Dear Colleagues,
I want to enable OpenMP multithreading for the Quantum Espresso code on my multicore CPU. After doing several attempts for the compilation with ./configure --enable-openmp, there is always the message "no parallel environment detected". As a result, I am only able to activate one thread (visible in the CPU usage monitor). Even setting the "OMP_NUM_THREAD=XXX" does not bring any change.
I guess the problem lies already at the compilation stage. However, I am not experienced with openmp, only with serial QE. Is anyone able to provide general help on the issue? Has anybody the same problem?
Thanks a lot everybody for your response.
Markus
Dear All,
Problem was solved by restarting the installation routine for Cygwin and enabling the implementation of libopenmpi libraries. After ./configure it tells "parallel environment succesfully detected"!
However, by performing the PW examples, an error appears as follows:
"from allocate_fft : error # 1 wrong ngm"
I already searched in the mailing lists. Nevertheless, no solution can be found on the issue. Anybody with the same problem?
Best regards
Markus
Your configure must use appropriate flags with gcc/gofortran, i.e. anything GNU or Intel. In a bash shell, you have to export the num_threads variable. openmp does not need mpi, unless your code is hybrid.
Thanks Sanjay,
Going to configure with options and flags for compilers. Will give feedback when successful.
Dear Markus Becker,
This might be a silly question but how do you run a calculation with OpenMP? I need to run a QE calculation using OpenMP (multithreading) but not through Slurm or MPI.
Hi Roxana,
the easiest way is to use pre-compiled code of Quantum Espresso. I typically use the Cygwin environmet for MS Windows and it works quite well. Since most of the problems with OpenMP implementation arise from the compilation and ./configure stage, the pre-compiled packages can circumwent these issues. You can define the number of threads at runtime via exporting the #OMP_NUM_THREADS variable.
I hope this already helps you. Kind regards
Markus
Hello, everyone. I am facing the same issue.
In MS Windows, I can run PW with 8 threads/MPI, but for WSL Linux, I can't make it. Should I re-install it and make a different ./configure or can I do some command before calculation?
Markus Becker , could you please explain this comment?
"You can define the number of threads at runtime via exporting the #OMP_NUM_THREADS variable."
Best regards,
Ricardo Tadeu