ghc_rts_options (defalting RTS flags)
marlowsd at gmail.com
Wed Sep 15 06:30:38 EDT 2010
On 14/09/2010 02:09, Thomas DuBuisson wrote:
> A recent SO question  led me to do a quick test on hard-coding RTS
> options as suggested in the manual rts-hooks section .
> 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.
> $ 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.
> $ time ./hashPar 10MB 10MB 10MB 10MB
> real 0m2.411s
> $ time ./hashPar 10MB 10MB 10MB 10MB +RTS -N
> real 0m1.690s
>  http://stackoverflow.com/questions/3704430/why-do-you-have-to-use-both-a-compiler-flag-and-a-run-time-flag-to-get-multicore
>  http://haskell.org/ghc/docs/6.12.2/html/users_guide/runtime-control.html#rts-hooks
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