Re: [Discuss-gnuradio] scratch space in output buffer

[Miklos Maroti]

Hi Ron,

Thanks for the quick response!

On Tue, May 30, 2017 at 3:32 PM, Ron Economos <address@hidden> wrote:
> If you call set_output_multiple() in your block constructor, it will
> guarantee the size of the output buffer.

That would actually work (so I return exactly one block of items less
than requested, and use the last slot for scratch space), although it
will be inefficient for large scratch space size (I need a few hundred
samples).

> The scheduler won't touch it until you exit your block with:
>
> return noutput_items;

No good, I would like my scratch place to be preserved across
general_work calls, so return noutput_items will not be enough.

Best,
Miklos

>
> Ron
>
>
> On 05/30/2017 12:57 PM, Miklos Maroti wrote:
>>
>> Hi,
>>
>> I would like to use scratch space within the output buffer of a block,
>> but not sure if I can rely on the scheduler not altering the content
>> of those items in the output buffer that I have written to but have
>> not made it available to downstream blocks within general_work. I know
>> how blocks, forecast, general_work and history works, but I think my
>> use case is not covered.
>>
>> A simple toy use case would be to implement a fir filter without the
>> history call (I know that in this case history is better). Once a new
>> sample is taken from the input you multiply that with an N-length
>> kernel and add it to the output buffer and output only one item and
>> zero out N-item ahead.
>>
>> Can I rely on the scheduler not to modify unproduced items (but of
>> course within the limits of ninput_items)? Should I return 0 for
>> forecast when there is not enough space in the output buffer? Would
>> such a block be synchronous?
>>
>> Best,
>> Miklos
>>
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