As for the transient analysis, he typical algorithem of hspice is trap(trapezoidal), which usually is the fastest and most accurate algorithem. But some times, it may cause the problem of convergence, then, you can use another algorithem--GEAR, by writing .option method=gear. Usually, the circuit which doesn't converge in TRAP algorithem may converge using GEAR. However, the doc of hpsice said that some circuits with high nonlinearity will need very long time in GEAR, I havent't try it. Also, the speed of convergence maybe affected by some setting, like accurate, and so on.