getfem_integration.h

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/* -*- c++ -*- (enables emacs c++ mode) */
/*===========================================================================
 
 Copyright (C) 2000-2026 Yves Renard
 
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/**@file getfem_integration.h
   @author  Yves Renard <Yves.Renard@insa-lyon.fr>
   @date December 17, 2000.
   @brief Integration methods (exact and approximated) on convexes
 
   @section im_list List of integration methods for getfem::int_method_descriptor
 
   - "IM_EXACT_SIMPLEX(n)"             : exact integration on simplexes.
   - "IM_PRODUCT(IM1, IM2)"            : product of two integration methods
   - "IM_EXACT_PARALLELEPIPED(n)"      : exact integration on parallelepipeds
   - "IM_EXACT_PRISM(n)"               : exact integration on prisms
   - "IM_GAUSS1D(K)"                   : Gauss method on the segment, 
                                         order K=1, 3, 5, 7, ..., 99.
   - "IM_GAUSSLOBATTO1D(K)"            : Gauss-Lobatto method on the segment, 
                                         order K=1, 3, 5, 7, ..., 99.
   - "IM_NC(N,K)"                      : Newton-Cotes approximative 
                                         integration on simplexes, order K
   - "IM_NC_PARALLELEPIPED(N,K)"       : product of Newton-Cotes integration 
                                         on parallelepipeds
   - "IM_NC_PRISM(N,K)"                : product of Newton-Cotes integration
                                         on prisms
   - "IM_GAUSS_PARALLELEPIPED(N,K)"    : product of Gauss1D integration
                                         on parallelepipeds (K=1,3,..99)
   - "IM_TRIANGLE(K)"                  : Gauss methods on triangles
                                         (K=1..10,13,17,19)
   - "IM_QUAD(K)"                      : Gauss methods on quadrilaterons
                                         (K=2, 3, 5, 7, 9, 17)
   - "IM_HEXAHEDRON(K)"                : Gauss methods on hexahedrons
                                         (K=5,9,11)
   - "IM_TETRAHEDRON(K)"               : Gauss methods on tetrahedrons
                                         (K=1, 2, 3, 5, 6, or 8)
   - "IM_SIMPLEX4D(3)"                 : Gauss method on a 4-dimensional
                                         simplex.
   - "IM_CUBE4D(K)"                    : Gauss method on a 4-dimensional cube
                                         (K=5,9).
   - "IM_STRUCTURED_COMPOSITE(IM1, K)" : Composite method on a grid with
                                         K divisions
   - "IM_HCT_COMPOSITE(IM1)"           : Composite integration suited to the
                                         HCT composite finite element.
   - "IM_QUAQC1_COMPOSITE(IM1)"        : Composite integration suited to the
                                         QUADC1 composite finite element.
 
   - "IM_QUASI_POLAR(IM1, IP1)"        : if IM1 is an integration method on a
               square, gives an integration method on a triangle which is
               close to a polar integration with respect to vertex IP1.
               if IM1 is an integration method on a tetrahedron, gives an
               integration method on a tetrahedron which is close to a
               cylindrical integration with respect to vertex IP1
               (does not work very well).
               if IM1 is an integration method on a prism. Gives an integration
               method on a tetrahedron which is close to a
               cylindrical integration with respect to vertex IP1.
 
   - "IM_QUASI_POLAR(IM1, IP1, IP2)"   : IM1 should be an integration method
               on a prism. Gives an integration method on a tetrahedron which
               is close to a cylindrical integration with respect to IP1-IP2
               axis.
 
   - "IM_PYRAMID_COMPOSITE(IM1)"       : Composite integration for a pyramid
                                         decomposed into two tetrahedrons
*/
#ifndef GETFEM_INTEGRATION_H__
#define GETFEM_INTEGRATION_H__
 
#include "getfem_config.h"
#include "bgeot_convex_ref.h"
#include "bgeot_geometric_trans.h"
#include "bgeot_node_tab.h"
#include "bgeot_poly_composite.h"
#include "getfem/dal_naming_system.h"
 
 
 
 
namespace getfem
{
  /** Description of an exact integration of polynomials.
   *  This class is not to be manipulate by itself. Use ppoly_integration and
   *  the functions written to produce the basic descriptions.
   */
  class poly_integration {
    protected :
 
      bgeot::pconvex_structure cvs;
 
      mutable std::vector<long_scalar_type> int_monomials;
      mutable std::vector< std::vector<long_scalar_type> > int_face_monomials;
 
    public :
 
      /// Dimension of convex of reference.
      dim_type dim(void) const { return cvs->dim(); }
      /// {Structure of convex of reference.  
      bgeot::pconvex_structure structure(void) const { return cvs; }
 
      virtual long_scalar_type int_monomial(const bgeot::power_index &power)
        const = 0;
      virtual long_scalar_type int_monomial_on_face(const bgeot::power_index
                                                    &power, short_type f) const = 0;
 
      /// Evaluate the integral of the polynomial P on the reference element.
      long_scalar_type int_poly(const base_poly &P) const;
      /** Evaluate the integral of the polynomial P on the face f of the
       *    reference element.
       */
      long_scalar_type int_poly_on_face(const base_poly &P,
                                        short_type f) const;
 
      virtual ~poly_integration() {}
 
  };
 
  typedef std::shared_ptr<const poly_integration> ppoly_integration;
 
   /** Description of an approximate integration of polynomials of
   *  several variables on a reference element.
   *  This class is not to be manipulate by itself. Use papprox\_integration
   *  and the functions written to produce the basic descriptions.
   */
 
  class integration_method;  
  typedef std::shared_ptr<const integration_method> pintegration_method;
 
 
  class approx_integration {
  protected :
    
    typedef bgeot::node_tab PT_TAB;
    bgeot::pconvex_ref cvr;
    bgeot::pstored_point_tab pint_points;
    std::vector<scalar_type> int_coeffs;
    std::vector<size_type> repartition;
    
    // index 0 : points for volumic integration, index > 0 : points for faces
    std::vector<PT_TAB> pt_to_store; 
    bool valid;
    bool built_on_the_fly;
    
  public :
    
    /// Dimension of reference convex.
    dim_type dim(void) const { return cvr->structure()->dim(); }
    size_type nb_points(void) const { return int_coeffs.size(); }
    /// Number of integration nodes on the reference element.
    size_type nb_points_on_convex(void) const { return repartition[0]; }
    /// Number of integration nodes on the face f of the reference element.
    size_type nb_points_on_face(short_type f) const
    { return repartition[f+1] - repartition[f]; }
    size_type ind_first_point_on_face(short_type f) const 
    { return repartition[f]; }
    /// Convenience method returning the number of faces of the reference convex
    short_type nb_convex_faces() const
    { return cvr->structure()->nb_faces(); /* == repartition.size() - 1;*/ }
    bool is_built_on_the_fly(void) const { return built_on_the_fly; }
    void set_built_on_the_fly(void)  { built_on_the_fly = true; }
    /// Structure of the reference element.
    bgeot::pconvex_structure structure(void) const
    { return basic_structure(cvr->structure()); }
    bgeot::pconvex_ref ref_convex(void) const { return cvr; }
    
    const std::vector<size_type> &repart(void) const { return repartition; }
    
    /// Gives an array of integration nodes.
    // const bgeot::stored_point_tab &integration_points(void) const
    // { return *(pint_points); }
    bgeot::pstored_point_tab pintegration_points(void) const
    { return pint_points; }
    /// Gives the integration node i on the reference element.
    const base_node &point(size_type i) const
    { return (*pint_points)[i]; }
    /// Gives the integration node i of the face f.
    const base_node &
    point_on_face(short_type f, size_type i) const 
    { return (*pint_points)[repartition[f] + i]; }
    /// Gives an array of the integration coefficients.
    const std::vector<scalar_type> &integration_coefficients(void) const
    { return int_coeffs; }
    /// Gives the integration coefficient corresponding to node i.
    scalar_type coeff(size_type i) const { return int_coeffs[i]; }
    /// Gives the integration coefficient corresponding to node i of face f.
    scalar_type coeff_on_face(short_type f, size_type i) const
    { return int_coeffs[repartition[f] + i]; }
    
    void add_point(const base_node &pt, scalar_type w,
                   short_type f = short_type(-1),
                   bool include_empty = false);
    void add_point_norepeat(const base_node &pt, scalar_type w,
                            short_type f=short_type(-1));
    void add_point_full_symmetric(base_node pt, scalar_type w);
    void add_method_on_face(pintegration_method ppi, short_type f);
    void valid_method(void);
    
    approx_integration(void) : valid(false), built_on_the_fly(false) { }
    approx_integration(bgeot::pconvex_ref cr)
      : cvr(cr), repartition(cr->structure()->nb_faces()+1),
        pt_to_store(cr->structure()->nb_faces()+1), valid(false),
        built_on_the_fly(false)
    { std::fill(repartition.begin(), repartition.end(), 0); }
    virtual ~approx_integration() {}
  };
 
  typedef std::shared_ptr<const approx_integration> papprox_integration;
 
  /**
     the list of main integration method types 
  */
  typedef enum { IM_APPROX, IM_EXACT, IM_NONE } integration_method_type;
 
  /**
     this structure is not intended to be used directly. It is built via
     the int_method_descriptor() function
  */
  class integration_method : virtual public dal::static_stored_object {
    ppoly_integration ppi; /* for exact integrations */
    papprox_integration pai; /* for approximate integrations (i.e. cubatures) */
    integration_method_type im_type;
    void remove() { pai =  papprox_integration(); ppi = ppoly_integration(); }
 
  public:
    integration_method_type type(void) const { return im_type; }
    const papprox_integration &approx_method(void) const { return pai; }
    const ppoly_integration &exact_method(void) const { return ppi; }
 
    void set_approx_method(papprox_integration paii)
    { remove(); pai = paii; im_type = IM_APPROX; }
    void set_exact_method(ppoly_integration ppii)
    { remove(); ppi = ppii; im_type = IM_EXACT; }
 
    bgeot::pstored_point_tab pintegration_points(void) const { 
      if (type() == IM_EXACT) {
        size_type n = ppi->structure()->dim();
        std::vector<base_node> spt(1); spt[0] = base_node(n);
        return store_point_tab(spt);
      }
      else if (type() == IM_APPROX)
        return pai->pintegration_points();
      else GMM_ASSERT1(false, "IM_NONE has no points");
    }
 
    // const bgeot::stored_point_tab &integration_points(void) const
    // { return *(pintegration_points()); }
 
    bgeot::pconvex_structure structure(void) const { 
      switch (type()) {
      case IM_EXACT: return ppi->structure();
      case IM_APPROX: return pai->structure();
      case IM_NONE: GMM_ASSERT1(false, "IM_NONE has no structure");
      default: GMM_ASSERT3(false, "");
      }
      return 0;
    }
 
    integration_method(ppoly_integration p) {
      DAL_STORED_OBJECT_DEBUG_CREATED(this, "Exact integration method");
      ppi = p; im_type = IM_EXACT;
    }
 
    integration_method(papprox_integration p) {
      DAL_STORED_OBJECT_DEBUG_CREATED(this, "Approximate integration method");
      pai = p; im_type = IM_APPROX;
    }
 
    integration_method() {
      DAL_STORED_OBJECT_DEBUG_CREATED(this, "Integration method");
      im_type = IM_NONE;
    }
    
    virtual ~integration_method()
    { DAL_STORED_OBJECT_DEBUG_DESTROYED(this, "Integration method"); }
  };
 
 
  /** Get an integration method from its name .
      @see @ref im_list 
      @param name the integration method name, for example "IM_TRIANGLE(6)"
      @param throw_if_not_found choose if an exception must be thrown
      when the integration method does not exist (if no exception, a
      null pointer is returned).
  */
  pintegration_method int_method_descriptor(std::string name,
                                            bool throw_if_not_found = true);
 
  /** Get the string name of an integration method .
   */
  std::string name_of_int_method(pintegration_method p);
  
  /**
     return an exact integration method for convex type handled by pgt.
     If pgt is not linear, classical_exact_im will fail.
  */
  pintegration_method classical_exact_im(bgeot::pgeometric_trans pgt);
  /**
     try to find an approximate integration method for the geometric
     transformation pgt which is able to integrate exactly polynomials
     of degree <= "degree". It may return a higher order integration
     method if no method match the exact degree.
  */
  pintegration_method classical_approx_im(bgeot::pgeometric_trans pgt, dim_type degree);
 
  /// return IM_EXACT_SIMPLEX(n)
  pintegration_method exact_simplex_im(size_type n);
  /// return IM_EXACT_PARALLELEPIPED(n)
  pintegration_method exact_parallelepiped_im(size_type n);
  /// return IM_EXACT_PRISM(n)
  pintegration_method exact_prism_im(size_type n);
  /// use classical_exact_im instead.
  pintegration_method exact_classical_im(bgeot::pgeometric_trans pgt) IS_DEPRECATED;
  /// return IM_NONE
  pintegration_method im_none(void);
 
 
  class mesh_im;
  papprox_integration composite_approx_int_method(const bgeot::mesh_precomposite &mp, 
                                                  const mesh_im &mf,
                                                  bgeot::pconvex_ref cr);
 
  /* try to integrate all monomials up to order 'order' and return the 
     max. error */
  scalar_type test_integration_error(papprox_integration pim, dim_type order);
 
  papprox_integration get_approx_im_or_fail(pintegration_method pim);
 
  /* Function allowing the add of an integration method outwards
     of getfem_integration.cc */
  
  typedef dal::naming_system<integration_method>::param_list im_param_list;
 
  void add_integration_name(std::string name,
                            dal::naming_system<integration_method>::pfunction f);
 
}  /* end of namespace getfem.                                            */
 
 
#endif /* BGEOT_INTEGRATION_H__                                           */