sheet 5

Sheet_5/bsp_5_3/main.cpp

@@ -0,0 +1,46 @@
+#include "bsp_5_3_lib.h"
+#include "mayer_primes.h"
+#include <iostream>
+#include <algorithm>
+#include <chrono>
+// BSP 5_3 Goldbach conjunction
+using namespace std;
+
+int main()
+{
+	omp_set_num_threads(8);
+	
+	cout << "\nChecking for correct result\n";
+	cout << "694 has " << single_goldbach_par(694) << " decompositions" << endl;
+	
+    // Auswertung für n=100000 bzw herausfinden der Zahl, welche die meisten Dekompositionen hat
+    vector<int> v = count_goldbach_par(1e5);
+    auto ip = max_element(v.begin(), v.end());
+    cout << "number in [4,1e5] with most decompositions: " << distance(v.begin(), ip)*2+4 << " has " << *ip << " decompositions" << endl;
+
+    cout << "\nTiming for parallel" << endl;
+    vector<int> nvec{static_cast<int>(1e4), static_cast<int>(1e5), static_cast<int>(4*1e5), static_cast<int>(1e6), static_cast<int>(2*1e6)}; // Vektor für n
+    for(size_t k=0; k<nvec.size(); ++k)
+    {
+        auto timestart = omp_get_wtime();
+        vector<int> vall = count_goldbach_par(nvec[k]);
+        auto time = omp_get_wtime() - timestart;
+        cout << "n = " << nvec[k] << "\ttime in s: " << time << endl;
+    }
+    
+    cout << "\nTiming for serial" << endl;
+    for(size_t k=0; k<nvec.size(); ++k)
+    {
+        auto timestart = omp_get_wtime();
+        vector<int> vall = count_goldbach(nvec[k]);
+        auto time = omp_get_wtime() - timestart;
+        cout << "n = " << nvec[k] << "\ttime in s: " << time << endl;
+    }
+    
+    // for large n the parallel version is slower than the sequential
+    // the reason is the reduction(VecAdd) which is slow especially for large vectors
+
+//    cout << single_goldbach(694) << endl;
+//    cout << count_goldbach(10000)[690/2] << endl;
+    return 0;
+}