[Python-Dev] PEP 3146: Merge Unladen Swallow into CPython (original) (raw)

Collin Winter collinwinter at google.com
Sat Feb 13 01:04:07 CET 2010

Hey Maciej,

On Thu, Feb 11, 2010 at 6:39 AM, Maciej Fijalkowski <fijall at gmail.com> wrote:

Snippet from:

http://codereview.appspot.com/186247/diff2/5014:8003/7002 PyPy: PyPy [#pypy] has good performance on numerical code, but is slower than Unladen Swallow on non-numerical workloads. PyPy only supports 32-bit x86 code generation. It has poor support for CPython extension modules, making migration for large applications prohibitively expensive. That part at the very least has some sort of personal opinion "prohibitively",

Of course; difficulty is always in the eye of the person doing the work. Simply put, PyPy is not a drop-in replacement for CPython: there is no embedding API, much less the same one exported by CPython; important libraries, such as MySQLdb and pycrypto, do not build against PyPy; PyPy is 32-bit x86 only.

All of these problems can be overcome with enough time/effort/money, but I think you'd agree that, if all I'm trying to do is speed up my application, adding a new x86-64 backend or implementing support for CPython extension modules is certainly north of "prohibitively expensive". I stand by that wording. I'm willing to enumerate all of PyPy's deficiencies in this regard in the PEP, rather than the current vaguer wording, if you'd prefer.

while the other part is not completely true "slower than US on non-numerical workloads". Fancy providing a proof for that? I'm well aware that there are benchmarks on which PyPy is slower than CPython or US, however, I would like a bit more weighted opinion in the PEP.

Based on the benchmarks you're running at http://codespeak.net:8099/plotsummary.html, PyPy is slower than CPython on many non-numerical workloads, which Unladen Swallow is faster than CPython at. Looking at the benchmarks there at which PyPy is faster than CPython, they are primarily numerical; this was the basis for the wording in the PEP.

My own recent benchmarking of PyPy and Unladen Swallow (both trunk; PyPy wouldn't run some benchmarks):

| Benchmark | PyPy | Unladen | Change | +==============+=======+=========+=================+ | ai | 0.61 | 0.51 | 1.1921x faster | | django | 0.68 | 0.8 | 1.1898x slower | | float | 0.03 | 0.07 | 2.7108x slower | | html5lib | 20.04 | 16.42 | 1.2201x faster | | pickle | 17.7 | 1.09 | 16.2465x faster | | rietveld | 1.09 | 0.59 | 1.8597x faster | | slowpickle | 0.43 | 0.56 | 1.2956x slower | | slowspitfire | 2.5 | 0.63 | 3.9853x faster | | slowunpickle | 0.26 | 0.27 | 1.0585x slower | | unpickle | 28.45 | 0.78 | 36.6427x faster |

I'm happy to change the wording to "slower than US on some workloads".

Thanks, Collin Winter

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