Hi John, Are you able to compile GLPK from source? I'll aim to provide an updated source code and some more details/examples over the weekend.
On Thu, 5 Oct 2017 at 2:17 am, john tass <[email protected]> wrote: > Hi Lyndon, again. > Please do not forget to include in the example that you possibly will send > to me, the way of how to refer to your extension and how I can have access > to the solution. > Thanks. > > 2017-10-04 18:11 GMT+03:00 john tass <[email protected]>: > >> Hi Lyndon, >> Yes, it is exactly what I was looking for. I assume that by the way you >> suggest I shall be able to write pure MathProg code. I make this comment >> because I do not want simply to use just 2 or three variables (as the >> example you sent, x1 and x2) but hundreds of them. So, I need the >> flexibility that MathProg provides. The same holds for the constraints >> that refer to those variables, which are many, too. >> Is it possible to send me an example which contains say 50 variables (x1, >> x2, x3, ..., x50) without having to hard-code them? In other words, the >> example should declare the variables by the use of indices. In addition, >> please make an effort to mention how I get back to C function the optimal >> objective value and the values of the variables concerning the optimal >> solution. >> Thank you a lot. >> >> 2017-10-04 15:44 GMT+03:00 Lyndon D'Arcy <[email protected]>: >> >>> John, the reason I ask is, I wrote a small extension to allow reading a >>> MathProg model from memory instead of an external file. I'm not sure if >>> this is what you are looking for exactly. But it would allow you to >>> generate the MathProg code in-memory, and then read the resulting program >>> into GLPK. I think I would need to add another function to allow you to >>> process the solution in memory as well. Then you would be able to do >>> everything without ever needing to leave the C environment, or read/write >>> text files, or maintain a model file that had been generated separately. >>> Is that what you're looking for? >>> >>> Below is some example code for reading MathProg using my extension: >>> >>> int status; >>> char *buf = "var x1;\ >>> var x2;\ >>> maximize obj: 0.6 * x1 + 0.5 * x2;\ >>> s.t. c1: x1 + 2 * x2 <= 1;\ >>> s.t. c2: 3 * x1 + x2 <= 2;\ >>> end;"; >>> glp_prob *lp; >>> glp_tran *tran = glp_mpl_alloc_wksp(); >>> status = glp_mpl_read_buffer_into_model(tran, buf, strlen(buf), 0); >>> ck_assert_int_eq(status, 0); >>> if (!status) { >>> status = glp_mpl_generate(tran, NULL); >>> if (!status) { >>> lp = glp_create_prob(); >>> glp_mpl_build_prob(tran, lp); >>> } >>> } >>> glp_mpl_free_wksp(tran); >>> glp_delete_prob(lp); >>> glp_free_env(); >>> >>> On 4 October 2017 at 22:49, Andrew Makhorin <[email protected]> wrote: >>> >>>> >>>> > I am trying to write a function in ANCI C programming language. The >>>> > aim of this function is to get some input arguments from the main C >>>> > program, then solve a MIP problem and return the value of objective >>>> > function along with the values of structural variables back to the C >>>> > main program. >>>> > The issue is that the MIP problem I am about to solve via glpk has a >>>> > quite large number of variables. So, I am not able to hard-code them. >>>> > Hence, I came across the idea to use MathProg language, as it is very >>>> > easy to code my model. >>>> > The question is, how to do this? Is it possible to incorporate >>>> > MathProg code inside a C language function? Please note that I am >>>> > aware of how to write a C program that calls API routines of glpk in >>>> > order to solve a simple model, but here I am not referring to this >>>> > case. >>>> > Any suggestion of a site, pdf or relevant document will be very >>>> > helpful. >>>> >>>> Please see Section 3.2 "Routines for processing MathProg models" in the >>>> glpk reference manual (file glpk.pdf can be found in the subdirectory >>>> 'doc' in every glpk distribution tarball). >>>> >>>> >>>> >>>> _______________________________________________ >>>> Help-glpk mailing list >>>> [email protected] >>>> https://lists.gnu.org/mailman/listinfo/help-glpk >>>> >>> >>> >> >> >> -- >> Dr. Ioannis X. Tassopoulos, MSc., Ph.D. >> >> > > > -- > Dr. Ioannis X. Tassopoulos, MSc., Ph.D. > >
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