fix(frontend-python): round_bit_pattern, prevent exactness argument m…

…isuse

frontends/concrete-python/concrete/fhe/compilation/configuration.py

@@ -4,7 +4,7 @@
 
 import platform
 from dataclasses import dataclass
-from enum import Enum, IntEnum
+from enum import Enum
 from pathlib import Path
 from typing import List, Optional, Tuple, Union, get_type_hints
 
@@ -74,13 +74,13 @@ def parse(cls, string: str) -> "MultiParameterStrategy":
         raise ValueError(message)
 
 
-class Exactness(IntEnum):
+class Exactness(Enum):
     """
     Exactness, to specify for specific operator the implementation preference (default and local).
     """
 
-    EXACT = 0
-    APPROXIMATE = 1
+    APPROXIMATE = "approximate"
+    EXACT = "exact"
 
 
 @dataclass

frontends/concrete-python/concrete/fhe/extensions/round_bit_pattern.py

@@ -242,6 +242,10 @@ def round_bit_pattern(
 
         lsbs_to_remove = lsbs_to_remove.lsbs_to_remove
 
+    if not isinstance(exactness, (Exactness, None.__class__)):
+        msg = "exactness should be of type fhe.Exactness"
+        raise TypeError(msg)
+
     assert isinstance(lsbs_to_remove, int)
 
     def evaluator(

frontends/concrete-python/concrete/fhe/mlir/converter.py

@@ -760,7 +760,7 @@ def tlu(self, ctx: Context, node: Node, preds: List[Conversion]) -> Conversion:
                 variable_input.origin.properties["exactness"]
                 or ctx.configuration.rounding_exactness
             )
-            if exactness == Exactness.APPROXIMATE:
+            if exactness is Exactness.APPROXIMATE:
                 # we clip values to enforce input precision exactly as queried
                 original_bit_width = variable_input.origin.properties["original_bit_width"]
                 lsbs_to_remove = variable_input.origin.properties["kwargs"]["lsbs_to_remove"]

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

@@ -40,7 +40,7 @@ def apply(self, graph: Graph):
                 exactness = self.rounding_exactness
 
             if original_lsbs_to_remove != 0 and final_lsbs_to_remove == 0:
-                if exactness != Exactness.APPROXIMATE:
+                if exactness is not Exactness.APPROXIMATE:
                     self.replace_with_tlu(graph, node)
                 continue
 

frontends/concrete-python/tests/extensions/test_round_bit_pattern.py

@@ -2,6 +2,8 @@
 Tests of 'round_bit_pattern' extension.
 """
 
+import pytest
+
 from concrete import fhe
 
 
@@ -35,3 +37,16 @@ def test_dump_load_auto_rounder():
     assert loaded.input_max == 20
     assert loaded.input_bit_width == 5
     assert loaded.lsbs_to_remove == 2
+
+
+def test_bad_exactness():
+    """
+    Test for incorrect 'exactness' argument.
+    """
+
+    @fhe.compiler({"a": "encrypted"})
+    def f(a):
+        return fhe.round_bit_pattern(a, lsbs_to_remove=1, exactness=True)
+
+    with pytest.raises(TypeError):
+        f.compile([0])