For problems of the form M*y' = F(t,y) sets and gets the value of the constant mass matrix M.

For problems of the form M(t,y)*y' = F(t,y) sets and gets the value of the time-state dependent mass matrix function M(t,y).

The output function to be called by the ODE solver at each integration step. If this function returns true the solver continues with the next step, if it returns false the solver is halted.