el #132's quadratic (strlen per character in str_char_code/str_slice) is
pure CPU and allocates NOTHING. Measured on three controlled specimens:
specimen allocs bytes time
linear 2.00 -> O(n) 2.16 -> O(n) 2.05 -> O(n)
accum 2.00 -> O(n) 3.99 -> O(n2) noisy
compute FLAT FLAT 3.96 -> O(n2)
'compute' is #132's shape. A gate fitting only allocation count and bytes
classifies it FLAT and passes -- it would not have caught the defect it
was created for. The gate now fits time AND count AND bytes, failing if
any exceeds its declared curve.
Also: black_box is mandatory and consuming the result is NOT sufficient.
The first 'compute' reported 0us at every n while returning a correct n2 --
clang closed the loop to a multiply. Only an opaque call restored the curve.
Adds lang/tests/bench/fitprobe.el as the fitter's known-good/known-bad set,
so the classifier is provable without depending on a real bug existing.
Marks DESIGN.md 1.3 stale: test_compiler 3.58s -> 0.03s (119x).
Neuron
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