MPI_Constants(3)
MPI_Constants - Defines constants
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NAME MPI_Constants - Defines constants STANDARDS This release implements the MPI 1.2 standard, as documented by the MPI Forum in the spring 1997 release of MPI: A Message Passing Interface Standard. DESCRIPTION The MPI_Constants routine defines constants of the following types: * Communicators * Groups * Results of compare operations * Collective operations * Permanent key values * Null objects * Predefined constants * Topology types * MPI status * Special MPI types and functions Communicators The following communicator constants are of type MPI_Comm in C and type integer in Fortran: MPI_COMM_WORLD Specifies a constant that contains all of the processes MPI_COMM_SELF Specifies a constant that contains only the calling process Groups The following group constant is of type MPI_Group in C and type integer in Fortran: MPI_GROUP_EMPTY Specifies a group that contains no members Compare Operation Results The following constants specify results of compare operations: MPI_IDENT The groups are identical. MPI_CONGRUENT The groups are identical (used only for MPI_Comm_compare(3)). MPI_SIMILAR The groups contain the same members, but in a different order. MPI_UNEQUAL The groups are not equal. Collective Operations The collective combination operations (MPI_Reduce(3), MPI_Allreduce(3), MPI_Reduce_scatter(3), and MPI_Scan(3)) take a combination operation. This combination operation is of type MPI_Op in C and of type integer in Fortran. The predefined operations are as follows: MPI_MAX Returns the maximum value MPI_MIN Returns the minumum value MPI_SUM Returns the sum MPI_PROD Returns the product MPI_LAND Returns the logical AND MPI_BAND Returns the bitwise AND MPI_LOR Returns the logical OR MPI_BOR Returns the bitwise OR MPI_LXOR Returns the logical exclusive OR MPI_BXOR Returns the bitwise exclusive OR MPI_MINLOC Returns the minimum value and the location (actually, it returns the value of the second element of the structure where the minimum of the first element is found) MPI_MAXLOC Returns the maximum value and the location Permanent Key Values The types of the following permanent key value constants are the same in C and Fortran: MPI_TAG_UB Specifies largest tag value MPI_HOST Specifies the rank of the process that is host, if any MPI_IO Specifies the rank of the process that can perform I/O operations MPI_WTIME_IS_GLOBAL Has a value of 1 if MPI_Wtime(3) is globally synchronized Null Objects The following constants specify null objects: MPI_COMM_NULL Specifies a null communicator MPI_OP_NULL Specifies a null operation MPI_GROUP_NULL Specifies a null group MPI_DATATYPE_NULL Specifies a null data type MPI_REQUEST_NULL Specifies a null request MPI_ERRHANDLER_NULL Specifies a null error handler Predefined Constants The following constants are predefined: MPI_MAX_PROCESSOR_NAME Specifies the maximum length of the name returned by MPI_Get_processor_name(3) MPI_MAX_ERROR_STRING Specifies the maximum length of the string returned by MPI_Error_string(3) MPI_UNDEFINED Used by many routines to indicate an undefined or unknown integer value MPI_UNDEFINED_RANK Specifies an unknown rank MPI_KEYVAL_INVALID Provides a special key value that can be used to detect uninitialized key values MPI_BSEND_OVERHEAD Specifies a value that can be added to the size of a MPI_Bsend(3) buffer for each outstanding message MPI_PROC_NULL Specifies a rank that can be used to send or receive from no-one MPI_ANY_SOURCE Indicates, in a receive, to accept a message from anyone MPI_ANY_TAG Indicates, in a receive, to accept a message with any tag value MPI_BOTTOM Can be used to indicate the bottom of the address space Topology Types The following constants are topology types: MPI_GRAPH Indicates a general graph MPI_CART Indicates a Cartesian grid MPI Status The MPI_Status data type is a structure. The elements that programmers can use are as follows: MPI_SOURCE Indicates who sent the message MPI_TAG Indicates with what tag the message was sent MPI_ERROR Indicates any error return Special MPI Types and Functions The following constants are special MPI types and functions: MPI_Aint Specifies a C type that holds any valid address MPI_Handler_function Specifies a C function for handling errors (see the MPI_Errhandler_create(3) man page) MPI_User_function Specifies a C function to combine values (see the Collective Operations subsection on this man page) and the MPI_Op_create(3) man page) MPI_Copy_function Specifies a function to copy attributes (see the MPI_Keyval_create(3) man page) MPI_Delete_function Specifies a function to delete attributes (see the MPI_Keyval_create(3) man page) MPI_ERRORS_ARE_FATAL Specifies an error handler that forces an exit on error MPI_ERRORS_RETURN Specifies an error handler that returns error codes (as a value of the MPI routine in C and through the last argument in Fortran) SEE ALSO MPI_Allreduce(3), MPI_Bsend(3), MPI_Comm_compare(3), MPI_Errhandler_create(3), MPI_Error_string(3), MPI_Get_processor_name(3), MPI_Keyval_create(3), MPI_Op_create(3), MPI_Reduce(3), MPI_Reduce_scatter(3), MPI_Scan(3), MPI_Wtime(3)