FlightAware Discussions

Dump1090-fa wisdom question

Hello. I’ve recently changed from dump1090-mutability from Debian 10’s package to dump1090-fa compiled and installed from source. Around two hours ago I was reading the FlightAware dump1090 github page again and at the bottom it showed how to, within the source code directory, run “make wisdom-local” in a terminal then add “–wisdom /path/to/wisdom.local” to the command-line switches, all of which I did. My messages received counts have at least quadrupled which is good, but I haven’t been able to find any documentation on what this “wisdom” is, what it does and how it works. Can anyone enlighten me? Thanks.

You should assign the question to that category:

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There are several different builds of some of the core DSP routines in dump1090, compiled with different optimizations / different instruction sets. Some will be faster than others, but which version is the fastest depends a lot on the exact machine (CPU type, etc) that it runs on - e.g. some CPUs may not support some of the extended SIMD instruction sets, and the same code can run at different relative speeds on different CPUs depending on their internal architecture.

There’s a default ordering which tries to provide a good balance for all CPUs, but it’s not necessarily perfect for any given machine.

The wisdom file (terminology stolen from FFTW) essentially lists which version to use for each DSP routine. “make wisdom-local” runs benchmarks and selects the best (fastest) for the local machine.

There should be no functional difference - all the different versions are meant to produce the same results. It’ll just be faster / take less CPU.

Thanks @obj for explaining.

I have run wisdom in March this year (when Piaware ver 5.0 was released), but never understood what was it’s purpose.

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Dumb question: I’m running airspy_adsb. I have no /etc/dump1090-fa. I ran ‘/usr/share/dump1090-fa/generate-wisdom’ and created ‘/tmp/wisdom.Ywl14Y/wisdom.local’. If I create /etc/dump1090-fa and copy wisdom.local to that directory and restart dump1090-fa will it have any effect?

Thanks.

So it’s basically a sort of automatic optimization routine. Got it. Thanks.

airspy_adsb does not use dump1090’s wisdom files, and dump1090 only has DSP work to do if it’s running the demodulator, so in that case a wisdom file will do nothing.

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Thanks for that @obj :+1: