jpountz commented on a change in pull request #966: LUCENE-9024 Optimize
IntroSelector to use median of medians
URL: https://github.com/apache/lucene-solr/pull/966#discussion_r338913879
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File path: lucene/core/src/java/org/apache/lucene/util/IntroSelector.java
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@@ -33,26 +32,87 @@ public final void select(int from, int to, int k) {
quickSelect(from, to, k, maxDepth);
}
- // heap sort
- // TODO: use median of median instead to have linear worst-case rather than
- // n*log(n)
- void slowSelect(int from, int to, int k) {
- new Sorter() {
+ int slowSelect(int from, int to, int k) {
+ return medianOfMediansSelect(from, to-1, k);
+ }
+
+ int medianOfMediansSelect(int from, int to, int k) {
Review comment:
It took me a while to figure out that `to` is inclusive here while it is
exclusive elsewhere in this file (e.g. in `select` and `quickselecet`). Maybe
rename it to `toInclusive` or something along those lines to make it clear? Or
maybe call them `left` and `right` like you did in some other methods?
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