Unidata · jswhit · Mar 22, 2019 · Mar 19, 2019 · Mar 19, 2019 · Mar 19, 2019
diff --git a/.travis.yml b/.travis.yml
@@ -53,6 +53,23 @@ matrix:
             - mpich
             - libmpich-dev
             - libhdf5-mpich-dev
+    # test MPI with latest released version
+    - python: 3.7
+      dist: xenial
+      env: 
+        - MPI=1
+        - CC=mpicc.mpich
+        - DEPENDS="numpy>=1.9.0 cython>=0.21 setuptools>=18.0 mpi4py>=1.3.1 cftime"
+        - NETCDF_VERSION=4.6.3
+        - PNETCDF_VERSION=1.11.0
+        - NETCDF_DIR=$HOME
+        - PATH=${NETCDF_DIR}/bin:${PATH} # pick up nc-config here
+      addons:
+        apt:
+          packages:
+            - mpich
+            - libmpich-dev
+            - libhdf5-mpich-dev
     # test with netcdf-c from github master
     - python: 3.7
       dist: xenial
@@ -86,6 +103,8 @@ script:
   - cd test
   - python run_all.py
   - |
+    echo "MPI = ${MPI}"
+    echo "PNETCDF_VERSION = ${PNETCDF_VERSION}"
     if [ $MPI -eq 1 ] ; then
        cd ../examples
        mpirun.mpich -np 4 python mpi_example.py
@@ -94,6 +113,14 @@ script:
          exit 1
        else
          echo "mpi test passed!"
-         exit 0
+       fi
+       if [ -n "${PNETCDF_VERSION}" ] ; then
+          mpirun.mpich -np 4 python mpi_example.py NETCDF3_64BIT_DATA
+          if [ $? -ne 0 ] ; then
+            echo "PnetCDF mpi test failed!"
+            exit 1
+          else
+            echo "PnetCDF mpi test passed!"
+          fi
        fi
     fi
diff --git a/Changelog b/Changelog
@@ -1,3 +1,8 @@
+ current master
+===============
+ * added support for parallel IO in the classic netcdf-3 formats through the
+   pnetcdf library.
+
  version 1.4.3.2 (tag v1.4.3.2)
 ===============================
  * include missing membuf.pyx file in release source tarball.

diff --git a/ci/travis/build-parallel-netcdf.sh b/ci/travis/build-parallel-netcdf.sh
@@ -2,8 +2,19 @@
 
 set -e
 
-echo "Using downloaded netCDF version ${NETCDF_VERSION} with parallel capabilities enabled"
 pushd /tmp
+if [ -n "${PNETCDF_VERSION}" ]; then
+	echo "Using downloaded PnetCDF version ${PNETCDF_VERSION}"
+	wget https://parallel-netcdf.github.io/Release/pnetcdf-${PNETCDF_VERSION}.tar.gz
+	tar -xzf pnetcdf-${PNETCDF_VERSION}.tar.gz
+	pushd pnetcdf-${PNETCDF_VERSION}
+	./configure --prefix $NETCDF_DIR --enable-shared --disable-fortran --disable-cxx
+	NETCDF_EXTRA_CONFIG="--enable-pnetcdf"
+	make -j 2
+	make install
+	popd
+fi
+echo "Using downloaded netCDF version ${NETCDF_VERSION} with parallel capabilities enabled"
 if [ ${NETCDF_VERSION} == "GITMASTER" ]; then
    git clone http://github.com/Unidata/netcdf-c netcdf-c
    pushd netcdf-c
@@ -14,9 +25,10 @@ else
    pushd netcdf-c-${NETCDF_VERSION}
 fi
 # for Ubuntu xenial
-export CPPFLAGS="-I/usr/include/hdf5/mpich"
+export CPPFLAGS="-I/usr/include/hdf5/mpich -I${NETCDF_DIR}/include"
+export LDFLAGS="-L${NETCDF_DIR}/lib"
 export LIBS="-lhdf5_mpich_hl -lhdf5_mpich -lm -lz"
-./configure --prefix $NETCDF_DIR --enable-netcdf-4 --enable-shared --disable-dap --enable-parallel
+./configure --prefix $NETCDF_DIR --enable-netcdf-4 --enable-shared --disable-dap --enable-parallel4 $NETCDF_EXTRA_CONFIG
 make -j 2
 make install
 popd
diff --git a/examples/mpi_example.py b/examples/mpi_example.py
@@ -1,10 +1,17 @@
 # to run: mpirun -np 4 python mpi_example.py
+import sys
 from mpi4py import MPI
 import numpy as np
 from netCDF4 import Dataset
+if len(sys.argv) == 2:
+	format = sys.argv[1]
+else:
+	format = 'NETCDF4_CLASSIC'
 rank = MPI.COMM_WORLD.rank  # The process ID (integer 0-3 for 4-process run)
+if rank == 0:
+	print('Creating file with format {}'.format(format))
 nc = Dataset('parallel_test.nc', 'w', parallel=True, comm=MPI.COMM_WORLD,
-        info=MPI.Info(),format='NETCDF4_CLASSIC')
+        info=MPI.Info(),format=format)
 # below should work also - MPI_COMM_WORLD and MPI_INFO_NULL will be used.
 #nc = Dataset('parallel_test.nc', 'w', parallel=True)
 d = nc.createDimension('dim',4)

diff --git a/include/netCDF4.pxi b/include/netCDF4.pxi
@@ -51,6 +51,7 @@ cdef extern from "netcdf.h":
         NC_CLOBBER
         NC_NOCLOBBER # Don't destroy existing file on create 
         NC_64BIT_OFFSET # Use large (64-bit) file offsets 
+        NC_64BIT_DATA # Use cdf-5 format 
         NC_NETCDF4 # Use netCDF-4/HDF5 format 
         NC_CLASSIC_MODEL # Enforce strict netcdf-3 rules. 
         # Use these 'mode' flags for both nc_create and nc_open.
@@ -703,7 +704,7 @@ IF HAS_NC_CREATE_MEM:
             int flags
         int nc_close_memio(int ncid, NC_memio* info);
 
-IF HAS_NC_PAR:
+IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
     cdef extern from "mpi-compat.h": pass
     cdef extern from "netcdf_par.h":
         ctypedef int MPI_Comm

diff --git a/netCDF4/__init__.py b/netCDF4/__init__.py
@@ -6,6 +6,7 @@
 from ._netCDF4 import (__version__, __netcdf4libversion__, __hdf5libversion__,
                        __has_rename_grp__, __has_nc_inq_path__,
                        __has_nc_inq_format_extended__, __has_nc_open_mem__,
-                       __has_nc_create_mem__,__has_cdf5_format__,__has_nc_par__)
+                       __has_nc_create_mem__, __has_cdf5_format__,
+                       __has_parallel4_support__, __has_pnetcdf_support__)
 __all__ =\
 ['Dataset','Variable','Dimension','Group','MFDataset','MFTime','CompoundType','VLType','date2num','num2date','date2index','stringtochar','chartostring','stringtoarr','getlibversion','EnumType']
diff --git a/netCDF4/_netCDF4.pyx b/netCDF4/_netCDF4.pyx
@@ -63,9 +63,10 @@ Requires
  If you want [OPeNDAP](http://opendap.org) support, add `--enable-dap`.
  If you want HDF4 SD support, add `--enable-hdf4` and add
  the location of the HDF4 headers and library to `$CPPFLAGS` and `$LDFLAGS`.
- - for MPI parallel IO support, MPI-enabled versions of the HDF5 and netcdf
- libraries are required, as is the [mpi4py](http://mpi4py.scipy.org) python
- module.
+ - for MPI parallel IO support, an MPI-enabled versions of the netcdf library
+ is required, as is the [mpi4py](http://mpi4py.scipy.org) python module.
+ Parallel IO further depends on the existence of MPI-enabled HDF5 or the
+ [PnetCDF](https://parallel-netcdf.github.io/) library.
 
 
 Install
@@ -918,13 +919,14 @@ specified names.
 
 ## <div id='section13'>13) Parallel IO.
 
-If MPI parallel enabled versions of netcdf and hdf5 are detected, and
-[mpi4py](https://mpi4py.scipy.org) is installed, netcdf4-python will
-be built with parallel IO capabilities enabled.  Since parallel IO
-uses features of HDF5, it can only be used with NETCDF4 or 
-NETCDF4_CLASSIC formatted files. To use parallel IO,
-your program must be running in an MPI environment using
-[mpi4py](https://mpi4py.scipy.org).
+If MPI parallel enabled versions of netcdf and hdf5 or pnetcdf are detected,
+and [mpi4py](https://mpi4py.scipy.org) is installed, netcdf4-python will
+be built with parallel IO capabilities enabled. Parallel IO of NETCDF4 or 
+NETCDF4_CLASSIC formatted files is only available if the MPI parallel HDF5
+library is available. Parallel IO of classic netcdf-3 file formats is only
+available if the [PnetCDF](https://parallel-netcdf.github.io/) library is
+available. To use parallel IO, your program must be running in an MPI
+environment using [mpi4py](https://mpi4py.scipy.org).
 
     :::python
     >>> from mpi4py import MPI
@@ -971,9 +973,12 @@ participate in doing IO. To toggle back and forth between
 the two types of IO, use the `netCDF4.Variable.set_collective`
 `netCDF4.Variable`method. All metadata
 operations (such as creation of groups, types, variables, dimensions, or attributes)
-are collective.  There are a couple of important limitatons of parallel IO:
+are collective.  There are a couple of important limitations of parallel IO:
 
- - only works with NETCDF4 or NETCDF4_CLASSIC formatted files.
+ - parallel IO for NETCDF4 or NETCDF4_CLASSIC formatted files is only available
+   if the netcdf library was compiled with MPI enabled HDF5.
+ - parallel IO for all classic netcdf-3 file formats is only available if the
+   netcdf library was compiled with PnetCDF.
  - If a variable has an unlimited dimension, appending data must be done in collective mode.
    If the write is done in independent mode, the operation will fail with a
    a generic "HDF Error".
@@ -1202,7 +1207,7 @@ import_array()
 include "constants.pyx"
 include "membuf.pyx"
 include "netCDF4.pxi"
-IF HAS_NC_PAR:
+IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
     cimport mpi4py.MPI as MPI
     from mpi4py.libmpi cimport MPI_Comm, MPI_Info, MPI_Comm_dup, MPI_Info_dup, \
                                MPI_Comm_free, MPI_Info_free, MPI_INFO_NULL,\
@@ -1240,7 +1245,8 @@ __has_nc_inq_format_extended__ = HAS_NC_INQ_FORMAT_EXTENDED
 __has_cdf5_format__ = HAS_CDF5_FORMAT
 __has_nc_open_mem__ = HAS_NC_OPEN_MEM
 __has_nc_create_mem__ = HAS_NC_CREATE_MEM
-__has_nc_par__ = HAS_NC_PAR
+__has_parallel4_support__ = HAS_PARALLEL4_SUPPORT
+__has_pnetcdf_support__ = HAS_PNETCDF_SUPPORT
 _needsworkaround_issue485 = __netcdf4libversion__ < "4.4.0" or \
                (__netcdf4libversion__.startswith("4.4.0") and \
                 "-development" in __netcdf4libversion__)
@@ -1282,20 +1288,29 @@ _intnptonctype  = {'i1' : NC_BYTE,
 _format_dict  = {'NETCDF3_CLASSIC' : NC_FORMAT_CLASSIC,
                  'NETCDF4_CLASSIC' : NC_FORMAT_NETCDF4_CLASSIC,
                  'NETCDF4'         : NC_FORMAT_NETCDF4}
+# create dictionary mapping string identifiers to netcdf create format codes
+_cmode_dict  = {'NETCDF3_CLASSIC' : NC_CLASSIC_MODEL,
+                'NETCDF4_CLASSIC' : NC_CLASSIC_MODEL | NC_NETCDF4,
+                'NETCDF4'         : NC_NETCDF4}
 IF HAS_CDF5_FORMAT:
     # NETCDF3_64BIT deprecated, saved for compatibility.
     # use NETCDF3_64BIT_OFFSET instead.
     _format_dict['NETCDF3_64BIT_OFFSET'] = NC_FORMAT_64BIT_OFFSET
     _format_dict['NETCDF3_64BIT_DATA'] = NC_FORMAT_64BIT_DATA
+    _cmode_dict['NETCDF3_64BIT_OFFSET'] = NC_64BIT_OFFSET
+    _cmode_dict['NETCDF3_64BIT_DATA'] = NC_64BIT_DATA
 ELSE:
     _format_dict['NETCDF3_64BIT'] = NC_FORMAT_64BIT
+    _cmode_dict['NETCDF3_64BIT'] = NC_64BIT_OFFSET
 # invert dictionary mapping
 _reverse_format_dict = dict((v, k) for k, v in _format_dict.iteritems())
 # add duplicate entry (NETCDF3_64BIT == NETCDF3_64BIT_OFFSET)
 IF HAS_CDF5_FORMAT:
     _format_dict['NETCDF3_64BIT'] = NC_FORMAT_64BIT_OFFSET
+    _cmode_dict['NETCDF3_64BIT'] = NC_64BIT_OFFSET
 ELSE:
     _format_dict['NETCDF3_64BIT_OFFSET'] = NC_FORMAT_64BIT
+    _cmode_dict['NETCDF3_64BIT_OFFSET'] = NC_64BIT_OFFSET
 
 # default fill_value to numpy datatype mapping.
 default_fillvals = {#'S1':NC_FILL_CHAR,
@@ -2084,7 +2099,7 @@ strings.
         cdef char *path
         cdef char namstring[NC_MAX_NAME+1]
         cdef int cmode
-        IF HAS_NC_PAR:
+        IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
             cdef MPI_Comm mpicomm
             cdef MPI_Info mpiinfo
 
@@ -2107,12 +2122,20 @@ strings.
             raise ValueError(msg)
 
         if parallel:
-            IF HAS_NC_PAR != 1:
+            IF HAS_PARALLEL4_SUPPORT != 1 and HAS_PNETCDF_SUPPORT != 1:
                 msg='parallel mode requires MPI enabled netcdf-c'
                 raise ValueError(msg)
             ELSE:
-                if format not in ['NETCDF4','NETCDF4_CLASSIC']:
-                    msg='parallel mode only works with format=NETCDF4 or NETCDF4_CLASSIC'
+                parallel_formats = []
+                IF HAS_PARALLEL4_SUPPORT:
+                    parallel_formats += ['NETCDF4','NETCDF4_CLASSIC']
+                IF HAS_PNETCDF_SUPPORT:
+                    parallel_formats += ['NETCDF3_CLASSIC',
+                                         'NETCDF3_64BIT_OFFSET',
+                                         'NETCDF3_64BIT_DATA',
+                                         'NETCDF3_64BIT']
+                if format not in parallel_formats:
+                    msg='parallel mode only works with the following formats: ' + ' '.join(parallel_formats)
                     raise ValueError(msg)
                 if comm is not None:
                     mpicomm = comm.ob_mpi
@@ -2122,9 +2145,7 @@ strings.
                     mpiinfo = info.ob_mpi
                 else:
                     mpiinfo = MPI_INFO_NULL
-                cmode = NC_MPIIO | NC_NETCDF4
-                if format == 'NETCDF4_CLASSIC':
-                    cmode = cmode | NC_CLASSIC_MODEL
+                cmode = NC_MPIIO | _cmode_dict[format]
 
         self._inmemory = False
         if mode == 'w':
@@ -2144,7 +2165,7 @@ strings.
             else:
                 if clobber:
                     if parallel:
-                        IF HAS_NC_PAR:
+                        IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                             ierr = nc_create_par(path, NC_CLOBBER | cmode, \
                                    mpicomm, mpiinfo, &grpid)
                         ELSE:
@@ -2159,7 +2180,7 @@ strings.
                         ierr = nc_create(path, NC_CLOBBER, &grpid)
                 else:
                     if parallel:
-                        IF HAS_NC_PAR:
+                        IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                             ierr = nc_create_par(path, NC_NOCLOBBER | cmode, \
                                    mpicomm, mpiinfo, &grpid)
                         ELSE:
@@ -2194,7 +2215,7 @@ strings.
         version 4.4.1 or higher of the netcdf C lib, and rebuild netcdf4-python."""
                     raise ValueError(msg)
             elif parallel:
-                IF HAS_NC_PAR:
+                IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                     ierr = nc_open_par(path, NC_NOWRITE | NC_MPIIO, \
                            mpicomm, mpiinfo, &grpid)
                 ELSE:
@@ -2205,7 +2226,7 @@ strings.
                 ierr = nc_open(path, NC_NOWRITE, &grpid)
         elif mode == 'r+' or mode == 'a':
             if parallel:
-                IF HAS_NC_PAR:
+                IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                     ierr = nc_open_par(path, NC_WRITE | NC_MPIIO, \
                            mpicomm, mpiinfo, &grpid)
                 ELSE:
@@ -2217,7 +2238,7 @@ strings.
         elif mode == 'as' or mode == 'r+s':
             if parallel:
                 # NC_SHARE ignored
-                IF HAS_NC_PAR:
+                IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                     ierr = nc_open_par(path, NC_WRITE | NC_MPIIO, \
                            mpicomm, mpiinfo, &grpid)
                 ELSE:
@@ -2231,7 +2252,7 @@ strings.
             if clobber:
                 if parallel:
                     # NC_SHARE ignored
-                    IF HAS_NC_PAR:
+                    IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                         ierr = nc_create_par(path, NC_CLOBBER | cmode, \
                                mpicomm, mpiinfo, &grpid)
                     ELSE:
@@ -2246,7 +2267,7 @@ strings.
             else:
                 if parallel:
                     # NC_SHARE ignored
-                    IF HAS_NC_PAR:
+                    IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
                         ierr = nc_create_par(path, NC_NOCLOBBER | cmode, \
                                mpicomm, mpiinfo, &grpid)
                     ELSE:
@@ -5345,7 +5366,7 @@ NC_CHAR).
 turn on or off collective parallel IO access. Ignored if file is not
 open for parallel access.
         """
-        IF HAS_NC_PAR:
+        IF HAS_PARALLEL4_SUPPORT or HAS_PNETCDF_SUPPORT:
             # set collective MPI IO mode on or off
             if value:
                 ierr = nc_var_par_access(self._grpid, self._varid,