Re: [Discuss-gnuradio] something about forecast()

[Marcus Müller]

Hi Xianda,
the io_signature specifies a minimum and a maximum number of inputs, so
this might be 1,2 or 3.

Greetings,
Marcus
On 04.06.2014 10:24, xianda wrote:
> Hi:
>       Thank you so much.
>       Now i want to ask:if we set 
>                                                   gr::block("c_vcvc",
>                                                               
> gr::io_signature::make(1, 3, sizeof(gr_complex)*length1),
>                                                               
> gr::io_signature::make(1, 1, sizeof(gr_complex)*length1))
>     then: ninput_items_required.size ()=1 or 3?
> Thanks,
> Best regards
>
>
>
>
>
> At 2014-06-04 03:10:40, "Marcus Müller" <address@hidden> wrote:
> Hi Xianda,
>
> Easiest answer first:
>
> 2. You need to write a forecast if, and only if, you're using general_work. I 
> generally try to avoid doing that.
>
> Then:
> 1.
> ninput_items_required is, as you can see in the function signature, a 
> reference to a vector.
> The size of the vector is the number of input ports.
> Compare to 
> http://gnuradio.org/doc/doxygen/classgr_1_1block.html#a5bc118d94944d2ff71e378f807fb8d28
>
> Greetings,
> Marcus
>
>
> On 04.06.2014 08:22, xianda wrote:
>
> Hi all:
>          I want to know something about the forecast().
>          I have already known that forcast() can tell  scheduler how many 
> input items are required for each output item.
>      1.But now i have read two example:
>         The first one:
>                        void your_block::forecast(int 
> noutput_items,gr_vector_int &ninput_items_required){
>                                     ninput_items_required[0]=100 * 
> noutput_items;
>
>                                     ninput_items_required[1]=100 * 
> noutput_items; }         
>                      I have already understand it.
>         But the second one:
>                          void  forecast (int noutput_items, gr_vector_int 
> &ninput_items_required)
>                            {
>                                unsigned ninputs = ninput_items_required.size 
> ();
>                                  for (unsigned i = 0; i < ninputs; i++)
>                                    ninput_items_required[i] = 1;}
>                     I can't understand since we can't know how many input 
> items we required,why use  ninput_items_required.size ().Can someone help me?
>              2.I want to know if we use the general_work().Is it means that 
> we must use the forcast()?Thanks.
> Best regards
>
>
>
>
>
>
>
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