Move input validation out of _inverse_pattern and _get_ordered_swap

crates/accelerate/src/permutation.rs

@@ -77,12 +77,20 @@ fn get_ordered_swap(pattern: &ArrayView1<i64>) -> Vec<(i64, i64)> {
     swaps
 }
 
+/// Checks whether an array of size N is a permutation of 0, 1, ..., N - 1.
+#[pyfunction]
+#[pyo3(signature = (pattern))]
+fn _validate_permutation(py: Python, pattern: PyArrayLike1<i64>) -> PyResult<PyObject> {
+    let view = pattern.as_array();
+    validate_permutation(&view)?;
+    Ok(py.None())
+}
+
 /// Finds inverse of a permutation pattern.
 #[pyfunction]
 #[pyo3(signature = (pattern))]
 fn _inverse_pattern(py: Python, pattern: PyArrayLike1<i64>) -> PyResult<PyObject> {
     let view = pattern.as_array();
-    validate_permutation(&view)?;
     let inverse_i64: Vec<i64> = invert(&view).iter().map(|&x| x as i64).collect();
     Ok(inverse_i64.to_object(py))
 }
@@ -100,12 +108,12 @@ fn _inverse_pattern(py: Python, pattern: PyArrayLike1<i64>) -> PyResult<PyObject
 #[pyo3(signature = (permutation_in))]
 fn _get_ordered_swap(py: Python, permutation_in: PyArrayLike1<i64>) -> PyResult<PyObject> {
     let view = permutation_in.as_array();
-    validate_permutation(&view)?;
     Ok(get_ordered_swap(&view).to_object(py))
 }
 
 #[pymodule]
 pub fn permutation(m: &Bound<PyModule>) -> PyResult<()> {
+    m.add_function(wrap_pyfunction!(_validate_permutation, m)?)?;
     m.add_function(wrap_pyfunction!(_inverse_pattern, m)?)?;
     m.add_function(wrap_pyfunction!(_get_ordered_swap, m)?)?;
     Ok(())

qiskit/synthesis/permutation/permutation_utils.py

@@ -13,7 +13,11 @@
 """Utility functions for handling permutations."""
 
 # pylint: disable=unused-import
-from qiskit._accelerate.permutation import _inverse_pattern, _get_ordered_swap
+from qiskit._accelerate.permutation import (
+    _inverse_pattern,
+    _get_ordered_swap,
+    _validate_permutation,
+)
 
 
 def _pattern_to_cycles(pattern):

test/python/synthesis/test_permutation_synthesis.py

@@ -25,7 +25,11 @@
     synth_permutation_basic,
     synth_permutation_reverse_lnn_kms,
 )
-from qiskit.synthesis.permutation.permutation_utils import _inverse_pattern, _get_ordered_swap
+from qiskit.synthesis.permutation.permutation_utils import (
+    _inverse_pattern,
+    _get_ordered_swap,
+    _validate_permutation,
+)
 from test import QiskitTestCase  # pylint: disable=wrong-import-order
 
 
@@ -58,7 +62,7 @@ def test_get_ordered_swap(self, width):
 
     @data(10, 20)
     def test_invalid_permutations(self, width):
-        """Check that synth_permutation_basic raises exceptions when the
+        """Check that _validate_permutation raises exceptions when the
         input is not a permutation."""
         np.random.seed(1)
         for _ in range(5):
@@ -67,21 +71,21 @@ def test_invalid_permutations(self, width):
             pattern_out_of_range = np.copy(pattern)
             pattern_out_of_range[0] = -1
             with self.assertRaises(ValueError) as exc:
-                _ = synth_permutation_basic(pattern_out_of_range)
+                _validate_permutation(pattern_out_of_range)
                 self.assertIn("input contains a negative number", str(exc.exception))
 
             pattern_out_of_range = np.copy(pattern)
             pattern_out_of_range[0] = width
             with self.assertRaises(ValueError) as exc:
-                _ = synth_permutation_basic(pattern_out_of_range)
+                _validate_permutation(pattern_out_of_range)
                 self.assertIn(
                     "input has length {0} and contains {0}".format(width), str(exc.exception)
                 )
 
             pattern_duplicate = np.copy(pattern)
             pattern_duplicate[-1] = pattern[0]
             with self.assertRaises(ValueError) as exc:
-                _ = synth_permutation_basic(pattern_duplicate)
+                _validate_permutation(pattern_duplicate)
                 self.assertIn(
                     "input contains {} more than once".format(pattern[0]), str(exc.exception)
                 )