MPI_T_pvar_get_info(3)

NAME
MPI_T_pvar_get_info - Query information from a performance variable

SYNTAX

C Syntax
#include <mpi.h>
int MPI_T_pvar_get_info(int pvar_index, char *name, int *name_len,
                        int *verbosity, int *var_class, MPI_Datatype *datatype, MPI_T_enum *enumtype,
                        char *desc, int *desc_len, int *bind, int *readonly, int *continuous,
                        int *atomic)

INPUT PARAMETERS

pvar_index
    Index of the performance 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 performance variable.

verbosity
    Verbosity level of this variable.

var_class
    Class of performance variable.

datatype
    MPI datatype of the information stored in the performance variable.

enumtype
    Optional descriptor for enumeration information.

desc
    Buffer to return the string containing the description of the performance variable.

bind
    Type of MPI object to which this variable must be bound.

readonly
    Flag indicating whether the variable can be written/reset.

continuous
    Flag indicating whether the variable can be started and stopped or is continuously active.

atomic
    Flag indicating whether the variable can be atomically read and reset.

DESCRIPTION
MPI_T_pvar_get_info can be used to query information from a performance variable. The function returns the verbosity, class, datatype, enumeration type, and binding of the queried control variable in the arguments verbosity, var_class, datatype, enumtype, and bind respectively. Flags indicating whether the variable is read-only, continuous, or atomic are returns in readonly, continuous, and atomic accordingly. See MPI-3 § 14.3.7 for more information. See the man page for MPI_T_cvar_get_info for information on variable verbosity.

VARIABLE CLASS
Performance variables are categorized into classes which describe their initial value, valid types, and behavior. The class returned in the var_class parameter may be one of the following:

MPI_T_PVAR_CLASS_STATE
    Variable represents a set of discrete states that may be described by an enumerator. Variables of this class must be represented by an MPI_INT. The starting value is the current state of the variable.

MPI_T_PVAR_CLASS_LEVEL
    Variable represents the current utilization level of a resource. Variables of this class must be represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. The starting value is the current utilization level of the resource.

MPI_T_PVAR_CLASS_SIZE
    Variable represents the fixed size of a resource. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. The starting value is the current size of the resource.

MPI_T_PVAR_CLASS_PERCENTAGE
    Variable represents the current precentage utilization level of a resource. Variables of this class are represented by an MPI_DOUBLE. The starting value is the current percentage utilization of the resource.

MPI_T_PVAR_CLASS_HIGHWATERMARK
    Variable represents the high watermark of the utilization of a resource. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. The starting value is the current utilization of the resource.

MPI_T_PVAR_CLASS_HIGHWATERMARK
    Variable represents the low watermark of the utilization of a resource. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. The starting value is the current utilization of the resource.

MPI_T_PVAR_CLASS_COUNTER
    Variable represents a count of the number of occurrences of a specific event. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, or MPI_UNSIGNED_LONG_LONG. The starting value is 0.

MPI_T_PVAR_CLASS_COUNTER
    Variable represents an aggregated value that represents a sum of arguments processed during a specific event. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. The starting value is 0.

MPI_T_PVAR_CLASS_TIMER
    Variable represents the aggregated time spent by the MPI implementation while processing an event, type of event, or section of code. Variables of this class are represented by an MPI_UNSIGNED, MPI_UNSIGNED_LONG, MPI_UNSIGNED_LONG_LONG, or MPI_DOUBLE. If the variable is represented by an MPI_DOUBLE the units will be the same as those used by MPI_Wtime(). The starting value is 0.

MPI_T_PVAR_CLASS_GENERIC
    Variable does not fit into any other class. Can by represented by an type supported by the MPI tool information interface (see DATATYPE). Starting value is variable specific.

    For more information see MPI-3 § 14.3.7.

DATATYPE
The datatype returned by MPI_T_pvar_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 the MPI Tool information interface see MPI-3 § 14.3.5.

BINDING
Performance variables may be bound to an MPI object. The binding returned in the bind parameter may be one of the following:

MPI_T_BIND_NO_OBJECT
    No object

MPI_T_BIND_MPI_COMM
    MPI communicator

MPI_T_BIND_MPI_DATATYPE
    MPI datatype

MPI_T_BIND_MPI_ERRHANDLER
    MPI error handler

MPI_T_BIND_MPI_FILE
    MPI file handle

MPI_T_BIND_MPI_GROUP
    MPI group

MPI_T_BIND_MPI_OP
    MPI reduction operator

MPI_T_BIND_MPI_REQUEST
    MPI request

MPI_T_BIND_MPI_WIN
    MPI window for one-sided communication

MPI_T_BIND_MPI_MESSAGE
    MPI message object

MPI_T_BIND_MPI_INFO
    MPI info object

    For more information see MPI-3 § 14.3.2.

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. For more information see MPI-3 § 14.3.3.

ERRORS
MPI_T_pvar_get_info() will fail if:

[MPI_T_ERR_NOT_INITIALIZED]
    The MPI Tools interface not initialized

[MPI_T_ERR_INVALID_INDEX]
    The performance variable index is invalid

SEE ALSO
MPI_T_cvar_get_info