Output is all 0 in howto_square_ff::general_work()

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1

Hi,
Thanks to Seeve Bunch especially and sorry for my silly question.
It’s work well now. but , I still have some perplexity.
here is the printf information in the file of howto_square_ff ::
general_work():

noutput_items = 4
input_items[0] = -3.000000
output_items[0] = 9.000000
input_items[1] = 4.000000
output_items[1] = 16.000000
input_items[2] = -5.500000
output_items[2] = 30.250000
input_items[3] = 2.000000
output_items[3] = 4.000000

noutput_items = 1
input_items[0] = 3.000000
output_items[0] = 9.000000

while the source code is :
howto_square_ff::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const float *in = (const float *) input_items[0];
float *out = (float *) output_items[0];
//test
printf (“noutput_items = %d\n”,noutput_items);

for (int i = 0; i < noutput_items; i++){
printf (“input_items[%d] = %f\n”, i, in[i]);
out[i] = in[i] * in[i];
printf (“output_items[%d] = %f\n”, i, out[i]);
}
I can not understand that the src_data is src_data = (-3, 4, -5.5, 2, 3)
which have 5 items in all, but why separate into 2 step ,the one is
noutput_items = 4, the other is noutput_items = 1 ?

在2010-05-23，"Steve Bunch" [email protected] 写道：

const float *in = (const float *) input_items[0];
float *out = (float *) output_items[0];

…
printf (“input_items[%d] = %d\n”, i, in[i]);
out[i] = in[i] * in[i];
printf (“output_items[%d] = %d\n”, i, out[i]);

in and out reference floating point numbers. You are printing them with
%d instead of a floating point format, such as %f.

Steve

2

The scheduler chooses the amount of data to process each time. Here it
chose
4 the first time it ran the general_work() function and the next time it
chose 1. You can look into the scheduler’s implementation to know how it
chooses this. If you want to make it choose 5 the first time then you
can
call gr_block::set_output_multiple() function to set the the
output_items to
be a multiple of 5. This will make the scheduler choose 5 items on input
stream. There are other things involved too and I suggest looking at
gr_block.h file to know more.

2010/5/23 zzw.1012 [email protected]