How to do operations on scalar tensors?

[emvazquez]

Hi,
I would like to know how to perform operations on scalar tensors. For example, the following code fails

t = np.array([1, 2, 3])
a = np.array([4, 4, 4])
a.attach_grad()
with mx.autograd.record():
    b = 2.0 * np.dot(a, t)
    
db = mx.autograd.grad(b, [a])
print(db)

with the following error

MXNetError: Operator _npi_multiply_scalar inferring shapes failed.
input shapes:
None
output shapes:
None
operator attributes:
scalar : 2.0

The reason is that I am multiplying np.dot(a, t), which is a zero-dimensional array, with a number.

What is the correct way to do that?

Thank you.