fix sequence parallelism conflict in kimiVL

[ShareLer]

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What does this PR do?

Fix sequence parallelism conflict in kimiVL patch.

Background:
A recent VLM-related PR(#1739 ) has modified the sequence parallelism logic of VLM: Split inputs_embeds after the model's embedding layer instand of spliting input_ids and position_ids before forward.
However, the SP logic I implemented in KimiVL's PR(#1639 ) was still implemented in accordance with the old logic. And split the image token at the combination of image_token and text_token to avoid the problem of 'the Image features and image tokens do not match'.
Since these two PR were developed in parallel which led to logical conflicts after the PR were merged.

High-Level Design

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Specific Changes

• Delete the patch for _merge_with_image_features which to assign the image token to the corresponding SP rank.
• Adjust the processing related to position_ids in _ulysses_flash_attn_forward.

API

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Additional Info.

• Issue Number: Fixes issue # or discussion # if any.
• Training: [Note which backend this PR will affect: FSDP, Megatron, both, or none]
• Inference: [Note which backend this PR will affect: vLLM, SGLang, both, or none]

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[eric-haibin-lin]

thanks! would u mind adding a unit test in tests/models/test_transformers_ulysses.py that reproduce this error?

[hiyouga]

LGTM. Now we should split not the image features but the input ids only

[ShareLer]

thanks! would u mind adding a unit test in tests/models/test_transformers_ulysses.py that reproduce this error?

It might not be possible to add the unit test of KimiVL because the unit tests in tests/models/test_transformers_ulysses.py rely on importing the model's config from transformers (ie: 'KimiVLConfig') to create a mock model by from_config, while in transformers the model and config of kimiVL are not defined.

It is necessary to add ulysses-related unit tests for VLM. Perhaps I can first try to add a unit test related to ulysses for QwenVL.

[hiyouga]

@ShareLer The unittest for qwen2vl ulysses already exists https://github.com/volcengine/verl/blob/85fef90d518577b44abca3015249c6cde52b0be9/.github/workflows/e2e_ppo_trainer.yml#L200-L208

I think current state is sufficient