performance consideration when using properties multiple times

Question

I am using CultureInfo.CurrentCulture when formating my strings using string.format

To quote this blog

This just has the implication that if you are using CurrentCulture a lot, it might be worth reading it into a private variable rather than making lots of calls to CultureInfo.CurrentCulture, otherwise you're using up clock cycles needlessly.

so as per this author

var culture = CultureInfo.CurrentCulture
string.Format(culture,"{0} some format string","some args");
string.Format(culture,"{0} some format string","some other args");

is better than

string.Format(CultureInfo.CurrentCulture,"{0} some format string","some args");
string.Format(CultureInfo.CurrentCulture,"{0} some format string","some other args");

as per MSDN, CultureInfo.CurrentCulture is a property

Is there a performance penalty associated when accessing a property multiple times ??

Also I did some emperical analysis and my tests show me that using a local variable is more expensive than using the property directly.

Stopwatch watch = new Stopwatch();

            int count = 100000000;
            watch.Start();
            for(int i=0;i<count;i++)
            {
                string.Format(CultureInfo.CurrentCulture, "{0} is my name", "ram");
            }


            watch.Stop();
                 //EDIT:Reset watch
                 watch.Reset();


            Console.WriteLine(watch.Elapsed);
            Console.WriteLine(watch.ElapsedMilliseconds);
            Console.WriteLine(watch.ElapsedTicks);


            Console.WriteLine("--------------------");
            var culture = CultureInfo.CurrentCulture;
            watch.Start();
            for (int i=0; i < count; i++)
            {
                string.Format(culture, "{0} is my name", "ram");
            }


            watch.Stop();

            Console.WriteLine(watch.Elapsed);
            Console.WriteLine(watch.ElapsedMilliseconds);
            Console.WriteLine(watch.ElapsedTicks);

Result:

00:00:29.6116306
29611
68922550970
--------------------
00:00:27.3578116
27357
63676674390

My tests show that using CultureInfo.CurrentCulture property is better than using local variable (which contradicts with the authors view). Or am I missing something here ?

Edit:I was not resetting the stopwatch before teh second iteration. hence the difference. resetting stopwatch, updating iteration count and result in this edit

Answer 1

You should only optimize CultureInfo.CurrentCulture into a local variable if a profiler shows it to be a significant problem in your code and also that putting into a local variable makes it faster. This profile shows neither is true so I would not put it into a local.

Answer 2

The one true reason to rewrite your code to

var culture = CultureInfo.CurrentCulture;
String.Format(culture, "{0} some format string", "some args"); 
String.Format(culture, "{0} some format string", "some other args"); 

from

String.Format(CultureInfo.CurrentCulture, "{0} some format string", "some args");  
String.Format(CultureInfo.CurrentCulture, "{0} some format string", "some other args"); 

is for readability and maintainability. Now, if you need for some reason to change the culture from CultureInfo.CurrentCulture to a CultureInfo that is loaded via some configuration file or passed in as a method to the parameter you only need to change the code in one place. Performance is a secondary consideration here and probably does not matter in that this is highly unlikely to be a bottleneck in your code.

Answer 3

There is a bug in your code. In your test code you don't reset the Stopwatch. When you reset the stop watch, you'll see that using the cached reference is actually faster. CultureInfo.CurrentCulture isn't cheap, but string.Format is much more costlier.