Re: Building CPython

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.python
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$Zf4.246168@fx22.am4>
Message-ID	<xpb5x.597872$X95.548374@fx10.am4> (permalink)
Organization	virginmedia.com
Date	2015-05-15 01:50 +0100

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On 14/05/2015 22:55, BartC wrote:

 > def whiletest():
 >      i=0
 >      while i<=100000000:
 >          i=i+1
 >
 > whiletest()
 >

> 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.

(Actually my ASM-aided code took 0.5 seconds (some crucial section had 
been commented out). Faster than PyPy and just using simple brute-force 
methods.)

> 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.

It turns out the LOAD_FASTs were the simple byte-codes!

I'm just starting to find out just how much of a big complicated mess 
this project really is. I wouldn't be surprised if there aren't many 
people who actually understand it all, and that would explain why no-one 
seems to have had much luck in getting the speed up (if anything, it's 
getting slower).

I still have no idea yet exactly what an object comprises. I know that 
even an innocuous-looking LOAD_CONST actually loads a tuple from a table 
(complete with flag testing and bounds checks, although taking those out 
made no discernible difference).

It appears to be those "<=" and "+" operations in the code above where 
much of the time is spent. When I trace out the execution paths a bit 
more, I'll have a better picture of how many lines of C code are 
involved in each iteration.

-- 
Bartc

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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