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Further improve probe_dtz()

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This commit is contained in:
Marco Costalba 2016-05-21 10:50:04 +02:00
parent 0b040243ba
commit 0700912dc5
1 changed files with 26 additions and 36 deletions
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62
src/syzygy/tbprobe.cpp
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@ -1326,55 +1326,45 @@ int probe_dtz(Position& pos, ProbeState* result)
return wdl > WDLDraw ? dtz : -dtz;
}
// DTZ stores results for the other STM, so we need to do a 1-ply search.
// Because of the structure of the dtz values, it is easier to distinguish
// between wdl > 0 and wdl < 0.
// DTZ stores results for the other STM, so we need to do a 1-ply search and
// find the winning move that minimizes DTZ.
StateInfo st;
CheckInfo ci(pos);
int minDTZ = 0xFFFF;
if (wdl > 0)
// Find the winning move that minimizes DTZ. We don't need to probe for
// captures and pawn moves because we already know are losing.
for (const Move& move : MoveList<LEGAL>(pos))
{
if (pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN)
continue;
for (const Move& move : MoveList<LEGAL>(pos))
{
// When winning, we don't need to probe for captures and pawn
// moves because we already know are losing.
if ( wdl > 0
&& (pos.capture(move) || type_of(pos.moved_piece(move)) == PAWN))
continue;
pos.do_move(move, st, pos.gives_check(move, ci));
pos.do_move(move, st, pos.gives_check(move, ci));
if (wdl > 0)
dtz = -probe_dtz(pos, result);
pos.undo_move(move);
if (*result == FAIL)
return 0;
else if (st.rule50 > 0) // Not a capture or pawn move
dtz = -probe_dtz(pos, result) - 1;
if (dtz > 0 && dtz + 1 < minDTZ)
minDTZ = dtz + 1;
}
else
// 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));
else if (wdl == WDLLoss)
dtz = -1;
if (st.rule50 > 0) // Not a capture or pawn move
dtz = -probe_dtz(pos, result) - 1;
else
dtz = search(pos, WDLCursedWin, WDLWin, result) == WDLWin ? 0 : -101;
else if (wdl == WDLLoss)
dtz = -1;
pos.undo_move(move);
else
dtz = search(pos, WDLCursedWin, WDLWin, result) == WDLWin ? 0 : -101;
if (*result == FAIL)
return 0;
pos.undo_move(move);
if (wdl > 0 && dtz > 0 && dtz + 1 < minDTZ)
minDTZ = dtz + 1;
if (*result == FAIL)
return 0;
if (dtz < minDTZ)
minDTZ = dtz;
}
else if (wdl < 0 && dtz < minDTZ)
minDTZ = dtz;
}
return minDTZ;
}