Copy changes from kll doubles to floats items

src/main/java/org/apache/datasketches/kll/KllFloatsHelper.java

@@ -123,16 +123,15 @@ private static void compressWhileUpdatingSketch(final KllFloatsSketch fltSk) {
   }
 
   //assumes readOnly = false and UPDATABLE, called from KllFloatsSketch::merge
-  static void mergeFloatImpl(final KllFloatsSketch mySketch,
-      final KllFloatsSketch otherFltSk) {
+  static void mergeFloatImpl(final KllFloatsSketch mySketch, final KllFloatsSketch otherFltSk) {
     if (otherFltSk.isEmpty()) { return; }
 
     //capture my key mutable fields before doing any merging
     final boolean myEmpty = mySketch.isEmpty();
     final float myMin = myEmpty ? Float.NaN : mySketch.getMinItem();
     final float myMax = myEmpty ? Float.NaN : mySketch.getMaxItem();
     final int myMinK = mySketch.getMinK();
-    final long finalN = mySketch.getN() + otherFltSk.getN();
+    final long finalN = Math.addExact(mySketch.getN(), otherFltSk.getN());
 
     //buffers that are referenced multiple times
     final int otherNumLevels = otherFltSk.getNumLevels();
@@ -398,7 +397,7 @@ private static int[] generalFloatsCompress(
       curLevel++; // start out at level 0
 
       // If we are at the current top level, add an empty level above it for convenience,
-      // but do not increment numLevels until later
+      // but do not actually increment numLevels until later
       if (curLevel == (numLevels - 1)) {
         inLevels[curLevel + 2] = inLevels[curLevel + 1];
       }
@@ -465,7 +464,7 @@ private static int[] generalFloatsCompress(
     return new int[] {numLevels, targetItemCount, currentItemCount};
   }
 
-  private static void populateFloatWorkArrays(
+  private static void populateFloatWorkArrays( //workBuf and workLevels are modified
       final float[] workbuf, final int[] worklevels, final int provisionalNumLevels,
       final int myCurNumLevels, final int[] myCurLevelsArr, final float[] myCurFloatItemsArr,
       final int otherNumLevels, final int[] otherLevelsArr, final float[] otherFloatItemsArr) {

src/main/java/org/apache/datasketches/kll/KllFloatsSketch.java

@@ -276,6 +276,7 @@ public QuantilesFloatsSketchIterator iterator() {
   @Override
   public final void merge(final KllSketch other) {
     if (readOnly || sketchStructure != UPDATABLE) { throw new SketchesArgumentException(TGT_IS_READ_ONLY_MSG); }
+    if (this == other) { throw new SketchesArgumentException(SELF_MERGE_MSG); }
     final KllFloatsSketch othFltSk = (KllFloatsSketch)other;
     if (othFltSk.isEmpty()) { return; }
     KllFloatsHelper.mergeFloatImpl(this, othFltSk);

src/main/java/org/apache/datasketches/kll/KllHeapFloatsSketch.java

@@ -288,7 +288,7 @@ void incNumLevels() {
 
   @Override
   void setNumLevels(final int numLevels) {
-  //the heap sketch computes num levels from the array itself, so this is not used on-heap
+    //the heap sketch computes num levels from the array itself, so this is not used on-heap
   }
 
   @Override

src/main/java/org/apache/datasketches/kll/KllItemsHelper.java

@@ -133,7 +133,7 @@ static <T> void mergeItemImpl(final KllItemsSketch<T> mySketch,
     final Object myMin = myEmpty ? null : mySketch.getMinItem();
     final Object myMax = myEmpty ? null : mySketch.getMaxItem();
     final int myMinK = mySketch.getMinK();
-    final long finalN = mySketch.getN() + otherItmSk.getN();
+    final long finalN = Math.addExact(mySketch.getN(), otherItmSk.getN());
 
     //buffers that are referenced multiple times
     final int otherNumLevels = otherItmSk.getNumLevels();
@@ -399,7 +399,7 @@ private static <T> int[] generalItemsCompress(
       curLevel++; // start out at level 0
 
       // If we are at the current top level, add an empty level above it for convenience,
-      // but do not increment numLevels until later
+      // but do not actually increment numLevels until later
       if (curLevel == (numLevels - 1)) {
         inLevels[curLevel + 2] = inLevels[curLevel + 1];
       }
@@ -466,7 +466,7 @@ private static <T> int[] generalItemsCompress(
     return new int[] {numLevels, targetItemCount, currentItemCount};
   }
 
-  private static <T> void populateItemWorkArrays(
+  private static <T> void populateItemWorkArrays( //workBuf and workLevels are modified
       final Object[] workbuf, final int[] worklevels, final int provisionalNumLevels,
       final int myCurNumLevels, final int[] myCurLevelsArr, final Object[] myCurItemsArr,
       final int otherNumLevels, final int[] otherLevelsArr, final Object[] otherItemsArr,

src/main/java/org/apache/datasketches/kll/KllItemsSketch.java

@@ -251,6 +251,7 @@ public QuantilesGenericSketchIterator<T> iterator() {
   @Override
   public final void merge(final KllSketch other) {
     if (readOnly || sketchStructure != UPDATABLE) { throw new SketchesArgumentException(TGT_IS_READ_ONLY_MSG); }
+    if (this == other) { throw new SketchesArgumentException(SELF_MERGE_MSG); }
     final KllItemsSketch<T> othItmSk = (KllItemsSketch<T>)other;
     if (othItmSk.isEmpty()) { return; }
     KllItemsHelper.mergeItemImpl(this, othItmSk, comparator);