Merge pull request algorithmicsuperintelligence#215 from codelion/fix-update-doc-readme

clarify prompt design

Author: codelion

README.md

@@ -337,6 +337,40 @@ Sample configuration files are available in the `configs/` directory:
 - `default_config.yaml`: Comprehensive configuration with all available options
 - `island_config_example.yaml`: Advanced island-based evolution setup
 
+### Prompt Engineering Design
+
+OpenEvolve uses a sophisticated prompt engineering approach that separates different types of program examples to optimize LLM learning:
+
+#### Program Selection Strategy
+
+The system distinguishes between three types of program examples shown to the LLM:
+
+1. **Previous Attempts** (`num_top_programs`): Shows only the best performing programs to demonstrate high-quality approaches
+   - Used for the "Previous Attempts" section in prompts
+   - Focused on proven successful patterns
+   - Helps LLM understand what constitutes good performance
+
+2. **Top Programs** (`num_top_programs + num_diverse_programs`): Broader selection including both top performers and diverse approaches
+   - Used for the "Top Performing Programs" section
+   - Includes diverse programs to prevent local optima
+   - Balances exploitation of known good solutions with exploration of novel approaches
+
+3. **Inspirations** (`num_top_programs`): Cross-island program samples for creative inspiration
+   - Derived from other evolution islands to maintain diversity
+   - Count automatically configures based on `num_top_programs` setting
+   - Prevents convergence by exposing LLM to different evolutionary trajectories
+
+#### Design Rationale
+
+This separation is intentional and serves multiple purposes:
+
+- **Focused Learning**: Previous attempts show only the best patterns, helping LLM understand quality standards
+- **Diversity Maintenance**: Top programs include diverse solutions to encourage exploration beyond local optima  
+- **Cross-Pollination**: Inspirations from other islands introduce novel approaches and prevent stagnation
+- **Configurable Balance**: Adjust `num_top_programs` and `num_diverse_programs` to control exploration vs exploitation
+
+The inspiration count automatically scales with `num_top_programs` to maintain consistency across different configuration sizes, eliminating the need for a separate configuration parameter.
+
 ### Template Customization
 
 OpenEvolve supports advanced prompt template customization to increase diversity in code evolution:

openevolve/_version.py

@@ -1,3 +1,3 @@
 """Version information for openevolve package."""
 
-__version__ = "0.1.2"
+__version__ = "0.1.3"

openevolve/database.py

@@ -304,18 +304,23 @@ def get(self, program_id: str) -> Optional[Program]:
         """
         return self.programs.get(program_id)
 
-    def sample(self) -> Tuple[Program, List[Program]]:
+    def sample(self, num_inspirations: Optional[int] = None) -> Tuple[Program, List[Program]]:
         """
         Sample a program and inspirations for the next evolution step
 
+        Args:
+            num_inspirations: Number of inspiration programs to sample (defaults to 5 for backward compatibility)
+
         Returns:
             Tuple of (parent_program, inspiration_programs)
         """
         # Select parent program
         parent = self._sample_parent()
 
         # Select inspirations
-        inspirations = self._sample_inspirations(parent, n=5)
+        if num_inspirations is None:
+            num_inspirations = 5  # Default for backward compatibility
+        inspirations = self._sample_inspirations(parent, n=num_inspirations)
 
         logger.debug(f"Sampled parent {parent.id} and {len(inspirations)} inspirations")
         return parent, inspirations
@@ -436,10 +441,10 @@ def get_top_programs(
                 reverse=True,
             )
         else:
-            # Sort by average of all numeric metrics
+            # Sort by combined_score if available, otherwise by average of all numeric metrics
             sorted_programs = sorted(
                 candidates,
-                key=lambda p: safe_numeric_average(p.metrics),
+                key=lambda p: p.metrics.get("combined_score", safe_numeric_average(p.metrics)),
                 reverse=True,
             )
 
@@ -877,7 +882,7 @@ def _update_archive(self, program: Program) -> None:
         # Find worst program among valid programs
         if valid_archive_programs:
             worst_program = min(
-                valid_archive_programs, key=lambda p: safe_numeric_average(p.metrics)
+                valid_archive_programs, key=lambda p: p.metrics.get("combined_score", safe_numeric_average(p.metrics))
             )
 
             # Replace if new program is better
@@ -1279,10 +1284,10 @@ def _enforce_population_limit(self, exclude_program_id: Optional[str] = None) ->
         # Get programs sorted by fitness (worst first)
         all_programs = list(self.programs.values())
 
-        # Sort by average metric (worst first)
+        # Sort by combined_score if available, otherwise by average metric (worst first)
         sorted_programs = sorted(
             all_programs,
-            key=lambda p: safe_numeric_average(p.metrics),
+            key=lambda p: p.metrics.get("combined_score", safe_numeric_average(p.metrics)),
         )
 
         # Remove worst programs, but never remove the best program or excluded program

openevolve/iteration.py

@@ -48,7 +48,7 @@ async def run_iteration_with_shared_db(
 
     try:
         # Sample parent and inspirations from database
-        parent, inspirations = database.sample()
+        parent, inspirations = database.sample(num_inspirations=config.prompt.num_top_programs)
 
         # Get artifacts for the parent program if available
         parent_artifacts = database.get_artifacts(parent.id)

openevolve/process_parallel.py

@@ -153,18 +153,20 @@ def _run_iteration_worker(
         )
 
         # Use config values for limits instead of hardcoding
-        island_top_programs = island_programs[
+        # Programs for LLM display (includes both top and diverse for inspiration)
+        programs_for_prompt = island_programs[
             : _worker_config.prompt.num_top_programs + _worker_config.prompt.num_diverse_programs
         ]
-        island_previous_programs = island_programs[: _worker_config.prompt.num_top_programs]
+        # Best programs only (for previous attempts section, focused on top performers)
+        best_programs_only = island_programs[: _worker_config.prompt.num_top_programs]
 
         # Build prompt
         prompt = _worker_prompt_sampler.build_prompt(
             current_program=parent.code,
             parent_program=parent.code,
             program_metrics=parent.metrics,
-            previous_programs=[p.to_dict() for p in island_previous_programs],
-            top_programs=[p.to_dict() for p in island_top_programs],
+            previous_programs=[p.to_dict() for p in best_programs_only],
+            top_programs=[p.to_dict() for p in programs_for_prompt],
             inspirations=[p.to_dict() for p in inspirations],
             language=_worker_config.language,
             evolution_round=iteration,
@@ -589,7 +591,7 @@ def _submit_iteration(self, iteration: int, island_id: Optional[int] = None) ->
 
             try:
                 # Sample parent and inspirations from the target island
-                parent, inspirations = self.database.sample()
+                parent, inspirations = self.database.sample(num_inspirations=self.config.prompt.num_top_programs)
             finally:
                 # Always restore original island state
                 self.database.current_island = original_island

tests/test_island_isolation.py

@@ -109,7 +109,7 @@ def test_island_isolation_during_evolution(self):
         # Track which islands were sampled
         sampled_islands = []
 
-        def mock_sample():
+        def mock_sample(num_inspirations=None):
             # Record which island was sampled
             sampled_islands.append(self.database.current_island)
             # Return mock parent and inspirations