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

[Nikhil Maroli]

Thank you very much for your reply.
Could you please tell me how to use GPU in cp2k?
I have installed all the libraries and compiled with cuda. I couldn't find
any instructions to assign GPU for the calculations.

On Fri, Sep 20, 2019, 8:15 PM Pierre Cazade <pierre.a... at gmail.com>
wrote:

> 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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