[megatron]delete cpu sync

[yangbofun]

PR type

• Bug Fix
• New Feature
• Document Updates
• More Models or Datasets Support

PR information

1. Delete the CPU sync when rope, which speeds up 1.5%.

before:

after:

Experiment results

Paste your experiment result here(if needed).

[gemini-code-assist]

Summary of Changes

Hello, 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 aims to enhance the performance of the Rotary Positional Embedding (RoPE) application by eliminating an unnecessary CPU synchronization step. The change streamlines the logic for detecting batched RoPE usage, resulting in a reported speedup of 1.5%.

Highlights

• Performance Optimization: Removed CPU synchronization logic related to Rotary Positional Embedding (RoPE) calculation, leading to a reported 1.5% speedup.
• RoPE Batched Calculation: Simplified the determination of whether to use batched RoPE by directly comparing freqs.shape[0] with t.shape[0], eliminating reliance on context parallel group size and cu_seqlens.

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[gemini-code-assist]

Code Review

This pull request simplifies the logic for determining use_batched_rope within the _apply_rotary_pos_emb_thd function in swift/megatron/init.py. The previous calculation involving cp_group, cp_size, and cu_seqlens_for_batched has been removed, and use_batched_rope is now directly determined by comparing freqs.shape[0] with t.shape[0]. There are no review comments to provide feedback on.