Main file

Sheet5/Ex2_Second_Attempt/mainEx2.cpp

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+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <cmath>
+#include <algorithm>
+// #include <execution>   // only include if the compiler supports it
+#include <omp.h>
+
+using namespace std;
+
+// OpenMP parallel computations (already implemented)
+void computeMeansVectorParallel(const vector<int> &v, double &arith, double &geom, double &harm) {
+    int n = v.size();
+    double sum = 0.0, logSum = 0.0, recSum = 0.0;
+
+    #pragma omp parallel for reduction(+:sum,logSum,recSum)
+    for (int i = 0; i < n; ++i) {
+        int x = v[i];
+        sum += x;
+        logSum += log(x);
+        recSum += 1.0 / x;
+    }
+
+    arith = sum / n;
+    geom  = exp(logSum / n);
+    harm  = n / recSum;
+}
+
+double computeStdDevParallel(const vector<int> &v, double mean) {
+    int n = v.size();
+    double sumSq = 0.0;
+
+    #pragma omp parallel for reduction(+:sumSq)
+    for (int i = 0; i < n; ++i) {
+        double diff = v[i] - mean;
+        sumSq += diff * diff;
+    }
+
+    return sqrt(sumSq / n);
+}
+
+int main() {
+    cout << "Exercise Sheet 5: Task 2\n";
+    // Read data
+    vector<int> v;
+    ifstream fin("data_1.txt");
+    int x;
+    while (fin >> x) v.push_back(x);
+    fin.close();
+
+    cout << "Data size: " << v.size() << "\n";
+
+    double t_start = omp_get_wtime();
+
+    // OpenMP parallel computations
+    #pragma omp parallel
+    {
+        #pragma omp single
+        cout << "Using " << omp_get_num_threads() << " OpenMP threads\n";
+    }
+
+    int minVal = v[0], maxVal = v[0];
+    #pragma omp parallel
+    {
+        int local_min = v[0], local_max = v[0];
+        #pragma omp for nowait
+        for (int i = 0; i < v.size(); ++i) {
+            if (v[i] < local_min) local_min = v[i];
+            if (v[i] > local_max) local_max = v[i];
+        }
+        #pragma omp critical
+        {
+            if (local_min < minVal) minVal = local_min;
+            if (local_max > maxVal) maxVal = local_max;
+        }
+    }
+
+    double arith, geom, harm;
+    computeMeansVectorParallel(v, arith, geom, harm);
+
+    double stddev = computeStdDevParallel(v, arith);
+
+    double t_end = omp_get_wtime();
+
+    cout << "OpenMP results:\n";
+    cout << "Min: " << minVal << ", Max: " << maxVal << "\n";
+    cout << "Arithmetic mean: " << arith
+         << ", Geometric mean: " << geom
+         << ", Harmonic mean: " << harm << "\n";
+    cout << "Standard deviation: " << stddev << "\n";
+    cout << "Elapsed time (s): " << t_end - t_start << "\n\n";
+
+    cout << "\nNote: The C++17 execution::par version is implemented in the main file, "
+        "but my Mac's Clang compiler does not support parallel execution policies.\n";
+
+    // C++17 execution policy version
+    /*
+    double t_ep_start = omp_get_wtime();
+
+    auto p = minmax_element(execution::par, v.begin(), v.end());
+    double min_ep = *p.first;
+    double max_ep = *p.second;
+
+    double sum_ep = reduce(execution::par, v.begin(), v.end(), 0.0);
+    double ar_ep = sum_ep / v.size();
+
+    double geom_ep = transform_reduce(
+        execution::par,
+        v.begin(), v.end(),
+        0.0,
+        plus<>(),
+        [n=v.size()](int val){ return log(val); }
+    );
+    geom_ep = exp(geom_ep / v.size());
+
+    double sum_inv_ep = transform_reduce(
+        execution::par,
+        v.begin(), v.end(),
+        0.0,
+        plus<>(),
+        [](int val){ return 1.0 / val; }
+    );
+    double harm_ep = v.size() / sum_inv_ep;
+
+    double sum_sq_ep = transform_reduce(
+        execution::par,
+        v.begin(), v.end(),
+        0.0,
+        plus<>(),
+        [ar_ep](int val){ double d = val - ar_ep; return d*d; }
+    );
+    double std_ep = sqrt(sum_sq_ep / v.size());
+
+    double t_ep_end = omp_get_wtime();
+
+    cout << "Execution policy results:\n";
+    cout << "Min: " << min_ep << ", Max: " << max_ep << "\n";
+    cout << "Arithmetic mean: " << ar_ep
+         << ", Geometric mean: " << geom_ep
+         << ", Harmonic mean: " << harm_ep << "\n";
+    cout << "Standard deviation: " << std_ep << "\n";
+    cout << "Elapsed time (s): " << t_ep_end - t_ep_start << "\n";
+    */
+    return 0;
+}