mp_maxloc_dv Subroutine

   SUBROUTINE mp_maxloc_dv(msg, gid)
      !! Finds the location of the maximal element in a vector.
      !!
      !! MPI mapping
      !! mpi_allreduce with the MPI_MAXLOC reduction function identifier
      !!
      !! Invalid data types
      !! This routine is invalid for (int_8) data!

      REAL(kind=real_8), CONTIGUOUS, INTENT(INOUT)         :: msg(:)
         !! Find location of maximum element among these data (input).
      TYPE(mp_comm_type), INTENT(IN)                      :: gid
         !! Message passing environment identifier

      CHARACTER(LEN=*), PARAMETER :: routineN = 'mp_maxloc_dv'

      INTEGER                                  :: handle, ierr
#if defined(__parallel)
      INTEGER                                  :: msglen
      REAL(kind=real_8), ALLOCATABLE           :: res(:)
#endif

      ierr = 0
      IF ("d" .EQ. "l" .AND. real_8 .EQ. int_8) THEN
         DBCSR_ABORT("Maximal location not available with long integers @ "//routineN)
      END IF
      CALL timeset(routineN, handle)

#if defined(__parallel)
      msglen = SIZE(msg)
      ALLOCATE (res(1:msglen))
      CALL mpi_allreduce(msg, res, msglen/2, MPI_2DOUBLE_PRECISION, MPI_MAXLOC, gid%handle, ierr)
      IF (ierr /= 0) CALL mp_stop(ierr, "mpi_allreduce @ "//routineN)
      msg = res
      DEALLOCATE (res)
      CALL add_perf(perf_id=3, msg_size=msglen*real_8_size)
#else
      MARK_USED(msg)
      MARK_USED(gid)
#endif
      CALL timestop(handle)
   END SUBROUTINE mp_maxloc_dv