In MiniZinc (windows IDE) How can I resolve: flatzinc: error: variables of type `var float' are not supported by the FD solver backend. I realize I need a different solver but could not find a procedure installing one and the Preferences dlg does not seem to work. Also, not clear which solver would work.
The G12/fd solver don't support float decision variables. Do you find G12 MIP solver in the "Solver" list? If so, try it and see if it can solve the model. There is a Help text ("Help, Help...") that might help you add the solver if not.
However, if it's an non-linear model then G12/mip might complain, and you have to try another solver. Gecode and JaCoP has some support for non-linear float models.
In MiniZinc 2.0 it might work with G12/mip and a non-linear model if the "-G linear" flag is used: mzn2fzn will then linearize non-linear constraints.