[CP2K-user] [CP2K:11393] Convergence difference with different number of pocessors for an input

[Matthias Krack]

Hi

how many CPU cores do you have available?

There are also issues with your input: (1) you set PERIODIC NONE only for 
Poisson solver, but not in the CELL section, (2) EPS_DEFAULT should be at 
least 1.0E-12, (3) you should try alternative PSOLVERs like MT or WAVELET 
instead of MULTIPOLE.

HTH

Matthias


On Friday, 8 March 2019 22:19:39 UTC+1, Mohammad Shakiba wrote:
>
> Dear Matthias Krack,
>
> As you said I added OMP_NUM_THREADS to mpirun as follows:
>
> 'mpirun -np 16 -genv OMP_NUM_THREADS 1'
>
> I did that for one thread for different number of processors 4, 16 and 32. 
> For 32 it could not perform even one OT after half an hour. The outputs of 
> the three runs done for some minutes are attached. Also, I found that the 
> version of CP2K is 7. Should I use another version?
>
>
> On Friday, March 8, 2019 at 10:47:01 PM UTC+3:30, Matthias Krack wrote:
>>
>> Hi ?
>>
>>  
>>
>> The extension “.psmp” implies that you are using an MPI and OpenMP 
>> parallel cp2k executable. Did you define the number of OpenMP threads at 
>> runtime, e.g. by setting the environment variable OMP_NUM_THREADS? OpenMP 
>> usually behaves greedy, if you do not specify the number of threads, i.e. 
>> it might create for each MPI process a number OpenMP threads equivalent to 
>> the number of available CPU cores, which will easily overload your compute 
>> node. This could explain the weird timings, but there might be other 
>> reasons as well. You will have to provide a corresponding output file, if 
>> you want to have better guesses as an answer.
>>
>>  
>>
>> Matthias
>>
>>  
>>
>> *From:* cp... at googlegroups.com <cp... at googlegroups.com> *On Behalf Of *Mohammad 
>> Shakiba
>> *Sent:* Freitag, 8. März 2019 19:43
>> *To:* cp2k <cp... at googlegroups.com>
>> *Subject:* [CP2K:11393] Convergence difference with different number of 
>> pocessors for an input
>>
>>  
>>
>> Hello everyone,
>>
>>  
>>
>> I was using CP2K 6.1.0, compiled with intel 17 and 'psmp' version, for ab 
>> initio molecular dynamics. My system contains 87 atoms containing Al, O, C 
>> and H (an MOF). I had two major questions, please help me to find their 
>> answers.
>>
>>  
>>
>> 1- When I use 16 number of processors, it takes 2.5 seconds for each OT 
>> calculation and when I use 4 processors it takes 2.9 seconds to update OT. 
>> When I put the number of processors to 20 it takes 270 seconds (about 5 
>> minutes), put it for 40 it takes 140 seconds and if I put it for 12 
>> processors it takes more than a minute for each update. My question here is 
>> just WHY? the following questions are: 
>>
>> Is there an optimum number of processors? How can I define that? When 
>> should we use a high number of processors? I have used command 'mpirun -np 
>> $nprocessors cp2k.psmp -i $input -o $output'.
>>
>>  
>>
>> 2- I used 16 number of processors and 4 number of processors. For 'mpirun 
>> -np 16', it does not converge but for 'mpirun -np 4' it converges slightly 
>> to the target convergence. I have changed the following commands but the 
>> convergence for 16 number of processors did not change. Can you explain 
>> why? What would be the solution to obtain convergence for 16 number of 
>> processors?
>>
>>  
>>
>> Thanks in advance.
>>
>>  
>>
>> I summarize the commands in the attached input file:
>>
>>  
>>
>> RUN_TYPE MD
>>
>>  
>>
>> !FORCE_EVAL
>>
>> METHOD Quickstep
>>
>>  
>>
>> !QS
>>
>> METHOD GPW 
>>
>>  
>>
>> EXTRAPOLATION ASPC 
>>
>>  
>>
>> PERIODIC NONE
>>
>>  
>>
>> PSOLVER  MULTIPOLE 
>>
>>  
>>
>> SCF_GUESS ATOMIC
>>
>>  
>>
>> EPS_SCF 1.0E-6 
>>
>>  
>>
>> PRECONDITIONER FULL_SINGLE_INVERSE ! I also used FULL_ALL
>>
>>  
>>
>> MINIMIZER DIIS ! I also used CG but it converges very slightly and 
>> sometimes there is no change in the convergence
>>
>>  
>>
>> OPTIMIZER BFGS
>>
>>  
>>
>> ENSEMBLE NVT 
>>
>>  
>>
>> TYPE NOSE
>>
>>  
>>
>>  
>>
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>
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