sync https://github.com/JL-er/RWKV-PEFT

finetune/lora/v6/fla/ops/abc/naive.py

@@ -0,0 +1,90 @@
+# -*- coding: utf-8 -*-
+
+from typing import Optional
+
+import torch
+
+
+def naive_recurrent_abc(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    s: torch.Tensor,
+    g: Optional[torch.Tensor] = None,
+    scale: Optional[int] = None,
+    initial_state: Optional[torch.Tensor] = None,
+    output_final_state: Optional[bool] = False
+) -> torch.Tensor:
+    dtype = q.dtype
+
+    # [batch_size, n_heads, seq_len, n_slots]
+    if g is None:
+        z = s.float().logcumsumexp(2)
+        g = torch.cat((z[:, :, :1], z[:, :, :-1]), 2) - z
+        s = torch.exp(s - z)
+    q, k, v, s, g = map(lambda x: x.float(), (q, k, v, s, g))
+    B, H, T, K, V, M = *q.shape, v.shape[-1], s.shape[-1]
+
+    hk = torch.zeros(B, H, K, M, dtype=torch.float, device=q.device)
+    ok = torch.zeros_like(s)
+
+    if scale is None:
+        scale = q.shape[-1] ** -0.5
+
+    final_state = None
+    if initial_state is not None:
+        hk += initial_state[0]
+
+    for i in range(T):
+        q_i = q[:, :, i] * scale
+        k_i = k[:, :, i]
+        v_i = s[:, :, i]
+        g_i = g[:, :, i].exp()
+        hk = hk * g_i[..., None, :] + k_i[..., None] * v_i[..., None, :]
+        ok[:, :, i] = (q_i[..., None] * hk).sum(-2)
+
+    qv = ok.softmax(-1)
+    hv = torch.zeros(B, H, M, V, dtype=torch.float, device=q.device)
+    ov = torch.zeros_like(v)
+    if initial_state is not None:
+        hv += initial_state[1]
+
+    for i in range(T):
+        q_i = qv[:, :, i]
+        k_i = s[:, :, i]
+        v_i = v[:, :, i]
+        g_i = g[:, :, i].exp()
+        hv = hv * g_i[..., :, None] + k_i[..., None] * v_i[..., None, :]
+        ov[:, :, i] = (q_i[..., None] * hv).sum(-2)
+
+    if output_final_state:
+        final_state = (hk, hv)
+    return ov.to(dtype), final_state
+
+
+def naive_cumsum_abc(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    s: torch.Tensor
+) -> torch.Tensor:
+    """
+    A simple implementation of vanilla ABC that is more aligned with the descriptions in the paper.
+    This is just for demonstration purposes, with no numerical stabilities guaranteed.
+    """
+
+    dtype = q.dtype
+    q, k, v, s = map(lambda x: x.float(), (q, k, v, s))
+
+    scale = q.shape[-1] ** -0.5
+    # [batch_size, n_heads, seq_len, n_slots]
+    s = (s - s.max(2, True)[0]).exp()
+    z = s.cumsum(2)
+    # [batch_size, n_heads, seq_len, n_slots, d_head]
+    K = (s.unsqueeze(-1) * k.unsqueeze(-2)).cumsum(2) / z.unsqueeze(-1)
+    V = (s.unsqueeze(-1) * v.unsqueeze(-2)).cumsum(2) / z.unsqueeze(-1)
+    # [batch_size, n_heads, seq_len, n_slots]
+    p = torch.einsum('...d,...md->...m', q * scale, K).softmax(-1)
+    # [batch_size, n_heads, seq_len, d_head]
+    o = torch.einsum('...m,...md->...d', p, V)
+    return o.to(dtype), None