#9073: small SPECIALIZE INLINE program taking gigabytes of memory to compile -------------------------+------------------------------------------------- Reporter: dagit | Owner: Type: bug | Status: new Priority: | Milestone: normal | Version: 7.8.2 Component: | Operating System: Unknown/Multiple Compiler | Type of failure: Compile-time performance bug Keywords: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- I have a small program that is taking 1+ GB of memory to compile. I've distilled the troublesome input down to the following: {{{ {-# LANGUAGE BangPatterns #-} import Data.Vector knot :: Vector Double -> Int -> Double knot vs k = vs ! idx0 where !idx0 = abs k `mod` 16 {-# SPECIALIZE INLINE knot :: Vector Double -> Int -> Double #-} noise :: Vector Double -> Int -> Double noise vs k = knot vs k + knot vs k + knot vs k + knot vs k + knot vs k + knot vs k + knot vs k + knot vs k }}} Compiled with `ghc -fprof-auto -prof -O2 -Wall`. As far as I can tell, prof-auto, prof, and optimizations of at least -O1 are required to trigger it. I'm using ghc-7.8.2 64bit for Windows. vector is version 0.10.9.1 (currently the latest on hackage). Same code worked fine on ghc 7.6.2. Also worth noting: Even though the `SPECIALIZE` isn't needed, if you remove the `SPECIALIZE` or the `INLINE` the problem goes away. If you remove even one of the duplicated calls to `knot vs k` in the body of `noise` then the amount of memory required drops dramatically. Add more to increase the requirements. I've been able to push it up around 10 GB, but I don't have enough memory to test beyond that! Thanks! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9073 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler