sequential is now really fast

inf2440/hw2/Main.java

@@ -25,8 +25,14 @@ class Main {
 			t.start();
 			long n = maxNum * maxNum;
 			for (long j = n; j >= n - 100; --j) {
+
+				Timer t2 = new Timer().start();
 				long[] factors = s.factor(sieve, j);
+				System.out.println(
+					t2.end().prettyTime()+": "+
+					Util.factors(j, factors));
 
+				/*
 				if (j > (n - 5) || j < (n - 95)) {
 					if (j == n - 96)
 						System.out.println(".............");
@@ -34,6 +40,7 @@ class Main {
 					System.out.println(
 						Util.factors(j, factors));
 				}
+				*/
 			}
 			t.end();
 		}
@@ -50,7 +57,8 @@ class Main {
 		Sequential sseq = new Sequential();
 		Parallel spar = new Parallel();
 
-		boolean findPrimes = true;
+		//boolean findPrimes = true;
+		boolean findPrimes = false;
 		boolean factor = true;
 
 		int maxNum = Integer.parseInt(args[0]);
@@ -73,11 +81,17 @@ class Main {
 
 			System.out.println("\nFactoring sequentially...");
 			Timer seq = testFactor(sseq, maxNum, sieve);
-			System.out.println("Sequential: "+seq.prettyTime());
+			Timer seqAvg = new Timer(seq.time / 100);
+			System.out.println(
+				"Sequential: "+seq.prettyTime()+
+				" ("+seqAvg.prettyTime()+" per factor)");
 
 			System.out.println("\nFactoring in parallel...");
 			Timer par = testFactor(spar, maxNum, sieve);
-			System.out.println("Parallel: "+par.prettySpeedup(seq));
+			Timer parAvg = new Timer(par.time / 100);
+			System.out.println(
+				"Parallel: "+par.prettySpeedup(seq)+
+				" ("+parAvg.prettyTime()+" per factor)");
 		}
 
 		spar.stopThreads();

inf2440/hw2/Sequential.java

@@ -13,28 +13,31 @@ class Sequential implements Solver {
 
 		ArrayList<Long> arr = new ArrayList<>();
 
-		while (true) {
-			long prime;
-			for (prime = 2; prime <= sqrt; ++prime) {
-				if (num % prime == 0) {
-					arr.add(new Long(prime));
-					num /= prime;
-					break;
-				}
-			}
+		// Easier to assume all primes are odd
+		while (num % 2 == 0) {
+			arr.add(new Long(2));
+			num /= 2;
+		}
 
-			if (prime > sqrt) {
-				arr.add(new Long(num));
-				break;
-			}
+		// Find factors
+		long prime;
+		for (prime = 3; prime <= sqrt; prime += 2) {
+			if (!sieve.isPrime((int)prime))
+				continue;
 
-			if (num <= sqrt && sieve.isPrime((int)num)) {
-				if (num != 1)
-					arr.add(new Long(num));
-				break;
+			if (num % prime == 0) {
+				do {
+					arr.add(new Long(prime));
+					num /= prime;
+				} while (num % prime == 0);
+				sqrt = (int)Math.sqrt(num);
 			}
 		}
 
+		// Add num if we didn't find all the factors before sqrt(num)
+		if (num != 1)
+			arr.add(new Long(num));
+
 		long[] a = new long[arr.size()];
 		for (int i = 0; i < a.length; ++i) {
 			a[i] = arr.get(i);

inf2440/hw2/Timer.java

@@ -5,6 +5,11 @@ class Timer implements Comparable<Timer> {
 
 	private long start = 0;
 
+	Timer() {}
+	Timer(long time) {
+		this.time = time;
+	}
+
 	public Timer start() {
 		start = System.nanoTime();
 		return this;