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[Bug-gsl] [bug #28267] poor convergence region for gsl_sf_hyperg_1F1


From: Brian Gough
Subject: [Bug-gsl] [bug #28267] poor convergence region for gsl_sf_hyperg_1F1
Date: Fri, 11 Dec 2009 20:35:19 +0000
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.9.0.11) Gecko/2009061118 Fedora/3.0.11-1.fc9 Firefox/3.0.11

URL:
  <http://savannah.gnu.org/bugs/?28267>

                 Summary: poor convergence region for gsl_sf_hyperg_1F1
                 Project: GNU Scientific Library
            Submitted by: bjg
            Submitted on: Fri 11 Dec 2009 08:35:17 PM GMT
                Category: Accuracy problem
                Severity: 3 - Normal
        Operating System: 
                  Status: Confirmed
             Assigned to: None
             Open/Closed: Open
                 Release: 1.13
         Discussion Lock: Any

    _______________________________________________________

Details:

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 <address@hidden>
To: address@hidden
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





    _______________________________________________________

File Attachments:


-------------------------------------------------------
Date: Fri 11 Dec 2009 08:35:18 PM GMT  Name: hyperg1F1.c  Size: 429B   By:
bjg

<http://savannah.gnu.org/bugs/download.php?file_id=19240>

    _______________________________________________________

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  <http://savannah.gnu.org/bugs/?28267>

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