Hosung Song wrote:

Professor Bagnara,

Greetings. I've got some help request on PPL usage. I'm sorry if I should have sent this email to someone else, but I didn't think the developer mailing list was appropriate, and there's no contact information in the PPL website (other than mailing lists). I'm currently working on extending a software model checker (Spin) to hybrid settings. This requires extensive polyhedra manipulations and naturally I was led to your PPL package. First of all, I'd like to thank you for your thorough work on the library. Unfortunately, Spin is written in C language and I myself am not a good C++ programmer, so I think I have to use C language interface of PPL. While C++ usage seems quite intuitive (I could see from the examples in the tests directory), there's no example using C interface, and the documentation about it seems quite terse. I'm wondering if you could provide some very simple example of C interface usage (e.g. C interface version of one example in the tests directory). I guess we can manipulate constraints, polyhedra and so on, but I don't know how to deal with variables. Are variables just indexed as integers as ppl_dimension_type? Anyway, a brief example would be greatly helpful. Thanks again for your wonderful package, and I look forward to your little help.

Best wishes,

Hosung Song

Dear Hosung,

the developer's mailing list is indeed the appropriate place if you want to get in touch with the PPL's developers. On their behalf, let me thank you for your nice words.

Coming to the C interface, what you write makes me suspect you did not look into the `interfaces/C/lpenum/' directory. It contains a toy LP solver written in C and using the PPL's C interface. There you can find examples of how to use several functions provided by that interface.

You guess right: a variable is represented by its index, and such indices are of type `ppl_dimension_type'. For example,

ppl_LinExpression_add_to_coefficient(le, i, k);

adds `k*x' to the linear expression represented by `le', where x is the variable corresponding to dimension `i'.

Your message indicates a number of things we can do to improve the PPL's web site and documentation. Thank you very much for your feedback and, please, do not hesitate to come back to us. All the best,

Roberto

P.S. A number of quite exciting new features are in preparation for the future releases of the PPL. These include support for more precise domains and for restricted classes of polyhedra for which very efficient algorithms are available. If you would like to tell us more about the application you are developing and how our library could make your life easier, please do so: this may help us to better direct our development efforts.