bugGNU Scientific Library - Bugs: bug #25320, Import fresnel, bugs on GSL...

 
 

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bug #25320: Import fresnel, bugs on GSL Extension Fresnel

Submitter:  -Deleted Account- <bjg>
Submitted:  Wed 14 Jan 2009 05:41:30 PM UTC
   
 
Category:  Accuracy problem Severity:  3 - Normal
Operating System:  Status:  None
Assigned to:  None Open/Closed:  Open
Release:  1.12

Wed 14 Jan 2009 05:41:30 PM UTC, original submission:  

The fresnel extension should be imported for the next release, with the following bug report checked.

From: "Toshiro Ohsaki" <t.ohsaki@ipb.co.jp>
To: <bug-gsl@gnu.org>
Subject: [Bug-gsl] Bugs on GSL Extension Fresnel
Date: Wed, 26 Nov 2008 21:07:02 +0900

Dear staff of GNU


  I found bugs on GSL Extensions/Applications Fresnel by Andrew Steiner.
 This program does not return a correct value, if x is negative.

The original function fresnel_c is coded as,

double fresnel_c(double x)
{
  double xx = x*x*pi_2;
  double ret_val;
  if(xx<=8.0)
   ret_val = fresnel_cos_0_8(xx);
  else
   ret_val = fresnel_cos_8_inf(xx);
  return (x<0.0) ? -ret_val : ret_val;
}
.

 I think it should be coded as,

double fresnel_c(double x)
{
  double xx = x*x*pi_2;
  double ret_val;
  double sign;

  if(xx < 0.0){
    xx*=-1.0;
    sign=-1.0;
  }
  else{
    sign=1.0;
  }

  if(xx<=8.0)
   ret_val = fresnel_cos_0_8(xx);
  else
   ret_val = fresnel_cos_8_inf(xx);

  ret_val*=sign;

  return(ret_val);
}
.

The same correction should be done on the function fresnel_s.

Sincerely yours,
Toshiro Ohsaki
from Tokyo Japan.
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-Deleted Account- <bjg>

 

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