#14519: Exponential runtime performance regression in GHC 8.2 + Data.Text.Lazy + Text.RE.TDFA -------------------------------------+------------------------------------- Reporter: ntc2 | Owner: tdammers Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime | Test Case: performance bug | https://github.com/ntc2/ghc-8.2.1 | -regex-lazy-text- | bug/tree/07b7bb32c6e90e8f2d2eada4b59943f37e632d53 Blocked By: | Blocking: Related Tickets: #13745, #14564 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): Actually it turns out that I must have done something wrong with my benchmarking; proper testing shows that *all* the examples that start with `^[.^]` (i.e. everything that fails on the first token) runs fast (~20 ms), while everything that matches on the first token at least runs slowly (~30,000 ms). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14519#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler