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In qsearch store the cut move in TT

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And upon reentering the same position try it as first.

Normally qsearch moves order is already very good, first move
is the cut off in almost 90% of cases. With this patch, we get
a cut off on TT move of 98%.

Another good side effect is that we don't generate captures
and/or checks when we already have a TT move.

Unfortunatly we found a TT move only in 1% of cases. So real
impact of this patch is relatively low.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-04-18 14:03:33 +01:00
parent 4634be8ba6
commit e68ebe618c
3 changed files with 14 additions and 25 deletions
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27
src/movepick.cpp
View file

@ -50,7 +50,6 @@ namespace {
}
////
//// Functions
////
@ -445,9 +444,9 @@ Move MovePicker::pick_move_from_list() {
bestIndex = (movesPicked < 4 ? find_best_index() : movesPicked);
move = moves[bestIndex].move;
moves[bestIndex] = moves[movesPicked++];
// Remember to change the line below if we decide to hash the qsearch!
// Maybe also postpone the legality check until after futility pruning?
if (/* move != ttMove && */ pos.pl_move_is_legal(move, pinned))
// Maybe postpone the legality check until after futility pruning?
if ( move != ttMove
&& pos.pl_move_is_legal(move, pinned))
return move;
}
break;
@ -460,8 +459,8 @@ Move MovePicker::pick_move_from_list() {
while (movesPicked < numOfMoves)
{
move = moves[movesPicked++].move;
// Remember to change the line below if we decide to hash the qsearch!
if (/* move != ttMove && */ pos.pl_move_is_legal(move, pinned))
if ( move != ttMove
&& pos.pl_move_is_legal(move, pinned))
return move;
}
break;
@ -473,20 +472,10 @@ Move MovePicker::pick_move_from_list() {
}
/// MovePicker::current_move_type() returns the type of the just
/// picked next move. It can be used in search to further differentiate
/// according to the current move type: capture, non capture, escape, etc.
MovePicker::MovegenPhase MovePicker::current_move_type() const {
return PhaseTable[phaseIndex];
}
/// MovePicker::init_phase_table() initializes the PhaseTable[],
/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
/// QsearchNoCapturesPhaseIndex, QsearchWithoutChecksPhaseIndex and
/// NoMovesPhaseIndex variables. It is only called once during program
/// startup, and never again while the program is running.
/// and QsearchWithoutChecksPhaseIndex. It is only called once during
/// program startup, and never again while the program is running.
void MovePicker::init_phase_table() {
@ -511,12 +500,14 @@ void MovePicker::init_phase_table() {
// Quiescence search with checks
QsearchWithChecksPhaseIndex = i - 1;
PhaseTable[i++] = PH_TT_MOVE;
PhaseTable[i++] = PH_QCAPTURES;
PhaseTable[i++] = PH_QCHECKS;
PhaseTable[i++] = PH_STOP;
// Quiescence search without checks
QsearchWithoutChecksPhaseIndex = i - 1;
PhaseTable[i++] = PH_TT_MOVE;
PhaseTable[i++] = PH_QCAPTURES;
PhaseTable[i++] = PH_STOP;

1
src/movepick.h
View file

@ -70,7 +70,6 @@ public:
Move get_next_move(Lock &lock);
int number_of_moves() const;
int current_move_score() const;
MovegenPhase current_move_type() const;
Bitboard discovered_check_candidates() const;
static void init_phase_table();

11
src/search.cpp
View file

@ -1516,6 +1516,7 @@ namespace {
return value_from_tt(tte->value(), ply);
}
}
Move ttMove = (tte ? tte->move() : MOVE_NONE);
// Evaluate the position statically
EvalInfo ei;
@ -1559,7 +1560,7 @@ namespace {
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth == 0) will be generated.
MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth);
MovePicker mp = MovePicker(pos, pvNode, ttMove, EmptySearchStack, depth);
Move move;
int moveCount = 0;
Bitboard dcCandidates = mp.discovered_check_candidates();
@ -1636,22 +1637,20 @@ namespace {
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// Update transposition table
Move m = ss[ply].pv[ply];
if (!pvNode)
{
Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
if (bestValue < beta)
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER);
else
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_LOWER);
TT.store(pos, value_to_tt(bestValue, ply), d, m, VALUE_TYPE_LOWER);
}
// Update killers only for good check moves
Move m = ss[ply].currentMove;
if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
{
// Wrong to update history when depth is <= 0
update_killers(m, ss[ply]);
}
return bestValue;
}