# Running multiple flow graphs simultaneously

**URL:** <https://www.ruby-forum.com/t/running-multiple-flow-graphs-simultaneously/240202>\
**Category:** GNU Radio\
**Created:** [April 1, 2014, 11:30pm UTC](https://www.ruby-forum.com/t/running-multiple-flow-graphs-simultaneously/240202 "2014-04-01T23:30:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [April 1, 2014, 11:30pm UTC](https://www.ruby-forum.com/t/running-multiple-flow-graphs-simultaneously/240202/1 "2014-04-01T23:30:26Z")

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Hi -

Is it possible to run more than one top\_block at a time in gnuradio  
3.7.x? I have an application where I wish to run an additional flow  
graph periodically. I have set up a thread that grabs samples via a  
probe from my main flow graph that is running all of the time, and uses  
that data to source another flow graph. Everything appears to be  
running, however I want to be certain that I’m not doing something  
terribly wrong — especially since two relevant sources of information  
seem to contradict my current mode of operation:

From the Python application writing tutorial (June 2008)  
[http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsWritePythonApplications](http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsWritePythonApplications)

From a January 2012 gnuradio mailing list post:  
[http://lists.gnu.org/archive/html/discuss-gnuradio/2012-01/msg00145.html](http://lists.gnu.org/archive/html/discuss-gnuradio/2012-01/msg00145.html)

Best,  
Rob

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**Author:** ![coldtone](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9e8a1a/32.png) [@coldtone](https://www.ruby-forum.com/u/coldtone)\
**Post date:** [April 2, 2014, 2:03pm UTC](https://www.ruby-forum.com/t/running-multiple-flow-graphs-simultaneously/240202/2 "2014-04-02T14:03:10Z")

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On 04/01/2014 11:29 PM, Rob M. wrote:

> Is it possible to run more than one top\_block at a time in gnuradio  
> 3.7.x? I have an application where I wish to run an additional flow  
> graph periodically. I have set up a thread that grabs samples via a  
> probe from my main flow graph that is running all of the time, and uses  
> that data to source another flow graph. Everything appears to be

Yes, you can do that.  
It might not be what you want – running 2 top\_blocks is a bit like  
running 2 processes with one tb each.  
You can have a disconnected flow graph in one top block by making each  
FG a hier block, and then adding that to the top block.

> From a January 2012 gnuradio mailing list post:
> 
> [Re: [Discuss-gnuradio] Multiple flow graphs, proper design](http://lists.gnu.org/archive/html/discuss-gnuradio/2012-01/msg00145.html)

It used to be that you could only have 1 top\_block per process. The wiki  
page is not up to date.

M