code: function millerRabinInt(x, b) {
    if (mr_x1.length!=x.length) {
      mr_x1=dup(x);
      mr_r=dup(x);
      mr_a=dup(x);
    }
  
    copyInt_(mr_a, b);
    return millerRabin(x, mr_a);
  }
docs: does a single round of Miller-Rabin base b consider x to be a possible prime? x is a bigInt, and b is an integer, with b<x