MPI_CONSTANTS(3)MPI_CONSTANTS(3)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:
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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
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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
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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 ALSOMPI_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),
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