utils.py

# Copyright © 2023-2024 Apple Inc.

import contextlib
import copy
import functools
import glob
import importlib
import json
import logging
import os
import shutil
import time
from dataclasses import dataclass
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

if os.getenv("MLXLM_USE_MODELSCOPE", "False").lower() == "true":
    try:
        from modelscope import snapshot_download
    except ImportError:
        raise ImportError(
            "Please run `pip install modelscope` to activate the ModelScope."
        )
else:
    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, nparams

# 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)


@dataclass
class GenerationResponse:
    """
    The output of :func:`stream_generate`.

    Args:
        text (str): The next segment of decoded text. This can be an empty string.
        token (int): The next token.
        logprobs (mx.array): A vector of log probabilities.
        prompt_tokens (int): The number of tokens in the prompt.
        prompt_tps (float): The prompt processing tokens-per-second.
        generation_tokens (int): The number of generated tokens.
        generation_tps (float): The tokens-per-second for generation.
        peak_memory (float): The peak memory used so far in GB.
        finish_reason (str): The reason the response is being sent: "length", "stop" or `None`
    """

    text: str
    token: int
    logprobs: mx.array
    prompt_tokens: int
    prompt_tps: float
    generation_tokens: int
    generation_tps: float
    peak_memory: float
    finish_reason: Optional[str] = None


@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 compute_bits_per_weight(model):
    model_bytes = tree_reduce(
        lambda acc, x: acc + x.nbytes if isinstance(x, mx.array) else acc, model, 0
    )
    leaf_modules = tree_flatten(
        model.leaf_modules(), is_leaf=lambda m: isinstance(m, nn.Module)
    )
    model_params = sum(nparams(m) for _, m in leaf_modules)
    return model_bytes * 8 / model_params


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(
                    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)):
            if isinstance(prompt_cache[i], cache.KVCache):
                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,
    *,
    max_tokens: int = 256,
    sampler: Optional[Callable[mx.array, mx.array]] = None,
    logits_processors: Optional[List[Callable[[mx.array, mx.array], mx.array]]] = None,
    max_kv_size: Optional[int] = None,
    prompt_cache: Optional[Any] = None,
    prefill_step_size: int = 512,
    kv_bits: Optional[int] = None,
    kv_group_size: int = 64,
    quantized_kv_start: int = 0,
    prompt_progress_callback: Optional[Callable[int, int]] = None,
) -> 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.
        max_tokens (int): The maximum number of tokens. Use``-1`` for an infinite
          generator. Default: ``256``.
        sampler (Callable[mx.array, mx.array], optional): A sampler for sampling a
          token from a vector of log probabilities. Default: ``None``.
        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``.
        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.
        prefill_step_size (int): Step size for processing the prompt.
        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``.
        prompt_prorgress_callback (Callable[int, int]): A call-back which takes the
           prompt tokens processed so far and the total number of prompt tokens.

    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.")

    prompt_progress_callback = prompt_progress_callback or (lambda *_: None)

    quantize_cache_fn = functools.partial(
        maybe_quantize_kv_cache,
        quantized_kv_start=quantized_kv_start,
        kv_group_size=kv_group_size,
        kv_bits=kv_bits,
    )

    sampler = sampler or (lambda x: mx.argmax(x, axis=-1))

    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)

            quantize_cache_fn(prompt_cache)

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

    with mx.stream(generation_stream):
        total_prompt_tokens = y.size
        prompt_processed_tokens = 0
        while y.size > prefill_step_size:
            model(y[:prefill_step_size][None], cache=prompt_cache)
            quantize_cache_fn(prompt_cache)
            mx.eval([c.state for c in prompt_cache])
            prompt_progress_callback(prompt_processed_tokens, total_prompt_tokens)
            prompt_processed_tokens += prefill_step_size
            y = y[prefill_step_size:]
            mx.metal.clear_cache()

        y, logprobs = _step(y)

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


def speculative_generate_step(
    prompt: mx.array,
    model: nn.Module,
    draft_model: nn.Module,
    *,
    num_draft_tokens=2,
    max_tokens: int = 256,
    sampler: Optional[Callable[mx.array, mx.array]] = None,
    logits_processors: Optional[List[Callable[[mx.array, mx.array], mx.array]]] = None,
    prompt_cache: Optional[Any] = None,
    prefill_step_size: int = 512,
    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.
        draft_model (nn.Module): The draft model for speculative decoding.
        num_draft_tokens (int, optional): The number of draft tokens for
          speculative decoding. Default: ``2``.
        max_tokens (int): The maximum number of tokens. Use``-1`` for an infinite
          generator. Default: ``256``.
        sampler (Callable[mx.array, mx.array], optional): A sampler for sampling a
          token from a vector of log probabilities. Default: ``None``.
        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``.
        prompt_cache (List[Any], optional): A pre-computed prompt cache. Note, if
          provided, the cache will be updated in place. The cache must be trimmable.
        prefill_step_size (int): Step size for processing the prompt.
        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:
        model_cache = cache.make_prompt_cache(model)
        draft_cache = cache.make_prompt_cache(draft_model)
    elif len(prompt_cache) != (len(model.layers) + len(draft_model.layers)):
        raise ValueError("Wrong number of layers in the prompt cache.")
    else:
        model_cache = prompt_cache[: len(model.layers)]
        draft_cache = prompt_cache[len(model.layers) :]

    sampler = sampler or (lambda x: mx.argmax(x, axis=-1))

    quantize_cache_fn = functools.partial(
        maybe_quantize_kv_cache,
        quantized_kv_start=quantized_kv_start,
        kv_group_size=kv_group_size,
        kv_bits=kv_bits,
    )

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

            quantize_cache_fn(cache)

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

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

    def _rewind_cache(num_draft, num_accept):
        cache.trim_prompt_cache(model_cache, num_draft - num_accept)
        cache.trim_prompt_cache(draft_cache, max(num_draft - num_accept - 1, 0))

    def _draft_generate(y, num_draft):
        if num_draft == 0:
            return mx.array([], mx.uint32)
        ys = []
        for _ in range(num_draft):
            y, _ = _step(draft_model, draft_cache, y)
            mx.async_eval(y)
            ys.append(y)
        return mx.concatenate(ys)

    with mx.stream(generation_stream):
        draft_y = _prefill(draft_model, draft_cache, y)
        y = _prefill(model, model_cache, y)

    ntoks = 0
    # Set these so the finally block doesn't raise
    num_draft = 0
    n = 0
    try:
        while True:
            num_draft = min(max_tokens - ntoks, num_draft_tokens)
            draft_tokens = _draft_generate(draft_y, num_draft)
            y = mx.concatenate([y, draft_tokens])

            tokens, logprobs = _step(model, model_cache, y, num_draft + 1)
            mx.eval(tokens, draft_tokens)
            draft_tokens = draft_tokens.tolist()
            tokens = tokens.tolist()
            n = 0
            while n < num_draft:
                tn, dtn, lpn = tokens[n], draft_tokens[n], logprobs[n]
                if tn != dtn:
                    break
                n += 1
                ntoks += 1
                yield tn, lpn
                if ntoks == max_tokens:
                    break
            if ntoks < max_tokens:
                ntoks += 1
                yield tokens[n], logprobs[n]

            if ntoks == max_tokens:
                break

            y = mx.array([tokens[n]], mx.uint32)
            draft_y = y

            # If we accpeted all the draft tokens, include the last
            # draft token in the next draft step since it hasn't been
            # processed yet by the draft model
            if n == num_draft:
                draft_y = mx.concatenate(
                    [mx.array(draft_tokens[-1:], mx.uint32), draft_y]
                )

            _rewind_cache(num_draft, n)
    finally:
        _rewind_cache(num_draft, n)


def stream_generate(
    model: nn.Module,
    tokenizer: Union[PreTrainedTokenizer, TokenizerWrapper],
    prompt: Union[str, mx.array, List[int]],
    draft_model: Optional[nn.Module] = None,
    **kwargs,
) -> Generator[GenerationResponse, 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, mx.array, List[int]]): The input prompt string or
          integer tokens.
        draft_model (Optional[nn.Module]): An optional draft model. If provided
          then speculative decoding is used. The draft model must use the same
          tokenizer as the main model. Default: ``None``.
        kwargs: The remaining options get passed to :func:`generate_step`.
          See :func:`generate_step` for more details.

    Yields:
        GenerationResponse: An instance containing the generated text segment and
            associated metadata. See :class:`GenerationResponse` for details.
    """
    if not isinstance(tokenizer, TokenizerWrapper):
        tokenizer = TokenizerWrapper(tokenizer)

    if not isinstance(prompt, mx.array):
        if isinstance(prompt, str):
            # Try to infer if special tokens are needed
            add_special_tokens = tokenizer.bos_token is None or not prompt.startswith(
                tokenizer.bos_token
            )
            prompt = tokenizer.encode(prompt, add_special_tokens=add_special_tokens)
        prompt = mx.array(prompt)

    detokenizer = tokenizer.detokenizer

    if draft_model is None:
        kwargs.pop("num_draft_tokens", None)
        token_generator = generate_step(prompt, model, **kwargs)
    else:
        kwargs.pop("max_kv_size", None)
        token_generator = speculative_generate_step(
            prompt, model, draft_model, **kwargs
        )
    with wired_limit(model, [generation_stream]):
        detokenizer.reset()
        tic = time.perf_counter()
        for n, (token, logprobs) in enumerate(token_generator):
            if n == 0:
                prompt_time = time.perf_counter() - tic
                prompt_tps = prompt.size / prompt_time
                tic = time.perf_counter()
            if token in tokenizer.eos_token_ids:
                break

            detokenizer.add_token(token)

            yield GenerationResponse(
                text=detokenizer.last_segment,
                token=token,
                logprobs=logprobs,
                prompt_tokens=prompt.size,
                prompt_tps=prompt_tps,
                generation_tokens=n + 1,
                generation_tps=(n + 1) / (time.perf_counter() - tic),
                peak_memory=mx.metal.get_peak_memory() / 1e9,
                finish_reason=None,
            )

        detokenizer.finalize()
        yield GenerationResponse(
            text=detokenizer.last_segment,
            token=token,
            logprobs=logprobs,
            prompt_tokens=prompt.size,
            prompt_tps=prompt_tps,
            generation_tokens=n + 1,
            generation_tps=(n + 1) / (time.perf_counter() - tic),
            peak_memory=mx.metal.get_peak_memory() / 1e9,
            finish_reason="stop" if token in tokenizer.eos_token_ids else "length",
        )


def generate(
    model: nn.Module,
    tokenizer: Union[PreTrainedTokenizer, TokenizerWrapper],
    prompt: Union[str, List[int]],
    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 (Union[str, List[int]]): The input prompt string or integer tokens.
       verbose (bool): If ``True``, print tokens and timing information.
           Default: ``False``.
       kwargs: The remaining options get passed to :func:`stream_generate`.
          See :func:`stream_generate` for more details.
    """
    if formatter is not None:
        print(
            "[Warning] Text formatting is deprecated and no longer used. "
            "The argument will be removed in a future version."
        )
    if verbose:
        print("=" * 10)

    text = ""
    for response in stream_generate(model, tokenizer, prompt, **kwargs):
        if verbose:
            print(response.text, end="", flush=True)
        text += response.text

    if verbose:
        print()
        print("=" * 10)
        if len(text) == 0:
            print("No text generated for this prompt")
            return
        print(
            f"Prompt: {response.prompt_tokens} tokens, "
            f"{response.prompt_tps:.3f} tokens-per-sec"
        )
        print(
            f"Generation: {response.generation_tokens} tokens, "
            f"{response.generation_tps:.3f} tokens-per-sec"
        )
        print(f"Peak memory: {response.peak_memory:.3f} GB")
    return 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,
    strict: bool = True,
    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``
        strict (bool): Whether or not to raise an exception if weights don't
            match. Default: ``True``
        model_config (dict, optional): 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 and strict:
        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:

        def class_predicate(p, m):
            # Handle custom per layer quantizations
            if p in config["quantization"]:
                return config["quantization"][p]
            if not hasattr(m, "to_quantized"):
                return False
            # Handle legacy models which may not have everything quantized
            return f"{p}.scales" in weights

        nn.quantize(
            model,
            group_size=quantization["group_size"],
            bits=quantization["bits"],
            class_predicate=class_predicate,
        )

    model.load_weights(list(weights.items()), strict=strict)

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

    model.eval()
    return model, config


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, config = load_model(model_path, lazy)
    if adapter_path is not None:
        model = load_adapters(model, adapter_path)
        model.eval()
    tokenizer = load_tokenizer(
        model_path, tokenizer_config, eos_token_ids=config.get("eos_token_id", None)
    )

    return model, tokenizer


def fetch_from_hub(
    model_path: Path, lazy: bool = False
) -> Tuple[nn.Module, dict, PreTrainedTokenizer]:
    model, config = load_model(model_path, lazy)
    tokenizer = load_tokenizer(
        model_path, eos_token_ids=config.get("eos_token_id", None)
    )
    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 tokenizer.chat_template is not None:
            messages = [{{"role": "user", "content": prompt}}]
            prompt = tokenizer.apply_chat_template(
                messages, 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_large_folder(
        folder_path=path,
        repo_id=upload_repo,
        repo_type="model",
    )
    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,
    quant_predicate: Optional[
        Callable[[str, nn.Module, dict], Union[bool, dict]]
    ] = None,
) -> 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.
        quant_predicate (Callable): A callable that decides how
            to quantize each layer based on the path.
            Accepts the layer `path`, the `module` and the model `config`.
            Returns either a bool to signify quantize/no quantize or
            a dict of quantization parameters to pass to `to_quantized`.

    Returns:
        Tuple: Tuple containing quantized weights and config.
    """
    quantized_config = copy.deepcopy(config)
    quantized_config["quantization"] = {"group_size": q_group_size, "bits": q_bits}

    # Add any custom quantization parameters to the config as we go
    def _class_predicate(p, m):
        bool_or_params = quant_predicate(p, m, config)
        quantized_config["quantization"][p] = bool_or_params
        return bool_or_params

    nn.quantize(
        model,
        q_group_size,
        q_bits,
        class_predicate=_class_predicate if quant_predicate else None,
    )
    # support hf model tree #957
    quantized_config["quantization_config"] = quantized_config["quantization"]
    quantized_weights = dict(tree_flatten(model.parameters()))

    bpw = compute_bits_per_weight(model)
    print(f"[INFO] Quantized model with {bpw:.3f} bits per weight.")

    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,
    quant_predicate: Optional[
        Callable[[str, nn.Module, dict], Union[bool, dict]]
    ] = None,
):
    # 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, quant_predicate=quant_predicate
        )

    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)