REF: Reorganize how multi-device parallelism is implemented

[carterbox]

Purpose

Reduce communications overhead for multi-device reconstructions and hopefully speed up large reconstructions.

Separate multi-device parallelism from reconstruction logic (ptycho solver implementation).

Approach

Instead of synchronizing every update to the probe/object across all devices, use an approach that is more like distributed consensus where devices only communicate with their neighbors for object updates and synchronization only happens once per epoch.

The effect of this approach on performance is minor reduction in time per epoch for all numbers of GPUs, but increase in the number of epochs required for convergence for multi-gpu reconstructions because information is exchanged between GPUs less frequently.

Pre-Merge Checklists

Submitter

• Write a helpfully descriptive pull request title.
• Organize changes into logically grouped commits with descriptive commit messages.
• Document all new functions.
• Click 'details' on the readthedocs check to view the updated docs.
• Write tests for new functions or explain why they are not needed.
• Address any complaints from pep8speaks.

Reviewer

• Actually read all of the code.
• Run the new code yourself; the included tests should make this easy.
• Write a summary of the changes as you understand them.
• Thank the submitter.

[pep8speaks]

Hello @carterbox! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file src/tike/communicators/pool.py:

Line 459:81: E501 line too long (81 > 80 characters)

• In the file src/tike/ptycho/probe.py:

Line 158:81: E501 line too long (81 > 80 characters)
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• In the file src/tike/ptycho/ptycho.py:

Line 395:81: E501 line too long (101 > 80 characters)
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• In the file src/tike/ptycho/solvers/lstsq.py:

Line 83:81: E501 line too long (85 > 80 characters)
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• In the file src/tike/ptycho/solvers/options.py:

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• In the file src/tike/ptycho/solvers/rpie.py:

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• In the file tests/communicators/test_pool.py:

Line 146:81: E501 line too long (81 > 80 characters)
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Line 164:36: E203 whitespace before ':'
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Comment last updated at 2024-07-17 18:41:45 UTC