Implement bucketize in torch aten ops (#7396) (#8007)

Co-authored-by: Simon Teo <[email protected]>

Author: simonteozw

experimental/torch_xla2/test/test_ops.py

@@ -16,7 +16,6 @@
     "_upsample_bilinear2d_aa",
     "bincount", # NOTE: dtype for int input torch gives float. This is weird.
     "block_diag",
-    "bucketize",
     "byte",
     "cat",
     "cauchy",

experimental/torch_xla2/torch_xla2/ops/jaten.py

@@ -698,6 +698,11 @@ def fix_dim(p):
   new_shape = [p for i, p in enumerate(self.shape) if i not in dim or p != 1]
   return self.reshape(new_shape)
 
+@op(torch.ops.aten.bucketize)
+def _aten_bucketize(input, boundaries, *, out_int32=False, right=False, out=None):
+  assert boundaries[0] < boundaries[-1], "boundaries must contain a strictly increasing sequence"
+  return_type = jnp.int32 if out_int32 else jnp.int64
+  return jnp.digitize(input, boundaries, right=not right).astype(return_type)
 
 @op(torch.ops.aten.convolution)
 def _aten_convolution(