Re: StringBuilder Extension: IsQuotedBy

Getting back to my original comment (which applies greatly here) ...

IsQuotedBy needs to be special cased for a single char ... Most of the
time it will be called with only 1 char (think quotes :)) and doing a
simpler ...

return string[0] == char && string[length - 1] == char

will be orders of magnitude faster ...


Cheers,

Greg

On Fri, Feb 15, 2008 at 11:10 AM, Sébastien Lorion
<[email protected]> wrote:
> GC is taking cpu time, being on another thread does not change that.
>  The time spent collecting/compacting is less time spent doing real
>  work. If GC would spend 1 min for each gen0 collection, you would sure
>  see this as part of the cost.
>
>  About your second point, please compare below 2 simple implementations
>  of IsQuotedBy, both maintainable. The first one is around 10x faster.
>  That apparently insignificant change can make the difference between a
>  slow as molasses parser and a speedy one.
>
>  using System;
>  using System.Diagnostics;
>  using System.Text;
>
>  namespace ConsoleApplication1
>  {
>   class Program
>   {
>     static void Main(string[] args)
>     {
>       const int IterationCount = 1000000;
>
>       StringBuilder value = new StringBuilder("@asdf@");
>
>       Stopwatch timer = new Stopwatch();
>
>       timer.Start();
>       for (int i = 0; i < IterationCount; i++)
>       {
>         IsQuotedBy(value, "@");
>       }
>       timer.Stop();
>       Console.WriteLine(timer.ElapsedTicks);
>
>       timer.Start();
>       for (int i = 0; i < IterationCount; i++)
>       {
>         IsQuotedByWithAllocation(value, "@");
>       }
>       timer.Stop();
>       Console.WriteLine(timer.ElapsedTicks);
>
>       Console.ReadKey();
>     }
>
>     static bool IsQuotedBy(StringBuilder input, string quote)
>     {
>       if (input.Length < quote.Length * 2)
>         return false;
>
>       for (int i = 0; i < quote.Length; i++)
>       {
>         if (input[i] != quote[i])
>           return false;
>       }
>
>       for (int i = quote.Length - 1; i >= 0; i--)
>       {
>         if (input[input.Length - i - 1] != quote[i])
>           return false;
>       }
>
>       return true;
>     }
>
>     static bool IsQuotedByWithAllocation(StringBuilder input, string quote)
>     {
>       if (input.Length < quote.Length * 2)
>         return false;
>
>       for (int i = 0; i < quote.Length; i++)
>       {
>         if (input[i] != quote[i])
>           return false;
>       }
>
>       string reverse = Reverse(quote);
>
>       for (int i = 0; i < reverse.Length; i++)
>       {
>         if (input[input.Length - i - 1] != reverse[i])
>           return false;
>       }
>
>       return true;
>     }
>
>     static string Reverse(string input)
>     {
>       StringBuilder reversed = new StringBuilder(input.Length);
>
>       for (int i = input.Length - 1; i >= 0; i--)
>         reversed.Append(input[i]);
>
>       return reversed.ToString();
>
>
>     }
>   }
>  }
>
>
>  On 2/15/08, Peter Obiefuna <[email protected]> wrote:
>  > > Yes, I see that as one action because one cannot go without the other.
>  >  > But sure, StringBuilder has more than one benefits as you and others
>  >  > pointed out.
>  >  >
>  >  > Sébastien
>  >
>  >
>  >
>  > I am struggling with seeing object creation and destruction as "one action"
>  >  ... and then speculate on overall performance based on that 'seeing'. GC
>  >  work is not happening on my worker thread. It may be important in the grand
>  >  scheme but that's how far am willing to go.
>  >  I interpreted the original poster's use of StringBuilder as a 'given'. I
>  >  imagine he's in the middle of this justifiable 'string-building' exercise
>  >  and then comes upon a decision to look for delimiters. Arguing that creating
>  >  StringBuilder for the sake of creating a class would be out of scope and may
>  >  obfuscate the original problem.
>  >
>  >  A perhaps strident note I'd rather chip in here is that programmers who
>  >  target .NET CLR should focus on writing maintainable code as a major
>  >  architectural ideal. For that reason, creating a few more properly
>  >  refactored classes with a single-responsibility concept, in my opinion, is
>  >  of higher value than than shaving off a million nanoseconds from one task.
>  >  Putting this in perspective, these kinds of apps hop around networks quite
>  >  much and there's much to gain from focusing on maintainable code that lays
>  >  more emphasis on optimizing the way it moves around the network.
>  >  P
>  >
>  >  --------------------------------------------------
>  >  From: "Sébastien Lorion" <[email protected]>
>  >  Sent: Friday, February 15, 2008 8:11 AM
>  >
>  > To: <[email protected]>
>  >  Subject: Re: [DOTNET-CLR] StringBuilder Extension: IsQuotedBy
>  >
>  >
>  > > On 2/15/08, Frans Bouma <[email protected]> wrote:
>  >  >>         That initial size is to prevent memory fragmentation during
>  >  >> memcpy
>  >  >>  actions when the buffer needs to be resized. I don't see a relevance
>  >  >> with
>  >  >>  object creation speed and that parameter. I think the main reason the
>  >  >> string
>  >  >>  builder is there is to avoid having lots of objects to collect. I file
>  >  >> that
>  >  >>  kind of action under 'object destruction', not 'creation', though if you
>  >  >> see
>  >  >>  that as one action (as creating an object means it also has to be
>  >  >> collected at
>  >  >>  some point), you have a point.
>  >  >>
>  >  >>                 FB
>  >  >
>  >  > Yes, I see that as one action because one cannot go without the other.
>  >  > But sure, StringBuilder has more than one benefits as you and others
>  >  > pointed out.
>  >  >
>  >  > Sébastien
>  >  >
>  >
>  > > ===================================
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>
>
>  --
>  Sébastien
>  www.sebastienlorion.com
>
>
>
>  ===================================
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