fix for old MPI.jl

Author: simonbyrne

.appveyor.yml

@@ -30,6 +30,7 @@ install:
         "https://download.microsoft.com/download/A/E/0/AE002626-9D9D-448D-8197-1EA510E297CE/msmpisetup.exe",
         "C:\projects\MSMpiSetup.exe")
   - C:\projects\MSMpiSetup.exe -unattend -minimal
+  - set PATH=C:\Program Files\Microsoft MPI\Bin;%PATH% # can be removed in new MPI.jl
   # This shouldn't typicallybe needed: the installer adds the directory to
   # the PATH. For some reason this doesn't work on Appveyor
   - set JULIA_MPIEXEC=C:\Program Files\Microsoft MPI\Bin\mpiexec.exe

.travis.yml

@@ -49,6 +49,10 @@ before_install:
         export JULIA_MPI_PATH=$HOME/$MPI_IMPL;
       fi
     fi
+# following can be removed with next MPI.jl release.
+  - export PATH=$HOME/OpenMPI/bin:$HOME/MPICH/bin:$PATH
+  - export CC=mpicc
+  - export FC=mpif90
 # Work around OpenMPI attempting to create overly long temporary
 # file names - and erroring as a result
   - export TMPDIR=/tmp

src/mpimanager.jl

@@ -391,7 +391,9 @@ function start_main_loop(mode::TransportMode=TCP_TRANSPORT_ALL;
             Distributed.init_worker(cookie, mgr)
             # Start a worker event loop
             receive_event_loop(mgr)
-            MPI.free(comm)
+            if isdefined(MPI, :free) && hasmethod(MPI.free, Tuple{MPI.Comm})
+                MPI.free(comm)
+            end
             MPI.Finalize()
             exit()
         end