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Core sketch algorithms used alone and by other Java repositories in the DataSketches library.
/*
* 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.datasketches.theta;
import static java.nio.charset.StandardCharsets.UTF_8;
import static org.apache.datasketches.Util.DEFAULT_UPDATE_SEED;
import static org.apache.datasketches.Util.checkSeedHashes;
import static org.apache.datasketches.Util.computeSeedHash;
import static org.apache.datasketches.hash.MurmurHash3.hash;
import static org.apache.datasketches.theta.PreambleUtil.MAX_THETA_LONG_AS_DOUBLE;
import static org.apache.datasketches.theta.PreambleUtil.SINGLEITEM_FLAG_MASK;
import org.apache.datasketches.SketchesArgumentException;
import org.apache.datasketches.Util;
import org.apache.datasketches.memory.Memory;
/**
* @author Lee Rhodes
*/
public final class SingleItemSketch extends CompactSketch {
private static final long DEFAULT_SEED_HASH = computeSeedHash(DEFAULT_UPDATE_SEED) & 0xFFFFL;
private static final String LS = System.getProperty("line.separator");
//For backward compatibility, a candidate pre0 long must have Flags= compact, read-only, ordered,
// empty=0; COMPACT-Family=3, SerVer=3, PreLongs=1, plus the relevant seedHash.
private static final long PRE0_LO6 = 0X00_00_1A_00_00_03_03_01L; //no SI flag, requires not empty
private static final long PRE0_MASK = 0XFF_FF_DF_FF_FF_FF_FF_FFL; //removes SI flag
private final long[] arr = new long[2];
//use to test a candidate pre0 given a seed
static boolean testPre0Seed(final long candidate, final long seed) {
final long seedHash = computeSeedHash(seed) & 0xFFFFL;
return testPre0SeedHash(candidate, seedHash);
}
//use to test a candidate pre0 given a seedHash
static boolean testPre0SeedHash(final long candidate, final long seedHash) {
final long test1 = (seedHash << 48) | PRE0_LO6; //no SI bit
final long test2 = test1 | ((long)SINGLEITEM_FLAG_MASK << 40); //adds the SI bit
final long mask = PRE0_MASK; //ignores the SI flag
final long masked = candidate & mask;
return (masked == test1) || (candidate == test2);
}
//Internal Constructor. All checking has been done, assumes default seed
private SingleItemSketch(final long hash) {
arr[0] = (DEFAULT_SEED_HASH << 48) | PRE0_LO6 | ((long)SINGLEITEM_FLAG_MASK << 40);
arr[1] = hash;
}
//Internal Constructor.All checking has been done, give the relevant seed
SingleItemSketch(final long hash, final long seed) {
final long seedHash = computeSeedHash(seed) & 0xFFFFL;
arr[0] = (seedHash << 48) | PRE0_LO6 | ((long)SINGLEITEM_FLAG_MASK << 40);
arr[1] = hash;
}
//All checking has been done, give the relevant seed
SingleItemSketch(final long hash, final short seedHash) {
final long seedH = seedHash & 0xFFFFL;
arr[0] = (seedH << 48) | PRE0_LO6 | ((long)SINGLEITEM_FLAG_MASK << 40);
arr[1] = hash;
}
/**
* Creates a SingleItemSketch on the heap given a SingleItemSketch Memory image and assumes the
* DEFAULT_UPDATE_SEED.
* @param srcMem the Memory to be heapified. It must be a least 16 bytes.
* @return a SingleItemSketch
*/
public static SingleItemSketch heapify(final Memory srcMem) {
return heapify(srcMem, Util.DEFAULT_UPDATE_SEED);
}
/**
* Creates a SingleItemSketch on the heap given a SingleItemSketch Memory image and a seed.
* Checks the seed hash of the given Memory against a hash of the given seed.
* @param srcMem the Memory to be heapified
* @param seed a given hash seed
* @return a SingleItemSketch
*/
public static SingleItemSketch heapify(final Memory srcMem, final long seed) {
final long memPre0 = srcMem.getLong(0);
final short seedHashMem = srcMem.getShort(6);
final short seedHashCk = computeSeedHash(seed);
checkSeedHashes(seedHashMem, seedHashCk);
if (testPre0SeedHash(memPre0, seedHashCk)) {
return new SingleItemSketch(srcMem.getLong(8), seedHashCk);
}
final long def = (((long)seedHashCk << 48) | PRE0_LO6);
throw new SketchesArgumentException("Input Memory does not match required Preamble. " + LS
+ "Memory Pre0 : " + Long.toHexString(memPre0) + LS
+ "Should be Pre0 : " + Long.toHexString(def));
}
//Create methods using the default seed
/**
* Create this sketch with a long.
*
* @param datum The given long datum.
* @return a SingleItemSketch
*/
public static SingleItemSketch create(final long datum) {
final long[] data = { datum };
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given double (or float) datum.
* The double will be converted to a long using Double.doubleToLongBits(datum),
* which normalizes all NaN values to a single NaN representation.
* Plus and minus zero will be normalized to plus zero.
* The special floating-point values NaN and +/- Infinity are treated as distinct.
*
* @param datum The given double datum.
* @return a SingleItemSketch
*/
public static SingleItemSketch create(final double datum) {
final double d = (datum == 0.0) ? 0.0 : datum; // canonicalize -0.0, 0.0
final long[] data = { Double.doubleToLongBits(d) };// canonicalize all NaN forms
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given String.
* The string is converted to a byte array using UTF8 encoding.
* If the string is null or empty no create attempt is made and the method returns null.
*
* Note: this will not produce the same hash values as the {@link #create(char[])}
* method and will generally be a little slower depending on the complexity of the UTF8 encoding.
*
*
* @param datum The given String.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final String datum) {
if ((datum == null) || datum.isEmpty()) { return null; }
final byte[] data = datum.getBytes(UTF_8);
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given byte array.
* If the byte array is null or empty no create attempt is made and the method returns null.
*
* @param data The given byte array.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final byte[] data) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given char array.
* If the char array is null or empty no create attempt is made and the method returns null.
*
* Note: this will not produce the same output hash values as the {@link #create(String)}
* method but will be a little faster as it avoids the complexity of the UTF8 encoding.
*
* @param data The given char array.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final char[] data) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given integer array.
* If the integer array is null or empty no create attempt is made and the method returns null.
*
* @param data The given int array.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final int[] data) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
/**
* Create this sketch with the given long array.
* If the long array is null or empty no create attempt is made and the method returns null.
*
* @param data The given long array.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final long[] data) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, DEFAULT_UPDATE_SEED)[0] >>> 1);
}
//Updates with a user specified seed
/**
* Create this sketch with a long and a seed.
*
* @param datum The given long datum.
* @param seed used to hash the given value.
* @return a SingleItemSketch
*/
public static SingleItemSketch create(final long datum, final long seed) {
final long[] data = { datum };
return new SingleItemSketch(hash(data, seed)[0] >>> 1);
}
/**
* Create this sketch with the given double (or float) datum and a seed.
* The double will be converted to a long using Double.doubleToLongBits(datum),
* which normalizes all NaN values to a single NaN representation.
* Plus and minus zero will be normalized to plus zero.
* The special floating-point values NaN and +/- Infinity are treated as distinct.
*
* @param datum The given double datum.
* @param seed used to hash the given value.
* @return a SingleItemSketch
*/
public static SingleItemSketch create(final double datum, final long seed) {
final double d = (datum == 0.0) ? 0.0 : datum; // canonicalize -0.0, 0.0
final long[] data = { Double.doubleToLongBits(d) };// canonicalize all NaN forms
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
/**
* Create this sketch with the given String and a seed.
* The string is converted to a byte array using UTF8 encoding.
* If the string is null or empty no create attempt is made and the method returns null.
*
* Note: this will not produce the same output hash values as the {@link #create(char[])}
* method and will generally be a little slower depending on the complexity of the UTF8 encoding.
*
*
* @param datum The given String.
* @param seed used to hash the given value.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final String datum, final long seed) {
if ((datum == null) || datum.isEmpty()) { return null; }
final byte[] data = datum.getBytes(UTF_8);
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
/**
* Create this sketch with the given byte array and a seed.
* If the byte array is null or empty no create attempt is made and the method returns null.
*
* @param data The given byte array.
* @param seed used to hash the given value.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final byte[] data, final long seed) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
/**
* Create this sketch with the given char array and a seed.
* If the char array is null or empty no create attempt is made and the method returns null.
*
* Note: this will not produce the same output hash values as the {@link #create(String)}
* method but will be a little faster as it avoids the complexity of the UTF8 encoding.
*
* @param data The given char array.
* @param seed used to hash the given value.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final char[] data, final long seed) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
/**
* Create this sketch with the given integer array and a seed.
* If the integer array is null or empty no create attempt is made and the method returns null.
*
* @param data The given int array.
* @param seed used to hash the given value.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final int[] data, final long seed) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
/**
* Create this sketch with the given long array and a seed.
* If the long array is null or empty no create attempt is made and the method returns null.
*
* @param data The given long array.
* @param seed used to hash the given value.
* @return a SingleItemSketch or null
*/
public static SingleItemSketch create(final long[] data, final long seed) {
if ((data == null) || (data.length == 0)) { return null; }
return new SingleItemSketch(hash(data, seed)[0] >>> 1, seed);
}
//Sketch
@Override
public int getCountLessThanTheta(final double theta) {
return (arr[1] < (theta * MAX_THETA_LONG_AS_DOUBLE)) ? 1 : 0;
}
@Override
public int getCurrentBytes(final boolean compact) {
return 16;
}
@Override
public double getEstimate() {
return 1.0;
}
@Override
public HashIterator iterator() {
return new HeapHashIterator(new long[] { arr[1] }, 1, Long.MAX_VALUE);
}
@Override
public double getLowerBound(final int numStdDev) {
return 1.0;
}
@Override
public int getRetainedEntries(final boolean valid) {
return 1;
}
@Override
public long getThetaLong() {
return Long.MAX_VALUE;
}
@Override
public double getUpperBound(final int numStdDev) {
return 1.0;
}
@Override
public boolean hasMemory() {
return false;
}
@Override
public boolean isDirect() {
return false;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public boolean isOrdered() {
return true;
}
@Override
public byte[] toByteArray() {
final byte[] out = new byte[16];
for (int i = 0; i < 8; i++) {
out[i] = (byte) (arr[0] >>> (i * 8));
out[i + 8] = (byte) (arr[1] >>> (i * 8));
}
return out;
}
//restricted methods
@Override
long[] getCache() {
return new long[] { arr[1] };
}
@Override
int getCurrentPreambleLongs(final boolean compact) {
return 1;
}
@Override
Memory getMemory() {
return null;
}
@Override
short getSeedHash() {
return (short) (arr[0] >>> 48);
}
}
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