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! This is part of the netCDF package.
! Copyright 2008 University Corporation for Atmospheric Research/Unidata.
! See COPYRIGHT file for conditions of use.
! This is a simple example which reads a small dummy array, from a
! netCDF data file created by the companion program
! simple_xy_par_wr.f90. The data are read using parallel I/O.
! This program is part of the netCDF tutorial:
! http://www.unidata.ucar.edu/software/netcdf/docs/tutorial_8dox.html
! Full documentation of the netCDF Fortran 90 API can be found at:
! http://www.unidata.ucar.edu/software/netcdf/docs-fortran/f90_The-NetCDF-Fortran-90-Interface-Guide.html
! Ed Hartnett
program simple_xy_par_rd
use netcdf
implicit none
include 'mpif.h'
! This is the name of the data file we will read.
character (len = *), parameter :: FILE_NAME = "simple_xy_par.nc"
! These will tell where in the data file this processor should
! write.
integer, parameter :: NDIMS = 2
integer :: start(NDIMS), count(NDIMS)
! We will read data into this array.
integer, allocatable :: data_in(:)
! This will be the netCDF ID for the file and data variable.
integer :: ncid, varid
! MPI stuff: number of processors, rank of this processor, and error
! code.
integer :: p, my_rank, ierr
! Loop indexes, and error handling.
integer :: x, stat
! Initialize MPI, learn local rank and total number of processors.
call MPI_Init(ierr)
call MPI_Comm_rank(MPI_COMM_WORLD, my_rank, ierr)
call MPI_Comm_size(MPI_COMM_WORLD, p, ierr)
! Allocate space to read in data.
allocate(data_in(p), stat = stat)
if (stat .ne. 0) stop 3
! Open the file. NF90_NOWRITE tells netCDF we want read-only access to
! the file.
call check( nf90_open(FILE_NAME, IOR(NF90_NOWRITE, NF90_MPIIO), ncid, &
comm = MPI_COMM_WORLD, info = MPI_INFO_NULL) )
! Get the varid of the data variable, based on its name.
call check( nf90_inq_varid(ncid, "data", varid) )
! Read the data.
start = (/ 1, my_rank + 1/)
count = (/ p, 1 /)
call check( nf90_get_var(ncid, varid, data_in, &
start = start, count = count) )
! Check the data.
do x = 1, p
if (data_in(x) .ne. my_rank) then
print *, "data_in(", x, ") = ", data_in(x)
stop "Stopped"
endif
end do
! Close the file, freeing all resources.
call check( nf90_close(ncid) )
! Free my local memory.
deallocate(data_in)
! MPI library must be shut down.
call MPI_Finalize(ierr)
if (my_rank .eq. 0) print *,"*** SUCCESS reading example file ", FILE_NAME, "! "
contains
subroutine check(status)
integer, intent ( in) :: status
if(status /= nf90_noerr) then
print *, trim(nf90_strerror(status))
stop 2
end if
end subroutine check
end program simple_xy_par_rd
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