ERRATUM

FlexPDE version 4 documentation contains an error in the Problem Descriptor Reference, chapter heading "The Sections of a Descriptor", subchapter "Variables".  The error is in the paragraph "The THRESHOLD Clause", where the word "lesser" is used where it should have said "greater".  This paragraph occurs on page 47 of the hardcopy Reference Manual.  The correct paragraph is as follows:

The THRESHOLD clause

An optional THRESHOLD clause may be associated with a variable name.
In most cases, the use of THRESHOLD is meaningful only in time-dependent problems with uniform initial values.

The THRESHOLD value determines the minimum value of the variable for which FlexPDE must try to maintain the requested ERRLIM accuracy. In other words, THRESHOLD defines the level at which the user begins to lose interest in the details of the solution.

Error estimates are scaled to the greater of the THRESHOLD value or the observed range of the variable, so the THRESHOLD value becomes meaningless once the observed variation of a variable in the problem domain exceeds the stated THRESHOLD.