#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: 11362 | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, Wiki Page: | Phab:D1396, Phab:D1457, Phab:D1468, DeterministicBuilds | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Comment (by Bartosz Nitka <niteria@…>): In [changeset:"ad4392c142696d5092533480a82ed65322e9d413/ghc" ad4392c/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="ad4392c142696d5092533480a82ed65322e9d413" Kill non-deterministic foldUFM in TrieMap and TcAppMap Summary: foldUFM introduces unnecessary non-determinism that actually leads to different generated code as explained in Note [TrieMap determinism]. As we're switching from UniqFM to UniqDFM here you might be concerned about performance. There's nothing that ./validate detects. nofib reports no change in Compile Allocations, but Compile Time got better on some tests and worse on some, yielding this summary: -1 s.d. ----- -3.8% +1 s.d. ----- +5.4% Average ----- +0.7% This is not a fair comparison as the order of Uniques changes what GHC is actually doing. One benefit from making this deterministic is also that it will make the performance results more stable. Full nofib results: P108 Test Plan: ./validate, nofib Reviewers: goldfire, simonpj, simonmar, austin, bgamari Reviewed By: simonpj Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2169 GHC Trac Issues: #4012 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:158> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler