fix window size of none for scalable vit for rectangular images

Author: lucidrains

setup.py

@@ -3,7 +3,7 @@
 setup(
   name = 'vit-pytorch',
   packages = find_packages(exclude=['examples']),
-  version = '0.28.1',
+  version = '0.28.2',
   license='MIT',
   description = 'Vision Transformer (ViT) - Pytorch',
   author = 'Phil Wang',

vit_pytorch/scalable_vit.py

@@ -156,8 +156,8 @@ def __init__(
     def forward(self, x):
         height, width, heads, wsz = *x.shape[-2:], self.heads, self.window_size
 
-        wsz = default(wsz, height) # take height as window size if not given
-        assert (height % wsz) == 0 and (width % wsz) == 0, f'height ({height}) or width ({width}) of feature map is not divisible by the window size ({wsz})'
+        wsz_h, wsz_w = default(wsz, height), default(wsz, width)
+        assert (height % wsz_h) == 0 and (width % wsz_w) == 0, f'height ({height}) or width ({width}) of feature map is not divisible by the window size ({wsz_h}, {wsz_w})'
 
         q, k, v = self.to_q(x), self.to_k(x), self.to_v(x)
 
@@ -167,7 +167,7 @@ def forward(self, x):
 
         # divide into window (and split out heads) for efficient self attention
 
-        q, k, v = map(lambda t: rearrange(t, 'b (h d) (x w1) (y w2) -> (b x y) h (w1 w2) d', h = heads, w1 = wsz, w2 = wsz), (q, k, v))
+        q, k, v = map(lambda t: rearrange(t, 'b (h d) (x w1) (y w2) -> (b x y) h (w1 w2) d', h = heads, w1 = wsz_h, w2 = wsz_w), (q, k, v))
 
         # similarity
 
@@ -183,7 +183,7 @@ def forward(self, x):
 
         # reshape the windows back to full feature map (and merge heads)
 
-        out = rearrange(out, '(b x y) h (w1 w2) d -> b (h d) (x w1) (y w2)', x = height // wsz, y = width // wsz, w1 = wsz, w2 = wsz)
+        out = rearrange(out, '(b x y) h (w1 w2) d -> b (h d) (x w1) (y w2)', x = height // wsz_h, y = width // wsz_w, w1 = wsz_h, w2 = wsz_w)
 
         # add LIM output