1 /*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright © 2019 Keith Packard
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above
14 * copyright notice, this list of conditions and the following
15 * disclaimer in the documentation and/or other materials provided
16 * with the distribution.
17 *
18 * 3. Neither the name of the copyright holder nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
31 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
33 * OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35 #define _DEFAULT_SOURCE
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <math.h>
39 #include <stdbool.h>
40
41 bool
near(double got,double target,double close)42 near(double got, double target, double close)
43 {
44 if (got < target - close)
45 return false;
46 if (got > target + close)
47 return false;
48 return true;
49 }
50
51 int
main(void)52 main(void)
53 {
54 int i;
55 int ret = 0;
56 double s1 = 0;
57 double s2 = 0;
58 #define N 100000
59 for (i = 0; i < N; i++) {
60 double d = drand48();
61 s1 += d;
62 s2 += d*d;
63 }
64 double mean = s1 / N;
65 double stddev = sqrt((N * s2 - s1*s1) / ((double) N * ((double) N - 1)));
66 if (!near(mean, .5, .1)) {
67 printf("bad mean %g\n", mean);
68 ret = 1;
69 }
70 if (!near(stddev, .28, .1)) {
71 printf("bad stddev %g\n", stddev);
72 ret = 2;
73 }
74 fflush(stdout);
75 return ret;
76 }
77
