gf2121 commented on code in PR #14203:
URL: https://github.com/apache/lucene/pull/14203#discussion_r1997571999
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lucene/core/src/java/org/apache/lucene/util/bkd/DocIdsWriter.java:
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@@ -248,21 +281,68 @@ private void readBitSet(IndexInput in, int count, int[]
docIDs) throws IOExcepti
assert pos == count : "pos: " + pos + ", count: " + count;
}
- private static void readDelta16(IndexInput in, int count, int[] docIDs)
throws IOException {
+ private static void readDelta16(IndexInput in, int count, int[] docIds)
throws IOException {
final int min = in.readVInt();
- final int halfLen = count >>> 1;
- in.readInts(docIDs, 0, halfLen);
- for (int i = 0; i < halfLen; ++i) {
- int l = docIDs[i];
+ final int half = count >> 1;
+ in.readInts(docIds, 0, half);
+ if (count == BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE) {
+ // Same format, but enabling the JVM to specialize the decoding logic
for the default number
+ // of points per node proved to help on benchmarks
+ decode16(docIds, BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE / 2, min);
+ assert half * 2 == BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE
+ : "we are assuming DEFAULT_MAX_POINTS_IN_LEAF_NODE is a multiple of
2 here.";
+ } else {
+ decode16(docIds, half, min);
+ for (int i = half << 1; i < count; i++) {
+ docIds[i] = Short.toUnsignedInt(in.readShort()) + min;
+ }
+ }
+ }
+
+ private static void decode16(int[] docIDs, int half, int min) {
+ for (int i = 0; i < half; ++i) {
+ final int l = docIDs[i];
docIDs[i] = (l >>> 16) + min;
- docIDs[halfLen + i] = (l & 0xFFFF) + min;
+ docIDs[i + half] = (l & 0xFFFF) + min;
}
- if ((count & 1) == 1) {
- docIDs[count - 1] = Short.toUnsignedInt(in.readShort()) + min;
+ }
+
+ private void readInts24(IndexInput in, int count, int[] docIDs) throws
IOException {
+ int quarter = count >> 2;
+ int numInts = quarter * 3;
+ in.readInts(scratch, 0, numInts);
+ if (count == BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE) {
+ // Same format, but enabling the JVM to specialize the decoding logic
for the default number
+ // of points per node proved to help on benchmarks
+ decode24(
+ docIDs,
+ scratch,
+ BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE / 4,
+ BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE / 4 * 3);
+ assert quarter * 4 == BKDConfig.DEFAULT_MAX_POINTS_IN_LEAF_NODE
+ : " we are assuming DEFAULT_MAX_POINTS_IN_LEAF_NODE is a multiple of
4 here.";
+ } else {
+ decode24(docIDs, scratch, quarter, numInts);
+ // Now read the remaining 0, 1, 2 or 3 values
+ for (int i = quarter << 2; i < count; ++i) {
+ docIDs[i] = (in.readShort() & 0xFFFF) | (in.readByte() & 0xFF) << 16;
+ }
Review Comment:
I want to keep decode24 small so i put it under the `if else` block to save
the assertion. luceneutil and jmh proved it has similar performance.
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