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    <p>If you want to be really fast, and I mean really fast you'll have to look beyond the StringBuilder and just write well optimized code.</p> <p>One thing your computer doesn't like to do is branching, if you can write a replace method which operates on a fixed array (char *) and doesn't branch you have great performance.</p> <p>What you'll be doing is that the replace operation is going to search for a sequence of characters and if it finds any such sub string it will replace it. In effect you'll copy the string and when doing so, preform the find and replace.</p> <p>You'll rely on these functions for picking the index of some buffer to read/write. The goal is to preform the replace method such that when nothing has to change you write junk instead of branching.</p> <p>You should be able to complete this without a single if statement and remember to use unsafe code. Otherwise you'll be paying for index checking for every element access.</p> <pre><code>unsafe { fixed( char * p = myStringBuffer ) { // Do fancy string manipulation here } } </code></pre> <p>I've written code like this in C# for fun and seen significant performance improvements, almost 300% speed up for find and replace. While the .NET BCL (base class library) performs quite well it is riddled with branching constructs and exception handling this will slow down you code if you use the built-in stuff. Also these optimizations while perfectly sound are not preformed by the JIT-compiler and you'll have to run the code as a release build without any debugger attached to be able to observe the massive performance gain.</p> <p>I could provide you with more complete code but it is a substantial amount of work. However, I can guarantee you that it will be faster than anything else suggested so far.</p>
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    1. POMemory Efficiency and Performance of String.Replace .NET Framework
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    1. USJohn Leidegren
    1. USJohn Leidegren
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    1. COI am very interested in your suggestion. Could you please share it when you have time?
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      1. USHosam Aly
    2. COString.Replace is optimized with C code already. You cannot beat that.
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      1. USRohit
    3. COIf you look closer at the actual implementation there are things you can do, unfortunately I don't have access to the CLR source. I bet you it's good but not particularly fancy. Find a replace in large strings can be solved faster by implementations based on suffix arrays not sure if there's a tipping point there but even the most trivial linear search algorithms can be made faster by utilizing new hardware and intrinsics that just aren't available in managed code. You can put a lot of effort into it and make it faster but at some point it's hard to defend the time you spend on it.
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