78 transformer blocks › 75 MoE blocks › Sparse latent attention › Key heads
Rotated shared key
×tensork_rot · 405
The position-carrying key features every head uses.
- shape
- [B batch, T positions, 64 rotary]
Sources
Contextual evidence from Rotate shared key
Interleaved RoPE rotates consecutive feature pairs (x0, x1), (x2, x3), … by one frequency each; attention and the indexer both call it.
apply-rope · huggingface/transformers / modeling_glm_moe_dsa.py
Pinned revision 5e4d6304de55 ↗ · lines 125–405
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def apply_rotary_pos_emb_interleave(q, k, cos, sin, position_ids=None, unsqueeze_dim=1):
r"""
Applies interleaved Rotary Position Embedding to the query and key tensors.
DeepSeek lays the rotary dimensions out in interleaved pairs `(x0, x1), (x2, x3), ...`, each rotated by a
single frequency. We compute that rotation directly on the even/odd slices instead of de-interleaving with a
`view`/`transpose`/`reshape`; the output is bit-identical to the de-interleaved `rotate_half` formulation while
avoiding the extra contiguous copy.
Args:
q (`torch.Tensor`): The query tensor.
k (`torch.Tensor`): The key tensor.
cos (`torch.Tensor`): The cosine part of the rotary embedding.
sin (`torch.Tensor`): The sine part of the rotary embedding.
position_ids (`torch.Tensor`):
The position indices of the tokens corresponding to the query and key tensors. For example, this can be
used to pass offsetted position ids when working with a KV-cache.
unsqueeze_dim (`int`, *optional*, defaults to 1):
The 'unsqueeze_dim' argument specifies the dimension along which to unsqueeze cos[position_ids] and
sin[position_ids] so that they can be properly broadcasted to the dimensions of q and k. For example, note
that cos[position_ids] and sin[position_ids] have the shape [batch_size, seq_len, head_dim]. Then, if q and
k have the shape [batch_size, heads, seq_len, head_dim], then setting unsqueeze_dim=1 makes
cos[position_ids] and sin[position_ids] broadcastable to the shapes of q and k. Similarly, if q and k have
the shape [batch_size, seq_len, heads, head_dim], then set unsqueeze_dim=2.
Returns:
`tuple(torch.Tensor)` comprising of the query and key tensors rotated using the Rotary Position Embedding.
"""
# `cos`/`sin` are `cat(freqs, freqs)`; the first half holds the per-pair angle.
cos = cos[..., : cos.shape[-1] // 2].unsqueeze(unsqueeze_dim)
sin = sin[..., : sin.shape[-1] // 2].unsqueeze(unsqueeze_dim)
q1, q2 = q[..., 0::2], q[..., 1::2]
k1, k2 = k[..., 0::2], k[..., 1::2]
q_embed = torch.cat([q1 * cos - q2 * sin, q2 * cos + q1 * sin], dim=-1)
k_embed = torch.cat([k1 * cos - k2 * sin, k2 * cos + k1 * sin], dim=-1)
return q_embed, k_embed… lines 162–231 omitted …
q_rot, k_rot = apply_rotary_pos_emb_interleave(q_rot, k_rot, cos, sin, unsqueeze_dim=2)… lines 233–404 omitted …
q_rot, k_rot = apply_rotary_pos_emb_interleave(q_rot, k_rot, cos, sin)Contextual evidence from Rotate shared key
Rotary coefficients: default RoPE, inverse frequencies θ^(−2j/d) over the rotary slice, cosine and sine computed in float32 for the current positions and cast to the activations’ type, with no rescaling (the attention factor is 1).
rope · huggingface/transformers / modeling_glm_moe_dsa.py
Pinned revision 5e4d6304de55 ↗ · lines 68–122
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class GlmMoeDsaRotaryEmbedding(nn.Module):
@deprecate_kwarg("device", version="5.18")
def __init__(self, config: GlmMoeDsaConfig, device=None):
super().__init__()
self.max_seq_len_cached = config.max_position_embeddings
self.original_max_seq_len = config.max_position_embeddings
self.config = config
self.rope_type = self.config.rope_parameters["rope_type"]
rope_init_fn: Callable = self.compute_default_rope_parameters
if self.rope_type != "default":
rope_init_fn = ROPE_INIT_FUNCTIONS[self.rope_type]
inv_freq, self.attention_scaling = rope_init_fn(self.config, device)
self.inv_freq = nn.Buffer(inv_freq, persistent=False)
self.original_inv_freq = nn.Buffer(inv_freq.clone(), persistent=False)
@staticmethod
@deprecate_kwarg("device", version="5.18")
def compute_default_rope_parameters(config: GlmMoeDsaConfig, device=None, **kwargs) -> tuple[torch.Tensor, float]:
"""
Computes the inverse frequencies according to the original RoPE implementation
Args:
config ([`~transformers.PreTrainedConfig`]):
The model configuration.
Returns:
Tuple of (`torch.Tensor`, `float`), containing the inverse frequencies for the RoPE embeddings and the
post-processing scaling factor applied to the computed cos/sin (unused in this type of RoPE).
"""
base = config.rope_parameters["rope_theta"]
dim = getattr(config, "head_dim", None) or config.hidden_size // config.num_attention_heads
attention_factor = 1.0 # Unused in this type of RoPE
# Compute the inverse frequencies
inv_freq = 1.0 / (base ** (torch.arange(0, dim, 2, dtype=torch.float) / dim))
return inv_freq.to(device), attention_factor
@torch.no_grad()
@dynamic_rope_update # power user: used with advanced RoPE types (e.g. dynamic rope)
def forward(self, x, position_ids):
inv_freq_expanded = (
self.inv_freq[None, :, None].expand(position_ids.shape[0], -1, 1).to(dtype=torch.float, device=x.device)
)
position_ids_expanded = position_ids[:, None, :].float()
device_type = x.device.type if isinstance(x.device.type, str) else "cpu"
# Disable any outside autocast context if any, to really force fp32
with maybe_autocast(device_type=device_type, enabled=False):
freqs = (inv_freq_expanded @ position_ids_expanded).transpose(1, 2)
emb = torch.cat((freqs, freqs), dim=-1)
cos = emb.cos() * self.attention_scaling
sin = emb.sin() * self.attention_scaling
return cos.to(dtype=x.dtype), sin.to(dtype=x.dtype)Contextual evidence from KV cache · rotated keys
The cache is updated while the key–value latent is still compressed: the normalized latent and the rotated key go in, every cached latent and rotated key come back, and the key and value heads are expanded from all of them on every call.
kv-cache · huggingface/transformers / modeling_glm_moe_dsa.py
Pinned revision 5e4d6304de55 ↗ · lines 362–413
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def expand_kv(self, kv_nope: torch.Tensor, k_rot: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
"""Expands the compressed latents into key and value states. Args:
- kv_nope: key + value without positional encoding, shape [batch_size, 1, seqlen, self.kv_lora_rank]
- k_rot: shared key with positional encoding, shape [batch_size, 1, seqlen, self.qk_rope_head_dim]
Returns the key and value states, two tensors of shape [batch, num_heads, seq, (k or v)_head_dim].
"""
batch_size, _, seq_length, _ = kv_nope.shape
key_shape = (batch_size, seq_length, -1, self.qk_nope_head_dim + self.v_head_dim)
kv_nope = self.kv_b_proj(kv_nope).view(key_shape).transpose(1, 2)
k_nope, value_states = torch.split(kv_nope, [self.qk_nope_head_dim, self.v_head_dim], dim=-1)
k_rot = k_rot.expand(-1, k_nope.shape[1], -1, -1) # does not affect the underlying storage
# Concatenate k_nope and k_rot in a new tensor
key_states = kv_nope.new_empty(*kv_nope.shape[:-1], self.qk_nope_head_dim + self.qk_rope_head_dim)
key_states[..., : self.qk_nope_head_dim].copy_(k_nope)
key_states[..., self.qk_nope_head_dim :].copy_(k_rot)
return key_states, value_states… lines 380–403 omitted …
cos, sin = position_embeddings
q_rot, k_rot = apply_rotary_pos_emb_interleave(q_rot, k_rot, cos, sin)
# Cache read / write is performed while latent KV is still compressed
if past_key_values is not None:
k_pass, k_rot = past_key_values.update(k_pass, k_rot, self.layer_idx)
query_states = torch.cat((q_pass, q_rot), dim=-1)
key_states, value_states = self.expand_kv(k_pass, k_rot)