[PD] Any problems else/blocksize changing subpatch blocking during dsp?

[Christof Ressi]

Just because it doesn't crash in your specific use case doesn't mean it isn't dangerous...

> At least, for my usage case, having a subpatch fixed to overlap 2 of
> the parent, I can't crash it either.  I mean, I really thrashed it.
> It takes a lot of time when it's allocating signals up to 2^22---but
> did not crash, resumed.  I put the block size on a power of 2
> quantized vertical slider and slung it around.  There's not much
> latency in changing them in the low blocksizes up to 131,072.  Not
> bad.
>
>
>
> On Fri, Jan 17, 2020 at 3:54 AM Christof Ressi <christof.ressi at gmx.at> wrote:
> >
> > > Or a *great* idea
> >
> > Certainly not. As I've said, it's possible to crash Pd in various ways.
> >
> > Christof
> >
> > > Gesendet: Freitag, 17. Januar 2020 um 07:36 Uhr
> > > Von: "Charles Z Henry" <czhenry at gmail.com>
> > > An: Pd-List <pd-list at lists.iem.at>
> > > Betreff: Re: [PD] Any problems else/blocksize changing subpatch blocking during dsp?
> > >
> > > On Thu, Jan 16, 2020 at 1:03 PM Christof Ressi <christof.ressi at gmx.at> wrote:
> > > >
> > > > it's certainly not a good idea to (possibly) modify the DSP graph while it's being built.
> > >
> > > Or a *great* idea
> > >
> > > >As I said, the external should use a clock to schedule the message for the next tick.
> > >
> > > Here's what seems possible:
> > > The canvas "dsp" method gets called on toplevel canvases.  It adds all
> > > the objects in the canvas with "dsp" methods to an unsorted list.
> > > Then, in ugen_done_graph, the main work of setting up the dspcontext
> > > struct from block~/switch~ happens.  It allocates all the signals, and
> > > ugen_doit puts each chain of objects in a queue to have their "dsp"
> > > methods run.  Then it finally reaches a sub-patch (a canvas object),
> > > and its "dsp" method gets called.
> > >
> > > The outcome depends on which runs first--the blocksize~ "dsp" method
> > > or the sub-patch canvas "dsp" method.  Sub-patch blocksizes could
> > > still be set, during graph generation, because the block~ parameters
> > > aren't even relevant until the sub-patch "dsp" method.
> > >
> > > With no signal inlets and no outlets, there's nothing there to force
> > > it to come before/after the sub-patch "dsp" method.
> > >
> > > If blocksize~ had a signal inlet, you could connect it to a subpatch
> > > output and be guaranteed that the sub-patch "dsp" method will be
> > > called before the blocksize~ "dsp"
> > >
> > > And vice versa (the interesting case): if blocksize~ has a signal
> > > outlet connected to some sub-patch inlet, then it's possible to set
> > > the sub-patch block~/switch~ parameters during the graph generation,
> > > right before they are to be used.
> > > But.... I still have questions.  Will the block~ "set" method trigger
> > > the dsp graph to be rebuilt, at some point when it's already trying to
> > > build the graph?  What would happen if it did?
> > >
> > > > > Gesendet: Donnerstag, 16. Januar 2020 um 19:07 Uhr
> > > > > Von: "Charles Z Henry" <czhenry at gmail.com>
> > > > > An: Pd-List <pd-list at lists.iem.at>
> > > > > Betreff: Re: [PD] Any problems else/blocksize changing subpatch blocking during dsp?
> > > > >
> > > > > On Thu, Jan 16, 2020 at 10:03 AM Christof Ressi <christof.ressi at gmx.at> wrote:
> > > > > >
> > > > > > I also think that messaging an outlet in the "dsp" method is not a good idea and it's better to use a clock with delay 0. The user might take the output of [blocksize~] and accidentally do something which interferes with DSP graph generation, e.g. by resizing an array, creating/deleting objects, etc.
> > > > > >
> > > > > > Christof
> > > > >
> > > > > Yes it *could*, but I'm unclear on the timing.  I've read and
> > > > > consulted the d_ugen.c code recently but .  The block parameters are
> > > > > derived from block/switch and coded into the dspcontext struct which
> > > > > gets generated for each canvas.  The parameters have to be known
> > > > > before "dsp" gets called in the current canvas (which would trigger
> > > > > the "blocksize~" output), but is the sub-patch dspcontext already
> > > > > built?  I'll try to follow up later today and try to answer it
> > > > >
> > > > > That ambiguity could be resolved by looking at the "bang~" code.  I
> > > > > just think it's an interesting question what is possible to happen as
> > > > > it is currently written
> > > > >
> > > > > bang~ sends properly timed messages by using:
> > > > > t_clock *x_clock;  //in the data structure
> > > > >
> > > > > x->x_clock = clock_new(x, (t_method)bang_tilde_tick); // in the "new" method
> > > > >
> > > > > static void bang_tilde_tick(t_bang *x)  // added "tick" method
> > > > > { outlet_bang(x->x_obj.ob_outlet); }
> > > > >
> > > > > and
> > > > > clock_delay(x->x_clock, 0);  // in the "perform" routine
> > > > >
> > > > > Chuck
> > > > >
> > > > >
> > > > >
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