VectorType solve(const MatrixType & matrix, VectorType const & rhs, cg_tag const & tag, PreconditionerType const & precond)
{
typedef typename VectorType::value_type ScalarType;
typedef typename viennacl::tools::CPU_SCALAR_TYPE_DEDUCER<ScalarType>::ResultType CPU_ScalarType;
VectorType result(rhs.size());
result.clear();
VectorType residual = rhs;
VectorType tmp(rhs.size());
VectorType z = rhs;
precond.apply(z);
VectorType p = z;
ScalarType ip_rr = viennacl::linalg::inner_prod(residual, z);
ScalarType alpha;
ScalarType new_ip_rr = 0;
ScalarType beta;
ScalarType norm_rhs = ip_rr;
for (unsigned int i = 0; i < tag.iterations(); ++i)
{
tag.iters(i+1);
tmp = viennacl::linalg::prod(matrix, p);
alpha = ip_rr / viennacl::linalg::inner_prod(tmp, p);
result += alpha * p;
residual -= alpha * tmp;
z = residual;
precond.apply(z);
new_ip_rr = viennacl::linalg::inner_prod(residual, z);
if (std::fabs(new_ip_rr / norm_rhs) < tag.tolerance() * tag.tolerance()) //squared norms involved here
break;
beta = new_ip_rr / ip_rr;
ip_rr = new_ip_rr;
p = z + beta*p;
}
//store last error estimate:
tag.error(sqrt(std::fabs(new_ip_rr / norm_rhs)));
return result;
}
VectorType solve(const MatrixType & matrix, VectorType const & rhs, cg_tag const & tag)
{
typedef typename VectorType::value_type ScalarType;
VectorType result(rhs.size());
result.clear();
VectorType residual = rhs;
VectorType p = rhs;
VectorType tmp(rhs.size());
ScalarType ip_rr = viennacl::linalg::inner_prod(rhs,rhs);
ScalarType alpha;
ScalarType new_ip_rr = 0;
ScalarType beta;
ScalarType norm_rhs = ip_rr;
//std::cout << "Starting CG solver... " << std::endl;
for (unsigned int i = 0; i < tag.iterations(); ++i)
{
tag.iters(i+1);
tmp = viennacl::linalg::prod(matrix, p);
alpha = ip_rr / viennacl::linalg::inner_prod(tmp, p);
result += alpha * p;
residual -= alpha * tmp;
new_ip_rr = viennacl::linalg::inner_prod(residual,residual);
if (new_ip_rr / norm_rhs < tag.tolerance() * tag.tolerance())//squared norms involved here
break;
beta = new_ip_rr / ip_rr;
ip_rr = new_ip_rr;
p = residual + beta*p;
}
//store last error estimate:
tag.error(sqrt(new_ip_rr / norm_rhs));
return result;
}
