ghc_rts_options (defalting RTS flags)

[Simon Marlow]

On 14/09/2010 02:09, Thomas DuBuisson wrote:
> All,
>
> A recent SO question [1] led me to do a quick test on hard-coding RTS
> options as suggested in the manual rts-hooks section [2].
> Unfortunately the timing tests indicate "ghc_rts_opts" isn't being
> used; tests with flags besides -N (ex: "-H1024m") also show the
> ghc_rts_opts being ignored.  Can someone shed light on what's
> happening?  A grep of ghc source shows no users of ghc_rts_opts,
> though that isn't definitive.
>
> Cheers,
> Thomas
>
> --------
> $ cat rts-opts.h
> char *ghc_rts_opts = "-N";
>
> $ ghc --make -O2 -threaded hashPar.hs rts-opts.h  -fforce-recomp
> [1 of 1] Compiling Main             ( hashPar.hs, hashPar.o )
> Linking hashPar ...

Did you really mean rts-opts.h here?  I think it would probably work 
better if you put the declaration in a .c file.

Cheers,
	Simon




> $ time ./hashPar 10MB 10MB 10MB 10MB
> ["10MB","10MB","10MB"]
>
> real    0m2.411s
>
> $ time ./hashPar 10MB 10MB 10MB 10MB +RTS -N
> ["10MB","10MB","10MB"]
>
> real    0m1.690s
> ----------
>
> [1] http://stackoverflow.com/questions/3704430/why-do-you-have-to-use-both-a-compiler-flag-and-a-run-time-flag-to-get-multicore
> [2] http://haskell.org/ghc/docs/6.12.2/html/users_guide/runtime-control.html#rts-hooks
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