Note that the Fortran types should only be used in Fortran programs,
and the C types should only be used in C programs. For example,
it is in error to use
MPI_INT
for a Fortran INTEGER.
Datatypes are of type
MPI_Datatype
in C and of tyep
INTEGER
in Fortran.
C DATATYPES
MPI_CHAR
- char
MPI_BYTE
- See standard; like unsigned char
MPI_SHORT
- short
MPI_INT
- int
MPI_LONG
- long
MPI_FLOAT
- float
MPI_DOUBLE
- double
MPI_UNSIGNED_CHAR
- unsigned char
MPI_UNSIGNED_SHORT
- unsigned short
MPI_UNSIGNED
- unsigned int
MPI_UNSIGNED_LONG
- unsigned long
MPI_LONG_DOUBLE
- long double (some systems may not implement)
MPI_LONG_LONG_INT
- long long (some systems may not implement)
The following are datatypes for the MPI functions
MPI_MAXLOC
and
MPI_MINLOC
.
MPI_FLOAT_INT
-
struct { float, int }
MPI_LONG_INT
-
struct { long, int }
MPI_DOUBLE_INT
-
struct { double, int }
MPI_SHORT_INT
-
struct { short, int }
MPI_2INT
-
struct { int, int }
MPI_LONG_DOUBLE_INT
-
struct { long double, int }; this
is an OPTIONAL type, and may be set to NULL
Note that there is no
MPI_LONG_LONG_INT
type corresponding to
a
struct { long long, int }
.
Special datatypes for C and Fortran
MPI_PACKED
- For
MPI_Pack
and
MPI_Unpack
MPI_UB
- For
MPI_Type_struct
; an upper-bound indicator
MPI_LB
- For
MPI_Type_struct
; a lower-bound indicator
FORTRAN DATATYPES
MPI_REAL
-
REAL
MPI_INTEGER
-
INTEGER
MPI_LOGICAL
-
LOGICAL
MPI_DOUBLE_PRECISION
-
DOUBLE PRECISION
MPI_COMPLEX
-
COMPLEX
MPI_DOUBLE_COMPLEX
-
complex*16
(or
complex*32
) where supported.
The following datatypes are optional
MPI_INTEGER1
-
integer*1
if supported
MPI_INTEGER2
-
integer*2
if supported
MPI_INTEGER4
-
integer*4
if supported
MPI_REAL4
-
real*4
if supported
MPI_REAL8
-
real*8
if supported
The following are datatypes for the MPI functions
MPI_MAXLOC
and
MPI_MINLOC
.
In Fortran, these datatype always consist of
two elements of the same Fortran type.
MPI_2INTEGER
-
INTEGER,INTEGER
MPI_2REAL
-
REAL, REAL
MPI_2DOUBLE_PRECISION
-
DOUBLE PRECISION, DOUBLE PRECISION
MPI_2COMPLEX
-
COMPLEX, COMPLEX
MPI_2DOUBLE_COMPLEX
-
complex*16, complex*16
COMMUNICATORS
Communicators are of type
MPI_Comm
in C and
INTEGER
in Fortran
MPI_COMM_WORLD
- Contains all of the processes
MPI_COMM_SELF
- Contains only the calling process
GROUPS
Groups are of type
MPI_Group
in C and
INTEGER
in Fortran
MPI_GROUP_EMPTY
- A group containing no members.
RESULTS OF THE COMPARE OPERATIONS
MPI_IDENT
- Identical
MPI_CONGRUENT
- (only for
MPI_COMM_COMPARE
) The groups are identical
MPI_SIMILAR
- Same members, but in a different order
MPI_UNEQUAL
- Different
COLLECTIVE OPERATIONS
The collective combination operations (
MPI_REDUCE
,
MPI_ALLREDUCE
,
MPI_REDUCE_SCATTER
, and
MPI_SCAN
) take a combination operation.
This operation is of type
MPI_Op
in C and of type
INTEGER
in Fortran.
The predefined operations are
MPI_MAX
- return the maximum
MPI_MIN
- return the minumum
MPI_SUM
- return the sum
MPI_PROD
- return the product
MPI_LAND
- return the logical and
MPI_BAND
- return the bitwise and
MPI_LOR
- return the logical or
MPI_BOR
- return the bitwise of
MPI_LXOR
- return the logical exclusive or
MPI_BXOR
- return the bitwise exclusive or
MPI_MINLOC
- return the minimum and the location (actually, the value of
the second element of the structure where the minimum of
the first is found)
MPI_MAXLOC
- return the maximum and the location
NOTES ON COLLECTIVE OPERATIONS
The reduction functions (
MPI_Op
) do not return an error value. As a result,
if the functions detect an error, all they can do is either call
MPI_Abort
or silently skip the problem. Thus, if you change the error handler from
MPI_ERRORS_ARE_FATAL
to something else, for example,
MPI_ERRORS_RETURN
,
then no error may be indicated.
The reason for this is the performance problems in ensuring that
all collective routines return the same error value.
Note that not all datatypes are valid for these functions. For example,
MPI_COMPLEX
is not valid for
MPI_MAX
and
MPI_MIN
.
In addition, the MPI
1.1 standard did not include the C types
MPI_CHAR
and
MPI_UNSIGNED_CHAR
among the lists of arithmetic types for operations like
MPI_SUM
.
However,
since the C type
char
is an integer type (like
short
), it should have been
included. The MPI Forum will probably include
char
and
unsigned char
as a clarification to MPI 1.1; until then, users are advised that MPI
implementations may not accept
MPI_CHAR
and
MPI_UNSIGNED_CHAR
as valid
datatypes for
MPI_SUM
,
MPI_PROD
, etc. MPICH does allow these datatypes.
PERMANENT KEY VALUES
These are the same in C and Fortran
MPI_TAG_UB
- Largest tag value
MPI_HOST
- Rank of process that is host, if any
MPI_IO
- Rank of process that can do I/O
MPI_WTIME_IS_GLOBAL
- Has value 1 if
MPI_WTIME
is globally synchronized.
NULL OBJECTS
MPI_COMM_NULL
- Null communicator
MPI_OP_NULL
- Null operation
MPI_GROUP_NULL
- Null group
MPI_DATATYPE_NULL
- Null datatype
MPI_REQUEST_NULL
- Null request
MPI_ERRHANDLER_NULL
- Null error handler
PREDEFINED CONSTANTS
MPI_MAX_PROCESSOR_NAME
- Maximum length of name returned by
MPI_GET_PROCESSOR_NAME
MPI_MAX_ERROR_STRING
- Maximum length of string return by
MPI_ERROR_STRING
MPI_UNDEFINED
- Used by many routines to indicated undefined or unknown
integer value
MPI_UNDEFINED_RANK
- Unknown rank
MPI_KEYVAL_INVALID
- Special keyval that may be used to detect uninitialized
keyvals.
MPI_BSEND_OVERHEAD
- Add this to the size of a
MPI_BSEND
buffer for each
outstanding message
MPI_PROC_NULL
- This rank may be used to send or receive from no-one.
MPI_ANY_SOURCE
- In a receive, accept a message from anyone.
MPI_ANY_TAG
- In a receive, accept a message with any tag value.
MPI_BOTTOM
- May be used to indicate the bottom of the address space
TOPOLOGY TYPES
MPI_GRAPH
- General graph
MPI_CART
- Cartesian grid
MPI STATUS
The
MPI_Status
datatype is a structure. The three elements for use
by programmers are
MPI_SOURCE
- Who sent the message
MPI_TAG
- What tag the message was sent with
MPI_ERROR
- Any error return
SPECIAL MPI TYPES AND FUNCTIONS
MPI_Aint
- C type that holds any valid address.
MPI_Handler_function
- C function for handling errors (see
MPI_Errhandler_create
) .
MPI_User_function
- C function to combine values (see collective operations
and
MPI_Op_create
)
MPI_Copy_function
- Function to copy attributes (see
MPI_Keyval_create
)
MPI_NULL_COPY_FN
- Predefined copy function
MPI_Delete_function
- Function to delete attributes (see
MPI_Keyval_create
)
MPI_NULL_DELETE_FN
- Predefined delete function
MPI_DUP_FN
- Predefined duplication function
MPI_ERRORS_ARE_FATAL
- Error handler that forces exit on error
MPI_ERRORS_RETURN
- Error handler that returns error codes (as value of
MPI routine in C and through last argument in Fortran)