Avoid intermediate Map allocations and tuple boxing in groupFlatMap#79
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The Result/AbstractFunction1 pattern finalized builders via repeated calls to immutable.Map#updated, which rebuilds trie nodes on every call and discards all but the final version as garbage. Replace it with a single Map builder populated via foreachEntry: val b = immutable.Map.newBuilder[K, CC[B]] m.foreachEntry((k, bldr) => b += ((k, bldr.result()))) b.result() This avoids both problems in one pass: results are staged once and frozen once (no repeated .updated trie rebuilds), and foreachEntry traverses m's internal table directly instead of going through m.iterator, so no (K, Builder) pair is boxed per entry just to be immediately unpacked again (as view.mapValues(_.result()).toMap would do). Same O(n + k) complexity (n = elements, k = groups), fewer allocations on both counts. Also enhance tests in group-flat-map.scala to cover more cases: duplicate keys from expansion, cross-element duplicates within a group, mixed expansion sizes, and empty-expansion groups.
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@bishabosha I tried to reproduce the problem by running the same command locally but it didn't fail, can you try rerun the failed CI? Thanks. |
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The Result/AbstractFunction1 pattern finalized builders via repeated
calls to immutable.Map#updated, which rebuilds trie nodes on every
call and discards all but the final version as garbage.
Replace it with a single Map builder populated via foreachEntry:
This avoids both problems in one pass: results are staged once and
frozen once (no repeated .updated trie rebuilds), and foreachEntry
traverses m's internal table directly instead of going through
m.iterator, so no (K, Builder) pair is boxed per entry just to be
immediately unpacked again (as view.mapValues(_.result()).toMap
would do). Same O(n + k) complexity (n = elements, k = groups),
fewer allocations on both counts.
Enhanced the test in group-flat-map.scala to cover more cases.