sheet 4

sheet4/C/main.cpp

@@ -0,0 +1,51 @@
+
+#include <iostream>
+#include <sstream>
+#include <vector>
+#include <cmath>
+#include <lapacke.h>
+using namespace std;
+
+
+int main()
+{   
+    unsigned int ns[5] = {10,20,30,40,70};
+    int p = 70;
+    int rhs = 1;
+    for(unsigned int i = 0; i< sizeof(ns)/sizeof(ns[0]); i++)
+    {
+        int n=ns[i];
+        unsigned int nodes = n+1;
+
+        vector<double> upperdiagonal(n,-n+p/2.0);
+        vector<double> lowerdiagonal(n,-n-p/2.0);
+        vector<double> diagonal(nodes,2*n);
+        vector<double> F(nodes,0.0);
+        upperdiagonal[0]=0.0;
+        lowerdiagonal[n-1]=0.0;
+        diagonal[0] = 1.0;
+        diagonal[n] = 1.0;
+        F[n] = 1.0;
+
+        //Tridiagonal
+        LAPACKE_dgtsv(LAPACK_COL_MAJOR,nodes,rhs,lowerdiagonal.data(),diagonal.data(),upperdiagonal.data(),F.data(),nodes);
+
+
+         cout << "Solution u_h at nodes x_0..x_" << n << ":\n";
+    
+        for (unsigned int j = 0; j < nodes; ++j) {
+
+            double xi = double(j) /double(n);
+            cout << "u_h(" << xi << ") = " << F[j] << "\n";
+            // F will be overwritten with sol
+        }
+    }
+
+    /*
+    From Methode  der finiten Elemente fuer Ingenieure:
+    small n approximates pu' not good espicially if n < p/2=35 therefor this oscillation (see plot) occurs.
+    */
+    return 0;
+
+    
+}