[PD] poly-musings again (and dispatching anything)

[Krzysztof Czaja]

hi,

after rereading my discussion with pix, I think there are few
points I must clear up.

1. My `notsocute' example, patched up in haste, was meant to
illustrate my general doubts, and not to be used as a nqpoly~
replacement.  On the other hand, any Pd-instrument designer
would welcome a simple access to poly~'s functionality.

2. I was wrong, arguing that an addition of a request to return
a single voice to the free voices pool of PureData's poly would
cause an incompatibility with max.  Even if we seriously cared
for such compatibility, `clear' message to poly is PureData's
extra addition to max-poly, which has only `stop' message.

But anyway I was right about simplicity of such addition.  The
proof is in x_midi.c.diff attachment, which adds a float argument
to `clear' message.  If this argument's value $n$ is in the range
[1..<number-of-voices>] then voice$_n$ is returned to the pool.
In this version an argumentless `clear' works as it used to.

The question remains, if this simple addition does not introduce
unnecessary ambiguity to the meaning of poly.  Currently stopping
a voice means stopping the oldest voice playing a note of
a specified pitch, if there is any such voice.  Stopping a voice
number n is something conceptually different.  Maybe it is better
to add a separate object class `pool'?  OK, there could be an
extern...

#if 0 // this is hackery
3. ... or, if none of the above is available, the remaining
technique would be to cheat existing poly, forcing it to store
noteons with pitch always equal to voice number -- as I did in
notsocute.pd, and which is a very inefficient way of doing
something pretty simple.  This trickery is factored out into the
attached abstraction `pooly.pd'.  The interface of poly remains
in pooly (with quite the same functionality), and there are two
extensions for handling the voice pool: a `bang' message to choose
a voice (in stealing mode or not), and a `clear <n>' message to
return voice n to the pool.  But beware, this abstraction plays
nasty tricks...
#endif

4. Of course the `pitch' input to poly may have any meaning, not
necessarily directly interpreted as a single parameter of a note,
but instead, for example, mapped to a parameter vector, or to any
other mechanism of generating parameter values.  A user of poly
should think rather of playing/stopping a note of some arbitrarily
choosen cathegory, which can be pitch or anything else.

5. One thing that is really troublesome in designing poly~-alike
abstraction is a dispatching scheme, since there is no `forward'
object class in Pd.  We need to feed the choosen voice with
parameters.  This voice's number is a variable.  Since, of course,
it is impossible to [route] into as many destinations as we wish,
the only way is to use global send/receive.  But if we wanted to
choose send's destination dynamically, we are stuck with a message
box, and the number of parameters must be kept constant -- we
cannot dispatch anything.  If, on the other hand, we need variable
number of parameters, then they will have to be sent to all voices,
preceded by another message opening a spigot in the voice being
current destination (one can make variations of this theme, like
passing a message through a chain of destinations, until it is
spigoted into the proper one).  This is clumsy, unreliable and
highly inefficient.

Whoever knows of any other way (using max/forward excluded),
please give me a clue.

Krzysztof
-------------- next part --------------
--- x_midi.c~	Sun May 20 05:50:52 2001
+++ x_midi.c	Mon Oct  1 16:04:05 2001
@@ -1173,11 +1173,18 @@
     }
 }
 
-static void poly_clear(t_poly *x)
+static void poly_clear(t_poly *x, t_floatarg ndx)
 {
-    int i;
+    int i = ndx;
     t_voice *v;
-    for (v = x->x_vec, i = x->x_n; i--; v++) v->v_used = v->v_serial = 0;
+    if (i--) {
+	if (i >= 0 && i < x->x_n) {
+	    x->x_vec[i].v_used = 0;
+	    x->x_vec[i].v_serial = x->x_serial++;
+	}
+    }
+    else
+	for (v = x->x_vec, i = x->x_n; i--; v++) v->v_used = v->v_serial = 0;
 }
 
 static void poly_free(t_poly *x)
@@ -1192,7 +1199,7 @@
     	sizeof(t_poly), 0, A_DEFFLOAT, A_DEFFLOAT, 0);
     class_addfloat(poly_class, poly_float);
     class_addmethod(poly_class, (t_method)poly_stop, gensym("stop"), 0);
-    class_addmethod(poly_class, (t_method)poly_clear, gensym("clear"), 0);
+    class_addmethod(poly_class, (t_method)poly_clear, gensym("clear"), A_DEFFLOAT, 0);
 }
 
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