Re: [Discuss-gnuradio] Avoiding divide by zero in case of input being zero.

[CEL]

Hi Anshul,

you shouldn't have to have your own buffer for a running sum – can you
explain why you're doing that? 
A running sum can trivially be implemented with the IIR filter block
with Feed-Forward taps (1,) and Feed-back taps (1,0)!
Where does in a running sum does a division take place? 

> (a) Why am I getting the initial zero samples from the file block in
> gnuradio_companion and non-zero values when using a vector_source in
> unit tests?

If these zeros are not in the file you're reading, your block has a
bug!


> (b) What can I do about it (here specifically as a fix to the
> situation, and a general guideline to always remember)?

good question, but we'd need to know your code, your motivation for a
circular buffer, and why you're implementing a running sum yourself!

Best regards,
Marcus

On Fri, 2018-03-30 at 23:19 +0530, Anshul Thakur wrote:
> Hi,
> 
> I used a circular buffer of finite size to keep the past 'N' power
> values of the sample stream in my block as a part of creating a
> running sum. This buffer is initialized to 0 in the constructor. 
> The running sum of powers is used to compute the average power used
> in computing signal correlation.
> 
> I have a capture stream (cfile) to test the operation of the block.
> The test case uses a vector_source_c block to read the contents of
> the file into memory. The unit tests pass without error. 
> 
> However, when I use the block in a flowgraph in that reads the same
> file from a file source block gnuradio_companion, I am getting the
> first few sample values as 0 which cause a divide by zero
> problem. This messes up the rest of the running sum. I don't want to
> put an 'if' block that checks for the zero condition as it is not
> expected that a device/stream would ever spit out zero values.
> 
> (a) Why am I getting the initial zero samples from the file block in
> gnuradio_companion and non-zero values when using a vector_source in
> unit tests?
> 
> (b) What can I do about it (here specifically as a fix to the
> situation, and a general guideline to always remember)?
> 
> I am using GNURadio version 3.7.12. 
> 
> Regards,
> Anshul
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> Discuss-gnuradio mailing list
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