arraycmp.c

#include <jni.h>
#include <string.h>

static inline jlong vectorized_cmp(const jlong* s1, const jlong* s2, int size) {
    jlong result = 0;
    for (int i = 0; i < size; i++) {
        result |= s1[i] ^ s2[i];
    }
    return result;
}

JNIEXPORT jboolean JavaCritical_bench_LongArrayCompare_compare(jint a_len, jlong* a_raw,
                                                               jint b_len, jlong* b_raw,
                                                               jint size) {
#define STEP 64
    while (size >= STEP) {
        if (vectorized_cmp(a_raw, b_raw, STEP) != 0) {
            return JNI_FALSE;
        }
        a_raw += STEP;
        b_raw += STEP;
        size -= STEP;
    }
#undef STEP

    return vectorized_cmp(a_raw, b_raw, size) == 0 ? JNI_TRUE : JNI_FALSE;
}

JNIEXPORT jboolean Java_bench_LongArrayCompare_compare(JNIEnv* env, jobject unused,
                                                       jlongArray a, jbyteArray b, jint size) {
    void* a_raw = (*env)->GetPrimitiveArrayCritical(env, a, NULL);
    void* b_raw = (*env)->GetPrimitiveArrayCritical(env, b, NULL);

    jboolean result = JavaCritical_bench_LongArrayCompare_compare(0, a_raw, 0, b_raw, size);

    (*env)->ReleasePrimitiveArrayCritical(env, b, b_raw, JNI_ABORT);
    (*env)->ReleasePrimitiveArrayCritical(env, a, a_raw, JNI_ABORT);
    return result;
}

LongArrayCompare.java

package bench;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;

import java.util.Arrays;
import java.util.concurrent.ThreadLocalRandom;

@State(Scope.Benchmark)
public class LongArrayCompare {

    @Param({"10", "100", "1000"})
    private int size;

    private long[] a;
    private long[] b;

    @Setup
    public void setup() {
        a = ThreadLocalRandom.current().longs(size).toArray();
        b = a.clone();
        b[b.length - 1]++;
    }

    @Benchmark
    public boolean arraysEquals() {
        return Arrays.equals(a, b);
    }

    @Benchmark
    public boolean jniCritical() {
        return a.length == b.length && compare(a, b, a.length);
    }

    private static native boolean compare(long[] a, long[] b, int size);

    static {
        System.loadLibrary("arraycmp");
    }
}