from typing import Tuple, List, Dict, Optional from dataclasses import dataclass import math import torch import torch.nn.functional as F from torch import nn from pydantic import BaseModel from models.common import trunc_normal_init_ from models.layers import rms_norm, SwiGLU, Attention, RotaryEmbedding, CosSin, CastedEmbedding, CastedLinear from models.sparse_embedding import CastedSparseEmbedding @dataclass class HierarchicalReasoningModel_ACTV1InnerCarry: z_H: torch.Tensor z_L: torch.Tensor @dataclass class HierarchicalReasoningModel_ACTV1Carry: inner_carry: HierarchicalReasoningModel_ACTV1InnerCarry steps: torch.Tensor halted: torch.Tensor current_data: Dict[str, torch.Tensor] class HierarchicalReasoningModel_ACTV1Config(BaseModel): batch_size: int seq_len: int puzzle_emb_ndim: int = 0 num_puzzle_identifiers: int vocab_size: int H_cycles: int L_cycles: int H_layers: int L_layers: int # Transformer config hidden_size: int expansion: float num_heads: int pos_encodings: str rms_norm_eps: float = 1e-5 rope_theta: float = 10000.0 # Halting Q-learning config halt_max_steps: int halt_exploration_prob: float forward_dtype: str = "bfloat16" class HierarchicalReasoningModel_ACTV1Block(nn.Module): def __init__(self, config: HierarchicalReasoningModel_ACTV1Config) -> None: super().__init__() self.self_attn = Attention( hidden_size=config.hidden_size, head_dim=config.hidden_size // config.num_heads, num_heads=config.num_heads, num_key_value_heads=config.num_heads, causal=False ) self.mlp = SwiGLU( hidden_size=config.hidden_size, expansion=config.expansion, ) self.norm_eps = config.rms_norm_eps def forward(self, cos_sin: CosSin, hidden_states: torch.Tensor) -> torch.Tensor: # Post Norm # Self Attention hidden_states = rms_norm(hidden_states + self.self_attn(cos_sin=cos_sin, hidden_states=hidden_states), variance_epsilon=self.norm_eps) # Fully Connected hidden_states = rms_norm(hidden_states + self.mlp(hidden_states), variance_epsilon=self.norm_eps) return hidden_states class HierarchicalReasoningModel_ACTV1ReasoningModule(nn.Module): def __init__(self, layers: List[HierarchicalReasoningModel_ACTV1Block]): super().__init__() self.layers = torch.nn.ModuleList(layers) def forward(self, hidden_states: torch.Tensor, input_injection: torch.Tensor, **kwargs) -> torch.Tensor: # Input injection (add) hidden_states = hidden_states + input_injection # Layers for layer in self.layers: hidden_states = layer(hidden_states=hidden_states, **kwargs) return hidden_states class HierarchicalReasoningModel_ACTV1_Inner(nn.Module): def __init__(self, config: HierarchicalReasoningModel_ACTV1Config) -> None: super().__init__() self.config = config self.forward_dtype = getattr(torch, self.config.forward_dtype) # I/O self.embed_scale = math.sqrt(self.config.hidden_size) embed_init_std = 1.0 / self.embed_scale self.embed_tokens = CastedEmbedding(self.config.vocab_size, self.config.hidden_size, init_std=embed_init_std, cast_to=self.forward_dtype) self.lm_head = CastedLinear(self.config.hidden_size, self.config.vocab_size, bias=False) self.q_head = CastedLinear(self.config.hidden_size, 2, bias=True) self.puzzle_emb_len = -(self.config.puzzle_emb_ndim // -self.config.hidden_size) # ceil div if self.config.puzzle_emb_ndim > 0: # Zero init puzzle embeddings self.puzzle_emb = CastedSparseEmbedding(self.config.num_puzzle_identifiers, self.config.puzzle_emb_ndim, batch_size=self.config.batch_size, init_std=0, cast_to=self.forward_dtype) # LM Blocks if self.config.pos_encodings == "rope": self.rotary_emb = RotaryEmbedding(dim=self.config.hidden_size // self.config.num_heads, max_position_embeddings=self.config.seq_len + self.puzzle_emb_len, base=self.config.rope_theta) elif self.config.pos_encodings == "learned": self.embed_pos = CastedEmbedding(self.config.seq_len + self.puzzle_emb_len, self.config.hidden_size, init_std=embed_init_std, cast_to=self.forward_dtype) else: raise NotImplementedError() # Reasoning Layers self.H_level = HierarchicalReasoningModel_ACTV1ReasoningModule(layers=[HierarchicalReasoningModel_ACTV1Block(self.config) for _i in range(self.config.H_layers)]) self.L_level = HierarchicalReasoningModel_ACTV1ReasoningModule(layers=[HierarchicalReasoningModel_ACTV1Block(self.config) for _i in range(self.config.L_layers)]) # --- CORRECTED CODE BLOCK --- # Initial states h_init_tensor = trunc_normal_init_(torch.empty(self.config.hidden_size, dtype=self.forward_dtype), std=1) self.register_buffer('H_init', h_init_tensor) l_init_tensor = trunc_normal_init_(torch.empty(self.config.hidden_size, dtype=self.forward_dtype), std=1) self.register_buffer('L_init', l_init_tensor) # --- END OF CORRECTION --- # Q head special init # Init Q to (almost) zero for faster learning during bootstrapping with torch.no_grad(): self.q_head.weight.zero_() self.q_head.bias.fill_(-5) # type: ignore def _input_embeddings(self, input: torch.Tensor, puzzle_identifiers: torch.Tensor): # Token embedding embedding = self.embed_tokens(input.to(torch.int32)) # Puzzle embeddings if self.config.puzzle_emb_ndim > 0: puzzle_embedding = self.puzzle_emb(puzzle_identifiers) pad_count = self.puzzle_emb_len * self.config.hidden_size - puzzle_embedding.shape[-1] if pad_count > 0: puzzle_embedding = F.pad(puzzle_embedding, (0, pad_count)) embedding = torch.cat((puzzle_embedding.view(-1, self.puzzle_emb_len, self.config.hidden_size), embedding), dim=-2) # Position embeddings if self.config.pos_encodings == "learned": # scale by 1/sqrt(2) to maintain forward variance embedding = 0.707106781 * (embedding + self.embed_pos.embedding_weight.to(self.forward_dtype)) # Scale return self.embed_scale * embedding def empty_carry(self, batch_size: int): return HierarchicalReasoningModel_ACTV1InnerCarry( z_H=torch.empty(batch_size, self.config.seq_len + self.puzzle_emb_len, self.config.hidden_size, dtype=self.forward_dtype), z_L=torch.empty(batch_size, self.config.seq_len + self.puzzle_emb_len, self.config.hidden_size, dtype=self.forward_dtype), ) def reset_carry(self, reset_flag: torch.Tensor, carry: HierarchicalReasoningModel_ACTV1InnerCarry): return HierarchicalReasoningModel_ACTV1InnerCarry( z_H=torch.where(reset_flag.view(-1, 1, 1), self.H_init, carry.z_H), z_L=torch.where(reset_flag.view(-1, 1, 1), self.L_init, carry.z_L), ) def forward(self, carry: HierarchicalReasoningModel_ACTV1InnerCarry, batch: Dict[str, torch.Tensor]) -> Tuple[HierarchicalReasoningModel_ACTV1InnerCarry, torch.Tensor, Tuple[torch.Tensor, torch.Tensor]]: seq_info = dict( cos_sin=self.rotary_emb() if hasattr(self, "rotary_emb") else None, ) # Input encoding input_embeddings = self._input_embeddings(batch["inputs"], batch["puzzle_identifiers"]) # Forward iterations with torch.no_grad(): z_H, z_L = carry.z_H, carry.z_L for _H_step in range(self.config.H_cycles): for _L_step in range(self.config.L_cycles): if not ((_H_step == self.config.H_cycles - 1) and (_L_step == self.config.L_cycles - 1)): z_L = self.L_level(z_L, z_H + input_embeddings, **seq_info) if not (_H_step == self.config.H_cycles - 1): z_H = self.H_level(z_H, z_L, **seq_info) assert not z_H.requires_grad and not z_L.requires_grad # 1-step grad z_L = self.L_level(z_L, z_H + input_embeddings, **seq_info) z_H = self.H_level(z_H, z_L, **seq_info) # LM Outputs new_carry = HierarchicalReasoningModel_ACTV1InnerCarry(z_H=z_H.detach(), z_L=z_L.detach()) # New carry no grad output = self.lm_head(z_H)[:, self.puzzle_emb_len:] # Q head q_logits = self.q_head(z_H[:, 0]).to(torch.float32) return new_carry, output, (q_logits[..., 0], q_logits[..., 1]) class HierarchicalReasoningModel_ACTV1(nn.Module): """ACT wrapper.""" def __init__(self, config_dict: dict): super().__init__() self.config = HierarchicalReasoningModel_ACTV1Config(**config_dict) self.inner = HierarchicalReasoningModel_ACTV1_Inner(self.config) @property def puzzle_emb(self): return self.inner.puzzle_emb def initial_carry(self, batch: Dict[str, torch.Tensor]): batch_size = batch["inputs"].shape[0] return HierarchicalReasoningModel_ACTV1Carry( inner_carry=self.inner.empty_carry(batch_size), # Empty is expected, it will be reseted in first pass as all sequences are halted. steps=torch.zeros((batch_size, ), dtype=torch.int32), halted=torch.ones((batch_size, ), dtype=torch.bool), # Default to halted current_data={k: torch.empty_like(v) for k, v in batch.items()} ) def forward(self, carry: HierarchicalReasoningModel_ACTV1Carry, batch: Dict[str, torch.Tensor]) -> Tuple[HierarchicalReasoningModel_ACTV1Carry, Dict[str, torch.Tensor]]: # Update data, carry (removing halted sequences) new_inner_carry = self.inner.reset_carry(carry.halted, carry.inner_carry) new_steps = torch.where(carry.halted, 0, carry.steps) new_current_data = {k: torch.where(carry.halted.view((-1, ) + (1, ) * (batch[k].ndim - 1)), batch[k], v) for k, v in carry.current_data.items()} # Forward inner model new_inner_carry, logits, (q_halt_logits, q_continue_logits) = self.inner(new_inner_carry, new_current_data) outputs = { "logits": logits, "q_halt_logits": q_halt_logits, "q_continue_logits": q_continue_logits } with torch.no_grad(): # Step new_steps = new_steps + 1 is_last_step = new_steps >= self.config.halt_max_steps halted = is_last_step # if training, and ACT is enabled if self.training and (self.config.halt_max_steps > 1): # Halt signal # NOTE: During evaluation, always use max steps, this is to guarantee the same halting steps inside a batch for batching purposes halted = halted | (q_halt_logits > q_continue_logits) # Exploration min_halt_steps = (torch.rand_like(q_halt_logits) < self.config.halt_exploration_prob) * torch.randint_like(new_steps, low=2, high=self.config.halt_max_steps + 1) halted = halted & (new_steps >= min_halt_steps) # Compute target Q # NOTE: No replay buffer and target networks for computing target Q-value. # As batch_size is large, there're many parallel envs. # Similar concept as PQN https://arxiv.org/abs/2407.04811 next_q_halt_logits, next_q_continue_logits = self.inner(new_inner_carry, new_current_data)[-1] outputs["target_q_continue"] = torch.sigmoid(torch.where(is_last_step, next_q_halt_logits, torch.maximum(next_q_halt_logits, next_q_continue_logits))) return HierarchicalReasoningModel_ACTV1Carry(new_inner_carry, new_steps, halted, new_current_data), outputs