[Rtk-users] Stream divisions in rtkfdk

[Simon Rit]

Since it fails in cufft, it's the memory of the projections that is a
problem. Therefore, it is not surprising that --divisions has no
influence. But --lowmem should have an influence. I would suggest:
- to uncomment
//#define VERBOSE
in itkCudaImageDataManager.hxx and try to see what amount of memory
are requested.
- to try to reproduce the problem with simulated data so that we can
help you in finding a solution.
Simon

On Wed, May 21, 2014 at 2:21 PM, Chao Wu <wuchao04 at gmail.com> wrote:
> Hi Simon,
>
> Yes I switched on an off the --lowmem option and it has no influence on the
> behaviour I mentioned.
> In my case the system memory is sufficient to handle the projections plus
> the volume.
> The major bottleneck is the amount of graphics memory.
> If I reconstruct a little bit more slices than the limit that I found with
> one stream, the allocation of GPU resource for CUFFT in the
> CudaFFTRampImageFilter will fail (which was more or less expected).
> However with --divisions > 1 it is indeed able to reconstruct more slices,
> but only a very few more; otherwise the CUFFT would fail again.
> I would expect the limitations of the amount of slices to be approximately
> proportional to the number of streams, or do I miss anything about stream
> division?
>
> Thanks,
> Chao
>
>
>
> 2014-05-21 13:43 GMT+02:00 Simon Rit <simon.rit at creatis.insa-lyon.fr>:
>
>> Hi Chao,
>> There are two things that use memory, the volume and the projections.
>> The --divisions option divides the volume only. The --lowmem option
>> works on a subset of projections at a time. Did you try this?
>> Simon
>>
>> On Wed, May 21, 2014 at 12:18 PM, Chao Wu <wuchao04 at gmail.com> wrote:
>> > Hoi,
>> >
>> > I may need some hint about how the stream division works in rtkfdk.
>> > I noticed that the StreamingImageFilter from ITK is used but I cannot
>> > figure
>> > out quickly how the division has been performed.
>> > I did some test with reconstructing 400 1500x1200 projections into a
>> > 640xNx640 volume (the pixel and voxel size are comparable).
>> > The reconstructions were executed by rtkfdk with CUDA.
>> > When I leave the origin of the volume at the center by default, I can
>> > reconstruct up to N=200 slices with --divisions=1 due to the limitation
>> > of
>> > the graphic memory. Then when I increase the number of divisions to 2, I
>> > can
>> > only reconstruct up to 215 slices; and with divisions to 3 only up to
>> > 219
>> > slices. Does anyone have an idea why it scales like this?
>> > Thanks in advance.
>> >
>> > Best regards,
>> > Chao
>> >
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>
>