Tree Structured Communication

int I_receive(

int stage /* in */,

int my_rank /* in */,

int* source_ptr /* out */) {

int power_2_stage;

/* 2^stage = 1 << stage */

power_2_stage = 1 << stage;

if ((power_2_stage <= my_rank) &&

(my_rank < 2*power_2_stage)){

*source_ptr = my_rank - power_2_stage;

return 1;

} else return 0;

} /* I_receive */

void Receive(

float* a_ptr /* out */,

float* b_ptr /* out */,

int* n_ptr /* out */,

int source /* in */) {

MPI_Status status;

MPI_Recv(a_ptr, 1, MPI_FLOAT, source, 0,

MPI_COMM_WORLD, &status);

MPI_Recv(b_ptr, 1, MPI_FLOAT, source, 1,

MPI_COMM_WORLD, &status);

MPI_Recv(n_ptr, 1, MPI_INT, source, 2,

MPI_COMM_WORLD, &status);

} /* Receive */

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