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Fix tablebase probe for dtz >1000 w/o 50 move rule

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For qn4N1/6R1/3K4/8/B2k4/8/8/8 w - - 0 1, white loses with DTZ 1034.
See https://syzygy-tables.info/?fen=qn4N1/6R1/3K4/8/B2k4/8/8/8_w_-_-_0_1

Prior to this fix, due to a too small hard-coded value, Stockfish interpreted this as winning.
The new value picked (1<<18) is large enough to deal with the largest DTZ values that can be stored in the current syzygy format.

closes https://github.com/official-stockfish/Stockfish/pull/4187

No functional change.
This commit is contained in:
Rodrigo Roim 2022-10-07 16:55:07 -07:00 • committed by Joost VandeVondele
parent 9be2977da7
commit 79c5f3a692
3 changed files with 8 additions and 8 deletions
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1
AUTHORS
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@ -169,6 +169,7 @@ renouve
Reuven Peleg Reuven Peleg
Richard Lloyd Richard Lloyd
Rodrigo Exterckötter Tjäder Rodrigo Exterckötter Tjäder
Rodrigo Roim (roim)
Ron Britvich (Britvich) Ron Britvich (Britvich)
Ronald de Man (syzygy1, syzygy) Ronald de Man (syzygy1, syzygy)
rqs rqs

13
src/syzygy/tbprobe.cpp
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@ -59,6 +59,7 @@ namespace Stockfish {
namespace { namespace {
constexpr int TBPIECES = 7; // Max number of supported pieces constexpr int TBPIECES = 7; // Max number of supported pieces
constexpr int MAX_DTZ = 1 << 18; // Max DTZ supported, large enough to deal with the syzygy TB limit.
enum { BigEndian, LittleEndian }; enum { BigEndian, LittleEndian };
enum TBType { WDL, DTZ }; // Used as template parameter enum TBType { WDL, DTZ }; // Used as template parameter
@ -1522,7 +1523,7 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
// Check whether a position was repeated since the last zeroing move. // Check whether a position was repeated since the last zeroing move.
bool rep = pos.has_repeated(); bool rep = pos.has_repeated();
int dtz, bound = Options["Syzygy50MoveRule"] ? 900 : 1; int dtz, bound = Options["Syzygy50MoveRule"] ? (MAX_DTZ - 100) : 1;
// Probe and rank each move // Probe and rank each move
for (auto& m : rootMoves) for (auto& m : rootMoves)
@ -1565,8 +1566,8 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
// Better moves are ranked higher. Certain wins are ranked equally. // Better moves are ranked higher. Certain wins are ranked equally.
// Losing moves are ranked equally unless a 50-move draw is in sight. // Losing moves are ranked equally unless a 50-move draw is in sight.
int r = dtz > 0 ? (dtz + cnt50 <= 99 && !rep ? 1000 : 1000 - (dtz + cnt50)) int r = dtz > 0 ? (dtz + cnt50 <= 99 && !rep ? MAX_DTZ : MAX_DTZ - (dtz + cnt50))
: dtz < 0 ? (-dtz * 2 + cnt50 < 100 ? -1000 : -1000 + (-dtz + cnt50)) : dtz < 0 ? (-dtz * 2 + cnt50 < 100 ? -MAX_DTZ : -MAX_DTZ + (-dtz + cnt50))
: 0; : 0;
m.tbRank = r; m.tbRank = r;
@ -1574,9 +1575,9 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
// 1 cp to cursed wins and let it grow to 49 cp as the positions gets // 1 cp to cursed wins and let it grow to 49 cp as the positions gets
// closer to a real win. // closer to a real win.
m.tbScore = r >= bound ? VALUE_MATE - MAX_PLY - 1 m.tbScore = r >= bound ? VALUE_MATE - MAX_PLY - 1
: r > 0 ? Value((std::max( 3, r - 800) * int(PawnValueEg)) / 200) : r > 0 ? Value((std::max( 3, r - (MAX_DTZ - 200)) * int(PawnValueEg)) / 200)
: r == 0 ? VALUE_DRAW : r == 0 ? VALUE_DRAW
: r > -bound ? Value((std::min(-3, r + 800) * int(PawnValueEg)) / 200) : r > -bound ? Value((std::min(-3, r + (MAX_DTZ - 200)) * int(PawnValueEg)) / 200)
: -VALUE_MATE + MAX_PLY + 1; : -VALUE_MATE + MAX_PLY + 1;
} }
@ -1590,7 +1591,7 @@ bool Tablebases::root_probe(Position& pos, Search::RootMoves& rootMoves) {
// A return value false indicates that not all probes were successful. // A return value false indicates that not all probes were successful.
bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves) { bool Tablebases::root_probe_wdl(Position& pos, Search::RootMoves& rootMoves) {
static const int WDL_to_rank[] = { -1000, -899, 0, 899, 1000 }; static const int WDL_to_rank[] = { -MAX_DTZ, -MAX_DTZ + 101, 0, MAX_DTZ - 101, MAX_DTZ };
ProbeState result; ProbeState result;
StateInfo st; StateInfo st;

2
src/syzygy/tbprobe.h
View file

@ -31,8 +31,6 @@ enum WDLScore {
WDLDraw = 0, // Draw WDLDraw = 0, // Draw
WDLCursedWin = 1, // Win, but draw under 50-move rule WDLCursedWin = 1, // Win, but draw under 50-move rule
WDLWin = 2, // Win WDLWin = 2, // Win
WDLScoreNone = -1000
}; };
// Possible states after a probing operation // Possible states after a probing operation