/* * 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 #include #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 #include #include #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 reduction(+ \ : pi) for (i = 0; i < NSTEPS; i++) { double x = (i + 0.5) * dx; pi += 1.0 / (1.0 + x * x); } pi *= 4.0 * dx; double run_time = omp_get_wtime() - start_time; double ref_pi = 4.0 * atan(1.0); printf("pi with %ld steps is %.10f in %.6f seconds (error=%e)\n", NSTEPS, pi, run_time, fabs(ref_pi - pi)); }