Hi Miller,

Idea #1 sounds quite good, except that it sounds hacky
and that performance might go down notifiable because
of thread switching. The extra amount of code necessary
to switch threads doesn't sound like too much work.

So I like idea #2 much better. The limitation of only one
DSP chain was the only good reason for implementing
multiple pd instances for Radium. If you implement #2,
that's probably good enough for Radium, and most likely
good enough for most others too. At least, it's a very
good start.

On Sun, Dec 8, 2013 at 6:53 PM, Miller Puckette <msp@ucsd.edu> wrote:
> Hi all -
>
> two idea, neither of them as general but perhaps much easier to pull off:
>
> 1.  make macros like:
> #define STATIC static __thread
>
> and rely on gcc's per-thread static storage mechanism.  This would involve
> some global search-and-replace action but wouldn't clutter the code too badly.
> The downside is it would require that each instance of libpd would have to
> run in its own thread - As Peter pointed out to me, in many situations the
> programmer can't even determine at compile time whether this would be true
> or not.
>
> I'm not sure but I think other C compilers besides gcc might support __thread
> these days.
>
> 2.  Just make the symbol table and DSP chain per-instance,  and leave the rest
> alone.  This only solves a subset of the problem (things like the search path
> would remain global) but my intuition has it that fixing these two would be
> enough so that people could practically make patches that don't interfere
> with each other.  (Making the symbol table per-instance would keep things
> like arrays, send/receives, etc., from cross-talking.)
>
> The result wouldn't be thread-safe; however, combining this with the
> __thread idea from above would probably work, and then you'd have something
> that would at least work (although perhaps slightly differently) in
> same-thread and multi-thread contexts.
>
> These are just ideas - if there's enough interest I can pull (2) off quite
> easily; (1) would be a global search-and-replace mess that would likely
> conflict with every source-code patch out there (e.g., all the patches that
> are applied for Pd extended) so I'd need a real good reason to inflict that
> one on the world.
>
> cheers
> Miller
>
> On Sun, Dec 08, 2013 at 10:12:03AM +0100, Kjetil Matheussen wrote:
>> Excellent plan.
>>
>> In my branch of libpd on Github, I've solved the Pd multiple
>> instances problem by letting the linker take care of separating
>> the global variables. However, using the linker causing various
>> problems, such as making it very difficult to load externals,
>> and it should probably also be considered a hack.
>> Your plan (the plan I didn't bother doing in my branch) is quite
>> undoubtedly the proper way to do it, and hopefully I would have time to
>> help. At least I would be helping to debug it afterwards,
>> because I would start using this system (in the Radium music editor),
>> instead of my own, to embed Pd instances.
>>
>> And an advantage to Pd itself might be that the source could be clearer when
>> variables that belongs to the instance, actually are denoted as such
>> in the text.
>>
>> There is also quite microscopic concern, which is that the added
>> amount of text could make the source more difficult to read,
>> here and there. Maybe a very short variable name for the pd instance,
>> such as "p", "pi', would be a good idea. (i.e. not "pure_data_instance").
>>
>>
>>
>> On Sat, Dec 7, 2013 at 10:20 PM, Rob Bairos <rob@derivative.ca> wrote:
>> > Sorry, most of my original post got cut off.
>> > Here's the rest (minus the list of symbols) in case its causing a problem:
>> >
>> >
>> > From my understanding, the current proposed solution is to take all statics
>> > and globals,
>> > encapsulate them in one object, and pass that object to all api calls.
>> > Peter further suggested legacy api is maintained by having them call the new
>> > api with a default instance object.
>> >
>> > I did a little bit of hunting, using objdump on the current dll, to get a
>> > rough list of all the globals and statics currently involved.
>> >
>> > Im thinking the *_class and *_sym static pointers are in fact constant, and
>> > need only one shared instance.  That would leave about 320 variables
>> > remaining.
>> > Many of these variables are constant arrays, strings, etc.
>> > And many seem to be used only as a shortcut for passing data between two
>> > functions, possibly bringing down the number further.
>> >
>> > Im toying with the idea of taking on this task if anyone's interested.
>> > I may require some tips and help from the forum, in terms of creating a
>> > branch, explanation of some statics etc.
>> >
>> > So how feasible is this? Am I on the right track?
>> > Thanks very much,
>> > Rob Bairos.
>> >
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>> >
>>
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