Int32 vs Int64 performance on a 64 bit platform?

Question

My question is relatively simply. On 32bit platforms it's best to use Int32 as opposed to short or long due to to the cpu processing 32 bits at a time. So on a 64 bit architecture does this mean it's faster to use longs for performance? I created a quick and dirty app that copies int and long arrays to test the benchmarks. Here is the code(I did warn it's dirty):

static void Main(string[] args)
    {
        var lar = new long[256];

        for(int z = 1; z<=256;z++)
        {
            lar[z-1] = z;
        }
        var watch = DateTime.Now;
        for (int z = 0; z < 100000000; z++)
        {
            var lard = new long[256];
            lar.CopyTo(lard, 0);

        }
        var res2 = watch - DateTime.Now;

        var iar = new int[256];

        for (int z = 1; z <= 256; z++)
        {
            iar[z - 1] = z;
        }

        watch = DateTime.Now;

        for (int z = 0; z < 100000000; z++)
        {
            var iard = new int[256];
            iar.CopyTo(iar, 0);

        }

        var res1 = watch - DateTime.Now;
        Console.WriteLine(res1);
        Console.WriteLine(res2);


    }

The results it produces make long about 3 times as fast as int. Which makes me curious to whether I should start using longs for counters and such. I also did a similar counter test and long was insignificantly faster. Does anybody have any input on this? I also understand even if longs are faster they will still take up twice as much space.

Answer 1

No. It takes longer to do 64-bit on a 32-bit CPU because the CPU can only handle 32-bits at a time. A 64-bit CPU will just ignore the missing 32-bits.

Also, try not to preemptively optimize too much. Only optimize when there is a noticeable bottleneck.