// select a random subset of the keys, with an optional random population of keys inbetween those
// that are present
// return a value with the search position
private static List<Integer> randomKeys(
Iterable<Integer> canonical, boolean mixInNotPresentItems) {
ThreadLocalRandom rnd = ThreadLocalRandom.current();
boolean useFake = mixInNotPresentItems && rnd.nextBoolean();
final float fakeRatio = rnd.nextFloat();
List<Integer> results = new ArrayList<>();
Long fakeLb = null, fakeUb = null;
for (Integer v : canonical) {
if (!useFake
|| fakeLb == null
|| (fakeUb == null ? v - 1 : fakeUb) <= fakeLb + 1
|| rnd.nextFloat() < fakeRatio) {
// if we cannot safely construct a fake value, or our randomizer says not to, we emit the
// next real value
results.add(v);
fakeLb = v.longValue();
fakeUb = null;
} else {
// otherwise we emit a fake value in the range immediately proceeding the last real value,
// and not
// exceeding the real value that would have proceeded (ignoring any other suppressed real
// values since)
if (fakeUb == null) fakeUb = v.longValue() - 1;
long mid = (fakeLb + fakeUb) / 2;
assert mid < fakeUb;
results.add((int) mid);
fakeLb = mid;
}
}
final float useChance = rnd.nextFloat();
return Lists.newArrayList(filter(results, (x) -> rnd.nextFloat() < useChance));
}
