Hi Alessandro,

I replicated your tests as exactly as possible, modifying 
CMAKE_CXX_FLAGS and General_FFLAGS by the addition of "-mtune=native".
Using WSJT-X and the "Shift+F6" command, the sequence of ten files 
(01.wav, 02,wav, ... 10.wav) was processed in 21 seconds with or without 
the addition of "-mtune=native" before building the program from 
scratch.  I could find no measurable difference in execution speed for 
the two cases.  Certainly they were the same to within 1 second.

I note also that the total execution time is very nearly the same as 
what I reported yesterday for the execution of jt9[.exe] from the 
command line.  Almost all of the CPU-intensive "number crunching" in 
WSJT-X occurs in the Fortran code in jt9.  Other tasks such as display 
of graphical information and decoded text, writing output files, etc.,
make comparatively trivial demands on CPU resources.

It remains a mystery to me why you have seen large differences in 
execution speed after adding the compiler flag "-mtune=native".

        -- 73, Joe, K1JT

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