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Fix four data races.

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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
This commit is contained in:
Joost VandeVondele
2017-06-21 13:36:53 -07:00
committed by Joona Kiiski
parent 2c237da546
commit 3cb0200459
7 changed files with 78 additions and 17 deletions
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.travis.yml
+2 -1
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@@ -72,4 +72,5 @@ script:
# sanitizer
#
# use g++-6 as a proxy for having sanitizers, might need revision as they become available for more recent versions of clang/gcc
- if [[ "$COMPILER" == "g++-6" ]]; then make clean && make ARCH=x86-64 sanitize=yes build > /dev/null && ../tests/instrumented.sh --sanitizer; fi
- if [[ "$COMPILER" == "g++-6" ]]; then make clean && make ARCH=x86-64 sanitize=undefined optimize=no debug=yes build > /dev/null && ../tests/instrumented.sh --sanitizer-undefined; fi
- if [[ "$COMPILER" == "g++-6" ]]; then make clean && make ARCH=x86-64 sanitize=thread optimize=no debug=yes build > /dev/null && ../tests/instrumented.sh --sanitizer-thread; fi