GNU 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
Submitter: | Bob Smith <sudleyplace> | ||
Submitted: | 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 |
Attached Files
Depends on the following items: None found
Items that depend on this one: None found
Carbon-Copy List
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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Corresponding source code
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.