mlx-examples/llms/mlx_lm/models/deepseek.py

from dataclasses import dataclass
from typing import Any, Dict, Optional

import mlx.core as mx
import mlx.nn as nn

from .base import BaseModelArgs, create_attention_mask
from .switch_layers import SwitchGLU


@dataclass
class ModelArgs(BaseModelArgs):
    model_type: str = "deepseek"
    vocab_size: int = 102400
    hidden_size: int = 4096
    intermediate_size: int = 11008
    moe_intermediate_size: int = 1407
    num_hidden_layers: int = 30
    num_attention_heads: int = 32
    num_key_value_heads: int = 32
    n_shared_experts: Optional[int] = None
    n_routed_experts: Optional[int] = None
    num_experts_per_tok: Optional[int] = None
    moe_layer_freq: int = 1
    first_k_dense_replace: int = 0
    max_position_embeddings: int = 2048
    rms_norm_eps: float = 1e-6
    rope_theta: float = 10000.0
    rope_scaling: Optional[Dict] = None
    attention_bias: bool = False


class DeepseekAttention(nn.Module):
    def __init__(self, config: ModelArgs):
        super().__init__()
        self.config = config
        self.hidden_size = config.hidden_size
        self.num_attention_heads = config.num_attention_heads
        self.num_kv_heads = config.num_key_value_heads
        self.head_dim = config.hidden_size // config.num_attention_heads
        self.scale = self.head_dim**-0.5

        attention_bias = getattr(config, "attention_bias", False)

        self.q_proj = nn.Linear(
            self.hidden_size,
            config.num_attention_heads * self.head_dim,
            bias=attention_bias,
        )
        self.k_proj = nn.Linear(
            self.hidden_size,
            config.num_key_value_heads * self.head_dim,
            bias=attention_bias,
        )
        self.v_proj = nn.Linear(
            self.hidden_size,
            config.num_key_value_heads * self.head_dim,
            bias=attention_bias,
        )
        self.o_proj = nn.Linear(
            self.hidden_size,
            config.num_attention_heads * self.head_dim,
            bias=attention_bias,
        )

        rope_scale = 1.0
        if config.rope_scaling and config.rope_scaling["type"] == "linear":
            assert isinstance(config.rope_scaling["factor"], float)
            rope_scale = 1 / config.rope_scaling["factor"]
        self.rope = nn.RoPE(
            self.head_dim,
            base=config.rope_theta,
            scale=rope_scale,
        )

    def __call__(
        self,
        x: mx.array,
        mask: Optional[mx.array] = None,
        cache: Optional[Any] = None,
    ) -> mx.array:
        B, L, _ = x.shape

        queries, keys, values = self.q_proj(x), self.k_proj(x), self.v_proj(x)

        queries = queries.reshape(B, L, self.num_attention_heads, -1).transpose(
            0, 2, 1, 3
        )
        keys = keys.reshape(B, L, self.num_kv_heads, -1).transpose(0, 2, 1, 3)
        values = values.reshape(B, L, self.num_kv_heads, -1).transpose(0, 2, 1, 3)

        if cache is not None:
            queries = self.rope(queries, offset=cache.offset)
            keys = self.rope(keys, offset=cache.offset)
            keys, values = cache.update_and_fetch(keys, values)
        else:
            queries = self.rope(queries)
            keys = self.rope(keys)

        output = mx.fast.scaled_dot_product_attention(
            queries, keys, values, scale=self.scale, mask=mask
        )
        output = output.transpose(0, 2, 1, 3).reshape(B, L, -1)
        return self.o_proj(output)


class DeepseekMLP(nn.Module):
    def __init__(
        self,
        config: ModelArgs,
        hidden_size: Optional[int] = None,
        intermediate_size: Optional[int] = None,
    ):
        super().__init__()
        self.config = config
        self.hidden_size = hidden_size or config.hidden_size
        self.intermediate_size = intermediate_size or config.intermediate_size
        self.gate_proj = nn.Linear(self.hidden_size, self.intermediate_size, bias=False)
        self.up_proj = nn.Linear(self.hidden_size, self.intermediate_size, bias=False)
        self.down_proj = nn.Linear(self.intermediate_size, self.hidden_size, bias=False)
        self.act_fn = nn.silu

    def __call__(self, x: mx.array) -> mx.array:
        return self.down_proj(self.act_fn(self.gate_proj(x)) * self.up_proj(x))


class MoEGate(nn.Module):
    def __init__(self, config: ModelArgs):
        super().__init__()
        self.config = config
        self.top_k = config.num_experts_per_tok
        self.n_routed_experts = config.n_routed_experts
        self.weight = mx.zeros((self.n_routed_experts, config.hidden_size))

    def __call__(self, x):
        gates = x @ self.weight.T
        scores = mx.softmax(gates, axis=-1, precise=True)
        k = self.top_k
        inds = mx.stop_gradient(mx.argpartition(-scores, kth=k - 1, axis=-1)[..., :k])
        scores = mx.take_along_axis(scores, inds, axis=-1)
        return inds, scores


class DeepseekMoE(nn.Module):
    def __init__(self, config: ModelArgs):
        super().__init__()
        self.config = config
        self.switch_mlp = SwitchGLU(
            config.hidden_size, config.moe_intermediate_size, config.n_routed_experts
        )

        self.gate = MoEGate(config)
        if config.n_shared_experts is not None:
            intermediate_size = config.moe_intermediate_size * config.n_shared_experts
            self.shared_experts = DeepseekMLP(
                config=config, intermediate_size=intermediate_size
            )

    def __call__(self, x):
        inds, scores = self.gate(x)
        y = self.switch_mlp(x, inds)
        y = (y * scores[..., None]).sum(axis=-2)
        if self.config.n_shared_experts is not None:
            y = y + self.shared_experts(x)

        return y


class DeepseekDecoderLayer(nn.Module):
    def __init__(self, config: ModelArgs, layer_idx: int):
        super().__init__()
        self.self_attn = DeepseekAttention(config)
        self.mlp = (
            DeepseekMoE(config)
            if (
                config.n_routed_experts is not None
                and layer_idx >= config.first_k_dense_replace
                and layer_idx % config.moe_layer_freq == 0
            )
            else DeepseekMLP(config)
        )
        self.input_layernorm = nn.RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.post_attention_layernorm = nn.RMSNorm(
            config.hidden_size, eps=config.rms_norm_eps
        )

    def __call__(
        self,
        x: mx.array,
        mask: Optional[mx.array] = None,
        cache: Optional[Any] = None,
    ) -> mx.array:
        r = self.self_attn(self.input_layernorm(x), mask, cache)
        h = x + r
        r = self.mlp(self.post_attention_layernorm(h))
        out = h + r
        return out


class DeepseekModel(nn.Module):
    def __init__(self, config: ModelArgs):
        super().__init__()
        self.config = config
        self.embed_tokens = nn.Embedding(config.vocab_size, config.hidden_size)
        self.layers = [
            DeepseekDecoderLayer(config, idx) for idx in range(config.num_hidden_layers)
        ]
        self.norm = nn.RMSNorm(config.hidden_size, eps=config.rms_norm_eps)

    def __call__(
        self,
        x: mx.array,
        cache: Optional[Any] = None,
    ) -> mx.array:
        h = self.embed_tokens(x)
        mask = create_attention_mask(h, cache)

        if cache is None:
            cache = [None] * len(self.layers)

        for layer, c in zip(self.layers, cache):
            h = layer(h, mask, c)

        return self.norm(h)


class Model(nn.Module):
    def __init__(self, config: ModelArgs):
        super().__init__()
        self.args = config
        self.model_type = config.model_type
        self.model = DeepseekModel(config)
        self.lm_head = nn.Linear(config.hidden_size, config.vocab_size, bias=False)

    def __call__(
        self,
        inputs: mx.array,
        cache: Optional[Any] = None,
    ):
        out = self.model(inputs, cache)
        return self.lm_head(out)

    def sanitize(self, weights):
        for l in range(self.args.num_hidden_layers):
            prefix = f"model.layers.{l}"
            for m in ["gate_proj", "down_proj", "up_proj"]:
                for k in ["weight", "scales", "biases"]:
                    if f"{prefix}.mlp.experts.0.{m}.{k}" in weights:
                        to_join = [
                            weights.pop(f"{prefix}.mlp.experts.{e}.{m}.{k}")
                            for e in range(self.args.n_routed_experts)
                        ]
                        weights[f"{prefix}.mlp.switch_mlp.{m}.{k}"] = mx.stack(to_join)
        return weights

    @property
    def layers(self):
        return self.model.layers