One of the notions you encounter in graph search algorithms is optimality
. You should consider that here optimality is just about the algorithm and not about the goal. Meaning that, if an algorithm is optimal it should return the minimum cost
solution.
Now, if you want to optimize something it's completely a different problem. In this case the quality of the solution is of most importance not the way you achieve it.
Algorithms like Genetic Algorithms, PSO, ... and many more optimization methods exists to address this issue.
BTW, sometimes we combine a graph search method like A* with an optimization algorithm to gain better results from the optimization algorithm.
Note: The term Graph Optimization
is not related to the topic Graph Search
that I think is your main topic according to your question.