uni/inf2440/hw1/Main.java

import java.util.Random;
import java.util.Arrays;

class Main {
	static void usage() {
		System.out.println("Usage: java Main <n> <k> [seq|par]");
		System.out.println("   or: java Main test");
	}

	static final int randSeed = 1337; // Just to keep things consistent

	static class Timer {
		long start = 0;
		long time = 0;

		void start() {
			start = System.nanoTime();
		}
		void end() {
			time = System.nanoTime() - start;
		}

		String prettyTime() {
			if (time < 1000)
				return time+"ns";
			else if (time < 1000000)
				return (time / 1000)+"μs";
			else if (time < 1000000000)
				return (time / 1000000)+"ms";
			else
				return (time / 1000000000)+"s";
		}

		String prettySpeedup(Timer base) {
			double speedup = (double)base.time / (double)time;
			return String.format("%s (%.2fx speedup)",
				prettyTime(), speedup);
		}
	}

	static class TestResult {
		Timer baseTime = null;
		Timer seqTime = null;
		Timer parTime = null;
		int n = 0;
		int k = 0;

		// Print a test result
		void print() {
			String tmpl =
				"\nTest results for n=%d, k=%d:\n"+
				"\tArrays.sort: %s\n"+
				"\tSequential:  %s\n"+
				"\tParallel:    %s\n";

			System.out.printf(tmpl,
				n, k, baseTime.prettyTime(),
				seqTime.prettySpeedup(baseTime),
				parTime.prettySpeedup(baseTime));
		}

		// Create a TestResult which is the average
		// of n other TestResults
		static TestResult avg(TestResult[] results) {
			TestResult ts = new TestResult();
			ts.baseTime = new Timer();
			ts.seqTime = new Timer();
			ts.parTime = new Timer();
			ts.n = results[0].n;
			ts.k = results[0].k;

			for (TestResult t: results) {
				if (t.n != ts.n)
					throw new RuntimeException("Bad n value");
				if (t.k != ts.k)
					throw new RuntimeException("Bad k value");

				ts.baseTime.time += t.baseTime.time;
				ts.seqTime.time += t.seqTime.time;
				ts.parTime.time += t.parTime.time;
			}

			ts.baseTime.time /= results.length;
			ts.seqTime.time /= results.length;
			ts.parTime.time /= results.length;
			return ts;
		}
	}

	static TestResult runTest(int[] a, int n, int k, Timer baseTime) {

		TestResult ts = new TestResult();

		Timer seqTime = new Timer();
		Timer parTime = new Timer();

		A2Solver seq = new Sequential();
		A2Solver par = new Parallel();

		int[] copy = new int[n];

		// Test seq
		System.arraycopy(a, 0, copy, 0, n);
		seqTime.start();
		seq.solveA2(copy, k);
		seqTime.end();

		// Test par
		System.arraycopy(a, 0, copy, 0, n);
		parTime.start();
		par.solveA2(copy, k);
		parTime.end();

		ts.baseTime = baseTime;
		ts.seqTime = seqTime;
		ts.parTime = parTime;
		ts.n = n;
		ts.k = k;
		return ts;
	}

	static void runTests() {
		int[] ns = { 100000000, 10000000, 1000000, 100000, 10000, 1000 };
		int[] ks = { 100, 20 };
		int iters = 7;

		for (int n: ns) {

			Timer baseTime = new Timer();

			// Construct array
			Random rand = new Random(randSeed);
			int[] a = new int[n];
			for (int i = 0; i < n; ++i) {
				a[i] = rand.nextInt();
			}

			// Time Arrays.sort()
			// I only do this once per n because it takes a long time.
			int[] copy = new int[n];
			System.arraycopy(a, 0, copy, 0, n);
			baseTime.start();
			Arrays.sort(copy);
			baseTime.end();

			for (int k: ks) {
				TestResult[] results = new TestResult[iters];
				for (int i = 0; i < iters; ++i) {
					results[i] = runTest(a, n, k, baseTime);
				}

				TestResult t = TestResult.avg(results);
				t.print();
			}
		}
	}

	public static void main(String[] args) {
		if (args.length < 1) {
			usage();
			System.exit(1);
		}

		if (args[0].equals("test")) {
			runTests();
			return;
		}

		A2Solver solver;
		int n, k;

		try {
			n = Integer.parseInt(args[0]);
			k = Integer.parseInt(args[1]);
			if (args.length == 3) {
				if (args[2].equals("seq"))
					solver = new Sequential();
				else if (args[2].equals("par"))
					solver = new Parallel();
				else {
					usage();
					System.exit(1);
					return;
				}
			} else {
				solver = new Sequential();
			}
		} catch (Exception ex) {
			System.out.println(ex.getMessage());
			System.out.println("");
			usage();
			System.exit(1);
			return;
		}

		Timer timer = new Timer();

		// Create array
		int[] a = new int[n];
		Random r = new Random(randSeed);
		for (int i = 0; i < n; ++i) {
			a[i] = r.nextInt();
		}

		// Solve
		timer.start();
		solver.solveA2(a, k);
		timer.end();

		// Print 
		for (int i = 0; i < k; ++i) {
			if (i != 0)
				System.out.print(" ");
			System.out.print(a[i]);
		}
		System.out.println("");

		// Print report info to stderr, so that
		// stdout is only the result
		System.err.printf("\nn=%d, k=%d, %s time: %s\n",
			n, k, solver.getClass().getName(), timer.prettyTime());
	}
}