Version 4.2.15    6/4/05

• Corrects errors in Contact Resistance boundary conditions in 3D problems. (Adaptive mesh refinement must still be disabled in such problems.)
• Corrects a spurious error diagnostic computing 3D volume integrals over regions for which the Layer 1 compartment is VOID.

  Version 4.2.14    5/13/05

• Corrects innacurate results of TINTEGRAL when the problem start time is not zero.
• Diagnoses missing equations.
• Correctly reports "permission denied" errors on Linux.
• Corrects a syntax-highlighter crash if typed numeric exponents exceed machine range.
• Corrects faulty testing of jump boundaries.

  Version 4.2.13    4/23/05

• Supports .PG4 files over 2 GB in length.
• Corrects an error in the use of INTEGRALS in SCALAR equations (introduced in 4.2.12).
• Corrects an error in the use of nested function calls (parameterized definitions).
• Erases residual text shadows in the status window (on operating systems with text shadowing).
• Corrects an error that caused deletion of constant-length vectors in vector plots.
• Corrects an error reading license key files containing apostrophe (').
• Corrects an error in implementation of the ALIGN_MESH option that caused occasional deletion of surface faces..

  Version 4.2.12    3/30/05

• Corrects occasional mesh generation failures in complex 3D domains.
• Implements speedups in INTEGRALs, FITs and SAVEs.
• Corrects spurious error diagnostics involving CURL operator in 3D.
• PG4 files are now portable between Macintosh and Intel computers..

  Version 4.2.11    3/16/05

• Corrects the lack of timely recomputation of INTEGRAL (and SAVE and FIT) of arguments which are functions of time only.

  Version 4.2.10    3/13/05

• Corrects an error in distribution of vectors in vector plots.
• Corrects loss of history data in problems with STAGED geometry.
• MAC version: Corrects very slow drawing of filled plots.

  Version 4.2.9    2/11/05

• Modified memory management makes more effective use of fragmented memory space in very large problems.
• Corrects a memory leak in time-dependent problems in batch runs.
• Corrects an occasional crash in problems with STAGED geometry.
• MAC version: Corrects handling of "Stop Now" and "Pause".
• Linux version: Corrects handling of memory faults.

  Version 4.2.8    1/18/05

• Corrects an error in plotting and integrating on 3D extrusion surfaces adjoining VOID layers.
• Corrects an error in implementation of FEATUREPLOT selector in 3D.
• Corrects an error in the implementation of the TANGENTIAL operator in 3D.
• Corrects an error in the Help Keyword Index on Linux.

  Version 4.2.7    1/8/05

• Corrects an error that caused excessive unnecessary recomputation of SAVES, FITS and INTEGRALs, resulting in slow execution in some cases.
• Corrects an error that deleted plotted vectors when all vectors were of equal length.
• Corrects a busy wait when FlexPDE is paused.
• Corrects occasional mesh generation failures.

  Version 4.2.6    12/23/04

• Corrects an error in application of 3D sidewall boundary conditions with a Value condition in layer 1 and Natural conditions in upper layers. (This error was corrected in version 4.0.5, and reappeared in version 4.1.0.)
• Corrects an error that generated random contour lines in contour plots on uniform value data.
• Adds an initial mesh refinement pass in 3D problems with very thin layers of erratic thickness, where the ALIGN_MESH switch is active.

  Version 4.2.5    12/14/04

• Corrects an error that caused double application of internal surface sources.
• Corrects occasional failures in mesh generation.

  Version 4.2.4    11/17/04

• Corrects an error in nonlinear JUMP boundary conditions.
• Corrects an occasional failure in color selection in VECTOR plots.
• Diagnoses coordinate name conflicts.
• Limits error weighting in time-dependent problems to prevent overflow in extreme cases. (This has occurred occasionally as a result of unrestrained use of exponential functions in coefficients).
• New Technical note "Coordinate Scaling" and example problems "Scaled_Z.pde" and "Unscaled_Z.pde" in the "Samples | Misc | 3D_Domains" folder show how to scale layer thicknesses in extremely thin domains.

  Version 4.2.3    10/24/04

• Corrects a spurious "No More Data" report in Viewing PG4 files from time dependent problems with interspersed non-graphic export commands.
• Corrects a timestep control error in mixed time-dependent/steady-state systems with constraints.
• Corrects an error in forming unqualified (exterior boundary) surf_integrals in 3D problems with VOID regions.

  Version 4.2.2    10/16/04

• Corrects a mesh generation error in 3D problems with LIMITED REGIONS and merged extrusion surfaces..
• Corrects a mesh generation error in handling FIXED POINTS in 2D problems.

  Version 4.2.1    10/8/04

• Corrects an error in writing TABLE files in default mode (unformatted) when the domain is irregular and some table points fall outside the domain. (This error was introduced in version 4.1.0).
• Implements REPEAT clauses in HISTORY plots.

  Version 4.2.0    10/5/04

• Changes the grammar for construction of contact resistance boundaries. CONTACT(v) must now be used instead of NATURAL(v) for a discontinuous variable.  JUMP(v) is now legal in any computation on a boundary where '"v" has been given a CONTACT BC.
• Corrects errors in 3D mesh generation using SPLINE sidewalls.
• Changes the default behavior in nonlinear time-dependent problems to PREFER_STABILITY instead of the previous PREFER_SPEED.  This can cause problems to run longer than in previous versions, but we chose to err in the direction of safety.  The behavior of previous versions can be recovered by SELECT PREFER_SPEED.
• Produces a complexity summary of defined parameters.  The summary is written to the file <problem_name>.DBG in the problem folder.
• Corrects 3D mesh generation failures using EXCLUDE boundaries.
• Imposes a halt if the timestep drops below 1e-9 times the requested initial timestep.  If this halt occurs, you may have an inconsistent initial condition that is not resolvable by cutting the timestep, or you may have temporal discontinuities in your coefficients, or you may have merely requested an initial timestep that is much too large.
• Corrects an error in nonlinear iteration that caused slow execution when given initial values much larger than the true solution.
• Mesh refinement applied during the initial value phase of time dependent problems was previously permanent.  This refinement can now be un-refined at later times if the cell errors drop below the merge threshold.  This can speed up problems with strong curvature in initial conditions.
• NEUMANN, DNORMAL and DTANGENTIAL boundary condition specifications have been disabled, due to unreliable performance.  In most cases, an equivalent NATURAL BC can be substituted.

  Version 4.1.1    8/28/04

• Corrects erratic behavior of 2D mesh generator.
• Corrects an error in periodic boundary conditions in time-dependent problems.
• Implements time derivatives in Natural boundary conditions.
• Corrects erratic failure of Elevation plots in 3D problems.
• Corrects failure of JUMP boundary conditions at multiple-boundary joints.

  Version 4.1.0    8/16/04

• [4.1.0b]
• Corrects an error writing VTKLIN output.
• Adds an error diagnostic for negative input radii in 2D cylindrical geomerty.
• Corrects an omitted final position label in Elevation plots on boundaries.

• [4.1.0a]
• Corrects an error in writing the "<problem>.DBG" file. This file contains information previously written to "<home>|flexpde4.dbg".

• [4.1.0]

Continuing the work begun in version 4.0, we have substantially rewritten the plot generation facilities of FlexPDE. The first goal has been to maintain compatibility with previous versions, but enhancements can now follow using the improved code base.

In addition, version 4.1 introduces the following new features:

• Version 4.1 can now handle variables that are discontinuous at material interfaces. The implementation follows the concept of contact resistance, but it can be used for other purposes, including complete decoupling of variables between regions. This feature adds the reserved word JUMP to the syntax of boundary condition statements. JUMP represents the discontinuity in the chosen variable at the interface.
• 2D region boundaries can now use SPLINE interpolated segments. The syntax of SPLINE is identical to LINE, and all points in a chain of TO (,) TO (,).. will be linked together in a spline curve.
• VTK export format extends the family of available visualization tools to include the free VisIt package.

We have made the following improvements to existing facilities:

• FlexPDE begins the mesh generation process in 3D by creating 2D meshes on the extrusion surfaces. Previous versions had shortcomings in maintaining compatibility between nearby surfaces with substantially different feature sizes. This condition has been considerably improved in version 4.1, resulting in more stable mesh generation in 3D problems with scale size variations.
• The new plot generation facilities are better at handling 3D cutplane plots that coincide with mesh boundaries.
• The MOVIE mode in previous versions had a built-in half-second frame delay, which minimized flashing, but made the display very slow for scanning large files. We have added two VIEW controls: the LAST command jumps as quickly as possible to the end of the file, and the FRAME_DELAY command allows the user to select the frame delay.

The following example problems have been added:

• "Samples | Misc | Jumpbc2.pde" and "Samples | Misc | Jumpbc2t.pde" show the use of the JUMP statement for discontinuous variables in steady-state and time-dependent problems.
• "Samples | Misc | Spline_Bdry.pde" shows the use of the SPLINE boundary construction facility.

  Version 4.0.7    6/29/04

• [4.0.7a]
• Corrects an "Incomplete Bounding Mesh" error with imbedded circular rings bounding limited regions.
• Corrects an error in assigning sidewall faces to integral operators in 3D problems with limited regions.
• Adds "Last Plot" command for viewing .PG4 files

• [4.0.7]
• Corrects an overzealous diagnostic that blocked periodic boundary conditions in multi-variable problems.
• Corrects a bug that generated "Incomplete Bounding Mesh" errors in some 3D problems.
• Displays 2D 'Domain' plots before diagnostics to aid visualization.
• Corrects a plotting error in 3D display of flat 2D surface meshes.
•  

  Version 4.0.5    3/24/04

• [4.0.5a]
• Corrects an error that propagated layer 1 boundary conditions into all layers.
• [4.0.5]
• 3D mesh generator improvements for thin shells.
•  

  Version 4.0.4    3/17/04

• Further stabilization of 3D mesh generator.
• Various bug fixes

  Version 4.0.3    3/4/04

• [4.0.3a]
• Corrects coloring error on 3D grid plots.

• [4.0.3]
• More robust mesh generator.
• New 3D domain review graphic under "Domain" button.
• New 3D bounding shell mesh display for each region/layer under "Domain" button.
• Corrected plot centering for off-origin domains.
• Additional domain error diagnostics.
• Corrected failure with cubic basis.

Version 4.0.2    2/24/04

• Significant modifications in the 3D mesh generator. See Tech Note "3D Mesh Generation in Version 4.0"for a discussion of the mesh generation process.  
• Modified interpretation of the ASPECT control. See Tech Note "Mesh Density Controls in Version 4.0.2".  
• Corrects errors in the interpretation and application of MESH_SPACING controls, and makes the syntax equivalent to boundary conditions. See Tech Note "Mesh Density Controls in Version 4.0.2".  
  
• Corrects an error in mesh generation of FEATURES in 2D domains.
• Corrects the distribution and spacing of arrow fields in ZOOMed VECTOR plots.
• Corrects a memory protection fault in SUMMARY PLOT processing.
• Corrects a memory protection fault in processing EXPORT of empty data arrays.
• Corrects an error in plotting data on a mesh imported by TRANSFERMESH.

• Known Issues:
• NEUMANN boundary conditions do not correctly identify the surface on which to apply the condition. Use NATURAL instead.

Version 4.0.1    2/7/04

• Improved handling of thin shells and merged surfaces in 3D.  See "Samples | Misc | 3d_shell.pde".
• Corrects a bug in the Splinetable facility.
• Corrects a potential hangup in the 3D cutplane plotting procedure.

• Known Issue:  We are experiencing occasional failures in the 3D mesh generator. Most of these cases can be worked around by modifying the NGRID control parameter.  We are working on correcting this problem, and hope to have a new release soon.

• [4.0.1a] Corrects File | Save_as | Cancel.  File was written in spite of cancel.
• [4.0.1b] Corrects an error in software license decoding on Macintosh.

Version 4.0.0    1/25/04

FlexPDE Version 4 is a major rewrite of the FlexPDE application. In the first restructuring of the program, we have aimed in some areas merely to reproduce the behavior of version 3. But the newly structured program should facilitate many extensions that will appear as later versions are released.

Among the new features of FlexPDE version 4 in the initial release are:

MESH GENERATION

• Rewritten 2D mesh generator. The generated meshes should be better balanced than in version 3.  
• Rewritten 3D mesh generator. While the extrusion model has been retained for domain specification, the mesh generator itself is fully general, in preparation for general 3D figure specification in future releases.  
• LIMITED REGIONS in 3D allow selected figures to be restricted to specified layers, rather than being extruded throughout the domain, as in previous versions. See the discussion in the User Guide.
• Improved 3D mesh generation allows the specification of spherical or cylindrical surfaces without the side-bands required in previous versions.  
• Mesh density controls are fully 3D, with optional specification in volumes, on surfaces or in layers.  
• Mesh density induction for surface curvature and layer proximity.
• 3D mesh TRANSFER is now implemented.  

NEW RULES

• Equations must now be tagged with the name of the associated variable (e.g. U:) in order to make the assignment of boundary conditions to equations more explicit.
• Boundary conditions must now be placed inside the boundary path (after START).
  

MISCELLANEOUS

• SPLINE tables in one or two dimensions, using the same input format as TABLE.  
• Syntax highliting in the editor makes large script files easier to manage.
• Extended SUMMARY plot for eigenvalue problems makes reporting of mode-dependent data easier.  
• New dongle supplier offers better cross-platform network support, and single-machine USB dongles on all supported platforms.

MINOR versions
[4.0.0a] removes spurious boundary traces on 3D cutplane plots.
[4.0.0b] corrects software key decoding errors.
[4.0.0c] corrects errors in 2D mesh relaxation.
[4.0.0d] corrects errors in field upgrade of dongles.