integrator.h

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#ifndef LIBSIMINTEGRATORS_INTEGRATOR_H
#define LIBSIMINTEGRATORS_INTEGRATOR_H
 
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
 
#include "oakfield/field.h"
 
struct SimContext;
struct SimBackend;
 
#ifdef __cplusplus
extern "C" {
#endif
 
typedef SimField Field;
 
struct Integrator;
 
typedef SimResult (*IntegratorDriftFn)(struct Integrator *integrator, const Field *field,
                                       const double *state, double *out_derivative, size_t count);
 
typedef SimResult (*IntegratorNoiseFn)(struct Integrator *integrator, const Field *field,
                                       double *out_noise, size_t count);
 
typedef void (*IntegratorDestroyFn)(struct Integrator *integrator);
 
typedef void (*IntegratorStepFn)(struct Integrator *integrator, Field *field, double dt);
 
typedef struct IntegratorConfig {
    IntegratorDriftFn drift;     
    IntegratorNoiseFn noise;     
    IntegratorDestroyFn destroy; 
    void *userdata;              
    size_t target_field_index;   
    double initial_dt;           
    double min_dt;               
    double max_dt;               
    double tolerance;            
    double safety;               
    bool adaptive;               
    bool enable_stochastic;      
    double stochastic_strength;  
    uint32_t random_seed;        
    size_t workspace_hint;       
    double subordination_alpha;  
    size_t subordination_quadrature_n; 
} IntegratorConfig;
 
typedef struct Integrator {
    char name[32];                     
    IntegratorStepFn step;             
    IntegratorDriftFn drift;           
    IntegratorNoiseFn noise;           
    IntegratorDestroyFn destroy;       
    void *userdata;                    
    bool adaptive;                     
    bool enable_stochastic;            
    double min_dt;                     
    double max_dt;                     
    double tolerance;                  
    double safety;                     
    double current_dt;                 
    double last_step;                  
    double last_error;                 
    double stochastic_strength;        
    uint32_t rng_state;                
    uint32_t last_attempt_count;       
    uint32_t last_rejection_count;     
    double **buffers;                  
    size_t buffer_count;               
    size_t buffer_elements;            
    size_t buffer_element_size;        
    void **drift_snapshots;            
    size_t *drift_snapshot_sizes;      
    size_t *drift_snapshot_capacities; 
    size_t drift_snapshot_count;       
    void *drift_state_scratch; 
    size_t drift_state_scratch_capacity; 
    size_t target_field_index;           
    double subordination_alpha;        
    size_t subordination_quadrature_n; 
    bool is_complex;                   
    double split_feedback_dt; 
    double split_feedback_max_error;  
    uint32_t split_feedback_substeps; 
} Integrator;
 
SimResult integrator_configure(Integrator *integrator, const char *name, IntegratorStepFn step_fn,
                               const IntegratorConfig *config);
 
void integrator_destroy(Integrator *integrator);
 
SimResult integrator_ensure_workspace(Integrator *integrator, size_t buffers, size_t elements);
 
double *integrator_buffer(Integrator *integrator, size_t index);
 
size_t integrator_state_length(const Field *field);
 
double integrator_clamp_dt(const Integrator *integrator, double dt);
 
double integrator_suggest_dt(const Integrator *integrator, double dt, double error_norm,
                             double method_order);
 
double integrator_reject_dt(const Integrator *integrator, double dt, double error_norm,
                            double method_order);
 
double integrator_measure_error(const double *a, const double *b, size_t count);
 
double integrator_rng_normal(Integrator *integrator);
 
uint64_t integrator_workspace_bytes(const Integrator *integrator);
 
uint64_t integrator_drift_scratch_bytes(const Integrator *integrator);
 
void integrator_apply_stochastic(Integrator *integrator, Field *field, double *scratch,
                                 size_t count, double dt);
 
double integrator_last_step(const Integrator *integrator);
 
double integrator_next_step(const Integrator *integrator);
 
double integrator_measure_error_complex(const SimComplexDouble *a, const SimComplexDouble *b,
                                        size_t n);
 
SimComplexDouble *integrator_buffer_complex(Integrator *integrator, unsigned int index);
 
SimResult integrator_noise_gaussian(struct Integrator *integrator, const Field *field,
                                    double *out_noise, size_t count);
 
SimResult integrator_noise_uniform(struct Integrator *integrator, const Field *field,
                                   double *out_noise, size_t count);
 
SimResult integrator_noise_laplace(struct Integrator *integrator, const Field *field,
                                   double *out_noise, size_t count);
 
double integrator_last_error(const Integrator *integrator);
 
SimResult integrator_context_drift(Integrator *integrator, const Field *field, const double *state,
                                   double *out_derivative, size_t count);
 
SimResult integrator_step_context(Integrator *integrator, struct SimContext *context,
                                  struct SimBackend *backend, double dt);
 
#ifdef __cplusplus
}
#endif
 
#endif /* LIBSIMINTEGRATORS_INTEGRATOR_H */