CPU Computing 15
the set of k-tuples of real numbers is IR
k
, n and d are positive integers, m is
a nonnegative integer (if zero, then Y = C), and C is a discrete space that is
referred to as the combinatorial portion of the output.
A typical example is the problem of computing the convex hull of a finite
set of points in two dimensions. In the definition, d = 2, which is the dimension
of the space containing the points, n is the number of points in the set, and
m = 0. The input points are indexed with integers 1 through n,andC is the
set of all ordered subsets of {1,...,n}. The output of the convex hull algorithm
is an element of C,say,{i
1
,...,i
q
}, which represents the ordered vertices of
the convex polygon that is the convex hull boundary; mathematically ...