FlexPDE version 7 is almost totally backward-compatible with version 6.

However, we have made a few changes:

FEM Basis

•Version 7 now uses a hierarchical basis system.  Higher order components of the interpolation are now the coefficients of higher order terms in the polynomial approximation, not additional nodal values.  As a result, the “Nodes” report in the Status panel is not directly comparable to the report in version 6.  The new "DOF" (degrees of freedom) report in version 7 is directly comparable to the version 6 "Nodes" report.

•Cubic basis is now the default.  To replicate the behavior of version 6, you must either specify “quadratic” in the Select section, or use the preference panel to default to order=2.  The cubic model will run somewhat longer than a quadratic model on the same mesh.  However, the cubic model can return accurate results on a smaller mesh than the quadratic model.  Actual results will be problem dependent.

File Consolidation

•Version 7 by default creates a subdirectory (<problem name>_output) for each script that is run, and into which all the associated output files are written (this default can be changed in the Preferences control).  Scripts that TRANSFER files from other runs need to provide the proper path to find the appropriate import files.

Solution Controls

•Error estimation algorithms are somewhat different, and may result in different behavior than with previous versions.  Our goal is to make the behavior consistent across versions, but this is not always possible for all problems.

Reserved Names

•In previous versions, the names LAMBDA and MODE were activated only in eigenvalue problems.  In version 7, they are always reserved and can no longer be used as user-defined values.  See the list of Reserved Words for other changes.