LisaPizzoExercises/Sheet5/mainEx4.cpp

// HOW TO COMPILE ON MAC 
// export CPPFLAGS="-I/opt/homebrew/opt/libomp/include"
// export LDFLAGS="-L/opt/homebrew/opt/libomp/lib"
// clang++ -std=c++17 -O3 -Xpreprocessor -fopenmp $CPPFLAGS main.cpp bench_funcs.cpp $LDFLAGS -lomp -o Ex4
// ./Ex4


#include <iostream>
#include <vector>
#include <cmath>
#include <iomanip>
#include <chrono>
#include "bench_funcs.h"
#include <omp.h>   

using namespace std;
using namespace std::chrono;

void gen_vector_x_y(size_t N, vector<double>& x, vector<double>& y) {
    x.resize(N);
    y.resize(N);
    for (size_t i = 0; i < N; ++i) {
        x[i] = (i % 219) + 1;
        y[i] = 1.0 / x[i];
    }
}

void gen_matrix_A(size_t M, size_t N, vector<double>& A) {
    A.resize(M * N);
    for (size_t i = 0; i < M; ++i)
        for (size_t j = 0; j < N; ++j)
            A[i * N + j] = ((i + j) % 219) + 1;
}

high_resolution_clock::time_point tic_timer;
void tic() { tic_timer = high_resolution_clock::now(); }
double toc() {
    auto t1 = high_resolution_clock::now();
    duration<double> elapsed = t1 - tic_timer;
    return elapsed.count();
}

// CHANGE THE flag VARIABLE IN main() TO CHOOSE A, B, C, D.
int main() {
    size_t N = 1'000'000;   
    size_t M = 3000, L = 3000;

    // Check OpenMP threads
    #pragma omp parallel
    {
        #pragma omp single
        cout << "Using " << omp_get_num_threads() << " OpenMP threads\n";
    }

    // Show menu
    cout << "Choose an option:\n";
    cout << "  1) SUM + DOT PRODUCT\n";
    cout << "  2) MATRIX-VECTOR PRODUCT\n";
    cout << "  3) MATRIX-MATRIX PRODUCT\n";
    cout << "  4) POLYNOMIAL EVALUATION\n";
    cout << "Enter your choice (1-4): ";

    int flag;
    cin >> flag;

    // validate input
    if(flag < 1 || flag > 4){
        cout << "Invalid choice. Exiting.\n";
        return 1;
    }

    // A) SUM + DOT PRODUCT (parallel)
    if (flag == 1) {
        vector<double> x, y;
        gen_vector_x_y(N, x, y);

        cout << "Running parallel SUM" << endl;
        tic();
        double ssum = sum_basic(x); (void)ssum;
        double dt_sum = toc();
        cout << "  sum time = " << dt_sum << " s\n";

        cout << "Running parallel DOT PRODUCT" << endl;
        tic();
        double sdot = dot_basic(x, y); (void)sdot;
        double dt_dot = toc();
        cout << "  dot time = " << dt_dot << " s\n";

        double flops_dot = 2.0 * N;
        double gflops_dot = (flops_dot / dt_dot) / 1e9;

        cout << "A: N=" << N << "\n";
        cout << "   SUM time=" << dt_sum << " s\n";
        cout << "   DOT time=" << dt_dot << " s  GFLOPS=" << gflops_dot << "\n";
    }

    // B) MATRIX–VECTOR PRODUCT (parallel)
    else if (flag == 2) {
        size_t m = M, n = 5000;
        vector<double> A, x, b;

        gen_matrix_A(m, n, A);
        x.resize(n);
        for (size_t j = 0; j < n; ++j)
            x[j] = 1.0 / (((17 + j) % 219) + 1);

        cout << "Running Matrix times vector (parallel)\n";
        tic();
        matvec_rowmajor(A, m, n, x, b);
        double dt = toc();

        double flops = 2.0 * m * n;
        double gflops = (flops / dt) / 1e9;

        cout << "B: M=" << m << " N=" << n
             << " time=" << dt << " s  GFLOPS=" << gflops << endl;
    }

    // C) MATRIX–MATRIX PRODUCT (parallel)
    else if (flag == 3) {
        size_t m = M, l = L, n = 500;
        vector<double> A, B, C;

        gen_matrix_A(m, l, A);
        gen_matrix_A(l, n, B);

        cout << "Running Multiplication of matrices (parallel)\n";
        tic();
        matmul_rowmajor(A, m, l, B, n, C);
        double dt = toc();

        double flops = 2.0 * m * l * n;
        double gflops = (flops / dt) / 1e9;

        cout << "C: M=" << m << " L=" << l << " N=" << n
             << " time=" << dt << " s  GFLOPS=" << gflops << endl;
    }

    // D) POLYNOMIAL EVALUATION (parallel Horner)
    else if (flag == 4) {
        size_t p = 100; // degree
        vector<double> a(p+1), x(N), y;

        for (size_t k = 0; k <= p; ++k)
            a[k] = 1.0 / (k+1);

        for (size_t i = 0; i < N; ++i)
            x[i] = (i % 219) * 0.001 + 1.0;

        cout << "Running polynomial function (parallel)\n";
        tic();
        polyp_horner(a, x, y);
        double dt = toc();

        double flops = 2.0 * p * N;
        double gflops = (flops / dt) / 1e9;

        cout << "D: p=" << p << " N=" << N
             << " time=" << dt << " s  GFLOPS=" << gflops << endl;
    }

    else {
        cout << "Invalid flag — choose 1, 2, 3, or 4.\n";
    }

    cout << "\nDone \n";
    return 0;
}