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                Department of Mathematical Sciences
                   The Johns Hopkins University

                             SEMINAR

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Keith N. Crank                                         April 18, 2002
Division of Mathematical Sciences                      304 Whitehall Hall 
National Science Foundation                            Refreshments: 3:30 PM 
                                                       Seminar: 4:00 PM 

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        INTERRUPTIBLE EXACT SAMPLING IN THE PASSIVE CASE


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                               ABSTRACT

We establish, for various scenarios, whether or not interruptible exact 
stationary sampling is possible when a finite-state Markov chain can 
only be viewed passively.  In particular, we prove that such sampling 
is not possible using a single copy of the chain.  Such sampling is 
possible when enough copies of the chain are available, and we 
provide an algorithm that terminates with probability one.

This is joint work with Jim Fill.