sqrt_vml_cpu not implemented for 'Long'
a = torch.full([2, 2], 9)

b = a.sqrt()
print(b)

b = a.rsqrt()
print(b)

RuntimeError: sqrt_vml_cpu not implemented for 'Long'

a is torch.LongTensor, but sqrt and rsqrt do not suppor Long, what should I do?

I couldn't reproduce your code because, when I run it, I get the following error (PyTorch 1.6):
RuntimeError: Providing a bool or integral fill value without setting the
optional `dtype` or `out` arguments is currently unsupported. In PyTorch 1.7,
when `dtype` and `out` are not set a bool fill value will return a tensor of
torch.bool dtype, and an integral fill value will return a tensor of
torch.long dtype.

However, I think your problem occurs because PyTorch does not support square root operation for Long/torch.int64. You should use another data type. This should do it:
a = torch.full([2, 2], 9, dtype=torch.float32)
b = a.sqrt()
b = a.rsqrt()

