[Discuss-gnuradio] Really big items, best practices?

[Martin Braun]

Hi everyone,

we've recently been working one some GR projects where item sizes can
get really big. One example is cyclostationary spectral estimation code,
which will be released soon.

If you're not familiar with cyclostationary spectral estimation, here's
the problem: the result of the estimator is a matrix, which, depending
on your estimator resolution, can be quite big (at least a several
hundred thousand floats per estimate, which would correspond to one
logical item).

With GNU Radio, very large item sizes do not work that well since the
inter-block buffers are shared between threads and therefore, max size
is limited by the OS. I'm sure you know what I mean :)

Question is, what's a good way to handle this? For the cyclo stuff, we
had to fix things manually by introducing separate buffers, splitting
the estimate into many small items and then manually keeping track of
what already had been consumed.

This doesn't seem to be the ideal solution. The whole point of GNU Radio
is that someone else (i.e. the GR scheduler) takes care of all of this,
and I, the developer, can focus on the signal processing component.

I'm wondering if anyone has some experience with large items they would
like to share. In particular, is there a way to limit the number of
items in the buffers? Or is this possibly a shortcoming of GNU Radio?

Martin

-- 
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

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