> Dear Flexers, I have tried to use the various command line options for > fftw_wisdom.exe to make it run for longer than one pass. I thought the > docs said to enter "-t5" for 5 minutes. But it seems to ignore the -t > option with no comment or error. > > Bob commented that he had been running fftw_wisdom on one of his > super-fast computers for a very long time (days? weeks?) and so I > figured it must be a good idea to try it on my computer at least over > night. But no joy. > > Anyone know how to persuade it to run longer? is it worth the effort? > perhaps you get a better representation of the innards of your CPU? > > TU de ken N9VV > >
Well, fftw_wisdom is (last I knew) a fully self-contained open source product. Should be able to read the standard web doc. Haven't done anything with our version, but I've used it on one other project. Extra run time should (in theory) help, but in truth, increased run times don't always matter all that much. What's happening here (if you don't already know) is that FFTs seem to have a near-infinite number of ways they can be implemented and the "wisdom" thing simply tries out various combinations of these until it gets the best it can find given the amount of time you spent looking. It then saves that result and uses it (when instructed, as our code surely does) thereafter for the "run time" FFT. In my limited experience dealing with an entirely different use of the FFT (the "convolution multiply" trick), extremely long run times on fftw_wisdom didn't matter much. Five minutes was as good as an hour. Larry WO0Z
