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POMathNet Numerics out of memory exception
 

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  1. POMathNet Numerics out of memory exception
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    <p>I'm using MathNet.Numerics in my F# project, and it runs out of memory when dealing with matrices that should be well within its remit.</p> <p><strong>EDIT: The problem is definitely not with MathNet.Numerics. It's something I'm doing, though I have yet to work out what that may be.</strong></p> <p>Here is how I'm building the MNIST matrix. Perhaps I'm leaving a file stream open or something, but I can't see how that would be the case.</p> <pre><code>let readInt (b : BinaryReader) = [1..4] |&gt; List.fold (fun res item -&gt; (res &lt;&lt;&lt; 8) ||| (int)(b.ReadByte())) 0 let readImage (b : BinaryReader, rowArray, colArray) = rowArray |&gt; List.collect (fun r -&gt; List.map (fun c -&gt; (b.ReadByte() |&gt; int |&gt; float)/255.0 ) colArray) let loadMnistImage file = use stream = File.Open(file, FileMode.Open) use reader = new BinaryReader(stream) let magicNumber = readInt(reader) let nImages = readInt(reader) let nRows = readInt(reader) let nCols = readInt(reader) let row = [1..nRows] let col = [1..nCols] let images = [1..nImages] |&gt; List.map (fun _ -&gt; readImage(reader, row, col)) matrix images; </code></pre> <p>Using this,</p> <pre><code>let mnistTrainingImages = loadMnistImage MnistTrainingImageData let tr = mnistTrainingImages.Transpose() </code></pre> <p>blows up.</p> <p>Is it them or is it me? I pulled the file from <a href="http://yann.lecun.com/exdb/mnist/" rel="nofollow">http://yann.lecun.com/exdb/mnist/</a>, in case anyone fancies trying this themselves.</p> <p><strong>EDIT 1: The culprit is the call to <code>loadMnistImage</code>.</strong> According to Gene Belitski's suggestion, I ran the code</p> <pre><code>let rand = System.Random() let m: double [,] = Array2D.init 60000 784 (fun _ _ -&gt; rand.NextDouble()) </code></pre> <p>before and after the line </p> <pre><code>let mnistTrainingImages = loadMnistImage MnistTrainingImageData </code></pre> <p>Before the line, it was fine; after the line, it blew up with the same out of memory exception. I would have thought that the <code>use</code> statements would release the file and I'd be OK (and this is not a massive file). However, I'm missing something, so I'll keep digging, and if anyone sees anything please do let me know.</p> <p><strong>EDIT 2: When I simplified the file reader as follows, the problem went away. It looks like the problem was the lazy evaluation of the list.</strong></p> <pre><code>let readImage (b : BinaryReader) = (b.ReadByte() |&gt; int |&gt; float)/255.0 let loadMnistImage file = use stream = File.Open(file, FileMode.Open) use reader = new BinaryReader(stream) let magicNumber = readInt(reader) let nImages = readInt(reader) let nRows = readInt(reader) let nCols = readInt(reader) Array2D.init nImages (nRows * nCols) (fun _ _ -&gt; readImage reader) </code></pre>
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    1. COI think I'm getting hit by lazy list evaluation. I'll switch to arrays and see what happens.
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