diff --git a/llms/mlx_lm/models/mamba2.py b/llms/mlx_lm/models/mamba2.py new file mode 100644 index 00000000..6e6e268c --- /dev/null +++ b/llms/mlx_lm/models/mamba2.py @@ -0,0 +1,264 @@ +# Copyright © 2024 Apple Inc. + +import math +from dataclasses import dataclass, field +from typing import Optional, Tuple, Union + +import mlx.core as mx +import mlx.nn as nn + +from .base import BaseModelArgs + + +@dataclass +class ModelArgs(BaseModelArgs): + model_type: str = "mamba2" + num_heads: int = 128 + head_dim: int = 64 + vocab_size: int = 32768 + hidden_size: int = 4096 + state_size: int = 128 + num_hidden_layers: int = 64 + layer_norm_epsilon: float = 1e-5 + pad_token_id: int = 1 + bos_token_id: int = 0 + eos_token_id: int = 2 + expand: int = 2 + conv_kernel: int = 4 + n_groups: int = 8 + use_bias: bool = False + use_conv_bias: bool = True + hidden_act: str = "silu" + initializer_range: float = 0.1 + residual_in_fp32: bool = True + time_step_rank: Union[int, str] = "auto" + time_step_min: float = 0.001 + time_step_max: float = 0.1 + time_step_floor: float = 1e-4 + time_step_limit: Tuple[float, float] = field(default_factory=lambda: (0.0, float("inf"))) + rescale_prenorm_residual: bool = False + use_cache: bool = True + rms_norm: bool = True + chunk_size: int = 256 + tie_word_embeddings: bool = False + + def __post_init__(self): + if not hasattr(self, "intermediate_size"): + self.intermediate_size = int(self.expand * self.hidden_size) + if not hasattr(self, "head_dim"): + self.head_dim = self.hidden_size // self.num_heads + if self.time_step_rank == "auto": + self.time_step_rank = math.ceil(self.hidden_size / 16) + + +class Mamba2Cache: + def __init__(self, num_layers): + self.cache = [[None, None] for _ in range(num_layers)] + + def __getitem__(self, idx): + return self.cache[idx] + + def __setitem__(self, idx, value): + self.cache[idx] = value + + +class MambaRMSNormGated(nn.Module): + def __init__(self, hidden_size, eps=1e-6): + super().__init__() + self.weight = mx.ones((hidden_size,)) + self.variance_epsilon = eps + + def __call__(self, hidden_states, gate=None): + if gate is not None: + hidden_states = hidden_states * nn.silu(gate) + variance = mx.mean(hidden_states ** 2, axis=-1, keepdims=True) + hidden_states = hidden_states * mx.rsqrt(variance + self.variance_epsilon) + return self.weight * hidden_states + + +class Mamba2Mixer(nn.Module): + def __init__(self, args: ModelArgs): + super().__init__() + self.args = args + self.hidden_size = args.hidden_size + self.intermediate_size = args.intermediate_size + self.conv_kernel_size = args.conv_kernel + self.state_size = args.state_size + self.num_heads = args.num_heads + self.head_dim = args.head_dim + self.n_groups = args.n_groups + self.time_step_rank = args.time_step_rank + + projection_size = self.intermediate_size + self.intermediate_size + 2 * self.n_groups * self.state_size + self.num_heads + self.in_proj = nn.Linear( + self.hidden_size, + projection_size, + bias=args.use_bias + ) + + self.conv_dim = self.intermediate_size + 2 * self.n_groups * self.state_size + self.conv1d = nn.Conv1d( + in_channels=self.conv_dim, + out_channels=self.conv_dim, + bias=args.use_conv_bias, + kernel_size=args.conv_kernel, + groups=self.conv_dim, + padding=args.conv_kernel - 1, + ) + + self.act = nn.SiLU() + self.dt_bias = mx.ones((self.num_heads,)) + self.A_log = mx.log(mx.arange(1, self.num_heads + 1, dtype=mx.float32)) + self.D = mx.ones((self.num_heads,)) + + self.out_proj = nn.Linear(self.intermediate_size, self.hidden_size, bias=args.use_bias) + self.norm = MambaRMSNormGated(self.intermediate_size, eps=args.layer_norm_epsilon) + + def ssm_step(self, x, dt, state): + A = -mx.exp(self.A_log) + D = self.D + + deltaBC = self.in_proj(x) + gate, conv_state, time_step = mx.split( + deltaBC, + [self.intermediate_size, self.intermediate_size + 2 * self.n_groups * self.state_size], + axis=-1 + ) + + conv_state = conv_state.transpose(0, 2, 1) + conv_out = self.conv1d(conv_state) + conv_out = conv_out.transpose(0, 2, 1) + conv_out = self.act(conv_out) + + x_and_conv_out, B, C = mx.split( + conv_out, + [self.intermediate_size, self.n_groups * self.state_size], + axis=-1 + ) + + dt = nn.softplus(time_step + self.dt_bias) + dt = mx.clip(dt, self.args.time_step_min, self.args.time_step_max) + + B = B.reshape(-1, self.num_heads, self.head_dim, self.state_size) + C = C.reshape(-1, self.num_heads, self.head_dim, self.state_size) + + dA = mx.exp(dt[:, :, None, None] * A[None, :, None, None]) + dB = dt[:, :, None, None] * B + + new_state = state * dA + x_and_conv_out[:, :, None, None] * dB + y = mx.sum(new_state * C, axis=-1) + y = y + D[None, :, None] * x_and_conv_out + + y = self.norm(y.reshape(-1, self.intermediate_size), gate) + output = self.out_proj(y) + + return output, new_state + + def __call__( + self, + x: mx.array, + cache = None + ): + B, L, _ = x.shape + + if cache[0] is not None: # Using cached state + conv_state, ssm_state = cache + x = x[:, -1:] + output, new_ssm_state = self.ssm_step(x, None, ssm_state) + cache[1] = new_ssm_state # Update SSM state in cache + else: + conv_state, ssm_state = None, None + outputs = [] + for t in range(L): + x = x[:, t:t+1] + output, ssm_state = self.ssm_step(x, None, ssm_state) + outputs.append(output) + output = mx.concatenate(outputs, axis=1) + cache[1] = ssm_state # Store final SSM state in cache + + # Update conv state in cache + new_conv_state = x[:, -self.conv_kernel_size:] + cache[0] = new_conv_state + + return output + + +class Mamba2Block(nn.Module): + def __init__(self, args: ModelArgs): + super().__init__() + self.args = args + self.residual_in_fp32 = args.residual_in_fp32 + self.norm = nn.RMSNorm(args.hidden_size, eps=args.layer_norm_epsilon) + self.mixer = Mamba2Mixer(args) + + def __call__( + self, + inputs: mx.array, + cache=None, + ): + h = self.mixer(self.norm(inputs), cache_params=cache) + r = inputs + h + return r + + +class Mamba2(nn.Module): + def __init__(self, args: ModelArgs): + super().__init__() + self.args = args + self.embeddings = nn.Embedding(args.vocab_size, args.hidden_size) + self.layers = [Mamba2Block(args) for idx in range(args.num_hidden_layers)] + self.norm_f = nn.RMSNorm(args.hidden_size, eps=args.layer_norm_epsilon) + + def __call__( + self, + inputs: mx.array, + cache=None + ): + hidden_states = self.embeddings(inputs) + + if cache is None: + cache = Mamba2Cache(len(self.layers)) + + for i, layer in enumerate(self.layers): + hidden_states = layer(hidden_states, cache[i]) + + hidden_states = self.norm_f(hidden_states) + return hidden_states + + +class Model(nn.Module): + def __init__(self, args: ModelArgs): + super().__init__() + self.args = args + self.model_type = args.model_type + self.backbone = Mamba2(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, + cache=None + ): + B, T = inputs.shape + + x = self.backbone(inputs, cache) + + if self.args.tie_word_embeddings: + logits = self.backbone.embeddings.as_linear(x) + else: + logits = self.lm_head(x) + return logits + + def sanitize_mabey(self, weights): + for k, v in weights.items(): + if "conv1d.weight" in k and v.ndim == 3: + weights[k] = v.moveaxis(2, 1) + return weights + + def make_cache(self, batch_size: int = 1): + return Mamba2Cache(len(self.backbone.layers)) + + @property + def layers(self): + return self.backbone.layers