OMPI_Affinity_str(3) Open MPI OMPI_Affinity_str(3)
NAME
OMPI_Affinity_str - Obtain prettyprint strings of processor affinity
information for this process
SYNTAX
C Syntax
#include <mpi.h>
#include <mpi-ext.h>
int OMPI_Affinity_str(ompi_affinity_fmt_type_t fmt_type,
char ompi_bound[OMPI_AFFINITY_STRING_MAX],
char current_binding[OMPI_AFFINITY_STRING_MAX],
char exists[OMPI_AFFINITY_STRING_MAX])
Fortran Syntax
There is no Fortran binding for this function.
Fortran 2008 Syntax
There is no Fortran 2008 binding for this function.
C++ Syntax
There is no C++ binding for this function.
INPUT PARAMETERS
fmt_type An enum indicating how to format the returned ompi_bound and
current_binding strings. OMPI_AFFINITY_RSRC_STRING_FMT re-
turns 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.
OUTPUT PARAMETERS
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.
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").
exists A prettyprint string describing the available sockets and
sockets on this host.
DESCRIPTION
Open MPI may bind a process to specific sockets and/or cores at process
launch time. This non-standard Open MPI function call returns pret-
typrint information about three things:
Where Open MPI bound this process.
The string returned in 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.
Where this process is currently bound.
Regardless of whether Open MPI bound this process or not, an-
other entity may have bound it. The string returned in cur-
rent_binding will indicate what the 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.
What processors exist.
As a convenience to the user, the exists string will contain a
prettyprint description of the sockets and cores that this
process can see (which is usually all processors in the system).
Examples
Example 1: Print out processes binding using resource string format.
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);
...
Output of mpirun -np 2 -bind-to-core a.out:
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
Output of mpirun -np 2 -bind-to-socket a.out:
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
Example 2: Print out processes binding using layout string format.
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);
...
Output of mpirun -np 2 -bind-to-core a.out:
rank 0:
ompi_bound: [B . . .]
current_binding: [B . . .]
exists: [. . . .]
rank 1:
ompi_bound: [. B . .]
current_binding: [. B . .]
exists: [. . . .]
Output of mpirun -np 2 -bind-to-socket a.out:
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: [. . . .]
See Also
mpirun(1)
4.1.2 Nov 24, 2021 OMPI_Affinity_str(3)
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