From: ElbertoOne <lubvdberg@gmail.com>
Date: Sun, 31 May 2020 14:39:03 +0000 (+0200)
Subject: Isolated pawns tweak
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=8c3d9d996af7aa34f019785818eecbeb9338b95f;ds=sidebyside

Isolated pawns tweak

Give opposed doubled isolated pawns only the Doubled penalty.
The other isolated pawns get the Isolated penalty and the WeakUnopposed penalty.
The popcount condition has been replaced with an opposed check,
which is non-functional, but probably gives a speed-up.

Passed STC (https://tests.stockfishchess.org/tests/view/5ed0f0f0042fa6d77c3552f5):
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 121832 W: 23562 L: 23195 D: 75075
Ptnml(0-2): 2092, 14064, 28313, 14279, 2168

LTC: (https://tests.stockfishchess.org/tests/view/5ed22e40042fa6d77c355387)
LLR: 2.96 (-2.94,2.94) {0.25,1.75}
Total: 103368 W: 13232 L: 12768 D: 77368
Ptnml(0-2): 693, 9484, 30919, 9842, 746

closes https://github.com/official-stockfish/Stockfish/pull/2706

Bench: 4085694
---

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 467137b3..c1119a41 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -145,13 +145,13 @@ namespace {
 
         else if (!neighbours)
         {
-            score -=   Isolated
-                     + WeakUnopposed * !opposed;
-
-            if (   (ourPawns & forward_file_bb(Them, s))
-                && popcount(opposed) == 1
+            if (     opposed
+                &&  (ourPawns & forward_file_bb(Them, s))
                 && !(theirPawns & adjacent_files_bb(s)))
                 score -= Doubled;
+            else
+                score -=   Isolated
+                         + WeakUnopposed * !opposed;
         }
 
         else if (backward)