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Fix intermittent threaded loop executed in order test warning #44479

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merged 4 commits into from
Mar 7, 2022
Merged

Fix intermittent threaded loop executed in order test warning #44479

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83b6502
synchronize start of threaded loop test for robustness
IanButterworth Mar 6, 2022
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Apply suggestions from code review
IanButterworth Mar 6, 2022
f3c3dc3
simplify
IanButterworth Mar 6, 2022
406b6fa
Merge branch 'master' into ib/thread_test_robustness
IanButterworth Mar 6, 2022
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12 changes: 11 additions & 1 deletion test/threads_exec.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,17 @@ end

# parallel loop with parallel atomic addition
function threaded_loop(a, r, x)
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counter = Threads.Atomic{Int}(Threads.nthreads())
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@threads for i in r
# synchronize the start given that each partition is started sequentially,
# meaning that without the wait, if the loop is too fast the iteration can happen in order
if counter[] != 0
Threads.atomic_sub!(counter, 1)
while counter[] != 0
GC.safepoint()
ccall(:jl_cpu_pause, Cvoid, ())
end
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end
j = i - firstindex(r) + 1
a[j] = 1 + atomic_add!(x, 1)
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end
Expand All @@ -93,7 +103,7 @@ function test_threaded_loop_and_atomic_add()
# and were unique (via pigeon-hole principle).
@test !(false in found)
if was_inorder && nthreads() > 1
println(stderr, "Warning: threaded loop executed in order")
@warn "threaded loop executed in order" nthreads() r
end
end
end
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