Date: Feb 18, 2013 4:14 AM
Author: Edric Ellis
Subject: Re: feval works but gather fails

"AL_math " <anatlibman1@gmail.com> writes:

> I am processing an image, by using CUDA kernels. I am calling
> GPUoutput = feval(........ ), and everything is fine, no error
> messages appear. But when I call: "output = gather(GPUoutput);" then
> I get an error messagse:
>
> " Error using parallel.gpu.GPUArray/gather
> An unexpected error occurred during CUDA execution. The CUDA error was:
> CUDA_ERROR_UNKNOWN. "


All CUDA kernel invocations return before the actual computation is
complete, so problems in your kernel can show up later when you try and
access the resulting data. I suspect that is what is happening here.

> The more strange fact, is that when I am calling less blocks of
> threads to process only part of the image, but still need to gather
> back an image of the same size (which is simply partially black) the
> problem is gone.


It sounds like when you try to work on the whole image, you may be
reading or writing beyond the bounds of the image.

Cheers,

Edric.