Why is long slower than int in x64 Java?

Question

I\'m running Windows 8.1 x64 with Java 7 update 45 x64 (no 32 bit Java installed) on a Surface Pro 2 tablet.

The code below takes 1688ms when the type of i is a long

Answer 1

I have just written a benchmark using caliper.

The results are quite consistent with the original code: a ~12x speedup for using int over long. It certainly seems that the loop unrolling reported by tmyklebu or something very similar is going on.

timeIntDecrements         195,266,845.000
timeLongDecrements      2,321,447,978.000

This is my code; note that it uses a freshly-built snapshot of caliper, since I could not figure out how to code against their existing beta release.

package test;

import com.google.caliper.Benchmark;
import com.google.caliper.Param;

public final class App {

    @Param({""+1}) int number;

    private static class IntTest {
        public static int v;
        public static void reset() {
            v = Integer.MAX_VALUE;
        }
        public static boolean decrementAndCheck() {
            return --v < 0;
        }
    }

    private static class LongTest {
        public static long v;
        public static void reset() {
            v = Integer.MAX_VALUE;
        }
        public static boolean decrementAndCheck() {
            return --v < 0;
        }
    }

    @Benchmark
    int timeLongDecrements(int reps) {
        int k=0;
        for (int i=0; i