id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
4856,Performance regression in the type checker regression for GADTs and type families,chak,,"The GHC 7.0.2 RC1 shows poor performance when compiling `Data.Array.Accelerate`.  In particular, to type check a particular module, GHC 7.02 takes several minutes, while GHC's resident memory grows to 350MB.  In contrast, GHC 6.12.3 compiles the same module in a few seconds.

How to reproduce the problem:

 0. Download the latest version of `Data.Array.Accelerate` with darcs from [http://code.haskell.org/accelerate/]
 1. Change directory to the new `accelerate` darcs repo.
 2. Invoke GHCi as `ghci -Iinclude`.
 3. Issue the GHCi command: `:l Data/Array/Accelerate/Smart.hs`

You will notice that `Data.Arra.Accelerate.Array.Sugar`, which is heavy in type classes and type families, already requires a noticeable time to compile — this is already a performance regression from 6.12.3.  The module `Data.Array.Accelerate.Smart` requires an even much longer time to compile.",bug,closed,normal,7.2.1,Compiler (Type checker),7.0.1,fixed,,dimitris@… verdelyi@…,Unknown/Multiple,Unknown/Multiple,Compile-time performance bug,,,,,