  This paper considers Gama-Nguyen-Regev's strategy [GNR10] for optimizing
pruning coefficients for lattice vector enumeration. We give a table of
optimized coefficients and proposes a faster method for computing
near-optimized coefficients for any parameters by interpolation.
  From the first version published in 2014, we inserted new Section 3.3 to
introduce our recent technique to compute approximations of enumeration cost
and success probability; both are completed in O(n^2) floating point operations
where n is the lattice dimension.
  For readers who are interested in this topic, we keep the descriptions of our
heuristic optimization method in Section 4 although they are outdated now.
