com.metamx.druid.aggregation.Histogram.java Source code

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Here is the source code for com.metamx.druid.aggregation.Histogram.java

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/*
 * Druid - a distributed column store.
 * Copyright (C) 2012  Metamarkets Group Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package com.metamx.druid.aggregation;

import com.fasterxml.jackson.annotation.JsonValue;
import com.google.common.base.Preconditions;
import com.google.common.primitives.Floats;
import com.google.common.primitives.Ints;
import com.google.common.primitives.Longs;

import java.nio.ByteBuffer;
import java.util.Arrays;

public class Histogram {
    public float[] breaks;
    public long[] bins;
    public transient long count;
    public float min;
    public float max;

    public Histogram(float[] breaks) {
        Preconditions.checkArgument(breaks != null, "Histogram breaks must not be null");

        this.breaks = breaks;
        this.bins = new long[this.breaks.length + 1];
        this.count = 0;
        this.min = Float.MAX_VALUE;
        this.max = Float.MIN_VALUE;
    }

    public Histogram(float[] breaks, long[] bins, float min, float max) {
        this.breaks = breaks;
        this.bins = bins;
        this.min = min;
        this.max = max;
        for (long k : bins)
            this.count += k;
    }

    public void offer(float d) {
        if (d > max)
            max = d;
        if (d < min)
            min = d;

        int index = Arrays.binarySearch(breaks, d);
        int pos = (index >= 0) ? index : -(index + 1);
        bins[pos]++;
        count++;
    }

    public Histogram fold(Histogram h) {
        Preconditions.checkArgument(Arrays.equals(breaks, h.breaks),
                "Cannot fold histograms with different breaks");

        if (h.min < min)
            min = h.min;
        if (h.max > max)
            max = h.max;

        count += h.count;
        for (int i = 0; i < bins.length; ++i) {
            bins[i] += h.bins[i];
        }
        return this;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        Histogram histogram = (Histogram) o;

        if (count != histogram.count) {
            return false;
        }
        if (Float.compare(histogram.max, max) != 0) {
            return false;
        }
        if (Float.compare(histogram.min, min) != 0) {
            return false;
        }
        if (!Arrays.equals(bins, histogram.bins)) {
            return false;
        }
        if (!Arrays.equals(breaks, histogram.breaks)) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int result = Arrays.hashCode(breaks);
        result = 31 * result + Arrays.hashCode(bins);
        result = 31 * result + (min != +0.0f ? Float.floatToIntBits(min) : 0);
        result = 31 * result + (max != +0.0f ? Float.floatToIntBits(max) : 0);
        return result;
    }

    @JsonValue
    public byte[] toBytes() {
        ByteBuffer buf = ByteBuffer
                .allocate(Ints.BYTES + Floats.BYTES * breaks.length + Longs.BYTES * bins.length + Floats.BYTES * 2);

        buf.putInt(breaks.length);
        for (float b : breaks)
            buf.putFloat(b);
        for (long c : bins)
            buf.putLong(c);
        buf.putFloat(min);
        buf.putFloat(max);

        return buf.array();
    }

    /**
     * Returns a visual representation of a histogram object.
     * Initially returns an array of just the min. and max. values
     * but can also support the addition of quantiles.
     */
    public HistogramVisual asVisual() {
        float[] visualCounts = new float[bins.length - 2];
        for (int i = 0; i < visualCounts.length; ++i)
            visualCounts[i] = (float) bins[i + 1];
        return new HistogramVisual(breaks, visualCounts, new float[] { min, max });
    }

    public static Histogram fromBytes(byte[] bytes) {
        ByteBuffer buf = ByteBuffer.wrap(bytes);
        return fromBytes(buf);
    }

    public static Histogram fromBytes(ByteBuffer buf) {
        int n = buf.getInt();
        float[] breaks = new float[n];
        long[] bins = new long[n + 1];

        for (int i = 0; i < breaks.length; ++i)
            breaks[i] = buf.getFloat();
        for (int i = 0; i < bins.length; ++i)
            bins[i] = buf.getLong();

        float min = buf.getFloat();
        float max = buf.getFloat();

        return new Histogram(breaks, bins, min, max);
    }

    @Override
    public String toString() {
        return "Histogram{" + "bins=" + Arrays.toString(bins) + ", count=" + count + ", breaks="
                + Arrays.toString(breaks) + '}';
    }
}