Brummel
75f7fda788
Closes the apples-to-apples gap from 21'e. Adds: - examples/bench_list_sum_explicit.ailx — same algorithm and sizes as bench_list_sum, fully (borrow)/(own)/(drop-iterative) annotated so codegen emits proper inc/dec instrumentation. - bench/reference/list_sum_explicit_free.c — same algorithm with explicit free() walking the chain after sum. The full alloc+dec vs malloc+free comparison reveals two non- trivial conclusions: 1. AILang's full RC pipeline is only 26% slower than glibc malloc+free on this workload (rc/c = 1.26x). The implicit- mode comparison's 1.42x was misleading — it counted neither pipeline's free path. The fair ratio is 1.26x, materially better than the previous read. 2. RC's dec is cheaper per cell than glibc free(). AILang dec-tax: ~3 ns/cell. C free-tax: ~5.5 ns/cell. Plausible cause: ailang_rc_dec operates on a known-shape cell with a fixed-offset refcount and a static per-type drop fn — no free-list bucketing, no header introspection, no global lock. bump's advantage expresses fully: bench_list_sum_explicit.bump/c = 0.42x means AILang at bump is 2.4x faster than C malloc+free. Sets a useful upper bound on a slab/pool RC allocator's potential. The 21'-family arc — bench-regression infrastructure — is now substantively complete: 21'a (bench/check.py), 21'b (corpus widening), 21'c (compile_check.py), 21'd (pure-compute fixtures + harness hardening), 21'e (cross-language hand-C), 21'f (explicit apples-to-apples). 63 runtime metrics + 18 compile metrics + 25 cross-lang metrics under regression coverage. Any future iter that regresses any axis beyond tolerance gets caught at the next family close. Remaining queue is back to substantive language work — Family 21 (typeclasses / polymorphic ADTs at runtime / pattern-binding generalisation) is now an orchestrator-level fork that needs direct user input.
77 lines
2.1 KiB
C
77 lines
2.1 KiB
C
// Hand-C reference for bench_list_sum_explicit — full malloc + free.
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//
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// Companion to list_sum.c (which leaks); this version adds explicit
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// `free()` calls to mirror AILang's explicit-mode RC dec-tax. Pairs
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// with examples/bench_list_sum_explicit.ailx via bench/cross_lang.py.
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//
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// The free pass walks the list after sum, freeing each cell. This is
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// genuinely O(N) work that bench_list_sum.c never paid; the rc/c
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// ratio for this fixture is therefore the honest answer to "how
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// much does RC's dec-and-free pipeline cost vs hand-C's malloc-free
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// pipeline on the same workload?".
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//
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// Note: we sum first, then free, rather than fold-with-free. This
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// matches the AILang fixture's structure: sum_list owns the chain
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// and consumes it; the dec walk happens implicitly as sum_acc
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// pattern-matches LCons and re-binds the tail to the recursive call.
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// AILang's pattern there is "consume during sum" — codegen emits
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// dec on the consumed cells as the match arm closes. The C version
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// could in principle interleave free into the sum loop too; doing it
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// in two passes is structurally cleaner and the cost is the same
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// (one O(N) walk + one O(N) walk-and-free).
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//
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// Build: clang -O2 -o list_sum_explicit_free list_sum_explicit_free.c
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// Expected stdout (one int per line):
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// 4999950000
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// 499999500000
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// 4499998500000
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#include <stdio.h>
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#include <stdlib.h>
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typedef struct cell {
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long head;
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struct cell *tail;
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} cell_t;
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static cell_t *cons_n(long n) {
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cell_t *acc = NULL;
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for (long i = n - 1; i >= 0; i--) {
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cell_t *c = (cell_t *) malloc(sizeof(cell_t));
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c->head = i;
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c->tail = acc;
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acc = c;
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}
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return acc;
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}
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static long sum_list(const cell_t *xs) {
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long acc = 0;
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while (xs) {
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acc += xs->head;
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xs = xs->tail;
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}
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return acc;
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}
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static void free_list(cell_t *xs) {
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while (xs) {
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cell_t *next = xs->tail;
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free(xs);
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xs = next;
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}
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}
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static void run_one(long n) {
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cell_t *xs = cons_n(n);
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printf("%ld\n", sum_list(xs));
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free_list(xs);
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}
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int main(void) {
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run_one(100000);
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run_one(1000000);
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run_one(3000000);
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return 0;
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}
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