Re: [Discuss-gnuradio] problem understanding the ninput_items/noutput_items

[Michael Dickens]

Hi Jason - This behavior is normal. If you're curious, read through the
code in gnuradio-runtime/lib/block_executor.cc, specifically here: <
https://github.com/gnuradio/gnuradio/blob/master/gnuradio-runtime/lib/block_executor.cc#L395
>. Note the comments: "not enough input on input[i]" and "if we can, try
reducing the size of our output request" coupled with dividing the
number of output items to test for (in ::forecast). The implication is
that some upstream block isn't providing data as fast as this block is
consuming it. So it's not the downstream null sink that's causing this
behavior, it's whatever is upstream. Hope this helps! - MLD

On Mon, Nov 6, 2017, at 12:46 PM, Jason Matusiak wrote:
> I am having a problem understanding something simple in my general_work 
> function.
> 
> I have a forecast function, but I seem to get different sizes for 
> ninput_items/noutput_items in general_work.  What I currently do is find 
> the minimum of the two values and work off of that: int min_items = 
> (ninput_items[0] < noutput_items) ? ninput_items[0] : noutput_items;.
> 
> In my mind that makes sense, but if I print out the values of 
> ninput_items/noutput_items, I see something I think is odd.  Over and 
> over it looks like this (where this is ninput_items/noutput_items= 
> min(ninput_items,noutput_items):
> 2044/1024=1024
> 1020/512=512
> 508/256=256
> 252/128=128
> 124/64=64
> 60/32=32
> 28/16=16
> 12/8=8
> 4/4=4
> 2044/1024=1024
> 1020/512=512
> 508/256=256
> 252/128=128
> 124/64=64
> 60/32=32
> 28/16=16
> 12/8=8
> 4/4=4
> 
> Is this divide-by-two on the output port action what is supposed to 
> happen?  I don't understand why it keeps dropping and then jumps up in 
> size again.  I am driving a null sink, so it should be able to keep up 
> no problem....