Looking through the source where the tests are conducted,

for (double x = 1; x < 1000000000; x += 0.5) {

      counter++;
      int64_t tmp;
      if (to_int64_simple(x, &tmp)) {
        sum += tmp;
      }

}

The fractional part is always mostly 0.5, or 0.10000... While that shouldn't really affect things, I think a proper test would sample randomly, though this runs into the problem of the random number generator itself influencing the time spent, so I can see the appeal for this method. Perhaps generating a random float array with N elements and calculating the results for x + arr[x%N] would accomplish this.