Add fake_impl for unique_consecutive (#145649)

Summary:
It's fairly similar to torch.unique and torch.unique_dim.

Test Plan:
New test

Pull Request resolved: https://github.com/pytorch/pytorch/pull/145649
Approved by: https://github.com/ezyang, https://github.com/eellison

test/dynamo/test_misc.py

@@ -2643,6 +2643,18 @@ utils_device.CURRENT_DEVICE == None""".split(
         self.assertEqual(r.dtype, torch.int64)
         self.assertEqual(cnts.frame_count, 1)
 
+    @torch._dynamo.config.patch(capture_dynamic_output_shape_ops=True)
+    def test_unique_consecutive(self):
+        x = torch.tensor([1, 1, 2, 2, 1, 3])
+
+        def fn(x):
+            return torch.unique_consecutive(x)
+
+        expected = fn(x)
+        opt_fn = torch.compile(fn, fullgraph=True, backend="eager")
+        result = opt_fn(x)
+        self.assertEqual(result, expected)
+
     def test_numpy_unique_f16(self):
         def fn():
             x = np.asarray([1, 1, 2, 2, 3], dtype=np.float16)

test/test_proxy_tensor.py

@@ -2011,7 +2011,6 @@ symbolic_tensor_failures = {
     xfail('nn.functional.cross_entropy', ''),  # aten.size.default - couldn't find symbolic meta function/decomposition
     xfail('nn.functional.ctc_loss'),  # aten._ctc_loss.Tensor - couldn't find symbolic meta function/decomposition
     xfail('quantile', ''),  # Could not run 'aten::equal' with arguments from the 'Meta' backend.
-    xfail('unique_consecutive', ''),  # aten.unique_consecutive.default - couldn't find symbolic meta function/decomposition
 
     xfail('max_pool2d_with_indices_backward', ''),  # Expected a value of type 'List[int]' for argument 'kernel_size' but...
 }

torch/_subclasses/fake_impls.py

@@ -274,7 +274,15 @@ def dyn_shape(fake_mode, func, *args, **kwargs):
 
 
 def _unique(
-    fake_mode, func, arg, dim, sorted=True, return_inverse=False, return_counts=False
+    fake_mode,
+    func,
+    arg,
+    dim,
+    sorted=True,
+    return_inverse=False,
+    return_counts=False,
+    *,
+    unique_consecutive=False,
 ):
     if (
         fake_mode.shape_env is None
@@ -283,8 +291,10 @@ def _unique(
         # Without symints/symfloats, cannot handle this
         raise DynamicOutputShapeException(func)
 
+    nnz = arg.unique_consecutive_memo if unique_consecutive else arg.unique_memo
+
     # Do not use a memo for unique_dim
-    if dim is not None or (nnz := arg.unique_memo) is None:
+    if dim is not None or nnz is None:
         # Avoid importing sympy at a module level
         from torch.fx.experimental.symbolic_shapes import (
             _constrain_range_for_size,
@@ -313,7 +323,10 @@ def _unique(
             _constrain_range_for_size(nnz, max=maxval)
 
         if dim is None:
-            arg.unique_memo = nnz
+            if unique_consecutive:
+                arg.unique_consecutive_memo = nnz
+            else:
+                arg.unique_memo = nnz
 
     if dim is None:
         ret = [arg.new_empty((nnz,))]
@@ -359,6 +372,20 @@ def unique_dim(
     )
 
 
+@register_op_impl(aten.unique_consecutive.default)
+def _(fake_mode, func, arg, return_inverse=False, return_counts=False, dim=None):
+    return _unique(
+        fake_mode,
+        func,
+        arg,
+        dim,
+        False,
+        return_inverse,
+        return_counts,
+        unique_consecutive=True,
+    )
+
+
 @register_op_impl(aten.repeat_interleave.Tensor)
 def repeat_interleave_tensor(fake_mode, func, repeats, output_size=None):
     if output_size is None:

torch/_subclasses/fake_tensor.py

@@ -619,6 +619,7 @@ class FakeTensor(Tensor):
     nonzero_memo = SymNumberMemoDescriptor()
     item_memo = SymNumberMemoDescriptor()
     unique_memo = SymNumberMemoDescriptor()
+    unique_consecutive_memo = SymNumberMemoDescriptor()
 
     # We expect nested_int_memo to be None when an offsets is a graph
     # intermediate, or an input that has never been associated with a
@@ -721,6 +722,7 @@ class FakeTensor(Tensor):
         self.nonzero_memo = None
         self.item_memo = None
         self.unique_memo = None
+        self.unique_consecutive_memo = None
         self.nested_int_memo = None
 
         if FakeTensorConfig.debug: