Several items have been changed in version 5 that may require some attention for users of FlexPDE version 4. In general, we have tried to make the transition as simple as possible.
|•||ERROR ESTIMATION: The algorithms used for error estimation have been changed in version 5. In most cases, the new measures are more pessimistic that those used in version 4, resulting in some cases in more intense mesh refinement and longer running. Nevertheless, we feel that the new algorithms provide an error measure closer to the actual disparity between the numerical and analytical solutions in test problems. In order to ameliorate the impact of this change, we have relaxed the default ERRLIM to 0.002 and allowed individual cells to exceed the ERRLIM specification, as long as a weighted average of errors is below ERRLIM. You may wish to adjust your ERRLIM specifications to reflect this new behavior.|
|•||SMOOTHING INITIAL VALUES: Version 5 applies a smoothing procedure to initial conditions in time-dependent problems, to ameliorate the harsh behaviour caused by discontinuous initial conditions. In most cases, you will experience a much quicker startup, with no significant difference in solution. The smoothing operation is scaled to cell sizes, so you can recover accurate resolution of initial transients by merely specifying dense meshing at important initial discontinuities. The smoothing operation can be suppressed by SELECT SMOOTHINIT=OFF.|
|•||CLOSE: The reserved word FINISH used in previous versions has been changed to CLOSE, to more accurately reflect its function. You will be warned once, after which FINISH will be accepted as in version 4. Except in cases where you want to run a problem on both versions, we suggest converting to the new format.|
|•||GLOBAL: The designation SCALAR VARIABLES used in version 4 has been changed to GLOBAL VARIABLES, to more accurately reflect its function. You will be warned once, after which SCALAR VARIABLES will be accepted as in version 4. Except in cases where you want to run a problem on both versions, we suggest converting to the new format.|