From e0f66688c432fe70325adff96498ddb1f849c03b Mon Sep 17 00:00:00 2001
From: ZY Liu <236001964+liuzhengyang699@users.noreply.github.com>
Date: Sun, 11 Oct 2026 00:21:04 +0800
Subject: [PATCH] fix: fill available inspiration slots in small islands

---
 openevolve/database.py                  |  5 ++--
 tests/test_small_island_inspirations.py | 40 +++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_small_island_inspirations.py

diff --git a/openevolve/database.py b/openevolve/database.py
index 0f487c0ec..049899206 100644
--- a/openevolve/database.py
+++ b/openevolve/database.py
@@ -30,7 +30,7 @@
     ProgramState,
 )
 from openevolve.utils.code_utils import calculate_edit_distance
-from openevolve.utils.metrics_utils import safe_numeric_average, get_fitness_score
+from openevolve.utils.metrics_utils import get_fitness_score, safe_numeric_average
 
 logger = logging.getLogger(__name__)
 
@@ -1136,6 +1136,7 @@ def _llm_judge_novelty(self, program: Program, similar_program: Program) -> bool
         Use LLM to judge if a program is novel compared to a similar existing program
         """
         import asyncio
+
         from openevolve.novelty_judge import NOVELTY_SYSTEM_MSG, NOVELTY_USER_MSG
 
         user_msg = NOVELTY_USER_MSG.format(
@@ -1791,7 +1792,7 @@ def _sample_inspirations(
                 inspirations.append(program)
 
         # Add diverse programs from within the island
-        if len(island_programs) > n and len(inspirations) < n:
+        if len(inspirations) < n:
             remaining_slots = n - len(inspirations)
 
             # Try to sample from different feature cells within the island
diff --git a/tests/test_small_island_inspirations.py b/tests/test_small_island_inspirations.py
new file mode 100644
index 000000000..1bf2c0ee0
--- /dev/null
+++ b/tests/test_small_island_inspirations.py
@@ -0,0 +1,40 @@
+"""Small islands should still contribute their available inspiration programs."""
+
+import unittest
+
+from openevolve.config import DatabaseConfig
+from openevolve.database import Program, ProgramDatabase
+
+
+class TestSmallIslandInspirations(unittest.TestCase):
+    def setUp(self):
+        self.db = ProgramDatabase(
+            DatabaseConfig(in_memory=True, num_islands=2, elite_selection_ratio=0.2)
+        )
+        self.parent = Program(id="parent", code="parent", metrics={"score": 1.0})
+        self.best = Program(id="best", code="best", metrics={"score": 3.0})
+        self.other = Program(id="other", code="other", metrics={"score": 2.0})
+        outsider = Program(id="outsider", code="outsider", metrics={"score": 4.0})
+        self.db.programs = {p.id: p for p in [self.parent, self.best, self.other, outsider]}
+        self.db.islands = [{"parent", "best", "other"}, {"outsider"}]
+        self.db.island_best_programs = ["best", "outsider"]
+
+    def test_fills_available_slots_when_island_is_no_larger_than_request(self):
+        for requested in (3, 5):
+            with self.subTest(requested=requested):
+                inspirations = self.db._sample_inspirations(self.parent, n=requested, island_id=0)
+                self.assertEqual([p.id for p in inspirations][0], "best")
+                self.assertCountEqual([p.id for p in inspirations], ["best", "other"])
+
+    def test_respects_smaller_request(self):
+        inspirations = self.db._sample_inspirations(self.parent, n=1, island_id=0)
+        self.assertEqual([p.id for p in inspirations], ["best"])
+
+    def test_parent_only_island_has_no_inspirations(self):
+        self.db.islands[0] = {"parent"}
+        self.db.island_best_programs[0] = "parent"
+        self.assertEqual(self.db._sample_inspirations(self.parent, n=5, island_id=0), [])
+
+
+if __name__ == "__main__":
+    unittest.main()