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POC# Memoization of functions with arbitrary number of arguments
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  1. POC# Memoization of functions with arbitrary number of arguments
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    copied!<p>I'm trying to create a memoization interface for functions with arbitrary number of arguments, but <strike>I'm failing miserably</strike> I feel like my solution is not very flexible. I tried to define an interface for a function which gets memoized automatically upon execution and each function will have to implement this interface. Here is an example with a two parameter Exponential Moving Average function:</p> <pre><code>class EMAFunction:IFunction { Dictionary&lt;List&lt;object&gt;, List&lt;object&gt;&gt; map; class EMAComparer : IEqualityComparer&lt;List&lt;object&gt;&gt; { private int _multiplier = 97; public bool Equals(List&lt;object&gt; a, List&lt;object&gt; b) { List&lt;object&gt; aVals = (List&lt;object&gt;)a[0]; int aPeriod = (int)a[1]; List&lt;object&gt; bVals = (List&lt;object&gt;)b[0]; int bPeriod = (int)b[1]; return (aVals.Count == bVals.Count) &amp;&amp; (aPeriod == bPeriod); } public int GetHashCode(List&lt;object&gt; obj) { // Don't compute hash code on null object. if (obj == null) { return 0; } List&lt;object&gt; vals = (List&lt;object&gt;) obj[0]; int period = (int) obj[1]; return (_multiplier * period.GetHashCode()) + vals.Count; } } public EMAFunction() { NumParams = 2; Name = "EMA"; map = new Dictionary&lt;List&lt;object&gt;, List&lt;object&gt;&gt;(new EMAComparer()); } #region IFunction Members public int NumParams { get; set; } public string Name { get; set; } public object Execute(List&lt;object&gt; parameters) { if (parameters.Count != NumParams) throw new ArgumentException("The num params doesn't match!"); if (!map.ContainsKey(parameters)) { //map.Add(parameters, List&lt;double&gt; values = new List&lt;double&gt;(); List&lt;object&gt; asObj = (List&lt;object&gt;)parameters[0]; foreach (object val in asObj) { values.Add((double)val); } int period = (int)parameters[1]; asObj.Clear(); List&lt;double&gt; ema = TechFunctions.ExponentialMovingAverage(values, period); foreach (double val in ema) { asObj.Add(val); } map.Add(parameters, asObj); } return map[parameters]; } public void ClearMap() { map.Clear(); } #endregion } </code></pre> <p>Here are my tests of the function:</p> <pre><code>private void MemoizeTest() { DataSet dataSet = DataLoader.LoadData(DataLoader.DataSource.FROM_WEB, 1024); List&lt;String&gt; labels = dataSet.DataLabels; Stopwatch sw = new Stopwatch(); IFunction emaFunc = new EMAFunction(); List&lt;object&gt; parameters = new List&lt;object&gt;(); int numRuns = 1000; long sumTicks = 0; parameters.Add(dataSet.GetValues("open")); parameters.Add(12); // First call for(int i = 0; i &lt; numRuns; ++i) { emaFunc.ClearMap();// remove any memoization mappings sw.Start(); emaFunc.Execute(parameters); sw.Stop(); sumTicks += sw.ElapsedTicks; sw.Reset(); } Console.WriteLine("Average ticks not-memoized " + (sumTicks/numRuns)); sumTicks = 0; // Repeat call for (int i = 0; i &lt; numRuns; ++i) { sw.Start(); emaFunc.Execute(parameters); sw.Stop(); sumTicks += sw.ElapsedTicks; sw.Reset(); } Console.WriteLine("Average ticks memoized " + (sumTicks/numRuns)); } </code></pre> <p><strong>Update:</strong><br> Thanks for pointing out my n00bish error... I <strong>always</strong> forget to call Reset on the stopwatch! </p> <p>I've seen <a href="https://stackoverflow.com/questions/633508/two-argument-memoization">another approach to memoization</a> as well... it doesn't offer n-argument memoization, but my approach with the Interface is not much more advantageous since I have to write a class for each function. Is there a reasonable way that I can merge these ideas into something more robust? <b>I want to make it easier to memoize a function without making the user write a class for each function that they intend to use.</b></p>
 

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