b771908e5b
Add a PNG writer so the demos produce actual images. Two pieces: - src/jolt/png.janet — the encoder (8-bit RGB, filter None, stored/uncompressed DEFLATE so no compressor is needed; correct CRC32 + Adler32). It lives in Janet because per-byte work in the overlay is far too slow (a byte-array aset loop is ~30s for 360k bytes, and CRC32 over even a tiny image would be worse). Janet's bit ops are 32-bit signed, so the 32-bit-unsigned arithmetic is done with plain number ops (doubles hold 2^32) plus byte-level bxor. Exposed to the overlay as janet.png/* by importing it into eval_base's module-load-env. - src/jolt/jolt/png.clj — the jolt.png overlay wrapper: image / put! / write. The overlay only produces pixels; the host encodes them in one pass. mandelbrot gets a `render` subcommand (jolt -m mandelbrot render out.png [size]) that colours count-point's escape counts; the numeric-arg bench path is untouched. Verified end to end: macOS `sips` accepts the output (so CRC/zlib are valid). png-test covers the encoder structure (signature/IHDR/IEND) and the overlay round-trip. Co-authored-by: Yogthos <yogthos@gmail.com> |
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|---|---|---|
| .. | ||
| binary_trees.clj | ||
| collections.clj | ||
| dispatch.clj | ||
| dump-mandelbrot-emit.janet | ||
| fib.clj | ||
| mandelbrot-hand-rec.janet | ||
| mandelbrot-hand.janet | ||
| mandelbrot.clj | ||
| mono_dispatch.clj | ||
| README.md | ||
| run.sh | ||
jolt benchmark suite
Benchmarks that isolate the workload axes jolt's optimizing passes target. The
ray tracer (examples/ray-tracer) is float-compute-bound — its time is
irreducible algorithmic math (hit-testing + transcendentals), and devirt,
allocation removal, and type-proving all measured flat on it. So it can't
tell us whether those passes work. These benchmarks make each pass's target
workload the dominant cost.
Reference: the cross-language suites these draw from — Are We Fast Yet? (Marr et al., DLS '16) and the Computer Language Benchmarks Game. The benchmarks are portable Clojure, so they also run on JVM Clojure for an absolute reference.
Benchmarks
| Benchmark | Axis | Pass it exercises | Source |
|---|---|---|---|
binary-trees |
allocation / GC pressure (escaping short-lived records) | jolt-15jq scalar-replace, jolt-8flj escape analysis | CLBG |
dispatch |
polymorphic (megamorphic) protocol dispatch | jolt-41m devirt, inline-cache | AWFY-style |
mono-dispatch |
monomorphic protocol dispatch (devirt/inline-cache can fire) | jolt-41m devirt, jolt-ez5h inline-cache | AWFY-style |
collections |
persistent map/vector churn (HAMT / 32-way tries) | persistent structures (jolt-684u/0hbr), transients | CLBG k-nucleotide-style |
mandelbrot |
pure float compute (tight arith loops, no alloc/dispatch) | jolt-3pl native arith, loop codegen | CLBG |
fib |
recursion: function-call + integer-arith overhead | jolt-3pl native arith, jolt-826 small-fn inlining | CLBG |
What the ray tracer does not capture and these do: allocation as the bottleneck (~7% there), megamorphic and monomorphic dispatch (its dispatch is monomorphic and cheap), persistent-collection throughput (it uses fixed records, no collections in the hot loop), and isolated compute/call overhead.
Planned additions: Richards / DeltaBlue (heavier OO dispatch), NBody (float control with record state), k-nucleotide proper.
Holistic scorecard
JVM=1 bench/run.sh runs each benchmark on jolt and JVM Clojure and prints
the jolt/JVM ratio — the epic's (jolt-ffn) absolute-reference scorecard. As of
the broadening (2026-06-16), ratios cluster by axis:
- pure compute (
mandelbrot) is the floor, ~15× — native arith (jolt-3pl) already gets jolt closest to the JVM. - collections ~28×, fib ~37×.
- dispatch ~75× (megamorphic), and
mono-dispatchis worse (~110×): the JVM inline-caches a runtime-monomorphic call site to near-free, while jolt does a full registry dispatch regardless (devirt only fires on statically proven receivers, whichreduceover a vector doesn't give). This is the signal for the call-site inline cache (jolt-ez5h). - allocation (
binary-trees) is the widest gap — but also the most inflated by host memory pressure, so read it as "alloc is the worst axis," not a precise multiple. Numbers are machine-specific; regenerate withJVM=1 bench/run.sh.
Running
jpm build && export PATH="$PWD/build:$PATH"
bench/run.sh # whole-program optimization on (default)
JOLT_WHOLE_PROGRAM=0 bench/run.sh # WP off, to measure what WP buys
bench/run.sh binary-trees 16 # one benchmark, custom size
A/B against a change
To measure a pass, run the suite on main, then on the branch, back to back
(same machine, quiet) — the protocol used for test/bench/core-bench.janet and
the ray tracer. Each benchmark prints runs: [...] and mean: N ms; compare
the means. A pass is worth landing when it moves a benchmark whose axis it
targets, even if the ray tracer stays flat.