When rinning simple_example.py - OverflowError: can't convert negative value to size_t

[ivbsd1]

Hi,

I recently tried to use gpyfft on following setup:
CPU - ARMv7, 32bits
Debian: Linux tinkerboard 4.4.103+ #1 SMP Fri Jun 22 16:14:49 CST 2018 armv7l GNU/Linux
Python 3.5.3
Cython 0.29.15
Pyopencl 2019.1.2

I installed libclfft and build gpyfft in following way:
python3 setup.py build
python3 setup.py install

After that I tried to run simple_example.py from examples directory and I received:
Traceback (most recent call last):
File "simple_example.py", line 13, in
transform = FFT(context, queue, data_gpu, axes = (2, 1))
File "/usr/local/lib/python3.5/dist-packages/gpyfft-0.7.3-py3.5-linux-armv7l.egg/gpyfft/fft.py", line 93, in init
plan = GFFT.create_plan(context, t_shape)
File "gpyfft/gpyfftlib.pyx", line 142, in gpyfft.gpyfftlib.GpyFFT.create_plan
File "gpyfft/gpyfftlib.pyx", line 219, in gpyfft.gpyfftlib.Plan.init
OverflowError: can't convert negative value to size_t

Can you, please, help me to fix this problem ?

Thanks

[ivbsd1]

Actually, I succeeded to fix this problem.
In file gpyfftlib.pyx, I changed
ctypedef size_t voidptr_t
to
ctypedef int voidptr_t

and rebuild gpyfft. Now this works.
Please let me know if you can give more elegant solution

[geggo]

Thanks for the report, that is a less common platform. I think you discovered a bug. Your fix is ok for your platform, I will try to find some platform independent solution. One possibility might be to use

ctypedef ptrdiff_t voidptr_t

Can you please test this and report back?

For the records: The problem arises when converting e.g. a OpenCL context reference (natively a void*) from pyopencl, where it is exposed as a (signed) Python int (int_ptr attribute), back to a void*. By any reason, a direct cast is not possible/allowed in cython, therefor an intermediate cast to some signed integer type of platform dependent size is needed. size_t is guaranteed to be large enough, but it is an unsigned integer type. ptrdiff_t is devised for signed arithmetic, but I am not sure if it has the right size on all platforms, could be longer. Don't know if that could create any harm.

hope that helps
Gregor

[ivbsd1]

Hi,

I did the change, you suggested
ctypedef ptrdiff_t voidptr_t
and it works.

Thanks