Struct GEPA 

pub struct GEPA {
    pub num_iterations: usize,
    pub minibatch_size: usize,
    pub num_trials: usize,
    pub temperature: f32,
    pub track_stats: bool,
    pub track_best_outputs: bool,
    pub max_rollouts: Option<usize>,
    pub max_lm_calls: Option<usize>,
    pub prompt_model: Option<LM>,
    pub valset: Option<Vec<Example>>,
}

GEPA Optimizer Configuration

Fields

num_iterations: usize

Maximum number of evolutionary iterations

minibatch_size: usize

Size of minibatch for each rollout

num_trials: usize

Number of trials per candidate evaluation

temperature: f32

Temperature for LLM-based mutations

track_stats: bool

Track detailed statistics

track_best_outputs: bool

Track best outputs on validation set (for inference-time search)

max_rollouts: Option<usize>

Maximum total rollouts (budget control)

max_lm_calls: Option<usize>

Maximum LM calls (budget control)

prompt_model: Option<LM>

Optional separate LM for meta-prompting (instruction generation)

valset: Option<Vec<Example>>

Validation set for Pareto evaluation (if None, uses trainset)

Implementations

impl GEPA

pub fn builder() -> GEPABuilder

Create an instance of GEPA using the builder syntax

Examples found in repository

examples/09-gepa-sentiment.rs (line 179)

async fn main() -> Result<()> {
    println!("GEPA Sentiment Analysis Optimization Example\n");

    // Setup LM
    let lm = LM::builder().temperature(0.7).build().await.unwrap();

    configure(lm.clone(), ChatAdapter);

    // Create training examples with diverse sentiments
    let trainset = vec![
        example! {
            "text": "input" => "This movie was absolutely fantastic! I loved every minute of it.",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "Terrible service, will never come back again.",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "The weather is okay, nothing special.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "Despite some minor issues, I'm quite happy with the purchase.",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "I have mixed feelings about this product.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "This is the worst experience I've ever had!",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "It's fine. Does what it's supposed to do.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "Exceeded all my expectations! Highly recommend!",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "Disappointed and frustrated with the outcome.",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "Standard quality, nothing remarkable.",
            "expected_sentiment": "input" => "neutral"
        },
    ];

    // Create module
    let mut module = SentimentAnalyzer::builder()
        .predictor(Predict::new(SentimentSignature::new()))
        .build();

    // Evaluate baseline performance
    println!("Baseline Performance:");
    let baseline_score = module.evaluate(trainset.clone()).await;
    println!("  Average score: {:.3}\n", baseline_score);

    // Configure GEPA optimizer
    let gepa = GEPA::builder()
        .num_iterations(5)
        .minibatch_size(5)
        .num_trials(3)
        .temperature(0.9)
        .track_stats(true)
        .build();

    // Run optimization
    println!("Starting GEPA optimization...\n");
    let result = gepa
        .compile_with_feedback(&mut module, trainset.clone())
        .await?;

    // Display results
    println!("\nOptimization Results:");
    println!(
        "  Best average score: {:.3}",
        result.best_candidate.average_score()
    );
    println!("  Total rollouts: {}", result.total_rollouts);
    println!("  Total LM calls: {}", result.total_lm_calls);
    println!("  Generations: {}", result.evolution_history.len());

    println!("\nBest Instruction:");
    println!("  {}", result.best_candidate.instruction);

    if !result.evolution_history.is_empty() {
        println!("\nEvolution History:");
        for entry in &result.evolution_history {
            println!("  Generation {}: {:.3}", entry.0, entry.1);
        }
    }

    // Test optimized module on a new example
    println!("\nTesting Optimized Module:");
    let test_example = example! {
        "text": "input" => "This product changed my life! Absolutely amazing!",
        "expected_sentiment": "input" => "positive"
    };

    let test_prediction = module.forward(test_example.clone()).await?;
    let test_feedback = module
        .feedback_metric(&test_example, &test_prediction)
        .await;

    println!(
        "  Test prediction: {}",
        test_prediction.get("sentiment", None)
    );
    println!("  Test score: {:.3}", test_feedback.score);
    println!("  Feedback:\n{}", test_feedback.feedback);

    Ok(())
}

examples/10-gepa-llm-judge.rs (line 274)

async fn main() -> Result<()> {
    println!("GEPA with LLM-as-a-Judge Example\n");
    println!("This example shows how to use an LLM judge to automatically");
    println!("generate rich feedback for optimizing a math solver.\n");

    // Setup: Configure the LLM
    // Main LM for the task
    let task_lm = LM::builder().temperature(0.7).build().await.unwrap();

    // Judge LM (could use a different/cheaper model)
    let judge_lm = LM::builder().temperature(0.3).build().await.unwrap();

    configure(task_lm, ChatAdapter);

    // Create training examples
    let trainset = vec![
        example! {
            "problem": "input" => "Sarah has 12 apples. She gives 3 to her friend and buys 5 more. How many apples does she have now?",
            "expected_answer": "input" => "14"
        },
        example! {
            "problem": "input" => "A train travels 60 miles in 1 hour. How far will it travel in 3.5 hours at the same speed?",
            "expected_answer": "input" => "210"
        },
        example! {
            "problem": "input" => "There are 24 students in a class. If 1/3 of them are absent, how many students are present?",
            "expected_answer": "input" => "16"
        },
        example! {
            "problem": "input" => "A rectangle has length 8 cm and width 5 cm. What is its area?",
            "expected_answer": "input" => "40"
        },
        example! {
            "problem": "input" => "John has $50. He spends $12 on lunch and $8 on a book. How much money does he have left?",
            "expected_answer": "input" => "30"
        },
    ];

    // Create the module
    let mut module = MathSolver::builder()
        .solver(Predict::new(MathWordProblem::new()))
        .judge(Predict::new(MathJudge::new()))
        .judge_lm(Arc::new(judge_lm))
        .build();

    // Evaluate baseline performance
    println!("Step 1: Baseline Performance");
    println!("Testing the solver before optimization...\n");
    let baseline_score = module.evaluate(trainset.clone()).await;
    println!("  Baseline average score: {:.3}\n", baseline_score);

    // Configure GEPA optimizer
    println!("Step 2: Configure GEPA");
    println!("Setting up the optimizer with budget controls...\n");

    let gepa = GEPA::builder()
        .num_iterations(3) // Fewer iterations for demo
        .minibatch_size(3) // Smaller batches
        .temperature(0.9)
        .track_stats(true)
        .maybe_max_lm_calls(Some(100)) // Important: we're using 2x LM calls (task + judge)
        .build();

    // Run GEPA optimization
    println!("Step 3: Run GEPA Optimization");
    println!("The judge will analyze reasoning quality and provide feedback...\n");

    let result = gepa
        .compile_with_feedback(&mut module, trainset.clone())
        .await?;

    // Display results
    println!("\nStep 4: Results");
    println!("===============\n");
    println!("Optimization complete!");
    println!(
        "  Best average score: {:.3}",
        result.best_candidate.average_score()
    );
    println!(
        "  Improvement: {:.3}",
        result.best_candidate.average_score() - baseline_score
    );
    println!("  Total rollouts: {}", result.total_rollouts);
    println!(
        "  Total LM calls: {} (includes judge evaluations)",
        result.total_lm_calls
    );

    println!("\nEvolution over time:");
    for (generation, score) in &result.evolution_history {
        println!("  Generation {}: {:.3}", generation, score);
    }

    println!("\nOptimized instruction:");
    println!("  {}", result.best_candidate.instruction);

    // Test the optimized solver
    println!("\nStep 5: Test Optimized Solver");
    println!("==============================\n");

    let test_problem = example! {
        "problem": "input" => "A store sells pencils for $0.25 each. If you buy 8 pencils, how much will you pay?",
        "expected_answer": "input" => "2"
    };

    let test_prediction = module.forward(test_problem.clone()).await?;
    let test_feedback = module
        .feedback_metric(&test_problem, &test_prediction)
        .await;

    println!(
        "Test problem: A store sells pencils for $0.25 each. If you buy 8 pencils, how much will you pay?"
    );
    println!("\nAnswer: {}", test_prediction.get("answer", None));
    println!("Score: {:.3}\n", test_feedback.score);
    println!("Detailed Feedback from Judge:");
    println!("{}", test_feedback.feedback);

    Ok(())
}

impl GEPA

pub async fn compile_with_feedback<M>( &self, module: &mut M, trainset: Vec<Example>, ) -> Result<GEPAResult>

where M: Module + Optimizable + FeedbackEvaluator,

Compile method specifically for FeedbackEvaluator modules

Examples found in repository

examples/09-gepa-sentiment.rs (line 190)

async fn main() -> Result<()> {
    println!("GEPA Sentiment Analysis Optimization Example\n");

    // Setup LM
    let lm = LM::builder().temperature(0.7).build().await.unwrap();

    configure(lm.clone(), ChatAdapter);

    // Create training examples with diverse sentiments
    let trainset = vec![
        example! {
            "text": "input" => "This movie was absolutely fantastic! I loved every minute of it.",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "Terrible service, will never come back again.",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "The weather is okay, nothing special.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "Despite some minor issues, I'm quite happy with the purchase.",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "I have mixed feelings about this product.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "This is the worst experience I've ever had!",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "It's fine. Does what it's supposed to do.",
            "expected_sentiment": "input" => "neutral"
        },
        example! {
            "text": "input" => "Exceeded all my expectations! Highly recommend!",
            "expected_sentiment": "input" => "positive"
        },
        example! {
            "text": "input" => "Disappointed and frustrated with the outcome.",
            "expected_sentiment": "input" => "negative"
        },
        example! {
            "text": "input" => "Standard quality, nothing remarkable.",
            "expected_sentiment": "input" => "neutral"
        },
    ];

    // Create module
    let mut module = SentimentAnalyzer::builder()
        .predictor(Predict::new(SentimentSignature::new()))
        .build();

    // Evaluate baseline performance
    println!("Baseline Performance:");
    let baseline_score = module.evaluate(trainset.clone()).await;
    println!("  Average score: {:.3}\n", baseline_score);

    // Configure GEPA optimizer
    let gepa = GEPA::builder()
        .num_iterations(5)
        .minibatch_size(5)
        .num_trials(3)
        .temperature(0.9)
        .track_stats(true)
        .build();

    // Run optimization
    println!("Starting GEPA optimization...\n");
    let result = gepa
        .compile_with_feedback(&mut module, trainset.clone())
        .await?;

    // Display results
    println!("\nOptimization Results:");
    println!(
        "  Best average score: {:.3}",
        result.best_candidate.average_score()
    );
    println!("  Total rollouts: {}", result.total_rollouts);
    println!("  Total LM calls: {}", result.total_lm_calls);
    println!("  Generations: {}", result.evolution_history.len());

    println!("\nBest Instruction:");
    println!("  {}", result.best_candidate.instruction);

    if !result.evolution_history.is_empty() {
        println!("\nEvolution History:");
        for entry in &result.evolution_history {
            println!("  Generation {}: {:.3}", entry.0, entry.1);
        }
    }

    // Test optimized module on a new example
    println!("\nTesting Optimized Module:");
    let test_example = example! {
        "text": "input" => "This product changed my life! Absolutely amazing!",
        "expected_sentiment": "input" => "positive"
    };

    let test_prediction = module.forward(test_example.clone()).await?;
    let test_feedback = module
        .feedback_metric(&test_example, &test_prediction)
        .await;

    println!(
        "  Test prediction: {}",
        test_prediction.get("sentiment", None)
    );
    println!("  Test score: {:.3}", test_feedback.score);
    println!("  Feedback:\n{}", test_feedback.feedback);

    Ok(())
}

examples/10-gepa-llm-judge.rs (line 287)

async fn main() -> Result<()> {
    println!("GEPA with LLM-as-a-Judge Example\n");
    println!("This example shows how to use an LLM judge to automatically");
    println!("generate rich feedback for optimizing a math solver.\n");

    // Setup: Configure the LLM
    // Main LM for the task
    let task_lm = LM::builder().temperature(0.7).build().await.unwrap();

    // Judge LM (could use a different/cheaper model)
    let judge_lm = LM::builder().temperature(0.3).build().await.unwrap();

    configure(task_lm, ChatAdapter);

    // Create training examples
    let trainset = vec![
        example! {
            "problem": "input" => "Sarah has 12 apples. She gives 3 to her friend and buys 5 more. How many apples does she have now?",
            "expected_answer": "input" => "14"
        },
        example! {
            "problem": "input" => "A train travels 60 miles in 1 hour. How far will it travel in 3.5 hours at the same speed?",
            "expected_answer": "input" => "210"
        },
        example! {
            "problem": "input" => "There are 24 students in a class. If 1/3 of them are absent, how many students are present?",
            "expected_answer": "input" => "16"
        },
        example! {
            "problem": "input" => "A rectangle has length 8 cm and width 5 cm. What is its area?",
            "expected_answer": "input" => "40"
        },
        example! {
            "problem": "input" => "John has $50. He spends $12 on lunch and $8 on a book. How much money does he have left?",
            "expected_answer": "input" => "30"
        },
    ];

    // Create the module
    let mut module = MathSolver::builder()
        .solver(Predict::new(MathWordProblem::new()))
        .judge(Predict::new(MathJudge::new()))
        .judge_lm(Arc::new(judge_lm))
        .build();

    // Evaluate baseline performance
    println!("Step 1: Baseline Performance");
    println!("Testing the solver before optimization...\n");
    let baseline_score = module.evaluate(trainset.clone()).await;
    println!("  Baseline average score: {:.3}\n", baseline_score);

    // Configure GEPA optimizer
    println!("Step 2: Configure GEPA");
    println!("Setting up the optimizer with budget controls...\n");

    let gepa = GEPA::builder()
        .num_iterations(3) // Fewer iterations for demo
        .minibatch_size(3) // Smaller batches
        .temperature(0.9)
        .track_stats(true)
        .maybe_max_lm_calls(Some(100)) // Important: we're using 2x LM calls (task + judge)
        .build();

    // Run GEPA optimization
    println!("Step 3: Run GEPA Optimization");
    println!("The judge will analyze reasoning quality and provide feedback...\n");

    let result = gepa
        .compile_with_feedback(&mut module, trainset.clone())
        .await?;

    // Display results
    println!("\nStep 4: Results");
    println!("===============\n");
    println!("Optimization complete!");
    println!(
        "  Best average score: {:.3}",
        result.best_candidate.average_score()
    );
    println!(
        "  Improvement: {:.3}",
        result.best_candidate.average_score() - baseline_score
    );
    println!("  Total rollouts: {}", result.total_rollouts);
    println!(
        "  Total LM calls: {} (includes judge evaluations)",
        result.total_lm_calls
    );

    println!("\nEvolution over time:");
    for (generation, score) in &result.evolution_history {
        println!("  Generation {}: {:.3}", generation, score);
    }

    println!("\nOptimized instruction:");
    println!("  {}", result.best_candidate.instruction);

    // Test the optimized solver
    println!("\nStep 5: Test Optimized Solver");
    println!("==============================\n");

    let test_problem = example! {
        "problem": "input" => "A store sells pencils for $0.25 each. If you buy 8 pencils, how much will you pay?",
        "expected_answer": "input" => "2"
    };

    let test_prediction = module.forward(test_problem.clone()).await?;
    let test_feedback = module
        .feedback_metric(&test_problem, &test_prediction)
        .await;

    println!(
        "Test problem: A store sells pencils for $0.25 each. If you buy 8 pencils, how much will you pay?"
    );
    println!("\nAnswer: {}", test_prediction.get("answer", None));
    println!("Score: {:.3}\n", test_feedback.score);
    println!("Detailed Feedback from Judge:");
    println!("{}", test_feedback.feedback);

    Ok(())
}

Trait Implementations

impl Optimizer for GEPA

async fn compile<M>( &self, _module: &mut M, _trainset: Vec<Example>, ) -> Result<()>

where M: Module + Optimizable + Evaluator,