How to use Torch index select for this use case?

1

I have an index tensor of size [N], that contains indices from 0 to 200

I have a tensor of size [200, N, 3]

I want to somehow do torch.index_select(tensor, 0, index) and get a tensor of size [1, N, 3]. Basically, it needs to select the index in a batch friendly manner etc. How do i do this?

2

I don’t quite understand the desired output shape given the input tensor and index.
If tensor is defined as:

B, N, C = 5, 4, 3
x = torch.arange(B*N*C).view(B, N, C)
print(x)

what would be the desired output?
If you want to create an output of [1, N, 3] you would index x in dim0 with a single value.