From 81f603e327a4425ff77a5d71e24a7ff41c9ecfc7 Mon Sep 17 00:00:00 2001
From: "lisa.pizzo" <lisa.pizzo@noreply.imsc.uni-graz.at>
Date: Tue, 2 Dec 2025 09:36:18 +0100
Subject: [PATCH] Main file - Exercise 1

---
 Sheet5/mainEx1.cpp | 94 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Sheet5/mainEx1.cpp

diff --git a/Sheet5/mainEx1.cpp b/Sheet5/mainEx1.cpp
new file mode 100644
index 0000000..c653f76
--- /dev/null
+++ b/Sheet5/mainEx1.cpp
@@ -0,0 +1,94 @@
+//HOW TO RUN IT ON MY TERMINAL (MAC)
+//export LDFLAGS="-L/opt/homebrew/opt/libomp/lib"
+//export CPPFLAGS="-I/opt/homebrew/opt/libomp/include"
+//clang++ -std=c++17 -O2 -Xpreprocessor -fopenmp $CPPFLAGS main.cpp mylib.cpp -L/opt/homebrew/opt/libomp/lib -lomp -o dotprod
+//./dotprod
+
+#include "check_env.h"
+#include "mylib.h"
+#include <cstdlib>          // atoi()
+#include <cstring>          // strncmp()
+#include <ctime>
+#include <iostream>
+#include <omp.h>            // OpenMP
+#include <sstream>
+#include <string>
+using namespace std;
+
+int main(int argc, char const *argv[])
+{
+    unsigned int N = 5000001;   // smaller default for testing
+    int const NLOOPS = 5;       // smaller loop for quick test
+
+    //##########################################################################
+    // Read Parameter from command line
+    cout << "=== Checking command line parameters ===" << endl;
+    for (int i = 1; i < argc; i++)
+    {
+        string ss(argv[i]);
+        if ("-n"==ss && i + 1 < argc)
+            N = static_cast<unsigned int>(atoi(argv[i + 1]));
+        else
+            cout << "Corect call: " << argv[0] << " -n  <number>\n";
+    }
+    cout << "\nVector size N = " << N << endl;
+
+    //##########################################################################
+    check_env(argc, argv);
+
+    //##########################################################################
+    cout << "\n=== Starting OpenMP test ===" << endl;
+    int nthreads;
+    #pragma omp parallel default(none) shared(cout,nthreads)
+    {
+        int const th_id  = omp_get_thread_num();
+        int const nthrds = omp_get_num_threads();
+        #pragma omp critical
+        cout << "Hello from thread " << th_id << " out of " << nthrds << endl;
+        #pragma omp master
+        nthreads = nthrds;
+    }
+    cout << "Total threads started: " << nthreads << endl;
+
+    //##########################################################################
+    cout << "\n=== Memory allocation ===" << endl;
+    vector<double> x(N), y(N);
+    cout << "Allocated memory for vectors x and y (" << N << " doubles each)" << endl;
+
+    //##########################################################################
+    cout << "\n=== Data initialization ===" << endl;
+    for (unsigned int i = 0; i < N; ++i)
+    {
+        x[i] = i + 1;
+        y[i] = 1.0 / x[i];
+    }
+    cout << "Vectors initialized: x[i] = i+1, y[i] = 1/x[i]" << endl;
+
+    //##########################################################################
+    cout << "\n=== Start Benchmarking inner product ===" << endl;
+    double tstart = omp_get_wtime();
+    double sk(0.0);
+    for (int i = 0; i < NLOOPS; ++i)
+    {
+        sk = scalar(x, y);
+        sk = scalar_trans(x, y);
+    }
+    double t1 = (omp_get_wtime() - tstart) / NLOOPS;
+    cout << "<x, y> = " << sk << endl;
+    if (static_cast<unsigned int>(sk) != N)
+        cout << "!! WRONG result !!" << endl;
+
+    cout << "Timing (average per loop) in sec: " << t1 << endl;
+    cout << "GFLOPS: " << 2.0 * N / t1 / 1024 / 1024 / 1024 << endl;
+    cout << "Memory throughput (GiByte/s): " << 2.0 * N / t1 / 1024 / 1024 / 1024 * sizeof(x[0]) << endl;
+
+    //##########################################################################
+    cout << "\n=== Testing reduction_vec (combining vectors across threads) ===" << endl;
+    cout << "Each thread initializes a vector of size 100; then vectors are combined." << endl;
+    auto vr = reduction_vec(100);
+    cout << "Resulting combined vector:" << endl;
+    cout << vr << endl;
+
+    cout << "\n=== Program finished ===" << endl;
+    return 0;
+}