Re: Detecting repeated subsequences of identical items

From	Oscar Benjamin <oscar.j.benjamin@gmail.com>
Newsgroups	comp.lang.python
Subject	Re: Detecting repeated subsequences of identical items
Date	2016-04-21 15:30 +0100
Message-ID	<mailman.13.1461249058.23626.python-list@python.org> (permalink)
References	(2 earlier) <mailman.7.1461228807.23626.python-list@python.org> <5718c457$0$1605$c3e8da3$5496439d@news.astraweb.com> <CAHVvXxQAPP8-31Nb3vM+=O4wYpXEuH1FH3n05N59KnqpC8C0PQ@mail.gmail.com> <CAPTjJmrp7ufKa194h4RrCh0F2y0FuDqaUkcV6-B-sHDWvosdKA@mail.gmail.com> <CAHVvXxQ=qbfxZAkznhFEpyNv-7WdFYzvJiQxrOzi9Ep7zanzaA@mail.gmail.com>

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On 21 April 2016 at 15:12, Chris Angelico <rosuav@gmail.com> wrote:
> On Fri, Apr 22, 2016 at 12:01 AM, Oscar Benjamin
> <oscar.j.benjamin@gmail.com> wrote:
>> In the recursive stack overflow case what you'll usually have is
>>
>> 1) A few frames leading up to the start of recursion
>> 2) A long repetitive sequence of frames
>> 3) A few frames at the end showing how the exception was ultimately triggered.
>>
>> You just need to find the cycle that makes that big long sequence.
>
> If the stack got overflowed, there won't usually be a part 3, as part
> 2 is the bit that hits sys.recursionlimit (unless increasing the
> recursion limit by a finite number would solve the problem). For other
> exceptions, yes, this is what you'd see.

If you have:

def f(x):
    return g(x+1)

def g(x):
    x = h(x)  # <-- stack can overflow inside here
    return f(x+1)

# etc.

So you have a long sequence that goes f, g, f, g but at the end the
stack can overflow while (not recursively) calling h leaving a small
non-cyclic part at the end.

--
Oscar

Thread

Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-21 13:07 +1000
  Re: Detecting repeated subsequences of identical items Ethan Furman <ethan@stoneleaf.us> - 2016-04-20 20:57 -0700
  Re: Detecting repeated subsequences of identical items Ethan Furman <ethan@stoneleaf.us> - 2016-04-20 21:15 -0700
  Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-21 15:37 +1000
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 06:35 +0000
    Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-21 18:05 +1000
      Re: Detecting repeated subsequences of identical items Nobody <nobody@nowhere.invalid> - 2016-04-21 13:02 +0100
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 06:49 +0000
  Re: Detecting repeated subsequences of identical items Vlastimil Brom <vlastimil.brom@gmail.com> - 2016-04-21 08:54 +0200
  Re: Detecting repeated subsequences of identical items Michael Selik <michael.selik@gmail.com> - 2016-04-21 07:05 +0000
  Re: Detecting repeated subsequences of identical items Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2016-04-21 09:25 +0200
  Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 09:53 +0100
    Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-21 22:15 +1000
      Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 15:01 +0100
      Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-22 00:12 +1000
        Re: Detecting repeated subsequences of identical items Steven D'Aprano <steve@pearwood.info> - 2016-04-23 01:00 +1000
      Re: Detecting repeated subsequences of identical items Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-21 15:30 +0100
      Re: Detecting repeated subsequences of identical items Chris Angelico <rosuav@gmail.com> - 2016-04-22 01:02 +1000
  Re: Detecting repeated subsequences of identical items Serhiy Storchaka <storchaka@gmail.com> - 2016-04-21 14:56 +0300

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