com.yahoo.sketches.quantiles.HeapDoublesUnion 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 com.yahoo.memory.Memory;
/**
* Union operation for on-heap.
*
* @author Lee Rhodes
*/
final class HeapDoublesUnion extends DoublesUnion {
private final int k_;
private HeapDoublesSketch gadget_;
HeapDoublesUnion(final int k) {
k_ = k;
}
HeapDoublesUnion(final DoublesSketch sketch) {
k_ = sketch.getK();
gadget_ = (HeapDoublesSketch) sketch;
}
/**
* Heapify the given srcMem into a HeapUnion object.
* @param srcMem the given srcMem.
* A reference to srcMem will not be maintained internally.
*/
HeapDoublesUnion(final Memory srcMem) {
gadget_ = HeapDoublesSketch.heapifyInstance(srcMem);
k_ = gadget_.getK();
}
@Override
public void update(DoublesSketch sketchIn) {
gadget_ = updateLogic(k_, gadget_, (HeapDoublesSketch)sketchIn);
}
@Override
public void update(Memory srcMem) {
HeapDoublesSketch that = HeapDoublesSketch.heapifyInstance(srcMem);
gadget_ = updateLogic(k_, gadget_, that);
}
@Override
public void update(double dataItem) {
if (gadget_ == null) gadget_ = HeapDoublesSketch.newInstance(k_);
gadget_.update(dataItem);
}
@Override
public DoublesSketch getResult() {
if (gadget_ == null) return HeapDoublesSketch.newInstance(k_);
return DoublesUtil.copy(gadget_); //can't have any externally owned handles.
}
@Override
public DoublesSketch getResultAndReset() {
if (gadget_ == null) return null; //Intentionally return null here for speed.
DoublesSketch hqs = gadget_;
gadget_ = null;
return hqs;
}
@Override
public void reset() {
gadget_ = null;
}
@Override
public String toString() {
return toString(true, false);
}
@Override
public String toString(boolean sketchSummary, boolean dataDetail) {
if (gadget_ == null) return HeapDoublesSketch.newInstance(k_).toString();
return gadget_.toString(sketchSummary, dataDetail);
}
//@formatter:off
@SuppressWarnings("null")
static HeapDoublesSketch updateLogic(final int myK, final HeapDoublesSketch myQS,
final HeapDoublesSketch 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; copy or downsample(myK)
case 2: outCase = 2; break; //myQS = null, other = valid; copy or downsample(myK)
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
}
HeapDoublesSketch ret = null;
switch (outCase) {
case 0: ret = null; break;
case 1: ret = myQS; break;
case 2: {
if (myK < other.getK()) {
ret = (HeapDoublesSketch) other.downSample(myK);
} else {
ret = DoublesUtil.copy(other); //required because caller has handle
}
break;
}
case 3: { //must merge
if (myQS.getK() <= other.getK()) { //I am smaller or equal, thus the target
HeapDoublesUnion.mergeInto(other, myQS);
ret = myQS;
} else {
//myQS_K > other_K, must reverse roles
//must copy other as it will become mine and can't have any externally owned handles.
HeapDoublesSketch myNewQS = DoublesUtil.copy(other);
HeapDoublesUnion.mergeInto(myQS, myNewQS);
ret = myNewQS;
}
break;
}
case 4: {
ret = HeapDoublesSketch.newInstance(Math.min(myK, other.getK()));
break;
}
//default: //This cannot happen and cannot be tested
}
return ret;
}
//@formatter:on
/**
* Merges the source sketch into the target sketch that can have a smaller value of K.
* However, it is required that the ratio of the two K values be a power of 2.
* I.e., source.getK() = target.getK() * 2^(nonnegative integer).
* The source is not modified.
*
* Note: It is easy to prove that the following simplified code which launches multiple waves of
* carry propagation does exactly the same amount of merging work (including the work of
* allocating fresh buffers) as the more complicated and seemingly more efficient approach that
* tracks a single carry propagation wave through both sketches.
*
*
This simplified code probably does do slightly more "outer loop" work, but I am pretty
* sure that even that is within a constant factor of the more complicated code, plus the
* total amount of "outer loop" work is at least a factor of K smaller than the total amount of
* merging work, which is identical in the two approaches.
*
*
Note: a two-way merge that doesn't modify either of its two inputs could be implemented
* by making a deep copy of the larger sketch and then merging the smaller one into it.
* However, it was decided not to do this.
*
* @param source The source sketch
* @param target The target sketch
*/
static void mergeInto(DoublesSketch source, DoublesSketch target) {
HeapDoublesSketch src = (HeapDoublesSketch)source;
HeapDoublesSketch tgt = (HeapDoublesSketch)target;
int srcK = src.getK();
int tgtK = tgt.getK();
long srcN = src.getN();
long tgtN = tgt.getN();
if (srcK != tgtK) {
DoublesMergeImpl.downSamplingMergeInto(src, tgt);
return;
}
double[] srcLevels = src.getCombinedBuffer(); // aliasing is a bit dangerous
double[] srcBaseBuffer = srcLevels; // aliasing is a bit dangerous
long nFinal = tgtN + srcN;
for (int i = 0; i < src.getBaseBufferCount(); i++) {
tgt.update(srcBaseBuffer[i]);
}
DoublesUpdateImpl.maybeGrowLevels(nFinal, tgt);
double[] scratchBuf = new double[2 * tgtK];
long srcBitPattern = src.getBitPattern();
assert srcBitPattern == (srcN / (2L * srcK));
for (int srcLvl = 0; srcBitPattern != 0L; srcLvl++, srcBitPattern >>>= 1) {
if ((srcBitPattern & 1L) > 0L) {
DoublesUpdateImpl.inPlacePropagateCarry(
srcLvl,
srcLevels, ((2 + srcLvl) * tgtK),
scratchBuf, 0,
false, tgt); //do Merge-Into-Version
// won't update qsTarget.n_ until the very end
}
}
tgt.n_ = nFinal;
assert tgt.getN() / (2 * tgtK) == tgt.getBitPattern(); // internal consistency check
double srcMax = src.getMaxValue();
double srcMin = src.getMinValue();
double tgtMax = tgt.getMaxValue();
double tgtMin = tgt.getMinValue();
if (srcMax > tgtMax) { tgt.maxValue_ = srcMax; }
if (srcMin < tgtMin) { tgt.minValue_ = srcMin; }
}
}