[None][fix] clamp very small non-zero sampling temperature

tensorrt_llm/sampling_params.py

@@ -1,4 +1,5 @@
 import json
+import math
 import os
 from abc import ABC, abstractmethod
 from dataclasses import dataclass, field, fields
@@ -122,6 +123,12 @@ def __call__(
         pass  # noqa
 
 
+# Smallest non-zero temperature forwarded to the sampling backend. Positive
+# values below this overflow logits / temperature to inf/nan in fp16/bf16, so
+# they are clamped up to this floor. temperature == 0 (greedy) is left as-is.
+MIN_SAMPLING_TEMPERATURE = 1e-2
+
+
 @dataclass(slots=True, kw_only=True)
 class SamplingParams:
     """Sampling parameters for text generation.
@@ -318,8 +325,14 @@ def _validate(self):
             raise ValueError(f"require 0 <= top_p <= 1, got top_p={self.top_p}")
         if self.top_k is not None and self.top_k < 0:
             raise ValueError(f"require top_k >= 0, got top_k={self.top_k}")
+        if self.temperature is not None and not math.isfinite(self.temperature):
+            raise ValueError(f"temperature must be finite, got temperature={self.temperature}")
         if self.temperature is not None and self.temperature < 0:
             raise ValueError(f"require temperature >= 0, got temperature={self.temperature}")
+        # Clamp very small non-zero temperatures up to a numerically safe floor;
+        # keep 0.0 as-is so greedy decoding is unaffected.
+        if self.temperature is not None and 0 < self.temperature < MIN_SAMPLING_TEMPERATURE:
+            self.temperature = MIN_SAMPLING_TEMPERATURE
 
         if self.best_of is not None and self.best_of < self.n:
             raise ValueError(f"best_of ({self.best_of}) cannot be less than n ({self.n})")

tests/unittest/llmapi/test_sampling_params.py

@@ -0,0 +1,50 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import math
+
+import pytest
+
+from tensorrt_llm.sampling_params import MIN_SAMPLING_TEMPERATURE, SamplingParams
+
+
+def test_temperature_none_unchanged() -> None:
+    assert SamplingParams().temperature is None
+
+
+def test_temperature_zero_kept_for_greedy() -> None:
+    # 0.0 means greedy decoding and must not be clamped.
+    assert SamplingParams(temperature=0.0).temperature == 0.0
+
+
+@pytest.mark.parametrize("tiny", [1e-12, 1e-6, MIN_SAMPLING_TEMPERATURE / 2])
+def test_tiny_positive_temperature_clamped(tiny: float) -> None:
+    # Assert against the contractual floor (1e-2), not the constant.
+    assert SamplingParams(temperature=tiny).temperature == 1e-2
+
+
+@pytest.mark.parametrize("temp", [MIN_SAMPLING_TEMPERATURE, 0.5, 1.0, 2.0])
+def test_normal_temperature_unchanged(temp: float) -> None:
+    assert SamplingParams(temperature=temp).temperature == temp
+
+
+def test_negative_temperature_rejected() -> None:
+    with pytest.raises(ValueError, match="temperature"):
+        SamplingParams(temperature=-1.0)
+
+
+@pytest.mark.parametrize("bad", [math.nan, math.inf, -math.inf])
+def test_non_finite_temperature_rejected(bad: float) -> None:
+    with pytest.raises(ValueError, match="finite"):
+        SamplingParams(temperature=bad)