C# puzzle....

James Curran

(I was torn between putting these here or in the C# forum, but it not really a serious question...) Given a simple string

		const string \_str = "abcdefghijklmnopqrstuvwxyz";

put the following equivalent code blocks in order of their speed:

	if ( \_str.Contains("~")) {....}				// A
	if ( \_str.Contains('~')) {....}				// B
	if ( \_str.IndexOf("~") >= 0)   {....}		// C
	if ( \_str.IndexOf('~') >= 0)   {....}		// D
	if ( \_str.IndexOf("~", StringComparison.Ordinal) >= 0)  {....}    //E

Hint: there are three tiers --- One is the clear winning. Two others are about the same, significantly behind, and the last two are about the same, *way* behind the others.

Truth, James

Nish Nishant

I did cheat, and run a quick console app. But D seems fastest, very closely followed by B. Barely really. Then A, and behind A is E. Slowest is C.

Nish Nishant Consultant Software Architect Ganymede Software Solutions LLC www.ganymedesoftwaresolutions.com

Nish Nishant

This is the code I ran in release mode. (.NET Core)

class Program
{
const string _str = "abcdefghijklmnopqrstuvwxyz";

static void Main(string\[\] args)
{
    Foo("A", () => \_str.Contains("~"));
    Foo ("B", () => \_str.Contains('~'));
    Foo("C", () => \_str.IndexOf("~") >= 0);
    Foo("D", () => \_str.IndexOf('~') >= 0);
    Foo("E", () => \_str.IndexOf("~", StringComparison.Ordinal) >= 0);
}

static void Foo(string s, Func<bool> action)
{
    var sw = new Stopwatch();
    sw.Start();
    for (int i = 0; i < 1000000; i++)
    {
        action();
    }
    sw.Stop();
    Console.WriteLine($"{s} - {sw.Elapsed.Milliseconds}");
}

}

Nish Nishant Consultant Software Architect Ganymede Software Solutions LLC www.ganymedesoftwaresolutions.com

Greg Utas

I'm just an old C++ dinosaur, so my guess is that B and D are the fastest, followed by A and C, and finally the indecipherable twaddle of E--unless it's some kind of secret code for "Hint: you're looking for a single character and therefore don't have to construct "~", in which case it's probably faster than A and C but slower than B and D.

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James Curran

Hmmmm Very interesting results. I ran my test using BenchmarkDotNet, with a longer string, with a "~" near the end. Now, the whole point of this was that I found some code using A, and I figured that B should be faster. So, I ran the test-- and in mine, B came out way last. Studying it source code, I found that A just redirects to E, so they were nearly the same. B, however, uses String's IEnumerable interface to run the Enumerable.Contains() extension method, which is why it was last. C I tried, mistakenly thinking it would be the same as E. It came out nearly tied with B for last. D was my overall winner as well. So, it seems you are experiencing a String.Contains(char) which is specific for strings, which I am not seeing. I ran the tests on .NET 4.6.1. Are you using .NET Core?

Truth, James

Nish Nishant

Yep, I used .NET Core which may explain the difference.

Nish Nishant Consultant Software Architect Ganymede Software Solutions LLC www.ganymedesoftwaresolutions.com

Member_14774770

Wrong Forum! Here are few right places to ask the QN or to discuss it. 1.C# Discussion Boards[^] 2.The Weird and The Wonderful[^]

Garth J Lancaster

Upvoted for 'cheating' being scientific - there's nothing wrong with empirical proof, its exactely what I thought when I saw the question, ie, 'why guess' ..

OriginalGriff

Something similar I tried some years ago: Counting Lines in a String[^] It shows another couple of methods you could have tried.

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony AntiTwitter: @DalekDave is now a follower!

Mario Vernari

In my experience, the speed measurements at the start of an app are always polluted by the runtime initialization. That is, it might look that "A" takes longer than "B", where actually does not. Typically, I copy the same piece of code two or three times, then I take the last results. Have a try, maybe the results will change, maybe not.

Jorgen Andersson

No, it's ok. Read the sticky on top: The Lounge[^] Point2: Technical discussions are welcome...

Wrong is evil and must be defeated. - Jeff Ello

OriginalGriff

Greg Utas wrote:

finally the indecipherable twaddle of E--unless it's some kind of secret code for "Hint: you're looking for a single character and therefore don't have to construct "~"

Nope: it's saying "Look for this using a binary comparison, rather than using a culture or shift specific sort order" - basically "compare strings as byte arrays" but using 16 bit values. In theory, this should be much quicker than a non-ordinal comparison as you don't have to deal with "special cases" or "'t' == 'T'", and most processors have machine code instructions for byte based searching and comparing.

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony AntiTwitter: @DalekDave is now a follower!

OriginalGriff

Jorgen is right - this isn't a question seeking help, it's a "Hey! look at this!" discussion.

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony AntiTwitter: @DalekDave is now a follower!

CPallini

After close examination, the fastest option is 'skip that block'. :rolleyes:

Nelek

Mario Vernari wrote:

Typically, I copy the same piece of code two or three times, then I take the last results.

I use sleep 5 seconds, then go for it.

M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpful answers is nice, but saying thanks can be even nicer.

Greg Utas

Next time I can't decipher some twaddle, I'll know who to turn to. :laugh:

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F ES Sitecore

It might well depend on the string being searched and what is being searched.

Jorgen Andersson

Mario Vernari wrote:

In my experience, the speed measurements at the start of an app are always polluted by the runtime initialization.

Not just that, but also caching, task switching etc. There is a really good article here on how to get consistent test results: Performance Tests: Precise Run Time Measurements with System.Diagnostics.Stopwatch[^]

Wrong is evil and must be defeated. - Jeff Ello

Nish Nishant

Thanks, good way of looking at it I suppose.

Nish Nishant Consultant Software Architect Ganymede Software Solutions LLC www.ganymedesoftwaresolutions.com

Nish Nishant

Also one of the more interesting posts here in recent times.

Nish Nishant Consultant Software Architect Ganymede Software Solutions LLC www.ganymedesoftwaresolutions.com