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Rewrok the extendeable patch

Browse source 
Cleanup and document.

The real functional change is that not mate threat
moves are never pruned, as could happen before.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2008-11-25 14:49:38 +01:00
parent eba8925d81
commit c3ba5fb9d3
1 changed files with 35 additions and 46 deletions
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77
src/search.cpp
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@ -245,7 +245,7 @@ namespace {
void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
bool connected_moves(const Position &pos, Move m1, Move m2);
bool move_is_killer(Move m, const SearchStack& ss);
Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* extendable);
Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* dangerous);
bool ok_to_do_nullmove(const Position &pos);
bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
@ -778,8 +778,8 @@ namespace {
<< " currmovenumber " << i + 1 << std::endl;
// Decide search depth for this move
bool dummy;
ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dummy);
bool dangerous;
ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dangerous);
newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
// Make the move, and search it
@ -953,8 +953,7 @@ namespace {
Value value, bestValue = -VALUE_INFINITE;
Bitboard dcCandidates = mp.discovered_check_candidates();
bool isCheck = pos.is_check();
bool mateThreat = MateThreatExtension[1] > Depth(0)
&& pos.has_mate_threat(opposite_color(pos.side_to_move()));
bool mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
@ -967,7 +966,6 @@ namespace {
bool singleReply = (isCheck && mp.number_of_moves() == 1);
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
movesSearched[moveCount++] = ss[ply].currentMove = move;
@ -979,8 +977,8 @@ namespace {
ss[ply].currentMoveCaptureValue = Value(0);
// Decide the new search depth
bool extendable;
Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &extendable);
bool dangerous;
Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &dangerous);
Depth newDepth = depth - OnePly + ext;
// Make and search the move
@ -994,11 +992,10 @@ namespace {
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
if ( depth >= 2*OnePly
&& !extendable
&& moveCount >= LMRPVMoves
&& !dangerous
&& !moveIsCapture
&& !move_promotion(move)
&& !moveIsPassedPawnPush
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
@ -1222,20 +1219,18 @@ namespace {
bool singleReply = (isCheck && mp.number_of_moves() == 1);
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
movesSearched[moveCount++] = ss[ply].currentMove = move;
// Decide the new search depth
bool extendable;
Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &extendable);
bool dangerous;
Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &dangerous);
Depth newDepth = depth - OnePly + ext;
// Futility pruning
if ( useFutilityPruning
&& !extendable
&& !dangerous
&& !moveIsCapture
&& !moveIsPassedPawnPush
&& !move_promotion(move))
{
if ( moveCount >= 2 + int(depth)
@ -1264,11 +1259,10 @@ namespace {
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
if ( depth >= 2*OnePly
&& !extendable
&& moveCount >= LMRNonPVMoves
&& !dangerous
&& !moveIsCapture
&& !move_promotion(move)
&& !moveIsPassedPawnPush
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
@ -1401,20 +1395,17 @@ namespace {
{
assert(move_is_ok(move));
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
moveCount++;
ss[ply].currentMove = move;
// Futility pruning
if ( UseQSearchFutilityPruning
&& enoughMaterial
&& !isCheck
&& !moveIsCheck
&& !move_promotion(move)
&& !moveIsPassedPawnPush
&& !pvNode
&& enoughMaterial)
&& !move_promotion(move)
&& !pos.move_is_check(move, dcCandidates)
&& !pos.move_is_passed_pawn_push(move))
{
Value futilityValue = staticValue
+ Max(pos.midgame_value_of_piece_on(move_to(move)),
@ -1509,7 +1500,6 @@ namespace {
bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
lock_grab(&(sp->lock));
int moveCount = ++sp->moves;
@ -1518,15 +1508,14 @@ namespace {
ss[sp->ply].currentMove = move;
// Decide the new search depth.
bool extendable;
Depth ext = extension(pos, move, false, moveIsCheck, false, false, &extendable);
bool dangerous;
Depth ext = extension(pos, move, false, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
// Prune?
if ( useFutilityPruning
&& !extendable
&& !dangerous
&& !moveIsCapture
&& !moveIsPassedPawnPush
&& !move_promotion(move)
&& moveCount >= 2 + int(sp->depth)
&& ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
@ -1538,10 +1527,9 @@ namespace {
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
if ( !extendable
if ( !dangerous
&& moveCount >= LMRNonPVMoves
&& !moveIsCapture
&& !moveIsPassedPawnPush
&& !move_promotion(move)
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
@ -1622,7 +1610,6 @@ namespace {
{
bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
assert(move_is_ok(move));
@ -1636,8 +1623,8 @@ namespace {
ss[sp->ply].currentMove = move;
// Decide the new search depth.
bool extendable;
Depth ext = extension(pos, move, true, moveIsCheck, false, false, &extendable);
bool dangerous;
Depth ext = extension(pos, move, true, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
// Make and search the move.
@ -1646,10 +1633,9 @@ namespace {
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
if ( !extendable
if ( !dangerous
&& moveCount >= LMRPVMoves
&& !moveIsCapture
&& !moveIsPassedPawnPush
&& !move_promotion(move)
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
@ -2053,13 +2039,16 @@ namespace {
// extension() decides whether a move should be searched with normal depth,
// or with extended depth. Certain classes of moves (checking moves, in
// particular) are searched with bigger depth than ordinary moves.
// particular) are searched with bigger depth than ordinary moves and in
// any case are marked as 'dangerous'. Note that also if a move is not
// extended, as example because the corresponding UCI option is set to zero,
// the move is marked as 'dangerous' so, at least, we avoid to prune it.
Depth extension(const Position &pos, Move m, bool pvNode,
bool check, bool singleReply, bool mateThreat, bool* extendable) {
Depth extension(const Position &pos, Move m, bool pvNode, bool check,
bool singleReply, bool mateThreat, bool* dangerous) {
Depth result = Depth(0);
*extendable = check || singleReply || mateThreat;
*dangerous = check || singleReply || mateThreat;
if (check)
result += CheckExtension[pvNode];
@ -2073,12 +2062,12 @@ namespace {
if (pos.move_is_pawn_push_to_7th(m))
{
result += PawnPushTo7thExtension[pvNode];
*extendable = true;
*dangerous = true;
}
if (pos.move_is_passed_pawn_push(m))
{
result += PassedPawnExtension[pvNode];
*extendable = true;
*dangerous = true;
}
if ( pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame
@ -2087,7 +2076,7 @@ namespace {
&& !move_promotion(m))
{
result += PawnEndgameExtension[pvNode];
*extendable = true;
*dangerous = true;
}
if ( pvNode
@ -2096,7 +2085,7 @@ namespace {
&& pos.see(m) >= 0)
{
result += OnePly/2;
*extendable = true;
*dangerous = true;
}
return Min(result, OnePly);