add mpigatherinplace example for reproducing pmpi wrapper bug

mpigatherinplace.f90

@@ -0,0 +1,58 @@
+program mpigatherinplace
+use mpi
+implicit none
+
+integer :: rank, ierr, nmpi, i
+
+integer :: N, err
+real(kind=8), dimension(:), allocatable :: allx
+real :: asum, lsum
+
+N = 128*1024*1024
+
+call MPI_Init(ierr)
+if (ierr /= 0) then
+    print *, 'Failed MPI_Init: ', ierr
+    stop
+end if
+
+call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
+if (ierr /= 0) then
+    print *, 'Failed MPI_COMM_RANK: ', ierr
+    stop
+end if
+
+call MPI_COMM_SIZE(MPI_COMM_WORLD, nmpi, ierr)
+if (ierr /= 0) then
+    print *, 'Failed MPI_COMM_SIZE: ', ierr
+    stop
+end if
+
+allocate(allx(N*nmpi))
+
+lsum = 0
+do i=1, N
+    allx(rank*N+i) = rank*i/N
+    lsum = lsum + allx(rank*N+i)
+end do
+
+call MPI_Allgather(MPI_IN_PLACE, 0, MPI_DOUBLE, &
+                 & allx, N, MPI_DOUBLE, MPI_COMM_WORLD, ierr)
+if (ierr /= 0) then
+    print *, 'Failed MPI_Allgather: ', ierr
+    stop
+end if
+
+asum = sum(allx)
+
+print *, rank, "/", nmpi, " ", lsum, " ", asum
+
+deallocate(allx)
+
+call MPI_Finalize(ierr)
+if (ierr /= 0) then
+    print *, 'Failed MPI_Finalize: ', ierr
+    stop
+end if
+
+end program mpigatherinplace