DecodeHexBenchmark Class — netty Architecture

Source Code

microbench/src/main/java/io/netty/handler/codec/http/DecodeHexBenchmark.java lines 37–177

@State(Scope.Benchmark)
@Warmup(iterations = 5, time = 1)
@Measurement(iterations = 5, time = 1)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
public class DecodeHexBenchmark extends AbstractMicrobenchmark {

    @Param({
            //with HEX chars
            "135aBa9BBCEA030b947d79fCcaf48Bde",
            //with HEX chars + 'g'
            "4DDeA5gDD1C6fE567E1b6gf0C40FEcDg",
    })
    private String hex;
    // Needs to specify a high number of inputs to allow the current strategy
    // on nextHexDigits to produce enough branch-misses
    @Param({ "2048" })
    private int inputs;
    private char[][] hexDigits;
    private static final long SEED = 1578675524L;
    private long next;

    @Setup
    public void init() {
        final char[] hexCh = hex.toCharArray();
        next = 0;
        inputs = MathUtil.findNextPositivePowerOfTwo(inputs);
        hexDigits = new char[inputs][];
        hexDigits[0] = hexCh;
        if (inputs > 1) {
            final Random rnd = new Random(SEED);
            for (int i = 1; i < inputs; i++) {
                hexDigits[i] = shuffle(Arrays.copyOf(hexCh, hexCh.length), rnd);
            }
        }
    }

    // https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
    private static char[] shuffle(char[] chars, Random rnd) {
        int index;
        char tmp;
        for (int i = chars.length - 1; i > 0; i--) {
            index = rnd.nextInt(i + 1);
            tmp = chars[index];
            chars[index] = chars[i];
            chars[i] = tmp;
        }
        return chars;
    }

    private int nextHexDigits() {
        final int idx = (int) (next & (inputs - 1));
        next++;
        return idx;
    }

    @Benchmark
    @CompilerControl(Mode.DONT_INLINE)
    public long hexDigits() {
        long v = 0;
        final char[] hexDigits = this.hexDigits[nextHexDigits()];
        for (int i = 0, size = hexDigits.length; i < size; i++) {
            v += StringUtil.decodeHexNibble(hexDigits[i]);
        }
        return v;
    }

    @Benchmark
    @CompilerControl(Mode.DONT_INLINE)
    public long hexDigitsWithChecks() {
        long v = 0;
        final char[] hexDigits = this.hexDigits[nextHexDigits()];
        for (int i = 0, size = hexDigits.length; i < size; i++) {
            v += decodeHexNibbleWithCheck(hexDigits[i]);
        }
        return v;
    }

    @Benchmark
    @CompilerControl(Mode.DONT_INLINE)
    public long hexDigitsOriginal() {
        long v = 0;