The Lumped Step node () is available when using the Segregated attribute node. This step is intended for speeding up the computation of any L2-projections, stemming from the identity operator, appearing as single physics interface within a multiphysics problem. Using the lumped step approximates the Jacobian matrix resulting from finite element discretization when solving the linear system for the unknown field variables. The approximation consists of replacing the Jacobian by a diagonal matrix with row sums. In doing so, take care to ensure that the resulting approximate Jacobian is invertible (nonsingular).