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 --- Makefile | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'Makefile') diff --git a/Makefile b/Makefile index 8632e8c..3433264 100644 --- a/Makefile +++ b/Makefile @@ -16,15 +16,19 @@ verify: # (a model of sort/sleep.go, not the Go code itself). See formal/tla/README.md. verify-model: java -cp $(HOME)/tools/tlaplus/tla2tools.jar tlc2.TLC -workers auto \ - -metadir /tmp/tlc-algorithms \ + -metadir /tmp/tlc-sleepsort \ -config formal/tla/SleepSort.cfg formal/tla/SleepSort.tla + java -cp $(HOME)/tools/tlaplus/tla2tools.jar tlc2.TLC -workers auto \ + -metadir /tmp/tlc-parallelsort \ + -config formal/tla/ParallelSort.cfg formal/tla/ParallelSort.tla # verify-formal: machine-checked deductive proof of a monomorphized insertion # sort with Gobra (Go verifier, Viper+Z3 backend), run from its container image. # See formal/README.md. verify-formal: podman run --rm -v $(PWD)/formal:/gobra/formal:z \ - ghcr.io/viperproject/gobra:latest -i /gobra/formal/insertion.go + ghcr.io/viperproject/gobra:latest \ + -i /gobra/formal/insertion.go /gobra/formal/selection.go bench: go test -run=xxx -bench=. ./... | tee bench.out sortbench: -- cgit v1.2.3