Two new throughput fixtures targeting blind spots in the 21'a
corpus:
- bench_closure_chain exercises the build_pair_drop_fn codegen
path (the 18c.4 doubled-braces trigger). Each iteration of
run_loop allocates a {thunk, env} closure pair via the
let-rec-name-as-value escape route. Sizes 10k / 100k / 500k.
rc/bump = 4.14x — materially worse than the 2.91x / 2.59x of
the linear/tree fixtures, exposing that closure work pays the
RC alloc tax twice (pair + env-struct).
- bench_hof_pipeline exercises poly-ADT instantiation and
indirect dispatch via fold_with_fn over List<a>. Sizes 100k /
1M / 3M elements. Ratios essentially match bench_list_sum,
confirming the 13b static-template-plus-ctor-inline design
has zero measurable overhead at this scale.
Baseline file extends from 31 to 47 metrics. The two new fixtures
build clean under all three allocators; the rc-arm build exercises
the per-type drop fn for the closure-pair, providing a tripwire
for any future 18c.4-class IR malformedness.
JOURNAL records both surprises (4.14x closure tax, ~zero HOF/poly
overhead) and explicitly notes the dispersion observation on
explicit_at_rc.p99 — three captures today (357.5 / 294.6 / 251.5)
confirm wide run-to-run variance on that fixture. Methodology
upgrade (n>=10 captures or tighter fixture) deferred to 21'c.
bench/run.sh fixtures array updated. bench/check.py needed no
changes — its parser handles the wider table by metric name.
Brummel
07bff24527