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/*******************************************************
* Copyright (c) 2014, ArrayFire
* All rights reserved.
*
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
* http://arrayfire.com/licenses/BSD-3-Clause
********************************************************/
/*
monte-carlo estimation of PI
algorithm:
- generate random (x,y) samples uniformly
- count what percent fell inside (top quarter) of unit circle
*/
#include <stdio.h>
#include <math.h>
#include <cstdlib>
#include <arrayfire.h>
using namespace af;
// generate millions of random samples
static int samples = 20e6;
/* Self-contained code to run host and device estimates of PI. Note that
each is generating its own random values, so the estimates of PI
will differ. */
static double pi_device()
{
array x = randu(samples,f32), y = randu(samples,f32);
return 4.0 * sum<float>(sqrt(x*x + y*y) < 1) / samples;
}
static double pi_host()
{
int count = 0;
for (int i = 0; i < samples; ++i) {
float x = float(rand()) / RAND_MAX;
float y = float(rand()) / RAND_MAX;
if (sqrt(x*x + y*y) < 1)
count++;
}
return 4.0 * count / samples;
}
// void wrappers for timeit()
static void device_wrapper() { pi_device(); }
static void host_wrapper() { pi_host(); }
int main(int argc, char ** argv)
{
try {
int device = argc > 1 ? atoi(argv[1]) : 0;
setDevice(device);
info();
printf("device: %.5f seconds to estimate pi = %.5f\n", timeit(device_wrapper), pi_device());
printf(" host: %.5f seconds to estimate pi = %.5f\n", timeit(host_wrapper), pi_host());
} catch (exception& e) {
fprintf(stderr, "%s\n", e.what());
throw;
}
return 0;
}
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