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