// returns result of function

static <A> A benchForNSeconds(double n, S desc default str(f), IF0<A> f) {

  benchForNSeconds(r { f! }, n);

  ret f!;

}

// returns minimal time needed

static long benchForNSeconds(S desc default str(r), Runnable r, double n) {

  long start = sysNow(), min = -1, print = sysNow();

  int seconds = 1;

  long count = 0, sum = 0;

  while (seconds <= n) {

    long time = nanos();

    r.run();

    ++count;

    time = nanos()-time;

    min = min < 0 ? time : min(min, time);

    sum += time;

    double avg = doubleRatio(sum, count);

    if (sysNow() >= start+seconds*1000) {

      printAndSetConsoleTitleIfMain(

        "n=" + n2(count) + ", avg=" + formatDouble(nanosToMS(avg), 3) + " ms, " +

        "min=" + formatDouble(nanosToMS(min), 3) + " ms: " +

        desc + " (" + seconds + "/" + n + " s, last=" + formatDouble(nanosToMS(time), 3) + " ms, " + n2(count) + "/s)");

      ++seconds;

      count = sum = 0;

    }

  }

  ret min;

}