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Showing posts from April, 2014

Immutable Sasa.Collections.Tree vs. System.Collections.Dictionary vs. C5 HashDictionary

I've previously posted about Sasa's hash-array mapped trie, but I never posted any benchmarks. I recently came across this post on Stackoverflow which provided a decent basic benchmark between .NET's default Dictionary<TKey, TValue>, the C5 collection's hash dictionary, F#'s immutable map, and .NET's new immutable collections. I slightly modified the file to remove the bench against the F# map and the new immutable collections since I'm still using VS 2010, and I added a simple warmup phase to ensure the methods have all been JIT compiled and the GC run to avoid introducing noise: static void Warmup() { var x = Tree.Make<string, object>(); var y = new C5.HashDictionary<string, object>(); var z = new Dictionary<string, object>(); z.Add("foo", "bar"); for (var i = 0; i < 100; ++i) { x = x.Add("foo" + i, "bar"); y.Add("foo" + i, "bar&q

A Truly Slim Read/Write Lock in C#

It's pretty well known that the CLR's ReaderWriterLock and ReaderWriterLockSlim have unappealing performance characteristics. Each class also encapsulates signficant state, which precludes its use in fine-grained concurrency across large collections of objects. Enter Sasa.Concurrency.RWLock in the core Sasa assembly. This is the most lightweight R/W lock I could come up with, particularly in terms of resources used. It's a struct that encapsulates a simple integer that stores the number of readers and a flag indicating whether a writer is active. The interface is similar to ReaderWriterLockSlim, although there are a few differences which are needed to keep the encapsulated state so small: public struct RWLock { // this field is the only state needed by RWLock private int flags; public void EnterReadLock(); public void ExitReadLock(); public bool TryEnterReadLock(); public void EnterWriteLock(object sync); public bool TryEnterWriteLock(object sync);