Adjust nChannels on Mi350x based on ranks and nodes

[dmwu]

Adjust nChannels based on the number of ranks and nodes for better bandwidth.

Details

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Work item: "Internal", or link to GitHub issue (if applicable).

What were the changes?
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Why were the changes made?
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How was the outcome achieved?
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Approval Checklist

Do not approve until these items are satisfied.

• [ ] Verify the CHANGELOG has been updated, if
  • there are any NCCL API version changes,
  • any changes impact library users, and/or
  • any changes impact any other ROCm library.