src/main/java/org/apache/sysds/runtime/compress/UncompressedBitmap.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.sysds.runtime.compress;

import java.util.Arrays;

import org.apache.commons.lang.ArrayUtils;
import org.apache.sysds.runtime.compress.utils.DblArrayIntListHashMap;
import org.apache.sysds.runtime.compress.utils.DoubleIntListHashMap;
import org.apache.sysds.runtime.compress.utils.DblArrayIntListHashMap.DArrayIListEntry;
import org.apache.sysds.runtime.compress.utils.DoubleIntListHashMap.DIListEntry;
import org.apache.sysds.runtime.compress.utils.IntArrayList;
import org.apache.sysds.runtime.util.SortUtils;

/**
 * Uncompressed representation of one or more columns in bitmap format.
 */
public final class UncompressedBitmap {
	
	private final int _numCols;

	/** Distinct values that appear in the column. Linearized as value groups <v11 v12> <v21 v22>. */
	private double[] _values;

	/** Bitmaps (as lists of offsets) for each of the values. */
	private IntArrayList[] _offsetsLists;

	public UncompressedBitmap(DblArrayIntListHashMap distinctVals, int numColumns) {
		// added for one pass bitmap construction
		// Convert inputs to arrays
		int numVals = distinctVals.size();
		_values = new double[numVals * numColumns];
		_offsetsLists = new IntArrayList[numVals];
		int bitmapIx = 0;
		for(DArrayIListEntry val : distinctVals.extractValues()) {
			System.arraycopy(val.key.getData(), 0, _values, bitmapIx * numColumns, numColumns);
			_offsetsLists[bitmapIx++] = val.value;
		}
		_numCols = numColumns;
	}

	public UncompressedBitmap(DoubleIntListHashMap distinctVals) {
		// added for one pass bitmap construction
		// Convert inputs to arrays
		int numVals = distinctVals.size();
		_values = new double[numVals];
		_offsetsLists = new IntArrayList[numVals];
		int bitmapIx = 0;
		for(DIListEntry val : distinctVals.extractValues()) {
			_values[bitmapIx] = val.key;
			_offsetsLists[bitmapIx++] = val.value;
		}
		_numCols = 1;
	}

	public int getNumColumns() {
		return _numCols;
	}

	/**
	 * Get all values without unnecessary allocations and copies.
	 * 
	 * @return dictionary of value tuples
	 */
	public double[] getValues() {
		return _values;
	}

	/**
	 * Obtain tuple of column values associated with index.
	 * 
	 * @param ix index of a particular distinct value
	 * @return the tuple of column values associated with the specified index
	 */
	public double[] getValues(int ix) {
		return Arrays.copyOfRange(_values, ix * _numCols, (ix + 1) * _numCols);
	}

	/**
	 * Obtain number of distinct values in the column.
	 * 
	 * @return number of distinct values in the column; this number is also the number of bitmaps, since there is one
	 *         bitmap per value
	 */
	public int getNumValues() {
		return _values.length / _numCols;
	}

	public IntArrayList getOffsetsList(int ix) {
		return _offsetsLists[ix];
	}

	public long getNumOffsets() {
		long ret = 0;
		for(IntArrayList offlist : _offsetsLists)
			ret += offlist.size();
		return ret;
	}

	public int getNumOffsets(int ix) {
		return _offsetsLists[ix].size();
	}

	public void sortValuesByFrequency() {
		int numVals = getNumValues();
		int numCols = getNumColumns();

		double[] freq = new double[numVals];
		int[] pos = new int[numVals];

		// populate the temporary arrays
		for(int i = 0; i < numVals; i++) {
			freq[i] = getNumOffsets(i);
			pos[i] = i;
		}

		// sort ascending and reverse (descending)
		SortUtils.sortByValue(0, numVals, freq, pos);
		ArrayUtils.reverse(pos);

		// create new value and offset list arrays
		double[] lvalues = new double[numVals * numCols];
		IntArrayList[] loffsets = new IntArrayList[numVals];
		for(int i = 0; i < numVals; i++) {
			System.arraycopy(_values, pos[i] * numCols, lvalues, i * numCols, numCols);
			loffsets[i] = _offsetsLists[pos[i]];
		}
		_values = lvalues;
		_offsetsLists = loffsets;
	}
}