1// Licensed to the .NET Foundation under one or more agreements.
2// The .NET Foundation licenses this file to you under the MIT license.
3// See the LICENSE file in the project root for more information.
4
5/*=====================================================================
6**
7** Source: test1.c
8**
9** Purpose: Tests that log2 returns correct values.
10**
11**===================================================================*/
12
13#include <palsuite.h>
14
15// binary64 (double) has a machine epsilon of 2^-52 (approx. 2.22e-16). However, this
16// is slightly too accurate when writing tests meant to run against libm implementations
17// for various platforms. 2^-50 (approx. 8.88e-16) seems to be as accurate as we can get.
18//
19// The tests themselves will take PAL_EPSILON and adjust it according to the expected result
20// so that the delta used for comparison will compare the most significant digits and ignore
21// any digits that are outside the double precision range (15-17 digits).
22
23// For example, a test with an expect result in the format of 0.xxxxxxxxxxxxxxxxx will use
24// PAL_EPSILON for the variance, while an expected result in the format of 0.0xxxxxxxxxxxxxxxxx
25// will use PAL_EPSILON / 10 and and expected result in the format of x.xxxxxxxxxxxxxxxx will
26// use PAL_EPSILON * 10.
27#define PAL_EPSILON 8.8817841970012523e-16
28
29#define PAL_NAN sqrt(-1.0)
30#define PAL_POSINF -log(0.0)
31#define PAL_NEGINF log(0.0)
32
33/**
34 * Helper test structure
35 */
36struct test
37{
38 double value; /* value to test the function with */
39 double expected; /* expected result */
40 double variance; /* maximum delta between the expected and actual result */
41};
42
43/**
44 * validate
45 *
46 * test validation function
47 */
48void __cdecl validate(double value, double expected, double variance)
49{
50 double result = log2(value);
51
52 /*
53 * The test is valid when the difference between result
54 * and expected is less than or equal to variance
55 */
56 double delta = fabs(result - expected);
57
58 if (delta > variance)
59 {
60 Fail("log2(%g) returned %20.17g when it should have returned %20.17g",
61 value, result, expected);
62 }
63}
64
65/**
66 * validate
67 *
68 * test validation function for values returning NaN
69 */
70void __cdecl validate_isnan(double value)
71{
72 double result = log2(value);
73
74 if (!_isnan(result))
75 {
76 Fail("log2(%g) returned %20.17g when it should have returned %20.17g",
77 value, result, PAL_NAN);
78 }
79}
80
81/**
82 * main
83 *
84 * executable entry point
85 */
86int __cdecl main(int argc, char **argv)
87{
88 struct test tests[] =
89 {
90 /* value expected variance */
91 { 0, PAL_NEGINF, 0 },
92 { 0.11331473229676087, -3.1415926535897932, PAL_EPSILON * 10 }, // expected: -(pi)
93 { 0.15195522325791297, -2.7182818284590452, PAL_EPSILON * 10 }, // expected: -(e)
94 { 0.20269956628651730, -2.3025850929940457, PAL_EPSILON * 10 }, // expected: -(ln(10))
95 { 0.33662253682241906, -1.5707963267948966, PAL_EPSILON * 10 }, // expected: -(pi / 2)
96 { 0.36787944117144232, -1.4426950408889634, PAL_EPSILON * 10 }, // expected: -(log2(e))
97 { 0.37521422724648177, -1.4142135623730950, PAL_EPSILON * 10 }, // expected: -(sqrt(2))
98 { 0.45742934732229695, -1.1283791670955126, PAL_EPSILON * 10 }, // expected: -(2 / sqrt(pi))
99 { 0.5, -1, PAL_EPSILON * 10 }, // expected: -(1)
100 { 0.58019181037172444, -0.78539816339744831, PAL_EPSILON }, // expected: -(pi / 4)
101 { 0.61254732653606592, -0.70710678118654752, PAL_EPSILON }, // expected: -(1 / sqrt(2))
102 { 0.61850313780157598, -0.69314718055994531, PAL_EPSILON }, // expected: -(ln(2))
103 { 0.64321824193300488, -0.63661977236758134, PAL_EPSILON }, // expected: -(2 / pi)
104 { 0.74005557395545179, -0.43429448190325183, PAL_EPSILON }, // expected: -(log10(e))
105 { 0.80200887896145195, -0.31830988618379067, PAL_EPSILON }, // expected: -(1 / pi)
106 { 1, 0, PAL_EPSILON },
107 { 1.2468689889006383, 0.31830988618379067, PAL_EPSILON }, // expected: 1 / pi
108 { 1.3512498725672678, 0.43429448190325183, PAL_EPSILON }, // expected: log10(e)
109 { 1.5546822754821001, 0.63661977236758134, PAL_EPSILON }, // expected: 2 / pi
110 { 1.6168066722416747, 0.69314718055994531, PAL_EPSILON }, // expected: ln(2)
111 { 1.6325269194381528, 0.70710678118654752, PAL_EPSILON }, // expected: 1 / sqrt(2)
112 { 1.7235679341273495, 0.78539816339744831, PAL_EPSILON }, // expected: pi / 4
113 { 2, 1, PAL_EPSILON * 10 },
114 { 2.1861299583286618, 1.1283791670955126, PAL_EPSILON * 10 }, // expected: 2 / sqrt(pi)
115 { 2.6651441426902252, 1.4142135623730950, PAL_EPSILON * 10 }, // expected: sqrt(2)
116 { 2.7182818284590452, 1.4426950408889634, PAL_EPSILON * 10 }, // expected: log2(e) value: e
117 { 2.9706864235520193, 1.5707963267948966, PAL_EPSILON * 10 }, // expected: pi / 2
118 { 4.9334096679145963, 2.3025850929940457, PAL_EPSILON * 10 }, // expected: ln(10)
119 { 6.5808859910179210, 2.7182818284590452, PAL_EPSILON * 10 }, // expected: e
120 { 8.8249778270762876, 3.1415926535897932, PAL_EPSILON * 10 }, // expected: pi
121 { PAL_POSINF, PAL_POSINF, 0 },
122 };
123
124 if (PAL_Initialize(argc, argv) != 0)
125 {
126 return FAIL;
127 }
128
129 for (int i = 0; i < (sizeof(tests) / sizeof(struct test)); i++)
130 {
131 validate(tests[i].value, tests[i].expected, tests[i].variance);
132 }
133
134 validate_isnan(PAL_NEGINF);
135 validate_isnan(PAL_NAN);
136
137 PAL_Terminate();
138 return PASS;
139}
140