Hi,
Erik (in copy) contacted me asking that I upload again a few examples in GNU
Octave that I
wrote in the past (mention in this thread).
Do we have one standard location for examples?
I now the files provided at https://www.gnu.org/software/glpk/#downloading
have some examples and I happy to
Hi Mike,
I am new to GLPK and I can't the MIP solver to report integer values.
Basically, when I first call the simplex, and then cal glp_inop, the
message report that it found a solution but when I call glp_mip_col_val, it
reports double numbers, not integers.
This is the correct behavior.
Hi Andrew,
I understand that for MIPs, GLPK uses branch-and-bound and only
offers the simplex method. I would be interested in knowing why
the interior point method is only allowed for LPs, not MIPs.
In some cases the solution for MIP is one vertex of the problem and interior
point methods
I am looking for a repository of working C programs (or Java, or Ruby,
or...) that access GLPK and demo its awesomeness.
https://gitorious.org/tutoriais-computacao-cientifica/glpk/source/9cd938d3e5ee00c3ec20ba6f68e3da6bad13238f:
Sorry that this set of examples is small.
Raniere
I'm want to use this to solve some optimization problem, but I dont know
how to input and compute it (Im using matlab). Optimization is not my
major so can you send me a tutorial of how it work, input constraints.
Not a tutorial, only some basic examples:
Hi Umar,
I would like to know about the techniques GPLK (or any other solver)
uses to ensure global consistency of all constraints while making a
choice. For example, for a MIP(mixed integer) program with binary
variables x_1...x_n a solver needs to decide whether a variable x_i will
be 0 or
Hi Roy,
To retrieve the values of the objective function and variables values with the
C API look for the functions:
* glp_get_obj_val
* glp_get_col_prim
I hope that is what you are looking for.
Raniere
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Where in the source code I have to look at? Any tip for a article about
that?
The scaling affects only the basis factorization and the simplex solver.
Let me see if I understanding correctly. When solving a MIP, for each node of
the tree it scale the problem before use the simplex solver
Hi Abhishek,
Can I run a glpsol program and get it to run a java program?
No. `glpsol` is a C program that uses GLPK C-API.
Can my data file be a java file and my code be a mod file?
Maybe you can write a Java program that read your model and use the data from
your other Java program.
Hello Juan,
I am compiling using: g++ example.cpp -lglpk -o example
However, when I run the file ./example I get:
error while loading shared libraries: libglpk.so.35: cannot open shared
object file: No such file or directory
Your operational system can't locate the shared library. You
Hi Bruce,
I checked the current version 4.52 and didn't find it support quadratic
programming.Is there any plans to add quadratic programming feature to glpk?
Simple answer
-
I don't know.
Long answer
---
AFAIK, the simplex method didn't work with quadratic programming.
Hello,
I was trying to install GLPK 4.35 on my Ubuntu 12.05 LTS system but
couldn't succeed. I downloaded the sig file and ran the following
command:
sudo gpg --verify glpk-4.35.tar.gz.sig
Why are you running gpg as root? AFAIK, the error you got is because you are
using gpg as root.
I would like to ask whether the matrices ia[], ja[], ar[] have a size
limitation or the only limitation that exists is due to the PC memory.
AFAIK, the PC memory or the limitation is the `INT_MAX` from `limits.h`.
Raniere
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Hi Dieter,
I am new to GLPK and so far I'm very impressed by it's capabilities. My
question goes to solving non-linear problems written in GMPL using e.g.
ipopt. Is there an interface or could anyone point me into a direction
where i can learn how to do this? I'm on Linux Mint, so I
Hi Giorgio,
I have a model to which I can provide a initial feasible solution.
How can I do that?
I do long time ago (about 3 years).
Initially I tried with glp_read_mip:
I didn't use that. Hope that some one can help you with that.
The second attempt was with the callback routine:
Hi Luca,
The problem is as follows:
minimize { sum[from i=1 to 96] of {c1*x1(i)+c2*x2(i)+c3*x3(i)} }
with this constraints:
x1(i)+x2(i)+x3(i)=c4(i)
x1(i)+x3(i)=c5
x1=5
0=x2=1 binary
0=x3=1 binary
where x1, x2, x3 and c4 are vectors of 96 elements. c1,c2,c3,c5 are
contants.
by Raniere Silva r.gaia...@gmail.com */
#include stdio.h
#include stdlib.h
#include glpk.h
int main(void){
int n = 96, i, ir, j, jc;
double c1=1.0;
double c2=1.0;
double c3=1.0;
double c5=1.0;
double c4[97];
for(j = 1; j = n; j++){
c4[j] = 1.0;
}
glp_prob *lp
Jeffrey,
Maybe I'm missing something, but shouldn't there be a call to mip solver
somewhere in your code?
Yes, you right. Sorry about the mistake.
Briefly, just replace `glp_simplex` in line 81 by `glp_intopt`.
Raniere
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