PolynomialChaos.h

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//* This file is part of the MOOSE framework
//* https://mooseframework.inl.gov
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html

#pragma once

#include "SurrogateModel.h"
#include "PolynomialQuadrature.h"
#include "QuadratureSampler.h"

#include "Distribution.h"
#include "nlohmann/json.h"

class PolynomialChaos : public SurrogateModel
{
public:
  static InputParameters validParams();
  PolynomialChaos(const InputParameters & parameters);
  using SurrogateModel::evaluate;
  virtual Real evaluate(const std::vector<Real> & x) const override;

  std::size_t getNumberOfParameters() const { return _poly.size(); }

  std::size_t getNumberofCoefficients() const { return _tuple.size(); }

  const std::vector<std::vector<unsigned int>> & getPolynomialOrders() const;
  unsigned int getPolynomialOrder(const unsigned int dim, const unsigned int i) const;

  const std::vector<Real> & getCoefficients() const;

  virtual Real computeMean() const;

  virtual Real computeStandardDeviation() const;

  Real powerExpectation(const unsigned int n) const;

  Real computeDerivative(const unsigned int dim, const std::vector<Real> & x) const;
  Real computePartialDerivative(const std::vector<unsigned int> & dim,
                                const std::vector<Real> & x) const;

  Real computeSobolIndex(const std::set<unsigned int> & ind) const;
  Real computeSobolTotal(const unsigned int dim) const;

  void store(nlohmann::json & json) const;

private:
  mutable dof_id_type _n_local_coeff = std::numeric_limits<dof_id_type>::max();
  mutable dof_id_type _local_coeff_begin = 0;
  mutable dof_id_type _local_coeff_end = 0;
  void linearPartitionCoefficients() const;

  // The following items are loaded from a SurrogateTrainer using getModelData

  const unsigned int & _order;

  const unsigned int & _ndim;

  const std::size_t & _ncoeff;

  const std::vector<std::vector<unsigned int>> & _tuple;

  const std::vector<Real> & _coeff;

  const std::vector<std::unique_ptr<const PolynomialQuadrature::Polynomial>> & _poly;

  friend void to_json(nlohmann::json & json, const PolynomialChaos * const & pc);
};