| /* |
| * Copyright 2016, Yahoo! Inc. |
| * Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms. |
| */ |
| |
| package com.yahoo.sketches.pig.tuple; |
| |
| import java.io.IOException; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| |
| import com.yahoo.memory.Memory; |
| import com.yahoo.sketches.tuple.ArrayOfDoublesSketch; |
| import com.yahoo.sketches.tuple.ArrayOfDoublesSketchIterator; |
| import com.yahoo.sketches.tuple.ArrayOfDoublesSketches; |
| |
| /** |
| * This UDF converts an ArrayOfDoubles sketch to estimates. |
| * The result will be a tuple with N + 1 double values, where |
| * N is the number of double values kept in the sketch per key. |
| * The first estimate is the estimate of the number of unique |
| * keys in the original population. |
| * Next there are N estimates of the sums of the parameters |
| * in the original population (sums of the values in the sketch |
| * scaled to the original population). |
| */ |
| public class ArrayOfDoublesSketchToEstimates extends EvalFunc<Tuple> { |
| |
| @Override |
| public Tuple exec(final Tuple input) throws IOException { |
| if ((input == null) || (input.size() == 0)) { |
| return null; |
| } |
| |
| final DataByteArray dba = (DataByteArray) input.get(0); |
| final ArrayOfDoublesSketch sketch = ArrayOfDoublesSketches.wrapSketch(Memory.wrap(dba.get())); |
| |
| final double[] estimates = new double[sketch.getNumValues() + 1]; |
| estimates[0] = sketch.getEstimate(); |
| if (sketch.getRetainedEntries() > 0) { // remove unnecessary check when version of sketches-core > 0.4.0 |
| final ArrayOfDoublesSketchIterator it = sketch.iterator(); |
| while (it.next()) { |
| final double[] values = it.getValues(); |
| for (int i = 0; i < sketch.getNumValues(); i++) { |
| estimates[i + 1] += values[i]; |
| } |
| } |
| for (int i = 0; i < sketch.getNumValues(); i++) { |
| estimates[i + 1] /= sketch.getTheta(); |
| } |
| } |
| return Util.doubleArrayToTuple(estimates); |
| } |
| } |