Move sort kind validation and add a fast-path for size == 1 arrays

radix sort implementation asserts that array must be of size > 1

Author: ndgrigorian

dpctl/tensor/_sorting.py

@@ -79,12 +79,23 @@ def sort(x, /, *, axis=-1, descending=False, stable=True, kind=None):
         raise TypeError(
             f"Expected type dpctl.tensor.usm_ndarray, got {type(x)}"
         )
+    if not isinstance(kind, str) or kind not in [
+        "stable",
+        "radixsort",
+        "mergesort",
+    ]:
+        raise ValueError(
+            "Unsupported kind value. Expected 'stable', 'mergesort', "
+            f"or 'radixsort', but got '{kind}'"
+        )
     nd = x.ndim
     if nd == 0:
         axis = normalize_axis_index(axis, ndim=1, msg_prefix="axis")
         return dpt.copy(x, order="C")
     else:
         axis = normalize_axis_index(axis, ndim=nd, msg_prefix="axis")
+    if x.size == 1:
+        return dpt.copy(x, order="C")
     a1 = axis + 1
     if a1 == nd:
         perm = list(range(nd))
@@ -96,15 +107,6 @@ def sort(x, /, *, axis=-1, descending=False, stable=True, kind=None):
         arr = dpt.permute_dims(x, perm)
     if kind is None:
         kind = "stable"
-    if not isinstance(kind, str) or kind not in [
-        "stable",
-        "radixsort",
-        "mergesort",
-    ]:
-        raise ValueError(
-            "Unsupported kind value. Expected 'stable', 'mergesort', "
-            f"or 'radixsort', but got '{kind}'"
-        )
     if kind == "mergesort":
         impl_fn = _get_mergesort_impl_fn(descending)
     elif kind == "radixsort":