Hi, I’d like to know what type of solver QSPICE uses. What is FASTMATH, and are there any other solvers available?
Does QSPICE include any stiff solvers?
I’m already familiar with the integration methods like Gear and Trapezoidal (which is the default), but it seems like there are fewer options compared to LTspice.
Option that related to solver are
Fastmath : Preferred 64 bits or 80 bits solver ( 1 : QSPICE64.exe or 0 : QSPICE80.exe ) [none]
MaxOrd : Integration method ( 1 : Backward Euler , 2 : Trapezoidal / Gear ) [2]
Method : Integration method ( Trapezoidal / Gear ) [Trap]
Feather : Damping Factor for Trapezoidal Integration [0]
Compare to LTspice
Fastmath is math precision, 80 bits solver uses more 80-bit math (long double) than 64 bits solver. In LTspice, it has an option “solver” to select normal or alt, alt is slower but more accurate, similar to fasmath but I don’t know if they are same thing.
MaxOrd and Method determines integration method : Backward Euler, Gear OR Trapezoidal. Compare to LTspice : LTspice had MaxOrd but not sure if it still available in latest version, and LTspice offers “Modified Trap” in method, but Mike no longer implement this in Qspice
Feather is a damping factor for Trap, which can be found in Hspice. No such option in LTspice.
In short, my understanding is that, as compare to LTspice, Qspice doesn’t offer “Modified Trap”.