[CP2K-user] [CP2K:12238] Running Cp2k in parallel using thread in a PC

[Chn]

Hi Pierre,
I tried to combine openMP with MPI as you mentioned above when I do 
vibrational analysis. I required 6 MPI threads and got 6 output files named 
as *-r-number.out, however in each file it printed that:
 GLOBAL| Total number of message passing processes                          
   1
 GLOBAL| Number of threads for this process                                
  1
 GLOBAL| This output is from process                                       0
also I used 'top' command and found that only 6 cores were busy. 
I use 2 x 24 core processor, and set:
export OMP_NUM_THREADS=8
mpirun -n 6 /lib/CP2K/cp2k/exe/local/cp2k.popt -i project.inp -o output.out
Any suggestion will be greatly appreciated..



在 2019年9月20日星期五 UTC+8下午10:45:55，Pierre Cazade写道：
>
> Hello Nikhil,
>
> Withe command "mpirun -n 42 cp2k.pop -i inp.inp -o -out.out", you are 
> requesting 42 MPI threads and not 42 OpenMP threads. MPI usually relies on 
> replicated data which means that, for a poorly program software, it will 
> request a total amount of memory which the amount of memory required by a 
> scalar execution times the number of threads. This can very quickly become 
> problematic, in particular for QM calculations. OpenMP, however relies on 
> shared memory, the data is normally not replicated but shared between 
> threads and therefore, in an ideal scenario, the amount of memory needed 
> for 42 OpenMP threads is the same as a single one.
>
> This might explains why you calculation freezes. You are out of memory. On 
> your workstation, you should only use the executable "cp2k.ssmp" which is 
> the OpenMP version. Then you don't need the mpirun command:
>
> cp2k.ssmp -i inp.inp -o -out.out
>
> To control the number of OpenMP threads, set the env variable: 
> OMP_NUM_THREADS, e.g. in bash, export OMP_NUM_THREADS=48
>
> Now, if you need to balance between MPI and OpenMP, you should use the 
> executable named cp2k.psmp. Here is such an example:
>
> export OMP_NUM_THREADS=24
> mpirun -n 2 cp2k.psmp -i inp.inp -o -out.out
>
> In this example, I am requesting two MPI threads and each of them can use 
> up to 24 OpenMP threads.
>
> Hope this clarifies things for you.
>
> Regards,
> Pierre
>
> On 20/09/2019 14:09, Nikhil Maroli wrote:
>
> Dear all, 
>
> I have installed all the versions of CP2K in my workstation with 2 x 12 
> core processor, total thread=48
>
> I wanted to run cp2k in parallel using 42 threads, can anyone share the 
> commands that i can use.
>
> I have tried 
>
> mpirun -n 42 cp2k.pop -i inp.inp -o -out.out
>
> After this command there is a rise in memory to 100 % and the whole system 
> freezes. (i have 128GB ram).
>
> Any suggestion will be greatly appreciated,
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>
>
> -- 
> Dr Pierre Cazade, PhD
> AD3-023, Bernal Institute,
> University of Limerick,
> Plassey Park Road,
> Castletroy, co. Limerick,
> Ireland
>
>
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