2 new computes: chunk/spread/atom and reduce/chunk

[sjplimp]

Purpose

New compute chunk/spread/atom and compute reduce/chunk commands.

Author(s)

Steve

Backward Compatibility

N/A

Implementation Notes

Example code is provided in the 2 doc pages which can be added to bench/in.chain
and examples/micelle/in.micelle which illustrate how to use the new commands.

Post Submission Checklist

Please check the fields below as they are completed

• The feature or features in this pull request is complete
• Suitable new documentation files and/or updates to the existing docs are included
• One or more example input decks are included
• The source code follows the LAMMPS formatting guidelines

Further Information, Files, and Links

Put any additional information here, attach relevant text or image files, and URLs to external sites (e.g. DOIs or webpages)

[sjplimp]

@akohlmey I think the one line I deleted in the last commit in fix ave/chunk should not be set,
since it does not produce peratom output. Am I missing some logical need for it?

[akohlmey]

@sjplimp won't be able to look into this for a while. Starting the LAMMPS tutorial in Indonesia tomorrow.

[akohlmey]

@sjplimp i suspect that the variable initialization you removed was done to avoid some uninitialized variable access error. i think you are correct to remove the line, but those xxx_freq variables should be initialized in fix.cpp instead. Since those are commonly used with the % operator, they are best initialized to -1 instead of 0, to avoid division by zero and have the operation result 0.

[akohlmey]

Made a few, mostly cosmetic changes