WHAT OPTIMIZERS DO

Optimizers exist to find the best possible solution to a problem.
What is meant by the best possible solution to a problem? Before attempting to define that phrase, let us first consider what constitutes a solution.
In trading, a solution is a particular set of trading rules and perhaps system parameters, All trading systems have at least two males (an entry rule and an exit rule), and most have one or more parameters. Rules express the logic of the trading system, and generally appear as “if-then” clauses in whatever language the trading system has been written. Parameters determine the behavior of the logic expressed in the rules;
they can include lengths of moving averages, connection weights in neural networks, thresholds used in comparisons, values that determine placements for stops and profit targets, and other similar items. The simple moving-average crossover system, used in the previous chapter to illustrate various trading simulators, had two rules:
one for the buy order and one for the sell order. It also had a single parameter, the length of the moving average. Rules and parameters completely define a trading system
and determine its performance.