[FIXED] How to reorder tensor based on indexes tensor from the same size

Issue

Say I have tensor A, and indexes Tensor: A = [1, 2, 3, 4], indexes = [1, 0, 3, 2]

I want to create a new Tensor from these two with the following result : [2, 1, 4, 3] Each element of the result is element from A and the order is defined by the indexes Tensor. Is there a way to do it with PyTorch tensor ops without loops?

My goal is to do it for 2D Tensor, but I don't think there is a way to do it without loops, so I thought to project it to 1D, do the work and project it back to the 2D.

Solution

You can use scatter:

A = torch.tensor([1, 2, 3, 4])
indices = torch.tensor([1, 0, 3, 2])
result = torch.tensor([0, 0, 0, 0])
print(result.scatter_(0, indices, A))

Answered By - teplandr