1. A method for ordering multiple nodes underlying equations in a distributed sparse linear system, comprising: designating nodes that do not have a connection that crosses a partitioning interface as interior nodes; designating nodes that have a connection that crosses a partitioning interface as boundary nodes; designating no more than three codes to distinguish the boundary nodes; processing each boundary node using a computer processor by: assigning a first code to each boundary node representing a first boundary node, wherein each first boundary node connection cannot cross a partitioning interface to connect two first boundary nodes; assigning a second code to each boundary node representing a second boundary node, wherein each second boundary node connection cannot cross a partitioning interface to connect two second boundary nodes; and assigning a third code to each boundary node representing a third boundary node, wherein each third boundary node connection cannot cross a partitioning interface to connect an interior node.