PERF: add a fast path to ufunc type resolution #27859
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colesbury
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Nov 26, 2024
| PyArray_DTypeMeta *op_dtypes[], | ||
| npy_bool legacy_promotion_is_possible) | ||
| { | ||
| PyObject *info = PyArrayIdentityHash_GetItem(ufunc->_dispatch_cache, |
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I don't think this is thread-safe because we may read from the hash table while another thread is concurrently modifying it, including possibly resizing the table.
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😓 That's a good point.
Is there a thread-safe way to do it without an RW lock?
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We could make PyArrayIdentityHash a concurrent hash table. That's generally hard, but there are a few things that make this specific case easier:
- We only care about concurrent read performance
- Entries are never deleted or overwritten
But we'd still have to deal with hash table resizing, which makes it more complex.
I think a RW lock will be simpler as long as it provides good enough read performance.
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I'm going to try again using an RW-lock |
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Fixes #27786.
Our group is thinking about ways to add better benchmarking so we don't regress on issues like this, see Quansight-Labs/free-threaded-compatibility#117. For now if it's alright I'd just like to merge this fix.
With the test script in the issue and this PR applied, I get the following scaling:
generating this made my laptop pretty hot!