enable multiple ssm groups duplication

[ilyasch2]

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)". Add mamba multi group duplication
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Purpose

This PR enable the duplication of multiple groups for Mamba models . Before, the groups duplication was only enabled when n_groups == 1. If n_groups divides tp_size, we can duplicate each groups tp_size/n_groups times so that each group can take its rank

For example, this enables Falcon-H1-34B to support TP4 instead of only TP2

Test Plan

Can be tested on gsm8k for Bamba-9B/ Falcon-H1-7B and Falcon-H1-34B

Test Result

(Optional) Documentation Update

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @ilyasch2, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the tensor parallelism capabilities for Mamba models by allowing the duplication of multiple SSM groups. This change addresses a previous limitation where group duplication was only supported when n_groups was 1. By enabling duplication when n_groups divides tp_size, it facilitates more efficient and flexible deployment of Mamba-based models, such as Falcon-H1-34B, across various tensor parallel configurations.

Highlights

• Enhanced Mamba Tensor Parallelism: The core change enables duplication of multiple SSM groups within Mamba models, specifically when n_groups divides tp_size, expanding beyond the previous limitation of n_groups == 1. This allows for more flexible and efficient tensor parallelism configurations.
• Updated Weight Loading Logic: The loader function in mamba_mixer2.py has been modified to incorporate n_groups into its shard_spec and to introduce new logic for calculating the rank. This new logic dynamically determines the rank based on whether duplicate_groups is true, if n_groups is a multiple of tp_size, or if tp_size is a multiple of n_groups.
• Relaxed Tensor Parallelism Constraints: A previous assertion in the __init__ method of MambaMixer that restricted n_groups to either be 1 or a multiple of tp_size has been removed. This removal is crucial for allowing the new, more flexible multi-group duplication strategy to function.

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[gemini-code-assist]

Code Review

The pull request introduces changes to enable the duplication of multiple groups for Mamba models when n_groups divides tp_size. The changes involve modifications to the logic for computing the rank in the loaded shard, updating comments, and adjusting assertions to accommodate the new functionality. The code review identified areas for improvement in comment accuracy, assertion messages, and potential missing assertions.

[gemini-code-assist]

This assertion message could be improved to be more descriptive about the conditions that lead to this assertion. Consider including the values of tp_size and n_groups in the message.