Hi,

I have a 3 dimension tensor “prob: tensor([[[0.2793, 0.3314, 0.3893]]], grad_fn=)”

and I am sampling an action by Categorical distribution.

```
print("prob:",prob)
action = Categorical(prob).sample().detach()
print("action:",action)
log_prob_a = log_prob.gather(1, action)
```

This is the output I am getting.

prob: tensor([[[0.3201, 0.3268, 0.3531]]], grad_fn=)

action: tensor([[2]])

Traceback (most recent call last):

File “D:\get_data\ind_a3c_lstm.py”, line 99, in train

log_prob_a = log_prob.gather(1, action)

RuntimeError: Index tensor must have the same number of dimensions as input tensor

My, Question is why action is not have same number of dimensions as prob tensor.