root / synthbench / euroben-dm / mod1i / .svn / text-base / dddot2.f.svn-base @ 0:839f52ef7657
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Function dddot2( 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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|
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Include 'mpif.h' |
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|
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Integer :: comm, datype, tag |
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Integer :: ierr, status(MPI_Status_Size) |
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Integer :: i, left, right, up, maxup |
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Real(l_) :: s, sleft, sright |
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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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! --------------------------------------------------------------------- |
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! --- If on 1 processor we are done: Return. |
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|
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If ( me == 0 ) dotres = s |
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If ( k == 1 ) Return |
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! --------------------------------------------------------------------- |
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! --- Combine partial results on processor 1. |
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|
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datype = MPI_Real8 |
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tag = 1 |
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comm = MPI_Comm_World |
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|
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right = 2*(me + 1) |
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left = right - 1 |
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up = (me - 1)/2 |
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maxup = (k - 2)/2 |
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|
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If ( right < k ) Then |
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Call MPI_Recv( sright, 1, datype, right, tag, comm, |
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& status, ierr ) |
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Call MPI_Recv( sleft, 1, datype, left, tag, comm, |
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& status, ierr ) |
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s = s + sleft + sright |
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Else If ( left < k ) Then |
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Call MPI_Recv( sleft, 1, datype, left, tag, comm, |
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& status, ierr ) |
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s = s + sleft |
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End If |
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If ( me > 0 .AND. me < k ) Then |
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Call MPI_Send( s, 1, datype, up, tag, comm, ierr ) |
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End If |
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If ( me == 0 ) dotres = s |
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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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Call MPI_Send( dotres, 1, datype, left, tag, comm, ierr) |
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If ( right < k ) Then |
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Call MPI_Send( dotres, 1, datype, right, tag, comm, ierr ) |
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End If |
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Else |
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If ( up <= maxup ) Then |
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Call MPI_Recv( dotres, 1, datype, up, tag, comm, status, |
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& ierr ) |
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End If |
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If ( right < k ) Then |
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Call MPI_Send( dotres, 1, datype, right, tag, comm, ierr ) |
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Call MPI_Send( dotres, 1, datype, left , tag, comm, ierr ) |
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Else If ( left < k ) Then |
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Call MPI_Send( dotres, 1, datype, left , tag, comm, ierr ) |
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End If |
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End If |
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! --------------------------------------------------------------------- |
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End Function dddot2 |