whitneyt at agcs.com
Wed Aug 1 22:05:27 CDT 2001
I am parsing mathematical models where there are LONG expressions of various
precessions, nothing too extreme. The error showed up when doing a ceiling
function. I could us sprintf in my ceiling function to fix it and use perls
math, but the error makes me a bit nervous, and considering the mathematical
nature of the project, it probably isn't a good idea anyway. Using Math:BigFloat
at least doubles the time. I saw a few modules on cpan that looked like they
might work, but I have a have the sysadmin install them for me.
EdelSys Consulting wrote:
> Why not just use sprintf to round? What kind of precision we
> talking about here?
> "Throw me a frickin' bone here, Scott"
> -- Doctor Evil
> At 04:43 PM 8/1/01 -0500, you wrote:
> > Your code is fine - the problem is just that numbers (floating point
> or otherwise) are stored in internal (binary) representation. The "extra
> digits" that you see tacked on the end are a consequence of how a floating
> point number is stored in binary format. The inconsistencies are compounded
> when you perform arithmetic operations. If you really need long floats, use
> Math::BigFloat. If it's precision you're worried about, check out
> Math::FixedPrecision. Both will be slow (compared to "straight math
> operations") due to overloading of arithmetic operators. Hope this helps.
> > - Rob
> >-----Original Message-----
> >From: Thomas Whitney [mailto:whitneyt at agcs.com]
> >Sent: Wednesday, August 01, 2001 2:16 PM
> >To: phoenix-pm-list at happyfunball.pm.org
> >Subject: Re: Phoenix.pm: Math
> >Thanks Scott,
> >Here is the problem I was having last year. Just ran it again same
> problem. I am running on v5.6.0. I don't see anything wrong that I am doing.
> >Script started on Thu Aug 17 15:57:29 2000
> >peoblej at holodeck: cat bug.pl
> >#!/usr/local/bin/perl -w
> >use strict;
> >my $result = 0.0;
> >$result = 0.07 * 10000.0;
> >printf "%40.35f\n", $result;
> >peoblej at holodeck: bug.pl
> > 700.00000000000011368683772161602973938
> >peoblej at holodeck: exit
> >script done on Thu Aug 17 15:57:44 2000
> >Scott Walters wrote:
> >> Hey Tom,
> >> Well, looking at Math::BigInt/BigFloat, they do everything in Perl by
> >> unpacking into an array from a string... something in C or Perl
> >> that minipulated it directly in its binary format would be much faster...
> >> what problems were you having with perls built in operators? Overflow?
> >> Precision? Don't know of anything offhand, and I assume you've searched
> >> CPAN... If you wanted to use a C library, Doug just did a demo on
> >> [what was that?] Embed, which makes it really easy to stick some C
> >> right in middle of your Perl.
> >> -scott
> >> On Wed, 1 Aug 2001, Thomas Whitney wrote:
> >> > Hi All,
> >> >
> >> > I am doing a lot of decimal arithmetic. I ran into problems using
> perl's standard arithmetic. Right now I am using Math::BigFloat, but it
> seems slow. Can anybody recommend a better module
> >> >
> >> > Thanks
> >> > Tom
> >> >
> >> >
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