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`table-2` wraps a 2-arg (input, output) relation. On a ground input walk, looks up the (string-encoded) cache key; on miss, runs the relation, drains the answer stream, extracts walk*-output values from each subst, stores them, and replays. On hit, replays the cached values directly — no recomputation. Cache lifetime: a single global mk-tab-cache (mutated via set!). mk-tab-clear! resets between independent queries. Canonical demo: tabled fib(25) = 75025 in ~5 seconds; the same naive fib-o times out at 60s. Memoization collapses the exponential redundant recomputation in the binary recursion. Limitations (deferred to future SLG work): cyclic recursive calls with the same ground key still diverge — naive memoization populates the cache only AFTER computation completes, so a recursive call inside its own computation can't see the in-progress entry. The brief's "tabled patho on cyclic graphs" use case requires producer/consumer scheduling and is left for a future iteration. 12 new tests, fib(0..20) + ground-term predicate + cache-replay verification. 638/638 cumulative.
61 lines
1.6 KiB
Plaintext
61 lines
1.6 KiB
Plaintext
;; lib/minikanren/tests/tabling.sx — Phase 7 piece A: naive memoization.
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;; --- Fibonacci canary: tabled vs naive --
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(define
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tab-fib-o
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(table-2
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"fib"
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(fn
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(n result)
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(conde
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((== n 0) (== result 0))
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((== n 1) (== result 1))
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((fresh (n-1 n-2 r-1 r-2) (lto-i 1 n) (minuso-i n 1 n-1) (minuso-i n 2 n-2) (tab-fib-o n-1 r-1) (tab-fib-o n-2 r-2) (pluso-i r-1 r-2 result)))))))
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(mk-tab-clear!)
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(mk-test "tab-fib-zero" (run* q (tab-fib-o 0 q)) (list 0))
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(mk-tab-clear!)
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(mk-test "tab-fib-one" (run* q (tab-fib-o 1 q)) (list 1))
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(mk-tab-clear!)
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(mk-test "tab-fib-two" (run* q (tab-fib-o 2 q)) (list 1))
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(mk-tab-clear!)
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(mk-test "tab-fib-five" (run* q (tab-fib-o 5 q)) (list 5))
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(mk-tab-clear!)
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(mk-test "tab-fib-ten" (run* q (tab-fib-o 10 q)) (list 55))
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(mk-tab-clear!)
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(mk-test
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"tab-fib-twenty"
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(run* q (tab-fib-o 20 q))
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(list 6765))
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;; --- ground-term predicate ---
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(mk-test "tab-ground-term-num" (mk-tab-ground-term? 5) true)
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(mk-test "tab-ground-term-str" (mk-tab-ground-term? "hi") true)
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(mk-test
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"tab-ground-term-list"
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(mk-tab-ground-term? (list 1 2 3))
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true)
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(mk-test "tab-ground-term-var" (mk-tab-ground-term? (mk-var "x")) false)
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(mk-test
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"tab-ground-term-nested"
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(mk-tab-ground-term?
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(list 1 (list 2 (mk-var "y")) 3))
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false)
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;; --- caching reduces work — count cache hits via repeated query ---
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(mk-test
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"tab-cache-replay"
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(begin
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(mk-tab-clear!)
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(let
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((first (run* q (tab-fib-o 10 q)))
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(second (run* q (tab-fib-o 10 q))))
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(and (= first (list 55)) (= second (list 55)))))
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true)
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(mk-tests-run!)
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