To my knowledge, there are B-spline and catmull-rom spline which can be used for bicubic sampling. My question is which type of spline excetly used in the F.grid_sample API with “bicubic” mode?
In the documentation for grid_sample there is a note at then end saying how bicubic is implemented.
They also link to this wikipedia entry, where bicubic convolution algorithm is explained.
I do not know much about this topic, but in this paper they compare these methods and it seems that they are different (meaning it is neither of the methods you mentioned, but another).
I hope this helps 
Yeah, you are right. I checked the links and reproduced the result. Thank you. In my point of view, bicubic refers to all the interpolation method that use cubic splines. Then from the link I realize that BICUBIC is also a specific method with varying alpha.
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