Re: case insensitive string comparison - relative speed - C# Discussion Boards

Re: case insensitive string comparison - relative speed

2-Nov-12 9:31

Suppose two strings,

String S1, S2;

Which is faster:

if( S1.ToLower() == S2.ToLower() )

Or:

if( String.Compare(S1, S2, true) == 0 )

Under what conditions might the relative speed vary?

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

Eddy Vluggen2-Nov-12 9:43

Re: case insensitive string comparison - relative speed

2-Nov-12 9:43

Blake Miller wrote:
Under what conditions might the relative speed vary?

strings are reference-types, and atomic in memory
Converting them both before the comparison is slower than comparing them directly (there can be only one!)
Microsoft "advises" to use uppercase constants. Has something to do with efficiency in comparing.
Does it matter?

The last point is the most important one; readability is important, as it influences maintainability. If you're doing a lot of string-operations, consider a RegEx for the job.

-edit;

Many string operations, most important the Compare and Equals methods, now provide an overload that accepts a StringComparision enumeration value as a parameter.

When you specify either StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase, the string comparison will be non-linguistic. That is, the features that are specific to the natural language are ignored when making comparison decisions. This means the decisions are based on simple byte comparisons and ignore casing or equivalence tables that are parameterized by culture. As a result, by explicitly setting the parameter to either the StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase, your code often gains speed, increases correctness, and becomes more reliable.

It's one of FxCops' warnings[^] Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

if you can't read my code, try converting it here[^]

modified 2-Nov-12 16:25pm.

Blake Miller2-Nov-12 10:26

Re: case insensitive string comparison - relative speed

2-Nov-12 10:26

Thank you for your answers.

Would you have a link to a tech note, language guide or MSDN about this part "Microsoft 'advises' to use uppercase constants."

It does matter. I am looking into this because customers are complaining about CPU load.

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

Eddy Vluggen2-Nov-12 10:29

Re: case insensitive string comparison - relative speed

2-Nov-12 10:29

Modified the post to include the FxCop rule Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]
They hate us for our freedom![^]

SledgeHammer012-Nov-12 11:20

SledgeHammer01

2-Nov-12 11:20

Blake Miller wrote:
It does matter. I am looking into this because customers are complaining about
CPU load.

I think you are barking up the wrong tree if that's the case. As another poster responded, with 1 *MILLION* string comparisons, the difference in performance is non-existant. Your performance issues are likely elsewhere.

Re: case insensitive string comparison - relative speed

Richard Deeming2-Nov-12 9:47

Richard Deeming

2-Nov-12 9:47

The first one creates two new strings, converting each character to lower-case, and then compares the results.

The second one performs a case-insensitive comparison of each character, without allocating any new strings.

Instinct would say that the second will always out-perform the first. Here's some code to test that:

int ITERATIONS = 1000000;

string s1 = "Hello World";
string s2 = "hello world";

Debug.Assert(s1.ToLower() == s2.ToLower());
Debug.Assert(string.Compare(s1, s2, true) == 0);

var sw1 = new Stopwatch();
sw1.Start();
for (int i = 0; i < ITERATIONS; i++)
{
   Debug.Assert(s1.ToLower() == s2.ToLower());
}
sw1.Stop();

var sw2 = new Stopwatch();
sw2.Start();
for (int i = 0; i < ITERATIONS; i++)
{
   Debug.Assert(string.Compare(s1, s2, true) == 0);
}
sw2.Stop();


Console.WriteLine("ToLower: {0}", sw1.Elapsed);
Console.WriteLine("Compare: {0}", sw2.Elapsed);

On my computer, the output is:

ToLower: 00:00:00.4507542
Compare: 00:00:00.1856049

The ToLower approach takes more than twice as long as the Compare approach.

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Re: case insensitive string comparison - relative speed

Blake Miller2-Nov-12 10:28

Re: case insensitive string comparison - relative speed

2-Nov-12 10:28

Confirms my 'gut feeling' and we all know how much we like to depend upon those Smile | :)

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

Clifford Nelson2-Nov-12 10:18

Clifford Nelson

2-Nov-12 10:18

Look at http://msdn.microsoft.com/en-us/library/cc165449.aspx[^]

Re: case insensitive string comparison - relative speed

Blake Miller2-Nov-12 10:28

Re: case insensitive string comparison - relative speed

2-Nov-12 10:28

Awesome! Thanks for the link. Thumbs Up | :thumbsup:

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

jschell2-Nov-12 12:46

jschell

2-Nov-12 12:46

In terms of application performance (rather than just statement performance.)

If you have not measured the application using appropriate data then your first step would be to do that.

If you have measured and found that this specific method containing this statement is the problem then finding a different algorithmic approach would have much more impact. The goal of course in that case is not to find a faster way to do the comparison but instead to find a way so no comparison at all is needed.

Spell checker in code

PozzaVecia2-Nov-12 9:11

2-Nov-12 9:11

What is the fast way to check spell in C# code comment?
I found this
http://visualstudiogallery.msdn.microsoft.com/7c8341f1-ebac-40c8-92c2-476db8d523ce?SRC=Home[^]
But apparently it doesn't work (I installed it but It does nothing)

I post questions to that web address but no one replies

has anyone experience of a working solution?

Eddy Vluggen2-Nov-12 9:38

2-Nov-12 9:38

TheGermoz wrote:

has anyone experience of a working solution?

A few; didn't need one for the last years, but I've implemented Hunspell[^], NetSpell[^] and something called "iSpell", whose link I cannot find.

They worked as advertised.

Bastard Programmer from Hell Suspicious | :suss:

if you can't read my code, try converting it here[^]

PozzaVecia2-Nov-12 9:44

2-Nov-12 9:44

apparently they spell simply a text (I can use word?!), but I need to spell the comment in the code from VS

Eddy Vluggen2-Nov-12 10:11

2-Nov-12 10:11

In that case, you'd need to get familiar with writing a VS-addin; I'd suggest trying to create a prototype for both "problems" (spellcheck a textbox, do something in VS), and working from there.

Bastard Programmer from Hell Suspicious | :suss:

if you can't read my code, try converting it here[^]

PozzaVecia2-Nov-12 11:22

2-Nov-12 11:22

thanks it is a bit complicate, I was looking for a ready to run solution to do not reinvent the wheel.

Eddy Vluggen2-Nov-12 11:31

2-Nov-12 11:31

TheGermoz wrote:
I was looking for a ready to run solution to do not reinvent the wheel

Unless your wheel is better than the one of the competitor, no-one is going to look anyway. Ready-to-run solutions are known paths that are tried and validated.

"Where there's muck, there's money"

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]
They hate us for our freedom![^]

Clifford Nelson2-Nov-12 10:26

Clifford Nelson

2-Nov-12 10:26

I have been using it for a while on several different computers, and always worked for me. Maybe you should add a Q & A (this is a tab on your link). Apparently somebody else if having problems: "It does work on VS 2010 Premium edition?? Im asking because i have it installed on VS 2010 Premium and it doesnt work"

PozzaVecia2-Nov-12 11:22

Source file with repetitive data

2-Nov-12 11:22

http://www.wholetomato.com/products/features/misspelled.asp[^]

this works! but it is not for free....

C-P-User-32-Nov-12 6:02

C-P-User-3

2-Nov-12 6:02

I want to have a bunch of byte arrays.

They are commands which will be sent to the external device; generally across some sort of serial port (for now, at least).

I want to put them in their own file.

This is to keep the source files manageable from a human point of view.

Pretty much, 300 lines has shown itself to be a very useful generally defining limit as one of the things that helps source code make sense.

How do I put them in a file of their own which still allows them to be seen and used by the methods in the other files ?

I'm getting errors like, "The name Such_And_So does not exist in the current context".

My search for the answer lead me to a page on MSDN about "Scopes" (Found ^Here^ )

That page has what appears to be 15 rules on the scope of anything.

I tried reading a couple of those rules. In order to understand the first thing about any one of those rules, you have to already be an expert in C# to begin with (in which case, you wouldn't need the rules in front of you in the first place).

I just want to keep my source files orderly.

How do I let the methods in one file see the data packets in another file ?

The arrays will look something like this...

byte[] Command_Number___1 = new byte[] {
                                        0xFF, 0x01, 0x01, 0x01, 
                                        0x01, 0x01, 0x01, 0x01, 
                                        0x01, 0x01, 0x01 
                                        }
                                        ;

byte[] Command_Number___2 = new byte[]  {
                                        0x0E, 0x02, 0x02, 0x02, 
                                        0x02, 0x02, 0x02, 0x02, 
                                        0x02, 0x02, 0x02, 0x02
                                        }
                                        ;

byte[] Command_Number___3 = new byte[]  {
                                        0xFD, 0x03, 0x03, 0x03, 
                                        0x03, 0x03, 0x03, 0x03, 
                                        0x03, 0x03, 0x03, 0x03
                                        0x03
                                        }
                                        ;

byte[] Command_Number___4 = new byte[]  {
                                        0xFC, 0x04, 0x04, 0x04, 
                                        0x04, 0x04, 0x04, 0x04, 
                                        0x04, 0x04, 0x04, 0x04 
                                        0x04, 0x04
                                        }
                                        ;

byte[] Command_Number___5 = new byte[]  {
                                        0xFB, 0x05, 0x05, 0x05, 
                                        0x05, 0x05, 0x05, 0x05, 
                                        0x05, 0x05, 0x05, 0x05,
                                        0x05, 0x05, 0x05
                                        }
                                        ;

byte[] Command_Number_etc = new byte[]  {
                                        0xFA, 0x0E, 0x0E, 0x0E, 
                                        0x0E, 0x0E, 0x0E, 0x0E, 
                                        0x0E, 0x0E, 0x0E, 0x0E,
                                        0x0E, 0x0E, 0x0E, 0x0E
                                        }
                                        ;

When I put them in a separate file, how do I make them visible to other methods which are in other files ?

It's quite conceivable (indeed normal everyday practice) that this concept will be extended to multiple functions, methods, classes, [whatever you want to call them] and variable names, constants, and who knows what else.

Perhaps the question is: How do I get the compiler and the Linker to cooperate between files ?

Whatever, whatever, thanks for the help.

Richard MacCutchan2-Nov-12 6:29

Richard MacCutchan

2-Nov-12 6:29

Put them in a static class[^] of their own with static getters, and ensure they are part of the namespace of the main application.

One of these days I'm going to think of a really clever signature.

C-P-User-35-Nov-12 8:00

C-P-User-3

5-Nov-12 8:00

Richard MacCutchan wrote:
Put them in a static class of their own with static getters, and ensure they are part of the namespace of the main application.

I'm trying to get an idea of all this.

Tried the following, and the code in other files still can't see the names of these groups of data bytes; no matter if I declare them as public or static...

using System;

namespace The_Same_Namespace_As_The_Other_Files
{
    public partial class Form1 : Form
    {
        public byte[] This_Does_Not_Work = new byte[] { 0x01, 0x02 };
    }



    static class Class1
    {
        static Class1();

        public byte[] The_Command_Set_01 = new byte[] {
                                                0x01, 0x01, 0x01, 0x01, 
                                                0x01, 0x01, 0x01, 0x01, 
                                                0x01, 0x01, 0x01 
                                                }
                                                ;



        static byte[] Just_A_Test_Set = new byte[] {
                                                0xFF, 0xFE, 0xFD, 0xFC, 
                                                0xFB, 0xFA, 0xF9, 0xF8, 
                                                0xF7, 0xF6, 0xF5 
                                                }
                                                ;



	
    }
}

What do I need to do to let my methods in other files see the group called The_Command_Set_01 which is in this file ?

Richard MacCutchan5-Nov-12 22:02

Richard MacCutchan

5-Nov-12 22:02

Your code is not addressing the values in the class. Try this:

public partial class Form1 : Form
{
    MessageBox.Show("Value is: {0}", Class1.Just_A_Test_Set[1]);
}

static class Class1
{
    public static byte[] The_Command_Set_01 = {
                                            0x01, 0x01, 0x01, 0x01,
                                            0x01, 0x01, 0x01, 0x01,
                                            0x01, 0x01, 0x01
                                            };



    public static byte[] Just_A_Test_Set = {
                                            0xFF, 0xFE, 0xFD, 0xFC,
                                            0xFB, 0xFA, 0xF9, 0xF8,
                                            0xF7, 0xF6, 0xF5
                                            };
    }

One of these days I'm going to think of a really clever signature.