Hi Matt,

What you said was basically what I was thinking, so we're somewhat on
the same page. As far as I understand, right now within Csound the
handling is synchronous, so when an opcode or the engine calls
csound->Message, by default if no message callback is set by a host,
the default message callback is used and that calls vfprintf to output
to stderr directly.

In MacCsound or Csound5GUI, the callback given to Csound is then used
for Message, but the asynchronous part is then handled in the host.
The opcodes call Message, the host callback adds the message to its
buffer, and the lower priority thread in the host is what does the end
printing.

I was suggesting a flag because i thought that if Csound was changed
to do the low priority thread thing inside, it might be less than
optimal if that's going on and you already have the same thing in the
host.

So, if the flag is off, the asynchronous handling via thread and
buffer is implemented by a host.  If flag is on, it gets a little
complicated, but there would have to be an extra message callback
stored somewhere.  All of the opcodes and internal code call Message,
but what would have to happen would be that Message would need to be a
function that adds to the buffer, then the low priority thread would
have to grab from the buffer and call the second stored Message
callback (either the default vfprintf one or a host provided one).
The low priority thread would also have to be started very early in
the csound compilation process to get all messages (I guess whenever
setMessageCallback is normally set, at that same step in the
compilation process).

So, take for instance you're in python. The host sets a callback to do
something like append to a text field.  With the flag, csound would
store messages in a buffer internally and the low priority thread
would call the host callback.  If that callback is slow (which it
might be with python or other scripting language with all the method
overheads involved), the it'll only slowdown the low priority thread,
not the csound main loop.

If you don't use the flag and you're in a scripting language, then you
can set a callback and do the whole threading thing in the scripting
language, but that callback, even if it's just to add to a linked
list, isn't going to be as fast as in C, and perhaps neither will the
thread in the scripting language be processing as quickly as in C.  So
it tightens up everything to do as much in C as possible I think to
let the main audio loop go as quickly as possible.

But I was thinking that the situation like csound5gui and MacCsound,
you're already handling it in an optimal way, and just adding it into
csound would only slow it down, which is why I was suggesting a flag.

Does that sound alright or is there something I'm missing that this
wouldn't work out?
steven


On 10/29/06, matt ingalls <matt@sfsound.org> wrote:
> i probably don't really understand, but
> i would assume the asynchronous handling be in the
> default message routine, which would then no be used
> if a host app registers a message callback?
> [ so no need for a commandline flag ]
>
> On Oct 29, 2006, at 2:44 AM, Steven Yi wrote:
>
> > Hi Matt,
> >
> > Thanks for the reply!  I'm beginning to think that it's pretty
> > important to have asynchronous handling for the Message callback,
> > especially when rendering in realtime.  I think I'll experiment
> > sometime with the commandline to see if implementing a threaded system
> > there will help out for blue and also in realtime CSD's.  If it does
> > indeed improve performance, would it be an issue to you or ayone else
> > here if it was put into the core and disabled by default but
> > enable-able (I've just coined a new word, I know :P ) with a flag?  It
> > seems like it would be tedious to implement for API users in non-C/C++
> > languages.
> >
> > BTW: Just as an experiment in Java, I found that the way to implement
> > a MessageCallback is to use the CsoundCallbackWrapper as in below:
> >
> >         Csound csound = new Csound();
> >         CsoundCallbackWrapper cw = new CsoundCallbackWrapper(csound) {
> >             public void MessageCallback(int attr, String msg) {
> >                 System.out.println(">>" + msg);
> >             }
> >         };
> >         cw.SetMessageCallback();
> >
> >         csound.Compile("/work/blue/sineTest.csd", "-Wdo", "dac");
> >         csound.Perform();
> >
> > Learning something every day! =)
> >
> > steven
> >
> >
> >
> >
> > On 10/29/06, matt ingalls <matt@sfsound.org> wrote:
> >>
> >>
> >> On Oct 28, 2006, at 4:12 PM, Steven Yi wrote:
> >>
> >>
> >> Do any hosts currently implement setting their own
> >>
> >> message callbacks to work in an asynchronous manner?
> >>
> >> yes - i have a circular buffer the csoundMessage callback writes to,
> >> and then a lower priority thread handles printing the buffer.
> >>
> >>
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