Re: Copy array with small changes

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: Copy array with small changes
Date	2018-03-12 17:42 +0000
Organization	A noiseless patient Spider
Message-ID	<87sh95ur60.fsf@bsb.me.uk> (permalink)
References	<p848dh$oko$1@dont-email.me> <slrnpac9bc.eu5.grahn+nntp@frailea.sa.invalid> <p864ci$btf$1@dont-email.me>

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Noob <root@127.0.0.1> writes:

> On 12/03/2018 07:59, Jorgen Grahn wrote:
<snip>
>> Because the function's task is so strange, I get the feeling that it
>> may be worth refactoring the code as a whole.  For example, it's
>> called "update_array" -- are you overwriting the same array with
>> basically the same data, over and over again?
>> 
>> I'm partly asking because with the requirements you have on
>> update_array(), I don't think it can be made internally elegant.
>
> OK, you want the big picture :-)
>
> The task is to evaluate all arithmetic expressions involving
> N numbers and the 4 arithmetic operators [+ - * /]

And it's Catalan numbers again!

Is the maximum value for N fixed?  In other words are the problem
instance mostly due to different sets of numbers, or can N be
arbitrarily large?  I'm guessing the latter because you talk of billions
of calls.

For smallish max N (six, in the case of the UK TV show Countdown that
BartC mentioned), I'd pre-compute the expression trees and apply them to
different permutation of the numbers and selections for the operands.

-- 
Ben.

Thread

Copy array with small changes Noob <root@127.0.0.1> - 2018-03-11 22:51 +0100
  Re: Copy array with small changes supercat@casperkitty.com - 2018-03-11 15:11 -0700
  Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-11 18:12 -0400
    Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-11 22:35 +0000
      Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-13 13:10 -0400
  Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-11 22:13 +0000
    Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 00:04 +0000
    Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 10:35 +0000
      Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 12:37 +0000
        Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 13:10 +0000
        Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-12 13:34 +0000
          Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:22 -0700
        Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 07:47 -0700
          Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 14:56 +0000
            Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 15:14 +0000
            Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 08:53 -0700
        Re: Copy array with small changes Keith Thompson <kst-u@mib.org> - 2018-03-12 09:08 -0700
          Re: Copy array with small changes supercat@casperkitty.com - 2018-03-12 09:57 -0700
            Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-13 13:21 -0400
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 15:25 +0100
      Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 15:09 +0000
  Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-12 06:59 +0000
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 15:55 +0100
      Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 15:07 +0000
      Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 09:03 -0700
      Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-12 17:42 +0000
        Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 23:33 +0100
          Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-12 23:44 +0100
          Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:48 -0700
            Re: Copy array with small changes Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-18 03:31 -0700
            Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-22 17:10 +0100
        Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:24 -0700
          Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-17 18:04 +0000
            Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 22:55 -0700
              Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-27 15:28 +0100
                Re: Copy array with small changes Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-28 14:42 -0700
      Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-13 12:46 +0000
  Re: Copy array with small changes Anton Shepelev <anton.txt@gmail.com> - 2018-03-12 22:36 +0300
  Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-12 23:32 +0100
    Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-13 10:42 +0100
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-13 11:37 +0100
      Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-13 21:27 +0100
  Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:55 -0700

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