import jdk.incubator.vector.*;

static int countDifferingBits_1024bit_vectorAPI(long[] array1, long[] array2, int i1) {

  VectorSpecies<Long> SPECIES = LongVector.SPECIES_PREFERRED;

  int diff = 0;

  int n = 1024/64;

  var upperBound = SPECIES.loopBound(n);

  var i = 0;

  for (; i < upperBound; i += SPECIES.length()) {

    var vector1 = LongVector.fromArray(SPECIES, array1, i);

    var vector2 = LongVector.fromArray(SPECIES, array2, i1+i);

    var xored = vector1.lanewise(VectorOperators.XOR, vector2);

    var bitCount = xored.lanewise(VectorOperators.BIT_COUNT);

    diff += (int) bitCount.reduceLanes(VectorOperators.ADD);

  } 

  // Compute elements not fitting in the vector alignment.

  for (; i < n; i++)

    diff += Long.bitCount(array1[i]^array2[i1+i]);

  ret diff;

}