Time required for a process to complete

Question

I am new to C# world. I am attempting to calculate time taken by a algorithum for the purpose of comparison. Following code measures the elapsed time from when a subroutine is called until the subroutine returns to the main program.This example is taken from "Data structures through C#" by Michael McMillan. After running this program the output is Time=0, which is incorrect. The program appears to be logically correct. Can anybody help me. Following is the code

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

namespace Chap1
{
    class chap1
    {
        static void Main()
        {
            int[] nums = new int[100000];
            BuildArray(nums);
            Timing tObj = new Timing();
            tObj.startTime();
            DisplayNums(nums);
            tObj.stopTime();
            Console.WriteLine("Time: " + tObj.result().TotalSeconds);
            Console.WriteLine("Start Time: " + tObj.startTime().TotalSeconds);
            Console.WriteLine("Duration : " + tObj.result().TotalSeconds);
            Console.ReadKey();
        }
        static void BuildArray(int[] arr)
        {
            for (int i = 0; i <= 99999; i++)
                arr[i] = i;
        }
        static void DisplayNums(int[] arr)
        {
            for (int i = 0; i <= arr.GetUpperBound(0); i++)
                Console.WriteLine(arr[i]);
        }
    }
class Timing
    {
        TimeSpan StartTiming;
        TimeSpan duration;
        public Timing()
        {
            StartTiming = new TimeSpan(0);
            duration = new TimeSpan(0);
        }
        public TimeSpan startTime()
        {
            GC.Collect();


     GC.WaitForPendingFinalizers();
            StartTiming = Process.GetCurrentProcess().Threads[0].UserProcessorTime;
            return StartTiming;
        }
        public void stopTime()
        {
            duration = Process.GetCurrentProcess().Threads[0].UserProcessorTime.Subtract(StartTiming);

        }
        public TimeSpan result()
        {
            return duration;
        }
    }
}

Answer 1

The Stopwatch class is designed for this.

UserProcessorTime doesn't begin to have the resolution necessary to measure counting to 100000 in a for loop. Your WriteLine calls won't be included in user time as they are I/O time. Your code might not be running on thread 0. User time isn't updated except at context switches. When you print startTime, you're changing the stored value. There are probably some other things that can go wrong I haven't thought of.

I strongly suggest you use the Stopwatch class which takes advantage of the CPU's performance counters.