[GitHub] [tvm] zxybazh commented on a diff in pull request #13399: [MetaSchedule] Fix segfault in gradient based scheduler

[GitBox <gi...@apache.org>]

zxybazh commented on code in PR #13399:
URL: https://github.com/apache/tvm/pull/13399#discussion_r1023535988


##########
tests/python/unittest/test_meta_schedule_task_scheduler.py:
##########
@@ -352,10 +353,85 @@ def test_meta_schedule_task_scheduler_multiple_gradient_based():
         )
 
 
+def test_meta_schedule_task_scheduler_gradient_based_with_null_search_strategy():
+    """
+    When search strategy of one task returns empty list of candidates,
+    the scheduler should continue working as normal for other tasks
+    """
+
+    @ms.derived_object
+    class NullSearchStrategy(ms.search_strategy.PySearchStrategy):
+        def __init__(self, n=0):
+            self.n = n
+
+        def _initialize_with_tune_context(self, context: "TuneContext") -> None:
+            pass
+
+        def pre_tuning(self, *args, **kwargs):
+            pass
+
+        def post_tuning(self):
+            pass
+
+        def generate_measure_candidates(self):
+            """
+            Returns empty list to indicate there is no result from search, while
+            the search isn't ended.
+            """
+            self.n += 1
+            if self.n <= 10:
+                return []
+            return None

Review Comment:
   To fix this you just need to add a check for whether task's runner future has been defined before doing `JoinRunningTask` when round robin rounds has been fullfilled.



##########
tests/python/unittest/test_meta_schedule_task_scheduler.py:
##########
@@ -352,10 +353,85 @@ def test_meta_schedule_task_scheduler_multiple_gradient_based():
         )
 
 
+def test_meta_schedule_task_scheduler_gradient_based_with_null_search_strategy():
+    """
+    When search strategy of one task returns empty list of candidates,
+    the scheduler should continue working as normal for other tasks
+    """
+
+    @ms.derived_object
+    class NullSearchStrategy(ms.search_strategy.PySearchStrategy):
+        def __init__(self, n=0):
+            self.n = n
+
+        def _initialize_with_tune_context(self, context: "TuneContext") -> None:
+            pass
+
+        def pre_tuning(self, *args, **kwargs):
+            pass
+
+        def post_tuning(self):
+            pass
+
+        def generate_measure_candidates(self):
+            """
+            Returns empty list to indicate there is no result from search, while
+            the search isn't ended.
+            """
+            self.n += 1
+            if self.n <= 10:
+                return []
+            return None

Review Comment:
   I noticed that the task scheduler will also fail when you return None directly here, can you please add that as a test case as well?



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