Lecture 7 - Parallel Sorting Algorithms

Question 1

MergeSort

Answer 1

SeqMerge ( int a[k], int b[k], int c[2k] )
{
int ap=0, bp=0, cp=0;
while ( cp < 2k ) { // assume a[k] = b[k] = ∞
if (a[ap]<b></b>

Question 2

Parallel MergeSort

Answer 2

void SParMergesort ( int *array, int n ) // in place
{
if (n==1) return; // nothing to sort
if (depth_limit_for_recursive_parallel_decomposition_reached())
SeqMergesort( array, n ); // switch to sequential
// parallel divide and conquer:
in parallel do {
SParMergesort ( array, n/2);
SParMergesort ( array + n/2, n-n/2 );
}
// now the two subarrays are sorted
seq SeqMerge ( array, n/2, n-n/2 );
}
void SeqMerge ( int *array, int n1, int n2 ) // sequential merge in place
{
// ... merge in O(n1+n2) steps ...
}