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ASF GitHub Bot commented on FLINK-1745: --------------------------------------- Github user danielblazevski commented on the pull request: https://github.com/apache/flink/pull/1220#issuecomment-146175315 @chiwanpark, in lines 203-207 + val useQuadTree = resultParameters.get(useQuadTreeParam).getOrElse( + training.values.head.size + math.log(math.log(training.values.length)/ + math.log(4.0)) < math.log(training.values.length)/math.log(4.0) && + (metric.isInstanceOf[EuclideanDistanceMetric] || + metric.isInstanceOf[SquaredEuclideanDistanceMetric])) the code decides whether to use quadtree or not if no value is specified. This codes decides based on the number of training + test points + dimension, and is a conservative estimate so that when it uses the quadtree, the quadtree will improve performance compared to the brute-force method -- basically the quadtree scales poorly with dimension, but really well with the number of points. As for using a `Vector` for `minVec` and `maxVec`, I plug in `minVec` and `maxVec` to construct the root Node, and I found it best to use a ListBuffer in the constructor for the Node class when partitioning the boxes into sub-boxes. > Add exact k-nearest-neighbours algorithm to machine learning library > -------------------------------------------------------------------- > > Key: FLINK-1745 > URL: https://issues.apache.org/jira/browse/FLINK-1745 > Project: Flink > Issue Type: New Feature > Components: Machine Learning Library > Reporter: Till Rohrmann > Assignee: Daniel Blazevski > Labels: ML, Starter > > Even though the k-nearest-neighbours (kNN) [1,2] algorithm is quite trivial > it is still used as a mean to classify data and to do regression. This issue > focuses on the implementation of an exact kNN (H-BNLJ, H-BRJ) algorithm as > proposed in [2]. > Could be a starter task. > Resources: > [1] [http://en.wikipedia.org/wiki/K-nearest_neighbors_algorithm] > [2] [https://www.cs.utah.edu/~lifeifei/papers/mrknnj.pdf] -- This message was sent by Atlassian JIRA (v6.3.4#6332)