CREATE_MPI_DATATYPE(MPI_2INT, int_int);
CREATE_MPI_DATATYPE(MPI_2FLOAT, float_float);
CREATE_MPI_DATATYPE(MPI_2DOUBLE, double_double);
CREATE_MPI_DATATYPE(MPI_2INT, int_int);
CREATE_MPI_DATATYPE(MPI_2FLOAT, float_float);
CREATE_MPI_DATATYPE(MPI_2DOUBLE, double_double);