basically you use GP as a last resort, when you don't have any knowledge of the actual problem space that would help you make better guesses from previous ones.

basically you use GP as a last resort, when you don't have any knowledge of the actual problem space that would help you make better guesses from previous ones. This is also usually the default situation, because often we really don't know anything about the problem space. Of course if you do know something about the problem space in the form of a gradient or probabilistic graph, and then you use those things & you won't be doing GP anymore.