From: Vizvezdenec <Vizvezdenec@gmail.com>
Date: Wed, 15 Apr 2020 01:13:50 +0000 (+0300)
Subject: Space bonus and number of blocked pawns
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=ca4e399ea6d88f8f71c8fd692566223496b10f78;hp=5c58f6712667076babe9ebaac1689436721c42be

Space bonus and number of blocked pawns

This patch refines the recently introduced interaction between
the space bonus and the number of blocked pawns in a position.

* pawns count as blocked also if their push square is attacked by 2 enemy pawns;
* overall dependence is stronger as well as offset;
* bonus increase is capped at 9 blocked pawns in position;

passed STC
https://tests.stockfishchess.org/tests/view/5e94560663d105aebbab243d
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 29500 W: 5842 L: 5603 D: 18055
Ptnml(0-2): 504, 3443, 6677, 3562, 564

passed LTC
https://tests.stockfishchess.org/tests/view/5e95b383c2aaa99f75d1a14d
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 63504 W: 8329 L: 7974 D: 47201
Ptnml(0-2): 492, 5848, 18720, 6197, 495

closes https://github.com/official-stockfish/Stockfish/pull/2631

bench 4956028
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index cd535d88..8feedfeb 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -695,7 +695,7 @@ namespace {
     behind |= shift<Down+Down>(behind);
 
     int bonus = popcount(safe) + popcount(behind & safe & ~attackedBy[Them][ALL_PIECES]);
-    int weight = pos.count<ALL_PIECES>(Us) - 2 + pe->blocked_count() / 2;
+    int weight = pos.count<ALL_PIECES>(Us) - 3 + std::min(pe->blocked_count(), 9);
     Score score = make_score(bonus * weight * weight / 16, 0);
 
     if (T)
diff --git a/src/pawns.cpp b/src/pawns.cpp
index a2063a8f..75e6ad7a 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -106,7 +106,7 @@ namespace {
         phalanx    = neighbours & rank_bb(s);
         support    = neighbours & rank_bb(s - Up);
 
-        e->blockedCount[Us] += bool(blocked);
+        e->blockedCount[Us] += blocked || more_than_one(leverPush);
 
         // A pawn is backward when it is behind all pawns of the same color on
         // the adjacent files and cannot safely advance.