Update outdated RLE paper and improve some code refactoring (#4286)

* Update outdated RLE paper and improve some code refactoring

* Roll back CONCISE's abbreviation

extendedset/src/main/java/io/druid/extendedset/intset/AbstractIntSet.java

@@ -126,8 +126,7 @@ public abstract class AbstractIntSet implements IntSet
   public boolean containsAny(IntSet c)
   {
     IntIterator itr = c.iterator();
-    boolean res = true;
+    while (itr.hasNext()) {
-    while (res && itr.hasNext()) {
       if (contains(itr.next())) {
         return true;
       }

extendedset/src/main/java/io/druid/extendedset/intset/ConciseSet.java

@@ -41,9 +41,9 @@ import java.util.SortedSet;
  * This class is an instance of {@link IntSet} internally represented by
  * compressed bitmaps though a RLE (Run-Length Encoding) compression algorithm.
  * See <a
- * href="http://ricerca.mat.uniroma3.it/users/colanton/docs/concise.pdf">http
+ * href="http://ricerca.mat.uniroma3.it/users/dipietro/publications/0020-0190.pdf">
- * ://ricerca.mat.uniroma3.it/users/colanton/docs/concise.pdf</a> for more
+ * http://ricerca.mat.uniroma3.it/users/dipietro/publications/0020-0190.pdf</a>
- * details.
+ * for more details.
  * <p/>
  * Notice that the iterator by {@link #iterator()} is <i>fail-fast</i>,
  * similar to most {@link Collection}-derived classes. If the set is
@@ -139,8 +139,8 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
    * than a power of 2 takes at most <tt>O(lg(32))</tt> time. The number of operations
    * is at most <tt>12 + 9 * ceil(lg(32))</tt>.
    * <p/>
-   * See <a
+   * See <a href="http://graphics.stanford.edu/~seander/bithacks.html">
-   * href="http://graphics.stanford.edu/~seander/bithacks.html">http://graphics.stanford.edu/~seander/bithacks.html</a>
+   *   http://graphics.stanford.edu/~seander/bithacks.html</a>
    *
    * @param n number to divide
    *
@@ -546,10 +546,10 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
    */
   private void appendLiteral(int word)
   {
-    // when we have a zero sequence of the maximum lenght (that is,
+    // when we have a zero sequence of the maximum length (that is,
     // 00.00000.1111111111111111111111111 = 0x01FFFFFF), it could happen
     // that we try to append a zero literal because the result of the given operation must be an
-    // empty set. Whitout the following test, we would have increased the
+    // empty set. Without the following test, we would have increased the
     // counter of the zero sequence, thus obtaining 0x02000000 that
     // represents a sequence with the first bit set!
     if (lastWordIndex == 0 && word == ConciseSetUtils.ALL_ZEROS_LITERAL && words[0] == 0x01FFFFFF) {
@@ -1380,10 +1380,10 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
           // -- If the literal is made up of all zeros, it definitely
           //    cannot be part of a sequence (otherwise it would not have
           //    been created). Thus, we can create a 1-bit literal word
-          // -- If there are MAX_LITERAL_LENGHT - 2 set bits, by adding
+          // -- If there are MAX_LITERAL_LENGTH - 2 set bits, by adding
           //    the new one we potentially allow for a 1's sequence
           //    together with the successive word
-          // -- If there are MAX_LITERAL_LENGHT - 1 set bits, by adding
+          // -- If there are MAX_LITERAL_LENGTH - 1 set bits, by adding
           //    the new one we potentially allow for a 1's sequence
           //    together with the successive and/or the preceding words
           if (!simulateWAH) {
@@ -1616,10 +1616,7 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
     // completely "covers" the second operator
     if (isSequenceWithNoBits(this.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(this.words[0]) + 1) > other.last) {
-      if (isZeroSequence(this.words[0])) {
+      return !isZeroSequence(this.words[0]);
-        return false;
-      }
-      return true;
     }
     if (isSequenceWithNoBits(other.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(other.words[0]) + 1) > this.last) {
@@ -1702,17 +1699,11 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
     // disjoint sets
     if (isSequenceWithNoBits(this.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(this.words[0]) + 1) > other.last) {
-      if (isZeroSequence(this.words[0])) {
+      return !isZeroSequence(this.words[0]);
-        return false;
-      }
-      return true;
     }
     if (isSequenceWithNoBits(other.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(other.words[0]) + 1) > this.last) {
-      if (isZeroSequence(other.words[0])) {
+      return !isZeroSequence(other.words[0]);
-        return false;
-      }
-      return true;
     }
 
     // scan "this" and "other"
@@ -1791,17 +1782,11 @@ public class ConciseSet extends AbstractIntSet implements java.io.Serializable
     // disjoint sets
     if (isSequenceWithNoBits(this.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(this.words[0]) + 1) > other.last) {
-      if (isZeroSequence(this.words[0])) {
+      return !isZeroSequence(this.words[0]);
-        return false;
-      }
-      return true;
     }
     if (isSequenceWithNoBits(other.words[0])
         && maxLiteralLengthMultiplication(getSequenceCount(other.words[0]) + 1) > this.last) {
-      if (isZeroSequence(other.words[0])) {
+      return !isZeroSequence(other.words[0]);
-        return false;
-      }
-      return true;
     }
 
     // resulting size

extendedset/src/main/java/io/druid/extendedset/intset/ConciseSetUtils.java

@@ -330,7 +330,7 @@ public class ConciseSetUtils
 
   public static int clearBitsAfterInLastWord(int lastWord, int lastSetBit)
   {
-    return lastWord &= ALL_ZEROS_LITERAL | (0xFFFFFFFF >>> (31 - lastSetBit));
+    return lastWord & (ALL_ZEROS_LITERAL | (0xFFFFFFFF >>> (31 - lastSetBit)));
   }
 
   public static int onesUntil(int bit)

extendedset/src/main/java/io/druid/extendedset/intset/ImmutableConciseSet.java

@@ -39,7 +39,7 @@ public class ImmutableConciseSet
   {
     // Comparison is first by index, then one fills < literals < zero fills
     // one fills are sorted by length (longer one fills have priority)
-    // similarily, shorter zero fills have priority
+    // similarly, shorter zero fills have priority
     @Override
     public int compare(WordIterator i1, WordIterator i2)
     {
@@ -82,7 +82,7 @@ public class ImmutableConciseSet
   {
     // Comparison is first by index, then zero fills < literals < one fills
     // zero fills are sorted by length (longer zero fills have priority)
-    // similarily, shorter one fills have priority
+    // similarly, shorter one fills have priority
     @Override
     public int compare(WordIterator i1, WordIterator i2)
     {

extendedset/src/test/java/io/druid/extendedset/intset/ImmutableConciseSetTest.java

@@ -25,6 +25,7 @@ import org.junit.runners.Parameterized;
 import java.nio.IntBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.NoSuchElementException;
@@ -1182,7 +1183,7 @@ public class ImmutableConciseSetTest
   {
     final int[] ints1 = {33, 100000};
     final int[] ints2 = {34, 100000};
-    List<Integer> expected = Arrays.asList(100000);
+    List<Integer> expected = Collections.singletonList(100000);
 
     ConciseSet set1 = new ConciseSet();
     for (int i : ints1) {
@@ -1655,7 +1656,7 @@ public class ImmutableConciseSetTest
   @Test
   public void testIntersectionTerminates() throws Exception
   {
-    verifyIntersection(Arrays.<Integer>asList(), Arrays.asList(new ImmutableConciseSet(), new ImmutableConciseSet()));
+    verifyIntersection(Collections.emptyList(), Arrays.asList(new ImmutableConciseSet(), new ImmutableConciseSet()));
   }
 
   private void verifyIntersection(ConciseSet set1, ConciseSet set2)