Problems / theoretical-computer-science
theoretical-computer-science / Approximate counting and sampling (FPRAS, Markov chains)
Polynomial-time approximate counting and uniform sampling of contingency tables with arbitrary margins
FPRAS manuscript: one randomized algorithm counts nonnegative integer matrices with prescribed row sums, column sums and entry bounds bij (zeros allowed) within relative error ε with probability 1−δ, using unbiased bits and a polynomial bound in the input length, ε−1 and logδ−1 on every execution. Sampling manuscript: for ordinary tables, an almost-uniform sampler (TV error 2−k) in worst-case polynomial bit time and an exactly uniform sampler in expected polynomial bit time in m,n,log(N+1). Exponents are deliberately large; the results are complexity classifications, not practical algorithms, and the exact sampler is polynomial only in expectation.