Avoid boxing the primitive when iterating ref-keyed/valued maps#1907
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brharrington merged 1 commit intoJun 4, 2026
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IntRefHashMap, RefIntHashMap, and RefDoubleHashMap exposed foreach as a Function2 callback. Because one parameter is a reference type, no specialized apply variant exists, so the generic apply(Object, Object) is used and the primitive (int key / int value / double value) is boxed on every element. This showed up as boxToInteger at IntRefHashMap.foreach being the Netflix#2 self-time leaf in a CPU profile, driven by RoaringTagIndex pattern queries (strPattern) scanning a key's value map. Replace the Function2 callback with a small single-abstract-method Consumer per map whose method carries the primitive directly (e.g. accept(int, T)); it erases to a primitive descriptor, so iteration no longer boxes. Call sites pass lambdas and are unchanged via SAM conversion. After the change RoaringTagIndex compiles with zero boxToInteger. Only these three maps box: the all-primitive maps (IntIntHashMap, DoubleIntHashMap, LongIntHashMap) and single-arg Function1 callbacks (foreachKey, the int/long sets, InternMap.retain) are already specialized by the compiler and were left unchanged. Adds a JMH benchmark contrasting the boxing Function2 path with the SAM.
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IntRefHashMap, RefIntHashMap, and RefDoubleHashMap exposed foreach as a Function2 callback. Because one parameter is a reference type, no specialized apply variant exists, so the generic apply(Object, Object) is used and the primitive (int key / int value / double value) is boxed on every element. This showed up as boxToInteger at IntRefHashMap.foreach being the #2 self-time leaf in a CPU profile, driven by RoaringTagIndex pattern queries (strPattern) scanning a key's value map.
Replace the Function2 callback with a small single-abstract-method Consumer per map whose method carries the primitive directly (e.g. accept(int, T)); it erases to a primitive descriptor, so iteration no longer boxes. Call sites pass lambdas and are unchanged via SAM conversion. After the change RoaringTagIndex compiles with zero boxToInteger.
Only these three maps box: the all-primitive maps (IntIntHashMap, DoubleIntHashMap, LongIntHashMap) and single-arg Function1 callbacks (foreachKey, the int/long sets, InternMap.retain) are already specialized by the compiler and were left unchanged.
Adds a JMH benchmark contrasting the boxing Function2 path with the SAM.