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

4.1.6                                             Sep 30, 2023                            MPI_T_pvar_get_info(3)