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117 lines
3.9 KiB
Fortran
117 lines
3.9 KiB
Fortran
! This is part of the netCDF package.
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! Copyright 2006 University Corporation for Atmospheric Research/Unidata.
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! See COPYRIGHT file for conditions of use.
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! This is a very simple example which writes a 2D array of sample
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! data. To handle this in netCDF we create two shared dimensions,
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! "x" and "y", and a netCDF variable, called "data". It uses
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! parallel I/O to write the file from all processors at the same
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! time.
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! This example demonstrates the netCDF Fortran 90 API. This is part
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! of the netCDF tutorial, which can be found at:
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! http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-tutorial
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! Full documentation of the netCDF Fortran 90 API can be found at:
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! http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90
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! $Id: simple_xy_par_wr.f90,v 1.3 2010/06/01 15:34:49 ed Exp $
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program simple_xy_par_wr
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use netcdf
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implicit none
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include 'mpif.h'
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! This is the name of the data file we will create.
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character (len = *), parameter :: FILE_NAME = "simple_xy_par.nc"
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! We are writing 2D data.
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integer, parameter :: NDIMS = 2
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! When we create netCDF files, variables and dimensions, we get back
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! an ID for each one.
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integer :: ncid, varid, dimids(NDIMS)
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integer :: x_dimid, y_dimid
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! These will tell where in the data file this processor should
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! write.
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integer :: start(NDIMS), count(NDIMS)
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! This is the data array we will write. It will just be filled with
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! the rank of this processor.
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integer, allocatable :: data_out(:)
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! MPI stuff: number of processors, rank of this processor, and error
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! code.
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integer :: p, my_rank, ierr
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! Loop indexes, and error handling.
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integer :: x, stat
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! Initialize MPI, learn local rank and total number of processors.
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call MPI_Init(ierr)
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call MPI_Comm_rank(MPI_COMM_WORLD, my_rank, ierr)
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call MPI_Comm_size(MPI_COMM_WORLD, p, ierr)
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! Create some pretend data. We just need one row.
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allocate(data_out(p), stat = stat)
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if (stat .ne. 0) stop 3
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do x = 1, p
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data_out(x) = my_rank
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end do
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! Create the netCDF file. The NF90_NETCDF4 flag causes a
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! HDF5/netCDF-4 file to be created. The comm and info parameters
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! cause parallel I/O to be enabled. Use either NF90_MPIIO or
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! NF90_MPIPOSIX to select between MPI/IO and MPI/POSIX.
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call check(nf90_create(FILE_NAME, IOR(NF90_NETCDF4, NF90_MPIIO), ncid, &
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comm = MPI_COMM_WORLD, info = MPI_INFO_NULL))
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! Define the dimensions. NetCDF will hand back an ID for
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! each. Metadata operations must take place on all processors.
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call check(nf90_def_dim(ncid, "x", p, x_dimid))
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call check(nf90_def_dim(ncid, "y", p, y_dimid))
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! The dimids array is used to pass the IDs of the dimensions of
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! the variables. Note that in fortran arrays are stored in
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! column-major format.
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dimids = (/ y_dimid, x_dimid /)
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! Define the variable. The type of the variable in this case is
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! NF90_INT (4-byte integer).
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call check(nf90_def_var(ncid, "data", NF90_INT, dimids, varid))
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! End define mode. This tells netCDF we are done defining
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! metadata. This operation is collective and all processors will
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! write their metadata to disk.
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call check(nf90_enddef(ncid))
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! Write the pretend data to the file. Each processor writes one row.
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start = (/ 1, my_rank + 1/)
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count = (/ p, 1 /)
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call check(nf90_put_var(ncid, varid, data_out, start = start, &
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count = count))
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! Close the file. This frees up any internal netCDF resources
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! associated with the file, and flushes any buffers.
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call check( nf90_close(ncid) )
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! Free my local memory.
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deallocate(data_out)
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! MPI library must be shut down.
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call MPI_Finalize(ierr)
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if (my_rank .eq. 0) print *, "*** SUCCESS writing example file ", FILE_NAME, "! "
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contains
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subroutine check(status)
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integer, intent ( in) :: status
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if(status /= nf90_noerr) then
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print *, trim(nf90_strerror(status))
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stop 2
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end if
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end subroutine check
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end program simple_xy_par_wr
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