#2762: Excessive heap usage
---------------------------------+------------------------------------------
Reporter: igloo | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.10.2
Component: Compiler | Version: 6.11
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Changes (by simonpj):
* cc: [EMAIL PROTECTED] (added)
Comment:
What we need here is a decent arity analysis, which Max is thinking about.
We have
{{{
f = \d. let f1 = f d in
\y. ...f1...
}}}
The leak comes from a shared partial application of `f`:
{{{
let t = f d in (t e1, t e2)
or
map (f d) es
}}}
This is readily fixed. `f` ''looks'' as if it has arity 1, but a simple
fixpoint argument shows that it really has arity 2. When we see that, we
see that we can eta-expand it to get
{{{
f = \d.\x. let f1 = f d in ...f1 d...
}}}
Now we can inline `f1`, and all is good.
I had not previously realised that this arity analysis stuff could fix
space leaks.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2762#comment:2>
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