1 | .\"Copyright 2006-2008 Sun Microsystems, Inc. |
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2 | .\" Copyright (c) 1996 Thinking Machines Corporation |
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3 | .TH MPI_Cart_sub 3 "Dec 08, 2009" "1.4" "Open MPI" |
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4 | .SH NAME |
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5 | \fBMPI_Cart_sub \fP \- Partitions a communicator into subgroups, which form lower-dimensional Cartesian subgrids. |
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6 | |
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7 | .SH SYNTAX |
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8 | .ft R |
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9 | .SH C Syntax |
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10 | .nf |
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11 | #include <mpi.h> |
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12 | int MPI_Cart_sub(MPI_Comm \fIcomm\fP, int\fI *remain_dims\fP, MPI_Comm\fI *comm_new\fP) |
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13 | |
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14 | .SH Fortran Syntax |
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15 | .nf |
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16 | INCLUDE 'mpif.h' |
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17 | MPI_CART_SUB(\fICOMM, REMAIN_DIMS, COMM_NEW, IERROR\fP) |
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18 | INTEGER \fICOMM, COMM_NEW, IERROR\fP |
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19 | LOGICAL \fIREMAIN_DIMS\fP(*) |
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20 | |
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21 | .SH C++ Syntax |
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22 | .nf |
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23 | #include <mpi.h> |
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24 | Cartcomm Cartcomm::Sub(const bool \fIremain_dims\fP[]) const |
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25 | |
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26 | .SH INPUT PARAMETERS |
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27 | .ft R |
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28 | .TP 1i |
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29 | comm |
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30 | Communicator with Cartesian structure (handle). |
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31 | .TP 1i |
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32 | remain_dims |
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33 | The ith entry of remain_dims specifies whether the ith dimension is kept in the subgrid (true) or is dropped (false) (logical vector). |
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34 | |
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35 | .SH OUTPUT PARAMETERS |
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36 | .ft R |
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37 | .TP 1i |
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38 | comm_new |
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39 | Communicator containing the subgrid that includes the calling process (handle). |
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40 | .ft R |
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41 | .TP 1i |
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42 | IERROR |
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43 | Fortran only: Error status (integer). |
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44 | |
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45 | .SH DESCRIPTION |
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46 | .ft R |
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47 | If a Cartesian topology has been created with MPI_Cart_create, the function MPI_Cart_sub can be used to partition the communicator group into subgroups that form lower-dimensional Cartesian subgrids, and to build for each subgroup a communicator with the associated subgrid Cartesian topology. (This function is closely related to MPI_Comm_split.) |
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48 | .sp |
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49 | \fBExample:\fP Assume that MPI_Cart_create( \&..., comm) has defined a (2 x 3 x 4) grid. Let remain_dims = (true, false, true). Then a call to |
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50 | .sp |
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51 | .nf |
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52 | MPI_Cart_sub(comm, remain_dims, comm_new) |
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53 | .fi |
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54 | .sp |
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55 | will create three communicators, each with eight processes in a 2 x 4 Cartesian topology. If remain_dims = (false, false, true) then the call to MPI_Cart_sub(comm, remain_dims, comm_new) will create six nonoverlapping communicators, each with four processes, in a one-dimensional Cartesian topology. |
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56 | |
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57 | .SH ERRORS |
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58 | Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object. |
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59 | .sp |
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60 | Before the error value is returned, the current MPI error handler is |
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61 | called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error. |
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62 | |
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63 | .SH SEE ALSO |
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64 | .ft R |
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65 | .sp |
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66 | .nf |
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67 | MPI_Cart_create |
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68 | MPI_Comm_split |
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69 | |
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