dense_matrix_base_impl.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 
 
#ifndef LIBMESH_DENSE_MATRIX_BASE_IMPL_H
#define LIBMESH_DENSE_MATRIX_BASE_IMPL_H
 
// Local Includes
#include "libmesh/dense_matrix.h"
#include "libmesh/dense_vector_base.h"
#include "libmesh/dense_vector.h"
#include "libmesh/int_range.h"
 
// C++ includes
#include <iomanip> // for std::setw()
 
namespace libMesh
{
 
  template <typename T>
  DenseVector<T>
  DenseMatrixBase<T>::diagonal() const
  {
    DenseVector<T> ret(_m);
    for (decltype(_m) i = 0; i < _m; ++i)
      ret(i) = el(i, i);
    return ret;
  }
 
  template<typename T>
  void DenseMatrixBase<T>::multiply (DenseMatrixBase<T> & M1,
                                     const DenseMatrixBase<T> & M2,
                                     const DenseMatrixBase<T> & M3)
  {
    // Assertions to make sure we have been
    // passed matrices of the correct dimension.
    libmesh_assert_equal_to (M1.m(), M2.m());
    libmesh_assert_equal_to (M1.n(), M3.n());
    libmesh_assert_equal_to (M2.n(), M3.m());
 
    const unsigned int m_s = M2.m();
    const unsigned int p_s = M2.n();
    const unsigned int n_s = M1.n();
 
    // Do it this way because there is a
    // decent chance (at least for constraint matrices)
    // that M3(k,j) = 0. when right-multiplying.
    for (unsigned int k=0; k<p_s; k++)
      for (unsigned int j=0; j<n_s; j++)
        if (M3.el(k,j) != 0.)
          for (unsigned int i=0; i<m_s; i++)
            M1.el(i,j) += M2.el(i,k) * M3.el(k,j);
  }
 
 
 
  template<typename T>
  void DenseMatrixBase<T>::condense(const unsigned int iv,
                                    const unsigned int jv,
                                    const T val,
                                    DenseVectorBase<T> & rhs)
  {
    libmesh_assert_equal_to (this->_m, rhs.size());
    libmesh_assert_equal_to (iv, jv);
 
 
    // move the known value into the RHS
    // and zero the column
    for (auto i : make_range(this->m()))
      {
        rhs.el(i) -= this->el(i,jv)*val;
        this->el(i,jv) = 0.;
      }
 
    // zero the row
    for (auto j : make_range(this->n()))
      this->el(iv,j) = 0.;
 
    this->el(iv,jv) = 1.;
    rhs.el(iv) = val;
 
  }
 
 
  template<typename T>
  void DenseMatrixBase<T>::print_scientific (std::ostream & os, unsigned precision) const
  {
    // save the initial format flags
    std::ios_base::fmtflags os_flags = os.flags();
 
    // Print the matrix entries.
    for (auto i : make_range(this->m()))
      {
        for (auto j : make_range(this->n()))
          os << std::setw(15)
             << std::scientific
             << std::setprecision(precision)
             << this->el(i,j) << " ";
 
        os << std::endl;
      }
 
    // reset the original format flags
    os.flags(os_flags);
  }
 
 
 
  template<typename T>
  void DenseMatrixBase<T>::print (std::ostream & os) const
  {
    for (auto i : make_range(this->m()))
      {
        for (auto j : make_range(this->n()))
          os << std::setw(8)
             << this->el(i,j) << " ";
 
        os << std::endl;
      }
 
    return;
  }
 
 
 
}
 
#endif // LIBMESH_DENSE_MATRIX_BASE_IMPL_H