Re: Parallel execution on SGI with GNAT

["Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org>]

This is just a guess since I'm not familiar with your platform, but it may
help you to figure out what is going on. Typically, an Ada compiler riding
on top of a workstation OS will map Ada tasks to OS threads. The compiler
will use whatever OS calls you have to create, schedule, rendesvous and
terminate tasks. If your OS does not schedule threads on multiple CPUs, but
schedules processes on multiple CPUs, then you have to adopt a different
strategy by building your system as independent programs that can be run as
processes & then use whatever you have for inter-process communication.
(TCP/IP is a common way to go for this.) Its possible that your OS can be
configured to run threads on multiple processors, so you might look into the
OS documentation and see how this might be done. Perhaps you'll get an
answer from someone more familiar with your particular configuration.

It would be great to have tasks scheduled on multiple processors because
then you've got all the facilities you need to make optimum use of the
processors entirely from within the language. However, there is usually a
non-trivial penalty for scheduling on multiple processors in the way of
inter-process communication, which is why it may not be done.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com
Web:      http://www.mcondic.com/


"Jay Fantini" <jay.fantini@dfrc.nasa.gov> wrote in message
news:3BDDD7EC.EC896675@dfrc.nasa.gov...
>


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> Ada experts,
>
> Maybe you can help me: I am trying to get the following program to execute
> on a 6-CPU SGI ONYX-2 R12000 based system. The system is running IRIX 6.5
> and I am using GNAT Ada-95 version 3.11p for SGI. The program does compile
> and run but it only uses 1 CPU and I would like for it to execute on 3
CPUs.
> This program is a prototype for a much larger program.
>
> Do I need to set an environment variable or am I using the wrong Ada-95
> construct? Is there a PRAGMA I should use? Please post all answers to this
NG.
>
> TIA,
>
> -Jay
>
> -- ******************************************************************
>
> with text_io;
> with integer_text_io;
> with tems_floating_point_std;
> with floating_point_math_lib;
> with fp_display;
> with higher_functions;
>         with wexzal;
>
> use  tems_floating_point_std;
> use  floating_point_math_lib;
> use  higher_functions;
>         use  wexzal;
>
> procedure hog is
>
>         task type wzlsum(upper_limit: integer);
>         task body wzlsum is
>         x   :floating_point;
>         s   :floating_point;
>         begin
>         for i in 1..upper_limit loop
>           x:=floating_point(i);
>           s:=s+1.0/(x*wzl(x));
>           end loop;
>         text_io.put("Sum for n=");
>         integer_text_io.put(upper_limit);
>         text_io.put(" is S=");
>         fp_display.prt(s);
>         text_io.new_line;
>         end wzlsum;
>
>         cpu_hog_5    :wzlsum(5000000);  -- Do big calculation in parallel
>         cpu_hog_4    :wzlsum(4000000);
>         cpu_hog_3    :wzlsum(3000000);
>
> begin
>         text_io.put_line("Program HOG is done!");
> end hog;
>