  This paper presents a method for computing a finite-blocklength converse for
the rate of fixed-length codes with feedback used on discrete memoryless
channels (DMCs). The new converse is expressed in terms of a stochastic control
problem whose solution can be efficiently computed using dynamic programming
and Fourier methods. For channels such as the binary symmetric channel (BSC)
and binary erasure channel (BEC), the accuracy of the proposed converse is
similar to that of existing special-purpose converse bounds, but the new
converse technique can be applied to arbitrary DMCs. We provide example
applications of the new converse technique to the binary asymmetric channel
(BAC) and the quantized amplitude-constrained AWGN channel.
