Given a graph with edges colored Red and Blue, we wish to sample and approximately count the number of perfect matchings with exactly k Red edges. We study a Markov chain on the space of all matchings of a graph that favors matchings with k Red edges. We show that it is rapidly mixing using non-traditional canonical paths that can backtrack, based on an algorithm for a simple combinatorial problem. We show that this chain can be used to sample dimer configurations on a 2-dimensional toroidal region with k Red edges. 							
						
							
					 															
					Nayantara Bhatnagar, Dana Randall, Vijay V. Vazira