[Discuss-gnuradio] something about forecast()

[xianda]

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