Descent direction
In optimization, a descent direction is a vector that, in the sense below, moves us closer towards a local minimum
of our objective function
.
Suppose we are computing by an iterative method, such as line search. We define a descent direction
at the
th iterate to be any
such that
, where
denotes the inner product. The motivation for such an approach is that small steps along
guarantee that
is reduced, by Taylor's theorem.