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

# Copyright © 2024 Apple Inc.

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

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

from .base import BaseModelArgs, create_attention_mask, scaled_dot_product_attention
from .rope_utils import initialize_rope


@dataclass
class ModelArgs(BaseModelArgs):
    model_type: str
    hidden_size: int
    num_layers: int
    intermediate_size: int
    num_attention_heads: int
    vocab_size: int
    rope_theta: float
    layer_norm_epsilon: float
    num_key_value_heads: int
    head_dim: Optional[int] = None
    max_position_embeddings: Optional[int] = None
    rope_traditional: bool = False
    rope_scaling: Optional[Dict[str, Union[float, str]]] = None
    tie_word_embeddings: bool = True
    attention_bias: bool = False
    mlp_bias: bool = False


class AttentionModule(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        dim = args.hidden_size
        self.n_heads = n_heads = args.num_attention_heads
        self.n_kv_heads = n_kv_heads = args.num_key_value_heads
        self.head_dim = head_dim = args.head_dim or (dim // n_heads)
        self.scale = head_dim**-0.5

        self.q_proj = nn.Linear(dim, n_heads * head_dim, bias=args.attention_bias)
        self.k_proj = nn.Linear(dim, n_kv_heads * head_dim, bias=args.attention_bias)
        self.v_proj = nn.Linear(dim, n_kv_heads * head_dim, bias=args.attention_bias)
        self.out_proj = nn.Linear(n_heads * head_dim, dim, bias=args.attention_bias)

        self.rope = initialize_rope(
            self.head_dim,
            args.rope_theta,
            args.rope_traditional,
            args.rope_scaling,
            args.max_position_embeddings,
        )

    def __call__(
        self, x: mx.array, mask: Optional[mx.array] = None, cache: Optional[Any] = None
    ) -> mx.array:
        B, L, D = x.shape
        q = self.q_proj(x).reshape(B, L, self.n_heads, -1).transpose(0, 2, 1, 3)
        k = self.k_proj(x).reshape(B, L, self.n_kv_heads, -1).transpose(0, 2, 1, 3)
        v = self.v_proj(x).reshape(B, L, self.n_kv_heads, -1).transpose(0, 2, 1, 3)

        if cache is not None:
            q = self.rope(q, offset=cache.offset)
            k = self.rope(k, offset=cache.offset)
            k, v = cache.update_and_fetch(k, v)
        else:
            q = self.rope(q)
            k = self.rope(k)

        out = scaled_dot_product_attention(
            q, k, v, cache=cache, scale=self.scale, mask=mask
        )
        out = out.transpose(0, 2, 1, 3).reshape(B, L, D)
        return self.out_proj(out)


class Attention(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        self.attention = AttentionModule(args)


class MLP(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        dim = args.hidden_size
        hidden_dim = args.intermediate_size
        self.c_fc_0 = nn.Linear(dim, hidden_dim, bias=args.mlp_bias)
        self.c_fc_1 = nn.Linear(dim, hidden_dim, bias=args.mlp_bias)
        self.c_proj = nn.Linear(hidden_dim, dim, bias=args.mlp_bias)

    def __call__(self, x: mx.array) -> mx.array:
        return self.c_proj(nn.silu(self.c_fc_0(x)) * self.c_fc_1(x))


class TransformerBlock(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        self.ln_1 = nn.RMSNorm(args.hidden_size, eps=args.layer_norm_epsilon)
        self.attn = Attention(args)
        self.ln_2 = nn.RMSNorm(args.hidden_size, eps=args.layer_norm_epsilon)
        self.mlp = MLP(args)

    def __call__(
        self,
        x: mx.array,
        mask: Optional[mx.array] = None,
        cache: Optional[Any] = None,
    ) -> mx.array:
        h = x + self.attn.attention(self.ln_1(x), mask, cache)
        out = h + self.mlp(self.ln_2(h))
        return out


class ExaoneModel(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        self.wte = nn.Embedding(args.vocab_size, args.hidden_size)
        self.h = [TransformerBlock(args) for _ in range(args.num_layers)]
        self.ln_f = nn.RMSNorm(args.hidden_size, eps=args.layer_norm_epsilon)

    def __call__(
        self,
        inputs: mx.array,
        mask: mx.array = None,
        cache=None,
    ):
        h = self.wte(inputs)
        if mask is None:
            mask = create_attention_mask(h, cache)

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

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

        return self.ln_f(h)


class Model(nn.Module):
    def __init__(self, args: ModelArgs):
        super().__init__()
        self.args = args
        self.model_type = args.model_type
        self.transformer = ExaoneModel(args)
        if not args.tie_word_embeddings:
            self.lm_head = nn.Linear(args.hidden_size, args.vocab_size, bias=False)

    def __call__(
        self,
        inputs: mx.array,
        mask: mx.array = None,
        cache=None,
    ):
        out = self.transformer(inputs, mask, cache)
        if self.args.tie_word_embeddings:
            out = self.transformer.wte.as_linear(out)
        else:
            out = self.lm_head(out)
        return out

    @property
    def layers(self):
        return self.transformer.h