  Coordinate exchange (CEXCH) is a popular algorithm for generating exact
optimal experimental designs. The authors of CEXCH advocated for a highly
greedy implementation - one that exchanges and optimizes single element
coordinates of the design matrix. We revisit the effect of greediness on CEXCHs
efficacy for generating highly efficient designs. We implement the
single-element CEXCH (most greedy), a design-row (medium greedy) optimization
exchange, and particle swarm optimization (PSO; least greedy) on 21 exact
response surface design scenarios, under the $D$- and $I-$criterion, which have
well-known optimal designs that have been reproduced by several researchers. We
found essentially no difference in performance of the most greedy CEXCH and the
medium greedy CEXCH. PSO did exhibit better efficacy for generating $D$-optimal
designs, and for most $I$-optimal designs than CEXCH, but not to a strong
degree under our parametrization. This work suggests that further investigation
of the greediness dimension and its effect on CEXCH efficacy on a wider suite
of models and criterion is warranted.
