need to cache it

test/unit/test_symbolic_shapetracker.py

@@ -177,8 +177,8 @@ class TestSymbolicExpand(unittest.TestCase):
     vi = Variable("i", 1, 10).bind(3)
     a = Tensor(1).unsqueeze(0).pad((0, 24)).unsqueeze(0).expand((vi, 25))
     self.assertEqual(a.shape, (vi, 25))
-    self.assertIn(a.reshape(25*vi).shape, {(vi*25,), (25*vi,)})
-    self.assertIn(a.reshape(vi*25).shape, {(vi*25,), (25*vi,)})
+    self.assertEqual(a.reshape(25*vi).shape, (vi*25,))
+    self.assertEqual(a.reshape(vi*25).shape, (vi*25,))
 
 class TestSymbolicShrink(unittest.TestCase):
   def test_shrink_symbols_simple(self):

tinygrad/uop/ops.py

@@ -223,13 +223,16 @@ class UOp(MathTrait, metaclass=UOpMetaClass):
         shape = tuple(1 if i in axis_arg else s for i,s in enumerate(shape))
     return ShapeTracker.from_shape(shape)
 
-  @property
+  @functools.cached_property
   def shape(self) -> tuple[sint, ...]:
+    # some ops init the shape
     match self.op:
       case Ops.CONST: return ()
       case Ops.BUFFER: return (self.arg,)
       case Ops.BUFFER_VIEW: return (self.arg[0],)
 
+    # movement ops change the shape
+    # NOTE: ssimplify is required because the shape needs to be canonical
     if self.op in GroupOp.Movement:
       ps = self.src[0].shape
       match self.op:
@@ -243,14 +246,23 @@ class UOp(MathTrait, metaclass=UOpMetaClass):
           if sorted(self.arg) != list(range(len(ps))): raise RuntimeError(f"invalid permutation {self.arg} of len {len(ps)}")
           return tuple(ps[i] for i in self.arg)
         case Ops.PAD:
-          if not all(b>=0 and e>=0 for b,e in self.arg): raise RuntimeError(f"invalid pad {self.arg}")
+          if len(ps) != len(self.arg) or not all(b>=0 and e>=0 for b,e in self.arg): raise RuntimeError(f"invalid pad {self.arg}")
           return tuple(ssimplify(s+b+e) for s,(b,e) in zip(ps, self.arg))
         case Ops.SHRINK:
           # TODO: why do i need resolve here?
-          if not all(resolve(0<=b) and resolve(b<=e) and resolve(e<=s) for s,(b,e) in zip(ps, self.arg)):
+          if len(ps) != len(self.arg) or not all(resolve(0<=b) and resolve(b<=e) and resolve(e<=s) for s,(b,e) in zip(ps, self.arg)):
             raise RuntimeError(f"invalid shrink {self.arg} for {ps}")
           return tuple(ssimplify(e-s) for s,e in self.arg)
-        case Ops.FLIP: return ps
+        case Ops.FLIP:
+          if len(ps) != len(self.arg) or not all(isinstance(x, bool) for x in self.arg): raise RuntimeError(f"bad flip on {ps}, {self.arg}")
+          return ps
+
+    # elementwise ops keep the shape the same
+    if self.op in GroupOp.Elementwise-{Ops.BITCAST}:
+      input_shapes = [x.shape for x in self.src]
+      if not all_same(input_shapes): raise RuntimeError(f"shape mismatch at {self.op}: {input_shapes}")
+      return input_shapes[0]
+
     # TODO: finish this and remove self.st.shape
     assert self.st is not None, f"{self.op} doesn't have a shape"
     return unwrap(self.st).shape