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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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15
src/Makefile
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@@ -50,7 +50,9 @@ OBJS = benchmark.o bitbase.o bitboard.o endgame.o evaluate.o main.o \
# ----------------------------------------------------------------------------
#
# debug = yes/no --- -DNDEBUG --- Enable/Disable debug mode
# sanitize = yes/no --- (-fsanitize ) --- enable undefined behavior checks
# sanitize = undefined/thread/no (-fsanitize )
# --- ( undefined ) --- enable undefined behavior checks
# --- ( thread ) --- enable threading error checks
# optimize = yes/no --- (-O3/-fast etc.) --- Enable/Disable optimizations
# arch = (name) --- (-arch) --- Target architecture
# bits = 64/32 --- -DIS_64BIT --- 64-/32-bit operating system
@@ -202,6 +204,9 @@ ifeq ($(COMP),clang)
comp=clang
CXX=clang++
CXXFLAGS += -pedantic -Wextra -Wshadow
ifneq ($(KERNEL),Darwin)
LDFLAGS += -latomic
endif
ifeq ($(ARCH),armv7)
ifeq ($(OS),Android)
@@ -261,9 +266,9 @@ else
endif
### 3.2.2 Debugging with undefined behavior sanitizers
ifeq ($(sanitize),yes)
CXXFLAGS += -g3 -fsanitize=undefined
LDFLAGS += -fsanitize=undefined
ifneq ($(sanitize),no)
CXXFLAGS += -g3 -fsanitize=$(sanitize) -fuse-ld=gold
LDFLAGS += -fsanitize=$(sanitize) -fuse-ld=gold
endif
### 3.3 Optimization
@@ -496,7 +501,7 @@ config-sanity:
@echo "Testing config sanity. If this fails, try 'make help' ..."
@echo ""
@test "$(debug)" = "yes" || test "$(debug)" = "no"
@test "$(sanitize)" = "yes" || test "$(sanitize)" = "no"
@test "$(sanitize)" = "undefined" || test "$(sanitize)" = "thread" || test "$(sanitize)" = "no"
@test "$(optimize)" = "yes" || test "$(optimize)" = "no"
@test "$(arch)" = "any" || test "$(arch)" = "x86_64" || test "$(arch)" = "i386" || \
test "$(arch)" = "ppc64" || test "$(arch)" = "ppc" || test "$(arch)" = "armv7"