Regular Expression performance [David Gutierrez]

Advanced Regular Expressions in C# | Martijn's C# Programming Blog

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To Compile or Not To Compile

Coding Horror — Fri, 04 Mar 2005 08:33:00 GMT

I am currently in the middle of a way-overdue refactoring of MhtBuilder, which uses regular expressions extensively. I noticed that I had sort of mindlessly added the RegexOptions.Compiled all over the place. It says "compiled" so it must be...

re: Regular Expression performance [David Gutierrez]

David Gutierrez — Wed, 24 Nov 2004 00:54:00 GMT

Lexp, you're right that Whidbey can't unload assemblies. What we've done is switch the compiled on the fly case to use a new form of Reflection.Emit called lightweight code-gen. Rather than generating assemblies, modules, types and methods, with lightweight code-gen you are only allowed to generate methods. In the end you receive a delegate to the generated method, and when that delegate is GC'ed, all of the IL and the JIT'ed code is reclaimed.

Note that the precompiled case can't use lightweight code-gen, so you still can't unload those types.

re: Regular Expression performance [David Gutierrez]

lexp — Wed, 17 Nov 2004 16:52:00 GMT

> In addition. in v1.0 and v1.1, we couldn't ever free the IL we generated, meaning you leaked memory by using this mode. We've fixed that problem in Whidbey.

As far as I know, Whidbey does not support unloading assemblies. Do you create AppDomain for each compiled Regex (and get all cross-appdomain performance drop) or you use some sort of internal mechanism for unloading assemblies?

re: Regular Expression performance [David Gutierrez]

David Gutierrez — Mon, 15 Nov 2004 21:23:00 GMT

We explored doing something like what Doug mentioned as a general purpose mechanism, though it didn't end up happening in Whidbey. I'll enter a feature request to make precompiling easier somehow, though.

re: Regular Expression performance [David Gutierrez]

RichB — Sat, 13 Nov 2004 11:48:00 GMT

The Whidbey C++ project system can manage and link multiple files from multiple languages (eg C++. VB.Net and C# all in the same project). Is it possible to add a .regex filetype into the C++ project system which will also compile and link into a single assembly?

re: Regular Expression performance [David Gutierrez]

Doug McClean — Sat, 13 Nov 2004 08:43:00 GMT

It would be really awesome if the C# compiler or IDE could do that for you, possibly by allowing a special file type and letting Regex.CompileToAssembly() or a more granular method like a hypothetical Regex.CompileToModule() have a crack at it. This approach could be extended to other DSLs too. I wonder if with the new extensible build engine it might not be possible to create such a tool as an add-in. Hmm...