com.yahoo.sketches.quantiles.ItemsUnion Maven / Gradle / Ivy
/*
* Copyright 2015-16, 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.quantiles;
import static com.yahoo.sketches.Util.LS;
import java.util.Comparator;
import com.yahoo.memory.Memory;
import com.yahoo.sketches.ArrayOfItemsSerDe;
/**
* The API for Union operations for generic ItemsSketches
*
* @param type of item
*
* @author Lee Rhodes
* @author Alex Saydakov
*/
public final class ItemsUnion {
protected final int maxK_;
protected final Comparator comparator_;
protected ItemsSketch gadget_;
private ItemsUnion(final int maxK, final Comparator comparator,
final ItemsSketch gadget) {
maxK_ = maxK;
comparator_ = comparator;
gadget_ = gadget;
}
/**
* Create an instance of ItemsUnion with the default k
* @param type of item
* @param comparator to compare items
* @return an instance of ItemsUnion
*/
public static ItemsUnion getInstance(final Comparator comparator) {
return new ItemsUnion(PreambleUtil.DEFAULT_K, comparator, null);
}
/**
* Create an instance of ItemsUnion
* @param type of item
* @param maxK determines the accuracy and size of the union and is a maximum value.
* The effective k can be smaller due to unions with smaller k sketches.
* It is recommended that maxK be a power of 2 to enable unioning of sketches with
* different values of k.
* @param comparator to compare items
* @return an instance of ItemsUnion
*/
public static ItemsUnion getInstance(final int maxK, final Comparator comparator) {
return new ItemsUnion(maxK, comparator, null);
}
/**
* Heapify the given srcMem into a Union object.
* @param type of item
* @param srcMem the given srcMem.
* A reference to srcMem will not be maintained internally.
* @param comparator to compare items
* @param serDe an instance of ArrayOfItemsSerDe
* @return an instance of ItemsUnion
*/
public static ItemsUnion getInstance(final Memory srcMem,
final Comparator comparator, final ArrayOfItemsSerDe serDe) {
final ItemsSketch gadget = ItemsSketch.getInstance(srcMem, comparator, serDe);
return new ItemsUnion(gadget.getK(), gadget.getComparator(), gadget);
}
/**
* Create an instance of ItemsUnion based on ItemsSketch
* @param type of item
* @param sketch the basis of the union
* @return an instance of ItemsUnion
*/
public static ItemsUnion getInstance(final ItemsSketch sketch) {
return new ItemsUnion(sketch.getK(), sketch.getComparator(), ItemsSketch.copy(sketch));
}
/**
* Iterative union operation, which means this method can be repeatedly called.
* Merges the given sketch into this union object.
* The given sketch is not modified.
* It is required that the ratio of the two K values be a power of 2.
* This is easily satisfied if each of the K values is already a power of 2.
* If the given sketch is null or empty it is ignored.
*
* It is required that the results of the union operation, which can be obtained at any time,
* is obtained from {@link #getResult() }.
*
* @param sketchIn the sketch to be merged into this one.
*/
public void update(final ItemsSketch sketchIn) {
gadget_ = updateLogic(maxK_, comparator_, gadget_, sketchIn);
}
/**
* Iterative union operation, which means this method can be repeatedly called.
* Merges the given Memory image of a ItemsSketch into this union object.
* The given Memory object is not modified and a link to it is not retained.
* It is required that the ratio of the two K values be a power of 2.
* This is easily satisfied if each of the K values is already a power of 2.
* If the given sketch is null or empty it is ignored.
*
* It is required that the results of the union operation, which can be obtained at any time,
* is obtained from {@link #getResult() }.
* @param srcMem Memory image of sketch to be merged
* @param serDe an instance of ArrayOfItemsSerDe
*/
public void update(final Memory srcMem, final ArrayOfItemsSerDe serDe) {
final ItemsSketch that = ItemsSketch.getInstance(srcMem, comparator_, serDe);
gadget_ = updateLogic(maxK_, comparator_, gadget_, that);
}
/**
* Update this union with the given double (or float) data Item.
*
* @param dataItem The given datum.
*/
public void update(final T dataItem) {
if (dataItem == null) { return; }
if (gadget_ == null) {
gadget_ = ItemsSketch.getInstance(maxK_, comparator_);
}
gadget_.update(dataItem);
}
/**
* Gets the result of this Union operation as a copy of the internal state.
* This enables further union update operations on this state.
* @return the result of this Union operation
*/
public ItemsSketch getResult() {
if (gadget_ == null) {
return ItemsSketch.getInstance(maxK_, comparator_);
}
return ItemsSketch.copy(gadget_); //can't have any externally owned handles.
}
/**
* Gets the result of this Union operation (without a copy) and resets this Union to the
* virgin state.
*
* @return the result of this Union operation and reset.
*/
public ItemsSketch getResultAndReset() {
if (gadget_ == null) { return null; } //Intentionally return null here for speed.
final ItemsSketch hqs = gadget_;
gadget_ = null;
return hqs;
}
/**
* Resets this Union to a virgin state.
*/
public void reset() {
gadget_ = null;
}
//toByteArray not necessary
/**
* Returns true if this union is empty
* @return true if this union is empty
*/
public boolean isEmpty() {
return (gadget_ == null) ? true : gadget_.isEmpty();
}
/**
* Returns true if this union is direct
* @return true if this union is direct
*/
public boolean isDirect() {
return (gadget_ == null) ? false : gadget_.isDirect();
}
/**
* Returns the configured maxK of this Union.
* @return the configured maxK of this Union.
*/
public int getMaxK() {
return maxK_;
}
/**
* Returns the effective k of this Union.
* @return the effective k of this Union.
*/
public int getEffectiveK() {
return (gadget_ != null) ? gadget_.getK() : maxK_;
}
/**
* Returns summary information about the backing sketch.
*/
@Override
public String toString() {
return toString(true, false);
}
/**
* Returns summary information about the backing sketch. Used for debugging.
* @param sketchSummary if true includes sketch summary
* @param dataDetail if true includes data detail
* @return summary information about the sketch.
*/
public String toString(final boolean sketchSummary, final boolean dataDetail) {
final StringBuilder sb = new StringBuilder();
final String thisSimpleName = this.getClass().getSimpleName();
final int maxK = this.getMaxK();
final String kStr = String.format("%,d", maxK);
sb.append(Util.LS).append("### Quantiles ").append(thisSimpleName).append(LS);
sb.append(" maxK : ").append(kStr);
if (gadget_ == null) {
sb.append(ItemsSketch.getInstance(maxK_, comparator_).toString());
return sb.toString();
}
sb.append(gadget_.toString(sketchSummary, dataDetail));
return sb.toString();
}
//@formatter:off
@SuppressWarnings({"null", "unchecked"})
static ItemsSketch updateLogic(final int myMaxK, final Comparator comparator,
final ItemsSketch myQS, final ItemsSketch other) {
int sw1 = ((myQS == null) ? 0 : myQS.isEmpty() ? 4 : 8);
sw1 |= ((other == null) ? 0 : other.isEmpty() ? 1 : 2);
int outCase = 0; //0=null, 1=NOOP, 2=copy, 3=merge
switch (sw1) {
case 0: outCase = 0; break; //myQS = null, other = null ; return null
case 1: outCase = 4; break; //myQS = null, other = empty; create empty-heap(myMaxK)
case 2: outCase = 2; break; //myQS = null, other = valid; stream or downsample to myMaxK
case 4: outCase = 1; break; //myQS = empty, other = null ; no-op
case 5: outCase = 1; break; //myQS = empty, other = empty; no-op
case 6: outCase = 3; break; //myQS = empty, other = valid; merge
case 8: outCase = 1; break; //myQS = valid, other = null ; no-op
case 9: outCase = 1; break; //myQS = valid, other = empty: no-op
case 10: outCase = 3; break; //myQS = valid, other = valid; merge
//default: //This cannot happen and cannot be tested
}
ItemsSketch ret = null;
switch (outCase) {
case 0: ret = null; break;
case 1: ret = myQS; break;
case 2: { //myQS = null, other = valid; stream or downsample to myMaxK
if (!other.isEstimationMode()) { //other is exact, stream items in
ret = ItemsSketch.getInstance(myMaxK, comparator);
final int otherCnt = other.getBaseBufferCount();
final Object[] combBuf = other.getCombinedBuffer();
for (int i = 0; i < otherCnt; i++) {
ret.update((T) combBuf[i]);
}
}
else { //myQS = null, other is est mode
ret = (myMaxK < other.getK())
? other.downSample(myMaxK)
: ItemsSketch.copy(other); //required because caller has handle
}
break;
}
case 3: { //myQS = empty/valid, other = valid; merge
if (!other.isEstimationMode()) { //other is exact, stream items in
ret = myQS;
final int otherCnt = other.getBaseBufferCount();
final Object[] combBuf = other.getCombinedBuffer();
for (int i = 0; i < otherCnt; i++) {
ret.update((T) combBuf[i]);
}
}
else { //myQS = empty/valid, other = valid and in est mode
if (myQS.getK() <= other.getK()) { //I am smaller or equal, thus the target
ItemsMergeImpl.mergeInto(other, myQS);
ret = myQS;
}
else { //Bigger: myQS.getK() > other.getK(), must reverse roles
//must copy other as it will become mine and can't have any externally owned handles.
ret = ItemsSketch.copy(other);
ItemsMergeImpl.mergeInto(myQS, ret);
}
}
break;
}
case 4: {
ret = ItemsSketch.getInstance(Math.min(myMaxK, other.getK()), comparator);
break;
}
//default: //This cannot happen and cannot be tested
}
return ret;
}
//@formatter:on
}
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