#pypy on 2017-08-19 — irc logs at freenode.irclog.whitequark.org

2017-07-05 11:38 cfbolz changed the topic of #pypy to: PyPy, the flexible snake (IRC logs: https://botbot.me/freenode/pypy/ ) | use cffi for calling C | "the modern world where network packets and compiler optimizations are effectively hostile"

00:00 <bbot2> Started: http://buildbot.pypy.org/builders/pypy-c-jit-linux-s390x/builds/640 [default]

00:01 <bbot2> Success: http://buildbot.pypy.org/builders/build-pypy-c-jit-linux-armel/builds/1880

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00:13 <bbot2> Success: http://buildbot.pypy.org/builders/pypy-c-jit-linux-x86-32/builds/4146 [default]

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00:42 <bbot2> Success: http://buildbot.pypy.org/builders/build-pypy-c-jit-linux-armhf-raring/builds/1631

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01:00 <bbot2> Started: http://buildbot.pypy.org/builders/pypy-c-jit-linux-x86-64/builds/4844 [py3.5]

01:00 <bbot2> Started: http://buildbot.pypy.org/builders/own-linux-x86-64/builds/6156 [py3.5]

01:00 <bbot2> Started: http://buildbot.pypy.org/builders/own-linux-x86-32/builds/5387 [py3.5]

01:00 <bbot2> Started: http://buildbot.pypy.org/builders/pypy-c-jit-linux-x86-32/builds/4147 [py3.5]

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01:03 <bbot2> Failure: http://buildbot.pypy.org/builders/pypy-c-jit-linux-x86-64/builds/4844 [py3.5]

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01:15 <bbot2> Success: http://buildbot.pypy.org/builders/build-pypy-c-linux-armhf-raspbian/builds/1509

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01:30 <bbot2> Failure: http://buildbot.pypy.org/builders/pypy-c-jit-macosx-x86-64/builds/3222 [default]

01:30 <bbot2> Started: http://buildbot.pypy.org/builders/pypy-c-jit-macosx-x86-64/builds/3223 [py3.5]

01:40 <bbot2> Failure: http://buildbot.pypy.org/builders/pypy-c-jit-macosx-x86-64/builds/3223 [py3.5]

01:43 <bbot2> Success: http://buildbot.pypy.org/builders/build-pypy-c-linux-armel/builds/1769

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02:29 <bbot2> Failure: http://buildbot.pypy.org/builders/pypy-c-jit-linux-x86-32/builds/4147 [py3.5]

02:32 <bbot2> Failure: http://buildbot.pypy.org/builders/own-linux-x86-64/builds/6156 [py3.5]

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03:00 <bbot2> Started: http://buildbot.pypy.org/builders/jit-benchmark-linux-x86-64/builds/2304

03:00 <bbot2> Started: http://buildbot.pypy.org/builders/jit-benchmark-linux-x86-32/builds/3096

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03:04 <bbot2> Started: http://buildbot.pypy.org/builders/pypy-c-jit-linux-armhf-v7/builds/1250

03:04 <bbot2> Success: http://buildbot.pypy.org/builders/build-pypy-c-jit-linux-armhf-raspbian/builds/1636

03:11 <bbot2> Failure: http://buildbot.pypy.org/builders/own-linux-x86-32/builds/5387 [py3.5]

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03:12 <kawing-chiu> njs: could you elaborate a bit on numpy's weird needs? I'm curious on it.

03:15 <njs> it uses a lot of Python C APIs to efficiently interact with the interpreter, it defines types in C, ...

03:16 <njs> so like, for example, on my laptop, if x = np.float32(1), then x + x takes <80 ns on cpython

03:17 <njs> OTOH if you have a type defined in Python, 'class Float32: def __add__(self, other): return Float32()', then the fastest possible x + x is ~300 ns on CPython

03:17 <Alex_Gaynor> (gosh, adding two floats in anything more than like... 1ns sounds like too much)

03:17 <njs> (of course pypy is different, but no-one's going to accept a 3x slowdown on cpython)

03:17 <njs> Alex_Gaynor: yeah, it's all boxing/unboxing overhead

03:17 <njs> Alex_Gaynor: numpy is too slow actually, python manages to do it in ~10 ns

03:18 <Alex_Gaynor> njs: Python doesn't pay the dynamic dispatch overhead because there's a special case in ceval, although that might be integer only now that I think about it.

03:19 <njs> Alex_Gaynor: I don't think so? I think the only special case is for the str += str hack

03:20 <Alex_Gaynor> njs: ah, it has a special case for ints on 2.7, but not 3.x, probably because on 3.x adding two ints is a fully blown arbitrary precision operation with god knows how many memory reads/writes

03:20 <Alex_Gaynor> https://github.com/python/cpython/blob/2.7/Python/ceval.c#L1464-L1496

03:22 <njs> Alex_Gaynor: that or victor decided that that special case wasn't worth it in the first place, judging from the comment in master :-)

03:25 <kawing-chiu> So, to make the numpy beast efficient in pypy, inevitably we need to rewrite part of it in pypy(rpython)?

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03:52 <njs> kawing-chiu: in principle, we might be able to come up with some kind of input language that can be compiled into forms that are efficient on both cpython or pypy

03:52 <njs> kawing-chiu: this idea isn't very far developed though

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04:25 <kawing-chiu> njs: I see. Is cython considered a valid "input language"?

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04:40 <bbot2> Success: http://buildbot.pypy.org/builders/pypy-c-jit-linux-s390x/builds/640 [default]

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04:59 <njs> kawing-chiu: something cython-ish seems like a good bet, yeah

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