea8 (unknown)
    @ 0x1157738 (unknown)
    @ 0x11576bc (unknown)
    @ 0x1157620 (unknown)
    @ 0x11575d8 (unknown)
    @ 0x11575b8 (unknown)
    @ 0xf70426581ae0 (unknown)
    @ 0xf7042624595c (unknown)

2. Ubuntu adjusts the clock with ntpdate - likely this is important.

What did you expect to see
No crashes on timing issues.

Anything else we should know about your project / environment

Likely fix would be at ortools/sat/subsolver.h to check for duration to be positive:

  // Note that this is protected by the global execution mutex and so it is
  // called sequentially. Subclasses do not need to call this.
  void AddTaskDuration(double duration_in_seconds) {
    ++num_finished_tasks_;
    wall_time_ += duration_in_seconds;
    if (duration_in_seconds > 0) {
      timing_.AddTimeInSec(duration_in_seconds);
    }
  }

This follows the same pattern already used in that file for AddTaskDeterministicDuration

[lperron]

Thanks