Integrator.hpp

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#pragma once

 
#include <functional>
#include <icarus/core/CoreTypes.hpp>
#include <icarus/sim/integrators/IntegratorTypes.hpp>
#include <string>
 
namespace icarus {
 
// =============================================================================
// Adaptive Step Result
// =============================================================================

template <typename Scalar> struct AdaptiveStepResult {
    JanusVector<Scalar> state; 
    Scalar dt_actual;          
    Scalar error_estimate;     
    bool accepted;             
};
 
// =============================================================================
// Abstract Integrator Interface
// =============================================================================

template <typename Scalar> class Integrator {
  public:
    virtual ~Integrator() = default;

    using DerivativeFunc =
        std::function<JanusVector<Scalar>(Scalar t, const JanusVector<Scalar> &x)>;

    virtual JanusVector<Scalar> Step(const DerivativeFunc &f, const JanusVector<Scalar> &x,
                                     Scalar t, Scalar dt) = 0;

    [[nodiscard]] virtual std::string Name() const = 0;

    [[nodiscard]] virtual int Order() const = 0;

    [[nodiscard]] virtual IntegratorType Type() const = 0;

    [[nodiscard]] virtual bool IsAdaptive() const { return false; }
};
 
// =============================================================================
// Adaptive Integrator Interface
// =============================================================================

template <typename Scalar> class AdaptiveIntegrator : public Integrator<Scalar> {
  public:
    using typename Integrator<Scalar>::DerivativeFunc;

    virtual AdaptiveStepResult<Scalar>
    AdaptiveStep(const DerivativeFunc &f, const JanusVector<Scalar> &x, Scalar t, Scalar dt) = 0;
 
    [[nodiscard]] bool IsAdaptive() const override { return true; }

    virtual void SetAbsTol(Scalar tol) = 0;

    virtual void SetRelTol(Scalar tol) = 0;

    [[nodiscard]] virtual Scalar GetAbsTol() const = 0;

    [[nodiscard]] virtual Scalar GetRelTol() const = 0;
};
 
} // namespace icarus