I hope that master/solave assignment rules are clear at this point, but it might be good to remind them just in case: Selection master and slave in contact
Or made rigid with RB constraints, as I suggested above.
CalculiX doesn’t have such a switch, but in the log you can see messages like this:
Solving the system of equations using the symmetric pardiso solver.
or:
Solving the system of equations using the unsymmetric pardiso solver.
In fact, it’s recommended to use unsymm=yes in Abaqus also for lower friction coefficients and sometimes even when there’s no friction.