6193 add a buffer_step option to the sliding windows util/speed up

[wyli]

Fixes #6193

Description

• adds buffer_step (code adapted from @myron's idea/implementation)
• clean up multioutput resizing logic
• perf optimize
• overlap to support different values along the spatial dimensions

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[wyli]

/build

[wyli]

/build

[myron]

I'm going to test it

[Nic-Ma]

Looks good to me.
SlidingWindow is quite important and widely used in MONAI applications, please ensure to test it in typical tutorials and bundles before merging.
@KumoLiu Please also help review it.

Thanks.

[wyli]

/build

[wyli]

/build

[myron]

@wyli this looks great! thanks for writing.

a few comments

1. perhaps the default for buffer_dim should be -1 (as this is the most common)
2. SlidingWindowInferer parameter type for "overlap" should be updated to overlap: float | Sequence (since it accepts a list now)
3. setting buffer_step option seems only appropriate together with setting device='cpu". It wasn't obvious. I tried using buffer_step=1, and GPU memory increased (compared to buffer_step==None). and it took me some time to figure out that device parameter needs to be manually specified to cpu. a user usually leaves that option as a default None, so it won't be obvious. may be we can give a warning, or just automatically set device to 'cpu' when the buffer_step is not None.

thanks!

[wyli]

thanks @myron, I'll revise it