krl-stdlib/src/asyncSort.ts

Standard library for KRL

export async function asyncSort(
  array: any[],
  comparator: (a: any, b: any) => Promise<number>
) {
  var N = array.length;
  if (N < 2) {
    return array;
  }
  var other = Array(N);

  // alternative: var strideLen = N/2 / Math.abs(1 << (Math.ceil(Math.log2(N)) - 1));
  var strideLen = N;
  while (strideLen > 1) {
    strideLen /= 2;
  }

  // alternative: first strideLen *= 2 and do a pre-pass for size-2 strides only
  do {
    var stride = strideLen;
    var read1 = 0;
    do {
      var startRead2 = Math.ceil(stride);
      var read2 = startRead2;
      var mergeEnd = Math.ceil(stride + strideLen);
      stride += 2 * strideLen;
      var write = read1;
      while (read1 < startRead2 && read2 < mergeEnd) {
        other[write++] =
          array[
            (await comparator(array[read1], array[read2])) <= 0
              ? read1++
              : read2++
          ];
      }
      while (read1 < startRead2) {
        other[write++] = array[read1++];
      }
      while (read2 < mergeEnd) {
        other[write++] = array[read2++];
      }
      read1 = mergeEnd;
    } while (stride < N);

    var temp = array;
    array = other;
    other = temp;
    strideLen *= 2;
  } while (strideLen < N);

  return array;
}