Dear Marcus,
1). The line 299 of gnuradio-runtime/lib/block_executor.cc is:
noutput_items = min_available_space(d, m->output_multiple(),
m->min_noutput_items());
If this line shows that set_min_output_items() works on the fly, does
this also shows set_out_multiple() works on the fly?
(just to confirm because I do not fully understand the source code).
2). Regarding the returning 0 issue, let me share my experience of
experiments.
I am creating a custom interpolation block with its interpolation factor
can be changed on the fly. Hence it is inherited from gr::block. It has
one input port and one output port.
During runtime, there will be no problem if the general_work() return 0,
provided it consume a non-zero value.
The flow graph may become unresponsive when the general_work() return 0 and
consume zero.
My explanation:
Says, the instantaneous interpolation factor is 800. The general_work() is
now called with noutput_items=699 and ninput_items[0]=3. In this case the
only correct thing that general_work() should do is to consume 0 and return
0.
But later the general_work() will be repeatedly called again with the same
arguments, i.e. noutput_items=699 and ninput_items[0]=3. In this case again
the general_work() has to consume 0 and return 0. This may repeat few
thousand rounds, or infinite rounds. When this happens the flow graph
becomes unresponsive (hang).
That's why it is important to set_min_output_items() to the instantaneous
interpolation factor (which is 800), if the set_output_multiple() doesn't
work on the fly.
If there is no better workaround, we have to stick to this trick at the
moment.
Regards,
Activecat
On Fri, Mar 7, 2014 at 6:00 PM, Marcus Müller <mar...@hostalia.de> wrote:
> Hi Activecat,
>
> to answer question 1):
> grepping for "min_noutput_items" instantly shows that in
> gnuradio-runtime/lib/block_executor.cc line 299, your block's
> min_noutput_items() is called every iteration. If there isn't enough space,
> the block thread sleeps until there is more. So yes, it works on the fly.
>
> I remember there was something with returning 0, and I know that producing
> 0 items used to mark a source as done, but this mechanism was commented out
> about a year ago (l. 483ff, I think for some good reason), but I can't
> remember that being an issue for a non-source block; have you tried it and
> did you run into problems?
>
> Greetings,
> Marcus
>
>
>
> On 03/07/2014 02:26 AM, Activecat wrote:
>
> Dear Sir,
>
> Let me explain the reason of why to use the function:
> set_min_noutput_items().
>
> I am creating a custom interpolator block.
> Says, the interpolation factor is 1000. Hence it is important to call
> set_output_multiple(1000).
>
> Meanwhile, for this block the interpolation factor depends on Sample
> Rate (samp_rate). In this flow-graph the samp_rate could be changed by the
> user during runtime. This means the interpolation factor may change during
> runtime, and hence we need to call set_output_multile() with different
> values during runtime !
>
> The problem arisen when there is no guarantee that set_output_multiple()
> will work if you change it on the fly.
> (Refer
> http://lists.gnu.org/archive/html/discuss-gnuradio/2010-11/msg00504.html)
>
> The workaround is to use set_min_noutput_items() if it work on the fly.
> Says, after changing samp_rate, the new interpolation factor is
> recalculated as 800.
> If the set_output_multiple(800) doesn't work, the general_work() can still
> consume 1 input and produce 800 output if the noutput_items is at least
> 800. This enables the flow graph continue to work.
>
> If the noutput_items is less than 800, the only correct thing the
> general_work() can do is to consume_each(0) and return 0. This may be
> problematic and can cause unforeseen behavior. So it is important to make
> sure the noutput_items is at least 800. Hence I call:
> set_min_noutput_items(800)
>
> This means we can make use of set_min_noutput_items() as a workaround,
> if set_output_multiple() doesn't change on the fly.
>
> The questions are:
> 1). Can we use this to change setting on the fly:
> set_min_noutput_items()
> 2). Is there any better workaround for this?
>
> Regards,
> Activecat
>
>
>
>
>
>
>
> On Thu, Mar 6, 2014 at 11:36 PM, Tom Rondeau <t...@trondeau.com> wrote:
>
>> On Thu, Mar 6, 2014 at 2:12 AM, Activecat <active...@gmail.com> wrote:
>> > Dear Sir,
>> >
>> > In c++ we have: set_min_noutput_items()
>> > What is it equivalent syntax in python ?
>> >
>> > I try this:
>> > self.set_min_noutput_items()
>> >
>> > Error message:
>> > AttributeError: 'quadrator_upconverter_python1' object has no
>> attribute
>> > 'set_min_noutput_items'
>> >
>> > Note:
>> > The self.set_output_multiple() in python seems accepted, is it
>> functional
>> > ..?
>> >
>> > Regards,
>> > Activecat
>>
>> Looks like when this feature was added, it didn't make it into the
>> block.i swig file. I'll push a patch for this soon.
>>
>> But before you try and use this, be very careful. This is an advanced
>> issue that's really only meant to be used if you a) really really need
>> it and b) really really know what you are doing and why.
>>
>> Tom
>>
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing
> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
