dungba88 commented on code in PR #12738:
URL: https://github.com/apache/lucene/pull/12738#discussion_r1378601593
##########
lucene/core/src/java/org/apache/lucene/util/fst/NodeHash.java:
##########
@@ -186,119 +193,85 @@ private long hash(FSTCompiler.UnCompiledNode<T> node) {
return h;
}
- // hash code for a frozen node. this must precisely match the hash
computation of an unfrozen
- // node!
- private long hash(long node) throws IOException {
- final int PRIME = 31;
-
- long h = 0;
- fstCompiler.fst.readFirstRealTargetArc(node, scratchArc, in);
- while (true) {
- h = PRIME * h + scratchArc.label();
- h = PRIME * h + (int) (scratchArc.target() ^ (scratchArc.target() >>
32));
- h = PRIME * h + scratchArc.output().hashCode();
- h = PRIME * h + scratchArc.nextFinalOutput().hashCode();
- if (scratchArc.isFinal()) {
- h += 17;
- }
- if (scratchArc.isLast()) {
- break;
- }
- fstCompiler.fst.readNextRealArc(scratchArc, in);
- }
-
- return h;
- }
-
- /**
- * Compares an unfrozen node (UnCompiledNode) with a frozen node at byte
location address (long),
- * returning true if they are equal.
- */
- private boolean nodesEqual(FSTCompiler.UnCompiledNode<T> node, long address)
throws IOException {
- fstCompiler.fst.readFirstRealTargetArc(address, scratchArc, in);
-
- // fail fast for a node with fixed length arcs
- if (scratchArc.bytesPerArc() != 0) {
- assert node.numArcs > 0;
- // the frozen node uses fixed-with arc encoding (same number of bytes
per arc), but may be
- // sparse or dense
- switch (scratchArc.nodeFlags()) {
- case FST.ARCS_FOR_BINARY_SEARCH:
- // sparse
- if (node.numArcs != scratchArc.numArcs()) {
- return false;
- }
- break;
- case FST.ARCS_FOR_DIRECT_ADDRESSING:
- // dense -- compare both the number of labels allocated in the array
(some of which may
- // not actually be arcs), and the number of arcs
- if ((node.arcs[node.numArcs - 1].label - node.arcs[0].label + 1) !=
scratchArc.numArcs()
- || node.numArcs != FST.Arc.BitTable.countBits(scratchArc, in)) {
- return false;
- }
- break;
- default:
- throw new AssertionError("unhandled scratchArc.nodeFlag() " +
scratchArc.nodeFlags());
- }
- }
-
- // compare arc by arc to see if there is a difference
- for (int arcUpto = 0; arcUpto < node.numArcs; arcUpto++) {
- final FSTCompiler.Arc<T> arc = node.arcs[arcUpto];
- if (arc.label != scratchArc.label()
- || arc.output.equals(scratchArc.output()) == false
- || ((FSTCompiler.CompiledNode) arc.target).node !=
scratchArc.target()
- || arc.nextFinalOutput.equals(scratchArc.nextFinalOutput()) == false
- || arc.isFinal != scratchArc.isFinal()) {
- return false;
- }
-
- if (scratchArc.isLast()) {
- if (arcUpto == node.numArcs - 1) {
- return true;
- } else {
- return false;
- }
- }
-
- fstCompiler.fst.readNextRealArc(scratchArc, in);
- }
-
- // unfrozen node has fewer arcs than frozen node
-
- return false;
- }
-
/** Inner class because it needs access to hash function and FST bytes. */
private class PagedGrowableHash {
+ public long copiedBytes;
private PagedGrowableWriter entries;
+ // mapping from FST real address to copiedNodes offsets
+ private PagedGrowableWriter copiedOffsets;
private long count;
+ // mask for entries
private long mask;
+ // mask for copiedOffsets
+ private long offsetMask;
+ private final List<byte[]> copiedNodes;
Review Comment:
I was trying to avoid double byte copy thus I used the list. I looked at
`BytesRefArray` and it seems it would still have the double byte copy problem
like `ByteBlockPool`:
- When we call `append(BytesRef)`, the byte[] will be copied into the
`ByteBlockPool`. We already had 1 copy when (1) reading from the BytesStore on
adding node and (2) reading from the fallback table on promotion.
- Similarly calling `get(BytesRef, int)` would also require a copy from the
`ByteBlockPool` into a temporary `byte[]`
- Using `List`, on promotion we can also just share the node `byte[]`, no
copy here and memory is shared, thus I think it would be more efficient on both
CPU and memory footprint?
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