Here you are returning without an error when possibly source was invalid (contained too few elements), but returning if mask.numel() == 0 should be fine?

I think if srcSize == 0, then mask after broadcasting should also have 0 elements as well. But if srcSize is not 0, then mask.numel() can not be 0 as well, because it can not be broadcastable.

It should, but if users sent empty src (erroneously), then instead of getting en error (like today), they'd get not updated self. Here's today's behavior, and there won't be an error after this change you are making:

In [2]: a=torch.randn(4,4)

In [3]: mask = a>0

In [4]: vals = torch.randn(0)

In [5]: vals.size()
Out[5]: torch.Size([0])

In [6]: torch.masked_scatter(a, mask, vals)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-6-35daff38b05a> in <module>
----> 1 torch.masked_scatter(a, mask, vals)

RuntimeError: Number of elements of source < number of ones in mask

Oh, I see, I thought I was checking self.numel() == 0. Thanks for figuring out.

fixed now. I changed it to self.numel() == 0