An algorithm for assembly of stiffness matrices into a compacted data structure

A data structure is described that stores only the non‐zero terms of the assembled stiffness matrix. This storage scheme results in considerable reduction in memory demand during the assembly phase of a finite element program. Therefore, larger matrices can be formed in the main memory of the computer. When secondary store must be used this approach reduces the I/O cost during the assembly stage. An algorithm is derived that starts with the element connectivity information and generates the compacted data structure. The element matrices are then assembled to form the stiffness matrix with this storage scheme. The assembly algorithm is described and a FORTRAN listing of the routines is presented. The reduction in storage is demonstrated with the aid of numerical examples.