Re: [Discuss-gnuradio] Struggling with gr-perf-monitorx

[Dan CaJacob]

Hey Tom,

I ran into this "math domain error" with CtrlPort recently.  Based on your suggestion that it might be related to zero work blocks causing a divide by zero, I started hacking away anything that might be being short-circuited in the relatively complex flowgraph.  First, an shorted branch of a select tree - no dice.  Then a copy block.  BAM!  That was it.  I guess copy must be super efficient and not really do any work.

Anyhow, I figure that using a copy block in a fg should reliably reproduce this problem an perhaps serve as a model for working around it.

In my fg, the copy block was serving as a valve that would prevent downstream blocks from executing if it was shut.  In my case, the "valve" was open, and data was flowing through the copy block.

Thanks!

On Tue, Jun 16, 2015 at 11:44 PM Tom Rondeau <address@hidden> wrote:

On Tue, Jun 16, 2015 at 11:11 PM, Dennis Glatting <address@hidden> wrote:

I have this "nearly" working. MX brings up a window, connects to GRC,
briefly displays a graph, then blanks out. Displayed in the command line
window:

gr-perf-monitorx: radio.getKnobs threw exception (math domain error).
...
(repeats)

I'm not sure what that message is telling me in the operation/debug
domain. Clue please.

The paper "Inspecting GNU Radio Applications with ControlPort and
Performance Counters" shows various blocks in Figures 2 and 5 named
"Ctrlport...". Are those necessary for MX? I haven't found anything that
indicates yes or no. Clue please.

Operationally:

address@hidden:~/thrift# gnuradio-companion  --version
GNU Radio Companion v3.7.7.1-131-g71ab508d


address@hidden:~/thrift# lsb_release  -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.04
Release:        15.04
Codename:       vivid

I'm not sure what MX is? Are you using that as shorthand for gr-perf-monitorx?

If that's the case, then no, the Ctrlport Probes are there for other purposes and not necessary for Performance Monitor.

I'm seen that Math Domain error before, but I've never been able to replicate it reliably. I think it's something related to a divide by zero and I think happens when one block's performance measure of work time comes back with 0 -- which doesn't often happen. Are you using any of your own blocks in the flowgraph? What if you run the Controlport Monitor tool instead of Performance Monitor? That will just show you a list of all available parameters exposed by the application over ControlPort.

Tom

 

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