Re: Building CPython

Date	2015-05-14 23:19 +0100
From	MRAB <python@mrabarnett.plus.com>
Subject	Re: Building CPython
References	<7JN4x.37133$Q41.15375@fx25.am4> <mailman.464.1431556504.12865.python-list@python.org> <6w35x.645690$I97.19867@fx31.am4> <874mnfunpn.fsf@elektro.pacujo.net> <zR85x.441429$Zf4.246168@fx22.am4>
Newsgroups	comp.lang.python
Message-ID	<mailman.19.1431641969.17265.python-list@python.org> (permalink)

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On 2015-05-14 22:55, BartC wrote:
> On 14/05/2015 17:29, Marko Rauhamaa wrote:
>> BartC <bc@freeuk.com>:
>>
>>> That's a shame because I wanted to tinker with the main dispatcher
>>> loop to try and find out what exactly is making it slow. Nothing that
>>> seems obvious at first sight.
>>
>> My guess is the main culprit is attribute lookup in two ways:
>>
>>   * Each object attribute reference involves a dictionary lookup.
>>
>>   * Each method call involves *two* dictionary lookups plus an object
>>     creation.
>>
>> Tell us what you find out.
>
> I'm just starting but I can tell you that it isn't because debug mode
> (Py_DEBUG defined) was left on by mistake!
>
> What is interesting however is that on the very simple test I'm doing (a
> while loop incrementing a variable up to 100 million), the timings under
> Windows are:
>
> Python 2.5       9.2 seconds
> Python 3.1      13.1
> Python 3.4.3    17.0
> Python 3.4.3    14.3 (under Ubuntu on same machine, using the version
>                        I built today)
>
> That's quite a big range!
>
> PyPy does it in 0.7 seconds. The same program within my own *simple*
> bytecode interpreter (not for Python) has a fastest time of 1.5 seconds
> but makes use of ASM. A version 100% in (gcc) C can manage 2 seconds.
>
> So far I haven't find anything that explains the discrepancy (the
> languages are different, mine is simpler, but the Python code isn't
> doing anything that complicated, only LOAD_FASTs and such, and LOAD_FAST
> is apparently just an array access.
>
> But the nearly 2:1 difference between new and old Python versions is
> also intriguing.
>
> def whiletest():
> 	i=0
> 	while i<=100000000:
> 		i=i+1
>
> whiletest()
>
Python 2.x has int and long; Python 3 has int, which is the old 'long'.
Try Python 2 with longs.

Thread

Building CPython BartC <bc@freeuk.com> - 2015-05-13 20:36 +0100
  Re: Building CPython Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-13 20:58 +0100
  Re: Building CPython Terry Reedy <tjreedy@udel.edu> - 2015-05-13 18:34 -0400
    Re: Building CPython BartC <bc@freeuk.com> - 2015-05-14 16:51 +0100
      Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 02:09 +1000
        Re: Building CPython BartC <bc@freeuk.com> - 2015-05-14 18:02 +0100
          Re: Building CPython Dave Angel <davea@davea.name> - 2015-05-14 13:10 -0400
          Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 03:11 +1000
            Re: Building CPython BartC <bc@freeuk.com> - 2015-05-14 18:32 +0100
              Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 03:45 +1000
          Re: Building CPython Terry Reedy <tjreedy@udel.edu> - 2015-05-14 14:50 -0400
            Re: Building CPython Christian Gollwitzer <auriocus@gmx.de> - 2015-05-15 12:51 +0200
              Re: Building CPython Terry Reedy <tjreedy@udel.edu> - 2015-05-15 17:19 -0400
      Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-14 19:29 +0300
        Re: Building CPython BartC <bc@freeuk.com> - 2015-05-14 22:55 +0100
          Re: Building CPython MRAB <python@mrabarnett.plus.com> - 2015-05-14 23:19 +0100
          Re: Building CPython BartC <bc@freeuk.com> - 2015-05-15 01:50 +0100
            Re: Building CPython Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-15 18:05 +1200
              Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-15 11:59 +0300
                Re: Building CPython wxjmfauth@gmail.com - 2015-05-15 02:07 -0700
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-15 12:20 +0300
                Re: Building CPython wxjmfauth@gmail.com - 2015-05-15 02:51 -0700
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-15 13:52 +0300
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-15 22:10 +1000
                Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 22:34 +1000
                Re: Building CPython wxjmfauth@gmail.com - 2015-05-15 07:11 -0700
                Re: Building CPython Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-15 13:41 +0100
                Re: Building CPython Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-15 13:38 +0100
                Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 19:43 +1000
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-15 13:50 +0300
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-15 22:43 +1000
                Re: Building CPython Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-15 09:00 -0600
                Re: Building CPython Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-15 09:04 -0600
                Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-16 01:06 +1000
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-15 20:14 +1000
                Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-15 20:25 +1000
                Re: Building CPython Terry Reedy <tjreedy@udel.edu> - 2015-05-15 17:05 -0400
                Re: Building CPython BartC <bc@freeuk.com> - 2015-05-15 22:54 +0100
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-16 01:44 +0300
                Re: Building CPython Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-16 00:27 +0100
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-16 11:55 +1000
                Re: Building CPython Chris Angelico <rosuav@gmail.com> - 2015-05-16 12:15 +1000
                Re: Building CPython Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-16 03:17 +0100
                Re: Building CPython BartC <bc@freeuk.com> - 2015-05-16 01:43 +0100
                Re: Building CPython MRAB <python@mrabarnett.plus.com> - 2015-05-16 02:16 +0100
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-16 11:08 +0300
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-16 19:40 +1000
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-16 16:59 +0300
                Re: Building CPython Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-17 04:18 +1000
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-16 21:55 +0300
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-17 01:51 +0300
                Re: Building CPython Marko Rauhamaa <marko@pacujo.net> - 2015-05-17 23:49 +0300
                Re: Building CPython Terry Reedy <tjreedy@udel.edu> - 2015-05-15 19:54 -0400
              Re: Building CPython BartC <bc@freeuk.com> - 2015-05-15 10:32 +0100
                Re: Building CPython Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-16 12:55 +1200
                Re: Building CPython Jonas Wielicki <jonas@wielicki.name> - 2015-05-17 14:25 +0200
                Re: Building CPython BartC <bc@freeuk.com> - 2015-05-17 14:41 +0100

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