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81 lines (70 loc) · 2.25 KB
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import java.util.BitSet;
public class MicroBenchmarking {
BitSet primes = new BitSet();
int prevMaxNum = -1;
public MicroBenchmarking() {
}
public boolean isPrime(int num) {
int maxCandidate = (int) Math.sqrt(num);
for (int i = 2; i <= maxCandidate; i++)
if (num % i == 0)
return false;
return true;
}
public boolean isPrime2(int num) {
if (num < 2)
return false;
if (num == 2)
return true;
if (primes.get(num))
return false;
if (num <= prevMaxNum)
return !primes.get(num);
int maxMultiple = 0;
int nextNum = 0;
int i = 4;
int p = 2;
if (prevMaxNum != -1) {
i = (prevMaxNum >> 1) * 2 + 2;
p = prevMaxNum;
}
for (; i <= num; i += 2)
primes.set(i);
for (i = 3; i <= num; i += 2) {
maxMultiple = num / i;
for (int j = p == 2? p: (p / i) + 1; j <= maxMultiple; j++) {
nextNum = i * j;
if (!primes.get(nextNum))
primes.set(nextNum);
}
}
prevMaxNum = num;
System.out.println(primes);
return !primes.get(num);
}
public static void main(String[] args) {
MicroBenchmarking mb = new MicroBenchmarking();
// warmup period
/* System.out.println("Finished warmup period");
long start = System.currentTimeMillis();
long end = System.currentTimeMillis();
for (int i = 0; i < 5000000; i++) {
start = System.currentTimeMillis();
mb.isPrime2(i);
end = System.currentTimeMillis();
}
System.out.println("Finished warmup period");
start = System.currentTimeMillis();
for (int i = 1001; i < 5000000; i++)
mb.isPrime2(i);
end = System.currentTimeMillis();
System.out.println("Time taken " + (end - start) + " ms.");
*/
//for (int i = 4; i <= 100; i++)
// System.out.println(i + " is prime " + mb.isPrime2(i));
System.out.println(mb.isPrime2(2));
System.out.println(mb.isPrime2(3));
System.out.println(mb.isPrime2(6));
System.out.println(mb.isPrime2(231));
}
}