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[OMNIML-6178] [1/11] Run the unit tests in parallel with pytest-xdist - #2845
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Check name Status Explanation Title check The title clearly and concisely describes the main change: running unit tests in parallel with pytest-xdist. The issue identifier and series marker do not obscure the change. Linked Issues check Check skipped because no linked issues were found for this pull request. Out of Scope Changes check Check skipped because no linked issues were found for this pull request. Security Anti-Patterns PASS. The pull request changes no Python files under modelopt/orexamples/. Added Python lines contain none of the prohibited security patterns, and no dependency manifests changed.Description Check Check skipped - CodeRabbit’s high-level summary is enabled.
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This was referenced Oct 17, 2026
[OMNIML-6179] [5/11] Make the ONNX tests cheaper: CPU-only ones to the unit lane, small models
#2849
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #2845 +/- ##
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+ Coverage 76.90% 78.94% +2.04%
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Files 658 658
Lines 74023 74023
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+ Misses 17099 15588 -1511
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Review comments at @tests/unit/torch/speculative/plugins/test_hf_dflash2.py:
- Line 352: Move test_overfits_a_single_batch out of tests/unit into the
appropriate slower GPU test suite, preserving its 60-step training workload and
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LGTM: this small, well-measured CI change runs the unit tests in parallel with the existing pytest-xdist dependency, and the test fixes it needs are justified. A human needs to sign off on the edits to existing tests.
Needs action:
- Confirm the existing-test edits as a human.
test_search_constraintsnow usesmonkeypatchso its patch doesn't leak into later tests.test_overfits_a_single_batchgets a 300 s timeout. The unit timeout intests/conftest.pygoes from 60 s to 120 s on every platform. No assertions were loosened.
No action needed:
- Design check: nothing new is built.
pytest-xdistis already indev-test, and the parallel options are set through the standardPYTEST_ADDOPTSvariable. noxfile.pyclearsPYTEST_ADDOPTSfor themanualrun, so those tests stay serial. Nox'senv=overrides the variable as intended.- Turning
TEST_MODELSfrom a set into a tuple fixes test IDs that differed between workers, which xdist needs. - The Windows and partial-install jobs don't set
PYTEST_ADDOPTS, so they still run serially.
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The unit workflow's `linux` job gates every GPU and example workflow: their pr-gate jobs wait for it (poseidon/wait-for-status-checks, `^linux$`). That wait is a median 13.8 min, 23% of a PR's GPU run, and the job itself takes a median 14.8 min. The tests are CPU-bound and run serially, so use the runner's four vCPUs. - unit_tests.yml: `PYTEST_ADDOPTS=-n 4 --dist loadfile` on the `linux` job and the multi-version matrix. One worker per vCPU (`-n auto` counts physical cores), whole files per worker, and `OMP_NUM_THREADS=1`: with torch's default threads per worker the runner is oversubscribed and the run is slower than serial (1,481 s and 41 failures in my local runs). - noxfile.py: the second pytest process that runs the `manual` tests clears PYTEST_ADDOPTS, so it stays serial: those tests leak global state into each other, and a worker would run them in some order. - tests/_test_utils/torch/quantization/onnx_export.py: TEST_MODELS was a set of classes, whose iteration order differs between processes, so xdist workers collected different test ids. Use a tuple. - test_hf_dflash2.py: test_overfits_a_single_batch needs more than the default 60 s call timeout when one thread runs it (about 53 s with torch's default threads). Give it 300 s. pytest-xdist is already in the dev-test extra on main (#2771); uv.lock is refreshed by the weekly bump_uv_lock workflow. Testing: the full tests/unit suite, on 4 CPUs with coverage as in CI, on the base before the unit-test cleanup of #2823. Serial 825 s; this configuration 332-344 s in three repeated runs (4,724 passed, 0 failed). The other matrix entries (Python 3.10, 3.13, 3.14, torch 2.8, transformers min) take 4.5-5.3 min. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
test_search_constraints replaced ConstraintsFunc._get_true_latency with a fake by plain assignment and never put the original back, so the fake stayed in place for the rest of the process. test_evaluate_constraints.py::test_evaluate_latency_constraints and ::test_percent_limits use the real method through a fake runtime client (latency 100 and 200) and fail when they run after it: the leaked fake returns 280.5 for the tiny resnet, so the 20% latency limit comes out as 56.1 instead of 40, and a 200 limit is not met. Serial runs never saw it, because test_evaluate_constraints.py sorts before test_full_algorithms_vision.py. With pytest-xdist (-n 4 --dist loadfile), added by the previous commit, a worker can get the files in the other order: in the Python 3.10 and 3.14 legs of a CI run, the same worker ran test_search_constraints and then the two victims, which failed; in the legs where they landed on different workers, or in the other order, they passed. Use monkeypatch, so the patch is undone after the test. Testing: running test_search_constraints[False-True] and then test_evaluate_constraints.py in one process failed both tests with the CI values before the change (56.10 against 40.0, and assert False is True) and passes after it, and ConstraintsFunc._get_true_latency is the original function again afterwards. tests/unit (without puzzletron, which needs hydra) in reversed and in shuffled file order shows no other leak of this kind. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
tests/unit/torch/quantization/test_dist.py::test_data_parallel hit the 60 s default cap in the Python 3.12 / torch 2.13 leg of a CI run with pytest-xdist. The test spawns two processes and takes 8-15 s in serial runs. With pytest-xdist it takes 25-35 s in every other leg, and 60 s or more on the slowest runner: four workers and the child processes of the multi-process tests (test_dist, the three test_*data_parallel* autoquant tests, the tests that share cpu_dist_workers) share the four vCPUs of a CI runner. A hung test is still reported, after 2 min instead of 1. Windows already had 120 s. Testing: the durations above come from the job logs of that CI run and of the serial run before it. Not re-run on a runner: the cap only adds headroom. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
…erged test_overfits_a_single_batch took about 53 s on one thread, which is why the first commit of this PR gave it a 300 s timeout. The time is neither DFlash logic nor the step count: the tiny model is built in bf16, CPU bf16 matmuls are slow, and one step costs 0.9 s (float32: 0.1 s). Build the model in float32 and stop once the backbone and selector accuracy both pass 0.9, which happens after 22 steps. The 60-step ceiling and both assertions stay, so a slower run still has the old room to converge, and the 300 s override is gone. Measured on CPU with one thread: 53.7 s before, 2.5 s after (6.8 s for 60 float32 steps). The whole test file passes (33 tests) and its next slowest test takes about 1 s. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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Float32 alone takes the test from 53.7 s to 6.8 s on one thread (6.6 s under pytest), which is what made the 300 s timeout unnecessary. The early exit that stopped the loop after 22 steps saved another 4 s but changed the loop, so go back to the original 60 steps and assertions. The one-line change stays: the model is built in float32, now with a comment saying why (CPU bf16 matmuls are emulated and about 8x slower). Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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What does this PR do?
Type of change: CI (unit-test runtime)
The unit
linuxjob gates every GPU and example workflow (their pr-gate jobs wait for it), and its tests are CPU-bound but run serially. This runs them under pytest-xdist on the runner's four vCPUs. Thelinuxjob and the multi-version matrix getPYTEST_ADDOPTS=-n 4 --dist loadfileandOMP_NUM_THREADS=1: one worker per vCPU (-n autocounts physical cores), whole files per worker, and one thread per worker, because with torch's default threads the runner is oversubscribed and slower than serial (1,481 s and 41 failures in my local runs).What else changes so the suite passes under xdist:
noxfile.py: the second pytest process that runs themanualtests clearsPYTEST_ADDOPTS, so it stays serial. Those tests leak global state into each other, and a worker would run them in some order.tests/_test_utils/torch/quantization/onnx_export.py:TEST_MODELSwas a set of classes, whose iteration order differs between processes, so workers collected different test ids. It is a tuple now.test_hf_dflash2.py::test_overfits_a_single_batchtook about 53 s, more than the 60 s default call timeout once a worker runs it on one thread. Its tiny model is built in bf16, and a CPU without native bf16 support emulates bf16 matmuls (0.9 s per step, 0.1 s in float32). The model is float32 now, which takes the test to 6.6 s on one thread, so it needs no timeout override; the loop and both assertions are unchanged.test_full_algorithms_vision.py::test_search_constraintsassignedConstraintsFunc._get_true_latencyand never restored it. Serial runs never noticed, becausetest_evaluate_constraints.pysorts first. Under xdist a worker can get the files in the other order, and the Python 3.10 and 3.14 legs failed two tests after it. It usesmonkeypatchnow.tests/conftest.py: the unit per-test cap is 120 s on every platform.test_dist.py::test_data_paralleltakes 8-15 s serial and 25-35 s with four workers sharing four vCPUs, and went over 60 s on the slowest runner. A hung test is still reported, after 2 min instead of 1.Why: on current main the
linuxjob has a median of 12.9 min (27 runs of other PRs since #2823 merged), and a pull request's GPU run waits a median 14.5 min for it (125 runs of 33 PRs).Time improvement (measured in CI)
Unit
linuxjob: serial on current main (27 runs of other PRs since #2823 merged) against the runs of this series with-n 4.linux, then the multi-version and Windows legslinuxcheck is done (pr-gate / wait-checks, at least 5 min). That wait is a median 14.5 min (IQR 12.9-15.8) on 125 GPU runs of 33 PRs since Speed up CPU unit tests to stay under the 20 min CI limit #2823; in this PR's own GPU run it was 9.7 min (itslinuxjob took 10.9 min). With a 7 minlinuxjob instead of 12.9 min, a GPU run requested right after a push starts about 6 min earlier. That figure is derived from the job times: the later runs of the series were requested after their unit check had finished (the wait sat at its 5.2 min floor in 7 of the 9 GPU runs), so they cannot show it.Method: every PR of the series has its own CI run, so "before" is the run of the PR(s) below that lack the change and "after" the runs that carry it. Times come from the job logs (
--durations, or the gap between consecutive result lines). Where runner speed matters, the tests that no PR of the series touches scale each run, and the raw and the scaled medians are both shown. One test varies by 15-30% from run to run on its own, so smaller differences are not evidence.Usage
Nothing user-facing. Locally:
OMP_NUM_THREADS=1 pytest tests/unit -n 4 --dist loadfile.Testing
tests/uniton 4 CPUs with coverage as in CI, on the base before Speed up CPU unit tests to stay under the 20 min CI limit #2823: serial 825 s, this configuration 332-344 s in three repeated runs (4,724 passed, 0 failed).linuxjob took 10.9 min (479 s of pytest) against the 12.9 min serial median; see the time section above for the later runs of the series.tests/unitwithoutpuzzletron(it needshydra, absent from my local environment) in reversed and in shuffled file order shows no other order dependence;test_search_constraintsfollowed bytest_evaluate_constraints.pyin one process failed before the fix and passes after it.test_hf_dflash2.py(33 tests) on one CPU thread: 13.8 s, of whichtest_overfits_a_single_batchtakes 6.6 s (53.7 s with the bf16 model; the next slowest test takes about 1 s).Before your PR is "Ready for review"
Make sure you read and follow Contributor guidelines and your commits are signed (
git commit -s -S).Make sure you read and follow the Security Best Practices (e.g. avoiding hardcoded
trust_remote_code=True,torch.load(..., weights_only=False),pickle, etc.).CONTRIBUTING.md: no new dependency (pytest-xdistis already in thedev-testextra on main)Additional Information
Slice 1 of 11 of the GPU-CI speed-up work, split out of the reference draft #2730 (not for merge; it holds the whole series with its measurements). Merge in order; each PR stands on its own and passes CI without the later ones.
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