LUCENE-10315: Speed up DocIdsWriter by ForUtil

lucene/CHANGES.txt

@@ -119,6 +119,8 @@ Optimizations
 * LUCENE-10503: Potential speedup for pure disjunctions whose clauses produce
   scores that are very close to each other. (Adrien Grand)
 
+* LUCENE-10315: Use SIMD instructions to decode BKD doc IDs. (Guo Feng, Adrien Grand, Ignacio Vera)
+
 Bug Fixes
 ---------------------
 * LUCENE-10477: Highlighter: WeightedSpanTermExtractor.extractWeightedSpanTerms to Query#rewrite

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/store/EndiannessReverserIndexInput.java

@@ -80,6 +80,14 @@ public void readLongs(long[] dst, int offset, int length) throws IOException {
     }
   }
 
+  @Override
+  public void readInts(int[] dst, int offset, int length) throws IOException {
+    in.readInts(dst, offset, length);
+    for (int i = 0; i < length; ++i) {
+      dst[offset + i] = Integer.reverseBytes(dst[offset + i]);
+    }
+  }
+
   @Override
   public void readFloats(float[] dst, int offset, int length) throws IOException {
     in.readFloats(dst, offset, length);

lucene/core/src/java/org/apache/lucene/store/ByteBufferGuard.java

@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.FloatBuffer;
+import java.nio.IntBuffer;
 import java.nio.LongBuffer;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -138,6 +139,11 @@ public void getLongs(LongBuffer receiver, long[] dst, int offset, int length) {
     receiver.get(dst, offset, length);
   }
 
+  public void getInts(IntBuffer receiver, int[] dst, int offset, int length) {
+    ensureValid();
+    receiver.get(dst, offset, length);
+  }
+
   public void getFloats(FloatBuffer receiver, float[] dst, int offset, int length) {
     ensureValid();
     receiver.get(dst, offset, length);

lucene/core/src/java/org/apache/lucene/store/ByteBufferIndexInput.java

@@ -22,6 +22,7 @@
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.FloatBuffer;
+import java.nio.IntBuffer;
 import java.nio.LongBuffer;
 
 /**
@@ -36,6 +37,7 @@
 public abstract class ByteBufferIndexInput extends IndexInput implements RandomAccessInput {
   private static final FloatBuffer EMPTY_FLOATBUFFER = FloatBuffer.allocate(0);
   private static final LongBuffer EMPTY_LONGBUFFER = LongBuffer.allocate(0);
+  private static final IntBuffer EMPTY_INTBUFFER = IntBuffer.allocate(0);
 
   protected final long length;
   protected final long chunkSizeMask;
@@ -46,6 +48,7 @@ public abstract class ByteBufferIndexInput extends IndexInput implements RandomA
   protected int curBufIndex = -1;
   protected ByteBuffer curBuf; // redundant for speed: buffers[curBufIndex]
   private LongBuffer[] curLongBufferViews;
+  private IntBuffer[] curIntBufferViews;
   private FloatBuffer[] curFloatBufferViews;
 
   protected boolean isClone = false;
@@ -83,6 +86,7 @@ protected void setCurBuf(ByteBuffer curBuf) {
     this.curBuf = curBuf;
     curLongBufferViews = null;
     curFloatBufferViews = null;
+    curIntBufferViews = null;
   }
 
   @Override
@@ -176,6 +180,37 @@ public void readLongs(long[] dst, int offset, int length) throws IOException {
     }
   }
 
+  @Override
+  public void readInts(int[] dst, int offset, int length) throws IOException {
+    // See notes about readLongs above
+    if (curIntBufferViews == null) {
+      curIntBufferViews = new IntBuffer[Integer.BYTES];
+      for (int i = 0; i < Integer.BYTES; ++i) {
+        if (i < curBuf.limit()) {
+          curIntBufferViews[i] =
+              curBuf.duplicate().position(i).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer();
+        } else {
+          curIntBufferViews[i] = EMPTY_INTBUFFER;
+        }
+      }
+    }
+    try {
+      final int position = curBuf.position();
+      guard.getInts(
+          curIntBufferViews[position & 0x03].position(position >>> 2), dst, offset, length);
+      // if the above call succeeded, then we know the below sum cannot overflow
+      curBuf.position(position + (length << 2));
+    } catch (
+        @SuppressWarnings("unused")
+        BufferUnderflowException e) {
+      super.readInts(dst, offset, length);
+    } catch (
+        @SuppressWarnings("unused")
+        NullPointerException npe) {
+      throw new AlreadyClosedException("Already closed: " + this);
+    }
+  }
+
   @Override
   public final void readFloats(float[] floats, int offset, int len) throws IOException {
     // See notes about readLongs above
@@ -503,6 +538,7 @@ private void unsetBuffers() {
     curBuf = null;
     curBufIndex = 0;
     curLongBufferViews = null;
+    curIntBufferViews = null;
   }
 
   /** Optimization of ByteBufferIndexInput for when there is only one buffer */

lucene/core/src/java/org/apache/lucene/store/DataInput.java

@@ -169,6 +169,20 @@ public void readLongs(long[] dst, int offset, int length) throws IOException {
     }
   }
 
+  /**
+   * Reads a specified number of ints into an array at the specified offset.
+   *
+   * @param dst the array to read bytes into
+   * @param offset the offset in the array to start storing ints
+   * @param length the number of ints to read
+   */
+  public void readInts(int[] dst, int offset, int length) throws IOException {
+    Objects.checkFromIndexSize(offset, length, dst.length);
+    for (int i = 0; i < length; ++i) {
+      dst[offset + i] = readInt();
+    }
+  }
+
   /**
    * Reads a specified number of floats into an array at the specified offset.
    *

lucene/core/src/java/org/apache/lucene/util/bkd/BKDReader.java

@@ -217,6 +217,7 @@ private static class BKDPointTree implements PointTree {
         scratchMaxIndexPackedValue;
     private final int[] commonPrefixLengths;
     private final BKDReaderDocIDSetIterator scratchIterator;
+    private final DocIdsWriter docIdsWriter;
     // if true the tree is balanced, otherwise unbalanced
     private final boolean isTreeBalanced;
 
@@ -303,6 +304,7 @@ private BKDPointTree(
       this.scratchDataPackedValue = scratchDataPackedValue;
       this.scratchMinIndexPackedValue = scratchMinIndexPackedValue;
       this.scratchMaxIndexPackedValue = scratchMaxIndexPackedValue;
+      this.docIdsWriter = scratchIterator.docIdsWriter;
     }
 
     @Override
@@ -570,7 +572,7 @@ public void addAll(PointValues.IntersectVisitor visitor, boolean grown) throws I
         // How many points are stored in this leaf cell:
         int count = leafNodes.readVInt();
         // No need to call grow(), it has been called up-front
-        DocIdsWriter.readInts(leafNodes, count, visitor);
+        docIdsWriter.readInts(leafNodes, count, visitor);
       } else {
         pushLeft();
         addAll(visitor, grown);
@@ -633,7 +635,7 @@ private int readDocIDs(IndexInput in, long blockFP, BKDReaderDocIDSetIterator it
       // How many points are stored in this leaf cell:
       int count = in.readVInt();
 
-      DocIdsWriter.readInts(in, count, iterator.docIDs);
+      docIdsWriter.readInts(in, count, iterator.docIDs);
 
       return count;
     }
@@ -1002,9 +1004,11 @@ private static class BKDReaderDocIDSetIterator extends DocIdSetIterator {
     private int offset;
     private int docID;
     final int[] docIDs;
+    private final DocIdsWriter docIdsWriter;
 
     public BKDReaderDocIDSetIterator(int maxPointsInLeafNode) {
       this.docIDs = new int[maxPointsInLeafNode];
+      this.docIdsWriter = new DocIdsWriter(maxPointsInLeafNode);
     }
 
     @Override

lucene/core/src/java/org/apache/lucene/util/bkd/BKDWriter.java

@@ -130,6 +130,7 @@ public class BKDWriter implements Closeable {
   private final long totalPointCount;
 
   private final int maxDoc;
+  private final DocIdsWriter docIdsWriter;
 
   public BKDWriter(
       int maxDoc,
@@ -165,7 +166,7 @@ public BKDWriter(
 
     // Maximum number of points we hold in memory at any time
     maxPointsSortInHeap = (int) ((maxMBSortInHeap * 1024 * 1024) / (config.bytesPerDoc));
-
+    docIdsWriter = new DocIdsWriter(config.maxPointsInLeafNode);
     // Finally, we must be able to hold at least the leaf node in heap during build:
     if (maxPointsSortInHeap < config.maxPointsInLeafNode) {
       throw new IllegalArgumentException(
@@ -1288,7 +1289,7 @@ private void writeLeafBlockDocs(DataOutput out, int[] docIDs, int start, int cou
       throws IOException {
     assert count > 0 : "config.maxPointsInLeafNode=" + config.maxPointsInLeafNode;
     out.writeVInt(count);
-    DocIdsWriter.writeDocIds(docIDs, start, count, out);
+    docIdsWriter.writeDocIds(docIDs, start, count, out);
   }
 
   private void writeLeafBlockPackedValues(