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Add doubled isolated pawn penalty.

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This patch gives an additional penalty if a doubled isolated pawn is stopped
only by a single opponent pawn on the same file. Thanks to NKONSTANTAKIS,
who shared this idea on the forum!

https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/vC4Qn-PMlS4.

STC:
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 84872 W: 16688 L: 16370 D: 51814
Ptnml(0-2): 1507, 9940, 19274, 10158, 1557
https://tests.stockfishchess.org/tests/view/5ec65bd955202b947dc5d4ac

LTC:
LLR: 2.93 (-2.94,2.94) {0.25,1.75}
Total: 58104 W: 7614 L: 7278 D: 43212
Ptnml(0-2): 411, 5369, 17196, 5625, 451
https://tests.stockfishchess.org/tests/view/5ec6e9f2c23f5b0710632b19

Closes https://github.com/official-stockfish/Stockfish/pull/2694

Bench: 5148950
This commit is contained in:
Stefan Geschwentner 2020-05-22 11:08:44 +02:00 • committed by Stéphane Nicolet
parent 09c6917d05
commit cdf5cfdb92
1 changed files with 14 additions and 6 deletions
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8
src/pawns.cpp
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@ -35,6 +35,7 @@ namespace {
constexpr Score Backward = S( 9, 24);
constexpr Score BlockedStorm = S(82, 82);
constexpr Score Doubled = S(11, 56);
constexpr Score DoubledIsolated = S(15, 57);
constexpr Score Isolated = S( 5, 15);
constexpr Score WeakLever = S( 0, 56);
constexpr Score WeakUnopposed = S(13, 27);
@ -144,9 +145,16 @@ namespace {
}
else if (!neighbours)
{
score -= Isolated
+ WeakUnopposed * !opposed;
if ( (ourPawns & forward_file_bb(Them, s))
&& popcount(opposed) == 1
&& !(theirPawns & adjacent_files_bb(s)))
score -= DoubledIsolated;
}
else if (backward)
score -= Backward
+ WeakUnopposed * !opposed;