Add more local mutation

v1.9.5

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -1,2 +1,6 @@
-cache/
-out/
+onchain/cache/
+onchain/out/
+
+offchain/target/
+
+.direnv

.gitmodules

@@ -1,3 +1,4 @@
-[submodule "lib/forge-std"]
-	path = lib/forge-std
+
+[submodule "onchain/lib/forge-std"]
+	path = onchain/lib/forge-std
 	url = https://github.com/foundry-rs/forge-std

flake.nix

@@ -23,6 +23,9 @@
 
             # ... any other dependencies we need
             solc
+            cargo
+            rustc
+            rust-analyzer
           ];
 
           # Decorative prompt override so we know when we're in a dev shell

offchain/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "offchain"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "gp_tester"
+path = "src/bin/gp_tester.rs"
+
+[[bin]]
+name = "gp_spec_tester"
+path = "src/bin/gp_spec_tester.rs"
+
+[[bin]]
+name = "symreg_experiment"
+path = "src/bin/symreg_experiment.rs"
+
+[[bin]]
+name = "symreg_experiment_local"
+path = "src/bin/symreg_experiment_local.rs"
+
+[dependencies]
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+rand = "0.8"
+hex = "0.4"
+# ethers = { version = "2.0", features = ["abi"] }
+anyhow = "1.0"
+revm = { git = "https://github.com/bluealloy/revm.git", rev = "03ea24bd9550e93b08f343e0b410725557c1adb4", features = ["std"] }
+database = { git = "https://github.com/bluealloy/revm.git", rev = "03ea24bd9550e93b08f343e0b410725557c1adb4", package = "revm-database" }
+ethers = "2.0"
+
+
+

offchain/src/bin/gp_spec_tester.rs

@@ -0,0 +1,36 @@
+use anyhow::Result;
+use rand::thread_rng;
+use rand::Rng;
+
+// Suppose you have these in your library:
+use offchain::gp::generate_spec::ranmdom_code_fixed;
+use offchain::gp::mutation::mutate_by_index;
+use offchain::compiler::ast::UntypedAst;
+
+fn main() -> Result<()> {
+    let mut rng = thread_rng();
+
+    // We'll produce, say, 3 random ASTs ("subjects").
+    let num_subjects = 3;
+    let max_points = 6;
+
+    for i in 0..num_subjects {
+        // Generate a random AST
+        let original = ranmdom_code_fixed(&mut rng, max_points);
+        println!("=== Subject #{} ===", i);
+        println!("Original AST:\n{:#?}", original);
+
+        // Let's do 2 successive mutations on it
+        let mut prev = original.clone();
+        for mut_idx in 0..2 {
+            let mutated = mutate_by_index(&prev, &mut rng, max_points);
+            println!("Mutation #{} result:\n{:#?}", mut_idx, mutated);
+            prev = mutated; // so the next iteration mutates from the last result
+        }
+
+        println!("=== End of Subject #{} ===\n", i);
+    }
+
+    println!("Done generating & mutating random ASTs!");
+    Ok(())
+}

offchain/src/bin/gp_tester.rs

@@ -0,0 +1,91 @@
+// src/bin/gp_tester.rs
+
+use anyhow::{anyhow, bail, Result};
+use rand::{thread_rng, Rng};
+
+// 1) We'll use the helper that reads creation code from a JSON artifact
+use offchain::helpers::artifact::get_creation_code;
+
+// 2) EvmRunner to deploy & run the interpreter
+use offchain::runner::revm_runner::EvmRunner;
+
+// 3) AST generation & mutation
+use offchain::gp::generate::random_ast;
+use offchain::gp::genetic_ops::mutated_ast;
+use offchain::compiler::ast::UntypedAst;
+
+fn main() -> Result<()> {
+    // ----------------------------------------------------------------------
+    // 1) Read the creation code (Push3Interpreter) using our helper function
+    // ----------------------------------------------------------------------
+    let creation_hex_filename = "../onchain/out/Push3Interpreter.sol/Push3Interpreter.json";
+    let creation_bytes = get_creation_code(creation_hex_filename)?;
+    println!(
+        "Loaded creation code from {} ({} bytes)",
+        creation_hex_filename,
+        creation_bytes.len()
+    );
+
+    // 2) Create the ephemeral EVM (deploy the contract)
+    let mut runner = EvmRunner::new(creation_bytes)?;
+    println!("Deployed test interpreter at: 0x{:x}\n", runner.interpreter_addr);
+
+    // 3) We'll generate random ASTs & mutate them
+    let number_of_programs = 3; // how many random ASTs to try
+    let max_depth = 4;         // max AST depth
+    let mut rng = thread_rng();
+
+    for i in 0..number_of_programs {
+        // a) Generate a random AST
+        let ast: UntypedAst = random_ast(&mut rng, 0, max_depth);
+
+        println!("=== Program {} ===", i);
+        println!("Random AST:\n{:#?}", ast);
+
+        // b) Run the original AST
+        match runner.run_ast(&ast) {
+            Ok(outputs) => {
+                println!("Original AST ran successfully!");
+                println!("Final CODE stack: {:?}", outputs.final_code_stack);
+                println!("Final EXEC stack: {:?}", outputs.final_exec_stack);
+                println!("Final INT stack:  {:?}", outputs.final_int_stack);
+
+                // c) Mutate it a few times
+                let mutated1 = mutated_ast(&ast, &mut rng, 0, max_depth);
+                println!("\n-- MUTATED 1 --\n{:#?}", mutated1);
+
+                match runner.run_ast(&mutated1) {
+                    Ok(m1_out) => {
+                        println!("MUTATED 1 ran successfully!");
+                        println!("Final INT stack: {:?}", m1_out.final_int_stack);
+                    }
+                    Err(e) => {
+                        println!("MUTATED 1 error: {}", e);
+                    }
+                }
+
+                let mutated2 = mutated_ast(&ast, &mut rng, 0, max_depth);
+                println!("\n-- MUTATED 2 --\n{:#?}", mutated2);
+
+                match runner.run_ast(&mutated2) {
+                    Ok(m2_out) => {
+                        println!("MUTATED 2 ran successfully!");
+                        println!("Final INT stack: {:?}", m2_out.final_int_stack);
+                    }
+                    Err(e) => {
+                        println!("MUTATED 2 error: {}", e);
+                    }
+                }
+            }
+            Err(e) => {
+                // If the original fails, we won't bother mutating it
+                println!("Original AST error: {}", e);
+            }
+        }
+
+        println!("=== End of Program {} ===\n", i);
+    }
+
+    println!("Finished running & mutating {} random programs.", number_of_programs);
+    Ok(())
+}

offchain/src/bin/symreg_experiment.rs

@@ -0,0 +1,223 @@
+// src/bin/symreg_experiment.rs
+
+use anyhow::Result;
+use rand::{thread_rng, Rng};
+
+// Our GP + compiler modules (adjust paths as needed)
+use offchain::compiler::ast::{UntypedAst, Push3Ast};
+use offchain::helpers::artifact::get_creation_code;
+use offchain::runner::revm_runner::{
+    EvmRunner, 
+    Push3InterpreterInputs,
+};
+use offchain::compiler::push3_describtor::make_sublist_descriptor;
+
+// Our GP operators
+use offchain::gp::generate_spec::ranmdom_code_fixed;
+use offchain::gp::mutation::{mutate_by_index, crossover_by_index};
+
+// Ethers + ABI
+use ethers::types::U256;
+use ethers::abi::{encode, Token};
+
+/// 1) Generate (x, y) samples for f(x)=3x^2 + x + 3
+fn generate_samples() -> Vec<(i32, i32)> {
+    let mut samples = Vec::new();
+    for x in -5..=5 {
+        let y = 3 * x * x + x + 3;
+        samples.push((x, y));
+    }
+    samples
+}
+
+/// 2) Evaluate a single AST on a single input `x` by 
+/// pushing `x` onto the int stack, running in EVM, 
+/// and reading the final top of the int stack.
+fn evaluate_ast_on_x(
+    runner: &mut EvmRunner,
+    ast: &UntypedAst,
+    x: i32,
+) -> i32 {
+    // a) Convert AST => push3 bytecode
+    let code_bytes = ast.to_bytecode();
+    let code_len = code_bytes.len() as u32;
+
+    // b) Build a sublist descriptor
+    let descriptor = make_sublist_descriptor(0, code_len);
+
+    // c) Provide x in `init_int_stack`
+    let inputs = Push3InterpreterInputs {
+        code: code_bytes,
+        init_code_stack: Vec::new(),
+        init_exec_stack: vec![descriptor],
+        init_int_stack: vec![x as i128],
+    };
+
+    // d) Actually run the interpreter
+    let outputs = match runner.run_interpreter(&inputs) {
+        Ok(o) => o,
+        Err(_) => {
+            // If the call fails or reverts, return 0
+            return 0;
+        }
+    };
+
+    // e) If final_int_stack is empty => 0, else top item
+    if outputs.final_int_stack.is_empty() {
+        i32::MAX
+    } else {
+        *outputs.final_int_stack.last().unwrap() as i32
+    }
+}
+
+/// 3) Evaluate an AST on all (x, y) samples => compute MSE
+fn evaluate_fitness(
+    runner: &mut EvmRunner,
+    ast: &UntypedAst,
+    samples: &[(i32, i32)]
+) -> f64 {
+    let mut error_sum = 0.0;
+    for &(x, target_y32) in samples {
+        // cast to i64
+        let target_y = target_y32 as i64;
+        
+        // evaluate in i64 as well
+        let predicted_i64 = evaluate_ast_on_x(runner, ast, x) as i64;
+        
+        let diff = predicted_i64.wrapping_sub(target_y); 
+        // or you could saturating_sub if you prefer
+
+        error_sum += (diff as f64) * (diff as f64);
+    }
+    error_sum / samples.len() as f64
+}
+
+
+fn main() -> Result<()> {
+    // 1) Generate samples for f(x)=3x^2 + x + 3
+    let samples = generate_samples();
+
+    // 2) Create ephemeral EVM runner for the interpreter
+    let creation_hex_filename = "../onchain/out/Push3Interpreter.sol/Push3Interpreter.json";
+    let creation_bytes = get_creation_code(creation_hex_filename)?;
+    let mut runner = EvmRunner::new(creation_bytes)?;
+
+    // 3) GP parameters
+    let pop_size = 4000;  // must be divisible by 4 for our scheme
+    let generations = 100;
+    let early_stop_threshold = 1.0;
+    let max_points = 20;
+
+    assert_eq!(pop_size % 4, 0, "pop_size must be multiple of 4 for our scheme");
+    let quarter = pop_size / 4;
+
+    let mut rng = thread_rng();
+
+    // 4) Initialize population (random)
+    let mut population: Vec<UntypedAst> = (0..pop_size)
+        .map(|_| ranmdom_code_fixed(&mut rng, max_points))
+        .collect();
+
+    // 5) Main GP loop
+    for gen in 0..generations {
+        // (a) Evaluate
+        let mut scored: Vec<(UntypedAst, f64)> = population.into_iter()
+            .map(|ast| {
+                let err = evaluate_fitness(&mut runner, &ast, &samples);
+                (ast, err)
+            })
+            .collect();
+
+        // (b) Sort ascending by error
+        scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
+
+        // (c) Print generation summary
+        let best_err = scored[0].1;
+        println!("\n=== Generation {gen} ===");
+        println!("Best error = {best_err}");
+
+        // Print top 5 subjects in pretty format
+        // let top_n = 5.min(scored.len());
+        // println!("Top {top_n} subjects:");
+        // for i in 0..top_n {
+        //     println!(
+        //         "  #{i}, err={}, AST:\n{:#?}",
+        //         scored[i].1,
+        //         scored[i].0
+        //     );
+        // }
+
+        // early stop?
+        if best_err < early_stop_threshold {
+            println!("Best error < {early_stop_threshold}, stopping early!");
+            // we can keep 'scored' for final if we want
+            population = scored.into_iter().map(|(a, _)| a).collect();
+            break;
+        }
+
+        // (d) Reproduction => build new population
+        let mut new_pop = Vec::with_capacity(pop_size);
+
+        // keep best quarter
+        for i in 0..quarter {
+            new_pop.push(scored[i].0.clone());
+        }
+
+        // add random quarter
+        for _ in 0..quarter {
+            let fresh = ranmdom_code_fixed(&mut rng, max_points);
+            new_pop.push(fresh);
+        }
+
+        // crossover quarter
+        let top_half_count = scored.len() / 2;
+        let crossover_pairs = quarter / 2;  // each yields 2 kids => quarter total
+        for _ in 0..crossover_pairs {
+            let idx1 = rng.gen_range(0..top_half_count);
+            let idx2 = rng.gen_range(0..top_half_count);
+            let (child1, child2) = crossover_by_index(
+                &scored[idx1].0,
+                &scored[idx2].0,
+                &mut rng
+            );
+            new_pop.push(child1);
+            new_pop.push(child2);
+        }
+
+        // mutate quarter
+        while new_pop.len() < pop_size {
+            let idx = rng.gen_range(0..top_half_count);
+            let mutated = mutate_by_index(&scored[idx].0, &mut rng, max_points);
+            new_pop.push(mutated);
+        }
+
+        population = new_pop;
+    }
+
+    // 6) Final population => evaluate & sort, then print only top 10
+    println!("\n=== Final Population (Top 10) ===");
+
+    // a) Evaluate each item in the final population
+    let mut final_scored: Vec<(UntypedAst, f64)> = population
+        .into_iter()
+        .map(|ast| {
+            let err = evaluate_fitness(&mut runner, &ast, &samples);
+            (ast, err)
+        })
+        .collect();
+    
+    // b) Sort ascending by error
+    final_scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
+    
+    // c) Print the top 10 (or fewer if the population is smaller)
+    let top_n = 10.min(final_scored.len());
+    for i in 0..top_n {
+        let (ref ast, err) = final_scored[i];
+        println!(
+            "Subject #{i}, err={err}, AST:\n{:#?}",
+            ast
+        );
+    }
+    
+    Ok(())
+}

offchain/src/bin/symreg_experiment_local.rs

@@ -0,0 +1,202 @@
+// src/bin/symreg_experiment_local.rs
+
+use anyhow::Result;
+use rand::{thread_rng, Rng};
+
+// Our GP + compiler modules (adjust paths if needed)
+use offchain::compiler::ast::{UntypedAst, Push3Ast};
+use offchain::helpers::artifact::get_creation_code;
+use offchain::runner::revm_runner::{EvmRunner, Push3InterpreterInputs};
+use offchain::compiler::push3_describtor::make_sublist_descriptor;
+
+// Our random code and local mutation
+use offchain::gp::generate_spec::ranmdom_code_fixed;
+use offchain::gp::local_mutation::local_mutation_fixed;
+
+// Ethers + ABI
+use ethers::types::U256;
+use ethers::abi::{encode, Token};
+
+/// 1) Generate (x, y) samples for f(x) = 3x^2 + x + 3
+fn generate_samples() -> Vec<(i32, i32)> {
+    let mut samples = Vec::new();
+    for x in -5..=5 {
+        let y = 3 * x * x + x + 3;
+        samples.push((x, y));
+    }
+    samples
+}
+
+/// 2) Evaluate a single AST on a single input `x`, returning the final top of the int stack.
+fn evaluate_ast_on_x(
+    runner: &mut EvmRunner,
+    ast: &UntypedAst,
+    x: i32,
+) -> i32 {
+    // Convert AST => push3 bytecode
+    let code_bytes = ast.to_bytecode();
+    let code_len = code_bytes.len() as u32;
+
+    // Build a sublist descriptor
+    let descriptor = make_sublist_descriptor(0, code_len);
+
+    // Provide x in `init_int_stack`
+    let inputs = Push3InterpreterInputs {
+        code: code_bytes,
+        init_code_stack: Vec::new(),
+        init_exec_stack: vec![descriptor],
+        init_int_stack: vec![x as i128],
+    };
+
+    // Run
+    let outputs = match runner.run_interpreter(&inputs) {
+        Ok(o) => o,
+        Err(_) => {
+            // If revert => 0
+            return 0;
+        }
+    };
+
+    if outputs.final_int_stack.is_empty() {
+        i32::MAX  // or 0, or i32::MAX to strongly penalize weird runs
+    } else {
+        *outputs.final_int_stack.last().unwrap() as i32
+    }
+}
+
+/// 3) Evaluate an AST on all samples => compute MSE
+fn evaluate_fitness(
+    runner: &mut EvmRunner,
+    ast: &UntypedAst,
+    samples: &[(i32, i32)]
+) -> f64 {
+    let mut error_sum = 0.0;
+    for &(x, target_y32) in samples {
+        // cast to i64
+        let target_y = target_y32 as i64;
+        
+        // evaluate in i64
+        let predicted_i64 = evaluate_ast_on_x(runner, ast, x) as i64;
+        
+        // wrapping_sub to avoid panic
+        let diff = predicted_i64.wrapping_sub(target_y);
+        error_sum += (diff as f64) * (diff as f64);
+    }
+    error_sum / samples.len() as f64
+}
+
+fn main() -> Result<()> {
+    // 1) Generate samples
+    let samples = generate_samples();
+
+    // 2) Setup ephemeral EVM runner
+    let creation_hex_filename = "../onchain/out/Push3Interpreter.sol/Push3Interpreter.json";
+    let creation_bytes = get_creation_code(creation_hex_filename)?;
+    let mut runner = EvmRunner::new(creation_bytes)?;
+
+    // 3) GP parameters
+    let pop_size = 3600;  // must be multiple of 3 for our scheme
+    let generations = 100;
+    let early_stop_threshold = 1.0;
+    let max_points = 12;  // random code size limit
+
+    // Ensure pop_size is multiple of 3
+    assert_eq!(pop_size % 3, 0, "pop_size must be multiple of 3 for our scheme");
+    let third = pop_size / 3;
+
+    let mut rng = thread_rng();
+
+    // 4) Initialize random population
+    let mut population: Vec<UntypedAst> = (0..pop_size)
+        .map(|_| ranmdom_code_fixed(&mut rng, max_points))
+        .collect();
+
+    // 5) Main loop
+    for gen in 0..generations {
+        // a) Evaluate
+        let mut scored: Vec<(UntypedAst, f64)> = population.into_iter()
+            .map(|ast| {
+                let err = evaluate_fitness(&mut runner, &ast, &samples);
+                (ast, err)
+            })
+            .collect();
+        
+        // b) Sort ascending by error
+        scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
+
+        let best_err = scored[0].1;
+        println!("\n=== Generation {gen} ===");
+        println!("Best error = {best_err}");
+
+        // (Optionally) Print top 5 in pretty format
+        let top_n = 5.min(scored.len());
+        println!("Top {top_n} subjects:");
+        for i in 0..top_n {
+            println!(
+                "  #{i}, err={}, AST:\n{:#?}",
+                scored[i].1, 
+                scored[i].0
+            );
+        }
+
+        // check early stop
+        if best_err < early_stop_threshold {
+            println!("Best error < {early_stop_threshold}, stopping early!");
+            population = scored.into_iter().map(|(a, _)| a).collect();
+            break;
+        }
+
+        // c) Build new population:
+        //   - 1/3 = best survivors
+        //   - 1/3 = fresh random
+        //   - 1/3 = local mutation
+        let mut new_pop = Vec::with_capacity(pop_size);
+
+        // keep best third
+        for i in 0..third {
+            new_pop.push(scored[i].0.clone());
+        }
+
+        // random third
+        for _ in 0..third {
+            let fresh = ranmdom_code_fixed(&mut rng, max_points);
+            new_pop.push(fresh);
+        }
+
+        // local mutation third
+        let top_half_count = scored.len() / 2; 
+        // we'll pick parents from top half for local mutation
+        while new_pop.len() < pop_size {
+            let idx = rng.gen_range(0..top_half_count);
+            // we assume you have local_mutation_fixed
+            // if you prefer passing a custom InstructionSet, do local_mutation(..., &instr_set)
+            let mutated = offchain::gp::local_mutation::local_mutation_fixed(
+                &scored[idx].0,
+                &mut rng
+            );
+            new_pop.push(mutated);
+        }
+
+        // store for next generation
+        population = new_pop;
+    }
+
+    // 6) Final => evaluate & sort => top 10
+    println!("\n=== Final Population (Top 10) ===");
+    let mut final_scored: Vec<(UntypedAst, f64)> = population
+        .into_iter()
+        .map(|ast| {
+            let err = evaluate_fitness(&mut runner, &ast, &samples);
+            (ast, err)
+        })
+        .collect();
+    final_scored.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
+
+    let top_n = 10.min(final_scored.len());
+    for i in 0..top_n {
+        let (ref ast, err) = final_scored[i];
+        println!("Subject #{i}, err={err}, AST:\n{:#?}", ast);
+    }
+
+    Ok(())
+}

offchain/src/compiler/ast.rs

@@ -0,0 +1,273 @@
+//! src/compiler/ast.rs
+//! 
+//! This module defines an **abstract** untyped AST for our Push3-like language,
+//! plus a mapping for how to encode opcodes as bytes. We do *not* hardcode numeric
+//! values in the `OpCode` enum. Instead, we provide a trait that can map
+//! opcodes to bytes. This allows us to expand or change instructions easily
+//! (e.g., when the on-chain interpreter adds new opcodes or changes their IDs).
+
+/// A trait describing how to convert an AST into Push3 bytecode.
+///
+/// This is deliberately minimal for now. In the future, we could add more methods
+/// (like parsing from bytecode or AST mutation).
+pub trait Push3Ast {
+    /// Convert this AST into a bytecode vector that the on-chain interpreter
+    /// can parse and execute.
+    fn to_bytecode(&self) -> Vec<u8>;
+}
+
+/// A trait that **maps** each [`OpCode`] variant to its **single-byte** representation.
+///
+/// By centralizing this, we can easily add or reorder instructions without rewriting
+/// big chunks of code everywhere. For example, if we add `OpCode::MyNewOp`, we just
+/// update this trait’s logic.
+pub trait OpCodeMapping {
+    /// Given an `OpCode` enum variant, return the corresponding single `u8`
+    /// that the interpreter expects.
+    fn opcode_byte(&self, op: &OpCode) -> u8;
+
+    // If you need reverse-lookup (byte => OpCode), you could add a method like:
+    // fn from_byte(&self, b: u8) -> Option<OpCode>;
+    // for now, we omit it since we only do forward mapping in this file.
+}
+
+/// Our untyped AST node:
+/// - `IntLiteral(i32)` holds a literal integer,
+/// - `Instruction(OpCode)` holds one opcode,
+/// - `Sublist(Vec<UntypedAst>)` holds a collection of nested AST nodes.
+#[derive(Debug, Clone, PartialEq)]
+pub enum UntypedAst {
+    IntLiteral(i32),
+    Instruction(OpCode),
+    Sublist(Vec<UntypedAst>),
+}
+
+/// An **abstract** set of opcodes. We do *not* assign numeric values here.
+/// Instead, see [`OpCodeMapping::opcode_byte`] for how we convert them to bytes.
+#[derive(Debug, Clone, PartialEq)]
+pub enum OpCode {
+    Noop,
+    Plus,
+    Minus,
+    Mult,
+    Dup,
+    Pop,
+    // Add new instructions here as needed. E.g.:
+    // MyNewOp, etc.
+}
+
+impl UntypedAst {
+    /// Encode this AST into bytecode, using a provided [`OpCodeMapping`].
+    ///
+    /// This method is more flexible than `to_bytecode()`, because you can pass in
+    /// *any* mapping if needed. The method used by the trait’s `to_bytecode()`
+    /// relies on the global `DEFAULT_OP_MAPPING`.
+    pub fn to_bytecode_with_mapping<M: OpCodeMapping>(&self, mapping: &M) -> Vec<u8> {
+        match self {
+            // For an integer literal, we write the “tag byte” for int-literal, then 4 bytes (LE).
+            UntypedAst::IntLiteral(val) => {
+                // Hardcode 0x02 => INT_LITERAL. 
+                // You *could* put that in the mapping if you want to make that flexible, too.
+                let mut bytes = Vec::with_capacity(1 + 4);
+                bytes.push(0x02);
+                bytes.extend_from_slice(&val.to_be_bytes());
+                bytes
+            }
+            UntypedAst::Instruction(op) => {
+                // Use the mapping to find the correct opcode byte:
+                let b = mapping.opcode_byte(op);
+                vec![b]
+            }
+            UntypedAst::Sublist(children) => {
+                // Hardcode 0x03 => SUBLIST, then big-endian length, then child payload
+                let mut payload = Vec::new();
+                for child in children {
+                    let child_bytes = child.to_bytecode_with_mapping(mapping);
+                    payload.extend(child_bytes);
+                }
+                let sub_len = payload.len() as u16;
+                let mut bytes = Vec::with_capacity(1 + 2 + payload.len());
+                bytes.push(0x03);
+                bytes.extend_from_slice(&sub_len.to_be_bytes()); // big-endian length
+                bytes.extend(payload);
+                bytes
+            }
+        }
+    }
+}
+
+/// For convenience, we implement `Push3Ast` using a *default* mapping.
+impl Push3Ast for UntypedAst {
+    fn to_bytecode(&self) -> Vec<u8> {
+        self.to_bytecode_with_mapping(&DEFAULT_OP_MAPPING)
+    }
+}
+
+/// A default mapping that corresponds to your current on-chain byte definitions.
+///
+/// This way, if your interpreter changes (e.g., `Minus` becomes 0x0A),
+/// you just update this mapping.
+pub struct DefaultOpCodeMapping;
+
+impl OpCodeMapping for DefaultOpCodeMapping {
+    fn opcode_byte(&self, op: &OpCode) -> u8 {
+        match op {
+            OpCode::Noop  => 0x00, // 0x00 => NOOP
+            OpCode::Plus  => 0x01, // 0x01 => INTEGER_PLUS
+            OpCode::Minus => 0x04, // 0x04 => INTEGER_MINUS
+            OpCode::Mult  => 0x05, // 0x05 => INTEGER_MULT
+            OpCode::Dup   => 0x06, // 0x06 => INTEGER_DUP
+            OpCode::Pop   => 0x07, // 0x07 => INTEGER_POP
+        }
+    }
+}
+
+/// A convenient global `const` or `static` for quick usage.
+pub const DEFAULT_OP_MAPPING: DefaultOpCodeMapping = DefaultOpCodeMapping;
+
+// ----------------------------------------------------------------------------
+// S-Expression Parsing Helpers
+// ----------------------------------------------------------------------------
+
+/// A simple S-expression tree for textual representation: either an `Atom` or a `List`.
+#[derive(Debug, Clone, PartialEq)]
+pub enum SExpr {
+    Atom(String),
+    List(Vec<SExpr>),
+}
+
+/// Tokenize a string into parentheses and symbols (atoms).
+pub fn tokenize(s: &str) -> Vec<String> {
+    let mut tokens = Vec::new();
+    let mut current = String::new();
+
+    for c in s.chars() {
+        match c {
+            '(' | ')' => {
+                if !current.trim().is_empty() {
+                    tokens.push(current.trim().to_string());
+                }
+                current.clear();
+                tokens.push(c.to_string());
+            }
+            ' ' | '\t' | '\n' | '\r' => {
+                if !current.trim().is_empty() {
+                    tokens.push(current.trim().to_string());
+                    current.clear();
+                }
+            }
+            _ => {
+                current.push(c);
+            }
+        }
+    }
+
+    if !current.trim().is_empty() {
+        tokens.push(current.trim().to_string());
+    }
+
+    tokens
+}
+
+/// Recursive helper to parse a single S-expression from a list of tokens, advancing `pos`.
+fn parse_sexpr_internal(tokens: &[String], pos: &mut usize) -> Result<SExpr, String> {
+    if *pos >= tokens.len() {
+        return Err("Unexpected end of tokens".to_string());
+    }
+
+    let token = &tokens[*pos];
+    match token.as_str() {
+        "(" => {
+            *pos += 1; // consume '('
+            let mut items = Vec::new();
+            while *pos < tokens.len() && tokens[*pos] != ")" {
+                let expr = parse_sexpr_internal(tokens, pos)?;
+                items.push(expr);
+            }
+            if *pos >= tokens.len() {
+                return Err("Missing closing parenthesis".to_string());
+            }
+            *pos += 1; // consume ')'
+            Ok(SExpr::List(items))
+        }
+        ")" => Err("Unexpected ')'".to_string()),
+        _ => {
+            let atom_str = token.clone();
+            *pos += 1;
+            Ok(SExpr::Atom(atom_str))
+        }
+    }
+}
+
+/// Parse a full string into a single top-level `SExpr`, assuming balanced parentheses.
+pub fn parse_string_to_sexpr(s: &str) -> Result<SExpr, String> {
+    let tokens = tokenize(s);
+    let mut pos = 0;
+    let expr = parse_sexpr_internal(&tokens, &mut pos)?;
+    if pos < tokens.len() {
+        Err(format!(
+            "Extra tokens after parse: {:?}",
+            &tokens[pos..]
+        ))
+    } else {
+        Ok(expr)
+    }
+}
+
+/// Convert an S-expression to an **untyped** AST node.
+pub fn sexpr_to_untyped(expr: &SExpr) -> Result<UntypedAst, String> {
+    match expr {
+        SExpr::Atom(text) => {
+            // 1) Try parse as integer
+            if let Ok(val) = text.parse::<i32>() {
+                Ok(UntypedAst::IntLiteral(val))
+            } else {
+                // 2) Otherwise interpret as an opcode
+                match text.to_uppercase().as_str() {
+                    "+" => Ok(UntypedAst::Instruction(OpCode::Plus)),
+                    "-" => Ok(UntypedAst::Instruction(OpCode::Minus)),
+                    "*" => Ok(UntypedAst::Instruction(OpCode::Mult)),
+                    "DUP" => Ok(UntypedAst::Instruction(OpCode::Dup)),
+                    "POP" => Ok(UntypedAst::Instruction(OpCode::Pop)),
+                    // unknown => treat as Noop
+                    _ => Ok(UntypedAst::Instruction(OpCode::Noop)),
+                }
+            }
+        }
+        SExpr::List(items) => {
+            let mut sub_asts = Vec::new();
+            for child in items {
+                sub_asts.push(sexpr_to_untyped(child)?);
+            }
+            Ok(UntypedAst::Sublist(sub_asts))
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------
+// (Optional) Placeholder for a future typed AST
+// ----------------------------------------------------------------------------
+
+// /// In the future, we plan to define a `TypedAst` enum that ensures each operation
+// /// has the correct number of typed children. We might also handle errors
+// /// if an operation expects two integer children, but the user tries to attach
+// /// a sublist or zero children, etc.
+// ///
+// /// For now, the untyped AST suffices for quick prototyping, but typed checks
+// /// will be crucial in more advanced genetic programming or static analysis scenarios.
+// #[derive(Debug, Clone)]
+// pub enum TypedAst {
+//     // e.g. IntLiteral(i32),
+//     //     Instruction(InstructionKind),
+// }
+
+// #[derive(Debug, Clone)]
+// pub enum InstructionKind {
+//     // e.g. Plus(Box<TypedAst>, Box<TypedAst>),
+//     //     Minus(Box<TypedAst>, Box<TypedAst>),
+//     //     Mult(Box<TypedAst>, Box<TypedAst>),
+//     //     Dup,
+//     //     Pop,
+// }
+
+// // etc.

offchain/src/compiler/mod.rs

@@ -0,0 +1,2 @@
+pub mod ast;
+pub mod push3_describtor;

offchain/src/compiler/push3_describtor.rs

@@ -0,0 +1,67 @@
+//! src/compiler/push3_descriptor.rs
+//! 
+//! A small module of helper functions to construct or interpret the 256-bit descriptors
+//! used by our on-chain `Push3Interpreter`. Each descriptor encodes a tag, an offset,
+//! a length, and any leftover bits (e.g., immediate data).
+
+use ethers::types::U256;
+
+/// The 256-bit descriptor layout is as follows:
+/// [  8 bits: tag  |  32 bits: offset  |  32 bits: length  |  184 bits: leftover ]
+///
+/// We'll define small helper functions to build or parse these. 
+/// Our `make_sublist_descriptor` is an example for tag=3 (SUBLIST).
+
+/// Tag constants, if you want them:
+pub const TAG_SUBLIST: u8 = 3;
+pub const TAG_INT_LITERAL: u8 = 2;
+pub const TAG_INSTRUCTION: u8 = 1;
+pub const TAG_NONE: u8 = 0;
+
+/// A small helper to shift the tag into the top 8 bits.
+#[inline]
+fn tag_bits(tag: u8) -> U256 {
+    U256::from(tag) << 248
+}
+
+/// Build a descriptor for a SUBLIST with the given offset and length (in bytes),
+/// leftover=0. 
+///
+/// # Example
+/// ```
+/// let desc = make_sublist_descriptor(0, code_bytes.len() as u32);
+/// // pass `desc` into the interpreter's exec stack
+/// ```
+pub fn make_sublist_descriptor(offset: u32, length: u32) -> U256 {
+    tag_bits(TAG_SUBLIST as u8)
+        | (U256::from(offset) << 216)
+        | (U256::from(length) << 184)
+        | U256::zero() // leftover
+}
+
+/// Possibly you want a more general helper that builds any descriptor:
+/// If you have other uses for leftover bits, you can pass that in:
+pub fn make_descriptor(tag: u8, offset: u32, length: u32, leftover: U256) -> U256 {
+    tag_bits(tag)
+        | (U256::from(offset) << 216)
+        | (U256::from(length) << 184)
+        | leftover
+}
+
+/// If you want to parse a descriptor, you can define getTag, getOffset, getLength, etc:
+pub fn get_tag(desc: U256) -> u8 {
+    // top 8 bits => shift right 248
+    (desc >> 248).as_u32() as u8
+}
+
+pub fn get_offset(desc: U256) -> u32 {
+    ((desc >> 216) & U256::from(u32::MAX)).as_u32()
+}
+
+pub fn get_length(desc: U256) -> u32 {
+    ((desc >> 184) & U256::from(u32::MAX)).as_u32()
+}
+
+pub fn get_low_184(desc: U256) -> U256 {
+    desc & ((U256::from(1u64) << 184) - 1)
+}

offchain/src/gp/generate.rs

@@ -0,0 +1,79 @@
+use rand::Rng;
+use crate::compiler::ast::{UntypedAst, OpCode};
+
+pub fn random_sublist_ast(rng: &mut impl Rng, max_depth: usize) -> UntypedAst {
+    // 1) Choose how many children the top-level `Sublist` will have.
+    let len = rng.gen_range(1..=3);
+
+    // 2) Build a vector of sub-ASTs by calling `random_ast` for each child
+    let mut children = Vec::with_capacity(len);
+    for _ in 0..len {
+        // We start at `depth=1` because the top-level sublist itself is `depth=0`.
+        children.push(random_ast(rng, 1, max_depth));
+    }
+
+    // 3) Return a `Sublist` as the root node
+    UntypedAst::Sublist(children)
+}
+
+/// Generate a random `UntypedAst` by recursively building sub-trees, 
+/// int literals, or instructions. 
+///
+/// - `depth` tracks how deep we are in the tree.
+/// - `max_depth` is the maximum allowed depth to prevent infinite recursion.
+pub fn random_ast(rng: &mut impl Rng, depth: usize, max_depth: usize) -> UntypedAst {
+    if depth >= max_depth {
+        // Return something "terminal," 
+        // e.g. an IntLiteral or a single Instruction
+        random_terminal(rng)
+    } else {
+        // Weighted choice: 
+        // 0 => IntLiteral, 
+        // 1 => single Instruction,
+        // 2 => Sublist with children
+        let choice = rng.gen_range(0..3);
+        match choice {
+            0 => UntypedAst::IntLiteral(rng.gen_range(-10..10)),
+            1 => UntypedAst::Instruction(random_opcode(rng)),
+            2 => {
+                // Make a sublist with 1..=3 children
+                let len = rng.gen_range(1..=3);
+                let mut children = Vec::with_capacity(len);
+                for _ in 0..len {
+                    children.push(random_ast(rng, depth + 1, max_depth));
+                }
+                UntypedAst::Sublist(children)
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+/// Generate a random "terminal" node. 
+/// Typically either an int literal or a single instruction.
+fn random_terminal(rng: &mut impl Rng) -> UntypedAst {
+    // Weighted choice:
+    // 0 => IntLiteral
+    // 1 => single Instruction
+    let choice = rng.gen_range(0..2);
+    match choice {
+        0 => UntypedAst::IntLiteral(rng.gen_range(-10..10)),
+        1 => UntypedAst::Instruction(random_opcode(rng)),
+        _ => unreachable!(),
+    }
+}
+
+/// Generate a random `OpCode` from your known set of instructions.
+pub fn random_opcode(rng: &mut impl Rng) -> OpCode {
+    let choice = rng.gen_range(0..6); 
+    // because we have 6 variants: Noop, Plus, Minus, Mult, Dup, Pop
+    match choice {
+        0 => OpCode::Noop,
+        1 => OpCode::Plus,
+        2 => OpCode::Minus,
+        3 => OpCode::Mult,
+        4 => OpCode::Dup,
+        5 => OpCode::Pop,
+        _ => unreachable!(),
+    }
+}

offchain/src/gp/generate_spec.rs

@@ -0,0 +1,121 @@
+use crate::compiler::ast::{UntypedAst, OpCode};
+use rand::Rng;
+use rand::prelude::SliceRandom;
+
+#[derive(Clone, Debug)]
+pub enum InstructionAtom {
+    /// A normal opcode, e.g. `Plus`, `Minus`, `Dup`, etc.
+    Opcode(OpCode),
+    /// An ephemeral random constant placeholder. 
+    /// If chosen, we generate a random literal on the spot.
+    EphemeralInt,
+    // If you want ephemeral floats, booleans, etc., add more variants
+}
+
+/// A small struct to hold our entire “instruction set.”
+#[derive(Clone, Debug)]
+pub struct InstructionSet {
+    pub atoms: Vec<InstructionAtom>,
+}
+
+impl InstructionSet {
+    pub fn new_default() -> Self {
+        // Example: Some opcodes + ephemeral constant
+        // Tweak as you like
+        use InstructionAtom::*;
+        use OpCode::*;
+
+        Self {
+            atoms: vec![
+                Opcode(Noop),
+                Opcode(Plus),
+                Opcode(Minus),
+                Opcode(Mult),
+                Opcode(Dup),
+                Opcode(Pop),
+                EphemeralInt,
+            ],
+        }
+    }
+    
+    /// Pick a random atom from this set.
+    /// If it's `EphemeralInt`, we produce `UntypedAst::IntLiteral(...)`.
+    /// If it's `Opcode(...)`, we produce `UntypedAst::Instruction(...)`.
+    pub fn random_atom_as_ast(&self, rng: &mut impl Rng) -> UntypedAst {
+        let idx = rng.gen_range(0..self.atoms.len());
+        match &self.atoms[idx] {
+            InstructionAtom::Opcode(op) => UntypedAst::Instruction(op.clone()),
+            InstructionAtom::EphemeralInt => {
+                // For ephemeral int, produce a random literal in some range
+                let val = rng.gen_range(-30..30);
+                UntypedAst::IntLiteral(val)
+            }
+        }
+    }
+}
+
+pub fn ranmdom_code_fixed(rng: &mut impl Rng, max_points: usize) -> UntypedAst {
+    let instr_set = InstructionSet::new_default();
+    return random_code(rng, &instr_set, max_points);
+}
+
+/// The "entry point": random_code(max_points).
+/// 1) Choose actual_points in [1..=max_points].
+/// 2) Return the result of random_code_with_size.
+pub fn random_code(rng: &mut impl Rng, instr_set: &InstructionSet, max_points: usize) -> UntypedAst {
+    let actual_points = rng.gen_range(1..=max_points);
+    random_code_with_size(rng, instr_set, actual_points)
+}
+
+/// The main logic: 
+///   If points == 1 => pick a single instruction/ephemeral 
+///   Else => 
+///       - We "decompose" (points - 1) among sub-codes
+///       - For each sub-points, we recursively call random_code_with_size
+///       - We return a Sublist of those children, possibly in random order
+pub fn random_code_with_size(
+    rng: &mut impl Rng,
+    instr_set: &InstructionSet,
+    points: usize,
+) -> UntypedAst {
+    use UntypedAst::*;
+
+    // Base case
+    if points == 1 {
+        // Choose a random "atom" from instr_set
+        return instr_set.random_atom_as_ast(rng);
+    } 
+
+    // If `points > 1`, let's produce a Sublist
+    // We'll break (points - 1) into sub-points via `decompose`
+    let subpoints_list = decompose(rng, points - 1, points - 1);
+    // subpoints_list is e.g. [2, 3, 5] and sums to (points-1)
+
+    // Then for each "subpoints", we do random_code_with_size 
+    let mut sub_asts: Vec<UntypedAst> = subpoints_list
+        .into_iter()
+        .map(|sp| random_code_with_size(rng, instr_set, sp))
+        .collect();
+
+    // The spec says "Return a list containing the results, in random order"
+    // so let's shuffle sub_asts
+    sub_asts.shuffle(rng);
+
+    Sublist(sub_asts)
+}
+
+/// Decompose a number into random parts. 
+/// 
+///  - If number is 1 or max_parts is 1 => return [number].
+///  - Otherwise pick a random split "this_part" and recurse on the remainder.
+fn decompose(rng: &mut impl Rng, number: usize, max_parts: usize) -> Vec<usize> {
+    if number == 1 || max_parts == 1 {
+        return vec![number];
+    }
+    // pick a random "this_part" in [1 .. (number-1)]
+    let this_part = rng.gen_range(1..number);
+    let mut remainder = decompose(rng, number - this_part, max_parts - 1);
+    let mut result = vec![this_part];
+    result.append(&mut remainder);
+    result
+}

offchain/src/gp/genetic_ops.rs

@@ -0,0 +1,64 @@
+use rand::Rng;
+use crate::compiler::ast::{UntypedAst, OpCode};
+use crate::gp::generate::{random_ast, random_opcode};
+
+/// Returns a new `UntypedAst` that is a mutated version of `original`.
+/// We do not modify `original`; we clone or build new pieces as needed.
+/// 
+/// - `depth`: current depth of this node,
+/// - `max_depth`: max allowed depth (to prevent infinite recursion).
+pub fn mutated_ast(original: &UntypedAst, rng: &mut impl Rng, depth: usize, max_depth: usize) -> UntypedAst {
+    // 10% chance: completely replace this node with a fresh random subtree
+    if rng.gen_range(0..100) < 10 {
+        return random_ast(rng, depth, max_depth);
+    }
+
+    match original {
+        UntypedAst::IntLiteral(val) => {
+            // Another small chance to replace the entire node with random subtree
+            if rng.gen_range(0..100) < 10 {
+                return random_ast(rng, depth, max_depth);
+            }
+
+            // Otherwise, "tweak" the int by a small offset
+            let delta = rng.gen_range(-2..=2);
+            let new_val = val.saturating_add(delta);
+            UntypedAst::IntLiteral(new_val)
+        }
+        UntypedAst::Instruction(op) => {
+            // 10% chance to replace node
+            if rng.gen_range(0..100) < 10 {
+                return random_ast(rng, depth, max_depth);
+            }
+
+            // 50% chance to pick a new opcode
+            // or else keep the same
+            if rng.gen_bool(0.5) {
+                UntypedAst::Instruction(random_opcode(rng))
+            } else {
+                // Just clone the original
+                UntypedAst::Instruction(op.clone())
+            }
+        }
+        UntypedAst::Sublist(children) => {
+            // 10% chance to replace this sublist entirely
+            if rng.gen_range(0..100) < 10 {
+                return random_ast(rng, depth, max_depth);
+            }
+
+            // Otherwise, mutate zero or more children
+            let mut new_children = children.clone();
+            if !new_children.is_empty() {
+                // Choose how many kids to mutate: 
+                // e.g., 1..=min(2, children.len())
+                let mut_count = rng.gen_range(1..=new_children.len().min(2));
+
+                for _ in 0..mut_count {
+                    let idx = rng.gen_range(0..new_children.len());
+                    new_children[idx] = mutated_ast(&new_children[idx], rng, depth+1, max_depth);
+                }
+            }
+            UntypedAst::Sublist(new_children)
+        }
+    }
+}

offchain/src/gp/local_mutation.rs

@@ -0,0 +1,114 @@
+//! src/gp/local_mutation.rs
+//! A localized mutation operator that makes small tweaks depending on node type.
+
+use rand::Rng;
+use crate::compiler::ast::{UntypedAst, OpCode};
+use crate::gp::mutation::{
+    enum_nodes_dfs, get_subtree, replace_subtree,
+};
+use crate::gp::generate_spec::{
+    InstructionAtom, InstructionSet,
+};
+
+/// A top-level function to perform a localized mutation with a chosen `InstructionSet`.
+pub fn local_mutation(
+    original: &UntypedAst,
+    rng: &mut impl Rng,
+    instr_set: &InstructionSet,
+) -> UntypedAst {
+    let all_paths = enum_nodes_dfs(original);
+    let idx = rng.gen_range(0..all_paths.len());
+    let chosen_path = &all_paths[idx];
+
+    let old_subtree = get_subtree(original, chosen_path);
+    let new_subtree = local_mutation_node(&old_subtree, rng, instr_set);
+    replace_subtree(original, chosen_path, new_subtree)
+}
+
+/// A convenience wrapper that always uses `InstructionSet::new_default()`.
+pub fn local_mutation_fixed(
+    original: &UntypedAst,
+    rng: &mut impl Rng,
+) -> UntypedAst {
+    let instr_set = InstructionSet::new_default();
+    local_mutation(original, rng, &instr_set)
+}
+
+fn local_mutation_node(
+    subtree: &UntypedAst,
+    rng: &mut impl Rng,
+    instr_set: &InstructionSet,
+) -> UntypedAst {
+    match subtree {
+        UntypedAst::IntLiteral(val) => {
+            let delta = rng.gen_range(-5..=5);
+            let new_val = val.saturating_add(delta);
+            UntypedAst::IntLiteral(new_val)
+        }
+        UntypedAst::Instruction(op) => {
+            let mut new_op = pick_random_opcode(rng, instr_set);
+            for _ in 0..3 {
+                if &new_op != op {
+                    break;
+                }
+                new_op = pick_random_opcode(rng, instr_set);
+            }
+            UntypedAst::Instruction(new_op)
+        }
+        UntypedAst::Sublist(children) => {
+            let choice = rng.gen_range(0..3);
+            let mut new_children = children.clone();
+
+            match choice {
+                0 => {
+                    // remove one child if possible
+                    if !new_children.is_empty() {
+                        let i = rng.gen_range(0..new_children.len());
+                        new_children.remove(i);
+                    }
+                }
+                1 => {
+                    // insert a new small node
+                    let i = rng.gen_range(0..=new_children.len());
+                    let node = create_small_node(rng, instr_set);
+                    new_children.insert(i, node);
+                }
+                2 => {
+                    // reorder two children
+                    if new_children.len() > 1 {
+                        let i = rng.gen_range(0..new_children.len());
+                        let j = rng.gen_range(0..new_children.len());
+                        new_children.swap(i, j);
+                    }
+                }
+                _ => {}
+            }
+
+            UntypedAst::Sublist(new_children)
+        }
+    }
+}
+
+fn pick_random_opcode(rng: &mut impl Rng, instr_set: &InstructionSet) -> OpCode {
+    use crate::compiler::ast::OpCode;
+
+    let mut opcode_list: Vec<&OpCode> = Vec::new();
+    for atom in &instr_set.atoms {
+        if let InstructionAtom::Opcode(ref op) = atom {
+            opcode_list.push(op);
+        }
+    }
+    if opcode_list.is_empty() {
+        // fallback => default to Noop
+        return OpCode::Noop;
+    }
+    let i = rng.gen_range(0..opcode_list.len());
+    opcode_list[i].clone()
+}
+
+fn create_small_node(
+    rng: &mut impl Rng,
+    instr_set: &InstructionSet,
+) -> UntypedAst {
+    instr_set.random_atom_as_ast(rng)
+}

offchain/src/gp/mod.rs

@@ -0,0 +1,6 @@
+pub mod population;
+pub mod genetic_ops;
+pub mod generate;
+pub mod generate_spec;
+pub mod mutation;
+pub mod local_mutation;

offchain/src/gp/mutation.rs

@@ -0,0 +1,147 @@
+use rand::Rng;
+use crate::compiler::ast::UntypedAst;
+use crate::gp::generate_spec::ranmdom_code_fixed; // or push3-based generator
+
+/// A "path" is a list of indices leading from the root to a child.
+/// For example, [] is the root, [0] is the root's first child, [0,1] is that child's second child, etc.
+pub type Path = Vec<usize>;
+
+/// Enumerate all nodes in a DFS order (root first).
+/// For each node, we store the `Path` (list of child indices).
+pub fn enum_nodes_dfs(ast: &UntypedAst) -> Vec<Path> {
+    let mut paths = Vec::new();
+    dfs_helper(ast, &mut paths, &mut vec![]);
+    paths
+}
+
+/// Recursive helper: `current_path` is a stack we push child indices onto.
+/// `paths` is the global list of final results.
+fn dfs_helper(ast: &UntypedAst, paths: &mut Vec<Path>, current_path: &mut Vec<usize>) {
+    // Record the current path as a valid node
+    paths.push(current_path.clone());
+
+    match ast {
+        UntypedAst::Sublist(children) => {
+            // For each child, push its index, recurse, then pop
+            for (i, child) in children.iter().enumerate() {
+                current_path.push(i);
+                dfs_helper(child, paths, current_path);
+                current_path.pop();
+            }
+        }
+        UntypedAst::IntLiteral(_) | UntypedAst::Instruction(_) => {
+            // Leaf node => no children
+        }
+    }
+}
+
+/// Replace the node at `path` in `original` with `replacement`, returning a new AST.
+/// If `path` is empty => we replace the root entirely.
+pub fn replace_subtree(
+    original: &UntypedAst,
+    path: &[usize],
+    replacement: UntypedAst
+) -> UntypedAst {
+    if path.is_empty() {
+        // means we’re replacing the root
+        return replacement;
+    }
+    // otherwise, we need to walk the sublist chain
+    match original {
+        UntypedAst::Sublist(children) => {
+            // let path_head = path[0], path_tail = path[1..]
+            let (first_idx, tail_path) = (path[0], &path[1..]);
+            let mut new_children = children.clone();
+            new_children[first_idx] = replace_subtree(&children[first_idx], tail_path, replacement);
+            UntypedAst::Sublist(new_children)
+        }
+        // If the path is not empty but we’re not in a Sublist => error or do nothing
+        UntypedAst::IntLiteral(_) | UntypedAst::Instruction(_) => {
+            // Possibly, if the path is invalid, we ignore. Or we treat it as "replace anyway."
+            // Here, we might treat it as an error or a no-op.
+            original.clone()
+        }
+    }
+}
+
+/// Produces a new AST by choosing exactly one node in `original` at random
+/// (by enumerating them), and replacing it with a new random subtree.
+pub fn mutate_by_index(
+    original: &UntypedAst,
+    rng: &mut impl Rng,
+    max_points: usize,
+) -> UntypedAst {
+    // 1) Enumerate all nodes => get a vector of `Path`
+    let all_paths = enum_nodes_dfs(original);
+    // pick a random path
+    let idx = rng.gen_range(0..all_paths.len());
+    let chosen_path = &all_paths[idx];
+
+    // 2) Generate a new subtree with our "fixed" random code generator
+    let new_subtree = ranmdom_code_fixed(rng, max_points);
+
+    // 3) Replace the subtree at `chosen_path` in `original` with `new_subtree`
+    replace_subtree(original, chosen_path, new_subtree)
+}
+
+/// Return the subtree of `original` at `path`, 
+/// cloning it as a `UntypedAst`. 
+/// If `path` is empty => returns the entire `original`.
+pub fn get_subtree(original: &UntypedAst, path: &[usize]) -> UntypedAst {
+    if path.is_empty() {
+        // The entire AST is the subtree
+        return original.clone();
+    }
+
+    match original {
+        UntypedAst::Sublist(children) => {
+            let (first_idx, tail_path) = (path[0], &path[1..]);
+            if first_idx >= children.len() {
+                // If path index is out of range, just clone the entire AST or 
+                // do something fallback
+                return original.clone();
+            }
+            get_subtree(&children[first_idx], tail_path)
+        }
+        UntypedAst::IntLiteral(_) | UntypedAst::Instruction(_) => {
+            // If path is non-empty but this is a leaf, 
+            // fallback: just return the leaf.
+            original.clone()
+        }
+    }
+}
+
+/// Perform a subtree crossover between two ASTs.
+/// 1) We pick a random node in `a` and a random node in `b`,
+/// 2) We swap those subtrees,
+/// 3) Return the two new ASTs.
+///
+/// Example usage:
+/// ```rust
+/// let (childA, childB) = crossover_by_index(&parentA, &parentB, &mut rng);
+/// ```
+pub fn crossover_by_index(
+    a: &UntypedAst,
+    b: &UntypedAst,
+    rng: &mut impl Rng,
+) -> (UntypedAst, UntypedAst) {
+    // 1) enumerate nodes in a
+    let paths_a = enum_nodes_dfs(a);
+    let idx_a = rng.gen_range(0..paths_a.len());
+    let chosen_a = &paths_a[idx_a];
+
+    // 2) enumerate nodes in b
+    let paths_b = enum_nodes_dfs(b);
+    let idx_b = rng.gen_range(0..paths_b.len());
+    let chosen_b = &paths_b[idx_b];
+
+    // 3) get subtree from a, from b
+    let subtree_a = get_subtree(a, chosen_a);
+    let subtree_b = get_subtree(b, chosen_b);
+
+    // 4) replace them
+    let new_a = replace_subtree(a, chosen_a, subtree_b);
+    let new_b = replace_subtree(b, chosen_b, subtree_a);
+
+    (new_a, new_b)
+}

offchain/src/gp/population.rs

@@ -0,0 +1,9 @@
+#[derive(Debug, Clone)]
+pub struct Individual {
+    pub fitness: f64,
+    // your Expr or bytecode or both
+}
+
+pub struct Population {
+    pub individuals: Vec<Individual>,
+}

offchain/src/helpers/artifact.rs

@@ -0,0 +1,41 @@
+//! src/helpers/artifact.rs
+//! A small helper module to read a Forge artifact JSON and extract the creation code.
+
+use anyhow::{anyhow, bail, Result};
+use serde::Deserialize;
+use std::fs;
+
+/// This mirrors the JSON structure: "bytecode": { "object": "...hex..." }
+#[derive(Debug, Deserialize)]
+struct BytecodeObject {
+    object: String,
+}
+
+/// The top-level artifact with a "bytecode" field.
+#[derive(Debug, Deserialize)]
+struct MyContractArtifact {
+    bytecode: BytecodeObject,
+}
+
+/// Reads the given JSON file (a Forge artifact) and returns the raw creation code bytes.
+///
+/// * `filename`: path to the artifact JSON (e.g. `../onchain/out/Push3Interpreter.sol/Push3Interpreter.json`)
+pub fn get_creation_code(filename: &str) -> Result<Vec<u8>> {
+    // 1) Read the JSON file
+    let creation_json = fs::read_to_string(filename)
+        .map_err(|e| anyhow!("Failed to read JSON file {}: {}", filename, e))?;
+    
+    // 2) Parse
+    let contract_artifact: MyContractArtifact = serde_json::from_str(&creation_json)
+        .map_err(|e| anyhow!("Failed to parse JSON artifact: {}", e))?;
+
+    // 3) Extract the hex code
+    let raw_hex = &contract_artifact.bytecode.object;
+    let stripped_hex = raw_hex.trim_start_matches("0x");
+
+    // 4) Convert from hex => bytes
+    match hex::decode(stripped_hex) {
+        Ok(bytes) => Ok(bytes),
+        Err(e) => bail!("Invalid hex for creation code: {e}"),
+    }
+}

offchain/src/helpers/mod.rs

@@ -0,0 +1 @@
+pub mod artifact;

offchain/src/lib.rs

@@ -0,0 +1,4 @@
+pub mod compiler;
+pub mod runner;
+pub mod gp;
+pub mod helpers;

offchain/src/main.rs

@@ -0,0 +1,118 @@
+// src/main.rs
+use std::env;
+
+// We’ll use your existing AST definitions for parsing
+use offchain::compiler::ast::{
+    parse_string_to_sexpr,
+    sexpr_to_untyped,
+    Push3Ast, // The trait
+    UntypedAst, // The untyped AST enum
+};
+
+use offchain::runner::revm_runner::{EvmRunner, Push3InterpreterOutputs}; // <--- We import our EvmRunner
+
+use anyhow::{anyhow, bail, Result};
+use hex;
+use serde::Deserialize; // For JSON artifact loading
+
+// If you still need these (not strictly required anymore):
+// use database::CacheDB;
+// use revm::{
+//     context::Context,
+//     context_interface::result::{ExecutionResult, Output},
+//     database_interface::EmptyDB,
+//     handler::EthHandler,
+//     primitives::{Bytes, TxKind},
+//     EvmCommit, MainEvm,
+// };
+use ethers::abi::{decode, ParamType};
+use ethers::types::U256;
+
+// ----------------------------------------------------------------------
+// JSON artifact struct, as before
+// ----------------------------------------------------------------------
+#[derive(Debug, Deserialize)]
+struct BytecodeObject {
+    object: String,
+}
+
+#[derive(Debug, Deserialize)]
+struct MyContractArtifact {
+    bytecode: BytecodeObject,
+}
+
+// ----------------------------------------------------------------------
+// MAIN
+// ----------------------------------------------------------------------
+fn main() -> Result<()> {
+    // 1) Read CLI arguments for the Push3 program
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        eprintln!("Usage: cargo run -- '<program>'");
+        eprintln!("Example: cargo run -- '((3 5 +) DUP MUL)'");
+        std::process::exit(1);
+    }
+    let program_str = &args[1];
+
+    // 2) Parse the string into an S-expression
+    let sexpr = parse_string_to_sexpr(program_str)
+        .map_err(|e| anyhow!("Error parsing S-expression: {}", e))?;
+
+    // 3) Convert SExpr => UntypedAst
+    let ast: UntypedAst = sexpr_to_untyped(&sexpr)
+        .map_err(|e| anyhow!("Error converting to UntypedAst: {}", e))?;
+
+    // 4) Convert UntypedAst => Push3 bytecode (for debugging, so we can see it)
+    let bytecode = ast.to_bytecode();
+
+    // 5) Print the resulting AST and bytecode (in hex)
+    println!("AST: {:?}", ast);
+    println!("Bytecode (hex): 0x{}", hex::encode(&bytecode));
+
+    // ----------------------------------------------------------------------
+    // Load the creation code (bytecode) from a JSON artifact
+    // ----------------------------------------------------------------------
+    let creation_hex_filename = "../onchain/out/Push3Interpreter.sol/Push3Interpreter.json";
+    let creation_json = std::fs::read_to_string(creation_hex_filename)
+        .map_err(|e| anyhow!("Failed to read JSON file {}: {}", creation_hex_filename, e))?;
+    let contract_artifact: MyContractArtifact = serde_json::from_str(&creation_json)
+        .map_err(|e| anyhow!("Failed to parse JSON artifact: {}", e))?;
+
+    let raw_hex = &contract_artifact.bytecode.object;
+    let stripped_hex = raw_hex.trim_start_matches("0x");
+
+    let creation_bytes = match hex::decode(stripped_hex) {
+        Ok(bytes) => bytes,
+        Err(e) => bail!("Invalid hex for creation code: {e}"),
+    };
+
+    println!(
+        "Loaded creation code ({} bytes) from {}",
+        creation_bytes.len(),
+        creation_hex_filename
+    );
+
+    // ----------------------------------------------------------------------
+    // 6) Deploy the interpreter in an ephemeral EVM using `EvmRunner`
+    // ----------------------------------------------------------------------
+    let mut runner = EvmRunner::new(creation_bytes)?;
+    println!("Interpreter deployed successfully in ephemeral EVM at: 0x{:x}", runner.interpreter_addr);
+
+    // ----------------------------------------------------------------------
+    // 7) Evaluate the AST in our EVM
+    // ----------------------------------------------------------------------
+    // We'll call `runner.run_ast(&ast)`, which:
+    // - Converts AST => push3 code,
+    // - Builds a sublist descriptor in the exec stack,
+    // - Calls `runInterpreter`,
+    // - Returns final stacks in a `Push3InterpreterOutputs`.
+    let outputs = runner.run_ast(&ast)?;
+    println!("Ran the AST successfully!");
+
+    // 8) Print the final stacks
+    println!("Final CODE stack: {:?}", outputs.final_code_stack);
+    println!("Final EXEC stack: {:?}", outputs.final_exec_stack);
+    println!("Final INT stack: {:?}", outputs.final_int_stack);
+
+    Ok(())
+}

offchain/src/runner/mod.rs

@@ -0,0 +1 @@
+pub mod revm_runner;

offchain/src/runner/revm_runner.rs

@@ -0,0 +1,232 @@
+//! src/evm_integration/revm_runner.rs
+//! 
+//! This module provides a thin wrapper around REVM to deploy a Push3Interpreter
+//! contract, then call its `runInterpreter(...)` function with flexible inputs/outputs,
+//! using the same style (Context::builder(), .modify_tx_chained, etc.) you had in your main.
+
+use anyhow::{anyhow, bail, Result};
+use ethers::abi::{encode, decode, Token, ParamType};
+use ethers::types::U256;
+use ethers::utils;
+use database::CacheDB;
+use revm::{
+    context::Context,
+    context::{BlockEnv, TxEnv, CfgEnv},
+    context_interface::result::{ExecutionResult, Output},
+    database_interface::EmptyDB,
+    handler::EthHandler,
+    primitives::{Bytes, TxKind}, // 4 generics
+    EvmCommit,
+    MainEvm,
+};
+
+// We import your AST definitions so we can call `ast.to_bytecode()`.
+use crate::compiler::ast::{UntypedAst, Push3Ast};
+
+// If you have a descriptor helper (like make_sublist_descriptor), bring it in:
+use crate::compiler::push3_describtor::make_sublist_descriptor;
+
+/// The input parameters for `runInterpreter(...)`: four fields (code, codeStack, execStack, intStack).
+pub struct Push3InterpreterInputs {
+    pub code: Vec<u8>,
+    pub init_code_stack: Vec<U256>,
+    pub init_exec_stack: Vec<U256>,
+    pub init_int_stack: Vec<i128>,
+}
+
+/// The outputs from `runInterpreter(...)`: three arrays for code/exec/int stacks.
+pub struct Push3InterpreterOutputs {
+    pub final_code_stack: Vec<U256>,
+    pub final_exec_stack: Vec<U256>,
+    pub final_int_stack: Vec<i128>,
+}
+
+/// A thin wrapper around REVM, parameterized by the 4 generics (DB, BLOCK, TX, CFG).
+/// - We store the ephemeral EVM instance,
+/// - We store the deployed address of your `Push3Interpreter`,
+/// - We provide `run_interpreter` and `run_ast`.
+pub struct EvmRunner {
+    /// The 4-parameter MainEvm:
+    ///   DB = CacheDB<EmptyDB>,
+    ///   BLOCK = BlockEnv,
+    ///   TX = TxEnv,
+    ///   CFG = CfgEnv
+    pub evm: MainEvm<CacheDB<EmptyDB>, BlockEnv, TxEnv, CfgEnv>,
+
+    /// The address where Push3Interpreter was deployed.
+    pub interpreter_addr: revm::primitives::Address,
+}
+
+impl EvmRunner {
+    /// Deploy a new ephemeral EVM with a "Create" transaction for the given `creation_code`.
+    ///
+    /// This matches your older style of:
+    ///  `MainEvm::new(Context::builder()... .with_db(...), EthHandler::default())`
+    pub fn new(creation_code: Vec<u8>) -> Result<Self> {
+        // 1) Create the EVM using your old style: `Context::builder()...`
+        //    Then pass to MainEvm::new(...).
+        //    The difference is that we explicitly say MainEvm<DB,BLOCK,TX,CFG>.
+        let mut evm = MainEvm::new(
+            // a) Prepare context with a chained transaction to CREATE
+            Context::builder()
+                .modify_tx_chained(|tx| {
+                    tx.transact_to = TxKind::Create;
+                    tx.data = Bytes::from(creation_code.clone());
+                })
+                // b) Provide ephemeral DB
+                .with_db(CacheDB::<EmptyDB>::default()),
+            // c) The EthHandler for block/tx environment logic
+            EthHandler::default(),
+        );
+
+        // 2) Execute the CREATE transaction
+        let creation_result = evm.exec_commit()?;
+        let ExecutionResult::Success {
+            output: Output::Create(_, Some(deployed_addr)),
+            ..
+        } = creation_result
+        else {
+            bail!("Interpreter deployment failed or no address returned: {creation_result:#?}");
+        };
+
+        // 3) Return the EvmRunner
+        Ok(Self {
+            evm,
+            interpreter_addr: deployed_addr,
+        })
+    }
+
+    /// Call `runInterpreter(bytes,uint256[],uint256[],int256[])` on the deployed contract,
+    /// returning the final code/exec/int stacks.
+    pub fn run_interpreter(
+        &mut self,
+        inputs: &Push3InterpreterInputs
+    ) -> Result<Push3InterpreterOutputs> {
+        // 1) Build function selector
+        let func_selector = &utils::id("runInterpreter(bytes,uint256[],uint256[],int256[])")[0..4];
+
+        // 2) Convert each field to `ethers::abi::Token`
+        let code_token = Token::Bytes(inputs.code.clone());
+        let init_code_stack = Token::Array(
+            inputs.init_code_stack
+                .iter()
+                .map(|&u| Token::Uint(u))
+                .collect()
+        );
+        let init_exec_stack = Token::Array(
+            inputs.init_exec_stack
+                .iter()
+                .map(|&u| Token::Uint(u))
+                .collect()
+        );
+        let init_int_stack = Token::Array(
+            inputs.init_int_stack
+                .iter()
+                .map(|&val_i128| {
+                    // store i128 as a U256. If you need negative values, do a two’s complement approach.
+                    let as_u128 = val_i128 as u128;
+                    Token::Int(U256::from(as_u128))
+                })
+                .collect()
+        );
+
+        // 3) Encode
+        let encoded_args = encode(&[
+            code_token,
+            init_code_stack,
+            init_exec_stack,
+            init_int_stack,
+        ]);
+
+        // 4) Build final call data
+        let mut call_data = Vec::from(func_selector);
+        call_data.extend_from_slice(&encoded_args);
+
+        // 5) Modify the transaction to CALL the deployed interpreter
+        self.evm.context.modify_tx(|tx| {
+            tx.transact_to = TxKind::Call(self.interpreter_addr);
+            tx.data = Bytes::from(call_data);
+            tx.nonce = 1; // increment nonce to avoid reuse
+        });
+
+        // 6) Execute the call
+        let call_result = self.evm.transact()?;
+        match &call_result.result {
+            ExecutionResult::Success {
+                output: Output::Call(return_data),
+                ..
+            } => {
+                // 7) Decode (uint256[], uint256[], int256[])
+                let param_types = &[
+                    ParamType::Array(Box::new(ParamType::Uint(256))), // finalCodeStack
+                    ParamType::Array(Box::new(ParamType::Uint(256))), // finalExecStack
+                    ParamType::Array(Box::new(ParamType::Int(256))),  // finalIntStack
+                ];
+                let decoded = decode(param_types, return_data)
+                    .map_err(|e| anyhow!("Failed to decode return data: {e}"))?;
+
+                // parse each array
+                let final_code_stack = match &decoded[0] {
+                    Token::Array(arr) => arr.iter().filter_map(|t| {
+                        if let Token::Uint(u) = t { Some(*u) } else { None }
+                    }).collect(),
+                    _ => Vec::new(),
+                };
+                let final_exec_stack = match &decoded[1] {
+                    Token::Array(arr) => arr.iter().filter_map(|t| {
+                        if let Token::Uint(u) = t { Some(*u) } else { None }
+                    }).collect(),
+                    _ => Vec::new(),
+                };
+                let final_int_stack = match &decoded[2] {
+                    Token::Array(arr) => arr.iter().filter_map(|t| {
+                        if let Token::Int(u256_val) = t {
+                            // read only the lower 128 bits => ignoring sign extension
+                            let lo = u256_val.low_u128();
+                            Some(lo as i128)
+                        } else {
+                            None
+                        }
+                    }).collect(),
+                    _ => Vec::new(),
+                };
+
+                Ok(Push3InterpreterOutputs {
+                    final_code_stack,
+                    final_exec_stack,
+                    final_int_stack,
+                })
+            }
+            ExecutionResult::Revert { gas_used, output } => {
+                bail!("Call reverted: gas used={gas_used:?}, output={output:?}")
+            }
+            other => {
+                bail!("Call failed: {other:?}")
+            }
+        }
+    }
+
+    /// A convenience method to run an `UntypedAst`:
+    /// - Convert AST => push3 code,
+    /// - Build a sublist descriptor in the exec stack,
+    /// - Call `run_interpreter`.
+    pub fn run_ast(&mut self, ast: &UntypedAst) -> Result<Push3InterpreterOutputs> {
+        // 1) Convert AST => push3 bytecode
+        let code_bytes = ast.to_bytecode();
+        let code_len = code_bytes.len() as u32;
+
+        // 2) Build a sublist descriptor
+        let descriptor = make_sublist_descriptor(0, code_len);
+
+        // 3) Put code in `code` and sublist descriptor in `execStack`
+        let inputs = Push3InterpreterInputs {
+            code: code_bytes,
+            init_code_stack: Vec::new(),
+            init_exec_stack: vec![descriptor],
+            init_int_stack: Vec::new(),
+        };
+
+        // 4) Run interpreter
+        self.run_interpreter(&inputs)
+    }
+}