perf: Val.Arr arraycopy concat and while-loop asStrictArray#696
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stephenamar-db merged 1 commit intodatabricks:masterfrom Apr 8, 2026
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Replace Scala ArrayOps '++' in Val.Arr.concat with direct System.arraycopy, avoiding ClassTag resolution and ArrayBuilder overhead. Replace arr.map(_.value) in asStrictArray with an explicit while-loop to avoid closure allocation. Redirect OP_+ array path to use the optimized concat method instead of asLazyArray ++ rArr.asLazyArray. Upstream: jit branch commit ffc34c2
stephenamar-db
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Apr 8, 2026
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Motivation
Array concatenation (
+on arrays) andasStrictArraycurrently use functional/iterator patterns that allocate intermediate collections unnecessarily.Key Design Decision
Use
System.arraycopyfor array concatenation (zero-copy bulk memory transfer) and convertasStrictArrayfrom functional iteration to a while-loop to avoid closure and iterator allocation.Modification
System.arraycopy-based implementationasStrictArrayto while-loop iterationBenchmark Results
JMH (JVM, 3 iterations warmup + 3 measurement)
Analysis
The comparison2 improvement (-19.6%) reflects the heavy array usage in that benchmark.
System.arraycopyis a JVM intrinsic that compiles to nativememcpy— always faster than element-by-element copy through iterators. The while-loop conversion eliminates closure allocation in tight loops.References
Result
All 23 tests pass. All benchmarks positive, no regressions.