Add a converter from mamba_ssm -> huggingface mamba (#29705)

* implement convert_mamba_ssm_checkpoint_to_pytorch

* Add test test_model_from_mamba_ssm_conversion

* moved convert_ssm_config_to_hf_config to inside mamba_ssm_available check

* fix skipif clause

* moved skips to inside test since skipif decorator isn't working for some reason

* Added validation

* removed test

* fixup

* only compare logits

* remove weight rename

* Update src/transformers/models/mamba/convert_mamba_ssm_checkpoint_to_pytorch.py
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

* nits

---------
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

src/transformers/models/mamba/convert_mamba_ssm_checkpoint_to_pytorch.py

+# coding=utf-8
+# Copyright 2024 state-spaces/mamba org and HuggingFace Inc. team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""This script can be used to convert checkpoints provided in the `mamba_ssm` library into the format provided in HuggingFace `transformers`. It depends on the `mamba_ssm` package to be installed."""
+
+import argparse
+import json
+import math
+from typing import Tuple
+
+import torch
+
+from transformers import AutoTokenizer, MambaConfig, MambaForCausalLM
+from transformers.utils import logging
+from transformers.utils.import_utils import is_mamba_ssm_available
+
+
+if is_mamba_ssm_available():
+    from mamba_ssm.models.config_mamba import MambaConfig as MambaConfigSSM
+    from mamba_ssm.models.mixer_seq_simple import MambaLMHeadModel
+
+    def convert_ssm_config_to_hf_config(config_ssm: MambaConfigSSM) -> MambaConfig:
+        """Convert a MambaConfig from mamba_ssm to a MambaConfig from transformers."""
+        hf_config = MambaConfig()
+        # Set config hidden size, num hidden layers, and vocab size directly from the original config
+        hf_config.hidden_size = config_ssm.d_model
+        hf_config.intermediate_size = config_ssm.d_model * 2
+        hf_config.time_step_rank = math.ceil(config_ssm.d_model / 16)
+
+        hf_config.num_hidden_layers = config_ssm.n_layer
+        vocab_size = config_ssm.vocab_size
+        pad_vocab_size_multiple = config_ssm.pad_vocab_size_multiple
+        if (vocab_size % pad_vocab_size_multiple) != 0:
+            vocab_size += pad_vocab_size_multiple - (vocab_size % pad_vocab_size_multiple)
+        hf_config.vocab_size = vocab_size
+        return hf_config
+
+
+logging.set_verbosity_info()
+logger = logging.get_logger(__name__)
+
+
+def convert_mamba_ssm_checkpoint_to_huggingface_model(
+    original_state_dict: dict, original_ssm_config_dict: dict
+) -> Tuple[MambaForCausalLM, AutoTokenizer]:
+    if not is_mamba_ssm_available():
+        raise ImportError(
+            "Calling convert_mamba_ssm_checkpoint_to_huggingface_model requires the mamba_ssm library to be installed. Please install it with `pip install mamba_ssm`."
+        )
+    original_ssm_config = MambaConfigSSM(**original_ssm_config_dict)
+
+    # Convert mamba_ssm config to huggingface MambaConfig
+    hf_config = convert_ssm_config_to_hf_config(original_ssm_config)
+
+    # No weights need to be renamed between the two models.
+    converted_state_dict = original_state_dict
+
+    # Load reshaped state dict into a huggingface model.
+    hf_model = MambaForCausalLM(hf_config)
+    tokenizer = AutoTokenizer.from_pretrained("EleutherAI/gpt-neox-20b")
+    hf_model.load_state_dict(converted_state_dict)
+    return (hf_model, tokenizer)
+
+
+def validate_converted_model(
+    original_state_dict: dict, original_ssm_config_dict: dict, hf_model: MambaForCausalLM, tokenizer: AutoTokenizer
+) -> None:
+    """Validate the converted model returns the same output as the original model."""
+    torch_device = "cuda"
+
+    original_config = MambaConfigSSM(**original_ssm_config_dict)
+    original_model = MambaLMHeadModel(original_config).to(torch_device)
+    original_model.load_state_dict(original_state_dict)
+
+    hf_model = hf_model.to(torch_device)
+    input_ids = tokenizer("Hey how are you doing?", return_tensors="pt")["input_ids"].to(torch_device)
+    # Assert model logits are close
+    with torch.no_grad():
+        original_model_logits = original_model(input_ids).logits
+        hf_model_logits = hf_model(input_ids).logits
+    if not torch.allclose(original_model_logits, hf_model_logits, atol=1e-3):
+        raise ValueError("The converted model did not return the same logits as the original model.")
+
+    logger.info("Model conversion validated successfully.")
+
+
+def convert_mamba_checkpoint_file_to_huggingface_model_file(
+    mamba_checkpoint_path: str, config_json_file: str, output_dir: str
+) -> None:
+    if not is_mamba_ssm_available():
+        raise ImportError(
+            "Calling convert_mamba_checkpoint_file_to_huggingface_model_file requires the mamba_ssm library to be installed. Please install it with `pip install mamba_ssm`."
+        )
+    if not torch.cuda.is_available():
+        raise ValueError(
+            "This script is to be run with a CUDA device, as the original mamba_ssm model does not support cpu."
+        )
+    logger.info(f"Loading model from {mamba_checkpoint_path} based on config from {config_json_file}")
+    # Load weights and config from paths
+    original_state_dict = torch.load(mamba_checkpoint_path, map_location="cpu")
+    with open(config_json_file, "r", encoding="utf-8") as json_file:
+        original_ssm_config_dict = json.load(json_file)
+
+    # Convert the model
+    hf_model, tokenizer = convert_mamba_ssm_checkpoint_to_huggingface_model(
+        original_state_dict, original_ssm_config_dict
+    )
+
+    # Validate the conversion
+    validate_converted_model(original_state_dict, original_ssm_config_dict, hf_model, tokenizer)
+
+    logger.info(f"Model converted successfully. Saving model to {output_dir}")
+
+    # Save new model to pytorch_dump_path
+    hf_model.save_pretrained(output_dir)
+    tokenizer.save_pretrained(output_dir)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "-i",
+        "--mamba_checkpoint_file",
+        type=str,
+        required=True,
+        help="Path to a `pytorch_model.bin` mamba_ssm checkpoint file to be converted.",
+    )
+    parser.add_argument(
+        "-c",
+        "--config_json_file",
+        type=str,
+        required=True,
+        help="Path to a `config.json` file corresponding to a MambaConfig of the original mamba_ssm model.",
+    )
+    parser.add_argument(
+        "-o", "--output_dir", type=str, required=True, help="Path to directory to save the converted output model to."
+    )
+    args = parser.parse_args()
+
+    convert_mamba_checkpoint_file_to_huggingface_model_file(
+        args.mamba_checkpoint_file, args.config_json_file, args.output_dir
+    )