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Fix flaky StreamPoolTest.ConcurrentThreadsGetDistinctStreams #23820

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rapids-bot merged 1 commit into from
Aug 26, 2026
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Fix flaky StreamPoolTest.ConcurrentThreadsGetDistinctStreams #23820

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7 changes: 5 additions & 2 deletions cpp/tests/utilities_tests/stream_pool_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,9 +40,12 @@ TEST_F(StreamPoolTest, ConcurrentThreadsGetDistinctStreams)
auto constexpr num_streams = 8;

// Repeated requests make a shared round-robin counter very likely to hand the same stream to both
// threads. The latch makes them overlap; a thread starting after the other exited would adopt its
// retired pool and see the same streams.
// threads. Each thread takes its pool before the latch: a pool is created on first use and
// returned to the free list when its thread exits, so a thread that made its first request after
// the other one exited would adopt the retired pool and see the same streams.
auto collect = [](std::unordered_set<cudaStream_t>& out, std::latch& ready) {
auto const first = get_hashable_streams(num_streams);
out.insert(first.begin(), first.end());
ready.arrive_and_wait();
for (auto request = 0; request < num_requests; request++) {
auto const streams = get_hashable_streams(num_streams);
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