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MPI_T_CVAR_GET_INFO

SYNTAX
C Syntax
INPUT PARAMETERS
INPUT/OUTPUT PARAMETERS
OUTPUT PARAMETERS
DESCRIPTION
VERBOSITY
DATATYPE
SCOPE
NOTES
ERRORS
COPYRIGHT

MPI_T see MPI-3 section 14.3.5.

MPI_T_cvar_get_info — Query information from a control variable

SYNTAX

C Syntax

#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)

INPUT PARAMETERS

•

cvar_index : Index of the control variable to be queried.

INPUT/OUTPUT PARAMETERS

	•		name_len : Length of the string and/or buffer for name.
	•		desc_len : Length of the string and/or buffer for desc.

OUTPUT PARAMETERS

	•		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.

DESCRIPTION

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.

VERBOSITY

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):

	1.		MPI_T_VERBOSITY_USER_BASIC : Basic information of interest to users
	2.		MPI_T_VERBOSITY_USER_DETAIL : Detailed information of interest to users
	3.		MPI_T_VERBOSITY_USER_ALL : All remaining information of interest to users
	4.		MPI_T_VERBOSITY_TUNER_BASIC : Basic information required for tuning
	5.		MPI_T_VERBOSITY_TUNER_DETAIL : Detailed information required for tuning
	6.		MPI_T_VERBOSITY_TUNER_ALL : All remaining information required for tuning
	7.		MPI_T_VERBOSITY_MPIDEV_BASIC : Basic information for MPI implementors
	8.		MPI_T_VERBOSITY_MPIDEV_DETAIL : Detailed information for MPI implementors
	9.		MPI_T_VERBOSITY_MPIDEV_ALL : All remaining information for MPI implementors

For more information see MPI-3 section 14.3.1.

DATATYPE

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 section 14.3.5.

SCOPE

The scope describes when and how changes can be made to a control variable. From MPI-3 section 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 section 14.3.6 Table 14.4.

NOTES

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.

ERRORS

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

SEE ALSO:

ompi_info

COPYRIGHT

2003-2025, The Open MPI Community