On 10/02/2010 05:39 AM, Tom Boothby wrote:
> Was this on sagenb.org? Frequently, the server will kill your process
> at the most inopportune times...
>
> On 10/1/10, ancienthart <joalheag...@gmail.com> wrote:
>> I get the following:
>>
>> a = FFT(4)
>> a[1] = 2
>> a.forward_transform()
>>
>> Everything works fine up to here. Then, when I do this:
>>
>> a.backward_transform()
>> a
>>
>> I get:
>> NameError: name 'a' is not defined
>>
>> Any ideas?
>>
>> Joal Heagney
I get
sage: a.backward_transform()
------------------------------------------------------------
Unhandled SIGSEGV: A segmentation fault occurred in Sage.
This probably occurred because a *compiled* component
of Sage has a bug in it (typically accessing invalid memory)
or is not properly wrapped with _sig_on, _sig_off.
You might want to run Sage under gdb with 'sage -gdb' to debug this.
Sage will now terminate (sorry).
------------------------------------------------------------
if the number of points is a power of two.
>From near the end of sage/gsl/fft.pyx:
def backward_transform(self):
cdef gsl_fft_complex_wavetable * wt
cdef gsl_fft_complex_workspace * mem
N = Integer(self.n)
e = N.exact_log(2)
if N==2**e:
gsl_fft_complex_backward(self.data, self.stride, self.n, wt,
mem)
Should this be
gsl_fft_complex_radix2_backward(self.data, self.stride, self.n)
(and similarly for inverse_transform)?
if N!=2**e:
mem = gsl_fft_complex_workspace_alloc(self.n)
wt = gsl_fft_complex_wavetable_alloc(self.n)
gsl_fft_complex_backward(self.data, self.stride, self.n, wt,
mem)
gsl_fft_complex_workspace_free(mem)
gsl_fft_complex_wavetable_free(wt)
That the notebook sometimes doesn't show the SIGSEGV message may be a
different problem.
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