#15938: Hadrian's recompilation check is extremely slow -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.8.1 Component: Build System | Version: 8.6.2 (Hadrian) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by snowleopard): I think I know a way to reduce the number of file pattern matchings in Hadrian. Currently we generate build rules for each build context and there are hundreds of contexts, e.g. see generation of `Rules.Compile.compilePackage`: https://github.com/ghc/ghc/blob/master/hadrian/src/Rules.hs#L108 Instead, we should generate just one build rule per logical target and parse various context parameters from the path, as implemented in `libraryRules`: https://github.com/ghc/ghc/blob/master/hadrian/src/Rules/Library.hs#L22 We need to rewrite all build rules in the same manner. This will essentially replace hundred-long linear chains of file pattern matchings with a single matching and subsequent parsing. This is an obvious optimisation, but requires a good understanding of Hadrian internals. I am happy to volunteer to implement this, but I'm unlikely to find time until the end of teaching term in the university (end of December). If anyone has a chance to do this earlier, please go ahead, I can review a patch. P.S.: I still have no idea where the long pauses after `Ctrl-C`-ing come from. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15938#comment:24 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler