czwartek, 22 czerwca 2017

Stockfish 17062122 - nowa kompilacja!

Stockfish, silnik szachowy UCI

Lider listy JCER = 3372
馃敩 Autor: Joost VandeVondele

Wi臋cej:
Timestamp: 1498077478 

Fix four data races. 

the nodes, tbHits, rootDepth and lastInfoTime variables are read by multiple threads, but not declared atomic, leading to data races as found by -fsanitize=thread. This patch fixes this issue. It is based on top of the CI-threading branch (PR #1129), and should fix the corresponding CI error messages. 

The patch passed an STC check for no regression: 

http://tests.stockfishchess.org/tests/view/5925d5590ebc59035df34b9f 
LLR: 2.96 (-2.94,2.94) [-3.00,1.00] 
Total: 169597 W: 29938 L: 30066 D: 109593 

Whereas rootDepth and lastInfoTime are not performance critical, nodes and tbHits are. Indeed, an earlier version using relaxed atomic updates on the latter two variables failed STC testing (http://tests.stockfishchess.org/tests/view/592001700ebc59035df34924), which can be shown to be due to x86-32 (http://tests.stockfishchess.org/tests/view/592330ac0ebc59035df34a89). Indeed, the latter have no instruction to atomically update a 64bit variable. The proposed solution thus uses a variable in Position that is accessed only by one thread, which is copied every few thousand nodes to the shared variable in Thread. 

No functional change. 

Closes #1130 
Closes #1129 

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