Testing and Validation CNTK Models using C#

Bahrudin Hrnjica

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15 Nov 2017CPOL1 min read

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Once the model is built and Loss and Validation functions satisfy our expectation, we need to validate and test the model using the data which was not part of the training data set (unseen data).

…continuation from the previous post.

Once the model is built and Loss and Validation functions satisfy our expectation, we need to validate and test the model using the data which was not part of the training data set (unseen data). The model validation is very important because we want to see if our model is trained well, so that can evaluate unseen data approximately same as the training data. Otherwise, the model which cannot predict the output is called overfitted model. Overfitting can happen when the model was trained long enough that shows very high performance for the training data set, but for the testing data, evaluate bad results.

We will continue with the implementation from the prevision two posts, and implement model validation. After the model is trained, the model and the trainer are passed to the Evaluation method. The evaluation method loads the testing data and calculates the output using passed model. Then it compares calculated (predicted) values with the output from the testing data set and calculated the accuracy. The following source code shows the evaluation implementation.

private static void EvaluateIrisModel(Function ffnn_model, Trainer trainer, DeviceDescriptor device)
{
    var dataFolder = "Data";//files must be on the same folder as program
    var trainPath = Path.Combine(dataFolder, "testIris_cntk.txt");
    var featureStreamName = "features";
    var labelsStreamName = "label";

    //extract features and label from the model
    var feature = ffnn_model.Arguments[0];
    var label = ffnn_model.Output;

    //stream configuration to distinct features and labels in the file
    var streamConfig = new StreamConfiguration[]
        {
            new StreamConfiguration(featureStreamName, feature.Shape[0]),
            new StreamConfiguration(labelsStreamName, label.Shape[0])
        };

    // prepare testing data
    var testMinibatchSource = MinibatchSource.TextFormatMinibatchSource(
        trainPath, streamConfig, MinibatchSource.InfinitelyRepeat, true);
    var featureStreamInfo = testMinibatchSource.StreamInfo(featureStreamName);
    var labelStreamInfo = testMinibatchSource.StreamInfo(labelsStreamName);

    int batchSize = 20;
    int miscountTotal = 0, totalCount = 20;
    while (true)
    {
        var minibatchData = testMinibatchSource.GetNextMinibatch((uint)batchSize, device);
        if (minibatchData == null || minibatchData.Count == 0)
            break;
        totalCount += (int)minibatchData[featureStreamInfo].numberOfSamples;

        // expected labels are in the mini batch data.
        var labelData = minibatchData[labelStreamInfo].data.GetDenseData<float>(label);
        var expectedLabels = labelData.Select(l => l.IndexOf(l.Max())).ToList();

        var inputDataMap = new Dictionary<Variable, Value>() {
            { feature, minibatchData[featureStreamInfo].data }
        };

        var outputDataMap = new Dictionary<Variable, Value>() {
            { label, null }
        };

        ffnn_model.Evaluate(inputDataMap, outputDataMap, device);
        var outputData = outputDataMap[label].GetDenseData<float>(label);
        var actualLabels = outputData.Select(l => l.IndexOf(l.Max())).ToList();

        int misMatches = actualLabels.Zip(expectedLabels, (a, b) => a.Equals(b) ? 0 : 1).Sum();

        miscountTotal += misMatches;
        Console.WriteLine($"Validating Model: Total Samples = {totalCount}, 
                                              Mis-classify Count = {miscountTotal}");

        if (totalCount >= 20)
            break;
    }
    Console.WriteLine($"---------------");
    Console.WriteLine($"------TESTING SUMMARY--------");
    float accuracy = (1.0F - miscountTotal / totalCount);
    Console.WriteLine($"Model Accuracy = {accuracy}");
    return;
}

The implemented method is called in the previous Training method.

EvaluateIrisModel(ffnn_model, trainer, device);

As can be seen, the model validation has shown that the model predicts the data with high accuracy, which is shown in the following image:

This is the latest post in the series of blog posts about using Feed forward neural networks to train the Iris data using CNTK and C#.

The full source code for all three samples can be found here.

Filed under: .NET, C#, CNTK, CodeProject
Tagged: .NET, C#, CNTK, Code Project, CodeProject, Machine Learning

This article was originally posted at https://bhrnjica.net/2017/11/15/testing-and-validation-cntk-models-using-c

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Bahrudin Hrnjica

Software Developer (Senior)

Bosnia and Herzegovina

Bahrudin Hrnjica holds a Ph.D. degree in Technical Science/Engineering from University in Bihać.
Besides teaching at University, he is in the software industry for more than two decades, focusing on development technologies e.g. .NET, Visual Studio, Desktop/Web/Cloud solutions.

He works on the development and application of different ML algorithms. In the development of ML-oriented solutions and modeling, he has more than 10 years of experience. His field of interest is also the development of predictive models with the ML.NET and Keras, but also actively develop two ML-based .NET open source projects: GPdotNET-genetic programming tool and ANNdotNET - deep learning tool on .NET platform. He works in multidisciplinary teams with the mission of optimizing and selecting the ML algorithms to build ML models.

He is the author of several books, and many online articles, writes a blog at http://bhrnjica.net, regularly holds lectures at local and regional conferences, User groups and Code Camp gatherings, and is also the founder of the Bihac Developer Meetup Group. Microsoft recognizes his work and awarded him with the prestigious Microsoft MVP title for the first time in 2011, which he still holds today.

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Testing and Validation CNTK Models using C#

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