Re: [Discuss-gnuradio] Scheduler Help/Question

[Earle Frank]

Eric Blossom wrote:
> 
> Let's say that block D never produces an output, but is consuming all
> of it's input.  Can you see how this leads to a hang?
> 

I can see that will cause the flow graph to hang. And I followed your
explanation.
I have added a "timeout" feature to block D, so that after a maximum of M
samples, block D will output the appropriate enable signal.
So now it is impossible for block D to consume all inputs and never produce
an output.

Let me further describe my test:
Let N=100, M=40.
The expected enable signal out of block D is:
0 for n=0 to 49
1 for n=50 to 79
0 for n=80 to 89
1 for n=90 to 109
0 for n=110 to 199

Block A produce 100 samples to it's output buffer.
Block B consumed all 100 samples of it's input and produced 100 samples to
it's output buffer.
Block C consumed all 100 samples of it's input and produced 100 samples to
it's output buffer.

Block D consumed all 100 samples of it's input and produced the correct
enable signal for n=0 to 89.
The state inside block D is now 10, because it saw the beginning of an event
from n=90 to 99. It is waiting for the event to end or for the state to
reach M=40.

Block E consumed 90 input samples from the input buffer from B and from the
input buffer from D to produce 30 outputs. These outputs are simply the
values from block B at n=50 to 79.


Eric Blossom wrote:
> 
> It goes like this.  E ends up BLKD_IN on it's second input, but
> meanwhile the buffer on it's first input is full.  It's full because B
> has been writing it as quickly as it can.  Once E's first input buffer
> (== B's output buffer) is full.  B becomes output blocked.  It will
> never run again because it's got nowhere to put it's output.
> 

Shouldn't the output buffer be nearly empty for block B now? Block E has
consumed 90 of the 100 samples from block B.
Shouldn't block B be able to process another 90 samples or even 100 samples
(assuming the output buffer is big enough)?

Why doesn't block A produce the next 100 samples to it's output buffer? And
if it does, why doesn't block C consumed those 100 samples? And also, why
doesn't block B consume at least 90 of those 100 samples??


Thanks again for all the insight
EF

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