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stockfish
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Use special null move technique in low depth. 

Try good captures before null move when depth < 3 * OnePly.
Use this kind of null move also in Depth == OnePly.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
sf_2.3.1_base
Joona Kiiski 2009-08-24 20:06:09 +03:00 committed by Marco Costalba
parent a5d699d62f
commit b088f0aefd
2 changed files with 5 additions and 2 deletions
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5
src/movepick.cpp
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@ -45,6 +45,7 @@ namespace {
CACHE_LINE_ALIGNMENT
const MovegenPhaseT MainSearchPhaseTable[] = { PH_STOP, PH_NULL_MOVE, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
const MovegenPhaseT MainSearchNoNullPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
const MovegenPhaseT LowSearchPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_NULL_MOVE, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
const MovegenPhaseT EvasionsPhaseTable[] = { PH_STOP, PH_EVASIONS, PH_STOP};
const MovegenPhaseT QsearchWithChecksPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
const MovegenPhaseT QsearchWithoutChecksPhaseTable[] = { PH_STOP, PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
@ -79,8 +80,10 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
if (p.is_check())
phasePtr = EvasionsPhaseTable;
else if (d > Depth(0))
else if (d >= Depth(3 * OnePly))
phasePtr = useNullMove ? MainSearchPhaseTable : MainSearchNoNullPhaseTable;
else if (d > Depth(0))
phasePtr = useNullMove ? LowSearchPhaseTable : MainSearchNoNullPhaseTable;
else if (d == Depth(0))
phasePtr = QsearchWithChecksPhaseTable;
else

2
src/search.cpp
View File

@ -1282,7 +1282,7 @@ namespace {
bool isCheck = pos.is_check();
bool useNullMove = ( allowNullmove
&& depth > OnePly
//&& depth > OnePly
&& !isCheck
&& !value_is_mate(beta)
&& ok_to_do_nullmove(pos)