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SE depth scaling using the previous depth

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This patch makes the SE depth condition more robust and allows it to scale with completed depth
from a previous search.

At long TC this patch is almost equivalent to https://github.com/official-stockfish/Stockfish/pull/4016 which had

VLTC:
https://tests.stockfishchess.org/tests/view/626abd7e8707aa698c0093a8
Elo: 2.35 +-1.5 (95%) LOS: 99.9%
Total: 40000 W: 10991 L: 10720 D: 18289
Ptnml(0-2): 8, 3534, 12648, 3799, 11
nElo: 5.47 +-3.4 (95%) PairsRatio: 1.08

VLTC multicore:
https://tests.stockfishchess.org/tests/view/6272a6afc8f14123163c1997
LLR: 2.94 (-2.94,2.94) <0.50,3.00>
Total: 86808 W: 24165 L: 23814 D: 38829
Ptnml(0-2): 11, 7253, 28524, 7606, 10

however, it is now also gaining at LTC:

LTC:
https://tests.stockfishchess.org/tests/view/627e7cb523c0c72a05b651a9
LLR: 2.94 (-2.94,2.94) <0.50,3.00>
Total: 27064 W: 7285 L: 7046 D: 12733
Ptnml(0-2): 8, 2446, 8390, 2675, 13

and should have nearly no influence at STC as depth 27 is rarely reached.
It was noticed that initializing the threshold with MAX_PLY, had an adverse effect,
possibly because the first move is sensitive to this.

closes https://github.com/official-stockfish/Stockfish/pull/4021
closes https://github.com/official-stockfish/Stockfish/pull/4016

Bench: 6481017
This commit is contained in:
disservin 2022-05-14 12:10:13 +02:00 • committed by Joost VandeVondele
parent c079acc26f
commit 5372f81cc8
4 changed files with 8 additions and 3 deletions
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1
AUTHORS
View file

@ -125,6 +125,7 @@ marotear
Matt Ginsberg (mattginsberg)
Matthew Lai (matthewlai)
Matthew Sullivan (Matt14916)
Max A. (Disservin)
Maxim Molchanov (Maxim)
Michael An (man)
Michael Byrne (MichaelB7)

5
src/search.cpp
View file

@ -238,6 +238,9 @@ void MainThread::search() {
bestPreviousScore = bestThread->rootMoves[0].score;
bestPreviousAverageScore = bestThread->rootMoves[0].averageScore;
for (Thread* th : Threads)
th->previousDepth = bestThread->completedDepth;
// Send again PV info if we have a new best thread
if (bestThread != this)
sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
@ -1061,7 +1064,7 @@ moves_loop: // When in check, search starts here
// a reduced search on all the other moves but the ttMove and if the
// result is lower than ttValue minus a margin, then we will extend the ttMove.
if ( !rootNode
&& depth >= 4 + 2 * (PvNode && tte->is_pv())
&& depth >= 4 - (thisThread->previousDepth > 27) + 2 * (PvNode && tte->is_pv())
&& move == ttMove
&& !excludedMove // Avoid recursive singular search
/* && ttValue != VALUE_NONE Already implicit in the next condition */

3
src/thread.cpp
View file

@ -60,7 +60,8 @@ void Thread::clear() {
counterMoves.fill(MOVE_NONE);
mainHistory.fill(0);
captureHistory.fill(0);
previousDepth = 0;
for (bool inCheck : { false, true })
for (StatsType c : { NoCaptures, Captures })
{

2
src/thread.h
View file

@ -69,7 +69,7 @@ public:
Position rootPos;
StateInfo rootState;
Search::RootMoves rootMoves;
Depth rootDepth, completedDepth, depth;
Depth rootDepth, completedDepth, depth, previousDepth;
Value rootDelta;
CounterMoveHistory counterMoves;
ButterflyHistory mainHistory;