Introduction

This module wraps the most useful mpi calls by using generic programming techniques. It supports most of the collective operations (such as BCAST, GATHER, REDUCE, etc.). These subroutines are

• MPI_INIT()
• MPI_FINALIZE()
• MPI_WTIME()
• MPI_WTICK()
• MPI_BARRIER()
• MPI_DIMS_CREATE()
• MPI_CART_CREATE()
• MPI_CART_COORDS()
• MPI_COMM_SPLIT()
• MPI_COMM_RANK()
• MPI_COMM_SIZE()
• MPI_GET_PROCESSOR_NAME()
• MPI_BCAST()
• MPI_GATHER()
• MPI_GATHERV()
• MPI_ALLGATHER()
• MPI_ALLGATHERV()
• MPI_REDUCE()
• MPI_ALLREDUCE()

etc. However, none of the point-to-point operations is supported. In the module, we also try to implement a light-weight error handler. Enjoy it!

Type

module

Source

src/m_mpi.f90

Usage

(1) Include mpi support.

use mmpi

Please pay attention to the module name. It is mmpi, instead of mpi.

(2) Init mpi environment.

call mp_init()            ! init mpi environment
call mp_comm_rank(myid)   ! get current process it
call mp_comm_size(nprocs) ! get number of processes

(3) Broadcast data.

real(dp), allocatable :: real_data(:,:,:)
integer, allocatable :: int_data(:)
complex(dp), allocatable :: cmplx_data(:,:,:,:)

call mp_bcast(real_data, master)
call mp_bcast(int_data, master)
call mp_bcast(cmplx_data, master)

Here master == 0 which means the master node/root process.

(4) Allreduce data.

real(dp), allocatable :: real_data(:)
real(dp), allocatable :: real_data_mpi(:)

call mp_allreduce(real_data, real_data_mpi)     ! all-readuce data
real_data = real_data_mpi / number_of_processes ! calculate the average

(5) Setup barrier.

call mp_barrier()

(6) Finialize mpi environment.

call mp_finalize()