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Re: [Discuss-gnuradio] Code Reuse Question

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Code Reuse Question
Date: Thu, 12 May 2016 18:18:16 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

Yeah, like the head block, it's a copying operation. But that's "relatively cheap".
I'm not quite sure about the state of this, but at GRCON '14 work was started on letting blocks define where their buffers are – maybe, one day, as a side effect, we can actually use the same buffers for in- and output and get rid of the copying.

On 12.05.2016 18:07, Richard Bell wrote:
If we wanted that behavior, could we do something similar to what gating blocks do (like the power squelch), where we pass X number of items through and after that only consume items without ever producing anything. Is there an efficiency problem with this technique?

On Thu, May 12, 2016 at 6:14 AM, Marcus Müller <address@hidden> wrote:
Yep, having had a walk over this: if we didn't want to have this behaviour, we'd need to have some buffer_writer specific done_policy or so, where we tell the block it should shut down based on whether all or just any one of its buffer readers signaled WORK_DONE.
We don't have that, so this is the only way to shut down a graph tree from a non-source block.

On 12.05.2016 14:58, Tom Rondeau wrote:
On Thu, May 12, 2016 at 5:13 AM, Marcus Müller <address@hidden> wrote:
Yeah, I've been actually scratching my head on whether that is
intentional or not – if we don't have that behaviour, there's no chance
that a leaf in a non-path tree-shaped flow graph can stop the flow
graph, is there?

Definitely intentional and the way it's worked since the beginning.


On 12.05.2016 12:23, Sylvain Munaut wrote:
> Hi,
>> I thought so, too, at first, but then tested:
>> Null src +-> Head --> Null sink0
>>          \----------> Null sink1
>> stops.
>> I think this is the "am done" message bubbling up from head to src, then
>> src knowing it should be done, then the info "there's no input coming
>> anymore" bubbling down to sink1. Thoughts?
> I'd classify that as a bug.
> I don't think that's the intended behavior. (but I tested too and
> that's indeed what happens, even with non-null sink/source)
> Cheers,
>    Sylvain

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