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Fix mated-in behaviour

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This addresses the issue where Stockfish may output non-proven checkmate
scores if the search is prematurely halted, either due to a time control
or node limit, before it explores other possibilities where the
checkmate score could have been delayed or refuted.

The fix also replaces staving off from proven mated scores in a
multithread environment making use of the threads instead of a negative
effect with multithreads (1t was better in proving mated in scores than
more threads).

Issue reported on mate tracker repo by and this PR is co-authored with
@robertnurnberg Special thanks to @AndyGrant for outlining that a fix is
eventually possible.

Passed Adj off SMP STC:
https://tests.stockfishchess.org/tests/view/65a125d779aa8af82b96c3eb
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 303256 W: 75823 L: 75892 D: 151541
Ptnml(0-2): 406, 35269, 80395, 35104, 454

Passed Adj off SMP LTC:
https://tests.stockfishchess.org/tests/view/65a37add79aa8af82b96f0f7
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 56056 W: 13951 L: 13770 D: 28335
Ptnml(0-2): 11, 5910, 16002, 6097, 8

Passed all tests in matetrack without any better mate for opponent found in 1t and multithreads.

Fixed bugs in https://github.com/official-stockfish/Stockfish/pull/4976

closes https://github.com/official-stockfish/Stockfish/pull/4990

Bench: 1308279

Co-Authored-By: Robert Nürnberg <28635489+robertnurnberg@users.noreply.github.com>
This commit is contained in:
Shahin M. Shahin
2024-01-08 10:31:23 +03:00
committed by Disservin
parent f15e4f50aa
commit 0c7f56dea6
5 changed files with 69 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
src/thread.cpp
View File

@@ -20,8 +20,6 @@
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <deque>
#include <memory>
#include <unordered_map>
@@ -169,8 +167,8 @@ void ThreadPool::start_thinking(const OptionsMap& options,
main_thread()->wait_for_search_finished();
main_manager()->stopOnPonderhit = stop = false;
main_manager()->ponder = ponderMode;
main_manager()->stopOnPonderhit = stop = abortedSearch = false;
main_manager()->ponder = ponderMode;
increaseDepth = true;
@@ -229,13 +227,23 @@ Thread* ThreadPool::get_best_thread() const {
votes[th->worker->rootMoves[0].pv[0]] += thread_value(th);
for (Thread* th : threads)
if (std::abs(bestThread->worker->rootMoves[0].score) >= VALUE_TB_WIN_IN_MAX_PLY)
if (bestThread->worker->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY)
{
// Make sure we pick the shortest mate / TB conversion or stave off mate the longest
// Make sure we pick the shortest mate / TB conversion
if (th->worker->rootMoves[0].score > bestThread->worker->rootMoves[0].score)
bestThread = th;
}
else if (bestThread->worker->rootMoves[0].score != -VALUE_INFINITE
&& bestThread->worker->rootMoves[0].score <= VALUE_TB_LOSS_IN_MAX_PLY)
{
// Make sure we pick the shortest mated / TB conversion
if (th->worker->rootMoves[0].score != -VALUE_INFINITE
&& th->worker->rootMoves[0].score < bestThread->worker->rootMoves[0].score)
bestThread = th;
}
else if (th->worker->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY
|| (th->worker->rootMoves[0].score != -VALUE_INFINITE
&& th->worker->rootMoves[0].score <= VALUE_TB_LOSS_IN_MAX_PLY)
|| (th->worker->rootMoves[0].score > VALUE_TB_LOSS_IN_MAX_PLY
&& (votes[th->worker->rootMoves[0].pv[0]]
> votes[bestThread->worker->rootMoves[0].pv[0]]