  The Quasi-Steady State Approximation (QSSA) can be an effective tool for
reducing the size and stiffness of chemical mechanisms for implementation in
computational reacting flow solvers. However, for many applications, stiffness
remains, and the resulting model requires implicit methods for efficient time
integration. In this paper, we outline an approach to formulating the QSSA
reduction that is coupled with a strategy to generate C++ source code to
evaluate the net species production rate, and the chemical Jacobian. The
code-generation component employs a symbolic approach enabling a simple and
effective strategy to analytically compute the chemical Jacobian. For
computational tractability, the symbolic approach needs to be paired with
common subexpression elimination which can negatively affect memory usage.
Several solutions are outlined and successfully tested on a 3D multipulse
ignition problem, thus allowing portable application across a chemical model
sizes and GPU capabilities. The implementation of the proposed method is
available at https://github.com/AMReX-Combustion/PelePhysics under an
open-source license.
