There are 2 kinds of random state in transforms

[Nic-Ma]

Describe the bug
Currently, in the case that a random transform contains another random transform, we have 2 different ways to set the random status:

1. Use the self.R of first transform the second:
   https://github.com/Project-MONAI/MONAI/blob/dev/monai/transforms/croppad/dictionary.py#L761
2. Use the same random seed or state for both transforms:
   https://github.com/Project-MONAI/MONAI/blob/dev/monai/transforms/intensity/dictionary.py#L177

@wyli @rijobro @ericspod Which one do you guys think is better? Then I can try to unify them.

[wyli]

these two options are equivalent, I don't see any issue there, or why is this a bug?

[Nic-Ma]

Hi @wyli ,

I am not sure whether we should pass the self.R from dict transform to the array transform(the first way), is there any potential issue?

Thanks.

[ericspod]

I'm not aware of this being an issue, I think they are numerically equivalent and sharing R objects doesn't bring up known issue. We should use one method or another however and not mix them. Can we imagine a situation where having shared R objects would cause unexpected behaviour? This would occur if a method was called on this object to change it's state before an internal transform was used, thus affecting the state it uses.

[rijobro]

I have no strong feelings either way. But you're right, the more we can unify our code, the better!

[Nic-Ma]

Hi @ericspod @rijobro ,

Thanks for your great discussion.
I agree with @ericspod , we should avoid to share unnecessary random state.
And I also updated the way 1 transforms to way 2 in PR: #3130.
Could you please help review it?

Thanks in advance.