Merging sorted sequences

Given are two sorted arrays A,B of n integers (assume all of them are distinct). The task is to compute a sorted array containg all elements from A and B/

The simplest sequential way is as follows: 

input int A[_], B[_];
int n = A.size, m = B.size;
output int C[n + m];
int i = 0, j = 0, k = 0;

while (i < n || j < m)
  if (i == n)
    C[k++] = B[j++];
  else if (j == m)
    C[k++] = A[i++];
  else if (A[i] < B[j])
    C[k++] = A[i++];
  else
    C[k++] = B[j++];
A O(log n) time and linear work algorithm is as follows: 
int merge(int A[_], int B[_], int offs) {
  int n = A.size, m = B.size;

  // if sizes are small, just merge sequentially
  if (A.size <= bs && B.size <= bs) 
    merge_seq(A,B,offs);
  else {
    int k = 1 + (n - 1) / bs;
    int X[k];
    pardo(i : k) X[i] = binary_search(A[i * bs], B);

    // copy elemets from B smaller than any of A
    if (X[0] > 0) pardo(i : X[0]) C[i + offs] = B[i];

    pardo(i : k) {
      int nn = bs;
      if (i == k - 1) nn = n - i * bs;
      int AA[nn];
      pardo(j : nn) AA[j] = A[i * bs + j];

      int top = m;
      if (i < k - 1) top = X[i + 1];
      int mm = top - X[i];

      if (mm == 0)
        pardo(j : nn) C[offs + i * bs + j + X[i]] = AA[j];
      else {
        int BB[mm];
        pardo(j : mm) BB[j] = B[X[i] + j];
        merge(BB, AA, offs + i * bs + X[i]);
      }
    }
  }
}