25 Apr
2008
25 Apr
'08
4:42 a.m.
| 1) Why is the Prelude mapM so slow? It seems like running 10x slower | than mapM_ when generating only 50,000 return values is a problem. All this does seem odd. I've submitted a ticket so we don't forget it http://hackage.haskell.org/trac/ghc/ticket/2236 It appears to be some bad (possibly even non-linear) run-time system or garbage collector effect, caused by the very deep stack. Thanks for persisting with this. I'd expect mapM to be a bit slower, but not *that* much. Simon