<chapter name="Random-Number Seed"> <h2>Random-Number Seed</h2> The seed of the random number generator can be set as follows: <flag name="Random:setSeed" default="off"> Indicates whether a user-set seed should be used every time the <code>Pythia::init</code> routine is called. If off, the random number generator is initialized with its default seed at the beginning of the run, and never again. If on, each new <code>Pythia::init</code> call (should several be made in the same run) results in the random number being re-initialized, thereby possibly starting over with the same sequence, if you do not watch out. </flag> <modeopen name="Random:seed" default="-1" max="900000000"> The seed to be used, if <code>setSeed</code> is on.<br/> A negative value gives the default seed,<br/> a value 0 gives a random seed based on the time, and<br/> a value between 1 and 900,000,000 a unique different random number sequence. </modeopen> <p/> For more on random numbers see <aloc href="RandomNumbers">here</aloc>. This includes methods to save and restore the state of the generator, and some preprogrammed methods to generate non-uniform random numbers. </chapter> <!-- Copyright (C) 2014 Torbjorn Sjostrand -->