#5642: Deriving Generic of a big type takes a long time and lots of space
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Reporter: basvandijk | Owner: dimitris
Type: bug | Status: new
Priority: high | Milestone: 7.4.1
Component: Compiler | Version: 7.3
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Compile-time performance bug
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Changes (by simonpj):
* difficulty: => Unknown
Comment:
I think this is going to be a difficult one to solve. The underlying
problem is that the types grow non-linearly with the program size. Why?
Look at Section 2.3 of [http://research.microsoft.com/en-
us/um/people/simonpj/papers/variant-f/index.htm Scrap your type
applications].
This is a fundamental problem with System F, so it's not easy for GHC to
get around it. It shows up especially with deeply-nested sums and
products, which is exactly what is generated by the generic stuff. I'm
not sure what to do here.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5642#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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