Dear Ashish,
thanks for the report; these issues are fixed in the latest
commit on https://gitorious.org/parmap (bfdf714)
Let me know if you find any more issues
All the best
--Roberto
On Wed, Aug 17, 2011 at 03:25:53PM -0400, Ashish Agarwal wrote:
> Thanks. This is very exciting. I tried a simple test but get an error:
>
> # #require "extlib";;
> # #require "parmap";;
> # Parmap.parfold (+) (List.of_enum (1 -- 1000)) 0 ~ncores:1;;
> Signal -10
>
> The function List.of_enum is from Batteries. I use it just to create a long
> list of integers.
>
> Also, you need to add extlib to the META file.
>
>
>
> On Wed, Aug 17, 2011 at 1:10 PM, Roberto Di Cosmo <[email protected]> wrote:
>
> Dear all,
> a few lines to announce the availability of a minimalistic library
> which
> can be useful to exploit your multicore processor with minimal
> modifications to
> your OCaml programs.
>
> In a nutshell
> -------------
>
> If you want to use your many cores to accelerate an operation which
> happens
> to
> be a map, fold or map/fold (map-reduce), just use Parmap's parmap, parfold
> and
> parmapfold primitives in place of the standard List.map and friends, and
> specify
> the number of subprocesses to use by the optional parameter ncores.
>
> For example, in the classical Mandelbrot example present in the example
> directory,
> the line
>
> Parmap.parmap pixel tasks ~ncores:i
>
> allows to spawn i separate processes, each working on 1/ith of the list
> tasks.
>
> Rationale
> ---------
>
> The principle of Parmap is very simple: when you call one of the three
> available
> primitives, map, fold, and mapfold , your OCaml sequential program forks
> in n
> subprocesses (you choose the n), and each subprocess performs the
> computation on
> the 1/n of the data, returing the results through a shared memory area
> to the
> parent process, that resumes execution once all the children have
> terminated,
> and the data has been recollected.
>
> This means that you *must* run your program on a *single* multicore
> machine.
> Repeat after us: Parmap is not meant to run on a cluster, see one of the
> many
> available (re)implementations of the map-reduce schema for that.
>
> By forking the parent process on a sigle machine, the children get
> access, for
> free, to all the data structures already built, even the imperative ones,
> and as
> far as your computation inside the map/fold does not produce side
> effects
> that
> need to be preserved, the final result will be the same as
> performing the
> sequential operation, the only difference is that you might get it faster.
>
> Of course, if you happen to have open channels, or files, or other
> connections
> that should only be used by the parent process, your program may behave
> in a
> very wierd way: as an example, *do not* open a graphic window before
> calling a
> Parmap primitive, and *do not* use this library if your program
> is
> multi-threaded!
>
> The OCaml code is quite simple and does not rely on any external C
> library: all
> the magic is done by your operating system's fork and memory mapping
> mechanisms.
> One could gain some speed by implementing a marshal/unmarshal operation
> directly
> on bigarrays, but we did not do this yet.
>
>
> How to get it
> -------------
>
> Project home: https://gitorious.org/parmap
>
> To compile and install:
>
> git clone git://gitorious.org/parmap/parmap.git
> make
> make install
>
> Enjoy
>
> -- Marco Danelutto and Roberto Di Cosmo
>
> P.S.: special thanks to Pierre Chambart for useful discussions on this
> code
>
>
>
>
>
>
> --
> Caml-list mailing list. Subscription management and archives:
> https://sympa-roc.inria.fr/wws/info/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>
>
>
--
--Roberto Di Cosmo
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