1. A computer-implemented method of optimizing operation of a pipeline system, comprising: executing instructions on one or more computer processors to perform operations, comprising: a) reading input data, wherein the input data describes the pipeline system; b) generating a population of solutions, wherein each solution in the population specifies a feasible operational state for the pipeline system; c) evaluating an expected performance of each solution in the population and sorting the solutions in the population according to the evaluations; d) performing a genetic algorithm optimization process on the population of solutions until a termination condition specified by the input data is satisfied, whereby a plurality of optimized production solutions is generated; e) after the genetic algorithm optimization process is performed, selecting an optimized production solution from the plurality of optimized production solutions, wherein the selected optimized production solution has a highest evaluation, relative to the evaluations of other solutions in the population; and f) generating an optimized pressure solution specifying an output pressure for one or more delivery points of the pipeline system and an input pressure for one or more production nodes of the pipeline system, for the selected optimized production solution, using a direct pressure optimization process to change pressures of some pipeline elements, wherein the direct pressure optimization is performed by: calculating flows thorough a plurality of elements and nodes of the pipeline system; determining and propagating pressures at the plurality of nodes; generating a pressure dependency graph and using it to compute generalized pressure gap and minimum pressure for each sub network; reducing pressures of high pressure nodes where possible; propagating the pressures through the nodes of each sub network; and recalculating at least one unknown parameter of the elements of each sub network.