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More work in probe_dtz_no_ep()

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This commit is contained in:
Marco Costalba 2016-05-21 10:16:56 +02:00
parent bea98066a0
commit 47e21c274d
1 changed files with 42 additions and 54 deletions
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96
src/syzygy/tbprobe.cpp
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@ -1282,8 +1282,6 @@ int probe_dtz(Position& pos, ProbeState* result);
// This routine treats a position with en passant captures as one without. // This routine treats a position with en passant captures as one without.
int probe_dtz_no_ep(Position& pos, ProbeState* result) int probe_dtz_no_ep(Position& pos, ProbeState* result)
{ {
int dtz;
WDLScore wdl = search<true>(pos, WDLLoss, WDLWin, result); WDLScore wdl = search<true>(pos, WDLLoss, WDLWin, result);
if (*result == FAIL) if (*result == FAIL)
@ -1296,7 +1294,7 @@ int probe_dtz_no_ep(Position& pos, ProbeState* result)
|| *result == WIN_PAWN_MOVE) || *result == WIN_PAWN_MOVE)
return wdl == WDLWin ? 1 : 101; // DTZ scores for immediate win or cursed win return wdl == WDLWin ? 1 : 101; // DTZ scores for immediate win or cursed win
dtz = 1 + probe_dtz_table(pos, wdl, result); // Probe the table! int dtz = 1 + probe_dtz_table(pos, wdl, result); // Probe the table!
if (*result != CHANGE_STM) if (*result != CHANGE_STM)
{ {
@ -1306,71 +1304,61 @@ int probe_dtz_no_ep(Position& pos, ProbeState* result)
return wdl > WDLDraw ? dtz : -dtz; return wdl > WDLDraw ? dtz : -dtz;
} }
ExtMove stack[MAX_MOVES]; // DTZ stores results for the other STM, so we need to do a 1-ply search.
ExtMove *moves, *end = nullptr; // Because of the structure of the dtz values, it is easier to distinguish
// between wdl > 0 and wdl < 0.
StateInfo st; StateInfo st;
CheckInfo ci(pos); CheckInfo ci(pos);
int minDTZ = 0xFFFF;
if (wdl > 0) { if (wdl > 0)
int best = 0xffff; {
// Find the winning move that minimizes DTZ. We don't need to probe for
for (moves = stack; moves < end; ++moves) { // captures and pawn moves because we already know are losing.
Move move = moves->move; for (const Move& move : MoveList<LEGAL>(pos))
{
if (pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN if (pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN)
|| !pos.legal(move, ci.pinned))
continue; continue;
pos.do_move(move, st, pos.gives_check(move, ci)); pos.do_move(move, st, pos.gives_check(move, ci));
int v = -probe_dtz(pos, result); dtz = -probe_dtz(pos, result);
pos.undo_move(move); pos.undo_move(move);
if (*result == FAIL) if (*result == FAIL)
return 0; return 0;
if (v > 0 && v + 1 < best) if (dtz > 0 && dtz + 1 < minDTZ)
best = v + 1; minDTZ = dtz + 1;
} }
return best; return minDTZ;
} else {
int best = -1;
if (!pos.checkers())
end = generate<NON_EVASIONS>(pos, stack);
else
end = generate<EVASIONS>(pos, stack);
for (moves = stack; moves < end; ++moves) {
int v;
Move move = moves->move;
if (!pos.legal(move, ci.pinned))
continue;
pos.do_move(move, st, pos.gives_check(move, ci));
if (st.rule50 == 0) {
if (wdl == -2) v = -1;
else {
v = search(pos, WDLCursedWin, WDLWin, result);
v = (v == 2) ? 0 : -101;
}
} else {
v = -probe_dtz(pos, result) - 1;
}
pos.undo_move(move);
if (*result == FAIL)
return 0;
if (v < best)
best = v;
}
return best;
} }
// Find the losing move that maximizes DTZ. Of course, all moves will
// return a negative dtz value because the position is known to lose.
for (const Move& move : MoveList<LEGAL>(pos))
{
pos.do_move(move, st, pos.gives_check(move, ci));
if (st.rule50 > 0) // Not a capture or pawn move
dtz = -probe_dtz(pos, result) - 1;
else if (wdl == WDLLoss)
dtz = -1;
else
dtz = search(pos, WDLCursedWin, WDLWin, result) == WDLWin ? 0 : -101;
pos.undo_move(move);
if (*result == FAIL)
return 0;
if (dtz < minDTZ)
minDTZ = dtz;
}
return minDTZ;
} }
// Probe the DTZ table for a particular position. // Probe the DTZ table for a particular position.