message: Update convergence criterion docs.
diff: @@ -121,7 +121,8 @@ protected:
  /** @name Reporting
  These options control the internal reporting behavior into ::mfem::out
  - and ::mfem::err of the iterative solvers. */
  + and ::mfem::err of the iterative solvers.
  + */
  ///@{
  /** @brief Legacy print level definition, which is left for compatibility
  @@ -146,17 +147,27 @@ protected:
  /** @name Convergence
  @brief Termination criteria for the iterative solvers.
  - @a X denotes the space in which the norm is measured, whose choice
  - depends on the specific iterative solver. */
  + @details While the convergence criterion is solver specific, most of the
  + provided iterative solvers use one of the following criterions
  +
  + \f$ ||r||_X \leq tol_{rel}||r_0||_X \f$,
  +
  + \f$ ||r||_X \leq tol_{abs} \f$,
  +
  + \f$ ||r||_X \leq \max\{ tol_{abs}, tol_{rel} ||r_0||_X \} \f$,
  +
  + where X denotes the space in which the norm is measured. The choice of
  + X depends on the specific iterative solver.
  + */
  ///@{
  /// Limit for the number of iterations the solver is allowed to do
  int max_iter;
  - /// Convergence criterion: \f$ ||r||_X \leq rel_{tol}||r_0||_X \f$
  + /// Relative tolerance.
  double rel_tol;
  - /// Convergence criterion: \f$ ||r||_X \leq abs_{tol} \f$
  + /// Absolute tolerance.
  double abs_tol;
  ///@}
  