// returns result of function
static <A> A benchForNSeconds2(double n, S desc default str(f), IF0<A> f) {
  benchForNSeconds2(n, r { f! });
  ret f!;
}

// returns minimal time needed
// TODO: sub-second duration
static long benchForNSeconds2(S desc, Runnable r, double n, int innerRepetitions) {
  long start = sysNow(), min = -1, print = sysNow();
  int seconds = 1;
  while (seconds <= n) {
    long time = sysNow();
    for (int i = 0; i < innerRepetitions; i++)
      r.run();
    long now = sysNow();
    time = now-time;
    min = min < 0 ? time : min(min, time);
    if (now >= start+seconds*1000) {
      printAndSetConsoleTitle(min + " ms: " + desc + " (" + seconds + "/" + (n*(long) innerRepetitions) + " s, last=" + time + " ms)");
      ++seconds;
    }
  }
  ret min;
}

Began life as a copy of #1007922