From 3f906d03262150892e2297e621bfc56e425ef142 Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Mon, 6 Jul 2026 10:32:34 +0300 Subject: Close verification-coverage gaps; harness finds two more bugs Extends the verification harness from sorts-only to the whole repo, and in doing so surfaces two further latent bugs (on top of the earlier hash-shift one): Bugs found and fixed: - queue/elementarypriority.go: max() seeded at the zero value, so an all-negative queue reported a phantom max of 0 and DeleteMax returned/removed the wrong element. Caught by the new queue permutation property (testing/quick generates negatives; the old test data never did). Seed from a[0] instead. - sort/sleep.go: result built on NewArrayList(len(a)) -- a slice of that LENGTH (len(a) zeros) -- then appended to, yielding double-length output with leading zeros. The old .Sorted()-only test passed because zeros-then-ascending is sorted. Caught by the new Sleep permutation check. Build from an empty slice. Coverage added: - queue/property_test.go: ordering + permutation (completeness) for both queues. - TestSleepSort now also checks permutation, not just Sorted(). - docs/verification.md: paper proofs for all search/set structures (Elementary, Hash, BST, red-black BST invariants, GoMap) and both priority queues. - formal/tla/ParallelSort.tla: exhaustive fork/join model of ParallelMerge/ ParallelQuick -- disjoint write-ranges (no data race) + termination. Wired into make verify-model. - formal/selection.go: second Gobra proof (memory safety + sortedness). Wired into make verify-formal. - docs/case-study-bugs-found.md: extensive write-up of all three bugs, how each was caught, why the old tests missed it, and the fix (supersedes the earlier single-bug case study). Co-Authored-By: Claude Opus 4.8 --- formal/tla/ParallelSort.cfg | 13 +++++++++++++ 1 file changed, 13 insertions(+) create mode 100644 formal/tla/ParallelSort.cfg (limited to 'formal/tla/ParallelSort.cfg') diff --git a/formal/tla/ParallelSort.cfg b/formal/tla/ParallelSort.cfg new file mode 100644 index 0000000..b60c298 --- /dev/null +++ b/formal/tla/ParallelSort.cfg @@ -0,0 +1,13 @@ +\* TLC configuration for the ParallelSort fork/join model. +\* N=4, Threshold=1 gives a full recursion tree of 7 nodes (root -> 2 -> 4 +\* leaves), enough to exercise siblings, cousins, and multi-level joins. Integer +\* constants can be assigned directly in a .cfg. +CONSTANT N = 4 +CONSTANT Threshold = 1 + +SPECIFICATION Spec + +INVARIANT TypeOK +INVARIANT NoDataRace + +PROPERTY Terminates -- cgit v1.2.3