program shmemf
      implicit none
      include 'mpif.h'
      integer iam,nprocs,isize,ierr,other,orank
      integer shmem_ptr, shmem_create, shmem_get, shmem_put, shmem_free
      integer shmem_mem_alloc, shmem_mem_free, ilen
      integer locmem,itmp(100),i

c Initiate MPI processes
      call MPI_Init(ierr)
      call MPI_COMM_RANK(MPI_COMM_WORLD, iam, ierr)
      call MPI_COMM_SIZE(MPI_COMM_WORLD, nprocs, ierr)
      print *,' iam and size ',iam,nprocs

C allocate some memory and return a pointer to that memory
      ilen=10000
      locmem=shmem_mem_alloc(MPI_COMM_WORLD, MPI_DOUBLE_PRECISION, ilen)
      if (iam.eq.0)print *,' address of memory ',locmem

C create an integer shared array of isize on each processor
      isize=100
      ierr=shmem_create(MPI_COMM_WORLD, isize, MPI_INTEGER, shmem_ptr)

C put some data into your local array
      do i=1,100
        itmp(i)=iam
      enddo
      ierr=shmem_put(shmem_ptr, 1, 100, iam, itmp)

C synchronize to ensure everyone has put their data
      call MPI_Barrier(MPI_COMM_WORLD,ierr)

C read one data item from the next processor
      other=mod(nprocs+iam-1,nprocs)+1
      if (other.gt.nprocs)other=other-nprocs
      ierr=shmem_get(shmem_ptr, other, 1, other-1, orank)
      print *,' iam, orank ',iam,orank

C remove the shared array
      ierr=shmem_free(shmem_ptr)

C free all allocated memory
      ierr=shmem_mem_free() 

C end the MPI process
      call MPI_Finalize(ierr)
      stop
      end