pytorch masked_fill: why can't I mask all zeros?

Question

I want to mask the all the zeros in the score matrix with -np.inf, but I can only get part of zeros masked, looked like

you see in the upper right corner there are still zeros that didn't get masked with -np.inf

Here's my codes:

q = torch.Tensor([np.random.random(10),np.random.random(10),np.random.random(10), np.random.random(10), np.zeros((10,1)), np.zeros((10,1))])
k = torch.Tensor([np.random.random(10),np.random.random(10),np.random.random(10), np.random.random(10), np.zeros((10,1)), np.zeros((10,1))])
scores = torch.matmul(q, k.transpose(0,1)) / math.sqrt(10)
mask = torch.Tensor([1,1,1,1,0,0])
mask = mask.unsqueeze(1)
scores = scores.masked_fill(mask==0, -np.inf)

Maybe the mask is wrong?

Answer 1

Your mask is wrong. Try

scores = scores.masked_fill(scores == 0, -np.inf)

scores now looks like

tensor([[1.4796, 1.2361, 1.2137, 0.9487,   -inf,   -inf],
        [0.6889, 0.4428, 0.6302, 0.4388,   -inf,   -inf],
        [0.8842, 0.7614, 0.8311, 0.6431,   -inf,   -inf],
        [0.9884, 0.8430, 0.7982, 0.7323,   -inf,   -inf],
        [  -inf,   -inf,   -inf,   -inf,   -inf,   -inf],
        [  -inf,   -inf,   -inf,   -inf,   -inf,   -inf]])

Answer 2

In mujjiga's code, scores tensor is itself used as mask and hence it will replace all 0's as -inf though that is not the usual intended use of a mask. A mask is generally independent of the tensor which one would want to mask.