File size: 10,342 Bytes
7bf638f | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 | """SHRAM per-layer cache — composite owner for one SHRAM decoder layer.
A SHRAM decoder layer contains two distinct attention pathways at one attention slot: the
local sliding-window path and the MoSRAH sparse path. Each path has its own cache with
different semantics and a different downstream consumer. ShramLayerCache owns both, satisfies
the HuggingFace per-layer cache role, and exposes each sub-cache directly so its attention
path can interact with it without indirection.
ShramLayerCache does not define a composite update() interface. The two paths have materially
different update semantics — the local side uses chunk-local key/value/mask concatenation
while the MoSRAH side uses expert-choice scatter with an active mask — and merging these
behind a single update() would hide those differences behind a misleading abstraction. Instead,
each attention path calls update() on the sub-cache it owns. ShramLayerCache acts as the
ownership, coordination, and reset/reorder boundary for one decoder layer.
Sequence length at this boundary is reported by delegating to the local sliding-window
sub-cache, which tracks the cumulative count of token positions processed. This is the
quantity HuggingFace generation reads through get_seq_length().
"""
import torch
from transformers.cache_utils import CacheLayerMixin
from .__cache__mosrah_cache import MoSRAHCache
from .__cache__sliding_window_cache import LocalSlidingWindowLayerCache
class ShramLayerCache(CacheLayerMixin):
"""Cache subsystem for one SHRAM decoder layer.
Owns and coordinates two sub-caches:
- sliding_window_cache: LocalSlidingWindowLayerCache for the local sliding-window path.
- mosrah_cache: MoSRAHCache for the MoSRAH sparse attention path.
Satisfies the HuggingFace per-layer cache role (CacheLayerMixin). The two sub-caches are
exposed directly for their downstream attention paths — no composite update() interface is
provided, because the two paths have materially different update semantics.
Sequence length is reported by delegating to the local sliding-window sub-cache, which
tracks the cumulative count of token positions processed across all update() calls.
Args:
sliding_window: Number of tokens retained by the local sliding-window cache.
num_local_heads: Number of local attention heads.
local_head_dim: Per-head embedding width for the local path.
num_mosrah_heads: Total number of MoSRAH expert heads (L).
mosrah_head_dim: Bottlenecked head embedding width (u) for the MoSRAH path.
batch_size: Number of sequences in the batch.
device: Device on which to allocate cache tensors.
initial_buffer_size: Initial per-(batch, head) capacity for MoSRAHCache. Doubled
when any slot overflows. Defaults to 64 to avoid repeated reallocation during
prompt processing.
"""
is_compileable = False
is_sliding = False
def __init__(
self,
sliding_window: int,
num_local_heads: int,
local_head_dim: int,
num_mosrah_heads: int,
mosrah_head_dim: int,
batch_size: int,
device: torch.device,
initial_buffer_size: int = 64,
) -> None:
super().__init__()
self.sliding_window_cache = LocalSlidingWindowLayerCache(
sliding_window=sliding_window,
num_heads=num_local_heads,
head_dim=local_head_dim,
batch_size=batch_size,
device=device,
)
self.mosrah_cache = MoSRAHCache(
num_mosrah_heads=num_mosrah_heads,
head_dim=mosrah_head_dim,
batch_size=batch_size,
device=device,
initial_buffer_size=initial_buffer_size,
)
# ---------------------------------------------------------------------------
# Properties
# ---------------------------------------------------------------------------
@property
def is_initialized(self) -> bool:
"""True iff both sub-caches have allocated their storage.
Both LocalSlidingWindowLayerCache and MoSRAHCache pre-allocate at construction,
so this is True immediately after ShramLayerCache.__init__ returns.
"""
return self.sliding_window_cache.is_initialized and self.mosrah_cache.is_initialized
@is_initialized.setter
def is_initialized(self, value: bool) -> None:
# CacheLayerMixin.__init__ assigns self.is_initialized = False as an instance
# attribute. Since property is a data descriptor it takes precedence, but Python
# still routes the assignment through __set__. Absorb it silently — state is
# derived from sub-caches, not stored here.
pass
# ---------------------------------------------------------------------------
# CacheLayerMixin — composite-meaningful methods
# ---------------------------------------------------------------------------
def get_seq_length(self) -> int: # type: ignore[override]
"""Return the cumulative sequence length from the local sliding-window path.
The local path is authoritative for sequence progress: it sees every token
presented to this layer and accumulates a truthful total. Delegates to
sliding_window_cache.get_seq_length().
"""
return self.sliding_window_cache.get_seq_length()
def reset(self) -> None:
"""Clear both sub-caches.
Delegates reset to each sub-cache. Both are cleared atomically so the sliding-window
state and MoSRAH sparse state remain consistent.
"""
self.sliding_window_cache.reset()
self.mosrah_cache.reset()
def reorder_cache(self, beam_idx: torch.LongTensor) -> None:
"""Reorder the batch dimension of both sub-caches for beam search.
Delegates to each sub-cache. Both are reordered atomically so the sliding-window
and MoSRAH state correspond to the same beam hypotheses after reordering.
Args:
beam_idx: Permutation indices of shape (batch,) produced by beam search.
"""
self.sliding_window_cache.reorder_cache(beam_idx)
self.mosrah_cache.reorder_cache(beam_idx)
def batch_repeat_interleave(self, repeats: int) -> None:
"""Expand the batch dimension of both sub-caches for beam search initialisation.
Delegates atomically to each sub-cache. Both must be expanded together so the
sliding-window and MoSRAH state correspond to the same beam candidates.
Args:
repeats: Number of times to repeat each batch entry.
"""
self.sliding_window_cache.batch_repeat_interleave(repeats)
self.mosrah_cache.batch_repeat_interleave(repeats)
def batch_select_indices(self, indices: torch.Tensor) -> None:
"""Select a subset of batch entries in both sub-caches for contrastive search.
Delegates atomically to each sub-cache. Both must be trimmed together so the
sliding-window and MoSRAH state remain consistent.
Args:
indices: 1-D integer tensor of batch indices to retain.
"""
self.sliding_window_cache.batch_select_indices(indices)
self.mosrah_cache.batch_select_indices(indices)
def offload(self) -> None:
"""Offload both sub-caches to CPU.
Delegates to each sub-cache's offload method. Does not call super() — ShramLayerCache
does not own self.keys/self.values directly; all cached data lives in the sub-caches.
"""
self.sliding_window_cache.offload()
self.mosrah_cache.offload()
def prefetch(self) -> None:
"""Move both sub-caches back to their model device ahead of time.
Delegates to each sub-cache's prefetch method. Does not call super() — ShramLayerCache
does not own self.keys/self.values directly; all cached data lives in the sub-caches.
"""
self.sliding_window_cache.prefetch()
self.mosrah_cache.prefetch()
def lazy_initialization( # type: ignore[override]
self, key_states: torch.Tensor, value_states: torch.Tensor
) -> None:
"""No-op — both sub-caches handle their own initialization."""
pass
# ---------------------------------------------------------------------------
# CacheLayerMixin — unsupported abstract methods
# ---------------------------------------------------------------------------
def update( # type: ignore[override]
self,
key_states: torch.Tensor,
value_states: torch.Tensor,
cache_kwargs: dict | None = None,
) -> tuple[torch.Tensor, torch.Tensor]:
"""Not supported — ShramLayerCache has no composite update interface.
The two sub-caches have materially different update semantics: the sliding-window
side uses standard key/value concatenation while the MoSRAH side uses expert-choice
scatter with an active mask. Callers must update each sub-cache directly via
sliding_window_cache.update() or mosrah_cache.update().
"""
raise NotImplementedError(
"ShramLayerCache has no composite update interface. "
"Update sliding_window_cache or mosrah_cache directly."
)
def get_max_cache_shape(self) -> int: # type: ignore[override]
"""Not supported — the composite cache has no single maximum shape.
The sliding-window cache is bounded by sliding_window; the MoSRAH cache is
unbounded. No truthful scalar maximum represents the composite.
"""
raise NotImplementedError(
"ShramLayerCache has no single maximum cache shape. "
"Query sliding_window_cache or mosrah_cache directly."
)
def get_mask_sizes( # type: ignore[override]
self,
cache_position: torch.Tensor,
) -> tuple[int, int]:
"""Not supported — ShramLayerCache does not participate in HF mask construction.
The two sub-caches have different mask semantics and their respective attention
paths handle masking directly.
"""
raise NotImplementedError(
"ShramLayerCache does not support get_mask_sizes(). "
"Query sliding_window_cache or mosrah_cache directly."
)
|