Benchmarks

The repo ships two parallel bench harnesses that compare the two codegen paths — the direct-emit codegen (default) and the AST walker (:emit<ast>, see API) — on a fixed set of representative templates:

• specs/bench/render-spec.raku — BDD-Behave spec, tagged :tag<benchmark> so it is skipped by the default test run and driven separately via behave --benchmark specs/bench/.

• t/0790-bench.rakutest — prove6-style harness, skipped unless HAML_RUN_BENCH=1 is set in the environment.

Both files share the same template cases and the same render setup, so either entry point produces a comparable measurement.

Run

From the project root, driving the BDD-Behave spec:

behave --benchmark specs/bench/

Driving the prove6 harness:

HAML_RUN_BENCH=1 prove6 -Ilib t/0790-bench.rakutest

Both harnesses honor HAML_BENCH_ITERS to override the iteration count (default 5000 for the BDD spec, 100 for the prove6 test):

HAML_BENCH_ITERS=20000 behave --benchmark specs/bench/
HAML_BENCH_ITERS=1000 HAML_RUN_BENCH=1 prove6 -Ilib t/0790-bench.rakutest

Output

The prove6 harness prints one TAP diagnostic per case:

# static tags only                  iters=100  ast=8.41ms  direct=2.31ms  speedup=3.64x
# inline expressions                iters=100  ast=4.92ms  direct=1.43ms  speedup=3.44x
# for-loop over a list              iters=100  ast=44.7ms  direct=12.8ms  speedup=3.49x
...

The BDD-Behave benchmark mode renders comparable per-case tables driven by the benchmark 'ast' { ... } / benchmark 'direct' { ... } blocks inside the spec.

Each case is warmed once for both paths before the timed loop, so the per-template precompile/EVAL cost is excluded from the timings — what's being measured is steady-state render speed.

Cases

The cases are declared in specs/bench/render-spec.raku (mirrored by t/0790-bench.rakutest). Each entry is a (name, src, locals) record. Add a case by appending to the list — the harnesses pick it up automatically.

Caveats

• The numbers are wall-clock and depend on machine load. Run a few times if the comparison is close.

• The harness times HAML.render(:src, ...) end-to-end. The first render for each path warms internal caches; subsequent renders reuse the cached closure, so the times reflect the steady-state cost, not first-render cost.

• :emit<direct> covers the same template-level features as the AST renderer (trim modifiers, remove-whitespace, preserved tags with children, tab-offset propagation). The only path it does not yet drive is streaming (HAML.render-supply), which stays on the AST renderer regardless of :emit. See API: Feature parity with the AST renderer.