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Simplify pondering time management (#1899)

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stopOnPonderhit is used to stop search quickly on a ponderhit. It is set by mainThread as part of its time management. However, master employs it as a signal between mainThread and the UCI thread. This is not necessary, it is sufficient for the UCI thread to signal that pondering finished, and mainThread should do its usual time-keeping job, and in this case stop immediately.

This patch implements this, removing stopOnPonderHit as an atomic variable from the ThreadPool,
and moving it as a normal variable to mainThread, reducing its scope. In MainThread::check_time() the search is stopped immediately if ponder switches to false, and the variable stopOnPonderHit is set.

Furthermore, ponder has been moved to mainThread, as the variable is only used to exchange signals between the UCI thread and mainThread.

The version has been tested locally (as fishtest doesn't support ponder):

Score of ponderSimp vs master: 2616 - 2528 - 8630 [0.503] 13774
Elo difference: 2.22 +/- 3.54

which indicates no regression.

No functional change.
This commit is contained in:
Joost VandeVondele
2019-01-20 19:14:24 +01:00
committed by Marco Costalba
parent 59b2486bc3
commit 58d3ee6175
4 changed files with 19 additions and 20 deletions
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17
src/search.cpp
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@@ -227,10 +227,9 @@ void MainThread::search() {
// Threads.stop. However, if we are pondering or in an infinite search,
// the UCI protocol states that we shouldn't print the best move before the
// GUI sends a "stop" or "ponderhit" command. We therefore simply wait here
// until the GUI sends one of those commands (which also raises Threads.stop).
Threads.stopOnPonderhit = true;
// until the GUI sends one of those commands.
while (!Threads.stop && (Threads.ponder || Limits.infinite))
while (!Threads.stop && (ponder || Limits.infinite))
{} // Busy wait for a stop or a ponder reset
// Stop the threads if not already stopped (also raise the stop if
@@ -448,7 +447,7 @@ void Thread::search() {
{
failedHighCnt = 0;
failedLow = true;
Threads.stopOnPonderhit = false;
mainThread->stopOnPonderhit = false;
}
}
else if (bestValue >= beta)
@@ -497,7 +496,7 @@ void Thread::search() {
// Do we have time for the next iteration? Can we stop searching now?
if ( Limits.use_time_management()
&& !Threads.stop
&& !Threads.stopOnPonderhit)
&& !mainThread->stopOnPonderhit)
{
double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0;
fallingEval = std::max(0.5, std::min(1.5, fallingEval));
@@ -515,8 +514,8 @@ void Thread::search() {
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".
if (Threads.ponder)
Threads.stopOnPonderhit = true;
if (mainThread->ponder)
mainThread->stopOnPonderhit = true;
else
Threads.stop = true;
}
@@ -1595,10 +1594,10 @@ void MainThread::check_time() {
}
// We should not stop pondering until told so by the GUI
if (Threads.ponder)
if (ponder)
return;
if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10)
if ( (Limits.use_time_management() && (elapsed > Time.maximum() - 10 || stopOnPonderhit))
|| (Limits.movetime && elapsed >= Limits.movetime)
|| (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
Threads.stop = true;