fix(frontend-python): always increase the clear bit width by one to a…

…void sign extension issues

frontends/concrete-python/concrete/fhe/mlir/processors/assign_bit_widths.py

@@ -119,9 +119,7 @@ def apply_many(self, graphs: Dict[str, Graph]):
             )
 
             if node.output.is_clear:
-                new_bit_width = original_bit_width
-                if not node.output.dtype.is_signed:
-                    new_bit_width += 1
+                new_bit_width = original_bit_width + 1
 
             node.properties["original_bit_width"] = original_bit_width
             node.output.dtype.bit_width = new_bit_width

frontends/concrete-python/tests/execution/test_others.py

@@ -212,6 +212,22 @@ def copy_modify(x):
     return np.concatenate((x, y))
 
 
+def issue650(x):
+    """
+    Function of a reported bug in which bit widths assigned to clear values were wrong.
+    """
+    tmp0 = x
+    tmp1 = [[1], [-1], [-1], [-1], [-1], [-1], [-2], [-1], [0], [0]]
+    tmp2 = np.matmul(tmp0, tmp1)
+    tmp3 = np.sum(tmp0, axis=1, keepdims=True)
+    tmp4 = -1
+    tmp5 = np.multiply(tmp4, tmp3)
+    tmp6 = np.subtract(tmp2, tmp5)
+    tmp7 = [[11]]
+    tmp8 = np.add(tmp6, tmp7)
+    return tmp8
+
+
 @pytest.mark.parametrize(
     "function,parameters,configuration_overrides",
     [
@@ -932,6 +948,14 @@ def copy_modify(x):
                 "{optimize_tlu_based_on_measured_bounds: True}"
             ),
         ),
+        pytest.param(
+            issue650,
+            {
+                "x": {"range": [-2, 1], "status": "encrypted", "shape": (1, 10)},
+            },
+            {},
+            id="issue-650",
+        ),
     ],
 )
 def test_others(function, parameters, configuration_overrides, helpers):