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Chunk range/map/filter to match JVM Clojure

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range, map, and filter were fully element-by-element lazy, so
(map f (range 1 50)) realized one element per first/nth where JVM
Clojure realizes a whole 32-element chunk. range is a chunked
LongRange on the JVM and map/filter are chunk-preserving, so the
observable side-effect timing differed.

Following clojure.lang.LongRange, ChunkedCons, ChunkBuffer and
core.clj, this adds a crest field to the cseq record and a
cseq-chunked constructor modeling ChunkedCons (a standalone chunk
pvec, an offset, and the after-chunk seq). The chunk accessors move
to seq.ss next to the representation they read. map/filter/remove
take a chunked branch when the source is chunked, realizing the whole
chunk and chunk-cons'ing it onto a lazy rest, so their output is
itself chunked and chained transforms each batch by 32. Bounded range
is now an eager chunked seq, and the reduce fast path flows through a
ChunkedCons rest. The chunk-buffer/chunk/chunk-cons builder API in
natives-array.ss now produces a real ChunkedCons.

Single-arg (range), multi-coll map, and plain lazy seqs stay
element-by-element, like the JVM.

Adds a lazy / chunking suite to the corpus that observes realization
timing via an atom counter: first over a chunked map realizes 32,
crossing a chunk boundary realizes 49, chained maps batch [32 32],
filter applies the predicate to the whole first block, and a plain
lazy seq still realizes one element at a time. Two cases that
documented the old over-laziness now assert the JVM value of 32 and
were dropped from the allowlist. certify against JVM Clojure 1.12.3
reports 0 new and 0 stale divergences.
This commit is contained in:
Yogthos 2026-06-29 22:02:06 -04:00
parent c0a0ec98ee
commit bd33d605ef
5 changed files with 170 additions and 74 deletions
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4
test/conformance/known-divergences.edn
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@ -16,7 +16,7 @@
:seq-type-model
"jolt models every seq as PersistentList (eager) or LazySeq (deferred); JVM reifies a specialized class per producer (Cons/Iterate/LongRange/Repeat/Cycle/ChunkedSeq/StringSeq/KeySeq/RSeq/ArraySeq/SubVector). Values and laziness are correct, only (class …) differs. jolt-aei7",
:chunking-model
"jolt seqs are unchunked: forcing one element realizes one (JVM realizes a ~32-element chunk), and mapcat/dedupe realize 0 at construction where JVM forces the first chunk — jolt is a finer-grained lazy superset. jolt-mm6v",
"jolt now chunks range/vector seqs through map/filter like the JVM (forcing one element realizes the whole ~32-element chunk). What remains finer-grained: mapcat/dedupe realize 0 at construction where the JVM's (apply concat …) / sequence transformer force the first chunk just to build the seq. jolt-mm6v",
:integer-box-model
"jolt unifies every integer as one exact-integer type. A Chez fixnum is an immediate identical to the plain integer (no distinct identity to tag, no metadata on numbers), so (byte/short/int n) report Long, not Byte/Short/Integer. Value/arithmetic/equality are correct; a faithful narrow box would crash raw compiled (+ …) or de-optimize all arithmetic. jolt-k9sw"},
:entries
@ -53,8 +53,6 @@
{:suite "seq-type-model / specialized seq classes collapse", :label "sort", :category :seq-type-model}
{:suite "seq-type-model / specialized seq classes collapse", :label "subvec", :category :seq-type-model}
{:suite "seq-type-model / specialized seq classes collapse", :label "drop over a vector", :category :seq-type-model}
{:suite "chunking-model / unchunked realization granularity", :label "first over a vector realizes one, not a chunk", :category :chunking-model}
{:suite "chunking-model / unchunked realization granularity", :label "nth 0 over a vector realizes one", :category :chunking-model}
{:suite "chunking-model / unchunked realization granularity", :label "mapcat is fully lazy at construction", :category :chunking-model}
{:suite "chunking-model / unchunked realization granularity", :label "dedupe is fully lazy at construction", :category :chunking-model}
{:suite "integer-box-model / narrow int class collapses to Long", :label "byte class", :category :integer-box-model}