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 #include <stdint.h>
41
42 static bool
near(double got,double target,double close)43 near(double got, double target, double close)
44 {
45 if (got < target - close)
46 return false;
47 if (got > target + close)
48 return false;
49 return true;
50 }
51
52 int
main(void)53 main(void)
54 {
55 int32_t i;
56 int ret = 0;
57 double s1 = 0;
58 double s2 = 0;
59 #define N 100000
60 for (i = 0; i < N; i++) {
61 double d = drand48();
62 s1 += d;
63 s2 += d*d;
64 }
65 double mean = s1 / N;
66 double stddev = sqrt((N * s2 - s1*s1) / ((double) N * ((double) N - 1)));
67 if (!near(mean, .5, .1)) {
68 printf("bad mean %g\n", mean);
69 ret = 1;
70 }
71 if (!near(stddev, .28, .1)) {
72 printf("bad stddev %g\n", stddev);
73 ret = 2;
74 }
75 fflush(stdout);
76 return ret;
77 }
78
