Before revision: We present a Monte Carlo algorithm that allows efficient and unbiased sampling of polymer melts consisting of two chains of equal length that jointly visit all the sites of a cubic lattice  .
After revision: We present a Monte Carlo algorithm that allows efficient and unbiased sampling of polymer melts consisting of two chains of equal length that jointly visit all the sites of a cubic lattice with rod geometry L x L x rL and non-periodic (hard wall) boundary conditions .