google3/third_party/libigl/include/igl/harwell_boeing.cpp

// This file is part of libigl, a simple c++ geometry processing library.
// 
// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
// 
// This Source Code Form is subject to the terms of the Mozilla Public License 
// v. 2.0. If a copy of the MPL was not distributed with this file, You can 
// obtain one at http://mozilla.org/MPL/2.0/.
#include "harwell_boeing.h"

template <typename Scalar, typename Index>
IGL_INLINE void igl::harwell_boeing(
  const Eigen::SparseMatrix<Scalar> & A,
  int & num_rows,
  std::vector<Scalar> & V,
  std::vector<Index> & R,
  std::vector<Index> & C)
{
  num_rows = A.rows();
  int num_cols = A.cols();
  int nnz = A.nonZeros();
  V.resize(nnz);
  R.resize(nnz);
  C.resize(num_cols+1);

  // Assumes outersize is columns
  assert(A.cols() == A.outerSize());
  int column_pointer = 0;
  int i = 0;
  int k = 0;
  // Iterate over outside
  for(; k<A.outerSize(); ++k)
  {
    C[k] = column_pointer;
    // Iterate over inside
    for(typename Eigen::SparseMatrix<Scalar>::InnerIterator it (A,k); it; ++it)
    {
      V[i] = it.value();
      R[i] = it.row();
      i++;
      // Also increment column pointer
      column_pointer++; 
    }
  }
  // by convention C[num_cols] = nnz
  C[k] = column_pointer;
}

#ifdef IGL_STATIC_LIBRARY
// Explicit template instantiation
// generated by autoexplicit.sh
template void igl::harwell_boeing<double, int>(Eigen::SparseMatrix<double, 0, int> const&, int&, std::vector<double, std::allocator<double> >&, std::vector<int, std::allocator<int> >&, std::vector<int, std::allocator<int> >&);
#endif