-------- Forwarded Message -------- From: Jeffrey Kantor <jeff.kan...@gmail.com> To: "Meketon, Marc" <marc.meke...@oliverwyman.com> Cc: Andrew Makhorin <m...@gnu.org>, Domingo Alvarez Duarte <mingodad@gmai l.com>, help-glpk@gnu.org <help-glpk@gnu.org> Subject: Re: Adding if/then/else statement to GMPL Date: Mon, 24 Aug 2020 09:54:33 -0500
> This would be another vote for extending GMPL to include features to > support the iterative use of LP’s. As is stands, GMPL is a sweet > little modeling tool … a well-crafted application is small work of art > that is generally clear and unambiguous. One mark fo a good model is > the ability to go back years later and instantly recall the logic > behind the model. > > There are so many more applications where iteration is a natural part > of the modeling. Stocking cutting, for example. Stochastic > programming. With these features, GMPL could continue to be a useful > tool for developing and documenting models and MILP applications. > Without these features, tools like PULP and Pyomo become the lingua > franca of the field. > > > On Aug 24, 2020, at 9:00 AM, Meketon, Marc via Users list for GLPK > > (GNU Linear Programming Kit) <help-glpk@gnu.org> wrote: > > > > I've always felt that GMPL needed if-then-else, for-loops, 'let' > > statements and the ability to re-solve to be a true modeling > > language. And Andrew has always disagreed. > > > > Many of the models that I create ultimately are 'iterative' where I > > need to take the results of one model and use it to setup another > > model. To me, that is also modeling. GMPL doesn't have it. > > > > So often, I use GMPL for an initial model - it is a wonderful > > language, and I find it faster to code than alternatives. But then > > when I 'get it right' I have to re-code it in PYOMO or PULP or write > > directly to an 'lp' file within a Python or C# or other language > > script. > > > > Having the ability to run, adjust variables, add/take away > > constraints, re-run would be extremely useful, and make GMPL more of > > a one-stop modeling language. > > > > -----Original Message----- > > From: Help-glpk <help-glpk-bounces+marc.meketon=oliverwyman.com@gnu. > > org> On Behalf Of Andrew Makhorin > > Sent: Sunday, August 23, 2020 2:56 PM > > To: Domingo Alvarez Duarte <mingo...@gmail.com>; help-glpk@gnu.org > > Subject: Re: Adding if/then/else statement to GMPL > > > > On Sun, 2020-08-23 at 15:36 +0200, Domingo Alvarez Duarte wrote: > > > Hello ! > > > > > > Also I've added the break/continue statements here > > > https://github.com/mingodad/GLPK/commit/9d70a37b16bd377722eeb3880f > > > cf86 > > > bb3b812118 > > > > > > > > > Again any comment/suggestion is welcome ! > > > > > > Cheers ! > > > > > > > > > > > > > Please note that GNU MathProg is a *modeling* language; it is not a > > general-purpose programming language. If you need to produce a non- > > trivial solution report (since all such-like statements are allowed > > only on the post-solving stage), it would be more practical to write > > the solution to a temporary file and then process it with a separate > > program. > > > > > > > > > > ________________________________ > > This e-mail and any attachments may be confidential or legally > > privileged. If you received this message in error or are not the > > intended recipient, you should destroy the e-mail message and any > > attachments or copies, and you are prohibited from retaining, > > distributing, disclosing or using any information contained herein. > > Please inform us of the erroneous delivery by return e-mail. Thank > > you for your cooperation. > >