84 lines
1.9 KiB
C++
84 lines
1.9 KiB
C++
// #include <omp.h>
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#include "walltime.h"
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#include <iostream>
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#include <math.h>
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#include <stdio.h>
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#include <unistd.h>
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#define NUM_ITERATIONS 100
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// Example benchmarks
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// 0.008s ~0.8MB
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#define N 100000
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// 0.1s ~8MB
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// #define N 1000000
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// 1.1s ~80MB
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// #define N 10000000
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// 13s ~800MB
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// #define N 100000000
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// 127s 16GB
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//#define N 1000000000
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#define EPSILON 0.1
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using namespace std;
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int main() {
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double time_serial, time_start = 0.0;
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double *a, *b;
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// Allocate memory for the vectors as 1-D arrays
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a = new double[N];
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b = new double[N];
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// Initialize the vectors with some values
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for (int i = 0; i < N; i++) {
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a[i] = i;
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b[i] = i / 10.0;
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}
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long double alpha = 0;
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// serial execution
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// Note that we do extra iterations to reduce relative timing overhead
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time_start = wall_time();
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for (int iterations = 0; iterations < NUM_ITERATIONS; iterations++) {
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alpha = 0.0;
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for (int i = 0; i < N; i++) {
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alpha += a[i] * b[i];
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}
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}
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time_serial = wall_time() - time_start;
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cout << "Serial execution time = " << time_serial << " sec" << endl;
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long double alpha_parallel = 0;
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double time_red = 0;
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double time_critical = 0;
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// TODO: Write parallel version (2 ways!)
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// i. Using reduction pragma
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// ii. Using critical pragma
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for (int iterations = 0; iterations < NUM_ITERATIONS; iterations++) {
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alpha_parallel = 0.0;
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for (int i = 0; i < N; i++) {
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alpha_parallel += a[i] * b[i];
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}
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}
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if ((fabs(alpha_parallel - alpha) / fabs(alpha_parallel)) > EPSILON) {
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cout << "parallel reduction: " << alpha_parallel << ", serial: " << alpha
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<< "\n";
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cerr << "Alpha not yet implemented correctly!\n";
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exit(1);
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}
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cout << "Parallel dot product = " << alpha_parallel
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<< " time using reduction method = " << time_red
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<< " sec, time using critical method " << time_critical << " sec"
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<< endl;
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// De-allocate memory
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delete[] a;
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delete[] b;
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return 0;
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}
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