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Change reduction/improving interaction

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Adjust criterion for applying extra reduction if not improving.
We now add an extra ply of reduction if r > 1.0, instead of the
previous condition Reductions[NonPV][imp][d][mc] >= 2.

Why does this work? Previously, reductions when not improving had
a discontinuity as the depth and/or move count increases due to the
Reductions[NonPV][imp][d][mc] >= 2 condition. Hence, values of r
such that 0.5 < r < 1.5 would be mapped to a reduction of 1, while
1.5 < r < 2.5 would be mapped to a reduction of 3. This patch allows
values of r satisfying 1.0 < r < 1.5 to be mapped to a reduction of 2,
making the reduction formula more continuous.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 35908 W: 7382 L: 7087 D: 21439
http://tests.stockfishchess.org/tests/view/5aba723a0ebc5902a4743e8f

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 23087 W: 3584 L: 3378 D: 16125
http://tests.stockfishchess.org/tests/view/5aba89070ebc5902a4743ea9

Ideas for future work:
- We could look at retuning the LMR formula.
- We could look at adjusting the reductions in PV nodes if not improving.

Bench: 5326261
This commit is contained in:
Jerry Donald Watson 2018-03-28 00:31:31 +02:00 • committed by Stéphane Nicolet
parent 5ce630584c
commit 9953bfff62
2 changed files with 3 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/search.cpp
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@ -160,7 +160,7 @@ void Search::init() {
Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
// Increase reduction for non-PV nodes when eval is not improving
if (!imp && Reductions[NonPV][imp][d][mc] >= 2)
if (!imp && r > 1.0)
Reductions[NonPV][imp][d][mc]++;
}

3
src/timeman.h
View file

@ -33,7 +33,8 @@ public:
void init(Search::LimitsType& limits, Color us, int ply);
TimePoint optimum() const { return optimumTime; }
TimePoint maximum() const { return maximumTime; }
TimePoint elapsed() const { return int(Search::Limits.npmsec ? Threads.nodes_searched() : now() - startTime); }
TimePoint elapsed() const { return Search::Limits.npmsec ?
TimePoint(Threads.nodes_searched()) : now() - startTime; }
int64_t availableNodes; // When in 'nodes as time' mode