Re: [Discuss-gnuradio] Dealing with `divide 0` or `Inf` in GNU Radio C++ code.
Hi Jeff,
you could use a strcture like this
MA_divisor = Divide: % =multiply = pad sink.
|- threshold detector-^
i.e. take the divisor path in parallel into threshold detector and use the
output (in {0,1}) in a multiplier for masking the dividing by zero cases.
By adjusting the threshold to 0+eps (a small number of your choice), this also
solves the problem of huge output if the divisor is _almost_ 0.
Best regards
Stephan Ludwig
Robert Bosch GmbH
Corporate Sector Research Advance Engineering, Communication Technology
(CR/AEH4)
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www.bosch.com
Tel. +49(711)811-8809
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Von: discuss-gnuradio-bounces+stephan.ludwig2=de.bosch@gnu.org
[mailto:discuss-gnuradio-bounces+stephan.ludwig2=de.bosch@gnu.org] Im
Auftrag von Jeff Long
Gesendet: Mittwoch, 19. August 2015 13:31
An: discuss-gnuradio@gnu.org
Betreff: Re: [Discuss-gnuradio] Dealing with `divide 0` or `Inf` in GNU Radio
C++ code.
(That should be moving averages, not correlators). Also, subtracting
instead of dividing might do what you want.
Jeff
On 08/19/2015 07:25 AM, Jeff Long wrote:
Jeon,
You can add an appropriate constant before the divide and compensate
for it afterward. The exact math will depend on the values coming out
of the correlators.
Jeff
On 08/19/2015 06:50 AM, Jeon wrote:
Let's think about the following auto/cross correlator:
http://i.imgur.com/Fy5hdVj.png
I've placed `divide` because I need to normalize the correlation result.
If we place `null source`, or `constant source with value of zero`
right before the `pad source`, the simplified form of the correlator
becomes 0 divided by 0.
I've placed `time sink` right after the `pad sink` then, I can see
the line hit the infinity. With a simplified flow graph:
http://i.imgur.com/Msx9EQj.png
Back to the my correlator, how can I handle such `infinity` value
coming into the next block?
My guess is that if a source block is a type of float, then
`infinity` might have a maximum value of float. So, I think I can
reject `infinity` value with `if (in[i] threshold)`, where
`threshold` is big enough, for correlator it is fine to have a value just
larger than one.
Do you think what I guess is right? Or can some boost numeric types,
or PMT help somehow to deal with it?
In addition, not important.
In pages
http://en.cppreference.com/w/cpp/types/numeric_limits/infinity
and http://en.cppreference.com/w/cpp/numeric/math/INFINITY,
non floating point numeric types can't handle infinity.
Is it also applied to GNU Radio?
Regards,
Jeon.
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Re: [Discuss-gnuradio] Dealing with `divide 0` or `Inf` in GNU Radio C++ code.
Jeon, You can add an appropriate constant before the divide and compensate for it afterward. The exact math will depend on the values coming out of the correlators. Jeff On 08/19/2015 06:50 AM, Jeon wrote: Let's think about the following auto/cross correlator: http://i.imgur.com/Fy5hdVj.png I've placed `divide` because I need to normalize the correlation result. If we place `null source`, or `constant source with value of zero` right before the `pad source`, the simplified form of the correlator becomes 0 divided by 0. I've placed `time sink` right after the `pad sink` then, I can see the line hit the infinity. With a simplified flow graph: http://i.imgur.com/Msx9EQj.png Back to the my correlator, how can I handle such `infinity` value coming into the next block? My guess is that if a source block is a type of float, then `infinity` might have a maximum value of float. So, I think I can reject `infinity` value with `if (in[i] threshold)`, where `threshold` is big enough, for correlator it is fine to have a value just larger than one. Do you think what I guess is right? Or can some boost numeric types, or PMT help somehow to deal with it? In addition, not important. In pages http://en.cppreference.com/w/cpp/types/numeric_limits/infinity and http://en.cppreference.com/w/cpp/numeric/math/INFINITY, non floating point numeric types can't handle infinity. Is it also applied to GNU Radio? Regards, Jeon. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Dealing with `divide 0` or `Inf` in GNU Radio C++ code.
(That should be moving averages, not correlators). Also, subtracting instead of dividing might do what you want. Jeff On 08/19/2015 07:25 AM, Jeff Long wrote: Jeon, You can add an appropriate constant before the divide and compensate for it afterward. The exact math will depend on the values coming out of the correlators. Jeff On 08/19/2015 06:50 AM, Jeon wrote: Let's think about the following auto/cross correlator: http://i.imgur.com/Fy5hdVj.png I've placed `divide` because I need to normalize the correlation result. If we place `null source`, or `constant source with value of zero` right before the `pad source`, the simplified form of the correlator becomes 0 divided by 0. I've placed `time sink` right after the `pad sink` then, I can see the line hit the infinity. With a simplified flow graph: http://i.imgur.com/Msx9EQj.png Back to the my correlator, how can I handle such `infinity` value coming into the next block? My guess is that if a source block is a type of float, then `infinity` might have a maximum value of float. So, I think I can reject `infinity` value with `if (in[i] threshold)`, where `threshold` is big enough, for correlator it is fine to have a value just larger than one. Do you think what I guess is right? Or can some boost numeric types, or PMT help somehow to deal with it? In addition, not important. In pages http://en.cppreference.com/w/cpp/types/numeric_limits/infinity and http://en.cppreference.com/w/cpp/numeric/math/INFINITY, non floating point numeric types can't handle infinity. Is it also applied to GNU Radio? Regards, Jeon. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
