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<TITLE>HPL_reduce HPL 2.0 Library Functions September 10, 2008</TITLE> |
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ALINK = "#ffff00"> |
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<H1>Name</H1> |
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<B>HPL_reduce</B> Reduce operation. |
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<H1>Synopsis</H1> |
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<CODE>#include "hpl.h"</CODE><BR><BR> |
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<CODE>int</CODE> |
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<CODE>HPL_reduce(</CODE> |
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<CODE>void *</CODE> |
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<CODE>BUFFER</CODE>, |
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<CODE>const int</CODE> |
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<CODE>COUNT</CODE>, |
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<CODE>const HPL_T_TYPE</CODE> |
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<CODE>DTYPE</CODE>, |
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<CODE>const HPL_T_OP </CODE> |
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<CODE>OP</CODE>, |
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<CODE>const int</CODE> |
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<CODE>ROOT</CODE>, |
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<CODE>MPI_Comm</CODE> |
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<CODE>COMM</CODE> |
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<CODE>);</CODE> |
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<H1>Description</H1> |
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<B>HPL_reduce</B> |
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performs a global reduce operation across all processes of |
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a group. Note that the input buffer is used as workarray and in all |
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processes but the accumulating process corrupting the original data. |
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<H1>Arguments</H1> |
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<PRE>
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BUFFER (local input/output) void * |
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On entry, BUFFER points to the buffer to be reduced. On |
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exit, and in process of rank ROOT this array contains the |
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reduced data. This buffer is also used as workspace during |
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the operation in the other processes of the group. |
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</PRE>
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<PRE>
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COUNT (global input) const int |
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On entry, COUNT indicates the number of entries in BUFFER. |
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COUNT must be at least zero. |
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</PRE>
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<PRE>
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DTYPE (global input) const HPL_T_TYPE |
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On entry, DTYPE specifies the type of the buffers operands. |
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<PRE>
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OP (global input) const HPL_T_OP |
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On entry, OP is a pointer to the local combine function. |
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ROOT (global input) const int |
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On entry, ROOT is the coordinate of the accumulating process. |
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<PRE>
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COMM (global/local input) MPI_Comm |
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The MPI communicator identifying the process collection. |
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</PRE>
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<H1>See Also</H1> |
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<A HREF="HPL_broadcast.html">HPL_broadcast</A>, |
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<A HREF="HPL_all_reduce.html">HPL_all_reduce</A>, |
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<A HREF="HPL_barrier.html">HPL_barrier</A>, |
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<A HREF="HPL_min.html">HPL_min</A>, |
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<A HREF="HPL_max.html">HPL_max</A>, |
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<A HREF="HPL_sum.html">HPL_sum</A>. |
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