[petsc-users] [Ext] Re: Two simple questions on building

[Ernesto Prudencio]

Thanks, Matt.

Regarding the blas/lapack used by PETSc via the -download-fblaslapack configuration option: are the libraries consumed as .a or as .so?

My question was related to the situation where they would be .so, with my LD_LIBRARY_PATH pointing first to the MKL path and then to the PETSc path. Would that cause PETSc to use the blas/lapack from MKL at run time, instead of the blas/lapack use at compilation time?

Regarding your question on (a): at the end of the PETSc building process, a docker image has to be created, but then there are some soft links in the supplied MKL library which are not resolved. The problem boils down to details on where the MKL is actually located, and the overall compilation environment used for all software, where certain rules have to be enforced for all.

Cheers,

Ernesto.

From: Matthew Knepley <knepley at gmail.com>
Sent: Wednesday, March 16, 2022 5:45 AM
To: Ernesto Prudencio <EPrudencio at slb.com>
Cc: PETSc users list <petsc-users at mcs.anl.gov>
Subject: [Ext] Re: [petsc-users] Two simple questions on building

On Wed, Mar 16, 2022 at 1:04 AM Ernesto Prudencio via petsc-users <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>> wrote:
Hi.

I have an application that uses MKL for some convolution operations. Such MKL functionality uses, I suppose, BLAS/LAPACK underneath.

This same application of mine also uses PETSc for other purposes. I can supply blas and lapack to PETSc in two ways:

  1.  Using the configuration option--with-blaslapack-lib="-L${MKL_DIR}/lib/intel64 -lfile1 -lfile2 ... ".  For reasons related to compilation environments + docker images + cloud, I am having issues with this option (a) _after_ PETSc builds successfully (both make and make install work fine).
  2.  Using the configuration option --download-fblaslapack=yes. This options works fine for the purpose of generating my application executable.

If I use option (b), I understand that I will have two different blas/lapack codes available during the execution of my application: one from MKL, the other being the one that PETSc downloads during its configuration.

Question 1) Do you foresee any potential run time issue with option (b)?

All those BLAS/LAPACK functions have the same name. If MKL does something slightly different in one, you could have problems. The annoying thing is that it will probably work 99% of the time.

What problem do you have with a)?

Question 2) In the case PETSc, is there any problem if run "make" and "make install" without specifying PETSC_ARCH?

It will choose an ARCH if you do not specify one.

  Thanks,

     Matt


Thank you in advance,

Ernesto.


Schlumberger-Private


--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/<https://urldefense.com/v3/__http:/www.cse.buffalo.edu/*knepley/__;fg!!Kjv0uj3L4nM6H-I!1YIcv0EOPSK_loLVyLJiARQF8B0wUp96gOBWK4L-7PdpPbhDZIEQPSkoe3a2pw$>


Schlumberger-Private
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20220316/ebe31fd7/attachment-0001.html>