Gul Rahman wrote: > Dear All, > As I mentioned in my previous e-mail that my QE is very slow when I > run it in parallel. > I have no problem on the same machine if I use some other code, e.g., > SIESTA. > I probably missing something in my compilation of QE. Please, have a > look into the attached sys.make file that I used to compile QE. > Also, if some one can share the parallel sys.make file. > After the compilation, I just use > mpirun -np 32 --hostfile machines ./mpi_script.sh > where mpi_script.sh file just contain the command for pw.x (./pw.x < > myfile.scf.in <http://myfile.scf.in> >OUT) > Thanks, > Gul > > -- Dear Prof. Gul,
Usually good parallelization requires interaction between mpirun and quantum espresso programs (pw.x for example). pw.x mostly benefits from parallelization of fftw algorithm but there is one gotcha (because fftw is not massively parallel task). Too fine granularity of this algorithm requires too much of data transfer between nodes which in case of the low speed network (like gigabit ethernet) produces too much overhead. As a rule 4-8 parallel process in this circumstances is a ceiling. However if you job requires summation over different k-points you may introduce additional parallelization over k-points (which does not require too much of data transfer and so network bottleneck is avoided) which is done by adding command line option like pw.x -npool k ... (where k is the number of slices in k-grid). As a result the whole task consist of only 32/4=8 "fftw-parallel" processes (which is what you usually want). This information is written in the beginning of the output file. There are some other tricks to obtain further parallelization which is discussed in PW help files. But this is the most general. Best wishes, M.V.Kondrin (High Pressure Physics Institute RAS) > > > Dr. Gul Rahman > Assistant Professor, > Department of Physics, > Quaid-i-Azam University, > Islamabad, Pakistan > > http://www.qau.edu.pk/profile.php?id=818020 > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
