Hi all, Thank you for your clarifications, Now I understand the concept much better.
Best regards On Thu, Sep 10, 2015 at 8:36 PM, Richard Bell <richard.be...@gmail.com> wrote: > Nicolas, > > The GNU Radio scheduler hands your block a certain number of samples > everytime the blocks work function is called. The work function gets called > many times over the course of a running flowgraph. To be technically > correct, the scheduler tells your block how much memory it has to store > output (noutput_items) and makes sure you have enough input to produce an > output, which it learned from the forecast() function. In your case, you're > seeing the scheduler give 4096 samples to the block in a call to work. This > doesn't mean you are stuck using only 4096 samples, it just means you have > to write your code so that it collects what it needs over the course of > several calls to work and then computes an output. I know this is hard to > understand for beginners, but it's central to how GNU Radio works, so worth > absorbing. > > set_output_multiple() gives you a little more control on what > noutput_items will be. For example, set_output_multiple(100000) tells the > scheduler that it shouldn't call your work function unless it can provide > 100,000 noutput_items or more. That means it could be 200,000, 300,000, > N*100,000 where N is a positive integer. If you overuse this, you might > hurt performance of your flowgraph, because you're placing additional > constraints on the scheduler. I try to avoid it unless I find I really need > it. I almost never need it. > > Hope that helps, > Rich > > On Thu, Sep 10, 2015 at 9:37 AM, Martin Braun <martin.br...@ettus.com> > wrote: > >> On 10.09.2015 07:25, Nicolas Cuervo Benavides wrote: >> > 1. Where does the 4096 comes from? it is 2¹², which I don't recall being >> > 12 the size of one datatype that is involved in my function. It is >> > directly a value from scheduler and always the same? >> >> This value is pretty much random; 4096 works well with pages, but it >> could be any other value. noutput_items is how much valid items you have >> in your buffer. On the *first run*, all other values will be zero (but >> after that, they may contain old samples). >> >> > 2. If it is not always the same value, how I am indirectly fixing that >> > amount of samples? I would like, if possible, to save more samples as it >> > would reduce the variance of the calculations. >> >> You need to construct your block to handle *any* number of samples, >> unless you constrain it e.g. with set_output_multiple(). Your variance >> can be calculated over several work() calls, until you've read enough >> samples. >> >> Your code may have some other issues, but it's hard to say without >> seeing the rest of the work function. >> >> M >> >> _______________________________________________ >> 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 > > -- Nicolás Cuervo Benavides Handy: +49 157 70476855 Electric and Electronic Engineering department. Electronic Engineering Universidad Nacional de Colombia -- Student M.Sc. Information and Communication Technology Karlsruher Institut für Technologie Karlsruhe, Baden Würtemberg, Germany
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