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

[Activecat]

On Wed, Jun 4, 2014 at 2:22 PM, xianda <address@hidden> 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; }         

In your first example above, you have exactly two input ports.

That's why you need to specify "ninput_items_required[0]" and "ninput_items_required[1]", there are in total 2 ports.

In fact in this example the value of "ninput_items_required.size()" is 2.

In alternative, you could also replace above two lines with:

    for (unsigned i=0; i < 2; i++)

       ninput_items_required[i] = 100 * noutput_items;

Or, to be more generic, you could also use this:

   for (unsigned i=0; i < ninput_items_required.size(); i++)
       ninput_items_required[i] = 100 * noutput_items;

 

             2.I want to know if we use the general_work().Is it means that we must use the forcast()?Thanks.
Best regards

If you use "general" block, you need to specify "forecast()".

"General" block has "general_work()" function but not "general()" function.

If you use sync block, decim, interpolation block etc, you have "work()" but not "general_work()", and you don't need to write "forecast()".

This is very straight-forward.