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Use evaluation trend to adjust futility margin

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Adjust futility margin in the child node based on whether the
static evaluation is improving.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 15271 W: 3157 L: 2958 D: 9156
http://tests.stockfishchess.org/tests/view/5a9f2f8c0ebc590297cb6216

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 6617 W: 1053 L: 908 D: 4656
http://tests.stockfishchess.org/tests/view/5a9f98390ebc590297cb6241

Ideas for future work:

- Tune the new margins.
- Try to get this idea to work for futility pruning in parent
  nodes as well.

Bench: 5779242
This commit is contained in:
Jerry Donald Watson 2018-03-07 22:31:51 +01:00 • committed by Stéphane Nicolet
parent 6d8f583af2
commit 65c3bb8586
1 changed files with 8 additions and 2 deletions
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10
src/search.cpp
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@ -69,7 +69,9 @@ namespace {
// Razor and futility margins // Razor and futility margins
const int RazorMargin1 = 590; const int RazorMargin1 = 590;
const int RazorMargin2 = 604; const int RazorMargin2 = 604;
Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); } Value futility_margin(Depth d, bool improving) {
return Value((175 - 50 * improving) * d / ONE_PLY);
}
// Futility and reductions lookup tables, initialized at startup // Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth] int FutilityMoveCounts[2][16]; // [improving][depth]
@ -678,6 +680,10 @@ namespace {
ss->staticEval, TT.generation()); ss->staticEval, TT.generation());
} }
improving = ss->staticEval >= (ss-2)->staticEval
/* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */
||(ss-2)->staticEval == VALUE_NONE;
if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move())) if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move()))
goto moves_loop; goto moves_loop;
@ -702,7 +708,7 @@ namespace {
// Step 8. Futility pruning: child node (skipped when in check) // Step 8. Futility pruning: child node (skipped when in check)
if ( !rootNode if ( !rootNode
&& depth < 7 * ONE_PLY && depth < 7 * ONE_PLY
&& eval - futility_margin(depth) >= beta && eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins && eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval; return eval;