Improve efficiency in bulk water calculation

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Improve efficiency in bulk water calculation

Postby Daniel_M » Fri Dec 01, 2017 2:00 pm

Dear all,

I am making some tests with a bulk water system (128 H2O molecules, cubic cell a = 15.66 angstrom, structure obtained from classical MD at 300 K). I am interested just in single point calculations for getting energy and forces at the PBE level at gamma point only, so from what I understand the only way of improving the efficiency is playing with the parallelization at the band and fft level. I am doing the tests in a Tier-0 supercomputer but it seems to me that my calculations are very slow, compared to the same calculation with other codes (e.g. CP2K, Siesta...) in the same machine, hence I think there is something quite wrong with my setup or compilation.
First, the output of abinit -b is this:

Code: Select all
 REAL:      Data type name: REAL(DP)
            Kind value:      8
            Precision:      15
            Smallest nonnegligible quantity relative to 1:  0.22204460E-15
            Smallest positive number:                       0.22250739-307
            Largest representable number:                   0.17976931+309
 INTEGER:   Data type name: INTEGER(default)
            Kind value: 4
            Bit size:   32
            Largest representable number: 2147483647
 LOGICAL:   Data type name: LOGICAL
            Kind value: 4
 CHARACTER: Data type name: CHARACTER             Kind value: 1
  ==== Using MPI-2 specifications ====
  MPI-IO support is ON
  xmpi_tag_ub ................   2147483647
  xmpi_bsize_ch ..............            1
  xmpi_bsize_int .............            4
  xmpi_bsize_sp ..............            4
  xmpi_bsize_dp ..............            8
  xmpi_bsize_spc .............            8
  xmpi_bsize_dpc .............           16
  xmpio_bsize_frm ............            4
  xmpi_address_kind ..........            8
  xmpi_offset_kind ...........            8
  MPI_WTICK ..................   1.000000000000000E-006

 CPP options activated during the build:

                  CC_INTEL                 CXX_INTEL                  FC_INTEL
             HAVE_FC_ETIME              HAVE_FC_EXIT             HAVE_FC_FLUSH
             HAVE_FC_GAMMA            HAVE_FC_GETENV            HAVE_FC_GETPID
            HAVE_FC_SYSTEM                  HAVE_FFT        HAVE_FFT_FFTW3_MKL
              HAVE_FFT_MPI           HAVE_FFT_SERIAL        HAVE_LIBPAW_ABINIT
                  HAVE_MPI                 HAVE_MPI2       HAVE_MPI_IALLREDUCE
               HAVE_MPI_IO HAVE_MPI_TYPE_CREATE_S...             HAVE_OS_LINUX
         HAVE_TIMER_ABINIT              USE_MACROAVE                           

 === Build Information ===
  Version       : 8.6.1
  Build target  : x86_64_linux_intel17.0
  Build date    : 20171130
 === Compiler Suite ===
  C compiler       : intel17.0
  C++ compiler     : intel17.0
  Fortran compiler : intel17.0
  CFLAGS           : -mkl
  CXXFLAGS         :  -g -O2 -vec-report0
  FCFLAGS          : -mkl
  FC_LDFLAGS       :
 === Optimizations ===
  Debug level        : basic
  Optimization level : standard
  Architecture       : intel_xeon
 === Multicore ===
  Parallel build : yes
  Parallel I/O   : yes
  openMP support : no
  GPU support    : no
 === Connectors / Fallbacks ===
  Connectors on : yes
  Fallbacks on  : yes
  DFT flavor    : none
  FFT flavor    : fftw3-mkl
  LINALG flavor : mkl
  MATH flavor   : none
  TIMER flavor  : abinit
  TRIO flavor   : none
 === Experimental features ===
  Bindings            : @enable_bindings@
  Exports             : no
  GW double-precision : no

 Default optimizations:
   --- None ---

And the input (irrelevant parts abbreviated) is:

Code: Select all
atom 384
ntypat 2
znucl 8 1
typat 1 2 2 ....
ionmov 0

nstep 100
toldfe 1.0d-5

ecut 150 Ry

kptopt 0
nkpt 1
kpt 0 0 0
nband 528
paral_kgb 1
npband 48
npfft 6
fftalg 401

chksymbreak 0
acell 3*15.6626780696 angstrom
nsym 1
symrel 1 0 0 0 1 0 0 0 1
xangst  ...

Now, some observations:

- When I try using "fftalg 312", the calculation stops with "FFTW3 support not activated". This should be fixed by including the flags HAVE_FFT_FFTW3 and/or HAVE_FFT_FFTW3_THREADS when compiling, right?

- I tried with "autoparal 3", but it seems to me it is better to set manually npband and npfft. It seem also obvious that they must be such npband*npfft = total no. of cores, at least in this calculation where there are no k-points or spin involved. Am I right or am I missing something obvious?

- You may think that ecut is too high. This is bacause I am making tests to check convergence of the forces wrt the cutoff, which is not yet reached for 150 Ry. From what I know from some other codes the convergence may be improved by applying some smoothing on the density for the xc calculation (e.g. see Appendix in Jonchiere et al. JCP , 135, 154503 (2011)). Is it something similar implemented in abinit?

I will be very thankful for any comment that may help me improve this calculation. Thanks a lot,
Posts: 1
Joined: Fri Dec 01, 2017 1:17 pm

Re: Improve efficiency in bulk water calculation

Postby Annelinde » Thu Jul 26, 2018 11:12 am


I don't have a solution, but I also noticed bad scaling of the parallelisation in nanoribbons (lots of electronic bands, little kpoints) on Tier-1 and Tier-2 machines. I concluded that kpoint-parallelisation must be the most efficient in ABINIT, and when you can't make use of this kind of parallelisation, your calculation is terribly slow. I don't know why this is.

with kind regards,

Posts: 6
Joined: Tue Jul 03, 2018 2:32 pm

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