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ai: Fix #100: Update alpha when searching 

When MTD(f) is disabled, played 1000 games, Win Rate:

New Vs. Old
25.7% : 17.1% : 57.2%

Old Vs. New
12.9% : 28.3% : 58.8%

When MTD(f) is enabled, played 250 games, Win Rate:

New Vs. Old
28.4% : 14.8% : 56.8%

Old Vs. New
10.8% : 32.0% : 57.2%
This commit is contained in:
Calcitem 2021-09-08 20:55:33 +08:00
parent 77b65d2cde
commit 6a7173211b
No known key found for this signature in database
GPG Key ID: F2F7C29E054CFB80
1 changed files with 14 additions and 4 deletions
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18
src/search.cpp
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@ -244,6 +244,8 @@ Value qsearch(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth or
Move ttMove = MOVE_NONE;
#endif // TT_MOVE_ENABLE
// Transposition table lookup
#if defined (TRANSPOSITION_TABLE_ENABLE) || defined(ENDGAME_LEARNING)
const Key posKey = pos->key();
#endif
@ -275,7 +277,7 @@ Value qsearch(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth or
// check transposition-table
const Value oldAlpha = alpha;
const Value oldAlpha = alpha; // To flag BOUND_EXACT when eval above alpha and no available moves
Bound type = BOUND_NONE;
@ -331,8 +333,8 @@ Value qsearch(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth or
}
#endif // THREEFOLD_REPETITION
// recurse
// Initialize a MovePicker object for the current position, and prepare
// to search the moves.
MovePicker mp(*pos);
Move nextMove = mp.next_move();
const int moveCount = mp.move_count();
@ -369,10 +371,13 @@ Value qsearch(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth or
#endif // !DISABLE_PREFETCH
#endif // TRANSPOSITION_TABLE_ENABLE
// Loop through the moves until no moves remain or a beta cutoff occurs
for (int i = 0; i < moveCount; i++) {
ss.push(*(pos));
const Color before = pos->sideToMove;
Move move = mp.moves[i].move;
// Make and search the move
pos->do_move(move);
const Color after = pos->sideToMove;
@ -435,7 +440,12 @@ Value qsearch(Position *pos, Sanmill::Stack<Position> &ss, Depth depth, Depth or
bestMove = move;
}
break;
if (value < beta) // Update alpha! Always alpha < beta
alpha = value;
else {
assert(value >= beta); // Fail high
break; // Fail high
}
}
}
}