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POThe cost of casting?
 

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  1. POThe cost of casting?
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    <p>I have a key/value pairs mapped by hash (ID) in <code>Dictionary&lt;string, Dictionary&lt;string, string&gt;&gt;</code> called id2key_value. You can think of this as a way to represent database-like table with rows.</p> <p>I added some helper functions to ease the use of some basic datatypes by doing a cast, like</p> <pre><code>public int GetInt(string id, string key) { int value = 0; bool success = int.TryParse(map[id][key], out value); if (success) return value; else throw new InvalidOperationException( "Trying to obtain a non-integer value with GetInt()."); } </code></pre> <p>Well, I thought I was being clever when I came up with an idea of a "cast-cache", which basically holds already parsed objects, so I could skip the parsing of the string for int, bool, DateTime, etc., and simply cast them to appropriate datatype from the cache. Like,</p> <pre><code>public int GetInt(string id, string key) { if (cast_cache.ContainsKey(id) &amp;&amp; cast_cache[id].ContainsKey(key)) return (int) cast_cache[id][key]; int value = 0; bool success = int.TryParse(map[id][key], out value); if (success) { this.AddToCache(id, key, value); return value; } else throw new InvalidOperationException( "Trying to obtain a non-integer value with GetInt()."); } </code></pre> <p>The "cast-cache" is simply <code>Dictionary&lt;string, Dictionary&lt;string, object&gt;&gt;</code>.</p> <p>So, I did some performance testing with 10000 ints added to the map. Then I did one million random retrieves, with and without "cast-caching".</p> <p>It took 495(ms) without caching and 490(ms) with caching. I also ran a test with DateTime, there the difference was more significant, but less than I expect (~750(ms) non-cached vs ~500(ms) cached).</p> <p>Not (obviously) understanding the principle of a cast, how costly this operation is and why the performance is so close to the one that "deserializes" from string?</p>
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    1. USSean Bright
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      1. VTUpMod
    1. COCan't you use Generics?
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      1. USDykam
    2. CO@Dykam, How? The id2key_value can contain any types, deserialized as strings to be able to persistantly store to an implemented provider (file, database, etc.). Where do you vision to use generics?
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    3. COParsing is not casting...
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      1. USThomas Levesque
 

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