update to MPI.jl v0.19 (#749)

See JuliaParallel/MPI.jl#485.
Closes #747; closes #748

Project.toml

@@ -39,7 +39,7 @@ ForwardDiff = "0.10.18"
 HDF5 = "0.14, 0.15"
 LinearMaps = "2.7, 3.0"
 LoopVectorization = "0.12.54"
-MPI = "0.16, 0.17, 0.18"
+MPI = "0.19"
 Octavian = "0.3.1"
 OffsetArrays = "1.3"
 P4est = "0.2.2"

src/auxiliary/mpi.jl

@@ -16,14 +16,12 @@ function init_mpi()
     return nothing
   end
 
-  if MPI.Initialized()
-    @assert MPI.Query_thread() >= MPI.THREAD_FUNNELED "MPI already initialized with insufficient threading support"
-  else
-    # MPI.THREAD_FUNNELED: Only main thread makes MPI calls
-    provided = MPI.Init_thread(MPI.THREAD_FUNNELED)
-    atexit(finalize_mpi) # register atexit hook
-    @assert provided >= MPI.THREAD_FUNNELED "MPI library with insufficient threading support"
-  end
+  # MPI.jl handles multiple calls to MPI.Init appropriately. Thus, we don't need
+  # any common checks of the form `if MPI.Initialized() ...`.
+  # threadlevel=MPI.THREAD_FUNNELED: Only main thread makes MPI calls
+  # finalize_atexit=true           : MPI.jl will call call MPI.Finalize as `atexit` hook
+  provided = MPI.Init(threadlevel=MPI.THREAD_FUNNELED, finalize_atexit=true)
+  @assert provided >= MPI.THREAD_FUNNELED "MPI library with insufficient threading support"
 
   # Initialize global MPI state
   MPI_RANK[] = MPI.Comm_rank(MPI.COMM_WORLD)
@@ -37,13 +35,6 @@ function init_mpi()
 end
 
 
-function finalize_mpi()
-  if MPI.Initialized()
-    MPI.Finalize()
-  end
-end
-
-
 const MPI_INITIALIZED = Ref(false)
 const MPI_RANK = Ref(-1)
 const MPI_SIZE = Ref(-1)

test/Project.toml

@@ -11,6 +11,6 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 [compat]
 Cassette = "0.3.5"
 ForwardDiff = "0.10"
-MPI = "0.16, 0.17, 0.18"
+MPI = "0.19"
 OrdinaryDiffEq = "5.60"
 Plots = "1.16"