The ABINIT Users Mailing List ( CLOSED )

[dylu@ucdavis.edu]

Dear abinit users:
     I have a question regarding the parallelization of outkss.F90, i.e., the 
program writing the KSS file for a subsequent GW calculation. My system has 8 
water moelcules placed periodically in SC cells and 32 (4*4*4) k-points are 
used for sampling. To get about 150 bands for each k-point under ecut=30 Ha, 
the partial diagonalization takes about a couple of hours (IBM AIX/power4+ 
with abinit5.1.2 or 5.2.2).
      To finish the job within the time limit of the supercomputer center (18 
hours), I was hoping to run the job in parallel. However, running 10 hours 
with 32 cpus (4 nodes) produced  wavefuncs for 4 k-points and running 18 
hours with 8 cpus (1 node) produced wavefuncs for 10 k-points. I'm kind of 
confused with the scaling of the parallelization. I did some tests using 
tgw_1.in under tests/tutorials with DATASET 1 only (KSS part, no GW, also 
setting nstep=1). With 2 cpus, the scaling is perfect. But with more, say 4, 
cpus, the scaling is pretty bad.
     I have the feeling that sending big wavefunc matrix between cpus could 
take quite some time, but it not may be the only factor. Hope people with 
more experience with MPI programming and familiar with the source code can 
give me some suggestions.
     
     Thanks
     Deyu Lu

-----------------------------INPUT 
FILE----------------------------------------
acell 3*11.732
ecut  30
ixc  11

#Definition of the atom types
ntypat 2          # There is only one type of atom
znucl 1 8           # The keyword "znucl" refers to the atomic number of the

#Definitioon of the k-point grid
kptopt  1
ngkpt   4 4 4
nshiftk 1
shiftk  0.5 0.5 0.5

istwfk     32*1
symmorphi 0
nstep 100          # Maximal number of SCF cycles
nband  34
diemac 3.5        # Although this is not mandatory, it is worth to
diemix 0.5        # function used as the standard preconditioner

prtden 1
nbandkss 150      # Number of bands in KSS file (the maximum possible)
npwkss  4457      # 14.915 Ha

#Definition of the atoms
natom 24
typat 16*1 8*2
toldfe  1.0d-8

xangst -1.770915920   1.256839825  -1.079211626
       -1.156326844   2.649702174  -1.720622083
       -1.180102192  -2.885145227  -0.015882150
        0.268978367  -2.217143196   0.420187286
        0.815634914   0.556314882   1.500261495
        0.432901744   1.858703091   2.612469201
       -1.687632397  -1.257557546   1.839956586
       -1.153134808   0.254543639   2.195829065
        0.988552101  -3.115473480  -1.580657088
        0.463591779  -2.106859074  -2.941603535
        2.721494031   2.989959718  -0.706831304
        1.837223196   2.019236764   0.195625936
        2.745692539   0.034601097  -0.228571029
        2.981538651   0.272971339   1.348134702
       -2.171870314  -0.590821640  -2.364215811
       -1.429592969  -0.888051080  -0.748716697
       -1.838512467   2.369269478  -1.016291640
       -0.728936694  -1.987319326   0.495856040
        0.167830160   0.901308139   2.252217434
       -2.021407178  -0.356002232   2.335649903
        0.335619632  -3.074532487  -2.523892064
        1.777997704   3.008397218  -0.245787912
        2.241855244   0.459793227   0.602171653
       -2.131412127  -0.322996196  -1.201685489