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Table of Contents
MPI_T_cvar_get_info - Query information from a control variable
#include <mpi.h>
int MPI_T_cvar_get_info(int cvar_index, char *name, int *name_len,
int *verbosity, MPI_Datatype *datatype, MPI_T_enum
*enumtype,
const *desc, int *desc_len, int *bind, int *scope)
- cvar_index
- Index of the control variable to be queried.
- name_len
- Length of the string and/or buffer for
name.
- desc_len
- Length of the string and/or buffer for desc.
- name
- Buffer to return the string containing the name of the control variable.
- verbosity
- Verbosity level of this variable.
- datatype
- MPI datatype of the
information stored in the control variable.
- enumtype
- Optional descriptor
for enumeration information.
- desc
- Buffer to return the string containing
the description of the control variable.
- bind
- Type of MPI object to which
this variable must be bound.
- scope
- Scope of when changes to this variable
are possible.
MPI_T_cvar_get_info can be used to query information
about a control variable. The function returns the verbosity, datatype,
enumeration type, binding, and scope of the queried control variable in
the arguments verbosity, datatype, enumtype, bind, and scope, respectively.
Control variables in Open MPI are the same as MCA parameters.
As
Open MPI exposes a very large number of MCA parameters (control variables),
control variables are categorized into nine verbosity levels corresponding
to the equivalent ompi_info level. The nine levels are (in increasing order):
- MPI_T_VERBOSITY_USER_BASIC
- Basic information of interest to users
- MPI_T_VERBOSITY_USER_DETAIL
- Detailed information of interest to users
- MPI_T_VERBOSITY_USER_ALL
- All
remaining information of interest to users
- MPI_T_VERBOSITY_TUNER_BASIC
- Basic information required for tuning
- MPI_T_VERBOSITY_TUNER_DETAIL
- Detailed
information required for tuning
- MPI_T_VERBOSITY_TUNER_ALL
- All remaining
information required for tuning
- MPI_T_VERBOSITY_MPIDEV_BASIC
- Basic information
for MPI implementors
- MPI_T_VERBOSITY_MPIDEV_DETAIL
- Detailed information
for MPI implementors
- MPI_T_VERBOSITY_MPIDEV_ALL
- All remaining information
for MPI implementors
For more information see MPI-3 [char167] 14.3.1.
The
datatype returned by MPI_T_cvar_get_info is restricted to one of the following
datatypes: MPI_INT, MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG,
MPI_COUNT, MPI_CHAR, and MPI_DOUBLE. For more information on datatypes in
MPI_T see MPI-3 [char167] 14.3.5.
The scope describes when and how changes
can be made to a control variable. From MPI-3 [char167] 14.3.6, the scope may
be any of the following:
- MPI_T_SCOPE_CONSTANT
- read-only, value is constant
- MPI_T_SCOPE_READONLY
- read-only, cannot be written, but can change
- MPI_T_SCOPE_LOCAL
- may be writeable, writing is a local operation
- MPI_T_SCOPE_GROUP
- may be
writeable, must be done to a group of processes, all processes in a group
must be set to consistent values
- MPI_T_SCOPE_GROUP_EQ
- may be writeable,
must be done to a group of processes, all processes in a group must be
set to the same value
- MPI_T_SCOPE_ALL
- may be writeable, must be done to
all processes, all connected processes must be set to consistent values
- MPI_T_SCOPE_ALL_EQ
- may be writeable, must be done to all processes, all
connected processes must be set to the same value
For more information
see MPI-3 [char167] 14.3.6 Table 14.4.
This MPI tool interface function
returns two strings. This function takes two argument for each string: a
buffer to store the string, and a length which must initially specify the
size of the buffer. If the length passed is n then this function will copy
at most n - 1 characters of the string into the corresponding buffer and
set the length to the number of characters copied - 1. If the length argument
is NULL or the value specified in the length is 0 the corresponding string
buffer is ignored and the string is not returned.
Open MPI does not currently
support binding control variables to MPI objects.
MPI_T_cvar_get_info()
will fail if:
- [MPI_T_ERR_NOT_INITIALIZED]
- The MPI Tools interface not initialized
- [MPI_T_ERR_INVALID_INDEX]
- The control variable index is invalid
ompi_info
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