1. In a computer system, a method of improving performance of a block diagram model using an optimization process, the method comprising: receiving a plurality of ranked performance objectives; determining with the optimization process in the computer system if a first portion of a block diagram model can operate with improved performance to satisfy the plurality of ranked performance objectives; providing a user with a first modification for operating the first portion of the block diagram model with the improved performance, the first modification involving constraining a value of an operational attribute of the first portion of the block diagram model, the first modification selected from a plurality of ranked possible modifications, the possible modifications being ranked based on complexities of making the possible modifications; and optimizing the first portion of the block diagram model in the computer system using the first modification.