Hi all [email protected] wrote: > Triple bonus points to Dante for cutting right to the heart of the matter. > > And it gets worse: there are algorithms out there that *change* what is > considered dependent and independent during the solution process. > The (often contemplated) der-style syntax {even if extendeded to > 'der(x,t); Independent(t)'} > basically has the problem of sewing a pile of special cases into the > compiler > and *hiding* variables. In a more likely model the user can write either > > der(x,t) in 15 places > or > they can simply write > link(xdot,x,t) once and use xdot without all the non-alphabetic > characters and > without sewing in a lot of new syntax and without making additional syntax > like der(x,t).fixed = true.
I would like to see ASCEND natively understand the idea of "derivative of" because I think it allows users to work in a way that is closer to their thinking. Why should one have to declare new variables if everything about them can be inferred? I think that the compiler can be expected to handle that. This is similar to the ongoing issue about improving the conditional modelling syntax, by creating inferred boolean variables, etc etc. I think it's important to do this, because the language is just too clunky in these areas. I am proposing something like x IS_A distance; INDEPENDENT t IS_A time; der(x) = x; OK, fair enough, let's work out a good compromise, but we have GSOC funding here with which to solve this problem properly, so I think that we can aim for a really neat and tidy solution that will make ASCEND more concise, and easier for new users. Maybe we need to have a hack and working further through this idea to see if it can really work. > > If we *really* like the der(x,t) approach, we should just ditch ascend and > go with an opensource compiler and system that fully supports it > instead of > reinventing the wheel. In particular openmodelica has it all, at the > 'cost' of > having to put up with nice gui's, etc, that work on mac/linux/windows. > And they finally got their licensing straightened out. OpenModelica is a worthy effort, but last time I checked they didn't support sophisticated thermo and they didn't have a conditional solver. And AFAICT it doesn't have the nice interactive approach that ASCEND has (fix/free on the fly, etc). So ASCEND is still in the game, and useful, and worth pursuing. Full support for derivatives in ASCEND is what this project is really about. Cheers JP ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Ascend-sim-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ascend-sim-users
