Merge pull request #1127 from agodianel/fix/832-total-power-zero-division

fix: handle empty power history in CPU.total_power() (#832)

Author: benoit-cty

codecarbon/external/hardware.py

@@ -377,12 +377,12 @@ def _get_energy_from_cpus(self, delay: Time) -> Energy:
 
     def total_power(self) -> Power:
         self._power_history.append(self._get_power_from_cpus())
-        if len(self._power_history) == 0:
-            logger.warning("Power history is empty, returning 0 W")
-            return Power.from_watts(0)
         power_history_in_W = [power.W for power in self._power_history]
-        cpu_power = sum(power_history_in_W) / len(power_history_in_W)
         self._power_history = []
+        if not power_history_in_W:
+            logger.warning("No power samples collected, returning 0 W")
+            return Power.from_watts(0)
+        cpu_power = sum(power_history_in_W) / len(power_history_in_W)
         return Power.from_watts(cpu_power)
 
     def measure_power_and_energy(self, last_duration: float) -> Tuple[Power, Energy]:

tests/test_cpu_load.py

@@ -121,3 +121,68 @@ def test_cpu_calculate_power_from_cpu_load_linear(
         for test in tests_values:
             power = cpu._calculate_power_from_cpu_load(tdp, test["cpu_load"], cpu_model)
             self.assertEqual(power, test["expected_power"])
+
+    @mock.patch(
+        "codecarbon.external.hardware.CPU._get_power_from_cpus",
+        return_value=Power.from_watts(0),
+    )
+    def test_cpu_total_power_empty_history(
+        self,
+        mocked_is_psutil_available,
+        mocked_is_powergadget_available,
+        mocked_is_rapl_available,
+        mocked_get_power_from_cpus,
+    ):
+        """Regression test for issue #832: ZeroDivisionError when no power samples collected."""
+        cpu = CPU.from_utils(
+            None, MODE_CPU_LOAD, "Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz", 100
+        )
+        # Simulate an empty power history before calling total_power
+        cpu._power_history = []
+        result = cpu.total_power()
+        # Should NOT raise ZeroDivisionError, should return a valid Power object
+        self.assertIsInstance(result, Power)
+        self.assertEqual(result.W, 0)
+
+    @mock.patch(
+        "codecarbon.external.hardware.CPU._get_power_from_cpus",
+        return_value=Power.from_watts(42),
+    )
+    def test_cpu_total_power_fetches_sample_when_history_is_empty(
+        self,
+        mocked_get_power_from_cpus,
+        mocked_is_psutil_available,
+        mocked_is_powergadget_available,
+        mocked_is_rapl_available,
+    ):
+        """Calling total_power should always fetch the latest sample before averaging."""
+        cpu = CPU.from_utils(
+            None, MODE_CPU_LOAD, "Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz", 100
+        )
+        cpu._power_history = []
+        result = cpu.total_power()
+        self.assertEqual(result.W, 42)
+        mocked_get_power_from_cpus.assert_called_once()
+        self.assertEqual(cpu._power_history, [])
+
+    @mock.patch(
+        "codecarbon.external.hardware.CPU._get_power_from_cpus",
+        return_value=Power.from_watts(30),
+    )
+    def test_cpu_total_power_averages_buffered_and_latest_sample(
+        self,
+        mocked_get_power_from_cpus,
+        mocked_is_psutil_available,
+        mocked_is_powergadget_available,
+        mocked_is_rapl_available,
+    ):
+        cpu = CPU.from_utils(
+            None, MODE_CPU_LOAD, "Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz", 100
+        )
+        cpu._power_history = [Power.from_watts(10), Power.from_watts(20)]
+
+        result = cpu.total_power()
+
+        self.assertEqual(result.W, 20)
+        self.assertEqual(cpu._power_history, [])
+        mocked_get_power_from_cpus.assert_called_once()