Re: Optimization of cascading recursions in "C" compilers?

From	Janis Papanagnou <janis_papanagnou+ng@hotmail.com>
Newsgroups	comp.lang.c
Subject	Re: Optimization of cascading recursions in "C" compilers?
Date	2025-10-01 00:15 +0200
Organization	A noiseless patient Spider
Message-ID	<10bhkpq$3vput$1@dont-email.me> (permalink)
References	<10bgug3$3pmee$1@dont-email.me> <10bgv25$3pq80$1@dont-email.me>

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On 30.09.2025 18:04, David Brown wrote:
> On 30/09/2025 17:54, Janis Papanagnou wrote:
>> In another newsgroup the question came up to what degree the
>> GNU "C" compilers can handle optimization of recursions like
>> fib() or ack(), i.e. cascading ones. Somebody here may know?
>>
>> Can we expect that (with the higher optimization levels) the
>> exponential complexity from cascaded recursion gets linearized?
>>
>> Janis
> 
> Optimising compilers can generally handle straight tail recursion well
> enough.  So if you write a simple "fib" function with two recursions,
> you'll get one turned into a loop and the other kept as recursion.  I
> don't think there is a general way to turn multiple recursions into
> loops - you have to make a stack-like data structure somewhere along the
> line, and no C compiler is going to do that automatically.

Well, a linear-recursion to iterative-loop transformation would
not reduce algorithmic complexity. So a stack would not address
the potential goal of my question. (See also my other reply for
more details/explanations/clarifications concerning my question.)

> 
> You might find that compilers like the GHC for Haskell can do better,
> since recursion is the bread and butter of functional programming
> languages.

Would the Haskell compilers do such transformations?

In the mentioned other post I have two variants, both functionally
formulated. My impression was that these sorts of transformations
might not lie within the usual refactoring optimizing capabilities
of common compilers.

Janis

Thread

Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-09-30 17:54 +0200
  Re: Optimization of cascading recursions in "C" compilers? David Brown <david.brown@hesbynett.no> - 2025-09-30 18:04 +0200
    Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-01 00:15 +0200
  Re: Optimization of cascading recursions in "C" compilers? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-09-30 16:12 +0000
    Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-01 00:07 +0200
      Re: Optimization of cascading recursions in "C" compilers? Ben Bacarisse <ben@bsb.me.uk> - 2025-10-01 10:05 +0100
        Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-01 19:01 +0200
          Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-01 19:08 +0200
            Re: Optimization of cascading recursions in "C" compilers? Ben Bacarisse <ben@bsb.me.uk> - 2025-10-02 00:48 +0100
              Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-02 05:25 +0200
                Re: Optimization of cascading recursions in "C" compilers? Ben Bacarisse <ben@bsb.me.uk> - 2025-10-03 15:09 +0100
                Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-03 16:47 +0200
    Re: Optimization of cascading recursions in "C" compilers? bart <bc@freeuk.com> - 2025-10-01 00:02 +0100
      Re: Optimization of cascading recursions in "C" compilers? antispam@fricas.org (Waldek Hebisch) - 2025-10-01 01:22 +0000
    Re: Optimization of cascading recursions in "C" compilers? Rosario19 <Ros@invalid.invalid> - 2025-10-23 00:37 +0200
      Re: Optimization of cascading recursions in "C" compilers? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-22 23:36 +0000
        Re: Optimization of cascading recursions in "C" compilers? Rosario19 <Ros@invalid.invalid> - 2025-10-24 09:53 +0200
          Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-24 15:36 +0200
            Re: Optimization of cascading recursions in "C" compilers? Michael S <already5chosen@yahoo.com> - 2025-10-24 17:35 +0300
              Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-24 17:22 +0200
                Re: Optimization of cascading recursions in "C" compilers? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-24 17:14 +0000
                Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-24 20:31 +0200
                Re: Optimization of cascading recursions in "C" compilers? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-24 23:59 +0000
                Re: Optimization of cascading recursions in "C" compilers? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-10-27 05:48 -0400
                Re: Optimization of cascading recursions in "C" compilers? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-10-27 12:52 +0100
                Re: Optimization of cascading recursions in "C" compilers? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-10-27 14:41 -0400
                Re: Optimization of cascading recursions in "C" compilers? Michael S <already5chosen@yahoo.com> - 2025-10-27 22:33 +0200
                Re: Optimization of cascading recursions in "C" compilers? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-10-27 16:52 -0400
                Re: Optimization of cascading recursions in "C" compilers? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-10-27 21:03 +0000
                Re: Optimization of cascading recursions in "C" compilers? antispam@fricas.org (Waldek Hebisch) - 2025-10-28 01:58 +0000

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