Draft of grammatical evolution.

ge.h

/**
 * @file grammatical_evolution.h
 * @brief Functions to use grammatical evolution to evolve programs, mathematical
 * functions, sentences, whatever you want, just use your imagination!
 */
#ifndef RAW_GRAMMATICAL_EVOLUTION_H_
#define RAW_GRAMMATICAL_EVOLUTION_H_

#include "raw/common.h"
#include "raw/grammar.h"
#include "raw/codons.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Stores all the information for grammatical evolution.
 */
typedef struct {
  size_t pop_size;    // Number of solutions considered.
  size_t codon_size;  // Number of integers in the codons (the solutions).
  size_t max_wrap;    // Do you allow wrapping? How many times? 0 is the correct answer.
  sfmt_t* rng;        // Random number generator.
  size_t elite;       // The top solutions to keep unchanged and use for the next generation.
  r_codons* codons;   // The population of solutions
  char** output;      // Output of the codons. NULL if the codon failed to generate a valid string.
  r_grammar* g;       // The grammar.
} r_ge;

/**
 * @brief Initializes an object for grammatical evolution.
 * 
 * @param g           Uninitialized grammatical evolution object.
 * @param seed        Seed for the random number generator.
 * @param pop_size    Size of the population of solutions.
 * @param elites      Number of solutions to keep unchanged and used to generate the next batch of solutions.
 * @param mutation    Probability that an integer will mutate. Should be a small number (e.g.: 0.001).
 * @param codon_size  How many integers to generate strings. 100-1000 are good numbers.
 * @param max_wrap    Whether you allow wrapping the integer sequence and if so, how many times.
 * @param grammar     A string representing the grammar (see grammar folder for examples).
 * @param err         Stores parsing errors. If NULL, errors will be ignored.
 */
void r_ge_init(r_ge* g, size_t seed, size_t pop_size, size_t elites,
               double mutation, size_t codon_size, size_t max_wrap,
               const char* grammar, r_parsing_err* err);

/**
 * @brief Generates new solutions (g->codons) and new strings (g->output) given
 * an array of fitnesses (higher = better) for the previous generation's output,
 * 
 * @param g           Initialized grammatical evolution object.
 * @param fitnesses   Fitness for all outputs (must have the same number of elements as g->pop_size).
 */
void r_ge_one_step(r_ge* g, double* fitnesses);

/**
 * @brief Frees memory.
 */
void r_ge_free(r_ge* g);

#ifdef __cplusplus
}
#endif

#endif