2010/9/21 Simon Marlow :

On 19/09/2010 13:11, Stefan Wehr wrote:

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Hi all,

I'm profiling a Haskell program and now getting that the program spents 56% of its individual time in the cost centre MAIN (note the capital letters).

I searched the documentation for this cost centre, with no success. In all profiling results so far, the individual time spent in MAIN was always 0%.

The profiler constructs a tree of cost centres representing the lexical call structure of your program.  The root of this tree is the special cost centre "MAIN", which will collect any costs that are not otherwise attributed to any other cost centre.

Usually if you get lots of costs attributed to "MAIN", then you don't have any cost centres; you should either compile with -auto-all, or add explicit cost centres yourself with {-# SCC "..." #-}.

I compiled the program with -auto-all and -caf-all, but also with -threaded. The -threaded flag makes the difference, if I remove this flag, cost centre MAIN is back at 0%. The program in question uses STM and quite a lot of threads. Maybe transaction and synchronization costs are summarized under MAIN?! Any comments? Thanks, Stefan