kate/BadFish
1
0
Fork 0
mirror of https://github.com/sockspls/badfish synced 2025-05-01 01:03:09 +00:00
Code Issues Releases Wiki Activity

Merge Joona Kiiski NULL search beta correction

Browse source 
Prune more moves after a null search because of
a lower beta limit then in main search.

In test positions reduces the searched nodes of 30% !!!!

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-03-13 15:26:02 +01:00
parent 3ed603cd64
commit c8773c720a
3 changed files with 35 additions and 20 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
src/evaluate.cpp
View file

@ -289,7 +289,6 @@ namespace {
void evaluate_space(const Position &p, Color us, EvalInfo &ei);
inline Value apply_weight(Value v, int w);
Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
int count_1s_8bit(Bitboard b);
@ -528,6 +527,22 @@ void read_weights(Color us) {
}
/// scale_by_game_phase() interpolates between a middle game and an endgame
/// score, based on game phase. It also scales the return value by a
/// ScaleFactor array.
Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
return Value(int(result) & ~(GrainSize - 1));
}
namespace {
// evaluate_common() computes terms common to all pieces attack
@ -1144,23 +1159,6 @@ namespace {
}
// scale_by_game_phase() interpolates between a middle game and an endgame
// score, based on game phase. It also scales the return value by a
// ScaleFactor array.
Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
return Value(int(result) & ~(GrainSize - 1));
}
// count_1s_8bit() counts the number of nonzero bits in the 8 least
// significant bits of a Bitboard. This function is used by the king
// shield evaluation.

1
src/evaluate.h
View file

@ -105,6 +105,7 @@ extern Value quick_evaluate(const Position &pos);
extern void init_eval(int threads);
extern void quit_eval();
extern void read_weights(Color sideToMove);
extern Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
#endif // !defined(EVALUATE_H_INCLUDED)

20
src/search.cpp
View file

@ -152,6 +152,16 @@ namespace {
// evaluation of the position is more than NullMoveMargin below beta.
const Value NullMoveMargin = Value(0x300);
//Null move search refutes move when Nullvalue >= Beta - Delta. Index is depth
//in full plies. Last index is 9+.
const Value NullMoveDeltaMidgame[] =
{ Value(-8), Value( 6), Value(-15), Value( 9), Value(21),
Value(34), Value(54), Value( 59), Value(61), Value(61) };
const Value NullMoveDeltaEndgame[] =
{ Value( 6), Value( 0), Value(-13), Value(-9), Value(-35),
Value(12), Value(24), Value( 9), Value( 5), Value( 5) };
// Pruning criterions. See the code and comments in ok_to_prune() to
// understand their precise meaning.
const bool PruneEscapeMoves = false;
@ -1202,13 +1212,19 @@ namespace {
&& ok_to_do_nullmove(pos)
&& approximateEval >= beta - NullMoveMargin)
{
//Calculate correct delta. Idea and tuning from Joona Kiiski.
ScaleFactor factor[2] = { SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL };
Phase phase = pos.game_phase();
int i = Min(depth / OnePly, 9);
Value delta = scale_by_game_phase(NullMoveDeltaMidgame[i], NullMoveDeltaEndgame[i], phase, factor);
ss[ply].currentMove = MOVE_NULL;
StateInfo st;
pos.do_null_move(st);
int R = (depth >= 4 * OnePly ? 4 : 3); // Null move dynamic reduction
Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
Value nullValue = -search(pos, ss, -(beta-delta-1), depth-R*OnePly, ply+1, false, threadID);
// Check for a null capture artifact, if the value without the null capture
// is above beta then mark the node as a suspicious failed low. We will verify
@ -1229,7 +1245,7 @@ namespace {
{
/* Do not return unproven mates */
}
else if (nullValue >= beta)
else if (nullValue >= beta - delta)
{
if (depth < 6 * OnePly)
return beta;