com.yahoo.sketches.hll.CouponHashMap Maven / Gradle / Ivy
/*
* 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.hll;
import static com.yahoo.sketches.Util.checkIfPowerOf2;
import static com.yahoo.sketches.Util.invPow2;
import java.util.Arrays;
import com.yahoo.sketches.SketchesArgumentException;
import com.yahoo.sketches.hash.MurmurHash3;
/**
* Implements a key-value map where the value is a hash map of coupons.
*
* The outer map is implemented as a prime-sized, Open Address, Double Hash, with deletes, so
* this table can grow and shrink. Each entry row has a 1-byte count where 255 is a marker for
* "dirty" and zero is empty.
*
*
The inner hash tables are implemented with linear probing or OASH and a load factor of 0.75.
*
* @author Lee Rhodes
* @author Alexander Saydakov
* @author Kevin Lang
*/
class CouponHashMap extends Map {
private static final double INNER_LOAD_FACTOR = 0.75;
private static final byte DELETED_KEY_MARKER = (byte) 255;
private static final int BYTE_MASK = 0XFF;
private static final int COUPON_K = 1024;
private static final double RSE = 0.408 / Math.sqrt(1024);
private final int maxCouponsPerKey_;
private final int capacityCouponsPerKey_;
private final int entrySizeBytes_;
private int tableEntries_;
private int capacityEntries_;
private int numActiveKeys_;
private int numDeletedKeys_;
//Arrays
private byte[] keysArr_;
private short[] couponsArr_;
private byte[] curCountsArr_; //also acts as a stateArr: 0 empty, 255 deleted
private float[] invPow2SumArr_;
private float[] hipEstAccumArr_;
private CouponHashMap(final int keySizeBytes, final int maxCouponsPerKey) {
super(keySizeBytes);
maxCouponsPerKey_ = maxCouponsPerKey;
capacityCouponsPerKey_ = (int)(maxCouponsPerKey * INNER_LOAD_FACTOR);
entrySizeBytes_ = keySizeBytes + maxCouponsPerKey * Short.BYTES + 1 + 4 + 4;
}
static CouponHashMap getInstance(final int keySizeBytes, final int maxCouponsPerKey) {
checkMaxCouponsPerKey(maxCouponsPerKey);
final int tableEntries = COUPON_MAP_MIN_NUM_ENTRIES;
final CouponHashMap map = new CouponHashMap(keySizeBytes, maxCouponsPerKey);
map.tableEntries_ = tableEntries;
map.capacityEntries_ = (int)(tableEntries * COUPON_MAP_GROW_TRIGGER_FACTOR);
map.numActiveKeys_ = 0;
map.numDeletedKeys_ = 0;
map.keysArr_ = new byte[tableEntries * keySizeBytes];
map.couponsArr_ = new short[tableEntries * maxCouponsPerKey];
map.curCountsArr_ = new byte[tableEntries];
map.invPow2SumArr_ = new float[tableEntries];
map.hipEstAccumArr_ = new float[tableEntries];
return map;
}
@Override
double update(final byte[] key, final short coupon) {
int entryIndex = findOrInsertKey(key);
return update(entryIndex, coupon); //negative when time to promote
}
@Override
double update(final int entryIndex, final short coupon) {
final int couponMapArrEntryIndex = entryIndex * maxCouponsPerKey_;
int innerCouponIndex = (coupon & 0xFFFF) % maxCouponsPerKey_;
while (couponsArr_[couponMapArrEntryIndex + innerCouponIndex] != 0) {
if (couponsArr_[couponMapArrEntryIndex + innerCouponIndex] == coupon) {
return hipEstAccumArr_[entryIndex]; //duplicate, returns the estimate
}
innerCouponIndex = (innerCouponIndex + 1) % maxCouponsPerKey_; //linear search
}
if (((curCountsArr_[entryIndex] + 1) & BYTE_MASK) > capacityCouponsPerKey_) {
//returns the negative estimate, as signal to promote
return -hipEstAccumArr_[entryIndex];
}
couponsArr_[couponMapArrEntryIndex + innerCouponIndex] = coupon; //insert
curCountsArr_[entryIndex]++;
//hip += k/qt; qt -= 1/2^(val);
hipEstAccumArr_[entryIndex] += COUPON_K / invPow2SumArr_[entryIndex];
invPow2SumArr_[entryIndex] -= invPow2(coupon16Value(coupon));
return hipEstAccumArr_[entryIndex]; //returns the estimate
}
@Override
double getEstimate(final byte[] key) {
final int index = findKey(key);
if (index < 0) { return 0; }
return hipEstAccumArr_[index];
}
@Override
double getUpperBound(byte[] key) {
return getEstimate(key) * (1 + RSE);
}
@Override
double getLowerBound(byte[] key) {
return getEstimate(key) * (1 - RSE);
}
@Override
void updateEstimate(final int entryIndex, final double estimate) {
if (entryIndex < 0) {
throw new SketchesArgumentException("Key not found.");
}
hipEstAccumArr_[entryIndex] = (float) estimate;
}
/**
* Returns entryIndex if the given key is found. If not found, returns one's complement index
* of an empty slot for insertion, which may be over a deleted key.
* @param key the given key
* @return the entryIndex
*/
@Override
int findKey(final byte[] key) {
final long[] hash = MurmurHash3.hash(key, SEED);
int entryIndex = getIndex(hash[0], tableEntries_);
int firstDeletedIndex = -1;
final int loopIndex = entryIndex;
do {
if (curCountsArr_[entryIndex] == 0) {
return firstDeletedIndex == -1 ? ~entryIndex : ~firstDeletedIndex; // found empty or deleted
}
if (curCountsArr_[entryIndex] == DELETED_KEY_MARKER) {
if (firstDeletedIndex == -1) {
firstDeletedIndex = entryIndex;
}
} else if (Map.arraysEqual(keysArr_, entryIndex * keySizeBytes_, key, 0, keySizeBytes_)) {
return entryIndex; // found key
}
entryIndex = (entryIndex + getStride(hash[1], tableEntries_)) % tableEntries_;
} while (entryIndex != loopIndex);
throw new SketchesArgumentException("Key not found and no empty slots!");
}
@Override
int findOrInsertKey(final byte[] key) {
int entryIndex = findKey(key);
if (entryIndex < 0) { //key not found
entryIndex = ~entryIndex;
if (curCountsArr_[entryIndex] == DELETED_KEY_MARKER) { // reusing slot from a deleted key
Arrays.fill(couponsArr_, entryIndex * maxCouponsPerKey_,
(entryIndex + 1) * maxCouponsPerKey_, (short) 0);
curCountsArr_[entryIndex] = 0;
numDeletedKeys_--;
}
if (numActiveKeys_ + numDeletedKeys_ >= capacityEntries_) {
resize();
entryIndex = ~findKey(key);
assert entryIndex >= 0;
}
//insert new key
System.arraycopy(key, 0, keysArr_, entryIndex * keySizeBytes_, keySizeBytes_);
//initialize HIP: qt <- k; hip <- 0;
invPow2SumArr_[entryIndex] = COUPON_K;
hipEstAccumArr_[entryIndex] = 0;
numActiveKeys_++;
}
return entryIndex;
}
@Override
void deleteKey(final int entryIndex) {
curCountsArr_[entryIndex] = DELETED_KEY_MARKER;
numActiveKeys_--;
numDeletedKeys_++;
if (numActiveKeys_ > COUPON_MAP_MIN_NUM_ENTRIES
&& numActiveKeys_ < tableEntries_ * COUPON_MAP_SHRINK_TRIGGER_FACTOR) {
resize();
}
}
@Override
CouponsIterator getCouponsIterator(final int entryIndex) {
return new CouponsIterator(couponsArr_, entryIndex * maxCouponsPerKey_, maxCouponsPerKey_);
}
@Override
double getEntrySizeBytes() {
return entrySizeBytes_;
}
@Override
int getTableEntries() {
return tableEntries_;
}
@Override
int getCapacityEntries() {
return capacityEntries_;
}
@Override
int getCurrentCountEntries() {
return numActiveKeys_ + numDeletedKeys_;
}
@Override
long getMemoryUsageBytes() {
final long arrays = keysArr_.length
+ (long)couponsArr_.length * Short.BYTES
+ curCountsArr_.length
+ invPow2SumArr_.length * Float.BYTES
+ hipEstAccumArr_.length * Float.BYTES;
final long other = 4 * 5;
return arrays + other;
}
@Override
int getActiveEntries() {
return numActiveKeys_;
}
@Override
int getDeletedEntries() {
return numDeletedKeys_;
}
@Override
int getMaxCouponsPerEntry() {
return maxCouponsPerKey_;
}
@Override
int getCapacityCouponsPerEntry() {
return capacityCouponsPerKey_;
}
private static final void checkMaxCouponsPerKey(final int maxCouponsPerKey) {
checkIfPowerOf2(maxCouponsPerKey, "maxCouponsPerKey");
final int cpk = maxCouponsPerKey;
if ((cpk < 16) || (cpk > 256)) {
throw new SketchesArgumentException(
"Required: 16 <= maxCouponsPerKey <= 256 : " + maxCouponsPerKey);
}
}
private void resize() {
final byte[] oldKeysArr = keysArr_;
final short[] oldCouponMapArr = couponsArr_;
final byte[] oldCurCountsArr = curCountsArr_;
final float[] oldInvPow2SumArr = invPow2SumArr_;
final float[] oldHipEstAccumArr = hipEstAccumArr_;
final int oldNumEntries = tableEntries_;
tableEntries_ = Math.max(
nextPrime((int) (numActiveKeys_ / COUPON_MAP_TARGET_FILL_FACTOR)),
COUPON_MAP_MIN_NUM_ENTRIES
);
capacityEntries_ = (int)(tableEntries_ * COUPON_MAP_GROW_TRIGGER_FACTOR);
keysArr_ = new byte[tableEntries_ * keySizeBytes_];
couponsArr_ = new short[tableEntries_ * maxCouponsPerKey_];
curCountsArr_ = new byte[tableEntries_];
invPow2SumArr_ = new float[tableEntries_];
hipEstAccumArr_ = new float[tableEntries_];
numActiveKeys_ = 0;
numDeletedKeys_ = 0;
for (int i = 0; i < oldNumEntries; i++) {
if (oldCurCountsArr[i] != 0 && oldCurCountsArr[i] != DELETED_KEY_MARKER) {
//extract an old valid key
final byte[] key =
Arrays.copyOfRange(oldKeysArr, i * keySizeBytes_, i * keySizeBytes_ + keySizeBytes_);
//insert the key and get its index
final int index = insertKey(key);
//copy the coupons array into that index
System.arraycopy(oldCouponMapArr, i * maxCouponsPerKey_, couponsArr_,
index * maxCouponsPerKey_, maxCouponsPerKey_);
//transfer the count
curCountsArr_[index] = oldCurCountsArr[i];
//transfer the HIP registers
invPow2SumArr_[index] = oldInvPow2SumArr[i];
hipEstAccumArr_[index] = oldHipEstAccumArr[i];
}
}
}
// for internal use by resize, no resize check and no deleted key check here
// no changes to HIP
private int insertKey(final byte[] key) {
final long[] hash = MurmurHash3.hash(key, SEED);
int entryIndex = getIndex(hash[0], tableEntries_);
final int loopIndex = entryIndex;
do {
if (curCountsArr_[entryIndex] == 0) {
System.arraycopy(key, 0, keysArr_, entryIndex * keySizeBytes_, keySizeBytes_);
numActiveKeys_++;
return entryIndex;
}
entryIndex = (entryIndex + getStride(hash[1], tableEntries_)) % tableEntries_;
} while (entryIndex != loopIndex);
throw new SketchesArgumentException("Key not found and no empty slots!");
}
}