jpountz commented on a change in pull request #556: LUCENE-8673: Use radix
partitioning when merging dimensional points
URL: https://github.com/apache/lucene-solr/pull/556#discussion_r254284219
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File path: lucene/core/src/java/org/apache/lucene/util/bkd/BKDWriter.java
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@@ -194,40 +169,28 @@ protected BKDWriter(int maxDoc, Directory tempDir,
String tempFileNamePrefix, in
minPackedValue = new byte[packedIndexBytesLength];
maxPackedValue = new byte[packedIndexBytesLength];
- // If we may have more than 1+Integer.MAX_VALUE values, then we must
encode ords with long (8 bytes), else we can use int (4 bytes).
- this.longOrds = longOrds;
-
- this.singleValuePerDoc = singleValuePerDoc;
+ // dimensional values (numDims * bytesPerDim) + docID (int)
+ bytesPerDoc = packedBytesLength + Integer.BYTES;
- // dimensional values (numDims * bytesPerDim) + ord (int or long) + docID
(int)
- if (singleValuePerDoc) {
- // Lucene only supports up to 2.1 docs, so we better not need longOrds
in this case:
- assert longOrds == false;
- bytesPerDoc = packedBytesLength + Integer.BYTES;
- } else if (longOrds) {
- bytesPerDoc = packedBytesLength + Long.BYTES + Integer.BYTES;
- } else {
- bytesPerDoc = packedBytesLength + Integer.BYTES + Integer.BYTES;
- }
// As we recurse, we compute temporary partitions of the data, halving the
// number of points at each recursion. Once there are few enough points,
// we can switch to sorting in heap instead of offline (on disk). At any
// time in the recursion, we hold the number of points at that level, plus
// all recursive halves (i.e. 16 + 8 + 4 + 2) so the memory usage is 2X
// what that level would consume, so we multiply by 0.5 to convert from
- // bytes to points here. Each dimension has its own sorted partition, so
- // we must divide by numDims as wel.
+ // bytes to points here. In addition the radix partitioning may sort on
memory
+ // double of this size so we multiply by another 0.5.
- maxPointsSortInHeap = (int) (0.5 * (maxMBSortInHeap * 1024 * 1024) /
(bytesPerDoc * numDataDims));
+ maxPointsSortInHeap = (int) (0.25 * (maxMBSortInHeap * 1024 * 1024) /
(bytesPerDoc));
Review comment:
I understand the first 0.5 factor due to how recursion levels add up, but
not the second one.
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