MPI

To be used for   MPI_REDUCE, MPI_ALLREDUCE, MPI_REDUCE_SCATTER, and MPI_SCAN

There are a number of predefined reduction operations for use with MPI_ALLREDUCE, MPI_EXSCAN, MPI_REDUCE, MPI_REDUCE_SCATTER, and MPI_SCAN.

To invoke a predefined operation, place any of the following reductions in variable op.

Operation

Description

MPI_BAND

bitwise AND

MPI_BOR

bitwise OR

MPI_BXOR

bitwise XOR

MPI_LAND

logical AND

MPI_LOR

logical OR

MPI_LXOR

logical XOR

MPI_MAX

maximum value

MPI_MAXLOC

maximum value and location

MPI_MIN

minimum value

MPI_MINLOC

minimum value and location

MPI_PROD

product

MPI_REPLACE

f(a,b) = b (the current value in the target memory is replaced by the value supplied by the origin)

MPI_SUM

sum

Source

MPI_Op_create

int MPI_Op_create(
  MPI_User_function *function,
  int commute,
  MPI_Op *op
);

source




MPI DATA types

Data type

Description

MPI_BYTE

Untyped byte data

MPI_LB

Explicit lower bound marker

MPI_PACKED

Packed data (byte)

MPI_UB

Explicit upper bound marker

Data types for C language bindings

Data type

Description

MPI_CHAR

8-bit character

MPI_DOUBLE

64-bit floating point

MPI_FLOAT

32-bit floating point

MPI_INT

32-bit integer

MPI_LONG

32-bit integer

MPI_LONG_DOUBLE

64-bit floating point

MPI_LONG_LONG

64-bit integer

MPI_LONG_LONG_INT

64-bit integer

MPI_SHORT

16-bit integer

MPI_SIGNED_CHAR

8-bit signed character

MPI_UNSIGNED

32-bit unsigned integer

MPI_UNSIGNED_CHAR

8-bit unsigned character

MPI_UNSIGNED_LONG

32-bit unsigned integer

MPI_UNSIGNED_LONG_LONG

64-bit unsigned integer

MPI_UNSIGNED_SHORT

16-bit unsigned integer

MPI_WCHAR

Wide (16-bit) unsigned character

Example to write a distributed 2D array 

https://stackoverflow.com/questions/33537451/writing-distributed-arrays-using-mpi-io-and-cartesian-topology