Add safe dynamic autotune blacklist

helion/autotuner/config_fragment.py

@@ -247,6 +247,26 @@ def differential_mutation(self, a: object, b: object, c: object) -> int:
         return a
 
 
+class DefaultBiasedIntegerFragment(IntegerFragment):
+    """Integer fragment that samples its default value most of the time."""
+
+    def __init__(
+        self,
+        low: int,
+        high: int,
+        default_val: int | None = None,
+        *,
+        default_probability: float,
+    ) -> None:
+        super().__init__(low, high, default_val)
+        self.default_probability = default_probability
+
+    def random(self) -> int:
+        if random.random() < self.default_probability:
+            return self.default()
+        return super().random()
+
+
 @dataclasses.dataclass
 class EnumFragment(ConfigSpecFragment):
     choices: tuple[object, ...]
@@ -285,6 +305,17 @@ def encode(self, value: object) -> list[float]:
         return [1.0 if i == choice_idx else 0.0 for i in range(len(self.choices))]
 
 
+@dataclasses.dataclass
+class DefaultBiasedEnumFragment(EnumFragment):
+    default_probability: float
+
+    def random(self) -> object:
+        if random.random() < self.default_probability:
+            return self.default()
+        choices = [choice for choice in self.choices if choice != self.default()]
+        return random.choice(choices)
+
+
 class BooleanFragment(ConfigSpecFragment):
     def default(self) -> bool:
         return False

helion/autotuner/config_spec.py

@@ -119,6 +119,8 @@
 from .config_fragment import BlockSizeFragment
 from .config_fragment import BooleanFragment
 from .config_fragment import ConfigSpecFragment
+from .config_fragment import DefaultBiasedEnumFragment
+from .config_fragment import DefaultBiasedIntegerFragment
 from .config_fragment import EnumFragment
 from .config_fragment import IntegerFragment
 from .config_fragment import ListOf
@@ -347,6 +349,8 @@ def _get_backend_tunable_keys() -> frozenset[str]:
 EPILOGUE_SUBTILE_DEFAULT_CHOICES = (None, 2)
 EPILOGUE_SUBTILE_MIN_K_HINT = 1024
 EPILOGUE_SUBTILE_MIN_K_HINT_EXTENDED = 16384
+RANGE_INT_RANDOM_DEFAULT_PROBABILITY = 0.95
+RANGE_WARP_SPECIALIZE_RANDOM_DEFAULT_PROBABILITY = 0.90
 # maxnreg values: None means no limit, otherwise limit to this many registers per thread
 # Lower values allow higher occupancy but may hurt performance for register-heavy kernels
 VALID_MAXNREG = (None, 32, 64, 128, 256)
@@ -3056,16 +3060,30 @@ def _fill_missing(self) -> None:
 
 class RangeUnrollFactorSpec(_OptionalIntSpec):
     def _fragment(self, base: ConfigSpec) -> IntegerFragment:
-        return IntegerFragment(0, 4, 0)
+        return DefaultBiasedIntegerFragment(
+            0,
+            4,
+            0,
+            default_probability=RANGE_INT_RANDOM_DEFAULT_PROBABILITY,
+        )
 
 
 class RangeWarpSpecializeSpec(_OptionalBoolSpec):
-    pass
+    def _fragment(self, base: ConfigSpec) -> EnumFragment:
+        return DefaultBiasedEnumFragment(
+            (None, False, True),
+            default_probability=RANGE_WARP_SPECIALIZE_RANDOM_DEFAULT_PROBABILITY,
+        )
 
 
 class RangeNumStagesSpec(_OptionalIntSpec):
     def _fragment(self, base: ConfigSpec) -> IntegerFragment:
-        return IntegerFragment(0, 4, 0)
+        return DefaultBiasedIntegerFragment(
+            0,
+            4,
+            0,
+            default_probability=RANGE_INT_RANDOM_DEFAULT_PROBABILITY,
+        )
 
 
 class RangeMultiBufferSpec(_OptionalBoolSpec):