@Stefan Schippers, how can we run simulation parallelly using multiple cores? I tried adding "set num_threads= 4" in .spiceinit file and set env variable OMP_NUM_THREADS= 4 . It runs parallelly and works well for xschem spice netlist and post layout spice simulation without parasitics extraction. A strange issue observerd:-On extracting parasitics and running the spice simulation, it does not run the simulation parallelly. What can be the reason for such behavior??

@Deepak I don't know why this happens, however consider that ngspice is not a true parallel solver. Only the device equation calculations can be assigned to multiple cores, however the solver that gets the solution of a set of multiple linearized equations (a sparse linear system) is one process and can not be split. For parallel execution consider using Xyce (the parallel Xyce version) and using OpenMP, but i have no experience on this.

okay Thanks @Stefan Schippers. Also is xyce simulator compatible with ngspice netlist(.spice file)?

@Deepak yes Xyce is compatible, reads almost all model files, the simulator commands are however different (specifically commands to save simulation data) . See the Xyce reference manual.

okay thank you