[PD] Patchmatrix Execution Order Issues

Sat Jan 20 13:16:17 CET 2007

Hallo,
Luke Iannini (pd) hat gesagt: // Luke Iannini (pd) wrote:

> Now, the issue I was having crops up when routing the result of a
> single inlet "matrixed" to multiple outlets back into an inlet.  I
> think it occurs in your copy as well: the first outlet to recieve the
> input (let's say it was "10101" again) transmits it to the top of the
> chain, and before your list drip has completed, a new input/row is
> received that overrides the first (also replacing the contents of the
> list append at the bottom).
> 
> I have attached a modified copy of your patch demonstrating this.
> Most mods are in the lower left; use my element definitions to see the
> issue in action.  If you disconnect the "loopback" sends (outputs Y&Z
> >inputs B&C in the lower left) it works fine, but when they are
> connected only one output makes it out.

Okay, this is indeed true and it has to do with Pd's "depth first"
message passing: Pd tries to walk along a message path until this path
ends. E.g. if you have a [t b b] then first everything connected to
the right outlet will be worked out completely before the bang from
the left outlet of the trigger will fire. 

With your loopback setup, walking along will work fine for the
outletY-route at first, but as soon as inletB fires, the counter after
the matrix in [pd count] will be reset to start at 0 again and the
[list] storing the 10101 will be overwritten by what's coming in
through inletB (in this case, a 10101 will come in again, but that's
just luck, it could be something different). So a lot of stuff will be
invalidated by the looped back message.

The solution is to defer the looped back messages until every direct
message has finished operations. You can do this easily with [pipe]
objects between the [r outlet?] and [s inlet?] objects. [pipe] (and
[del] will delay messages for one logical step even, if the delay time
is 0. They kind of insert a temporary end point to the depth first
message operations.

As a bonus I attached a little GUI abstraction to edit 0/1 matrices of
arbitrary size. This might be useful for your patch. It expects Pd at
least 0.40 to look nice. It also seems to trigger a bug in Pd and
makes the red GOP rectangle appear on the parent somehow. 

Ciao
-- 
 Frank Barknecht                 _ ______footils.org_ __goto10.org__
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