Hello all! I'm using Alex/Happy to generate a parser for PHP. This is my first go at using a parser generator instead of parser combinators and it's been going pretty smoothly so far, but I've hit a snag. Compiling the happy-generated parser is excruciatingly slow -- 20+ minutes with -O0 -- which messes up the typically very fast feedback loop haskell+ghci allows. Running the code is great; my quickcheck test suite is very fast. But compiling and loading into ghci are so slow that iterating on the project further is not practical until I can figure out how to speed it up. Are there any folklore techniques for dealing with this problem, or any resources about how to profile/debug slow compilation? I'm on macos using Stack with lts-13.21, which includes happy-1.19.10. I tried the ideas in this known issue: https://github.com/simonmar/happy/issues/109. I also tried downgrading to lts-6.35 (the most recent with GHC 7.*), all with similar results. I imagine some of this slowdown is inevitable because of the grammar's size; it has ~275 nonterminals and the generated `Parser.hs` module is 3.8MB. Usually for a problem like this I'd break the module up into smaller pieces that won't change as often, but in this case it's an opaque monolith generated by happy. I also see that the generated code doesn't have type signatures on all top level functions. Here's the relevant output from GHC with -v2 enabled: ``` *** Parser [PHP.Parse.Parser]: !!! Parser [PHP.Parse.Parser]: finished in 1980.24 milliseconds, allocated 3155.733 megabytes *** Renamer/typechecker [PHP.Parse.Parser]: !!! Renamer/typechecker [PHP.Parse.Parser]: finished in 243923.86 milliseconds, allocated 178189.005 megabytes *** Desugar [PHP.Parse.Parser]: Result size of Desugar (before optimization) = {terms: 1,346,664, types: 672,082,252, coercions: 789, joins: 0/9,651} Result size of Desugar (after optimization) = {terms: 834,353, types: 285,053,589, coercions: 246,053, joins: 235/735} !!! Desugar [PHP.Parse.Parser]: finished in 103983.68 milliseconds, allocated 17597.213 megabytes *** Simplifier [PHP.Parse.Parser]: Result size of Simplifier iteration=1 = {terms: 1,059,012, types: 69,942,882, coercions: 1,934,739, joins: 235/1,935} Result size of Simplifier iteration=2 = {terms: 815,760, types: 64,805,160, coercions: 1,368,873, joins: 233/1,929} Result size of Simplifier = {terms: 776,400, types: 64,474,214, coercions: 1,297,320, joins: 233/1,929} !!! Simplifier [PHP.Parse.Parser]: finished in 197842.50 milliseconds, allocated 116983.797 megabytes *** CoreTidy [PHP.Parse.Parser]: Result size of Tidy Core = {terms: 776,400, types: 64,474,214, coercions: 1,297,320, joins: 233/1,929} !!! CoreTidy [PHP.Parse.Parser]: finished in 97776.92 milliseconds, allocated 11254.968 megabytes *** CorePrep [PHP.Parse.Parser]: Result size of CorePrep = {terms: 795,714, types: 66,237,082, coercions: 1,297,320, joins: 233/4,234} !!! CorePrep [PHP.Parse.Parser]: finished in 7911.78 milliseconds, allocated 2564.067 megabytes *** Stg2Stg: *** CodeGen [PHP.Parse.Parser]: !!! CodeGen [PHP.Parse.Parser]: finished in 7048.73 milliseconds, allocated 6407.563 megabytes *** Assembler: *** CorePrep [PHP.Parse.Parser]: Result size of CorePrep = {terms: 795,714, types: 66,237,082, coercions: 1,297,320, joins: 233/4,234} !!! CorePrep [PHP.Parse.Parser]: finished in 3069.67 milliseconds, allocated 2564.018 megabytes *** Stg2Stg: *** CodeGen [PHP.Parse.Parser]: !!! CodeGen [PHP.Parse.Parser]: finished in 5970.62 milliseconds, allocated 6634.422 megabytes *** Assembler: *** Deleting temp files: Warning: deleting non-existent /var/folders/td/sxyy9wl919740vddr49g8nth0000gn/T/ghc1272_0/ghc_70.s Warning: deleting non-existent /var/folders/td/sxyy9wl919740vddr49g8nth0000gn/T/ghc1272_0/ghc_72.c Warning: deleting non-existent /var/folders/td/sxyy9wl919740vddr49g8nth0000gn/T/ghc1272_0/ghc_74.c ``` -- Nathan Bloomfield Systems Analyst, Team Neutron Automattic, Inc.