Personal tools
You are here: Home Documentation Help files for v7.0 input_variables PARALLELISATION variables.


ABINIT parallelisation input variables:

List and description.


This document lists and provides the description of the name (keywords) of parallelisation input variables to be used in the main input file of the abinit code.

The new user is advised to read first the new user's guide, before reading the present file. It will be easier to discover the present file with the help of the tutorial.

When the user is sufficiently familiarized with ABINIT, the reading of the ~abinit/doc/users/tuning file might be useful. For response-function calculations using abinit, please read the response function help file

Copyright (C) 1998-2012 ABINIT group (DCA, XG, RC)
This file is distributed under the terms of the GNU General Public License, see ~abinit/COPYING or http://www.gnu.org/copyleft/gpl.txt .
For the initials of contributors, see ~abinit/doc/developers/contributors.txt .

Content of the file : alphabetical list of variables.


A.
B.
C.
D.
E.
F.
G. gwpara  
H.
I.
J.
K.
L. localrdwf  
M.
N. npband   npfft   npimage   npkpt   nppert   npspinor  
O.
P. paral_atom   paral_kgb   paral_rf  
Q.
R.
S.
T.
U. use_gpu_cuda  
V.
W.
X.
Y.
Z.





gwpara
Mnemonics: GW PARAllelization level
Characteristic: GW, PARALLEL
Variable type: integer
Default is 1 TODO: default should be 2.

Only relevant if optdriver=3 or 4, that is, screening or sigma calculations.

gwpara is used to choose between the two different parallelization levels available in the GW code. The available options are:

  • =1 => parallelisation on k points
  • =2 => parallelisation on bands

Additional notes:
In the present status of the code, only the parallelization over bands (gwpara=2) allows to reduce the memory allocated by each processor.
Using gwpara=1, indeed, requires the same amount of memory as a sequential run, irrespectively of the number of CPU's used.

A reduction of the requireed memory can be achieved by opting for an out-of-core solution (mkmem=0, only coded for optdriver=3) at the price of a drastic worsening of the performance.



Go to the top | Complete list of input variables



localrdwf
Mnemonics: LOCAL ReaD WaveFunctions
Characteristic: DEVELOP, PARALLEL
Variable type: integer
Default is 1.

This input variable is used only when running abinit in parallel. If localrdwf=1, the input wavefunction disk file or the KSS/SCR file in case of GW calculations, is read locally by each processor, while if localrdwf=0, only one processor reads it, and broadcast the data to the other processors.

The option localrdwf=0 is NOT allowed when parallel I/O are activated (MPI-IO access), i.e. when accesswff==1.

The option localrdwf=0 is NOT allowed when mkmem==0 (or, for RF, when mkqmem==0, or mk1mem==0), that is, when the wavefunctions are stored on disk. This is still to be coded ...

In the case of a parallel computer with a unique file system, both options are as convenient for the user. However, if the I/O are slow compared to communications between processors, (e.g. for CRAY T3E machines), localrdwf=0 should be much more efficient; if you really need temporary disk storage, switch to localrdwf=1 ).

In the case of a cluster of nodes, with a different file system for each machine, the input wavefunction file must be available on all nodes if localrdwf=1, while it is needed only for the master node if localrdwf=0.



Go to the top | Complete list of input variables



npband
Mnemonics: Number of Processors at the BAND level
Characteristic:
Variable type: integer
Default is 1.

Relevant only for the band/FFT parallelisation (see the paral_kgb input variable).
npband gives the number of processors among which the work load over the band level is shared. npband, npfft, npkpt and npspinor are combined to give the total number of processors (nproc) working on the band/FFT/k-point parallelisation.
See npfft, npkpt, npspinor and paral_kgb for the additional information on the use of band/FFT/k-point parallelisation.

Note : at present, npband has to be a divisor or equal to nband



Go to the top | Complete list of input variables



npfft
Mnemonics: Number of Processors at the FFT level
Characteristic:
Variable type: integer
Default is nproc.

Relevant only for the band/FFT/k-point parallelisation (see the paral_kgb input variable).
npfft gives the number of processors among which the work load over the FFT level is shared. npfft, npkpt, npband and npspinor are combined to give the total number of processors (nproc) working on the band/FFT/k-point parallelisation.
See npband, npkpt, npspinor, and paral_kgb for the additional information on the use of band/FFT/k-point parallelisation.

Note : ngfft is automatically adjusted to npfft. If the number of processor is changed from a calculation to another one, npfft may change, and then ngfft also.



Go to the top | Complete list of input variables



npimage
Mnemonics: Number of Processors at the IMAGE level
Characteristic:
Variable type: integer
Default is min(nproc,ndynimage) (see below).

Relevant only when sets of images are activated (see imgmov and nimage.
npimage gives the number of processors among which the work load over the image level is shared. It is compatible with all other parallelization levels available for ground-state calculations.
Note on the npimage default value: this default value is crude. It is set to the number of dynamic images (ndynimage) if the number of available processors allows this choice. If ntimimage=1, npimage is set to min(nproc,nimage).


See paral_kgb, npkpt, npband, npfft and npspinor for the additional information on the use of k-point/band/FFT parallelisation.





Go to the top | Complete list of input variables



npkpt
Mnemonics: Number of Processors at the K-Point Level
Characteristic:
Variable type: integer
Default is 1.

Relevant only for the band/FFT/k-point parallelisation (see the paral_kgb input variable).
npkpt gives the number of processors among which the work load over the k-point/spin-component level is shared. npkpt, npfft, npband and npspinor are combined to give the total number of processors (nproc) working on the band/FFT/k-point parallelisation.
See npband, npfft, npspinor and paral_kgb for the additional information on the use of band/FFT/k-point parallelisation.

Note : npkpt should be a divisor or equal to with the number of k-point/spin-components (nkpt*nsppol) in order to have the better load-balancing and efficiency.




Go to the top | Complete list of input variables



nppert
Mnemonics: Number of Processors at the PERTurbation level
Characteristic: can even be specified separately for each dataset, parameter paral_rf is necessary
Variable type: integer
Default is 1.

This parameter is used in connection to the parallelization over perturbations(see paral_rf ), for a linear response calculation. nppert gives the number of processors among which the work load over the perturbation level is shared.




Go to the top | Complete list of input variables



npspinor
Mnemonics: Number of Processors at the SPINOR level
Characteristic:
Variable type: integer
Default is 1.

Can be 1 or 2 (if nspinor=2).
Relevant only for the band/FFT/k-point parallelisation (see the paral_kgb input variable).
npspinor gives the number of processors among which the work load over the spinorial components of wave-functions is shared. npspinor, npfft, npband and npkpt are combined to give the total number of processors (nproc) working on the band/FFT/k-point parallelisation.
See npkpt, npband, npfft, and paral_kgb for the additional information on the use of band/FFT/k-point parallelisation.




Go to the top | Complete list of input variables



paral_atom
Mnemonics: activate PARALelization over (paw) ATOMic sites
Characteristic:
Variable type: integer
Default is 0.

Relevant only for PAW calculations.
This keyword controls the parallel distribution of memory over atomic sites. Calculations are also distributed using the "kpt-band" communicator.
Warning: use of paral_atom is highly experimental.
Only compatible (for the moment) with ground-state calculations.




Go to the top | Complete list of input variables



paral_kgb
Mnemonics: activate PARALelization over K-point, G-vectors and Bands
Characteristic:
Variable type: integer
Default is 0.

If paral_kgb is not explicitely put in the input file, ABINIT automatically detects if the job has been sent in sequential or in parallel. In this last case, it detects the number of processors on which the job has been sent and calculates values of npkpt, npfft, npband, bandpp ,npimage and npspinor that are compatible with the number of processors. It then set paral_kgb to 0 or 1 (see hereunder)and launches the job.

If paral_kgb=0, the parallelization over k-points only is activated. In this case, npkpt, npfft and npband are ignored. Require compilation option --enable-mpi="yes".

If paral_kgb=1, the parallelization over bands, FFTs, and k-point/spin-components is activated (see npkpt, npfft and npband). With this parallelization, the work load is split over three levels of parallelization. The different communications almost occur along one dimension only. Require compilation option --enable-mpi="yes".

HOWTO fix the number of processors along one level of parallelisation:
At first, try to parallelise over the k point and spin (see npkpt). Otherwise, for unpolarized calculation at the gamma point, parallelise over the two other levels: the band and FFT ones. For nproc<=50, the best speed-up is achieved for npband=nproc and npfft=1 (which is not yet the default). For nproc>=50, the best speed-up is achieved for npband >=4*npfft.

For additional information, download F. Bottin's presentation at the ABINIT workshop 2007

Suggested acknowledgments :
F. Bottin, S. Leroux, A. Knyazev and G. Zerah, Large scale ab initio calculations based on three levels of parallelization, Comput. Mat. Science 42, 329 (2008), available on arXiv, http://arxiv.org/abs/0707.3405 .

If the total number of processors used is compatible with the three levels of parallelization, the values for npband, npfft, npband and bandpp will be filled automatically, although the repartition may not be optimal. To optimize the repartition use:

If paral_kgb=-n , ABINIT will test automatically if all the processor numbers between 2 and n are convenient for a parallel calculation and print the possible values in the log file. A weight is attributed to each possible processors repartition. It is adviced to select a processor repartition the weight of which is close to 1. The code will then stop after the printing. This test can be done as well with a sequential as with a parallel version of the code. The user can then choose the adequate number of processor on which he can run his job. He must put again paral_kgb=1 in the input file and put the corresponding values for npband, npfft, npband and bandpp in the input file.



Go to the top | Complete list of input variables



paral_rf
Mnemonics: activate PARALlelization over Response Function perturbations
Characteristic: can even be specified separately for each dataset
Variable type: integer
Default is 0.

This parameter activates the parallelization over perturbations which can be used during RF-Calculation. It is possible to use this type of parallelization in combination to the parallelization over k-points.

Currently total energies calculated by groups, where the master process is not in, are saved in .status_LOGxxxx files.





Go to the top | Complete list of input variables

use_gpu_cuda
Mnemonics: activate USE of GPU accelerators with CUDA (nvidia)
Characteristic:
Variable type: integer
Default is 1 for ground-state calculations (optdriver=0) when ABINIT has been compiled using cuda, 0 otherwise

Only available if ABINIT executable has been compiled with cuda nvcc compiler.
This parameter activates the use of NVidia graphic accelerators (GPU) if present.
If use_gp_cuda=1, some parts of the computation are transmitted to the GPUs.
If use_gp_cuda=1, no computation is done on GPUs, even if present.

Note that, while running ABINIT on GPUs, it is recommended to use MAGMA external library (i.e. Lapack on GPUs). The latter is activated during compilation stage (see "configure" step of ABINIT compilation process). If MAGMA is not used, ABINIT performances on GPUs can be poor.



Go to the top | Complete list of input variables