how to always round up to the next integer [duplicate]

Answer 1

A proper benchmark or how the number may lie

Following the argument about Math.ceil(value/10d) and (value+9)/10 I ended up coding a proper non-dead code, non-interpret mode benchmark. I've been telling that writing micro benchmark is not an easy task. The code below illustrates this:

00:21:40.109 starting up....
00:21:40.140 doubleCeil: 19444599
00:21:40.140 integerCeil: 19444599
00:21:40.140 warming up...
00:21:44.375 warmup doubleCeil: 194445990000
00:21:44.625 warmup integerCeil: 194445990000
00:22:27.437 exec doubleCeil: 1944459900000, elapsed: 42.806s
00:22:29.796 exec integerCeil: 1944459900000, elapsed: 2.363s

The benchmark is in Java since I know well how Hotspot optimizes and ensures it's a fair result. With such results, no statistics, noise or anything can taint it.

Integer ceil is insanely much faster.

The code

package t1;

import java.math.BigDecimal;

import java.util.Random;

public class Div {
    static int[] vals;

    static long doubleCeil(){
        int[] v= vals;
        long sum = 0;
        for (int i=0;i0?String.format(msg, params):msg;
        System.out.printf("%tH:%