What is the cost of a function call?

Question

Compared to

• Simple memory access
• Disk access
• Memory access on another computer(on the same network)
• Disk access on another computer

Answer 1

This link comes up a lot in Google. For future reference, I ran a short program in C# on the cost of a function call, and the answer is: "about six times the cost of inline". Below are details, see //Output at the bottom. UPDATE: To better compare apples with apples, I changed Class1.Method to return 'void', as so: public void Method1 () { // return 0; }
Still, inline is faster by 2x: inline (avg): 610 ms; function call (avg): 1380 ms. So the answer, updated, is "about two times".

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

namespace FunctionCallCost { class Program { static void Main(string[] args) { Debug.WriteLine("stop1"); int iMax = 100000000; //100M DateTime funcCall1 = DateTime.Now; Stopwatch sw = Stopwatch.StartNew();

        for (int i = 0; i < iMax; i++)
        {
            //gives about 5.94 seconds to do a billion loops, 
          // or 0.594 for 100M, about 6 times faster than
            //the method call.
        }

        sw.Stop(); 

        long iE = sw.ElapsedMilliseconds;

        Debug.WriteLine("elapsed time of main function (ms) is: " + iE.ToString());

        Debug.WriteLine("stop2");

        Class1 myClass1 = new Class1();
        Stopwatch sw2 = Stopwatch.StartNew();
        int dummyI;
        for (int ie = 0; ie < iMax; ie++)
        {
          dummyI =  myClass1.Method1();
        }
        sw2.Stop(); 

        long iE2 = sw2.ElapsedMilliseconds;

        Debug.WriteLine("elapsed time of helper class function (ms) is: " + iE2.ToString());

        Debug.WriteLine("Hi3");


    }
}

// Class 1 here using System; using System.Collections.Generic; using System.Linq; using System.Text;

namespace FunctionCallCost { class Class1 {

    public Class1()
    {
    }

    public int Method1 ()
    {
        return 0;
    }
}

}

// Output: stop1 elapsed time of main function (ms) is: 595 stop2 elapsed time of helper class function (ms) is: 3780

stop1 elapsed time of main function (ms) is: 592 stop2 elapsed time of helper class function (ms) is: 4042

stop1 elapsed time of main function (ms) is: 626 stop2 elapsed time of helper class function (ms) is: 3755