bugGNU Scientific Library - Bugs: bug #28267, poor convergence region for...

 
 

You are not allowed to post comments on this tracker with your current authentification level.

bug #28267: poor convergence region for gsl_sf_hyperg_1F1

Submitted by:  Brian Gough <bjg>
Submitted on:  Fri 11 Dec 2009 08:35:17 PM UTC  
 
Category: Accuracy problemSeverity: 3 - Normal
Operating System: Status: Postponed
Assigned to: NoneOpen/Closed: Open
Release: 1.13

Thu 25 Feb 2010 03:42:25 PM UTC, comment #2:

I cannot find any algorithm which handles this case.

Brian Gough <bjg>
Project Administrator
Fri 11 Dec 2009 08:36:23 PM UTC, comment #1:

It's inherently difficult to compute the value in this region either way as there is massive cancellation in both the series and the Kummer transformed series.

Brian Gough <bjg>
Project Administrator
Fri 11 Dec 2009 08:35:17 PM UTC, original submission:

The magnitude of the error is greater than the value itself for
a<<0, b>0, x>>0

gsl_sf_hyperg1F1(-3.78e+01, 2, 1.035e+02) => -7.00055e+18 +/- 3.77654e+19

-----------------------------------------------
From: Weibin Li <weibinli@mpipks-dresden.mpg.de>
To: -unavailable-
Subject: [Bug-gsl] gsl_sf_hyperg_1F1
Date: Mon, 30 Nov 2009 15:26:11 +0100

Hi, guys

I experienced bugs with gsl_sf_hyperg_1F1. The version is gsl_1.12, but
the testing is also done with gsl_1.13, using a mac with version 10.5.8
and hp-workstation with gnome_2.24.1.

#include<stdlib.h>
#include<stdio.h>
#include<math.h>
#include "gsl/gsl_sf_hyperg.h"

int main(int argc, char **argv)
{
int ii;
double Ri;
double v0;

gsl_sf_result r;
for(ii = 10; ii< 140;ii++)
{
Ri = 2013;
v0 =38.86871 +ii*2.5e-10;

gsl_sf_hyperg_1F1_e(1.0-v0,2,2.0*Ri/v0,&r);
printf("%lg\t%14.13g\t%14.13g\n",v0,r.val,r.err);

}
return 0;
}

The output of above code shows an extremely large error. by increasing
Ri, the relative error decreases. Is there any idea to fix this?

Thank you very much.

Best

Weibin

Brian Gough <bjg>
Project Administrator

 

Attached Files
file #19240:  hyperg1F1.c added by bjg (429B - text/x-csrc)

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by bjg (Submitted the item)
  •  

    Please enter the title of George Orwell's famous dystopian book (it's a date):

     

     

    Follow 2 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Thu 25 Feb 2010 03:42:25 PM UTCbjgStatusConfirmed=>Postponed
    Fri 11 Dec 2009 08:35:18 PM UTCbjgAttached File-=>Added hyperg1F1.c, #19240

    Back to the top


    Powered by Savane 3.1-cleanup