Reduce overhead in reformat

[daurer]

The way we are currently updating views, there can be a huge overhead which is especially problematic in two scenarios

• A single dataset (scan) with a very large number of views (e.g. electron ptychography)
• A combination of datasets loaded as a large list of scans

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Two avoid such overheads, I am proposing the following changes

1. Move container reformating to the outermost layer in new_data,
   i.e. reformat once after all scans and views have been loaded
2. Keep track of changes that are made to particular views and only update if absolutely needed

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Example benchmarks of data loading times before/after the above changes have been applied

Case 1

Electron Ptychography data with N frames of shape XxY
Data loading before: XX seconds
Data loading after: YY seconds
Speed increase Nx

Case 2

Ptychography data set with N scans, each with K frames of shape XxY, combined into a single reconstruction.
Data loading before: XX seconds
Data loading after: YY seconds
Speed increase Nx