[Memory Leak] Revert "[TE][Fix] Comparison of the output tensor"

[AndrewZhaoLuo]

Reverts #9829

The above behavior avoids having TE output Tensors change in address everytime by caching the tensors instead of reallocating everytime. However in doing so they introduce a cyclic dependency. Each Operation has a list of Tensors. However, each Tensor has a reference to the Operation. As a result, each will always have a reference to each other and never be deleted under TVM's reference counting system.

Possible alternatives:

• Something like a weak_ptr, probably so a counted reference exists between the tensor --> operator but not in the opposite direction. Don't know if this is in TVM rn
• Refactoring above PR to somehow avoid cyclic dependency

I'm reverting for now though.

Thanks to @mbrookhart for help in finding this memory error!

[mbrookhart]

Cc @leeexyz @Hzfengsy @junrushao1994

[tqchen]

I agree that the PR should be revereted.

To compare two tensors, we need to use deep comparison, the operator== of Tensor is also overloaded. In general we should avoid self-reference here

[tqchen]

cc @leeexyz

[leeexyz]

@AndrewZhaoLuo Sorry for the issue I introduced that I did not think too much. I am just wondering the original idea here is also has a cyclic dependency, operation <-> tensor, even the tensors are created every time.

@tqchen I agree with your suggestion that using Tensor::operator== is a better solution.

Thanks for your kind help.

[Hzfengsy]

I'm sorry that I didn't find the problem during reviewing. Please fix the CI and merge it as soon as possible.

[AndrewZhaoLuo]

@leeexyz the old way tensor has a reference to the operator but operator does not have a reference to the tensor so we do not have cyclic references.