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Re: [Help-glpk] Java interface to GLPK - accessing result values


From: xypron
Subject: Re: [Help-glpk] Java interface to GLPK - accessing result values
Date: Fri, 13 Feb 2009 11:07:39 -0800 (PST)

Hello Hartwig,

>> I plan to use GLPK by a Java application. 
>> My question is about the step after solving the model. I want to further
>> use the result 
>> values (values of decision variables after successful model solve) in my
>> Java application. 
>> I created a solution which avoids files and databases. 

it is not necessary to use a file or a database to access solutions. I only
tried
to keep my example GLPKSwig.java as simple as possible.

Methods are provided by the API to retrieve the result values. These are
described 
in doc/gmpl.pdf of the GLPK source distribution
ftp://ftp.gnu.org/gnu/glpk/glpk-4.36.tar.gz

Here you will also find all methods needed to create the problem 
without using an input file.

See the example below.

Best regards

Xypron

        /**
         * write MIP solution
         * @param lp problem
         */
        static void write_mip_solution(glp_prob lp)
        {
                int i;
                int n;
                String name;
                double val;
                
                n = GLPK.glp_get_num_cols(lp);
                for(i=1; i <= n; i++)
                {
                    name = GLPK.glp_get_col_name(lp, i);
                    val  = GLPK.glp_mip_col_val(lp, i);
                    System.out.printf("%s = %f\n", name, val);
                }
        }

        /**
         * write simplex solution
         * @param lp problem
         */
        static void write_lp_solution(glp_prob lp)
        {
                int i;
                int n;
                String name;
                double val;
                
                n = GLPK.glp_get_num_cols(lp);
                for(i=1; i <= n; i++)
                {
                    name = GLPK.glp_get_col_name(lp, i);
                    val  = GLPK.glp_get_col_prim(lp, i);
                    System.out.printf("%s = %f\n", name, val);
                }
        }



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