root / synthbench / euroben-dm / mod1i / dddot1.f @ 0:839f52ef7657
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Function dddot1( k, n, x, y ) Result( dotres ) |
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! --------------------------------------------------------------------- |
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Use dist_module |
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Use numerics |
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Implicit None |
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Integer :: k, n |
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Real(l_) :: x(n), y(n), dotres |
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Include 'mpif.h' |
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Integer, Parameter :: maxnod = 2048 |
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Integer :: comm, datype, i, ierr, length, |
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& status(MPI_Status_Size), tag |
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Real(l_) :: s, spart(0:maxnod-1) |
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! --------------------------------------------------------------------- |
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! --- Do local part of dotproduct. |
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|
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s = 0.0_l_ |
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Do i = 1, n |
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s = s + x(i)*y(i) |
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End Do |
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dotres = s |
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! --------------------------------------------------------------------- |
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! --- If on 1 processor we are done: Return. |
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|
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If ( k == 1 ) Return |
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! --------------------------------------------------------------------- |
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! --- Send partial results from all other processors to processor 1. |
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datype = Mpi_Real8 |
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length = 1 |
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tag = 1 |
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comm = MPI_Comm_World |
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|
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If ( me > 0 .AND. me < k ) Then |
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Call MPI_Send( s, length, datype , 0, tag, comm, ierr ) |
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Else If ( me == 0 ) Then |
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! --------------------------------------------------------------------- |
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! --- Receive partial results (blocking) on processor 1. |
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|
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Do i = 1, k - 1 |
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Call MPI_Recv( spart(i), length, datype, i, tag, comm, |
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& status, ierr ) |
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End Do |
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End If |
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! --------------------------------------------------------------------- |
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! --- Combine partial results. |
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|
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If ( me == 0 ) Then |
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Do i = 1, k - 1 |
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dotres = dotres + spart(i) |
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End Do |
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End If |
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! --------------------------------------------------------------------- |
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! --- Send sum to all processors. |
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|
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If ( me == 0 ) Then |
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Do i = 1, k - 1 |
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Call MPI_Send( dotres, length, datype, i, tag, comm, |
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& ierr ) |
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End Do |
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Else If ( me > 0 .AND. me < k ) Then |
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Call MPI_Recv( dotres, length, datype, 0, tag, comm, |
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& status, ierr ) |
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End If |
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! --------------------------------------------------------------------- |
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End Function dddot1 |