issues: 675482176

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
675482176 MDU6SXNzdWU2NzU0ODIxNzY= 4325 Optimize ndrolling nanreduce 6815844 open 0     5 2020-08-08T07:46:53Z 2023-04-13T15:56:52Z   MEMBER      

In #4219 we added ndrolling. However, nanreduce, such as ds.rolling(x=3, y=2).mean() calls np.nanmean which copies the strided-array into a full-array. This is memory-inefficient.

We can implement inhouse-nanreduce methods for the strided array. For example, our .nansum currently does make a strided array -> copy the array -> replace nan by 0 -> sum but we can do instead replace nan by 0 -> make a strided array -> sum This is much more memory efficient.

 
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