FFT segfault

[jmeyers314]

import galsim

fwhm = 0.00012892424082577847
e1 = 0.0
e2 = 0.0
dx = -0.24762100026331102
dy = 0.3718091783120656
nx = ny = 90
scale = 0.2

print(f"Attempting drawImage with {fwhm=}, {e1=}, {e2=}, {dx=}, {dy=}, {nx=}, {scale=}")
obj = galsim.Kolmogorov(fwhm=fwhm).shear(e1=e1, e2=e2).shift(dx, dy)
img = obj.drawImage(nx=nx, ny=ny, scale=scale)
print(f"ok, sum={img.array.sum():.6f}")

This segfaults with galsim 2.8.4 for me at USDF. Certainly my fault for letting an optimizer try to draw such a thing, but shouldn't the failure be more graceful than a segfault?

Tail of the traceback is

  File "/sdf/group/rubin/sw/conda/envs/lsst-scipipe-13.0.0/lib/python3.13/site-packages/galsim/image.py", line 795 in _wrap
  File "/sdf/group/rubin/sw/conda/envs/lsst-scipipe-13.0.0/lib/python3.13/site-packages/galsim/gsobject.py", line 1997 in drawFFT_finish
  File "/sdf/group/rubin/sw/conda/envs/lsst-scipipe-13.0.0/lib/python3.13/site-packages/galsim/gsobject.py", line 2045 in drawFFT
  File "/sdf/group/rubin/sw/conda/envs/lsst-scipipe-13.0.0/lib/python3.13/site-packages/galsim/gsobject.py", line 1813 in drawImage

[rmjarvis]

Oof. Two in one day. Brenna Wells reported a seg fault in Piff (most likely due to GalSim as well I assume) today too.

FWIW, I think yours is due to an extremely large FFT. Here is the output I get running this script:

Attempting drawImage with fwhm=0.00012892424082577847, e1=0.0, e2=0.0, dx=-0.24762100026331102, dy=0.3718091783120656, nx=90, scale=0.2
/Users/Mike/miniforge3/envs/py3.12/lib/python3.12/site-packages/galsim/errors.py:441: GalSimFFTSizeWarning: drawFFT requires a very large FFT.
The required FFT size would be 81488 x 81488, which requires 148.42 GB of memory.
If you can handle the large FFT and want to suppress this warning,
you may update gsparams.maximum_fft_size.
  warnings.warn(GalSimFFTSizeWarning(message, size))

So yeah. This used to raise an exception for too large an FFT. This is the downside of not requiring people to explicitly set maximum_fft_size to avoid the error is now sometimes there is just a warning and then maybe catastrophe. Is this a win for the average user or not?