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100% accurate PV display

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This gives SF accurate PVs, such that the evaluation of the leaf node in
the PV matches the score backed up to the root (99% of the time.
q-search will use the value stored in the hash table instead of the eval
value sometimes).

One drawback is that fail-high/low only get a minimal 2 move PV.

It doesn't add any additional overhead to the non-PV codepath except an
extra eight bytes to the SearchStack structure in multi-threaded
searches.

A core part of this is not pruning based on TT score in PV nodes. This
was measured as not being a regression at multiple TCs, except for one
exception, fast TC with huge hash, which is not realistic for longer
searches.

STC - 1 thread, 128 mb hash
ELO: 1.42 +-3.1 (95%) LOS: 81.9%
Total: 20000 W: 4078 L: 3996 D: 11926

STC - 3 thread, 128 mb hash
ELO: -3.60 +-2.9 (95%) LOS: 0.8%
Total: 20000 W: 3575 L: 3782 D: 12643

STC - 3 thread, 8 mb hash
ELO: 0.12 +-2.9 (95%) LOS: 53.3%
Total: 20000 W: 3654 L: 3647 D: 12699

LTC - 3 thread, 32mb hash
ELO: 2.29 +-2.0 (95%) LOS: 98.8%
Total: 35740 W: 5618 L: 5382 D: 24740

Bench: 6984058

Resolves #102
This commit is contained in:
Gary Linscott
2014-11-12 16:13:55 -05:00
parent 234344500f
commit 4739037f96
4 changed files with 56 additions and 60 deletions
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4
src/thread.h
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@@ -63,7 +63,7 @@ struct SplitPoint {
// Const data after split point has been setup
const Position* pos;
const Search::Stack* ss;
Search::Stack* ss;
Thread* masterThread;
Depth depth;
Value beta;
@@ -117,7 +117,7 @@ struct Thread : public ThreadBase {
bool cutoff_occurred() const;
bool available_to(const Thread* master) const;
void split(Position& pos, const Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];