=== Programming Details ===
Topmost level solver computations are concentrated in s__solve.cc file in 
 SIM::solve(...) 
inside it main important steps:
 do { 
assume we have some value of unknowns: X_c
calculate model parameters
   evaluate models; 
load matrices (Jacobian J and vector FG)
note, that dumping is implemented duing matrix & vector loading process. 
   load_marix(); 
solve equations and obtan new poin X_n
   solve_equations(); 
until equations will converge or iteration limit will not be acieved
  } while ( ! converged && ! _sim-> exceeds_iteration_limit(it1));