jank's ray tracer benchmark (examples/ray-tracer) drops from 165.6s to
15.8s per render (10.5x) — from 118x JVM Clojure to 11x. The changes
mirror the optimizations in jank's June 2026 post, adapted to the
janet backend (jolt-4vr, jolt-h79):
- (:kw m) emits an inline lookup instead of variadic jolt-call ->
core-get's predicate chain. The guard is (get m :jolt/type): janet
compiles get to an opcode (~17ns) where a struct? cfunction call
costs ~85ns/lookup. :jolt/type is reserved (the reader rejects it in
map literals) and every table rep that must not be raw-indexed
carries it — phm tables now tagged too — so tagged values route to
core-get and everything else gets janet get, which matches core-get
for keyword keys on structs/records/nil/arrays. 929ns -> 90ns.
- {:k v ...} literals with scalar const keys emit let-bound values, an
`and` truthiness test (pure branch opcodes), and a native (struct ...)
call instead of variadic build-map-literal + runtime kv re-scan. nil
or false values fall back to build-map-literal, which keeps Clojure's
nil-entry semantics via the phm rep. 890ns -> 246ns.
- native-op additions: min/max (janet's are variadic with the same
numeric semantics), nil?/some? lowered to janet's fastfun = / not=
against nil, and not.
- clojure.math (Clojure 1.11) installed as a namespace whose vars hold
janet's math natives directly, so calls direct-link. Math/sqrt-style
interop stays in the frozen interpret-only punt set (~5us/call); this
is the compiled route (~30ns).
- reduce over pvec/tuple/array iterates indexed in place — it was
copying the whole pvec into a fresh array on every reduce call — and
stops at `reduced` instead of scanning the tail.
- interpreter coll-lookup gains the sorted-coll arm: (:k (sorted-map ..))
was nil in interpret mode (compiled mode had it right).
map-fastpath-spec pins keyword-invoke/map-literal semantics (16+15
rows incl. nil-value maps, records, sorted, vectors-of-internals) and
clojure.math (10 rows). Two pre-existing bugs found and filed while
writing it: map literals evaluate entries in reader-hash order
(jolt-p3c), and an attempted local-callee call inline that breaks
overlay lazy self-recursion is parked with a repro (jolt-507).
Gate green, conformance 335/335 x3, suite 4718 steady, core bench even
with main back-to-back.
8b2be06b68