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/*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright © 2019 Keith Packard
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* 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.
*/
#define _DEFAULT_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
static bool
near(double got, double target, double close)
{
if (got < target - close)
return false;
if (got > target + close)
return false;
return true;
}
static double
random_double(void)
{
return (double)random() / 0x7fffffffL;
}
static double
rand_double(void)
{
return (double)rand() / RAND_MAX;
}
static const struct {
char *name;
double (*func)(void);
double mean_err;
double stddev_err;
} funcs[] = {
{
.name = "drand48",
.func = drand48,
.mean_err = 0.01,
.stddev_err = 0.02,
},
{
.name = "random",
.func = random_double,
.mean_err = 0.01,
.stddev_err = 0.02,
},
{
.name = "rand",
.func = rand_double,
.mean_err = 0.01,
.stddev_err = 0.02,
},
};
int
main(void)
{
int32_t i;
int ret = 0;
unsigned f;
for (f = 0; f < sizeof(funcs) / sizeof(funcs[0]); f++) {
double s1 = 0;
double s2 = 0;
int pass = 1;
#define N 1000
printf("Testing %s...", funcs[f].name);
fflush(stdout);
for (i = 0; i < N; i++) {
double d = funcs[f].func();
s1 += d;
s2 += d * d;
}
double mean = s1 / N;
double stddev = sqrt((N * s2 - s1 * s1) / ((double)N * ((double)N - 1)));
if (!near(mean, .5, funcs[f].mean_err)) {
printf(" bad mean %g", mean);
ret = 1;
pass = 0;
}
if (!near(stddev, .28, funcs[f].stddev_err)) {
printf(" bad stddev %g", stddev);
ret = 2;
pass = 0;
}
if (pass)
printf(" pass");
printf("\n");
}
return ret;
}
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