| Author | Message | ||
     Victor Manuel Rodriguez Zermeno (victor) New member Username: victor Post Number: 1 Registered: 11-2003 |
I am getting some errors like (these are just a few examples): overflow treeval_eval_ba ba_binop sparsemx_big_eigen_0 space_matrix_0 coupling_tr_matrix_0 onestep_0 startup_0 I can modify a little here or there (mesh_density, errorlim, changelim, etc), run the program again and not see them. I would like to know what the actual nature of these errors is. I didn't find any related info in the technical notes/reference/user guide/getting started. So, do you have any info on the subject? I mean, knowing the meaning of the errors would help me to know were to modify directly, rather that go "here and there". Thanks. | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 54 Registered: 06-2003 |
Since the FlexPDE input script is in essence a computer program, it is always possible for a user to pose an arithmetic sequence that cannot be computed by the hardware. For example, if you specify the equation dt(u)=u, the evolution of the exponentiating solution will very soon exceed the ability of the hardware to represent numbers. In these cases, the hardware issues a trap to the operating system, which is handed on to FlexPDE as an interrupt with an error code. FlexPDE reports that this has happened (the first line of the error report), and gives a trace of the sequence of nested calls in the FlexPDE code that indicates the process underway when the trap occurred. When such an interrupt occurs, it is impossible for FlexPDE to bactrack through the sequence of events and try to intuit the fundamental cause of the disaster. Nevertheless, the message is that you have posed a set of equations that cannot be computed. The best way to proceed is to start with a much simpler problem, one that you can get to work correctly, and gradually add the complexity of your final problem. Usually in this endeavor you will reach a point where you say, "Aha", and curse your oversight. If such an approach does not lead you to an "Aha", then send us the offending script, and we will try to determine the cause. |