Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #127070

Re: Catching overflow

From jacobnavia <jacob@jacob.remcomp.fr>
Newsgroups comp.lang.c
Subject Re: Catching overflow
Date 2018-02-26 10:53 +0100
Organization A noiseless patient Spider
Message-ID <p70lfc$ia3$1@dont-email.me> (permalink)
References <p6vf4p$ot1$1@dont-email.me> <87efl8two2.fsf@bsb.me.uk> <p6vl8r$2c3$1@dont-email.me> <878tbgtudk.fsf@bsb.me.uk>

Show all headers | View raw

Le 26/02/2018 à 02:25, Ben Bacarisse a écrit :

> 
> Doing some of the calculation in 128 bits may be a needless
> optimisation.  With a series that grows this fast, a table is almost
> always going to be the best way to go.  A table of just 70 numbers can
> hold all the 128-bit Catalan numbers.  Even if you don't pre-compute
> any, just caching these as they get computed would probably mean you can
> use qfloats from the start.
> 

You can compute up to catalan(62) in 128 bits without overflow. The 
computation of catalan(63) upwards needs more than 128 bits precision.

I have already optimized that, without a table but just computing all 
catalan numbers less than 63 in 128 bits, what goes very fast.

The problem is, for catalan numbers higher than 62, I can't cache the 
results since the goal number is involved in the computation from the 
start, and catalan(63) will have a VERY different value at iteration 62 
than catalan(62)...

But I can start computing a given catalan number in 128 bits and switch 
to 480 when the computation overflows.

I am using this:

https://www.geeksforgeeks.org/program-nth-catalan-number/

I "ported" that to  128 bits, then to 480. I use this as a way of 
testing my extended precision floats in the ARM 64 environment.

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-25 23:59 +0100
  Re: Catching overflow David Brown <david.brown@hesbynett.no> - 2018-02-26 00:32 +0100
    Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 01:45 +0100
  Re: Catching overflow Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-26 00:35 +0000
    Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 01:44 +0100
      Re: Catching overflow Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-26 01:25 +0000
        Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 10:53 +0100
          Re: Catching overflow Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-26 15:21 +0000
            Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 18:36 +0100
              Re: Catching overflow Ike Naar <ike@iceland.freeshell.org> - 2018-02-26 22:55 +0000
                Re: Catching overflow Tim Rentsch <txr@alumni.caltech.edu> - 2018-02-26 21:59 -0800
                Re: Catching overflow David Brown <david.brown@hesbynett.no> - 2018-02-27 09:30 +0100
                Re: Catching overflow Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-03 02:17 -0800
                Re: Catching overflow Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 03:19 -0800
                Re: Catching overflow asetofsymbols@gmail.com - 2018-03-03 03:20 -0800
                Re: Catching overflow Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 03:50 -0800
                Re: Catching overflow David Brown <david.brown@hesbynett.no> - 2018-03-04 13:48 +0100
                Re: Catching overflow asetofsymbols@gmail.com - 2018-03-04 07:11 -0800
                Re: Catching overflow Ike Naar <ike@iceland.freeshell.org> - 2018-03-11 09:21 +0000
                Re: Catching overflow Ike Naar <ike@iceland.freeshell.org> - 2018-03-11 09:26 +0000
                Re: Catching overflow Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 22:36 -0700
                Re: Catching overflow David Brown <david.brown@hesbynett.no> - 2018-03-27 15:15 +0200
                Re: Catching overflow Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-27 06:26 -0700
              Re: Catching overflow Ike Naar <ike@iceland.freeshell.org> - 2018-02-27 19:41 +0000
                Re: Catching overflow Ike Naar <ike@iceland.freeshell.org> - 2018-02-27 20:14 +0000
                Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-27 22:03 +0100
            Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 18:40 +0100
              Re: Catching overflow Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-02-26 18:31 +0000
      Re: Catching overflow Steve Carroll <frelwizzen@gmail.com> - 2018-03-01 08:45 -0800
  Re: Catching overflow bartc <bc@freeuk.com> - 2018-02-26 01:12 +0000
    Re: Catching overflow Richard Damon <Richard@Damon-Family.org> - 2018-02-25 23:10 -0500
  Catching overflow asetofsymbols@gmail.com - 2018-02-25 22:09 -0800
  Catching overflow asetofsymbols@gmail.com - 2018-02-25 23:30 -0800
    Catching overflow asetofsymbols@gmail.com - 2018-02-25 23:31 -0800
    Catching overflow asetofsymbols@gmail.com - 2018-02-28 00:03 -0800
      Catching overflow asetofsymbols@gmail.com - 2018-02-28 22:49 -0800
  Re: Catching overflow "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-02-26 23:37 +0800
    Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 18:33 +0100
      Re: Catching overflow "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-02-28 22:31 +0800
        Re: Catching overflow "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2018-02-28 22:33 +0800
      Re: Catching overflow already5chosen@yahoo.com - 2018-03-01 02:31 -0800
        Re: Catching overflow asetofsymbols@gmail.com - 2018-03-01 05:45 -0800
          Re: Catching overflow already5chosen@yahoo.com - 2018-03-01 08:24 -0800
            Re: Catching overflow asetofsymbols@gmail.com - 2018-03-01 09:03 -0800
              Re: Catching overflow Steve Carroll <frelwizzen@gmail.com> - 2018-03-01 09:32 -0800
            Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-03-01 19:47 +0100
              Re: Catching overflow already5chosen@yahoo.com - 2018-03-01 10:58 -0800
                Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-03-01 20:08 +0100
                Re: Catching overflow already5chosen@yahoo.com - 2018-03-01 11:14 -0800
                Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-03-01 20:50 +0100
                Re: Catching overflow already5chosen@yahoo.com - 2018-03-01 12:18 -0800
            Re: Catching overflow supercat@casperkitty.com - 2018-03-03 15:08 -0800
  Re: Catching overflow jladasky@itu.edu - 2018-02-26 13:07 -0800
    Re: Catching overflow jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-26 22:44 +0100

csiph-web