Allreduce

MPI_Allreduce(void *operand, void *result, int ct, MPI_Datatype dt, MPI_Op op, MPI_Comm comm);

float local_x[] /* in */,

float local_y[] /* in */,

int n_bar /* in */) {

float local_dot;

float dot = 0.0;

float Serial_dot(float x[], float y[], int m);

local_dot = Serial_dot(local_x, local_y, n_bar);

MPI_Allreduce(&local_dot, &dot, 1, MPI_FLOAT,

MPI_SUM, MPI_COMM_WORLD);

return dot;

} /* Parallel_dot */

MPI_Allreduce(void *operand, void *result, int ct, MPI_Datatype dt, MPI_Op op, MPI_Comm comm);