| |
|
|
| """Incremental decode caches for bit-exact autoregressive generation. |
| |
| The Daffodils RDT has exactly one cross-position operation: causal MLA |
| attention. Every other sub-layer is per-position (mHC stream mixing, SwiGLU |
| FFN, RMSNorm) or a sequential recurrence (the NaiveSSM Mamba scan). Therefore |
| incremental decoding -- appending one token at a time while reusing frozen |
| earlier state -- is *numerically identical* to re-running the full forward on |
| the growing prefix, and these caches make that explicit. |
| |
| Two primitive caches: |
| |
| * :class:`MLACache` -- post-RoPE ``K``/``V`` of one attention call, grown by |
| ``append``. Because each refinement pass of the Stage-2 loop is itself a |
| fresh causal attention over the frozen earlier positions, every |
| ``(step, layer)`` pair owns its own :class:`MLACache`. |
| * :class:`MambaCache` -- the constant-size ``(conv_window, ssm_state)`` of one |
| NaiveSSM layer, so the selective scan can be stepped one token at a time. |
| |
| :class:`DecodeCache` is a flat keyed container the orchestrators |
| (``RDTForCausalLM`` / ``TwoStageCore``) populate lazily; keys encode the call |
| site (e.g. ``"prelude.0"``, ``"stage1.2"``, ``"stage2.s3.l0"``, ``"coda.1"``). |
| """ |
|
|
| from __future__ import annotations |
|
|
| from dataclasses import dataclass, field |
|
|
| import torch |
|
|
|
|
| @dataclass |
| class MLACache: |
| """Per-attention-call key/value cache (post-RoPE, ``[B, H, T, head_dim]``).""" |
|
|
| k: torch.Tensor | None = None |
| v: torch.Tensor | None = None |
|
|
| @property |
| def length(self) -> int: |
| return 0 if self.k is None else self.k.shape[-2] |
|
|
| def append( |
| self, k: torch.Tensor, v: torch.Tensor |
| ) -> tuple[torch.Tensor, torch.Tensor]: |
| """Append the new tokens' ``k``/``v`` and return the full cached tensors.""" |
|
|
| if self.k is None: |
| self.k, self.v = k, v |
| else: |
| self.k = torch.cat([self.k, k], dim=-2) |
| self.v = torch.cat([self.v, v], dim=-2) |
| return self.k, self.v |
|
|
|
|
| @dataclass |
| class MambaCache: |
| """Per-NaiveSSM constant-size recurrent state. |
| |
| ``conv_window`` holds the last ``d_conv - 1`` *pre-convolution* columns |
| (shape ``[B, d_inner, d_conv - 1]``); ``ssm_state`` is the selective-scan |
| state ``[B, nheads, headdim, d_state]`` in float32. |
| """ |
|
|
| conv_window: torch.Tensor | None = None |
| ssm_state: torch.Tensor | None = None |
|
|
|
|
| @dataclass |
| class DecodeCache: |
| """Flat keyed container of per-layer caches for one decode stream.""" |
|
|
| mla: dict[str, MLACache] = field(default_factory=dict) |
| mamba: dict[str, MambaCache] = field(default_factory=dict) |
| seq_len: int = 0 |
|
|
| def mla_cache(self, key: str) -> MLACache: |
| cache = self.mla.get(key) |
| if cache is None: |
| cache = self.mla[key] = MLACache() |
| return cache |
|
|
| def mamba_cache(self, key: str) -> MambaCache: |
| cache = self.mamba.get(key) |
| if cache is None: |
| cache = self.mamba[key] = MambaCache() |
| return cache |
|
|
| @property |
| def past_len(self) -> int: |
| """Number of tokens already cached (0 before the prefill call).""" |
|
|
| return self.seq_len |
|
|
