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https://github.com/sockspls/badfish
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Remove ep specific code from dtz probe
This commit is contained in:
Marco Costalba
parent
47e21c274d
commit
0b040243ba
1 changed files with 44 additions and 140 deletions
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@ -1277,10 +1277,32 @@ WDLScore search(Position& pos, WDLScore alpha, WDLScore beta, ProbeState* result
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return alpha;
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return alpha;
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}
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}
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int probe_dtz(Position& pos, ProbeState* result);
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// Probe the DTZ table for a particular position.
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// If *result != FAIL, the probe was successful.
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// This routine treats a position with en passant captures as one without.
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// The return value is from the point of view of the side to move:
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int probe_dtz_no_ep(Position& pos, ProbeState* result)
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// n < -100 : loss, but draw under 50-move rule
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// -100 <= n < -1 : loss in n ply (assuming 50-move counter == 0)
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// 0 : draw
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// 1 < n <= 100 : win in n ply (assuming 50-move counter == 0)
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// 100 < n : win, but draw under 50-move rule
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//
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// The return value n can be off by 1: a return value -n can mean a loss
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// in n+1 ply and a return value +n can mean a win in n+1 ply. This
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// cannot happen for tables with positions exactly on the "edge" of
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// the 50-move rule.
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//
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// This implies that if dtz > 0 is returned, the position is certainly
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// a win if dtz + 50-move-counter <= 99. Care must be taken that the engine
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// picks moves that preserve dtz + 50-move-counter <= 99.
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//
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// If n = 100 immediately after a capture or pawn move, then the position
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// is also certainly a win, and during the whole phase until the next
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// capture or pawn move, the inequality to be preserved is
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// dtz + 50-movecounter <= 100.
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//
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// In short, if a move is available resulting in dtz + 50-move-counter <= 99,
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// then do not accept moves leading to dtz + 50-move-counter == 100.
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int probe_dtz(Position& pos, ProbeState* result)
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{
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{
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WDLScore wdl = search<true>(pos, WDLLoss, WDLWin, result);
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WDLScore wdl = search<true>(pos, WDLLoss, WDLWin, result);
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@ -1312,7 +1334,6 @@ int probe_dtz_no_ep(Position& pos, ProbeState* result)
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int minDTZ = 0xFFFF;
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int minDTZ = 0xFFFF;
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if (wdl > 0)
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if (wdl > 0)
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{
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// Find the winning move that minimizes DTZ. We don't need to probe for
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// Find the winning move that minimizes DTZ. We don't need to probe for
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// captures and pawn moves because we already know are losing.
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// captures and pawn moves because we already know are losing.
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for (const Move& move : MoveList<LEGAL>(pos))
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for (const Move& move : MoveList<LEGAL>(pos))
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@ -1330,10 +1351,7 @@ int probe_dtz_no_ep(Position& pos, ProbeState* result)
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if (dtz > 0 && dtz + 1 < minDTZ)
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if (dtz > 0 && dtz + 1 < minDTZ)
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minDTZ = dtz + 1;
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minDTZ = dtz + 1;
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}
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}
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else
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return minDTZ;
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}
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// Find the losing move that maximizes DTZ. Of course, all moves will
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// Find the losing move that maximizes DTZ. Of course, all moves will
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// return a negative dtz value because the position is known to lose.
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// return a negative dtz value because the position is known to lose.
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for (const Move& move : MoveList<LEGAL>(pos))
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for (const Move& move : MoveList<LEGAL>(pos))
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@ -1361,120 +1379,6 @@ int probe_dtz_no_ep(Position& pos, ProbeState* result)
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return minDTZ;
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return minDTZ;
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}
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}
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// Probe the DTZ table for a particular position.
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// If *result != FAIL, the probe was successful.
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// The return value is from the point of view of the side to move:
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// n < -100 : loss, but draw under 50-move rule
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// -100 <= n < -1 : loss in n ply (assuming 50-move counter == 0)
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// 0 : draw
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// 1 < n <= 100 : win in n ply (assuming 50-move counter == 0)
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// 100 < n : win, but draw under 50-move rule
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//
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// The return value n can be off by 1: a return value -n can mean a loss
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// in n+1 ply and a return value +n can mean a win in n+1 ply. This
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// cannot happen for tables with positions exactly on the "edge" of
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// the 50-move rule.
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//
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// This implies that if dtz > 0 is returned, the position is certainly
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// a win if dtz + 50-move-counter <= 99. Care must be taken that the engine
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// picks moves that preserve dtz + 50-move-counter <= 99.
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//
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// If n = 100 immediately after a capture or pawn move, then the position
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// is also certainly a win, and during the whole phase until the next
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// capture or pawn move, the inequality to be preserved is
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// dtz + 50-movecounter <= 100.
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//
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// In short, if a move is available resulting in dtz + 50-move-counter <= 99,
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// then do not accept moves leading to dtz + 50-move-counter == 100.
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//
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int probe_dtz(Position& pos, ProbeState *result)
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{
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*result = OK;
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int v = probe_dtz_no_ep(pos, result);
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if (pos.ep_square() == SQ_NONE)
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return v;
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if (*result == FAIL)
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return 0;
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// Now handle en passant.
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int v1 = -3;
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ExtMove stack[MAX_MOVES];
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ExtMove *moves, *end;
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StateInfo st;
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if (!pos.checkers())
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end = generate<CAPTURES>(pos, stack);
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else
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end = generate<EVASIONS>(pos, stack);
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CheckInfo ci(pos);
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for (moves = stack; moves < end; ++moves) {
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Move capture = moves->move;
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if (type_of(capture) != ENPASSANT
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|| !pos.legal(capture, ci.pinned))
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continue;
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pos.do_move(capture, st, pos.gives_check(capture, ci));
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WDLScore v0 = -search(pos, WDLLoss, WDLWin, result);
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pos.undo_move(capture);
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if (*result == 0)
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return 0;
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if (v0 > v1) v1 = v0;
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}
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if (v1 > -3) {
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v1 = wdl_to_dtz[v1 + 2];
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if (v < -100) {
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if (v1 >= 0)
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v = v1;
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} else if (v < 0) {
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if (v1 >= 0 || v1 < -100)
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v = v1;
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} else if (v > 100) {
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if (v1 > 0)
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v = v1;
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} else if (v > 0) {
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if (v1 == 1)
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v = v1;
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} else if (v1 >= 0) {
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v = v1;
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} else {
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for (moves = stack; moves < end; ++moves) {
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Move move = moves->move;
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if (type_of(move) == ENPASSANT) continue;
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if (pos.legal(move, ci.pinned))
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break;
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}
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if (moves == end && !pos.checkers()) {
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end = generate<QUIETS>(pos, end);
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for (; moves < end; ++moves) {
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Move move = moves->move;
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if (pos.legal(move, ci.pinned))
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break;
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}
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}
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if (moves == end)
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v = v1;
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}
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}
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return v;
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}
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} // namespace
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} // namespace
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void Tablebases::init(const std::string& paths)
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void Tablebases::init(const std::string& paths)
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