Re: [Discuss-gnuradio] Custom block overflow

[Marcus Müller]

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Ok, I think don't know why it overflows, but I get a better feeling
for your system :) thanks.

So: You have four UHD sources in parallel, feeding your block's four
input streams simultaneously, is that right? So, in that case, you
have a total sample rate of 2MS/s, which is more in regions where PCs
might be underpowered. You have to do a covariance matrix every 16µs
on average; this is quite a lot, possibly, though I have no idea of
the complexity that involves when using armadillo.

Maybe, you are I/O bound; do you write data to your hard drive or do
something similar after processing?

I think Martin's approach makes very much sense. Could you take the
four USRP sources, do a "streams to vector" and save that using a
file_sink? Do you still get overruns then?

Then, using file source and a vector to streams, could you process
your data offline and see if the would be sufficient for real time
processing?

Greetings,
Marcus



On 05.02.2014 10:55, sarankumar wrote:
> Hi, There is no throttle block in my flow graph. The USRP source is
> directly connected to the custom block. In the custom block, I form
> a 4x8 matrix with 4 being number of USRP's and 8 is the number of
> samples from each of them. Then I do cross co-variance of the
> matrix(4x8) with its transpose(8x4). The resulting 4x4 matrix is
> inverted. I use Armadillo linear algebra package for the
> co-variance and inverse operations. The computer is equipped with 8
> Gig ram and gigabit ethernet card.
> 
> Regards, Saran On Wed, Feb 5, 2014 at 2:56 PM, Marcus Müller
> <address@hidden> wrote:
> 
> Also, since this is a very common mistake: Maybe you have a
> throttle block in your flowgraph. If that's the case, remove it.
> 
> Greetings, Marcus
> 
> (Um, how do you invert a 4x8 matrix?)
> 
> On 05.02.2014 03:52, Martin Braun wrote:
>>>> On 04.02.2014 18:46, sarankumar wrote:
>>>>> Hi all, I am encountering overflow errors in my custom
>>>>> block in GRC even for low USRP sample rates of 500 Ksps.
>>>>> The flow graph goes like 4 USRP's connected to the custom
>>>>> block. The block does matrix correlation and inverse. The
>>>>> size of the matrix is 4x8. Any help? Regards, Saran
>>>> 
>>>> Your flow graph is probably running too slowly. You could
>>>> record IQ data and try w/ offline data.
>>>> 
>>>> MB
>>>> 
>>>> 
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