Merge pull request #1851 from C43H66N12O12S2/flash

xformers attention

modules/sd_hijack_optimizations.py

@@ -1,7 +1,14 @@
 import math
 import torch
 from torch import einsum
-
+try:
+    import xformers.ops
+    import functorch
+    xformers._is_functorch_available = True
+    shared.xformers_available = True
+except:
+    print('Cannot find xformers, defaulting to split attention. Try setting --xformers in your webui-user file if you wish to install it.')
+    continue
 from ldm.util import default
 from einops import rearrange
 
@@ -115,6 +122,25 @@ def split_cross_attention_forward(self, x, context=None, mask=None):
 
     return self.to_out(r2)
 
+def xformers_attention_forward(self, x, context=None, mask=None):
+    h = self.heads
+    q_in = self.to_q(x)
+    context = default(context, x)
+    hypernetwork = shared.selected_hypernetwork()
+    hypernetwork_layers = (hypernetwork.layers if hypernetwork is not None else {}).get(context.shape[2], None)
+    if hypernetwork_layers is not None:
+        k_in = self.to_k(hypernetwork_layers[0](context))
+        v_in = self.to_v(hypernetwork_layers[1](context))
+    else:
+        k_in = self.to_k(context)
+        v_in = self.to_v(context)
+    q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> b n h d', h=h), (q_in, k_in, v_in))
+    del q_in, k_in, v_in
+    out = xformers.ops.memory_efficient_attention(q, k, v, attn_bias=None)
+
+    out = rearrange(out, 'b n h d -> b n (h d)', h=h)
+    return self.to_out(out)
+
 def cross_attention_attnblock_forward(self, x):
         h_ = x
         h_ = self.norm(h_)
@@ -177,3 +203,13 @@ def cross_attention_attnblock_forward(self, x):
         h3 += x
 
         return h3
+    
+def xformers_attnblock_forward(self, x):
+        h_ = x
+        h_ = self.norm(h_)
+        q1 = self.q(h_).contiguous()
+        k1 = self.k(h_).contiguous()
+        v = self.v(h_).contiguous()
+        out = xformers.ops.memory_efficient_attention(q1, k1, v)
+        out = self.proj_out(out)
+        return x+out