Seeding the Random Number Generator

The random variations are created using a pseudo random number sequence. The sequence can be seeded such that it always produces the same sequence of numbers for a given seed. In Monte Carlo analysis, the random number generator is seeded with a new value at the start of each run and this seed value is displayed in the log file (see above). It is also possible to fix the first seed that is used using the SEED option. This makes it possible to repeat a run. To do this, note the seed value of the run of interest then add the line:

.OPTIONS SEED=seed_value

For example if you wanted to repeat run 2 in the above example you would add this line:

.OPTIONS SEED=1521158126

The first run of each Monte Carlo analysis will use the same random values as run 2 above. Note this assumes that only changes in values are made to the circuit. Any topology change will upset the sequence.