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Code Issues Releases Wiki Activity

Integrate ENPASSANT in the search

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This commit is contained in:
Marco Costalba 2016-05-20 18:35:10 +02:00
parent 9a0f8b38c3
commit 6eb670ad37
2 changed files with 21 additions and 77 deletions
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94
src/syzygy/tbprobe.cpp
View file

@ -1212,15 +1212,17 @@ int probe_dtz_table(const Position& pos, WDLScore wdl, int* success)
// probes is the correct result for the position. // probes is the correct result for the position.
WDLScore search(Position& pos, WDLScore alpha, WDLScore beta, int *success) WDLScore search(Position& pos, WDLScore alpha, WDLScore beta, int *success)
{ {
WDLScore value; WDLScore value, epValue = WDLScoreNone;
StateInfo st; StateInfo st;
CheckInfo ci(pos); CheckInfo ci(pos);
// Search caputures first accessing smaller tb tables, that potentially are // Search caputures first accessing smaller tb tables, that potentially are
// easier to be RAM cached. // easier to be RAM cached.
for (const Move& move : MoveList<LEGAL>(pos)) auto moveList = MoveList<LEGAL>(pos);
size_t moveCount = moveList.size();
for (const Move& move : moveList)
{ {
if (!pos.capture(move) || type_of(move) == ENPASSANT) if (!pos.capture(move))
continue; continue;
pos.do_move(move, st, pos.gives_check(move, ci)); pos.do_move(move, st, pos.gives_check(move, ci));
@ -1230,6 +1232,9 @@ WDLScore search(Position& pos, WDLScore alpha, WDLScore beta, int *success)
if (*success == 0) if (*success == 0)
return WDLDraw; return WDLDraw;
if (type_of(move) == ENPASSANT)
epValue = value;
if (value >= beta) if (value >= beta)
return *success = 2, value; return *success = 2, value;
@ -1243,10 +1248,17 @@ WDLScore search(Position& pos, WDLScore alpha, WDLScore beta, int *success)
if (*success == 0) if (*success == 0)
return WDLDraw; return WDLDraw;
if (alpha >= value) // The tables do not contain information on position with ep rights, so in
return *success = 1 + (alpha > WDLDraw), alpha; // this case probe_wdl_table could be wrong. In particular could be higher
// then epValue and if epValue is the only move then we are forced to play
// the losing ep capture.
if (epValue != WDLScoreNone && (moveCount == 1))
value = epValue;
if (value > alpha)
return *success = 1, value; return *success = 1, value;
return *success = 1 + (alpha > WDLDraw), alpha;
} }
int probe_dtz(Position& pos, int *success); int probe_dtz(Position& pos, int *success);
@ -1629,77 +1641,7 @@ void Tablebases::init(const std::string& paths)
WDLScore Tablebases::probe_wdl(Position& pos, int *success) WDLScore Tablebases::probe_wdl(Position& pos, int *success)
{ {
*success = 1; *success = 1;
WDLScore v = search(pos, WDLLoss, WDLWin, success); return search(pos, WDLLoss, WDLWin, success);
// If en passant is not possible, we are done.
if (pos.ep_square() == SQ_NONE)
return v;
if (*success == 0)
return WDLDraw;
// Now handle en passant.
WDLScore v1 = WDLScore(-3); // FIXME use a proper enum value here
// Generate (at least) all legal en passant captures.
ExtMove stack[MAX_MOVES];
ExtMove *moves, *end;
StateInfo st;
if (!pos.checkers())
end = generate<CAPTURES>(pos, stack);
else
end = generate<EVASIONS>(pos, stack);
CheckInfo ci(pos);
for (moves = stack; moves < end; ++moves) {
Move capture = moves->move;
if (type_of(capture) != ENPASSANT
|| !pos.legal(capture, ci.pinned))
continue;
pos.do_move(capture, st, pos.gives_check(capture, ci));
WDLScore v0 = -search(pos, WDLLoss, WDLWin, success);
pos.undo_move(capture);
if (*success == 0)
return WDLDraw;
if (v0 > v1) v1 = v0;
}
if (v1 > -3) {
if (v1 >= v) v = v1;
else if (v == 0) {
// Check whether there is at least one legal non-ep move.
for (moves = stack; moves < end; ++moves) {
Move capture = moves->move;
if (type_of(capture) == ENPASSANT) continue;
if (pos.legal(capture, ci.pinned))
break;
}
if (moves == end && !pos.checkers()) {
end = generate<QUIETS>(pos, end);
for (; moves < end; ++moves) {
Move move = moves->move;
if (pos.legal(move, ci.pinned))
break;
}
}
// If not, then we are forced to play the losing ep capture.
if (moves == end)
v = v1;
}
}
return v;
} }
// Check whether there has been at least one repetition of positions // Check whether there has been at least one repetition of positions

2
src/syzygy/tbprobe.h
View file

@ -30,6 +30,8 @@ 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
}; };
extern size_t MaxCardinality; extern size_t MaxCardinality;