1. A solver method, comprising: creating an ordered list of tasks involving objects and relationships between the objects to be simulated in a computer; simulating, in the computer, the objects and relationships by traversing the list of tasks and passing the tasks to corresponding objects and relationships; and repeating the traversing until a time for an end of the simulation is reached, wherein each object and relationship comprises operations of a pre-solving operation, pre-iteration operation, a solve operation, a post iteration operation and a post solve operation, each of the operations having tasks to be performed in an order and said creating comprises each object and relationship assigning an order number to each of the corresponding tasks.