/// Constructor takes matrix reference
explicit diagonal(const Matrix& A) : inv_diag(num_rows(A))
{
mtl::vampir_trace<5050> tracer;
MTL_THROW_IF(num_rows(A) != num_cols(A), mtl::matrix_not_square());
using math::reciprocal;
for (size_type i= 0; i < num_rows(A); ++i)
inv_diag[i]= reciprocal(A[i][i]);
}
// Undefined if matrix is not symmetric
void factorize(const Matrix& A, mtl::tag::sparse)
{
using namespace mtl; using namespace mtl::tag; using mtl::traits::range_generator;
using math::reciprocal; using mtl::matrix::upper;
typedef typename range_generator<row, U_type>::type cur_type;
typedef typename range_generator<nz, cur_type>::type icur_type;
MTL_THROW_IF(num_rows(A) != num_cols(A), mtl::matrix_not_square());
U= upper(A); crop(U);
U_type L(lower(A)); // needed to find non-zeros in column
typename mtl::traits::col<U_type>::type col(U), col_l(L);
typename mtl::traits::value<U_type>::type value(U);
cur_type kc= begin<row>(U), kend= end<row>(U);
for (size_type k= 0; kc != kend; ++kc, ++k) {
icur_type ic= begin<nz>(kc), iend= end<nz>(kc);
MTL_DEBUG_THROW_IF(col(*ic) != k, mtl::missing_diagonal());
// U[k][k]= 1.0 / sqrt(U[k][k]);
value_type inv_dia= reciprocal(sqrt(value(*ic)));
value(*ic, inv_dia);
icur_type jbegin= ++ic;
for (; ic != iend; ++ic) {
// U[k][i] *= U[k][k]
value_type d= value(*ic) * inv_dia;
value(*ic, d);
size_type i= col(*ic);
// find non-zeros U[j][i] below U[k][i] for j in (k, i]
// 1. Go to ith row in L (== ith column in U)
cur_type irow= begin<row>(L); irow+= i;
// 2. Find nonzeros with col() in (k, i]
icur_type jc= begin<nz>(irow), jend= end<nz>(irow);
while (col_l(*jc) <= k) ++jc;
while (col_l(*--jend) > i);
++jend;
for (; jc != jend; ++jc) {
size_type j= col_l(*jc);
U.lvalue(j, i)-= d * U[k][j];
}
// std::cout << "U after eliminating U[" << i << "][" << k << "] =\n" << U;
}
}
}
void factorize(const Matrix& A, L_type& L, U_type& U, boost::mpl::true_)
{
using namespace mtl; using namespace mtl::tag; using mtl::traits::range_generator;
using math::reciprocal;
MTL_THROW_IF(num_rows(A) != num_cols(A), mtl::matrix_not_square());
mtl::vampir_trace<5038> tracer;
typedef typename mtl::Collection<Matrix>::value_type value_type;
typedef typename mtl::Collection<Matrix>::size_type size_type;
typedef mtl::mat::parameters<mtl::row_major, mtl::index::c_index, mtl::non_fixed::dimensions, false, size_type> para;
typedef mtl::mat::compressed2D<value_type, para> LU_type;
LU_type LU(A);
typedef typename range_generator<row, LU_type>::type cur_type;
typedef typename range_generator<nz, cur_type>::type icur_type;
typename mtl::traits::col<LU_type>::type col(LU);
typename mtl::traits::value<LU_type>::type value(LU);
mtl::vec::dense_vector<value_type, mtl::vec::parameters<> > inv_dia(num_rows(A));
cur_type ic= begin<row>(LU), iend= end<row>(LU);
for (size_type i= 0; ic != iend; ++ic, ++i) {
for (icur_type kc= begin<nz>(ic), kend= end<nz>(ic); kc != kend; ++kc) {
size_type k= col(*kc);
if (k == i) break;
value_type aik= value(*kc) * inv_dia[k];
value(*kc, aik);
for (icur_type jc= kc + 1; jc != kend; ++jc)
value(*jc, value(*jc) - aik * LU[k][col(*jc)]);
// std::cout << "LU after eliminating A[" << i << "][" << k << "] =\n" << LU;
}
inv_dia[i]= reciprocal(LU[i][i]);
}
invert_diagonal(LU);
L= strict_lower(LU);
U= upper(LU);
}
