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Fix beam search for Llama models by adding reorder_cache method #2753

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amrothemich
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When using beam search with Unsloth-optimized Llama models, users encounter: NotImplementedError: Make sure that a reorder_cache function is correctly implemented in transformers.models.llama.modeling_llama

This occurs because Unsloth patches LlamaForCausalLM but doesn't preserve the reorder_cache static method required for beam search operations.

The fix adds the missing reorder_cache method after Unsloth's patching, ensuring compatibility with transformers' beam search functionality. This allows users to use generation methods like model.generate(num_beams=N) without errors.

amrothemich and others added 2 commits June 17, 2025 09:35
@amrothemich @claude
Fix beam search for Llama models by adding reorder_cache method
e526628 
When using beam search with Unsloth-optimized Llama models, users encounter:
NotImplementedError: Make sure that a `reorder_cache` function is correctly
implemented in transformers.models.llama.modeling_llama

This occurs because Unsloth patches LlamaForCausalLM but doesn't preserve
the reorder_cache static method required for beam search operations.

The fix adds the missing reorder_cache method after Unsloth's patching,
ensuring compatibility with transformers' beam search functionality.
This allows users to use generation methods like model.generate(num_beams=N)
without errors.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Fix pyproject.toml license field to comply with PEP 621
9927e31 
The license field was using a simple string format which causes
installation failures with modern setuptools. PEP 621 requires
the license to be specified as either {file: "path"} or {text: "value"}.

This change updates the license field to use the correct object format,
allowing successful package installation from source.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
@danielhanchen
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Thanks! I think pyproject.toml doesn't need changes hopefully right?
Is it possible to move the static method outside of the function?

@amrothemich
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Oops I wasn't trying to merge it in yet, it's not ready. I do think pyproject.toml needs changes (unrelated to the inference issue). Whenever I try to pip install, I get:

× Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [95 lines of output]
      configuration error: `project.license` must be valid exactly by one definition (2 matches found):
      
          - keys:
              'file': {type: string}
            required: ['file']
          - keys:
              'text': {type: string}
            required: ['text']
      
      DESCRIPTION:
          `Project license <[https://peps.python.org/pep-0621/#license>`_](https://peps.python.org/pep-0621/#license%3E%60_).
      
      GIVEN VALUE:
          "Apache-2.0"
      
      OFFENDING RULE: 'oneOf'
      
      DEFINITION:
          {
              "oneOf": [
                  {
                      "properties": {
                          "file": {
                              "type": "string",
                              "$$description": [
                                  "Relative path to the file (UTF-8) which contains the license for the",
                                  "project."
                              ]
                          }
                      },
                      "required": [
                          "file"
                      ]
                  },
                  {
                      "properties": {
                          "text": {
                              "type": "string",
                              "$$description": [
                                  "The license of the project whose meaning is that of the",
                                  "`License field from the core metadata",
                                  "<[https://packaging.python.org/specifications/core-metadata/#license>`_](https://packaging.python.org/specifications/core-metadata/#license%3E%60_)."
                              ]
                          }
                      },
                      "required": [
                          "text"
                      ]
                  }
              ]
          }
      Traceback (most recent call last):
        File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-91456821-3098-4104-a8da-189c5a8c8178/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
          main()
        File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-91456821-3098-4104-a8da-189c5a8c8178/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-91456821-3098-4104-a8da-189c5a8c8178/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
          return hook(config_settings)
                 ^^^^^^^^^^^^^^^^^^^^^
        File "/usr/local/lib/python3.12/dist-packages/setuptools/build_meta.py", line 332, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=[])
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/local/lib/python3.12/dist-packages/setuptools/build_meta.py", line 302, in _get_build_requires
          self.run_setup()
        File "/usr/local/lib/python3.12/dist-packages/setuptools/build_meta.py", line 318, in run_setup
          exec(code, locals())
        File "<string>", line 1, in <module>
        File "/usr/local/lib/python3.12/dist-packages/setuptools/__init__.py", line 117, in setup
          return distutils.core.setup(**attrs)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/local/lib/python3.12/dist-packages/setuptools/_distutils/core.py", line 158, in setup
          dist.parse_config_files()
        File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-91456821-3098-4104-a8da-189c5a8c8178/lib/python3.12/site-packages/_virtualenv.py", line 22, in parse_config_files
          result = old_parse_config_files(self, *args, **kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/local/lib/python3.12/dist-packages/setuptools/dist.py", line 608, in parse_config_files
          pyprojecttoml.apply_configuration(self, filename, ignore_option_errors)
        File "/usr/local/lib/python3.12/dist-packages/setuptools/config/pyprojecttoml.py", line 71, in apply_configuration
          config = read_configuration(filepath, True, ignore_option_errors, dist)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/local/lib/python3.12/dist-packages/setuptools/config/pyprojecttoml.py", line 136, in read_configuration
          validate(subset, filepath)
        File "/usr/local/lib/python3.12/dist-packages/setuptools/config/pyprojecttoml.py", line 60, in validate
          raise ValueError(f"{error}\n{summary}") from None
      ValueError: invalid pyproject.toml config: `project.license`.
      configuration error: `project.license` must be valid exactly by one definition (2 matches found):
      
          - keys:
              'file': {type: string}
            required: ['file']
          - keys:
              'text': {type: string}
            required: ['text']
      
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× Getting requirements to build wheel did not run successfully.
│ exit code: 1
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.

And the change here fixes it.

amrothemich and others added 2 commits June 17, 2025 10:35
@amrothemich @claude
Fix beam search method name from reorder_cache to _reorder_cache
e2799ac 
The transformers library expects the method to be named _reorder_cache
(with underscore) for beam search functionality. The previous commit
incorrectly used reorder_cache without the underscore, causing the
NotImplementedError to persist.

This corrects the method name to match transformers' expectations,
properly enabling beam search for Unsloth-optimized Llama models.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Refactor: Move _reorder_cache to module level function
ebe2e6b 
Moved the _llama_reorder_cache function outside of the pre_patch method
to make it a clean module-level function. This improves code organization
and follows Python best practices by avoiding nested function definitions
where unnecessary.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich
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I'd also like to come up with a more general solution so we don't have to do this for every model, since I know Gemma has had issues too. Will update and ping you when it's ready :)

amrothemich and others added 7 commits June 17, 2025 11:00
@amrothemich @claude
Fix beam search for PEFT models by adding _reorder_cache to PeftModel…
7a9e575 
…ForCausalLM

The beam search error was occurring because PEFT models wrap the base model
and need their own _reorder_cache method. This commit adds the same
_reorder_cache implementation to PeftModelForCausalLM class.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Fix beam search for all model instances including PEFT base_model
8e6c982 
Added _reorder_cache method to:
1. Model instances in from_pretrained
2. PEFT model instances in patch_peft_model
3. Base model of PEFT models (model.base_model)

This ensures beam search works regardless of how the model is accessed
during generation.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Refactor beam search fix into a general solution in _utils.py
a0b9e4c 
- Created general_reorder_cache function in _utils.py that works for all transformer models
- Created patch_model_for_beam_search function to patch any model instance
- Updated llama.py to use the general solution instead of model-specific implementation
- This fix now automatically works for all models (Gemma, Mistral, Qwen, etc.) that inherit from FastLlamaModel
- Models that don't inherit can easily use patch_model_for_beam_search to add beam search support

This is a more maintainable solution that fixes beam search for all Unsloth models.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Improve beam search fix with better documentation and error handling
da309b8 
- Added explanation of why we need to provide our own _reorder_cache implementation
- Added None check in general_reorder_cache for safety
- Documented that newer models rely on Cache classes but beam search might still use legacy format
- Clarified that our implementation is based on working models from transformers library

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Fix: Make _reorder_cache a staticmethod on model classes
540bf1f 
The transformers library expects _reorder_cache to be a staticmethod on the model class,
not a regular method. This matches the pattern used by models like GPT2 and OPT.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Fix: Patch _reorder_cache in the transformers module namespace
5adb3f7 
The key issue was that we were only patching our local import of LlamaForCausalLM,
but the error was looking for _reorder_cache in transformers.models.llama.modeling_llama.
Now we patch both the local import AND the transformers module's version.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich @claude
Add comprehensive beam search debugging summary and clean up debug pr…
39ded96 
…ints

- Added detailed debugging history to CLAUDE.md including all attempted fixes
- Documented the root cause and current state of the beam search issue
- Removed debug print statements from llama.py
- Ready to transfer to Windows machine for further debugging

The beam search fix attempts to patch _reorder_cache in multiple places:
1. Local LlamaForCausalLM class
2. PeftModelForCausalLM class
3. transformers.models.llama.modeling_llama.LlamaForCausalLM

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@danielhanchen
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@amrothemich Actually can you move the pyrpoject.toml PR to a new PR thanks :)

amrothemich and others added 3 commits June 18, 2025 23:06
@amrothemich @claude
Add Google Colab notebook for beam search debugging
980f3d5 
This notebook provides a minimal test case to debug the beam search issue
on a GPU-enabled environment. It:
- Clones our fix-reorder-cache branch
- Installs unsloth from source
- Tests beam search with a small model
- Includes debugging code to check module paths

To use: Upload to Google Colab and run with GPU runtime.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
@amrothemich
removed check whether reorder cache is already defined before reassig…
fb36e23 
…ning it
@amrothemich
Update pyproject.toml
3a72bf3
@danielhanchen
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@amrothemich I think it's best to open a new PR - I think you included Claude Code :)

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@amrothemich @danielhanchen