2.8 NF90_OPEN_PAR
This function opens a netCDF-4 dataset for parallel access.
This function is only available if the netCDF library was built with a
HDF5 library for which –enable-parallel was used, and which was
linked (like HDF5) to MPI libraries.
This opens the file using either MPI-IO or MPI-POSIX. The file must be
a netCDF-4 file. (That is, it must have been created using NF90_NETCDF4
in the creation mode).
This function is only available if netCDF-4 was build with a version
of the HDF5 library which was built with –enable-parallel.
Before either HDF5 or netCDF-4 can be installed with support for
parallel programming, and MPI layer must also be installed on the
machine, and usually a parallel file system.
NetCDF-4 exposes the parallel access functionality of HDF5. For more
information about what is required to install and use the parallel
access functions, see the HDF5 web site.
When a netCDF-4 file is opened for parallel access, collective
operations are the default. To use independent access on a variable,
See NF90_VAR_PAR_ACCESS.
Usage
function nf90_open_par(path, cmode, comm, info, ncid)
character (len = *), intent(in) :: path
integer, intent(in) :: cmode
integer, intent(in) :: comm
integer, intent(in) :: info
integer, intent(out) :: ncid
integer :: nf90_open_par
end function nf90_open_par
PATH- File name for netCDF dataset to be opened.
OMODE- A zero value (or NF90_NOWRITE) specifies the default behavior: open the
dataset with read-only access.
Otherwise, the mode may be NF90_WRITE. Setting the NF90_WRITE flag opens
the dataset with read-write access. ("Writing" means any kind of
change to the dataset, including appending or changing data, adding or
renaming dimensions, variables, and attributes, or deleting
attributes.)
Setting NF90_NETCDF4 is not necessary (or allowed). The file type is
detected automatically.
MPI_COMM- The MPI communicator.
MPI_INFO- The MPI info.
ncid- Returned netCDF ID.
Errors
NF90_OPEN returns the value NF90_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
- The specified netCDF dataset does not exist.
- A meaningless mode was specified.
- Not a netCDF-4 file.
Example
This example is from test program nf_test/f90tst_parallel.c.
! Reopen the file.
retval = nf90_open_par(FILE_NAME, nf90_nowrite, MPI_COMM_WORLD, &
MPI_INFO_NULL, ncid)
if (retval /= nf90_noerr) call handle_err(retval)
