Accessing right side vector

I am implementing mrdump command which dumps the right hand side matrix
values.The problem is when I try to access the right side
vector,i.e.,_sim->_i[i] it says Segmentation fault(core dumped).probably
that means _sim->_i does not exists when i am trying to reference it.I
tested this after doing a transient analysis.

-- 
Rishabh Yadav