The simultaneous perturbation stochastic approximation (SPSA) algorith
m has proven very effective for difficult multivariate optimization pr
oblems where it is not possible to obtain direct gradient information.
As discussed to date, SPSA is based on a highly efficient gradient ap
proximation requiring only two measurements of the loss function indep
endent of the number of parameters being estimated. This note presents
a form of SPSA that requires only one function measurement (for any d
imension). Theory is presented that identifies the class of problems f
or which this one-measurement form will be asymptotically superior to
the standard two-measurement form. (C) 1997 Elsevier Science Ltd.