fix_modify AtC control <physics_type> <solution_parameter>
fix_modify AtC transfer <physics_type> control max_iterations <max_iterations>
fix_modify AtC transfer <physics_type> control tolerance <tolerance> 
 fix_modify AtC control thermal max_iterations 10  
  fix_modify AtC control momentum tolerance 1.e-5  
 
Sets the numerical parameters for the matrix solvers used in the specified control algorithm. Many solution approaches require iterative solvers, and these methods enable users to provide the maximum number of iterations and the relative tolerance.
only for be used with specific controllers : thermal, momentum 
 They are ignored if a lumped solution is requested 
max_iterations is the number of rows in the matrix
 tolerance is 1.e-10 
 1.6.1
 1.6.1