move code to arbirate num_chains to use into own function
move code to arbirate num_chains to use into own function

mit-probabilistic-computing-project/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,fivejjs/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,probcomp/crosscat,probcomp/crosscat,fivejjs/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat