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Re: Bug in timsort!?

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Tue, 24 Feb 2015 15:59:34 -0700
Subject Re: Bug in timsort!?
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On Tue, Feb 24, 2015 at 3:45 PM, Grant Edwards <invalid@invalid.invalid> wrote:
> On 2015-02-24, Roy Smith <roy@panix.com> wrote:
>
>> http://envisage-project.eu/proving-android-java-and-python-sorting-algorithm-is-broken-and-how-to-fix-it/
>
> I don't get it.
>
>     3.2 Corrected Python merge_collapse function
>
>     merge_collapse(MergeState *ms)
>     {
>         struct s_slice *p = ms->pending;
>
>         assert(ms);
>         while (ms->n > 1) {
>             Py_ssize_t n = ms->n - 2;
>             if (     n > 0   && p[n-1].len <= p[n].len + p[n+1].len
>                 || (n-1 > 0 &&  p[n-2].len <= p[n].len + p[n-1].len)) {
>                 if (p[n-1].len < p[n+1].len)
>                     --n;
>                 if (merge_at(ms, n) < 0)
>                     return -1;
>             }
>             else if (p[n].len <= p[n+1].len) {
>                      if (merge_at(ms, n) < 0)
>                             return -1;
>             }
>             else
>                 break;
>         }
>         return 0;
>     }
>
> Or does "Python function" mean something else in this context?

Recall that CPython is implemented in C. ;-)

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Thread

Bug in timsort!? Roy Smith <roy@panix.com> - 2015-02-24 13:34 -0800
  Re: Bug in timsort!? Zachary Ware <zachary.ware+pylist@gmail.com> - 2015-02-24 15:40 -0600
  Re: Bug in timsort!? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-02-24 21:49 +0000
    Re: Bug in timsort!? sohcahtoa82@gmail.com - 2015-02-24 14:36 -0800
      Re: Bug in timsort!? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-02-25 00:38 +0000
  Re: Bug in timsort!? Grant Edwards <invalid@invalid.invalid> - 2015-02-24 22:45 +0000
    Re: Bug in timsort!? Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-24 15:59 -0700
    Re: Bug in timsort!? Robert Kern <robert.kern@gmail.com> - 2015-02-25 11:34 +0000
      Re: Bug in timsort!? Grant Edwards <invalid@invalid.invalid> - 2015-02-25 15:49 +0000
  Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-25 10:33 +1100
  Re: Bug in timsort!? MRAB <python@mrabarnett.plus.com> - 2015-02-24 23:38 +0000
  Re: Bug in timsort!? Skip Montanaro <skip.montanaro@gmail.com> - 2015-02-24 17:50 -0600
  Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-25 11:07 +1100
    Re: Bug in timsort!? Paddy <paddy3118@gmail.com> - 2015-02-25 01:10 -0800
      Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-25 21:11 +1100
  Re: Bug in timsort!? Chris Kaynor <ckaynor@zindagigames.com> - 2015-02-24 16:38 -0800
  Re: Bug in timsort!? Terry Reedy <tjreedy@udel.edu> - 2015-02-24 21:52 -0500
  Re: Bug in timsort!? Dave Angel <davea@davea.name> - 2015-02-24 21:41 -0500
  Re: Bug in timsort!? Ned Deily <nad@acm.org> - 2015-02-25 01:04 -0800
  Re: Bug in timsort!? Sturla Molden <sturla.molden@gmail.com> - 2015-02-25 14:58 +0100
    Re: Bug in timsort!? alister <alister.nospam.ware@ntlworld.com> - 2015-02-25 15:03 +0000
      Re: Bug in timsort!? Zachary Ware <zachary.ware+pylist@gmail.com> - 2015-02-25 09:23 -0600
      Re: Bug in timsort!? Terry Reedy <tjreedy@udel.edu> - 2015-02-25 16:08 -0500
    Re: Bug in timsort!? Roy Smith <roy@panix.com> - 2015-02-25 19:12 -0500
  Re: Bug in timsort!? Jonas Wielicki <jonas@wielicki.name> - 2015-02-25 15:07 +0100
  Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-26 01:33 +1100
  Re: Bug in timsort!? Sturla Molden <sturla.molden@gmail.com> - 2015-02-25 16:05 +0100
  Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-26 02:11 +1100
  Re: Bug in timsort!? Peter Otten <__peter__@web.de> - 2015-02-25 17:04 +0100
    Re: Bug in timsort!? Mario Figueiredo <marfig@gmail.com> - 2015-02-25 18:22 +0100
      Re: Bug in timsort!? Sturla Molden <sturla.molden@gmail.com> - 2015-02-25 19:41 +0100
      Re: Bug in timsort!? Jonas Wielicki <jonas@wielicki.name> - 2015-02-25 19:46 +0100
      Re: Bug in timsort!? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-02-25 20:07 +0000
  Re: Bug in timsort!? Sturla Molden <sturla.molden@gmail.com> - 2015-02-25 17:44 +0100
    Re: Bug in timsort!? Mario Figueiredo <marfig@gmail.com> - 2015-02-25 18:29 +0100
    Re: Bug in timsort!? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-26 10:13 +1100
      Re: Bug in timsort!? Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-25 22:51 -0700
  Re: Bug in timsort!? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-02-25 16:50 +0000
  Re: Bug in timsort!? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-02-25 16:55 +0000
  Re: Bug in timsort!? Chris Kaynor <ckaynor@zindagigames.com> - 2015-02-25 08:56 -0800
  Re: Bug in timsort!? Chris Angelico <rosuav@gmail.com> - 2015-02-26 04:18 +1100
  Re: Bug in timsort!? Peter Otten <__peter__@web.de> - 2015-02-25 18:21 +0100
  Re: Bug in timsort!? Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-25 12:42 -0700
  Re: Bug in timsort!? Serhiy Storchaka <storchaka@gmail.com> - 2015-02-26 09:33 +0200

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