void mg_mpi(int* data, const unsigned long n, const int rank, const int size, const MPI_Comm comm) {
// root tells each process how much data to expect.
unsigned long partition_size;
if(rank == 0) {
partition_size = n / size;
// TODO handle invalid multiplicity (eg 100 / 8 = 12.5)
}
MPI_Bcast( &partition_size, 1, MPI_UNSIGNED_LONG, 0, comm );
log(LOG_DEBUG, "part size: %u\n", partition_size);
// allocate a partition of the correct size to work in.
int* partition = (int*)malloc( partition_size * sizeof(int) );
// scatter data to the partitions
MPI_Scatter( data, partition_size, MPI_INT, partition, partition_size, MPI_INT, 0, comm );
// clear initial data, to avoid confusion.
if(rank == 0) {
memset(data, 0, n);
}
// sort inividual pieces using mergesort
sort_partition(&partition, partition_size);
// gather results up the tree, merging 2 pieces at each step, until results
// end up in the root. they are stored in data.
collect_results(&data, n, &partition, &partition_size, rank, size, comm);
// partition buffer is no longer needed so free it.
free( partition );
}
void OrbLB::qsort(int x, int p, int r)
{
if (p<r) {
int q = sort_partition(x, p, r);
//CmiPrintf("midpoint: %d %d %d\n", p,q,r);
qsort(x, p, q-1);
qsort(x, q+1, r);
}
}
