bugGNU Scientific Library - Bugs: bug #52127, Difference between 32- vs. 64-bit...

 
 

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bug #52127: Difference between 32- vs. 64-bit versions of gsl_eigen_nonsymm

Submitted by:  Bob Smith <sudleyplace>
Submitted on:  Wed 27 Sep 2017 09:02:40 PM UTC  
 
Category:  Accuracy problem Severity:  3 - Normal
Operating System:  Windows 10 Pro (64-bit) Status:  None
Assigned to:  None Open/Closed:  Open
Release:  2.4

Wed 27 Sep 2017 09:02:40 PM UTC, original submission:

I have encountered a difference in the result of gsl_eigen_nonsymm as a 32- vs. 64-bit executable. The program is attached. What am I doing wrong?

GSL Version: 2.4
Hardware: AMD FX-8350 CPU, AUSTek Sabertooth 990FX R2.0
OS: Windows 10 Pro (64-bit)
Description:

For the 4x4 integer-valued double-precision matrix in the source file, the 32-bit executable displays results different from the 64-bit executable. I think that the 64-bit results are correct, but they are both very close.

In particular, the results differ in the both real and imaginary parts of the resulting Eigenvalues. For example, the 32-bit version returns the real parts of the four Eigenvalues as

0.9999999999999996
0.9999999999999996
1.0000000000000009
1.0000000000000009

whereas the 64-bit version returns the real parts as all exactly 1. The differences between the 32- and 64-bit results for both real and imaginary parts are all in the low-order three bits of the hexadecimal form of the double-precision result.

See the comments in the attached source file for the hexadecimal displays of the real and imaginary parts.

Bob Smith <sudleyplace>

 

Attached Files
file #41904:  nonsymm.c added by sudleyplace (6KiB - text/plain)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -email is unavailable- added by sudleyplace (Submitted the item)
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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2017-09-27 sudleyplace Attached File- => Added nonsymm.c, #41904

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