Updating tnl-benchmark-linear-solvers: log iterations and residues

         throw std::runtime_error("solver did not converge");

   };

   benchmark.time( reset, performer, compute );

   // subclass BenchmarkResult to add extra columns to the benchmark

   // (iterations, preconditioned residue, true residue)

   struct MyBenchmarkResult : public BenchmarkResult

   {

      using HeaderElements = BenchmarkResult::HeaderElements;

      using RowElements = BenchmarkResult::RowElements;

   // TODO: add extra columns to the benchmark (iterations, preconditioned residue, true residue)

//   Vector r;

//   r.setLike( x );

//   matrix->vectorProduct( x, r );

//   r.addVector( b, 1.0, -1.0 );

//   const double trueResidue = r.lpNorm( 2.0 ) / b.lpNorm( 2.0 );

      Solver< Matrix >& solver;

      const SharedPointer< Matrix >& matrix;

      const Vector& x;

      const Vector& b;

//    std::cout << "Converged: " << solver.checkConvergence() << ", iterations = " << solver.getIterations() << ", residue = " << solver.getResidue() << "    " << std::endl;

//    std::cout << "Mean time: " << time / loops << " seconds." << std::endl;

//    std::cout << outputPrefix

//              << "converged: "   << std::setw( 5) << std::boolalpha << ( ! std::isnan(solver.getResidue()) && solver.getResidue() < solver.getConvergenceResidue() ) << "   "

//              << "iterations = " << std::setw( 4) << solver.getIterations() << "   "

//              << "preconditioned residue = " << std::setw(10) << solver.getResidue() << "   "

//              << "true residue = " << std::setw(10) << trueResidue << "   "

//              << "mean time = "  << std::setw( 9) << time / loops << " seconds." << std::endl;

      MyBenchmarkResult( Solver< Matrix >& solver,

                         const SharedPointer< Matrix >& matrix,

                         const Vector& x,

                         const Vector& b )

      : solver(solver), matrix(matrix), x(x), b(b)

      {}

      virtual HeaderElements getTableHeader() const override

      {

         return HeaderElements({"time", "speedup", "converged", "iterations", "residue_precond", "residue_true"});

      }

      virtual RowElements getRowElements() const override

      {

         const bool converged = ! std::isnan(solver.getResidue()) && solver.getResidue() < solver.getConvergenceResidue();

         const long iterations = solver.getIterations();

         const double residue_precond = solver.getResidue();

         Vector r;

         r.setLike( x );

         matrix->vectorProduct( x, r );

         r.addVector( b, 1.0, -1.0 );

         const double residue_true = r.lpNorm( 2.0 ) / b.lpNorm( 2.0 );

         return RowElements({ time, speedup, (double) converged, (double) iterations,

                              residue_precond, residue_true });

      }

   };

   MyBenchmarkResult benchmarkResult( solver, matrix, x, b );

   benchmark.time( reset, performer, compute, benchmarkResult );

}

#ifdef HAVE_ARMADILLO

                    const Vector& x0,

                    const Vector& b )

{

    using namespace TNL;

    // copy matrix into Armadillo's class

    // sp_mat is in CSC format

    arma::uvec _colptr( matrix->getRowPointers().getSize() );