In one of the elegant examples, which is also on this website ( https://www3.aps.anl.gov/forums/elegant ... +scan#p292 ), a tune scan for best dynamic aperture search is provided. I aim to use it as complementary information to the genetic optimization, which I have successfully and extensively used so far.
At first, I run the DATuneScan to benchmark against the picture in the above aps-forum link. I obtain the same result for the APS lattice, but looking more closely, something puzzles me a bit: when I extract the tunes from the files named "scan-tunex-tuney.twi", using a script called "plott" (because it also plot in addition of displaying parameters), I notice that the tune point do not match those indicated in the name of the file:
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[ DATuneScan_cluster_APS_benchmark]$ ./plott scan-36p37-19p40 Printout for SDDS file scan-36p37-19p40.twi ex0 ($gp$rm) = 2.426441e-09 dnux/dp (1/(2$gp$r)) = 5.996089e+00 dnuy/dp (1/(2$gp$r)) = 6.007089e+00 nux (1/(2$gp$r)) = 3.638030e+01 nuy (1/(2$gp$r)) = 1.941797e+01
Looking into the code, it seem that the discrepancy is abs(nuyChange) and abs(nuxChange) [nux/nuyChange are sometimes negative] although it's not clear why this is set up in scanTune main loop rather than daTemplate.ele. It look that the difference of tune is deliberate but then how to interpret it with respect the name of file?
any help would be most kindly appreciated,
PS: my attention was pointed to this because of problems I encountered with low-resolution tune scans for testing purposes: points were missing or even "distorded" and it seemed to be linked to this tune indexing mismatch.
(below: left : Michael's plot, right: my plot from the example)