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+from dataclasses import dataclass, field
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+from typing import Dict, Optional, Tuple, Union
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+
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+import mlx.core as mx
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+import mlx.nn as nn
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+
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+from mlx_lm.models.base import BaseModelArgs, create_additive_causal_mask
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+from ...shard import Shard
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+
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+
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+@dataclass
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+class NormalModelArgs(BaseModelArgs):
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+ model_type: str
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+ hidden_size: int
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+ num_hidden_layers: int
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+ intermediate_size: int
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+ num_attention_heads: int
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+ rms_norm_eps: float
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+ vocab_size: int
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+ num_key_value_heads: int = None
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+ attention_bias: bool = False
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+ mlp_bias: bool = False
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+ rope_theta: float = 10000
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+ rope_traditional: bool = False
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+ rope_scaling: Optional[Dict[str, Union[float, str]]] = None
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+ tie_word_embeddings: bool = True
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+
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+ def __post_init__(self):
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+ if self.num_key_value_heads is None:
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+ self.num_key_value_heads = self.num_attention_heads
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+
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+ if self.rope_scaling:
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+ required_keys = {"factor", "type"}
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+ if not all(key in self.rope_scaling for key in required_keys):
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+ raise ValueError(f"rope_scaling must contain keys {required_keys}")
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+
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+ if self.rope_scaling["type"] != "linear":
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+ raise ValueError("rope_scaling 'type' currently only supports 'linear'")
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+@dataclass
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+class ModelArgs(NormalModelArgs):
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+ shard: Shard = field(default_factory=lambda: Shard("", 0, 0, 0))
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+
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+ def __post_init__(self):
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+ super().__post_init__() # Ensure parent initializations are respected
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+
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+ if isinstance(self.shard, Shard):
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+ return
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+ if not isinstance(self.shard, dict):
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+ raise TypeError(f"Expected shard to be a Shard instance or a dict, got {type(self.shard)} instead")
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+
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+ self.shard = Shard(**self.shard)
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+
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+class Attention(nn.Module):
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+ def __init__(self, args: ModelArgs):
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+ super().__init__()
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+
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+ dim = args.hidden_size
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+ self.n_heads = n_heads = args.num_attention_heads
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+ self.n_kv_heads = n_kv_heads = args.num_key_value_heads
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+
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+ head_dim = args.hidden_size // n_heads
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+ self.scale = head_dim**-0.5
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+ if hasattr(args, "attention_bias"):
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+ attention_bias = args.attention_bias
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+ else:
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+ attention_bias = False
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+
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+ self.q_proj = nn.Linear(dim, n_heads * head_dim, bias=attention_bias)
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+ self.k_proj = nn.Linear(dim, n_kv_heads * head_dim, bias=attention_bias)
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+ self.v_proj = nn.Linear(dim, n_kv_heads * head_dim, bias=attention_bias)
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+ self.o_proj = nn.Linear(n_heads * head_dim, dim, bias=attention_bias)
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+
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+ rope_scale = (
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+ 1 / args.rope_scaling["factor"]
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+ if args.rope_scaling is not None and args.rope_scaling["type"] == "linear"
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+ else 1
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+ )
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+ self.rope = nn.RoPE(
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+ head_dim,
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+ traditional=args.rope_traditional,
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+ base=args.rope_theta,
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+ scale=rope_scale,
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+ )
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+
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+ def __call__(
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+ self,
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+ x: mx.array,
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+ mask: Optional[mx.array] = None,
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+ cache: Optional[Tuple[mx.array, mx.array]] = None,
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+ ) -> mx.array:
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+ B, L, D = x.shape
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+
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+ queries, keys, values = self.q_proj(x), self.k_proj(x), self.v_proj(x)
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+
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+ # Prepare the queries, keys and values for the attention computation
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+ queries = queries.reshape(B, L, self.n_heads, -1).transpose(0, 2, 1, 3)
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+ keys = keys.reshape(B, L, self.n_kv_heads, -1).transpose(0, 2, 1, 3)
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+ values = values.reshape(B, L, self.n_kv_heads, -1).transpose(0, 2, 1, 3)
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+
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+ if cache is not None:
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+ queries = self.rope(queries, offset=cache.offset)
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+ keys = self.rope(keys, offset=cache.offset)
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+ keys, values = cache.update_and_fetch(keys, values)
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+ else:
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+ queries = self.rope(queries)
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+ keys = self.rope(keys)
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+
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+ output = mx.fast.scaled_dot_product_attention(
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+ queries, keys, values, scale=self.scale, mask=mask
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+ )
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+ output = output.transpose(0, 2, 1, 3).reshape(B, L, -1)
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+ return self.o_proj(output)
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+
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+
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+class MLP(nn.Module):
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+ def __init__(self, args: ModelArgs):
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+ super().__init__()
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+
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+ dim = args.hidden_size
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+ hidden_dim = args.intermediate_size
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+ if hasattr(args, "mlp_bias"):
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+ mlp_bias = args.mlp_bias
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+ else:
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+ mlp_bias = False
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+
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+ self.gate_proj = nn.Linear(dim, hidden_dim, bias=mlp_bias)
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+ self.down_proj = nn.Linear(hidden_dim, dim, bias=mlp_bias)
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+ self.up_proj = nn.Linear(dim, hidden_dim, bias=mlp_bias)
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+
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+ def __call__(self, x) -> mx.array:
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+ return self.down_proj(nn.silu(self.gate_proj(x)) * self.up_proj(x))
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+
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+
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+class TransformerBlock(nn.Module):
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+ def __init__(self, args: ModelArgs):
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+ super().__init__()
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+ self.num_attention_heads = args.num_attention_heads
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+ self.hidden_size = args.hidden_size
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+ self.self_attn = Attention(args)
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+ self.mlp = MLP(args)
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+ self.input_layernorm = nn.RMSNorm(args.hidden_size, eps=args.rms_norm_eps)
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+ self.post_attention_layernorm = nn.RMSNorm(
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+ args.hidden_size, eps=args.rms_norm_eps
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+ )
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+ self.args = args
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+
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+ def __call__(
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+ self,
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+ x: mx.array,
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+ mask: Optional[mx.array] = None,
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+ cache: Optional[Tuple[mx.array, mx.array]] = None,
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+ ) -> mx.array:
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+ r = self.self_attn(self.input_layernorm(x), mask, cache)
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+ h = x + r
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+ r = self.mlp(self.post_attention_layernorm(h))
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+ out = h + r
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+ return out
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+
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+
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+class LlamaModel(nn.Module):
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+ def __init__(self, args: ModelArgs):
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+ super().__init__()
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+ self.args = args
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+ self.vocab_size = args.vocab_size
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+ self.num_hidden_layers = args.num_hidden_layers
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+ assert self.vocab_size > 0
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+ self.embed_tokens = nn.Embedding(args.vocab_size, args.hidden_size)
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+ self.layers = [
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+ TransformerBlock(args=args) for _ in range(args.shard.n_layers)
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+ ]
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+ self.norm = nn.RMSNorm(args.hidden_size, eps=args.rms_norm_eps)
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+
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+ def __call__(
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+ self,
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+ inputs: mx.array,
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+ cache=None,
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+ ):
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+ if self.args.shard.is_first_layer():
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+ h = self.embed_tokens(inputs)
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+ else:
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+ h = inputs
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+
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+ mask = None
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+ if h.shape[1] > 1:
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+ mask = create_additive_causal_mask(
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+ h.shape[1], cache[0].offset if cache is not None else 0
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+ )
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+ mask = mask.astype(h.dtype)
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+
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+ if cache is None:
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+ cache = [None] * len(self.layers)
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+
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+ for layer, c in zip(self.layers, cache):
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+ h = layer(h, mask, cache=c)
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+
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+ if self.args.shard.is_last_layer():
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+ return self.norm(h)
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+ else:
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+ return h
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+
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+
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+class Model(nn.Module):
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+ def __init__(self, args: ModelArgs):
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+ super().__init__()
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+ self.args = args
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+ self.model_type = args.model_type
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+ self.model = LlamaModel(args)
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+ if not args.tie_word_embeddings:
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+ self.lm_head = nn.Linear(args.hidden_size, args.vocab_size, bias=False)
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+
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+ def __call__(
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+ self,
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+ inputs: mx.array,
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+ cache=None,
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+ ):
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+ out = self.model(inputs, cache)
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+
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+ if self.args.shard.is_last_layer():
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+ if self.args.tie_word_embeddings:
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+ out = self.model.embed_tokens.as_linear(out)
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+ else:
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+ out = self.lm_head(out)
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+
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+ return out
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+
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+
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+ def sanitize(self, weights):
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+ # Remove unused precomputed rotary freqs
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+ return {
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+ k: v for k, v in weights.items() if "self_attn.rotary_emb.inv_freq" not in k
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+ }
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+
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+ @property
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+ def layers(self):
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+ return self.model.layers
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+
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+ @property
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+ def head_dim(self):
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+ return self.args.hidden_size // self.args.num_attention_heads
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+
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+ @property
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+ def n_kv_heads(self):
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+ return self.args.num_key_value_heads
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+
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