Yambo Community Forum

Dear YAMBO,

Can you provide me some tips for BSE kernel parallelization. I followed some variables of BSE parallel

BS_CPU= "47 1 28" # [PARALLEL] CPUs for each role
BS_ROLEs= "k eh t" # [PARALLEL] CPUs roles (k,eh,t)
BS_nCPU_LinAlg_INV= 8 # [PARALLEL] CPUs for matrix inversion
BS_nCPU_LinAlg_DIAGO= 8 # [PARALLEL] CPUs for matrix diagonalization

but it doesn't work. Looking at output file, these configurations were not taken into account.

Another question is which parallelism gives memory distribution. It seems that this calculation requires a lot of memory.

I attached here input and output files. Thank you.

Dear Viet-Anh Ha,,

please note that parallel linear algebra will be not in place if you do not compile the code using SCALAPACK libraries: Anyway this are need for the diagoalization of the BSE matrix, while you are experiencing problems in the building of the kernel.

Why do you say that BS_CPU and BS_ROLEs are not taken into account? The parallel distribution of the kernel is reported in the log files.
You have a lot of k points (1000 in the BZ) so you can easily end up with very large matrices I really suggest you to reduce the number of bands in BSE. The first band is around 41 eV below the Fermi level, this will not participate in the first excitations ie in the low energy part of the spectrum.
Also, the last bands 16/17/18 are 40eV above the Fermi energy. I would reduce drastically the range of bands in the BSE, this will reduce a lot the computational burden.
Best,
Daniele

Thank you Daniele.

I did not pay attention to log files and didn't recognize that parallel was performed. I just looked at the beginning of output file with the following text

* CPU-Threads :1316(CPU)-1(threads)-1(threads@X)-1(threads@DIP)-1(threads@SE)-1(threads@RT)-1(threads@K)-1(threads@NL)
* MPI CPU : 1316
* THREADS (max): 1
* THREADS TOT(max): 1316
* I/O NODES : 1
* Fragmented WFs :yes

so I thought the parallelization was not successfully.

Another question is why NLogCPUs does not work in this run. I set NLogCPUs = 2 but there are still a number of log files written (=number of MPIs).

Dear Viet-Anh Ha,

Another question is why NLogCPUs does not work in this run. I set NLogCPUs = 2 but there are still a number of log files written (=number of MPIs).

That's strange, are you sure that there are no logs from previous runs? These are not deleted, and an incremental number is used *_01 etc is used for new ones.
Finally, I can see you are using a rather old version of Yambo ( GPL Version 4.4.0), I suggest you to update to a newer version.
Best,
Daniele

I tried to delete log files in LOG directory but still see the same problem. Yes, I'll update the newest version.