[question] image size limitation? about popsift HOT 5 CLOSED

The reason is that CUDA Textures have strict size limits. Until someone adds an alternative code path, the best we can do it giving a better and earlier warning. I propose PR#89 for that.

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I was looking to the code and it seems that you upscale the image per default by a factor of 2.
If I choose a factor of 1, I have enough memory to extract the features.
Is there a big impact on accuracy by not upscaling the input image ?

The out of memory error comes from allocating an 3d array (cudaMalloc3DArray) of
width x upscale x height x upscale x (levels - 1)

Would it be possible to rather use (levels - 1) x 2d array instead ?
In this case, there should be enough memory in most common graphic card.

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The upscaling by 2 is the default of the original SIFT paper.
From my understanding of the algorithm, you would lose the highest quality features because you must take the first image, blur it 4 times, then compute the 3 Difference-of-Gaussian layers, and then you can search for feature point candidates in the middle one of those 3. So ... quite a bit of more blurry than the original image. Upscaling fixes that problem.

The RTX 2080 has a quite large amount of memory, but it limits the maximum Surface2DLayered size to 65536 (bytes) × 32768 × 2048. Are you sure that memory allocation fails in your case and not the creation of the surface?

It is absolutely possible to use very much less memory at the price of slightly slower code. It was just never a goal for me. Several of the currently supported alternative downscaling approaches would not be supported in that case and feature points would have to be collected differently, but it could be done.

Unfortunately, I'm not able to do it in the foreseeable future.

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You can adjust the SIFT params in popsift::Config.
See setDownsampling:

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@fabiencastan config.setDownsampling(0); solves my issue, Thanks

@griwodz thanks for the explanation, it does make sense.
the first allocation that failed is cudaMalloc3DArray in Octave::alloc_interm_array()
the maximum Surface2dLayered supported by my graphic card is 32768 x 32768 x 2048

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