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

 
 

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bug #28267: poor convergence region for gsl_sf_hyperg_1F1

Submitted by:  -Deleted Account- <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.

-Deleted Account- <bjg>
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.

-Deleted Account- <bjg>
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

-Deleted Account- <bjg>

 

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

 

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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

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