openmpi/ompi/mpiext/affinity/c/OMPI_Affinity_str.3in

.\" Copyright 2007-2010 Oracle and/or its affiliates.  All rights reserved.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright (c) 2010 Cisco Systems, Inc.  All rights reserved.
.TH OMPI_Affinity_str 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBOMPI_Affinity_str\fP \- Obtain prettyprint strings of processor affinity information for this process

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
#include <mpi-ext.h>

int OMPI_Affinity_str(ompi_affinity_fmt_type_t \fIfmt_type\fP,
                      char \fIompi_bound\fP[OMPI_AFFINITY_STRING_MAX],
                      char \fIcurrent_binding\fP[OMPI_AFFINITY_STRING_MAX],
                      char \fIexists\fP[OMPI_AFFINITY_STRING_MAX])
.fi
.SH Fortran Syntax
There is no Fortran binding for this function.
.
.SH C++ Syntax
There is no C++ binding for this function.
.
.SH INPUT PARAMETERS
.ft R
.TP 1i
fmt_type
An enum indicating how to format the returned ompi_bound and
current_binding strings.  OMPI_AFFINITY_RSRC_STRING_FMT returns the
string as human-readable resource names, such as "socket 0, core 0".

OMPI_AFFINITY_LAYOUT_FMT returns ASCII art representing where this MPI
process is bound relative to the machine resource layout.  For example
"[. B][. .]" shows the process that called the routine is bound to 
socket 0, core 1 in a system with 2 sockets, each containing 2 cores.

See below for more output examples.

.
.SH OUTPUT PARAMETERS
.ft R
.TP 1i
ompi_bound
A prettyprint string describing what processor(s) Open MPI bound this
process to, or a string indicating that Open MPI did not bind this
process.
.
.TP 1i
current_binding
A prettyprint string describing what processor(s) this process is
currently bound to, or a string indicating that the process is bound
to all available processors (and is therefore considered "unbound").
.
.TP 1i
exists
A prettyprint string describing the available sockets and sockets on
this host.

.SH DESCRIPTION
.ft R
Open MPI may bind a process to specific sockets and/or cores at
process launch time.  This non-standard Open MPI function call returns
prettyprint information about three things:
.
.TP
Where Open MPI bound this process.
The string returned in 
.B
ompi_bound
will either indicate that Open MPI did not bind this process to
anything, or it will contain a prettyprint description of the
processor(s) to which Open MPI bound this process.
.
.TP
Where this process is currently bound.
Regardless of whether Open MPI bound this process or not, another
entity may have bound it.  The string returned in
.B current_binding
will indicate what the
.I
current
binding is of this process, regardless of what Open MPI may have done
earlier.  The string returned will either indicate that the process is
unbound (meaning that it is bound to all available processors) or it
will contain a prettyprint description of the sockets and cores to
which the process is currently bound.
.
.TP
What processors exist.
As a convenience to the user, the
.B
exists
string will contain a prettyprint description of the sockets and cores
that this process can see (which is
.I usually
all processors in the system).

.SH Examples
.ft R
\fBExample 1:\fP  Print out processes binding using resource string format.
.sp
.nf
    int rank;
    char ompi_bound[OMPI_AFFINITY_STRING_MAX];
    char current_binding[OMPI_AFFINITY_STRING_MAX];
    char exists[OMPI_AFFINITY_STRING_MAX];

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    OMPI_Affinity_str(OMPI_AFFINITY_RSRC_STRING_FMT, 
                      ompi_bound, current_binding, exists);
    printf("rank %d: \\n"
           "       ompi_bound: %s\\n"
           "  current_binding: %s\\n"
           "           exists: %s\\n",
           rank, ompi_bound, current_binding, exists);
    ...
.fi
.PP
Output of mpirun -np 2 -bind-to-core a.out:
.nf
rank 0: 
       ompi_bound: socket 0[core 0] 
  current_binding: socket 0[core 0] 
           exists: socket 0 has 4 cores
rank 1: 
       ompi_bound: socket 0[core 1] 
  current_binding: socket 0[core 1] 
           exists: socket 0 has 4 cores
.fi
.PP
Output of mpirun -np 2 -bind-to-socket a.out:
.nf
rank 0: 
       ompi_bound: socket 0[core 0-3] 
  current_binding: Not bound (or bound to all available processors)
           exists: socket 0 has 4 cores
rank 1: 
       ompi_bound: socket 0[core 0-3] 
  current_binding: Not bound (or bound to all available processors)
           exists: socket 0 has 4 cores
.fi
.sp
.br
\fBExample 2:\fP  Print out processes binding using layout string format.
.sp
.nf
    int rank;
    char ompi_bound[OMPI_AFFINITY_STRING_MAX];
    char current_binding[OMPI_AFFINITY_STRING_MAX];
    char exists[OMPI_AFFINITY_STRING_MAX];

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    OMPI_Affinity_str(OMPI_AFFINITY_LAYOUT_FMT, 
                      ompi_bound, current_binding, exists);
    printf("rank %d: \\n"
           "       ompi_bound: %s\\n"
           "  current_binding: %s\\n"
           "           exists: %s\\n",
           rank, ompi_bound, current_binding, exists);
    ...
.fi
.PP
Output of mpirun -np 2 -bind-to-core a.out:
.nf
rank 0: 
       ompi_bound: [B . . .]
  current_binding: [B . . .]
           exists: [. . . .]
rank 1: 
       ompi_bound: [. B . .]
  current_binding: [. B . .]
           exists: [. . . .]
.fi
.PP
Output of mpirun -np 2 -bind-to-socket a.out:
.nf
rank 0: 
       ompi_bound: [B B B B]
  current_binding: [B B B B]
           exists: [. . . .]
rank 1: 
       ompi_bound: [B B B B]
  current_binding: [B B B B]
           exists: [. . . .]
.fi

.SH See Also
.ft R
.nf
mpirun(1)
.fi