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Simplify failedLow away #1986

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FailedLow doesn't seem to add any value so remove it.

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 43915 W: 9682 L: 9604 D: 24629
http://tests.stockfishchess.org/tests/view/5c5339770ebc592fc7baef74

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 58515 W: 9670 L: 9609 D: 39236
http://tests.stockfishchess.org/tests/view/5c53cc840ebc592fc7baf6c1

Ideas for further work:

    Tune the values in the revised fallingEval calculation
    Consider adding a term using delta, e.g. c * (delta - 20) as an indicator of eval instability

Bench: 3318033
This commit is contained in:
xoto10 2019-02-01 20:02:03 +00:00 • committed by Marco Costalba
parent 4d0981fef3
commit acc47e8b79
1 changed files with 5 additions and 7 deletions
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12
src/search.cpp
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@ -297,7 +297,6 @@ void Thread::search() {
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
double timeReduction = 1.0;
Color us = rootPos.side_to_move();
bool failedLow;
std::memset(ss-7, 0, 10 * sizeof(Stack));
for (int i = 7; i > 0; i--)
@ -308,7 +307,7 @@ void Thread::search() {
beta = VALUE_INFINITE;
if (mainThread)
mainThread->bestMoveChanges = 0, failedLow = false;
mainThread->bestMoveChanges = 0;
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
@ -349,7 +348,7 @@ void Thread::search() {
// Age out PV variability metric
if (mainThread)
mainThread->bestMoveChanges *= 0.517, failedLow = false;
mainThread->bestMoveChanges *= 0.517;
// Save the last iteration's scores before first PV line is searched and
// all the move scores except the (new) PV are set to -VALUE_INFINITE.
@ -429,7 +428,6 @@ void Thread::search() {
if (mainThread)
{
failedHighCnt = 0;
failedLow = true;
mainThread->stopOnPonderhit = false;
}
}
@ -481,19 +479,19 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0;
double fallingEval = (306 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
fallingEval = std::max(0.5, std::min(1.5, fallingEval));
// If the bestMove is stable over several iterations, reduce time accordingly
timeReduction = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0;
double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
// Use part of the gained time from a previous stable move for the current move
double bestMoveInstability = 1.0 + mainThread->bestMoveChanges;
bestMoveInstability *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
// Stop the search if we have only one legal move, or if available time elapsed
if ( rootMoves.size() == 1
|| Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval)
|| Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability)
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".