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hpc-2022-g3/openmp/lab2/.solutions/pi-omp2.c

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/*
* BSD 2-Clause License
*
* Copyright (c) 2020, Alessandro Capotondi
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* @file exercise7.c
* @author Alessandro Capotondi
* @date 27 Mar 2020
* @brief Exercise 8
*
* Pi calculation
* @see https://dolly.fim.unimore.it/2019/course/view.php?id=152
*/
#include <stdio.h>
#include <omp.h>
#include "utils.h"
/**
* @brief EX 8- Pi Calculation
*
* This program computes pi as
* \pi = 4 arctan(1)
* = 4 \int _0 ^1 \frac{1} {1 + x^2} dx
*
* @return void
*/
#include <stdio.h>
#include <math.h>
#include <omp.h>
#include "utils.h"
#if !defined(ITERS)
#define ITERS (4)
#endif
#define NSTEPS 134217728
void exercise(){
long i;
double dx = 1.0 / NSTEPS;
double pi = 0.0;
double start_time = omp_get_wtime();
#pragma omp parallel for
for (i = 0; i < NSTEPS; i++)
{
double x = (i + 0.5) * dx;
double tmp = 1.0 / (1.0 + x * x);
#pragma omp atomic
pi = pi + tmp;
}
pi *= 4.0 * dx;
double run_time = omp_get_wtime() - start_time;
double ref_pi = 4.0 * atan(1.0);
printf("pi with %d steps is %.10f in %.6f seconds (error=%e)\n",
NSTEPS, pi, run_time, fabs(ref_pi - pi));
}
int
main(int argc, char** argv)
{
for(int i=0; i<ITERS; i++){
printf("\n\n");
printf("============================\n");
printf("Test - Iteration %d...\n", i);
printf("============================\n");
start_stats();
exercise();
collect_stats();
}
printf("\n\n");
printf("============================\n");
printf("Statistics\n");
printf("============================\n");
print_stats();
return 0;
}