Fix sometimes incorrect key for prefetches

mstembera · snicolet · commit 385deefd807b · 2021-10-25T12:26:44.000+02:00
STC https://tests.stockfishchess.org/tests/view/61737b4f6ce927be32558401 LLR: 2.95 (-2.94,2.94) <-2.50,0.50> Total: 138712 W: 34914 L: 34942 D: 68856 Ptnml(0-2): 421, 14817, 38894, 14817, 407 Very minor tweak since Position::key() depends on the 50 move rule counter. Comments: mstembera@cddde31 closes #3759 No functional change
diff --git a/src/position.cpp b/src/position.cpp
@@ -1013,9 +1013,9 @@ void Position::do_null_move(StateInfo& newSt) {
   }
 
   st->key ^= Zobrist::side;
+  ++st->rule50;
   prefetch(TT.first_entry(key()));
 
-  ++st->rule50;
   st->pliesFromNull = 0;
 
   sideToMove = ~sideToMove;

Original file line number	Diff line number	Diff line change
`@@ -1013,9 +1013,9 @@ void Position::do_null_move(StateInfo& newSt) {`
`1013`	`1013`	`}`
`1014`	`1014`
`1015`	`1015`	`st->key ^= Zobrist::side;`
	`1016`	`+ ++st->rule50;`
`1016`	`1017`	`prefetch(TT.first_entry(key()));`
`1017`	`1018`
`1018`		`- ++st->rule50;`
`1019`	`1019`	`st->pliesFromNull = 0;`
`1020`	`1020`
`1021`	`1021`	`sideToMove = ~sideToMove;`