Does my code run exactly?

Question

5.00/5 (1 vote)

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I'm not really it's exactly because it's so quickly.
Please check help me!

C#

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            var sw = Stopwatch.StartNew();
            double nano = 0.00;
            nano += sw.Elapsed.TotalMilliseconds * 1000000;

            int a, b;
            a = 1; b = 2;

            // ______________________________________________________________
            sw.Start();

            for (int i = 0; i < 10000000; i++) // Run 10 milliions times
            {
                int c = (a + b);
                i++;
            }
            sw.Stop();
            // __________________________________________________________________

            Console.WriteLine("Nanoseconds time is: {0} (ns)", nano.ToString());
            Console.ReadLine();
        }
    }
}

And some results i received:

C#

Nanoseconds time is: 2400 (ns)

Another time, it's 2500, 2700
Only 2k nanoseconds for 10 millions times?

And here is my hardware:
Intel core i5 4200M
RAM: 2Gb
OS: Windows 8.1
Debugger: Visual Studio Debugger

Posted 8-Sep-14 3:21am

user8x86

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Comments

ZurdoDev 8-Sep-14 9:31am

What?

Nathan Minier 8-Sep-14 9:39am

I'd also like to throw in that because of register size vs the size of the operations you're doing, you can do 2 iterations per cycle per thread, and your chipset is 2.5gHz stock, which is 2.5 billion operations per second. Just saying.

user8x86 8-Sep-14 9:51am

Thanks for the advance

2 solutions

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OriginalGriff · Accepted Answer · 2014-09-08T03:32:00

It's difficult to tell - but that isn't 10,000,000 iterations: it's only 5,000,000 because you increment i twice in each loop.

The problem is that the bulk of the loop is a "fixed calculation" so any half decent optimiser will happily take out the loop content (and could easily dispose of the loop itself as well). But...if you are running this in the debugger, then optimisations are pretty much disabled, so it shouldn't be removed.

And no, it's not the number of nano seconds... You print a value you calculate before the loop is even started!, and the Stopwatch class isn't accurate to nanoseconds anyway!
Try this:

C#

int a, b;
a = 1; b = 2;

// ______________________________________________________________
Stopwatch sw = Stopwatch.StartNew();
for (int i = 0; i < 10000000; i++) // Run 10 milliions times
    {
    int c = (a + b);
    }
sw.Stop();
// __________________________________________________________________

Console.WriteLine("Milliseconds time is: {0}ms", sw.ElapsedMilliseconds);
Console.ReadLine();

CPallini · Accepted Answer · 2014-09-08T03:34:00

Solution 2

The result is incorrect. You have to move the following line

Quote:
nano += sw.Elapsed.TotalMilliseconds * 1000000;

after the sw.Stop(); statement.

Posted 8-Sep-14 3:34am

CPallini

Comments

user8x86 8-Sep-14 9:49am

Thank Mr.CPallini. That worked.

CPallini 8-Sep-14 10:53am

You are welcome.