diff -r d59bea55db9b -r c445c931472f examples/t1.cs --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/examples/t1.cs Mon Dec 06 13:09:21 2010 +0100 @@ -0,0 +1,99 @@ +/*Find the minimum value which satisfies the linear inequality: + a*x + b*y >= 1 {a,b,x,y Integers} {a,b > 0} {a,b entered on command line} + + Nigel_Galloway@operamail.com + February 2008 +*/ +using System; +using System.Runtime.InteropServices; + +unsafe class GLPK{ + double *lp; + public int a; + public int b; + + const string glpkLibrary = "libglpk.so"; + readonly int GLP_FR = 1; + readonly int GLP_IV = 2; + readonly int GLP_DB = 4; + struct ConstraintMatrix{ + public fixed int ia[3]; + public fixed int ja[3]; + public fixed double ar[3]; + } + [DllImport(glpkLibrary, SetLastError=true)] + static extern double* glp_create_prob(); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_add_rows(double* lp, int rows); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_add_cols(double* lp, int cols); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_set_col_bnds(double* lp, int col, int bound_type, double lower_bound, double upper_bound); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_set_col_kind(double* lp, int col, int kind); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_load_matrix(double* lp, int elements, int* ia, int* ja, double* ar); + public GLPK(int a, int b){ + this.a = a; + this.b = b; + lp = glp_create_prob(); + //Col 1 is x, Col 2 is y + glp_add_rows(lp, 1); + glp_add_cols(lp, 2); + glp_set_col_bnds(lp, 1, GLP_FR, 0.0, 0.0); + glp_set_col_bnds(lp, 2, GLP_FR, 0.0, 0.0); + glp_set_col_kind(lp, 1, GLP_IV); + glp_set_col_kind(lp, 2, GLP_IV); + //Row 1 is a*x + b*y + ConstraintMatrix CM = new ConstraintMatrix(); + CM.ia[1]=1; CM.ja[1]=1; CM.ar[1]=a; + CM.ia[2]=1; CM.ja[2]=2; CM.ar[2]=b; + glp_load_matrix(lp, 2, CM.ia, CM.ja, CM.ar); + Console.WriteLine("Hello Nigel"); + } + + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_set_row_bnds(double* lp, int row, int bound_type, double lower_bound, double upper_bound); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_simplex(double* lp, void* options); + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_intopt(double* lp, void* options); + [DllImport(glpkLibrary, SetLastError=true)] + static extern double glp_mip_col_val(double* lp, int col); + public int betterGuess(int upper_bound){ + //Find a new guess less than the old guess: 1 <= (a*x + b*y) <= (old guess - 1) + glp_set_row_bnds(lp, 1, GLP_DB, 1.0, ((double)upper_bound)-0.5); + glp_simplex(lp, null); + glp_intopt(lp, null); + int x = (int)glp_mip_col_val(lp, 1); + int y = (int)glp_mip_col_val(lp, 2); + int nextGuess = a*x + b*y; + Console.WriteLine("x = {0}, y = {1}, a*x + b*y = {2}",x,y,nextGuess); + return nextGuess; + } + + [DllImport(glpkLibrary, SetLastError=true)] + static extern void glp_delete_prob(double* lp); + ~GLPK(){ + glp_delete_prob(lp); + Console.WriteLine("Goodbye Nigel"); + } + +} + +class test{ + static bool isMinimum(int a, int b, int guess){ + Console.WriteLine("Trying {0}",guess); + if (a%guess > 0) return false; + if (b%guess > 0) return false; + Console.WriteLine("Solution is {0}",guess); + return true; + } + + public static void Main(string[] args){ + Console.WriteLine("a = {0}, b = {1}",args[0], args[1]); + GLPK lp = new GLPK(Int32.Parse(args[0]),Int32.Parse(args[1])); + int guess = (lp.a > lp.b) ? lp.b : lp.a; + while (!isMinimum(lp.a,lp.b,guess)) guess = lp.betterGuess(guess); + } +}