1 files changed, 99 insertions, 0 deletions
diff --git a/glpk-5.0/examples/t1.cs b/glpk-5.0/examples/t1.cs
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+++ b/glpk-5.0/examples/t1.cs
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+/*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);
+  }
+}