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gh-97933: add opcode for more efficient comprehension execution #101310
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@markshannon or @iritkatriel (or anyone else from faster-cpython team) -- if you could kick off a PyPerformance run with your fancy Github Action runner, I'd be much obliged! |
Done. |
Benchmark results are here: https://github.com/faster-cpython/benchmarking/blob/main/results/bm-20230125-3.12.0a4+-ee2ad56/bm-20230125-linux-x86_64-carljm-inlinecomp-3.12.0a4+-ee2ad56-vs-base.md (shows no difference overall). |
I can't see the detailed results (private repo), but if there's no impact overall then I guess they aren't that interesting :) We must not have any benchmarks that make heavy use of comprehensions. |
All benchmarks:
Benchmark hidden because not significant (33): aiohttp, async_tree_none, async_tree_cpu_io_mixed, async_tree_io, chameleon, bench_mp_pool, coverage, crypto_pyaes, dask, deepcopy, deltablue, django_template, djangocms, dulwich_log, genshi_text, genshi_xml, hexiom, html5lib, meteor_contest, mypy, nbody, nqueens, pprint_safe_repr, pprint_pformat, scimark_lu, scimark_sor, sqlglot_parse, sqlglot_transpile, sqlite_synth, sympy_str, unpickle_list, xml_etree_parse, xml_etree_generate |
* main: (225 commits) pythongh-102056: Fix a few bugs in error handling of exception printing code (python#102078) pythongh-102011: use sys.exception() instead of sys.exc_info() in docs where possible (python#102012) pythongh-101566: Sync with zipp 3.14. (pythonGH-102018) pythonGH-99818: improve the documentation for zipfile.Path and Traversable (pythonGH-101589) pythongh-88233: zipfile: handle extras after a zip64 extra (pythonGH-96161) pythongh-101981: Apply HOMEBREW related environment variables (pythongh-102074) pythongh-101907: Stop using `_Py_OPCODE` and `_Py_OPARG` macros (pythonGH-101912) pythongh-101819: Adapt _io types to heap types, batch 1 (pythonGH-101949) pythongh-101981: Build macOS as recommended by the devguide (pythonGH-102070) pythongh-97786: Fix compiler warnings in pytime.c (python#101826) pythongh-101578: Amend PyErr_{Set,Get}RaisedException docs (python#101962) Misc improvements to the float tutorial (pythonGH-102052) pythongh-85417: Clarify behaviour on branch cuts in cmath module (python#102046) pythongh-100425: Update tutorial docs related to sum() accuracy (FH-101854) Add missing 'is' to `cmath.log()` docstring (python#102049) pythongh-100210: Correct the comment link for unescaping HTML (python#100212) pythongh-97930: Also include subdirectory in makefile. (python#102030) pythongh-99735: Use required=True in argparse subparsers example (python#100927) Fix incorrectly documented attribute in csv docs (python#101250) pythonGH-84783: Make the slice object hashable (pythonGH-101264) ...
Closing this for now in favor of #101441 May reopen this approach if PEP 709 (implemented by that PR) is rejected. |
This avoids allocating a throwaway single-use function object every time we run a comprehension. Otherwise it shouldn't have any user-visible impact; the comprehension is still a separate code object and runs in its own frame, just as before. Tracebacks look the same, etc. We just have a new
COMPREHENSION
opcode that builds a frame directly from codeobject and optional closure and inline-calls it, without creating a function object.
In a micro-benchmark of comprehension execution time, this looks like it saves about 25%:
Currently this doesn't handle async comprehensions or generator expressions; those still create a function object and
CALL
it. In principle I think they could be handled as well, but to keep the PR smaller I'll defer that to a second PR if this one is merged.Closes #97933.