Function distance

examples/machine_learning/knn.cpp:26–49

Calculate all the distances from testing set to training set

// Calculate all the distances from testing set to training set
array distance(array train, array test) {
    const int feat_len  = train.dims(1);
    const int num_train = train.dims(0);
    const int num_test  = test.dims(0);

    array dist = constant(0, num_train, num_test);

    // Iterate over each attribute
    for (int ii = 0; ii < feat_len; ii++) {
        // Get a attribute vectors
        array train_i = train(span, ii);
        array test_i  = test(span, ii).T();

        // Tile the vectors to generate matrices
        array train_tiled = tile(train_i, 1, num_test);
        array test_tiled  = tile(test_i, num_train, 1);

        // Add the distance for this attribute
        dist = dist + abs(train_tiled - test_tiled);
        dist.eval();  // Necessary to free up train_i, test_i
    }

    return dist;
}

array knn(array &train_feats, array &test_feats, array &train_labels) {
    // Find distances between training and testing sets