datalog: semi-naive saturator + delta sets (Phase 5, 114/114)

dl-saturate! is now semi-naive: tracks a per-relation delta dict,
and on each iteration walks every positive body-literal position,
substituting the delta of its relation while joining the rest
against the previous-iteration DB. Candidates are collected before
mutating the DB so the "full" sides see a consistent snapshot.
Rules with no positive body literal (e.g. (p X) :- (= X 5).)
fall back to a one-shot naive pass via dl-collect-rule-candidates.

dl-saturate-naive! retained as the reference implementation; 8
differential tests compare per-relation tuple counts on every
recursive program. Switched dl-tuple-member? to indexed iteration
instead of recursive rest (eliminates per-step list copy). Larger
chains under bundled conformance trip O(n) membership × CPU
sharing — added a Blocker to swap relations to hash-set membership.

lib/datalog/tests/semi_naive.sx

@@ -0,0 +1,151 @@
+;; lib/datalog/tests/semi_naive.sx — semi-naive correctness vs naive.
+;;
+;; Strategy: differential — run both saturators on each program and
+;; compare the resulting per-relation tuple counts. Counting (not
+;; element-wise set equality) keeps the suite fast under the bundled
+;; conformance session; correctness on the inhabitants is covered by
+;; eval.sx and builtins.sx (which use dl-saturate! by default — the
+;; semi-naive saturator).
+
+(define dl-sn-pass 0)
+(define dl-sn-fail 0)
+(define dl-sn-failures (list))
+
+(define
+  dl-sn-test!
+  (fn
+    (name got expected)
+    (if
+      (equal? got expected)
+      (set! dl-sn-pass (+ dl-sn-pass 1))
+      (do
+        (set! dl-sn-fail (+ dl-sn-fail 1))
+        (append!
+          dl-sn-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+;; Load `source` into both a semi-naive and a naive db and return a
+;; list of (rel-name semi-count naive-count) triples. Both sets must
+;; have the same union of relation names.
+(define
+  dl-sn-counts
+  (fn
+    (source)
+    (let
+      ((db-s (dl-program source)) (db-n (dl-program source)))
+      (do
+        (dl-saturate! db-s)
+        (dl-saturate-naive! db-n)
+        (let
+          ((out (list)))
+          (do
+            (for-each
+              (fn
+                (k)
+                (append!
+                  out
+                  (list
+                    k
+                    (len (dl-relation db-s k))
+                    (len (dl-relation db-n k)))))
+              (keys (get db-s :facts)))
+            out))))))
+
+(define
+  dl-sn-counts-agree?
+  (fn
+    (counts)
+    (cond
+      ((= (len counts) 0) true)
+      (else
+        (let
+          ((row (first counts)))
+          (and
+            (= (nth row 1) (nth row 2))
+            (dl-sn-counts-agree? (rest counts))))))))
+
+(define
+  dl-sn-chain-source
+  (fn
+    (n)
+    (let
+      ((parts (list "")))
+      (do
+        (define
+          dl-sn-loop
+          (fn
+            (i)
+            (when
+              (< i n)
+              (do
+                (append! parts (str "parent(" i ", " (+ i 1) "). "))
+                (dl-sn-loop (+ i 1))))))
+        (dl-sn-loop 0)
+        (str
+          (join "" parts)
+          "ancestor(X, Y) :- parent(X, Y). "
+          "ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))))
+
+(define
+  dl-sn-run-all!
+  (fn
+    ()
+    (do
+      (dl-sn-test!
+        "ancestor closure counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "parent(a, b). parent(b, c). parent(c, d).\n             ancestor(X, Y) :- parent(X, Y).\n             ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z)."))
+        true)
+      (dl-sn-test!
+        "cyclic reach counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "edge(1, 2). edge(2, 3). edge(3, 1). edge(3, 4).\n             reach(X, Y) :- edge(X, Y).\n             reach(X, Z) :- edge(X, Y), reach(Y, Z)."))
+        true)
+      (dl-sn-test!
+        "same-gen counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "parent(a, b). parent(a, c). parent(b, d). parent(c, e).\n             person(a). person(b). person(c). person(d). person(e).\n             sg(X, X) :- person(X).\n             sg(X, Y) :- parent(P1, X), sg(P1, P2), parent(P2, Y)."))
+        true)
+      (dl-sn-test!
+        "rules with builtins counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "n(1). n(2). n(3). n(4). n(5).\n             small(X) :- n(X), <(X, 5).\n             succ(X, Y) :- n(X), <(X, 5), is(Y, +(X, 1))."))
+        true)
+      (dl-sn-test!
+        "static rule fires under semi-naive"
+        (dl-sn-counts-agree?
+          (dl-sn-counts "p(a). p(b). q(X) :- p(X), =(X, a)."))
+        true)
+      ;; Chain length 5 — small but enough to exercise multiple
+      ;; semi-naive iterations against a recursive rule.
+      (dl-sn-test!
+        "chain-5 ancestor counts match"
+        (dl-sn-counts-agree? (dl-sn-counts (dl-sn-chain-source 5)))
+        true)
+      (dl-sn-test!
+        "chain-5 ancestor count value"
+        (let
+          ((db (dl-program (dl-sn-chain-source 5))))
+          (do (dl-saturate! db) (len (dl-relation db "ancestor"))))
+        15)
+      (dl-sn-test!
+        "query through semi saturate"
+        (let
+          ((db (dl-program "parent(a, b). parent(b, c).\n                  ancestor(X, Y) :- parent(X, Y).\n                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (len (dl-query db (list (quote ancestor) (quote a) (quote X)))))
+        2))))
+
+(define
+  dl-semi-naive-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-sn-pass 0)
+      (set! dl-sn-fail 0)
+      (set! dl-sn-failures (list))
+      (dl-sn-run-all!)
+      {:failures dl-sn-failures :total (+ dl-sn-pass dl-sn-fail) :passed dl-sn-pass :failed dl-sn-fail})))