Fix iteration counting and checkpoint logic in evolution

Adjusts evolution start and iteration counting to treat the initial program evaluation as iteration 0, ensuring evolutionary iterations begin at 1 for fresh starts. Updates checkpoint logic to avoid saving at iteration 0 and aligns checkpoint intervals with evolutionary iterations. Adds comprehensive tests for iteration counting and checkpoint boundary conditions.

Author: codelion

openevolve/controller.py

@@ -280,9 +280,20 @@ def force_exit_handler(signum, frame):
 
             self.parallel_controller.start()
 
+            # When starting from iteration 0, we've already done the initial program evaluation
+            # So we need to adjust the start_iteration for the actual evolution
+            evolution_start = start_iteration
+            evolution_iterations = max_iterations
+            
+            # If we just added the initial program at iteration 0, start evolution from iteration 1
+            if should_add_initial and start_iteration == 0:
+                evolution_start = 1
+                # User expects max_iterations evolutionary iterations AFTER the initial program
+                # So we don't need to reduce evolution_iterations
+                
             # Run evolution with improved parallel processing and checkpoint callback
             await self._run_evolution_with_checkpoints(
-                start_iteration, max_iterations, target_score
+                evolution_start, evolution_iterations, target_score
             )
 
         finally:
@@ -444,6 +455,8 @@ async def _run_evolution_with_checkpoints(
             return
 
         # Save final checkpoint if needed
+        # Note: start_iteration here is the evolution start (1 for fresh start, not 0)
+        # max_iterations is the number of evolution iterations to run
         final_iteration = start_iteration + max_iterations - 1
         if final_iteration > 0 and final_iteration % self.config.checkpoint_interval == 0:
             self._save_checkpoint(final_iteration)

openevolve/process_parallel.py

@@ -472,7 +472,8 @@ async def run_evolution(
                         )
 
                     # Checkpoint callback
-                    if completed_iteration % self.config.checkpoint_interval == 0:
+                    # Don't checkpoint at iteration 0 (that's just the initial program)
+                    if completed_iteration > 0 and completed_iteration % self.config.checkpoint_interval == 0:
                         logger.info(f"Checkpoint interval reached at iteration {completed_iteration}")
                         self.database.log_island_status()
                         if checkpoint_callback:

tests/test_iteration_counting.py

@@ -0,0 +1,210 @@
+"""
+Tests for iteration counting and checkpoint behavior
+"""
+
+import asyncio
+import os
+import tempfile
+import unittest
+from unittest.mock import Mock, patch, MagicMock
+
+# Set dummy API key for testing
+os.environ["OPENAI_API_KEY"] = "test"
+
+from openevolve.config import Config
+from openevolve.controller import OpenEvolve
+from openevolve.database import Program, ProgramDatabase
+
+
+class TestIterationCounting(unittest.TestCase):
+    """Tests for correct iteration counting behavior"""
+
+    def setUp(self):
+        """Set up test environment"""
+        self.test_dir = tempfile.mkdtemp()
+        
+        # Create test program
+        self.program_content = """# EVOLVE-BLOCK-START
+def compute(x):
+    return x * 2
+# EVOLVE-BLOCK-END
+"""
+        self.program_file = os.path.join(self.test_dir, "test_program.py")
+        with open(self.program_file, "w") as f:
+            f.write(self.program_content)
+        
+        # Create test evaluator
+        self.eval_content = """
+def evaluate(program_path):
+    return {"score": 0.5, "performance": 0.6}
+"""
+        self.eval_file = os.path.join(self.test_dir, "evaluator.py")
+        with open(self.eval_file, "w") as f:
+            f.write(self.eval_content)
+    
+    def tearDown(self):
+        """Clean up test environment"""
+        import shutil
+        shutil.rmtree(self.test_dir, ignore_errors=True)
+    
+    def test_fresh_start_iteration_counting(self):
+        """Test that fresh start correctly handles iteration 0 as special"""
+        # Test the logic without actually running evolution
+        config = Config()
+        config.max_iterations = 20
+        config.checkpoint_interval = 10
+        
+        # Simulate fresh start
+        start_iteration = 0
+        should_add_initial = True
+        
+        # Apply the logic from controller.py
+        evolution_start = start_iteration
+        evolution_iterations = config.max_iterations
+        
+        if should_add_initial and start_iteration == 0:
+            evolution_start = 1
+            
+        # Verify
+        self.assertEqual(evolution_start, 1, "Evolution should start at iteration 1")
+        self.assertEqual(evolution_iterations, 20, "Should run 20 evolution iterations")
+        
+        # Simulate what process_parallel would do
+        total_iterations = evolution_start + evolution_iterations
+        self.assertEqual(total_iterations, 21, "Total range should be 21 (1 through 20)")
+        
+        # Check checkpoint alignment
+        expected_checkpoints = []
+        for i in range(evolution_start, total_iterations):
+            if i > 0 and i % config.checkpoint_interval == 0:
+                expected_checkpoints.append(i)
+                
+        self.assertEqual(expected_checkpoints, [10, 20], "Checkpoints should be at 10 and 20")
+    
+    def test_resume_iteration_counting(self):
+        """Test that resume correctly continues from checkpoint"""
+        config = Config()
+        config.max_iterations = 10
+        config.checkpoint_interval = 10
+        
+        # Simulate resume from checkpoint 10
+        start_iteration = 11  # Last iteration was 10, so start at 11
+        should_add_initial = False
+        
+        # Apply the logic
+        evolution_start = start_iteration
+        evolution_iterations = config.max_iterations
+        
+        if should_add_initial and start_iteration == 0:
+            evolution_start = 1
+            
+        # Verify
+        self.assertEqual(evolution_start, 11, "Evolution should continue from iteration 11")
+        self.assertEqual(evolution_iterations, 10, "Should run 10 more iterations")
+        
+        # Total iterations
+        total_iterations = evolution_start + evolution_iterations
+        self.assertEqual(total_iterations, 21, "Should run through iteration 20")
+        
+        # Check checkpoint at 20
+        expected_checkpoints = []
+        for i in range(evolution_start, total_iterations):
+            if i > 0 and i % config.checkpoint_interval == 0:
+                expected_checkpoints.append(i)
+                
+        self.assertEqual(expected_checkpoints, [20], "Should checkpoint at 20")
+    
+    def test_checkpoint_boundary_conditions(self):
+        """Test checkpoint behavior at various boundaries"""
+        test_cases = [
+            # (start_iter, max_iter, checkpoint_interval, expected_checkpoints)
+            (1, 100, 10, list(range(10, 101, 10))),  # Standard case
+            (1, 99, 10, list(range(10, 100, 10))),   # Just short of last checkpoint
+            (1, 101, 10, list(range(10, 101, 10))),  # Just past checkpoint
+            (0, 20, 5, [5, 10, 15, 20]),  # Special case with iteration 0
+        ]
+        
+        for start, max_iter, interval, expected in test_cases:
+            # Apply fresh start logic
+            evolution_start = start
+            if start == 0:
+                evolution_start = 1
+                
+            total = evolution_start + max_iter
+            
+            checkpoints = []
+            for i in range(evolution_start, total):
+                if i > 0 and i % interval == 0:
+                    checkpoints.append(i)
+                    
+            self.assertEqual(
+                checkpoints, 
+                expected, 
+                f"Failed for start={start}, max={max_iter}, interval={interval}"
+            )
+    
+    async def test_controller_iteration_behavior(self):
+        """Test actual controller behavior with iteration counting"""
+        config = Config()
+        config.max_iterations = 20
+        config.checkpoint_interval = 10
+        config.database.in_memory = True
+        config.evaluator.parallel_evaluations = 1
+        
+        controller = OpenEvolve(
+            initial_program_path=self.program_file,
+            evaluation_file=self.eval_file,
+            config=config,
+            output_dir=self.test_dir
+        )
+        
+        # Track checkpoint calls
+        checkpoint_calls = []
+        original_save = controller._save_checkpoint
+        controller._save_checkpoint = lambda i: checkpoint_calls.append(i) or original_save(i)
+        
+        # Mock LLM
+        with patch('openevolve.llm.ensemble.LLMEnsemble.generate_with_context') as mock_llm:
+            mock_llm.return_value = '''```python
+# EVOLVE-BLOCK-START
+def compute(x):
+    return x << 1
+# EVOLVE-BLOCK-END
+```'''
+            
+            # Run with limited iterations to test
+            await controller.run(iterations=20)
+            
+        # Verify checkpoints were called correctly
+        # Note: We expect checkpoints at 10 and 20
+        self.assertIn(10, checkpoint_calls, "Should checkpoint at iteration 10")
+        self.assertIn(20, checkpoint_calls, "Should checkpoint at iteration 20")
+        
+        # Verify we have the right number of programs (initial + 20 evolution)
+        # This may vary due to parallel execution, but should be at least 21
+        self.assertGreaterEqual(
+            len(controller.database.programs), 
+            21, 
+            "Should have at least 21 programs (initial + 20 iterations)"
+        )
+
+
+if __name__ == "__main__":
+    # Run async test
+    suite = unittest.TestLoader().loadTestsFromTestCase(TestIterationCounting)
+    runner = unittest.TextTestRunner(verbosity=2)
+    result = runner.run(suite)
+    
+    # Run the async test separately
+    async def run_async_test():
+        test = TestIterationCounting()
+        test.setUp()
+        try:
+            await test.test_controller_iteration_behavior()
+            print("✓ test_controller_iteration_behavior passed")
+        except Exception as e:
+            print(f"✗ test_controller_iteration_behavior failed: {e}")
+        finally:
+            test.tearDown()
+    
+    asyncio.run(run_async_test())