wxruby users - Jun 2008 - Background thread - entension code - switch contexts

Hi,

I am using wxRuby 1.9.7 and Ruby 1.8.6. I have built an extension in C++
and used swig to load it into Ruby interpreter, which works great. The
extension is an often long executing algorithm, and I''ve noticed that
if
I fork a new Ruby thread in button clicked event, and in this thread run
the algorithm the application freezes for the time of execution. I have
looked through the archive and found that in the wxRuby main thread I
need to use timer, but that does not work for the "algorithm thread",
I
dont know how to stop it or keep GUI responsive? Can anyone suggest what
should I do. I know about Green Threads, and possibly that interpreter
can not switch context when extension is running, so what should I do
maybe use a thread at the side of extension (in c++ code) or maybe try
to use the same mechanizm with timer as wxRuby does (but how to
implement that).


My code is simple:


require ''wx''
require ''cppapp'' #myextension

class MFrame < Wx::Frame
  STEPS = 100
  def initialize
    super(nil,-1,"Title")
    set_client_size(Wx::Size.new(300,300))
    panel = Wx::Panel.new(self)
    sizer = Wx::BoxSizer.new(Wx::VERTICAL)

    btn = Wx::Button.new(panel, -1, "Click me")
    sizer.add(btn, 0, Wx::GROW|Wx::ALL,2)

    evt_button(btn.get_id){

        Thread.abort_on_exception = true
        #that does not work
        @th = Thread.new do
          Wx::Timer.every(20) do
            Thread.pass
          end
          method1
        end

    }
    panel.set_sizer(sizer)
    sizer.fit(panel)
  end

  def method1
    alg = Cppapp::Algorithm.new
    alg.form = Cppapp::Form.new
    alg.algorithmize
  end
end

class MApp < Wx::App
  def on_init
    MFrame.new.show
    Wx::Timer.every(20) {Thread.pass}
  end
end
MApp.new.main_loop
-- 
Posted via http://www.ruby-forum.com/.

Hey Lukasz,

I looked over the code, and it looks good.  Now you said you developed the
C++ Extension yourself, so that gives you a bit more control then most.  The
problem is, Ruby''s threads are green, and if you use an extension that
doesn''t recognize that Ruby is Green Threaded, and yield control back
to it,
it''ll effectivly do as you are seeing, freezing.  With the examples
we''ve
given, we''re using Ruby''s core code, or using Sockets, with
key point
select() calls.  Ruby''s core code, and select() are specifically
programmed
to allow for Green Threads to be used.  When you use select() in Ruby,
it''s
not a "true" call to the os level select.  It''s timed to be
used within
Ruby''s Threads itself.

What you will need to do, is make your C++ Extension aware of Ruby Threads.
You will need to look at how to add rb_thread_yield() to your swig''ed
code,
to allow when an interation through your algorithim is completed, it will
call rb_thread_yield(), to allow a pass from the C/C++ Code, back to Ruby
code, so that it can do it''s iteration/processing, before giving
control
back to your C/C++ Extension.  That, unfortunatly, is the only way you will
be able to improve upon the problem you are facing.

Hope this helps,

Mario Steele

On Thu, Jun 12, 2008 at 3:00 AM, ?ukasz ?api?ski <lists at ruby-forum.com>
wrote:
> Hi,
>
> I am using wxRuby 1.9.7 and Ruby 1.8.6. I have built an extension in C++
> and used swig to load it into Ruby interpreter, which works great. The
> extension is an often long executing algorithm, and I''ve noticed
that if
> I fork a new Ruby thread in button clicked event, and in this thread run
> the algorithm the application freezes for the time of execution. I have
> looked through the archive and found that in the wxRuby main thread I
> need to use timer, but that does not work for the "algorithm
thread", I
> dont know how to stop it or keep GUI responsive? Can anyone suggest what
> should I do. I know about Green Threads, and possibly that interpreter
> can not switch context when extension is running, so what should I do
> maybe use a thread at the side of extension (in c++ code) or maybe try
> to use the same mechanizm with timer as wxRuby does (but how to
> implement that).
>
>
> My code is simple:
>
>
> require ''wx''
> require ''cppapp'' #myextension
>
> class MFrame < Wx::Frame
>  STEPS = 100
>  def initialize
>    super(nil,-1,"Title")
>    set_client_size(Wx::Size.new(300,300))
>    panel = Wx::Panel.new(self)
>    sizer = Wx::BoxSizer.new(Wx::VERTICAL)
>
>    btn = Wx::Button.new(panel, -1, "Click me")
>    sizer.add(btn, 0, Wx::GROW|Wx::ALL,2)
>
>    evt_button(btn.get_id){
>
>        Thread.abort_on_exception = true
>        #that does not work
>        @th = Thread.new do
>          Wx::Timer.every(20) do
>            Thread.pass
>          end
>          method1
>        end
>
>    }
>    panel.set_sizer(sizer)
>    sizer.fit(panel)
>  end
>
>  def method1
>    alg = Cppapp::Algorithm.new
>    alg.form = Cppapp::Form.new
>    alg.algorithmize
>  end
> end
>
> class MApp < Wx::App
>  def on_init
>    MFrame.new.show
>    Wx::Timer.every(20) {Thread.pass}
>  end
> end
> MApp.new.main_loop
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> wxruby-users mailing list
> wxruby-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/wxruby-users
>


-- 
Mario Steele
http://www.trilake.net
http://www.ruby-im.net
http://rubyforge.org/projects/wxruby/
http://rubyforge.org/projects/wxride/
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Mario Steele wrote:
> You will need to look at how to add rb_thread_yield() to your
swig''ed
> code,
> to allow when an interation through your algorithim is completed, it 
> will
> call rb_thread_yield(), to allow a pass from the C/C++ Code, back to 
> Ruby
> code, so that it can do it''s iteration/processing, before giving
control
> back to your C/C++ Extension.  That, unfortunatly, is the only way you 
> will
> be able to improve upon the problem you are facing.
> 
> Hope this helps,
> 
> Mario Steele


Thank you, I believe that is the only and good direction :). Now I will 
investigate that.

If I could use some tips of yours :)

I think I should place it somewhere here (the algorithm function)

SWIGINTERN VALUE
_wrap_Algorithm_algorithmize(int argc, VALUE *argv, VALUE self) {

  Algorithm *arg1 = (Algorithm *) 0 ;
  void *argp1 = 0 ;
  int res1 = 0 ;

  if ((argc < 0) || (argc > 0)) {
    rb_raise(rb_eArgError, "wrong # of arguments(%d for 0)",argc); 
SWIG_fail;
  }
  res1 = SWIG_ConvertPtr(self, &argp1,SWIGTYPE_p_Algorithm, 0 |  0 );
  if (!SWIG_IsOK(res1)) {
    SWIG_exception_fail(SWIG_ArgError(res1), Ruby_Format_TypeError(
"",
"Algorithm *","algorithmize", 1, self ));
  }
  arg1 = reinterpret_cast< Algorithm * >(argp1);

#HERE CREATE A THREAD FROM algorithmize function?

  (arg1)->algorithmize();
  return Qnil;
fail:
  return Qnil;
}


I still don''t know where to get the ruby thread that I should pass to

rb_thread_yield(VALUE arg, rb_thread_t th)

Should I create it or get current ruby thread in the place marked above 
in the code and then pass it to the algorithmize(rb_thread_t th) and 
then in this function



void Algorithm::algorithmize(rb_thread_t th) {

  time_t seconds;

  seconds = time (NULL);
  time_t tmp = 0;
  int nb = 0;

  //iterations
  while((tmp = time(NULL) - seconds) < 4)
  {
    if(tmp > nb)
    {
      nb++;
                        #THIS GOES IN THE ITERATION
      rb_thread_yield(some_VALUE, rh);
    }
  }
}




Kind regards,
?ukasz ?api?ski
-- 
Posted via http://www.ruby-forum.com/.

Hello again Lukasz,

On Thu, Jun 12, 2008 at 11:52 AM, ?ukasz ?api?ski <lists at
ruby-forum.com>
wrote:
> Thank you, I believe that is the only and good direction :). Now I will
> investigate that.
>
No problem.
>
> If I could use some tips of yours :)
>
> I think I should place it somewhere here (the algorithm function)
>
I''m sorry, I meant the use of rb_thread_pass(), instead of
rb_thread_yield().  rb_thread_yield() is pretty much like the internal
rb_yield(), which yields control back to Ruby, with some variable passed.
Generally meant for Blocks.  Where as rb_thread_pass() is meant to pass
control back to the Ruby Thread Scheduler, and on to the next thread in the
list of threads.

> Should I create it or get current ruby thread in the place marked above
> in the code and then pass it to the algorithmize(rb_thread_t th) and
> then in this function
>
You are partly right, again rb_thread_yield() is not the method to go with,
my apologizes, but your idea for Algorithim::algorithmize() would be the
best solution, only replace rb_thread_yield() with rb_thread_pass().  The
main thing you need to look at, is allowing Ruby''s Thread Scheduler
back
control, so that it can give processing time to other Ruby Threads.  If you
don''t do that, then all other threads will freeze till your C/C++
routine is
completed.  And that is not what you want.


> void Algorithm::algorithmize(rb_thread_t th) {
>
>  time_t seconds;
>
>  seconds = time (NULL);
>  time_t tmp = 0;
>  int nb = 0;
>
>  //iterations
>  while((tmp = time(NULL) - seconds) < 4)
>  {
>    if(tmp > nb)
>    {
>      nb++;
>                        #THIS GOES IN THE ITERATION
>      rb_thread_yield(some_VALUE, rh);
>    }
>  }
> }
>
Good luck,
Mario Steele
>
> Kind regards,
> ?ukasz ?api?ski
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> wxruby-users mailing list
> wxruby-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/wxruby-users
>


-- 
Mario Steele
http://www.trilake.net
http://www.ruby-im.net
http://rubyforge.org/projects/wxruby/
http://rubyforge.org/projects/wxride/
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Hi,

thanks for help,

Finally I have used

void rb_thread_schedule()

function which is not static and I can declare it to be extern in my C++ 
extension, what I did is


extern "C"
{
extern void
rb_thread_schedule();
}

using namespace std;

void Algorithm::algorithmize() {

  time_t seconds;

  seconds = time (NULL);
  time_t tmp = 0;
  float nb = 0;

  //iterations
  while((tmp = time(NULL) - seconds) < 5)
  {
    if(tmp > nb)
    {
      cout<<nb<<endl;
      nb = nb + 0.01;
      rb_thread_schedule();
    }
  }
}

And it works.

Thanks,
?ukasz ?api?ski


-- 
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