Public bug reported:
1. Ubuntu release
No LSB modules are available.
Description: Ubuntu 24.04.1 LTS
Release: 24.04
2. Package version
libopenblas0:
Installed: 0.3.26+ds-1
Candidate: 0.3.26+ds-1
Version table:
*** 0.3.26+ds-1 500
500 http://us.archive.ubuntu.com/ubuntu noble/universe amd64 Packages
100 /var/lib/dpkg/status
gcc-13:
Installed: 13.2.0-23ubuntu4
Candidate: 13.2.0-23ubuntu4
Version table:
*** 13.2.0-23ubuntu4 500
500 http://us.archive.ubuntu.com/ubuntu noble/main amd64 Packages
100 /var/lib/dpkg/status
3. I compiled the following c++ program with "g++ -o test_blas
test_blas.cpp -lopenblas"
#include <iostream>
#include <complex>
#include <fenv.h>
typedef std::complex<double> dcomp;
extern "C" {
void zrotg_(dcomp*, dcomp*, double*, dcomp*);
}
int main(void) {
feenableexcept(FE_INVALID |
FE_DIVBYZERO |
FE_OVERFLOW |
FE_UNDERFLOW);
dcomp ain(0.28048120941867205058,0.028460086243503417841),
bin(0.018279187257355982571,0);
double c(0.0);
dcomp s(0.0);
dcomp a=ain, b=bin;
zrotg_(&a, &b, &c, &s);
std::cout << a << " " << b << " " << c << " " << s << std::endl;
return 0;
}
Expected output:
(0.28107,0.101469) (0.0182792,0) 0.997905 (0.0643715,0.0065317)
4. What happened:
Output with -O3:
Floating point exception (core dumped)
Output with -O3 but FPE turned off:
(0.28107,inf) (0.0182792,0) 0.997905 (0.0643715,0.0065317)
This could be an issue with gcc as well, but I'm at a loss to understand
how the optimization level would affect the behavior of zrotg. I tried
to take a look in godbolt and saw that it clearly does something very
different with -O3 but I don't understand assembly very well. This
program executes successfully with -O3 and a recent Intel compiler +
MKL.
** Affects: openblas (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2083157
Title:
FPE in zrotg with g++-13 -O3
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