RE: [Caml-list] Cross-platform cpu count

[malc <av1474@comtv.ru>]

On Fri, 2 Sep 2011, David Allsopp wrote:

> malc wrote:
> > On Fri, 2 Sep 2011, Daniel B?nzli wrote:
> > 
> > > Hello,
> > >
> > > Can anybody confirm me that the following code works on cygwin :
> 
> It won't - Sys.os_type returns "Cygwin" and getconf isn't in Cygwin either - http://cygwin.com/ml/cygwin/2010-12/msg00435.html (actually, it may be now - I haven't upgraded my Cygwin in a while - but it'll be a recent addition)
> 
> > >
> > > let cpu_count () =
> > >   try match Sys.os_type with
> > >   | "Win32" -> int_of_string (Sys.getenv "NUMBER_OF_PROCESSORS")
> > >   | _ ->
> > >       let i = Unix.open_process_in "getconf _NPROCESSORS_ONLN" in
> > >       let close () = ignore (Unix.close_process_in i) in
> > >       try Scanf.fscanf i "%d" (fun n -> close (); n) with e -> close ();
> > raise e
> > >   with
> > >   | Not_found | Sys_error _ | Failure _ | Scanf.Scan_failure _
> > >   | End_of_file | Unix.Unix_error (_, _, _) -> 1
> > >
> > > Thanks,
> > >
> > 
> > http://repo.or.cz/w/apc.git/blob/55de75ccb853f5e4443fd484e5eb95e1342e72bd:
> > /ml_apc.c
> 
> The C code here uses a deprecated API call (probably for Windows NT 4 
> compatibility). If you do end up using a C stub, use GetSystemInfo 
> (http://msdn.microsoft.com/en-us/library/ms724381(v=vs.85).aspx) - it's 
> easier to call. It's used in the OCaml runtime - see byterun/win32.c. 
> Personally, even for something where it's unimportant, I'd be nervous 
> relying on an environment variable (which can be edited...)

Uhm, no, it uses native API which was never publically documented to begin
with, and the reason for that that it provides other information which is
unavailable via other means.

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