AOC Day 02 Java Vector API solution

Day02.java

package de.sirywell.aoc2022.java.day02;

import jdk.incubator.vector.ByteVector;
import jdk.incubator.vector.ShortVector;
import jdk.incubator.vector.VectorMask;
import jdk.incubator.vector.VectorShuffle;
import jdk.incubator.vector.VectorSpecies;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;

import static jdk.incubator.vector.VectorOperators.ADD;
import static jdk.incubator.vector.VectorOperators.FIRST_NONZERO;
import static jdk.incubator.vector.VectorOperators.XOR;

public class Day02 {

  private static final VectorSpecies<Byte> BYTE_V = ByteVector.SPECIES_PREFERRED;
  private static final VectorSpecies<Short> SHORT_V = ShortVector.SPECIES_PREFERRED;
  private static final VectorShuffle<Byte> ROTATE_ONE = VectorShuffle.iota(BYTE_V, 1, 1, true);
  private static final VectorShuffle<Byte> ROTATE_M_ONE = VectorShuffle.iota(BYTE_V, -1, 1, true);
  private static final VectorMask<Byte> SELECT_AT_EVEN = VectorMask.fromLong(BYTE_V, 0x5555555555555555L);
  private static final VectorMask<Byte> SELECT_AT_ODD = SELECT_AT_EVEN.not();

  public static void main(String[] args) throws IOException {
    String s = Files.readString(Path.of("src/main/resources/day02/input.txt"));
    byte[] raw = s.replace(" ", "")
        .replace("\r", "")
        .replace("\n", "").getBytes(StandardCharsets.UTF_8);
    int l = raw.length;
    int step = BYTE_V.length() << 1;
    int bound = l & -step;
    ShortVector firstSum = ShortVector.zero(SHORT_V);
    ShortVector secondSum = ShortVector.zero(SHORT_V);
    int offset;
    for (offset = 0; offset < bound; offset += step) {
      ByteVector l0 = ByteVector.fromArray(BYTE_V, raw, offset);
      ByteVector l1 = ByteVector.fromArray(BYTE_V, raw, offset + BYTE_V.length());
      ByteVector as = l0.lanewise(XOR, l0, SELECT_AT_ODD);
      ByteVector bs = l0.lanewise(XOR, l0, SELECT_AT_EVEN);
      as = as.lanewise(FIRST_NONZERO, l1.rearrange(ROTATE_M_ONE));
      bs = bs.rearrange(ROTATE_ONE).lanewise(FIRST_NONZERO, l1);
      as = as.sub((byte) 'A');
      bs = bs.sub((byte) 'X');
      ByteVector first = eval(as, bs);
      firstSum = firstSum.add(first.castShape(SHORT_V, 0));
      firstSum = firstSum.add(first.castShape(SHORT_V, 1));
      bs = modBy3(bs.add(as).add((byte) 2));
      ByteVector second = eval(as, bs);
      secondSum = secondSum.add(second.castShape(SHORT_V, 0));
      secondSum = secondSum.add(second.castShape(SHORT_V, 1));
    }
    int firstResult = firstSum.reduceLanes(ADD);
    int secondResult = secondSum.reduceLanes(ADD);
    for (; offset < raw.length; offset += 2) {
      int opponent = (raw[offset] - 'A');
      int self = (raw[offset + 1] - 'X');
      firstResult += (4 - opponent + self) % 3 * 3 + self + 1;
      self = (opponent + self + 2) % 3;
      secondResult += (4 - opponent + self) % 3 * 3 + self + 1;
    }
    System.out.println(firstResult);
    System.out.println(secondResult);
  }

  private static ByteVector eval(ByteVector opponent, ByteVector self) {
    final byte one = 1;
    final byte three = 3;
    ByteVector four = ByteVector.broadcast(BYTE_V, 4);
    ByteVector beforeMod = four.sub(opponent).add(self);
    return modBy3(beforeMod)
        .mul(three).add(self).add(one);
  }

  private static ByteVector modBy3(ByteVector vector) {
    final byte three = 3;
    return vector.sub(vector.div(three).mul(three));
  }
}