The problem, methinks, is in the use of the createplan verb in fftw
(~addons/fftw/fftw.ijs).
It passes a boxed noun into the DLL. Pointers to the contents of that
noun are copied by the DLL into the 'plan' it creates.
Subsequent calls to fftwexecute refer to these pointers.
This was never a good idea, but before 8.07 it worked because the data
blocks were ultimately allocated in fftwnd and thus persisted over the
calls.
In 8.07 named inputs to cd are copied to temporary blocks to avoid
aliasing errors, and the temporary blocks are freed when createplan
exits, leaving the stored plan invalid.
I THINK a solution would be to change the * in the next-last line of
createplan to & (3 places). To make this solid, the contents whose
addresses are taken should be protected by executing 15!:15 on them
before they are assigned to their first named value in fftwnd.
Henry Rich
On 11/9/2018 9:26 AM, bill lam wrote:
most probably, incompatible change in j807. the script needs updates, but
everyone is busy.
On Fri, Nov 9, 2018, 9:01 PM 'Rafael Andraschko' via General <
[email protected] wrote:
Hello,
I´m trying to run the 6-dimensional fft example that is in the "Fast
Fourier Transform" lab in the new version of J (8.0.7). In 8.0.6 it works,
I tried to verify any obvious difference between versions but found none.
The code follows:
A=: j./ ?. 1 + i. 2 3 4 5 6 7 8
$A
$B=: fftw A
$C=: ifftw B
+/ , clean A - C
It stops silently in the $B definition calling the fftw verb. Strangely
the previous calls to it were OK.
JVERSION
Engine: j807/j64/windows
Release: commercial/2018-10-05T10:39:42
Library: 8.07.19
Qt IDE: 1.7.9s/5.9.6
Platform: Win 64
Installer: J807 install
InstallPath: c:/users/weierstrass/j64-807
Thanks
Rafael
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