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Although significantly larger programs must be used to make conclusive statements about performance , these programs are sufficiently complex and varied at the basic block level to form a starting point for experimentation . Aquifer systems are often complex . The issues are deeply complex and not amenable to simple solutions . This is done because software systems are often complex and it is impossible to comprehend them in their entirety . However , discrimination complaints are often complex , sensitive and potentially volatile . " Previously we looked at small areas and used that information to make guesses about the large area , to extrapolate to the big area , and that does n't work very well when things are really complex and so then we shifted to say , really , the complexity is what 's interesting and important , " reported Peters . However , these systems are often complex and expensive to manage .