In torch.FloatTensor the parameter you put into it is the shape not the values in the tensor while in torch.tensor you pass in the values of the tensor not the shape.
The short answer is: don’t use torch.FloatTensor to create tensors, but stick to the factory methods, such as torch.randn, torch.ones, torch.empty, torch.tensor, etc.
The former approach might have unexpected behavior (as see in this topic), could yield an uninitialized tensor (as explained by @Dwight_Foster) etc.