[paper] Vectorizing Device Model Evaluation in Ngspice

Vectorizing Device Model Evaluation in Ngspice circuit simulator

Florian Ballenegger, Anamosic Ballenegger Design

Preprint July 2020

Abstract: A method improving the execution speed of electrical circuit simulation using vector processing is proposed. The BSIM3V32 semi-conductor device model for the open-source Ngspice simulator has been re-written for evaluating multiple device instances of the same model at once using Single Instruction Multiple Data (SIMD) processor instructions. While parallel evaluation of device model was already available using multiprocessing, the proposed method can achieve the same speed-up using less processor resources, thus allowing to do more parallel independent simulations for statistical analysis.

In Conclusion: Only the BSIM3V32 device model was modified to use vector processing. Other device models would of course also benefit from the proposed method. In particular interest would be the EKV model https://github.com/ekv26/model, as the calculations in this symmetric model are more linear with fewer conditional branches and could be vectorized more efficently.  The source code of the modified BSIM3V3 model is available at https://www.anamosic.com/pages/ngspice.html