Performance Optimization and Modeling of Fine-Grained Irregular Communication in UPC

Listing 8

The computational kernel of an existing 2D heat equation solver.

	#define idx(i, k) ((i) ∗ n + (k))
	for (it = 1; it ≤ itmax; it++) {
	double^∗phi = (double^∗) xphi[MYTHREAD];
	int i, k;
	/∗ communication per time step ∗/
	halo_exchange_intrinsic();
	/∗ computation per time step ∗/
	for (i = 1; i < m − 1; i++)
	for (k = 1; k < n − 1; k++)
	phin[idx(i, k)] = ((phi[idx(i + 1, k)] + phi[idx(i − 1, k)] − 2 ∗ phi[idx(i, k)]) ∗ dy2i + (phi[idx(i, k + 1)] + phi[idx(i, k − 1)] − 2 ∗ phi[idx(i, k)]) ∗ dx2i) ∗ dt;
	/∗ copying the content of phin to phi, checking convergence etc. ∗/
	// …
	}