utils.py

# Copyright © 2023-2024 Apple Inc.

import contextlib
import copy
import glob
import importlib
import json
import logging
import shutil
import time
from pathlib import Path
from textwrap import dedent
from typing import Any, Callable, Dict, Generator, List, Optional, Tuple, Type, Union

import mlx.core as mx
import mlx.nn as nn
from huggingface_hub import snapshot_download
from mlx.utils import tree_flatten, tree_reduce
from transformers import PreTrainedTokenizer

# Local imports
from .models import cache
from .sample_utils import make_logits_processors, make_sampler
from .tokenizer_utils import TokenizerWrapper, load_tokenizer
from .tuner.utils import dequantize as dequantize_model
from .tuner.utils import load_adapters

# Constants
MODEL_REMAPPING = {
    "mistral": "llama",  # mistral is compatible with llama
    "phi-msft": "phixtral",
    "falcon_mamba": "mamba",
}

MAX_FILE_SIZE_GB = 5

# A stream on the default device just for generation
generation_stream = mx.new_stream(mx.default_device())


class ModelNotFoundError(Exception):
    def __init__(self, message):
        self.message = message
        super().__init__(self.message)


@contextlib.contextmanager
def wired_limit(model: nn.Module, streams: Optional[List[mx.Stream]] = None):
    """
    A context manager to temporarily change the wired limit.

    Note, the wired limit should not be changed during an async eval.  If an
    async eval could be running pass in the streams to synchronize with prior
    to exiting the context manager.
    """
    model_bytes = tree_reduce(
        lambda acc, x: acc + x.nbytes if isinstance(x, mx.array) else acc, model, 0
    )
    max_rec_size = mx.metal.device_info()["max_recommended_working_set_size"]
    if model_bytes > 0.9 * max_rec_size:
        model_mb = model_bytes // 2**20
        max_rec_mb = max_rec_size // 2**20
        print(
            f"[WARNING] Generating with a model that requires {model_mb} MB "
            f"which is close to the maximum recommended size of {max_rec_mb} "
            "MB. This can be slow. See the documentation for possible work-arounds: "
            "https://github.com/ml-explore/mlx-examples/tree/main/llms#large-models"
        )
    old_limit = mx.metal.set_wired_limit(max_rec_size)
    try:
        yield None
    finally:
        if streams is not None:
            for s in streams:
                mx.synchronize(s)
        else:
            mx.synchronize()
        mx.metal.set_wired_limit(old_limit)


def _get_classes(config: dict):
    """
    Retrieve the model and model args classes based on the configuration.

    Args:
        config (dict): The model configuration.

    Returns:
        A tuple containing the Model class and the ModelArgs class.
    """
    model_type = config["model_type"]
    model_type = MODEL_REMAPPING.get(model_type, model_type)
    try:
        arch = importlib.import_module(f"mlx_lm.models.{model_type}")
    except ImportError:
        msg = f"Model type {model_type} not supported."
        logging.error(msg)
        raise ValueError(msg)

    return arch.Model, arch.ModelArgs


def get_model_path(path_or_hf_repo: str, revision: Optional[str] = None) -> Path:
    """
    Ensures the model is available locally. If the path does not exist locally,
    it is downloaded from the Hugging Face Hub.

    Args:
        path_or_hf_repo (str): The local path or Hugging Face repository ID of the model.
        revision (str, optional): A revision id which can be a branch name, a tag, or a commit hash.

    Returns:
        Path: The path to the model.
    """
    model_path = Path(path_or_hf_repo)
    if not model_path.exists():
        try:
            model_path = Path(
                snapshot_download(
                    repo_id=path_or_hf_repo,
                    revision=revision,
                    allow_patterns=[
                        "*.json",
                        "*.safetensors",
                        "*.py",
                        "tokenizer.model",
                        "*.tiktoken",
                        "*.txt",
                    ],
                )
            )
        except:
            raise ModelNotFoundError(
                f"Model not found for path or HF repo: {path_or_hf_repo}.\n"
                "Please make sure you specified the local path or Hugging Face"
                " repo id correctly.\nIf you are trying to access a private or"
                " gated Hugging Face repo, make sure you are authenticated:\n"
                "https://huggingface.co/docs/huggingface_hub/en/guides/cli#huggingface-cli-login"
            ) from None
    return model_path


def maybe_quantize_kv_cache(prompt_cache, quantized_kv_start, kv_group_size, kv_bits):
    if (
        kv_bits is not None
        and not isinstance(prompt_cache[0], cache.QuantizedKVCache)
        and prompt_cache[0].offset > quantized_kv_start
    ):
        for i in range(len(prompt_cache)):
            prompt_cache[i] = prompt_cache[i].to_quantized(
                group_size=kv_group_size, bits=kv_bits
            )


def generate_step(
    prompt: mx.array,
    model: nn.Module,
    temp: float = 0.0,
    repetition_penalty: Optional[float] = None,
    repetition_context_size: Optional[int] = 20,
    top_p: float = 1.0,
    min_p: float = 0.0,
    min_tokens_to_keep: int = 1,
    prefill_step_size: int = 512,
    max_kv_size: Optional[int] = None,
    prompt_cache: Optional[Any] = None,
    logit_bias: Optional[Dict[int, float]] = None,
    logits_processors: Optional[List[Callable[[mx.array, mx.array], mx.array]]] = None,
    kv_bits: Optional[int] = None,
    kv_group_size: int = 64,
    quantized_kv_start: int = 0,
) -> Generator[Tuple[mx.array, mx.array], None, None]:
    """
    A generator producing token ids based on the given prompt from the model.

    Args:
        prompt (mx.array): The input prompt.
        model (nn.Module): The model to use for generation.
        temp (float): The temperature for sampling, if 0 the argmax is used.
          Default: ``0``.
        repetition_penalty (float, optional): The penalty factor for repeating
          tokens.
        repetition_context_size (int, optional): The number of tokens to
          consider for repetition penalty. Default: ``20``.
        top_p (float, optional): Nulceus sampling, higher means model considers
          more less likely words.
        min_p (float, optional): The minimum value (scaled by the top token's
          probability) that a token probability must have to be considered.
        min_tokens_to_keep (int, optional): Minimum number of tokens that cannot
          be filtered by min_p sampling.
        prefill_step_size (int): Step size for processing the prompt.
        max_kv_size (int, optional): Maximum size of the key-value cache. Old
          entries (except the first 4 tokens) will be overwritten.
        prompt_cache (List[Any], optional): A pre-computed prompt cache. Note, if
          provided, the cache will be updated in place.
        logit_bias (dictionary, optional): Additive logit bias.
        logits_processors (List[Callable[[mx.array, mx.array], mx.array]], optional):
            A list of functions that take tokens and logits and return the processed
            logits. Default: ``None``.
        kv_bits (int, optional): Number of bits to use for KV cache quantization.
            None implies no cache quantization. Default: ``None``.
        kv_group_size (int): Group size for KV cache quantization. Default: ``64``.
        quantized_kv_start (int): Step to begin using a quantized KV cache.
            when ``kv_bits`` is non-None. Default: ``0``.

    Yields:
        Tuple[mx.array, mx.array]: One token and a vector of log probabilities.
    """

    y = prompt
    tokens = None

    # Create the KV cache for generation
    if prompt_cache is None:
        prompt_cache = cache.make_prompt_cache(
            model,
            max_kv_size=max_kv_size,
        )
    elif len(prompt_cache) != len(model.layers):
        raise ValueError("Wrong number of layers in the prompt cache.")

    sampler = make_sampler(temp, top_p, min_p, min_tokens_to_keep)
    logits_processors = logits_processors or []
    logits_processors.extend(
        make_logits_processors(logit_bias, repetition_penalty, repetition_context_size)
    )

    def _step(y):
        with mx.stream(generation_stream):
            logits = model(y[None], cache=prompt_cache)
            logits = logits[:, -1, :]

            if logits_processors:
                nonlocal tokens
                tokens = mx.concat([tokens, y]) if tokens is not None else y

                for processor in logits_processors:
                    logits = processor(tokens, logits)

            maybe_quantize_kv_cache(
                prompt_cache, quantized_kv_start, kv_group_size, kv_bits
            )

            logprobs = logits - mx.logsumexp(logits, keepdims=True)
            y = sampler(logprobs)
            return y, logprobs.squeeze(0)

    while y.size > prefill_step_size:
        model(y[:prefill_step_size][None], cache=prompt_cache)
        mx.eval([c.state for c in prompt_cache])
        y = y[prefill_step_size:]
        mx.metal.clear_cache()

    y, logprobs = _step(y)

    mx.async_eval(y, logprobs)
    n = 0
    while True:
        next_y, next_logprobs = _step(y)
        mx.async_eval(next_y, next_logprobs)
        yield y.item(), logprobs
        if n % 256 == 0:
            mx.metal.clear_cache()
        n += 1
        y, logprobs = next_y, next_logprobs


def stream_generate(
    model: nn.Module,
    tokenizer: Union[PreTrainedTokenizer, TokenizerWrapper],
    prompt: Union[str, List[int]],
    max_tokens: int = 100,
    **kwargs,
) -> Generator[Tuple[str, int, mx.array], None, None]:
    """
    A generator producing text based on the given prompt from the model.

    Args:
        model (nn.Module): The model to use for generation.
        tokenizer (PreTrainedTokenizer): The tokenizer.
        prompt (Union[str, List[int]]): The input prompt string or integer tokens.
        max_tokens (int): The maximum number of tokens. Default: ``100``.
        kwargs: The remaining options get passed to :func:`generate_step`.
          See :func:`generate_step` for more details.

    Yields:
        Tuple[str, int, mx.array]:
            The next text segment, token, and vector of log probabilities.
    """
    if not isinstance(tokenizer, TokenizerWrapper):
        tokenizer = TokenizerWrapper(tokenizer)

    prompt_tokens = mx.array(
        prompt if isinstance(prompt, list) else tokenizer.encode(prompt)
    )
    detokenizer = tokenizer.detokenizer

    with wired_limit(model, [generation_stream]):
        detokenizer.reset()
        for n, (token, logits) in zip(
            range(max_tokens),
            generate_step(prompt_tokens, model, **kwargs),
        ):
            if token == tokenizer.eos_token_id:
                break

            detokenizer.add_token(token)

            if n == (max_tokens - 1):
                break

            yield detokenizer.last_segment, token, logits

        detokenizer.finalize()
        yield detokenizer.last_segment, token, logits


def generate(
    model: nn.Module,
    tokenizer: Union[PreTrainedTokenizer, TokenizerWrapper],
    prompt: str,
    max_tokens: int = 100,
    verbose: bool = False,
    formatter: Optional[Callable] = None,
    **kwargs,
) -> str:
    """
    Generate a complete response from the model.

    Args:
       model (nn.Module): The language model.
       tokenizer (PreTrainedTokenizer): The tokenizer.
       prompt (str): The string prompt.
       max_tokens (int): The maximum number of tokens. Default: ``100``.
       verbose (bool): If ``True``, print tokens and timing information.
           Default: ``False``.
       formatter (Optional[Callable]): A function which takes a token and a
           probability and displays it.
       kwargs: The remaining options get passed to :func:`generate_step`.
          See :func:`generate_step` for more details.
    """
    if not isinstance(tokenizer, TokenizerWrapper):
        tokenizer = TokenizerWrapper(tokenizer)

    if verbose:
        print("=" * 10)
        print("Prompt:", prompt)

    prompt_tokens = mx.array(tokenizer.encode(prompt))
    detokenizer = tokenizer.detokenizer

    with wired_limit(model, [generation_stream]):
        tic = time.perf_counter()
        detokenizer.reset()
        for n, (token, logprobs) in zip(
            range(max_tokens),
            generate_step(prompt_tokens, model, **kwargs),
        ):
            if n == 0:
                prompt_time = time.perf_counter() - tic
                tic = time.perf_counter()
            if token == tokenizer.eos_token_id:
                break
            detokenizer.add_token(token)

            if verbose:
                if formatter:
                    # We have to finalize so that the prob corresponds to the last segment
                    detokenizer.finalize()
                    prob = mx.exp(logprobs[token]).item()
                    formatter(detokenizer.last_segment, prob)
                else:
                    print(detokenizer.last_segment, end="", flush=True)

        token_count = n + 1
        detokenizer.finalize()

        if verbose:
            gen_time = time.perf_counter() - tic
            print(detokenizer.last_segment, flush=True)
            print("=" * 10)
            if token_count == 0:
                print("No tokens generated for this prompt")
                return
            prompt_tps = prompt_tokens.size / prompt_time
            gen_tps = (token_count - 1) / gen_time
            print(
                f"Prompt: {prompt_tokens.size} tokens, {prompt_tps:.3f} tokens-per-sec"
            )
            print(f"Generation: {token_count} tokens, {gen_tps:.3f} tokens-per-sec")
            peak_mem = mx.metal.get_peak_memory() / 1e9
            print(f"Peak memory: {peak_mem:.3f} GB")

        return detokenizer.text


def load_config(model_path: Path) -> dict:
    try:
        with open(model_path / "config.json", "r") as f:
            config = json.load(f)
    except FileNotFoundError:
        logging.error(f"Config file not found in {model_path}")
        raise
    return config


def load_model(
    model_path: Path,
    lazy: bool = False,
    model_config: dict = {},
    get_model_classes: Callable[[dict], Tuple[Type[nn.Module], Type]] = _get_classes,
) -> nn.Module:
    """
    Load and initialize the model from a given path.

    Args:
        model_path (Path): The path to load the model from.
        lazy (bool): If False eval the model parameters to make sure they are
            loaded in memory before returning, otherwise they will be loaded
            when needed. Default: ``False``
        model_config (dict, optional): Configuration parameters for the model.
            Defaults to an empty dictionary.
        get_model_classes (Callable[[dict], Tuple[Type[nn.Module], Type]], optional):
            A function that returns the model class and model args class given a config.
            Defaults to the _get_classes function.

    Returns:
        nn.Module: The loaded and initialized model.

    Raises:
        FileNotFoundError: If the weight files (.safetensors) are not found.
        ValueError: If the model class or args class are not found or cannot be instantiated.
    """

    config = load_config(model_path)
    config.update(model_config)

    weight_files = glob.glob(str(model_path / "model*.safetensors"))

    if not weight_files:
        # Try weight for back-compat
        weight_files = glob.glob(str(model_path / "weight*.safetensors"))

    if not weight_files:
        logging.error(f"No safetensors found in {model_path}")
        raise FileNotFoundError(f"No safetensors found in {model_path}")

    weights = {}
    for wf in weight_files:
        weights.update(mx.load(wf))

    model_class, model_args_class = get_model_classes(config=config)

    model_args = model_args_class.from_dict(config)
    model = model_class(model_args)

    if hasattr(model, "sanitize"):
        weights = model.sanitize(weights)

    if (quantization := config.get("quantization", None)) is not None:
        # Handle legacy models which may not have everything quantized
        def class_predicate(p, m):
            if not hasattr(m, "to_quantized"):
                return False
            return f"{p}.scales" in weights

        nn.quantize(
            model,
            **quantization,
            class_predicate=class_predicate,
        )

    model.load_weights(list(weights.items()))

    if not lazy:
        mx.eval(model.parameters())

    model.eval()
    return model


def load(
    path_or_hf_repo: str,
    tokenizer_config={},
    model_config={},
    adapter_path: Optional[str] = None,
    lazy: bool = False,
) -> Tuple[nn.Module, TokenizerWrapper]:
    """
    Load the model and tokenizer from a given path or a huggingface repository.

    Args:
        path_or_hf_repo (Path): The path or the huggingface repository to load the model from.
        tokenizer_config (dict, optional): Configuration parameters specifically for the tokenizer.
            Defaults to an empty dictionary.
        model_config(dict, optional): Configuration parameters specifically for the model.
            Defaults to an empty dictionary.
        adapter_path (str, optional): Path to the LoRA adapters. If provided, applies LoRA layers
            to the model. Default: ``None``.
        lazy (bool): If False eval the model parameters to make sure they are
            loaded in memory before returning, otherwise they will be loaded
            when needed. Default: ``False``
    Returns:
        Tuple[nn.Module, TokenizerWrapper]: A tuple containing the loaded model and tokenizer.

    Raises:
        FileNotFoundError: If config file or safetensors are not found.
        ValueError: If model class or args class are not found.
    """
    model_path = get_model_path(path_or_hf_repo)

    model = load_model(model_path, lazy, model_config)
    if adapter_path is not None:
        model = load_adapters(model, adapter_path)
        model.eval()
    tokenizer = load_tokenizer(model_path, tokenizer_config)

    return model, tokenizer


def fetch_from_hub(
    model_path: Path, lazy: bool = False
) -> Tuple[nn.Module, dict, PreTrainedTokenizer]:
    model = load_model(model_path, lazy)
    config = load_config(model_path)
    tokenizer = load_tokenizer(model_path)
    return model, config, tokenizer


def make_shards(weights: dict, max_file_size_gb: int = MAX_FILE_SIZE_GB) -> list:
    """
    Splits the weights into smaller shards.

    Args:
        weights (dict): Model weights.
        max_file_size_gb (int): Maximum size of each shard in gigabytes.

    Returns:
        list: List of weight shards.
    """
    max_file_size_bytes = max_file_size_gb << 30
    shards = []
    shard, shard_size = {}, 0
    for k, v in weights.items():
        if shard_size + v.nbytes > max_file_size_bytes:
            shards.append(shard)
            shard, shard_size = {}, 0
        shard[k] = v
        shard_size += v.nbytes
    shards.append(shard)
    return shards


def upload_to_hub(path: str, upload_repo: str, hf_path: str):
    """
    Uploads the model to Hugging Face hub.

    Args:
        path (str): Local path to the model.
        upload_repo (str): Name of the HF repo to upload to.
        hf_path (str): Path to the original Hugging Face model.
    """
    import os

    from huggingface_hub import HfApi, ModelCard, logging

    from . import __version__

    card = ModelCard.load(hf_path)
    card.data.tags = ["mlx"] if card.data.tags is None else card.data.tags + ["mlx"]
    card.data.base_model = hf_path
    card.text = dedent(
        f"""
        # {upload_repo}

        The Model [{upload_repo}](https://huggingface.co/{upload_repo}) was
        converted to MLX format from [{hf_path}](https://huggingface.co/{hf_path})
        using mlx-lm version **{__version__}**.

        ## Use with mlx

        ```bash
        pip install mlx-lm
        ```

        ```python
        from mlx_lm import load, generate

        model, tokenizer = load("{upload_repo}")

        prompt="hello"

        if hasattr(tokenizer, "apply_chat_template") and tokenizer.chat_template is not None:
            messages = [{{"role": "user", "content": prompt}}]
            prompt = tokenizer.apply_chat_template(
                messages, tokenize=False, add_generation_prompt=True
            )

        response = generate(model, tokenizer, prompt=prompt, verbose=True)
        ```
        """
    )
    card.save(os.path.join(path, "README.md"))

    logging.set_verbosity_info()

    api = HfApi()
    api.create_repo(repo_id=upload_repo, exist_ok=True)
    api.upload_folder(
        folder_path=path,
        repo_id=upload_repo,
        repo_type="model",
        multi_commits=True,
        multi_commits_verbose=True,
    )
    print(f"Upload successful, go to https://huggingface.co/{upload_repo} for details.")


def save_weights(
    save_path: Union[str, Path],
    weights: Dict[str, Any],
    *,
    donate_weights: bool = False,
) -> None:
    """Save model weights into specified directory."""
    if isinstance(save_path, str):
        save_path = Path(save_path)
    save_path.mkdir(parents=True, exist_ok=True)

    shards = make_shards(weights)
    shards_count = len(shards)
    shard_file_format = (
        "model-{:05d}-of-{:05d}.safetensors"
        if shards_count > 1
        else "model.safetensors"
    )

    total_size = sum(v.nbytes for v in weights.values())
    index_data = {"metadata": {"total_size": total_size}, "weight_map": {}}

    # Write the weights and make sure no references are kept other than the
    # necessary ones
    if donate_weights:
        weights.clear()
        del weights

    for i in range(len(shards)):
        shard = shards[i]
        shards[i] = None
        shard_name = shard_file_format.format(i + 1, shards_count)
        shard_path = save_path / shard_name

        mx.save_safetensors(str(shard_path), shard, metadata={"format": "mlx"})

        for weight_name in shard.keys():
            index_data["weight_map"][weight_name] = shard_name
        del shard

    index_data["weight_map"] = {
        k: index_data["weight_map"][k] for k in sorted(index_data["weight_map"])
    }

    with open(save_path / "model.safetensors.index.json", "w") as f:
        json.dump(
            index_data,
            f,
            indent=4,
        )


def quantize_model(
    model: nn.Module, config: dict, q_group_size: int, q_bits: int
) -> Tuple:
    """
    Applies quantization to the model weights.

    Args:
        model (nn.Module): The model to be quantized.
        config (dict): Model configuration.
        q_group_size (int): Group size for quantization.
        q_bits (int): Bits per weight for quantization.

    Returns:
        Tuple: Tuple containing quantized weights and config.
    """
    quantized_config = copy.deepcopy(config)
    nn.quantize(model, q_group_size, q_bits)
    quantized_config["quantization"] = {"group_size": q_group_size, "bits": q_bits}
    # support hf model tree #957
    quantized_config["quantization_config"] = quantized_config["quantization"]
    quantized_weights = dict(tree_flatten(model.parameters()))

    return quantized_weights, quantized_config


def save_config(
    config: dict,
    config_path: Union[str, Path],
) -> None:
    """Save the model configuration to the ``config_path``.

    The final configuration will be sorted before saving for better readability.

    Args:
        config (dict): The model configuration.
        config_path (Union[str, Path]): Model configuration file path.
    """
    # Clean unused keys
    config.pop("_name_or_path", None)

    # sort the config for better readability
    config = dict(sorted(config.items()))

    # write the updated config to the config_path (if provided)
    with open(config_path, "w") as fid:
        json.dump(config, fid, indent=4)


def convert(
    hf_path: str,
    mlx_path: str = "mlx_model",
    quantize: bool = False,
    q_group_size: int = 64,
    q_bits: int = 4,
    dtype: str = "float16",
    upload_repo: str = None,
    revision: Optional[str] = None,
    dequantize: bool = False,
):
    # Check the save path is empty
    if isinstance(mlx_path, str):
        mlx_path = Path(mlx_path)

    if mlx_path.exists():
        raise ValueError(
            f"Cannot save to the path {mlx_path} as it already exists."
            " Please delete the file/directory or specify a new path to save to."
        )

    print("[INFO] Loading")
    model_path = get_model_path(hf_path, revision=revision)
    model, config, tokenizer = fetch_from_hub(model_path, lazy=True)

    weights = dict(tree_flatten(model.parameters()))
    dtype = getattr(mx, dtype)
    weights = {k: v.astype(dtype) for k, v in weights.items()}

    if quantize and dequantize:
        raise ValueError("Choose either quantize or dequantize, not both.")

    if quantize:
        print("[INFO] Quantizing")
        model.load_weights(list(weights.items()))
        weights, config = quantize_model(model, config, q_group_size, q_bits)

    if dequantize:
        print("[INFO] Dequantizing")
        model = dequantize_model(model)
        weights = dict(tree_flatten(model.parameters()))

    del model
    save_weights(mlx_path, weights, donate_weights=True)

    py_files = glob.glob(str(model_path / "*.py"))
    for file in py_files:
        shutil.copy(file, mlx_path)

    tokenizer.save_pretrained(mlx_path)

    save_config(config, config_path=mlx_path / "config.json")

    if upload_repo is not None:
        upload_to_hub(mlx_path, upload_repo, hf_path)