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CuckooChess: Don't do reverse futility pruning if there is too little material left.

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This commit is contained in:
Peter Osterlund 2011-12-04 13:02:37 +00:00
parent e547c780c9
commit c53f582581
3 changed files with 27 additions and 13 deletions
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2
CuckooChessEngine/src/chess/ComputerPlayer.java
View File

@ -30,7 +30,7 @@ public class ComputerPlayer implements Player {
public static final String engineName;
static {
String name = "CuckooChess 1.13a6";
String name = "CuckooChess 1.13a7";
String m = System.getProperty("sun.arch.data.model");
if ("32".equals(m))
name += " 32-bit";

26
CuckooChessEngine/src/chess/Search.java
View File

@ -554,8 +554,15 @@ public class Search {
}
// Reverse futility pruning
if (!inCheck && (depth < 5*plyScale) && (posExtend == 0)) {
if ((Math.abs(alpha) <= MATE0 / 2) && (Math.abs(beta) <= MATE0 / 2)) {
if (!inCheck && (depth < 5*plyScale) && (posExtend == 0) &&
(Math.abs(alpha) <= MATE0 / 2) && (Math.abs(beta) <= MATE0 / 2)) {
boolean mtrlOk;
if (pos.whiteMove) {
mtrlOk = (pos.wMtrl > pos.wMtrlPawns) && (pos.wMtrlPawns > 0);
} else {
mtrlOk = (pos.bMtrl > pos.bMtrlPawns) && (pos.bMtrlPawns > 0);
}
if (mtrlOk) {
int margin;
if (depth <= plyScale) margin = 204;
else if (depth <= 2*plyScale) margin = 420;
@ -615,9 +622,7 @@ public class Search {
if ((searchTreeInfo[ply-1].lmr > 0) && (depth < 5*plyScale)) {
Move m1 = searchTreeInfo[ply-1].currentMove;
Move m2 = searchTreeInfo[ply+1].bestMove; // threat move
if (m1.from != m1.to) {
if ((m1.to == m2.from) || (m1.from == m2.to) ||
((BitBoard.squaresBetween[m2.from][m2.to] & (1L << m1.from)) != 0)) {
if (relatedMoves(m1, m2)) {
// if the threat move was made possible by a reduced
// move on the previous ply, the reduction was unsafe.
// Return alpha to trigger a non-reduced re-search.
@ -628,7 +633,6 @@ public class Search {
}
}
}
}
boolean futilityPrune = false;
int futilityScore = alpha;
@ -844,6 +848,16 @@ public class Search {
return bestScore;
}
/** Return true if move m2 was made possible by move m1. */
private final boolean relatedMoves(Move m1, Move m2) {
if ((m1.from == m1.to) || (m2.from == m2.to))
return false;
if ((m1.to == m2.from) || (m1.from == m2.to) ||
((BitBoard.squaresBetween[m2.from][m2.to] & (1L << m1.from)) != 0))
return true;
return false;
}
/** Return true if move should be skipped in order to make engine play weaker. */
private final boolean weakPlaySkipMove(Position pos, Move m, int ply) {
long rndL = pos.zobristHash() ^ Position.psHashKeys[0][m.from] ^

2
CuckooChessEngine/test/chess/SearchTest.java
View File

@ -83,7 +83,7 @@ public class SearchTest {
sc = new Search(pos, nullHist, 0, tt);
score = sc.negaScout(-mate0, mate0, 0, 3*plyScale, -1, MoveGen.inCheck(pos));
assertTrue(Math.abs(score) < 50); // Stale-mate trap
score2 = idSearch(sc, 9).score;
score2 = idSearch(sc, 5).score;
assertEquals(score, score2);
pos = TextIO.readFEN("8/8/2K5/3QP3/P6P/1q6/8/k7 w - - 31 51");