Field Means and Variances

The function ` meansvars()` calculates the means and variances
of all output fields. The means are simply the sum of the field at
each gridpoint divided by the total number of gridpoints. The variance
is calculated as

(5.1) |

The ` meansvars()` function is also where the program checks
for runaway field behavior. If the evolution becomes unstable (usually
due to using too large a time step) the fields can start growing
exponentially. In this case it will generally not take many time steps
before the field values exceed the maximum storage possible on the
computer, and the values are then simply stored as non-numerical. The
program checks for such an occurence by verifying that the average is
numerical. If this test fails then the program will print a warning
message, call

Note that if you choose not to output means and variances then this error checking won't occur. In practice, though, it is almost invariably useful to have these quantities for at least one of the output fields, so we recommend leaving this output field on for all runs.

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This documentation was generated on 2008-01-21