On 11/13/24 11:32 AM, Patrick Dupre via users wrote:
Hello,
I am not sure this issue is entirely relevant on this mailing list.
Maybe you could redirect me.
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.
(just some thoughts)
It's been a long time, but I recall that some libraries are linked in during
the build, and some (shared libraries?) are linked in at run time. Is the gsl
identical (version, size, etc.) on both machines? Is the gsl linked during the
build or at run time?
Maybe try simple math programs (a square root, a trig function, and so on),
same source code on both machines. If the answers are different, then it seems
likely to be the gsl.
Does the diff command confirm that source, makefile, and libraries are
identical? (Copy from one machine to the other, then do the diff.)
Does the diff command confirm that input data files are identical?
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