givens decomposition: apply zrot without copying matrix (#165)

qiskit-community · May 8, 2024 · 13c962f · 13c962f
1 parent e139f89
commit 13c962f
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Showing 2 changed files with 8 additions and 12 deletions.
diff --git a/python/ffsim/linalg/givens.py b/python/ffsim/linalg/givens.py
@@ -168,17 +168,15 @@ def givens_decomposition(
                     right_rotations.append(
                         GivensRotation(c, s, target_index + 1, target_index)
                     )
-                    current_matrix = current_matrix.T.copy()
                     (
-                        current_matrix[target_index + 1],
-                        current_matrix[target_index],
+                        current_matrix[:, target_index + 1],
+                        current_matrix[:, target_index],
                     ) = zrot(
-                        current_matrix[target_index + 1],
-                        current_matrix[target_index],
+                        current_matrix[:, target_index + 1],
+                        current_matrix[:, target_index],
                         c,
                         s,
                     )
-                    current_matrix = current_matrix.T
         else:
             # rotate rows by left multiplication
             for j in range(i + 1):

diff --git a/python/ffsim/qiskit/gates/slater_determinant.py b/python/ffsim/qiskit/gates/slater_determinant.py
@@ -244,16 +244,14 @@ def _givens_decomposition_slater(orbital_coeffs: np.ndarray) -> list[GivensRotat
                 # zero out element j of row i
                 c, s = zrotg(current_matrix[i, j - 1], current_matrix[i, j])
                 rotations.append(GivensRotation(c, s, j, j - 1))
-                current_matrix = current_matrix.T.copy()
                 (
-                    current_matrix[j - 1],
-                    current_matrix[j],
+                    current_matrix[:, j - 1],
+                    current_matrix[:, j],
                 ) = zrot(
-                    current_matrix[j - 1],
-                    current_matrix[j],
+                    current_matrix[:, j - 1],
+                    current_matrix[:, j],
                     c,
                     s,
                 )
-                current_matrix = current_matrix.T
 
     return rotations[::-1]