uni/inf2440/hw4/Parallel.java

class Parallel extends Oblig4 {
	int nThreads = Math.min(
		Runtime.getRuntime().availableProcessors(),
		16);

	Parallel(NPunkter17 points) {
		super(points);
		name = "Parallel";
	}

	@Override
	void solve() {
		MinMaxXY minmax = findMinMax();
		MAX_X = x[minmax.maxX];
		MAX_Y = y[minmax.maxY];

		IntList indexes = new IntList(n);
		for (int i = 0; i < n; ++i)
			indexes.add(i);
	}

	class MinMaxXY {
		int minX, maxX, maxY;
	}

	class FindMinMaxWorker extends Thread {
		int start, end;
		int minX, maxX, maxY;
		FindMinMaxWorker(int start, int end) {
			this.start = start;
			this.end = end;
			this.minX = start;
			this.maxX = start;
			this.maxY = start;
		}

		public void run() {
			for (int i = start + 1; i < end; ++i) {
				if (x[i] < x[minX])
					minX = i;
				if (x[i] > x[maxX])
					maxX = i;
				if (y[i] > y[maxY])
					maxY = i;
			}
		}
	}

	MinMaxXY findMinMax() {
		FindMinMaxWorker[] workers = new FindMinMaxWorker[nThreads];

		int d = n / nThreads;
		for (int i = 0; i < nThreads; ++i) {
			workers[i] = new FindMinMaxWorker(
				d * i,
				(i == nThreads - 1
					? n - 1
					: d * (i + 1)));
			workers[i].start();
		}

		MinMaxXY minmax = new MinMaxXY();
		for (FindMinMaxWorker w: workers) {
			try { w.join(); } catch (InterruptedException ex) {}

			if (x[w.minX] < x[minmax.minX])
				minmax.minX = w.minX;
			if (x[w.maxX] > x[minmax.maxX])
				minmax.maxX = w.maxX;
			if (y[w.maxY] > y[minmax.maxY])
				minmax.maxY = w.maxY;
		}

		return minmax;
	}
}