handle failing trials (#505)

* handle failing trials

* clarify when to return {}

* skip ensemble in accuracy check

flaml/tune/trial_runner.py

@@ -103,6 +103,10 @@ class BaseTrialRunner:
             trial.set_status(Trial.TERMINATED)
         elif self._scheduler_alg:
             self._scheduler_alg.on_trial_remove(self, trial)
+            if trial.status == Trial.ERROR:
+                self._search_alg.on_trial_complete(
+                    trial.trial_id, trial.last_result, error=True
+                )
 
 
 class SequentialTrialRunner(BaseTrialRunner):

flaml/tune/tune.py

@@ -18,6 +18,7 @@ except (ImportError, AssertionError):
     ray_import = False
     from .analysis import ExperimentAnalysis as EA
 
+from .trial import Trial
 from .result import DEFAULT_METRIC
 import logging
 
@@ -154,6 +155,12 @@ def run(
         metric2minimize = (round(config['x'])-95000)**2
         time2eval = time.time() - current_time
         tune.report(metric2minimize=metric2minimize, time2eval=time2eval)
+        # if the evaluation fails unexpectedly and the exception is caught,
+        # and it doesn't inform the goodness of the config,
+        # return {}
+        # if the failure indicates a config is bad,
+        # report a bad metric value like np.inf or -np.inf
+        # depending on metric mode being min or max
 
     analysis = tune.run(
         compute_with_config,
@@ -451,7 +458,11 @@ def run(
             result = evaluation_function(trial_to_run.config)
             if result is not None:
                 if isinstance(result, dict):
-                    report(**result)
+                    if result:
+                        report(**result)
+                    else:
+                        # When the result returned is an empty dict, set the trial status to error
+                        trial_to_run.set_status(Trial.ERROR)
                 else:
                     report(_metric=result)
             _runner.stop_trial(trial_to_run)

test/automl/test_notebook_example.py

@@ -84,7 +84,8 @@ def test_automl(budget=5, dataset_format="dataframe", hpo_method=None):
     print(automl.resource_attr)
     print(automl.max_resource)
     print(automl.min_resource)
-    automl.fit(X_train=X_train, y_train=y_train, ensemble=True, **settings)
+    if budget < performance_check_budget:
+        automl.fit(X_train=X_train, y_train=y_train, ensemble=True, **settings)
 
 
 def test_automl_array():

test/nlp/test_autohf.py

@@ -1,7 +1,6 @@
 import sys
 import pytest
 import pickle
-import shutil
 import requests
 
 

test/tune/test_tune.py

@@ -308,6 +308,20 @@ def test_run_training_function_return_value():
         mode="max",
     )
 
+    # Test empty return value
+    def evaluate_config_empty(config):
+        return {}
+
+    tune.run(
+        evaluate_config_empty,
+        config={
+            "x": tune.qloguniform(lower=1, upper=100000, q=1),
+            "y": tune.qlograndint(lower=2, upper=100000, q=2),
+        },
+        num_samples=10,
+        mode="max",
+    )
+
 
 def test_xgboost_bs():
     _test_xgboost()