In :
http://pytorch.org/docs/torch.html#torch.addmm 368
we have :
torch.addmm(beta=1, mat, alpha=1, mat1, mat2, out=None)
out = (beta * M) + (alpha*mat1 @ mat2)

In torch.nn.Linear we have :
output.addmm_(0, 1, input, weight.t())
So is it the case that :

0 in output.addmm_(0, 1, input, weight.t()) is beta

1 in output.addmm_(0, 1, input, weight.t()) is M or mat

So out = alpha*mat1 @ mat2


? Thanks