expl: Work around inaccurate implementation on NetBSD.
[gnulib.git] / tests / test-ceil2.c
blobef48437b1808d65e1ef5a4b1011c6d6c59803f40
1 /* Test of rounding towards positive infinity.
2 Copyright (C) 2007-2019 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17 /* Written by Bruno Haible <bruno@clisp.org>, 2007. */
19 /* When this test fails on some platform, build it together with the gnulib
20 module 'fprintf-posix' for optimal debugging output. */
22 #include <config.h>
24 #include <math.h>
26 #include <float.h>
27 #include <stdbool.h>
28 #include <stdint.h>
29 #include <stdio.h>
31 #include "isnand-nolibm.h"
32 #include "minus-zero.h"
33 #include "macros.h"
35 /* MSVC with option -fp:strict refuses to compile constant initializers that
36 contain floating-point operations. Pacify this compiler. */
37 #ifdef _MSC_VER
38 # pragma fenv_access (off)
39 #endif
42 /* The reference implementation, taken from lib/ceil.c. */
44 #define DOUBLE double
45 #define MANT_DIG DBL_MANT_DIG
46 #define L_(literal) literal
48 /* -0.0. See minus-zero.h. */
49 #define MINUS_ZERO minus_zerod
51 /* 2^(MANT_DIG-1). */
52 static const DOUBLE TWO_MANT_DIG =
53 /* Assume MANT_DIG <= 5 * 31.
54 Use the identity
55 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
56 (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
57 * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
58 * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
59 * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
60 * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
62 DOUBLE
63 ceil_reference (DOUBLE x)
65 /* The use of 'volatile' guarantees that excess precision bits are dropped
66 at each addition step and before the following comparison at the caller's
67 site. It is necessary on x86 systems where double-floats are not IEEE
68 compliant by default, to avoid that the results become platform and compiler
69 option dependent. 'volatile' is a portable alternative to gcc's
70 -ffloat-store option. */
71 volatile DOUBLE y = x;
72 volatile DOUBLE z = y;
74 if (z > L_(0.0))
76 /* Work around ICC's desire to optimize denormal floats to 0. */
77 if (z < DBL_MIN)
78 return L_(1.0);
79 /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */
80 if (z < TWO_MANT_DIG)
82 /* Round to the next integer (nearest or up or down, doesn't matter). */
83 z += TWO_MANT_DIG;
84 z -= TWO_MANT_DIG;
85 /* Enforce rounding up. */
86 if (z < y)
87 z += L_(1.0);
90 else if (z < L_(0.0))
92 /* For -1 < x < 0, return -0.0 regardless of the current rounding
93 mode. */
94 if (z > L_(-1.0))
95 z = MINUS_ZERO;
96 /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */
97 else if (z > - TWO_MANT_DIG)
99 /* Round to the next integer (nearest or up or down, doesn't matter). */
100 z -= TWO_MANT_DIG;
101 z += TWO_MANT_DIG;
102 /* Enforce rounding up. */
103 if (z < y)
104 z += L_(1.0);
107 return z;
111 /* Test for equality. */
112 static int
113 equal (DOUBLE x, DOUBLE y)
115 return (isnand (x) ? isnand (y) : x == y);
118 /* Test whether the result for a given argument is correct. */
119 static bool
120 correct_result_p (DOUBLE x, DOUBLE result)
122 return
123 (x > 0 && x <= 1 ? result == L_(1.0) :
124 x + 1 > x ? result >= x && result <= x + 1 && result - x < 1 :
125 equal (result, x));
128 /* Test the function for a given argument. */
129 static int
130 check (double x)
132 /* If the reference implementation is incorrect, bail out immediately. */
133 double reference = ceil_reference (x);
134 ASSERT (correct_result_p (x, reference));
135 /* If the actual implementation is wrong, return an error code. */
137 double result = ceil (x);
138 if (correct_result_p (x, result))
139 return 0;
140 else
142 #if GNULIB_TEST_FPRINTF_POSIX
143 fprintf (stderr, "ceil %g(%a) = %g(%a) or %g(%a)?\n",
144 x, x, reference, reference, result, result);
145 #endif
146 return 1;
151 #define NUM_HIGHBITS 12
152 #define NUM_LOWBITS 4
155 main ()
157 unsigned int highbits;
158 unsigned int lowbits;
159 int error = 0;
160 for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
161 for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
163 /* Combine highbits and lowbits into a floating-point number,
164 sign-extending the lowbits to 64-NUM_HIGHBITS bits. */
165 union { double f; uint64_t i; } janus;
166 janus.i = ((uint64_t) highbits << (64 - NUM_HIGHBITS))
167 | ((uint64_t) ((int64_t) ((uint64_t) lowbits << (64 - NUM_LOWBITS))
168 >> (64 - NUM_LOWBITS - NUM_HIGHBITS))
169 >> NUM_HIGHBITS);
170 error |= check (janus.f);
172 return (error ? 1 : 0);