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gsl/gcc


From: Patrick Dupre
Subject: gsl/gcc
Date: Wed, 13 Nov 2024 20:08:54 +0100

Hello,

The same application (relatively heavy code), provides different values when it
is run and compiled on 2 different machines.
Both F40 (last update)
gcc (GCC) 14.2.1 20240912 (Red Hat 14.2.1-3)
One
Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz
The other one
Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
Actually, this happens when I use the gsl library.
gsl-devel-2.7.1-8.fc40.x86_64
for integration (gsl_integration_cquad).
Before integration, the values are strictly identical.
The same Makefile is used.
Now, if I copy the code generated by the machine A on machine B,
I get the same results as it had been run on machine A.
The size of both codes are slightly different.
I conclude that the issue is due to the compiler.
Indeed, the difference in the generated values seems pretty constant,
i.e., it seems proportional to the value itself: of the order 2.7e-8 (relative 
difference)
i.e. a lot higher than the accuracy of the machine: < 1e-35.

Which one is the good one?
Why this behavior?
Can I solve the issue?

Thank for any help.

===========================================================================
 Patrick DUPRÉ                                 | | email: pdupre@gmx.com
===========================================================================




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