79 строки
2.5 KiB
Fortran
79 строки
2.5 KiB
Fortran
C
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C Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
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C University Research and Technology
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C Corporation. All rights reserved.
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C Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
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C
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C Simple ring test program
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C
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program ring_f77
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implicit none
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include 'mpif.h'
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integer rank, size, tag, next, from, message, ierr
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C Start up MPI */
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call MPI_INIT(ierr)
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call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
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call MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierr)
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C Calculate the rank of the next process in the ring. Use the
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C modulus operator so that the last process "wraps around" to rank
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C zero.
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tag = 201
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next = mod((rank + 1), size)
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from = mod((rank + size - 1), size)
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C If we are the "master" process (i.e., MPI_COMM_WORLD rank 0), put
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C the number of times to go around the ring in the message.
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if (rank .eq. 0) then
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message = 10
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print *, 'Process 0 sending ', message, ' to ', next, ' tag ',
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& tag, ' (', size, ' processes in ring)'
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call MPI_SEND(message, 1, MPI_INTEGER, next, tag,
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& MPI_COMM_WORLD, ierr)
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print *, 'Process 0 sent to ', next
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endif
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C Pass the message around the ring. The exit mechanism works as
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C follows: the message (a positive integer) is passed around the
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C ring. Each time it passes rank 0, it is decremented. When each
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C processes receives a message containing a 0 value, it passes the
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C message on to the next process and then quits. By passing the 0
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C message first, every process gets the 0 message and can quit
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C normally.
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10 call MPI_RECV(message, 1, MPI_INTEGER, from, tag,
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& MPI_COMM_WORLD, MPI_STATUS_IGNORE, ierr)
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if (rank .eq. 0) then
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message = message - 1
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print *, 'Process 0 decremented value:', message
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endif
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call MPI_SEND(message, 1, MPI_INTEGER, next, tag,
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& MPI_COMM_WORLD, ierr)
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if (message .eq. 0) then
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print *, 'Process ', rank, ' exiting'
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goto 20
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endif
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goto 10
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C The last process does one extra send to process 0, which needs to
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C be received before the program can exit
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20 if (rank .eq. 0) then
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call MPI_RECV(message, 1, MPI_INTEGER, from, tag,
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& MPI_COMM_WORLD, MPI_STATUS_IGNORE, ierr)
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endif
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C All done
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call MPI_FINALIZE(ierr)
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end
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