Simplify kingRing

Simplify the king ring initialization and make it more regular, by just
moving the king square off the edges and using PseudoAttacks by king from
this new square.

There is a small functional difference from the previous master, as the
old master excludes the original ksq square while this patch always includes
the nine squares block (after moving the king from the edges). Additionally,
master does not adjust the kingRing down if we are on relative rank 8,
while this patch treats all of the edges the same.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 13263 W: 2968 L: 2830 D: 7465
http://tests.stockfishchess.org/tests/view/5db872830ebc5902d1f388aa

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 72996 W: 11819 L: 11780 D: 49397
http://tests.stockfishchess.org/tests/view/5db899c20ebc5902d1f38b5e

Closes https://github.com/official-stockfish/Stockfish/pull/2384

Bench: 4959244

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index c1640d945d0d115bca1355da9cbcb57896f5e9e3..959ccd8431cfba2e96cdf98ccfed8f1119c8cc62 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -235,15 +235,9 @@ namespace {
     attackedBy2[Us] = dblAttackByPawn | (attackedBy[Us][KING] & attackedBy[Us][PAWN]);
 
     // Init our king safety tables
     attackedBy2[Us] = dblAttackByPawn | (attackedBy[Us][KING] & attackedBy[Us][PAWN]);
 
     // Init our king safety tables

-    kingRing[Us] = attackedBy[Us][KING];
-    if (relative_rank(Us, ksq) == RANK_1)
-        kingRing[Us] |= shift<Up>(kingRing[Us]);
-
-    if (file_of(ksq) == FILE_H)
-        kingRing[Us] |= shift<WEST>(kingRing[Us]);
-
-    else if (file_of(ksq) == FILE_A)
-        kingRing[Us] |= shift<EAST>(kingRing[Us]);
+    Square s = make_square(clamp(file_of(ksq), FILE_B, FILE_G),
+                           clamp(rank_of(ksq), RANK_2, RANK_7));
+    kingRing[Us] = PseudoAttacks[KING][s] | s;

 
     kingAttackersCount[Them] = popcount(kingRing[Us] & pe->pawn_attacks(Them));
     kingAttacksCount[Them] = kingAttackersWeight[Them] = 0;
 
     kingAttackersCount[Them] = popcount(kingRing[Us] & pe->pawn_attacks(Them));
     kingAttacksCount[Them] = kingAttackersWeight[Them] = 0;