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n-claes / legolas

Legolas: a modern tool for MHD spectroscopy
https://legolas.science
GNU General Public License v3.0
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Linking error on some machines due to `zggev3` #148

Closed n-claes closed 1 year ago

n-claes commented 1 year ago

Issue description

Various users have reported compilation errors in the linking step due to zggev3 not being found.

This routine is the blocked variant of zggev, used in the QZ-direct solver. The weird thing is that zggev does in fact link and works properly, whereas both routines should be standard in the LAPACK library. Other solvers are also fine. I'm unable to reproduce this locally

Bug report

Minimal example for reproduction I'm unable to reproduce this locally, it seems to depend on the machine and/or BLAS/LAPACK library versions though apparently it happens across multiple versions.

Actual result When compiling:

Undefined symbols for architecture x86_64:
  "_zggev3_", referenced from:
      ___mod_solvers_MOD_qz_direct in liblego.a(smod_qz_direct.f08.o)
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status

Expected result Proper compilation and linking.

Version info

n-claes commented 1 year ago

Users having this issue can temporarily fix it by changing zggev3 to zggev (remove the 3) in the QZ-direct solver module src/solvers/smod_qz_direct. Apply the change in line https://github.com/n-claes/legolas/blob/2dac2414c11de55d1c4fb89fd797e76e710dc956/src/solvers/smod_qz_direct.f08#L64-L67 and in line https://github.com/n-claes/legolas/blob/2dac2414c11de55d1c4fb89fd797e76e710dc956/src/solvers/smod_qz_direct.f08#L75-L78

After doing this recompilation should work until a fix has been rolled out.

eprovst commented 1 year ago

To my knowledge, zggev3 has been included in LAPACK ever since v3.6.0 (November 2015). Presumably, these users thus have a highly outdated version of LAPACK. Performance is indeed less of a concern, but zggev3 (especially in more recent versions) is in certain cases significantly more accurate than zggev, so I would try to find a different solution.

If I remember correctly, there is some logic in the build process to check for ARPACK, maybe something similar can be done to disable QZ for users with too old LAPACK versions.

Alternatively, you could sharpen the version requirements. The current recommended minimum version 3.5 will be a decade old in a few months. So putting 3.6 as bare minimum (already almost 8 years old) and the most recent release (as of writing 3.11) as recommended should ensure linking.