Merge pull request #1182 from adler-j/issue-1181__l1_prox_bug

BUG: Fix bug with aliased input to l1_cconj proximal, closes #1181

odl/solvers/nonsmooth/proximal_operators.py

@@ -1035,7 +1035,11 @@ def _call(self, x, out):
             if g is not None:
                 diff = x - self.sigma * g
             else:
-                diff = x
+                if x is out:
+                    # Handle aliased data properly
+                    diff = x.copy()
+                else:
+                    diff = x
 
             if isotropic:
                 # Calculate |x| = pointwise 2-norm of x

odl/test/solvers/nonsmooth/proximal_operator_test.py

@@ -295,14 +295,23 @@ def test_proximal_convconj_l1_simple_space_without_data():
     assert isinstance(prox, odl.Operator)
 
     # Apply the proximal operator returning its optimal point
-    x_opt = space.element()
-    prox(x, x_opt)
-
     # Explicit computation: x / max(lam, |x|)
     denom = np.maximum(lam, np.sqrt(x_arr ** 2))
-    x_verify = lam * x_arr / denom
+    x_exact = lam * x_arr / denom
 
-    assert all_almost_equal(x_opt, x_verify, HIGH_ACC)
+    # Using out
+    x_opt = space.element()
+    x_result = prox(x, x_opt)
+    assert x_result is x_opt
+    assert all_almost_equal(x_opt, x_exact, HIGH_ACC)
+
+    # Without out
+    x_result = prox(x)
+    assert all_almost_equal(x_result, x_exact, HIGH_ACC)
+
+    # With aliased out
+    x_result = prox(x, x)
+    assert all_almost_equal(x_result, x_exact, HIGH_ACC)
 
 
 def test_proximal_convconj_l1_simple_space_with_data():