Multi-Spin Coding of the Monte Carlo Simulation of the Three-State   Random Potts Model and the Block-Spin Transformation
  The multi-spin coding of the Monte Carlo simulation of the three-state Potts model on the simple cubic lattice is presented. The ferromagnetic (F) model, the antiferromagnetic (AF) model, and the random mixture of the F and AF couplings are treated. The multi-spin coding technique is also applied to the block-spin transformation. The block-spin transformation of the F Potts model is simply realized by the majority rule, whereas the AF three-state Potts model is transformed to the block spin having a six-fold symmetry. 
Macoto Kikuchi and Yutaka Okabe