1 /* Test of rounding towards negative infinity.
2 Copyright (C) 2007-2010 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 <http://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. */
31 #include "isnand-nolibm.h"
35 /* The reference implementation, taken from lib/floor.c. */
38 #define MANT_DIG DBL_MANT_DIG
39 #define L_(literal) literal
42 static const DOUBLE TWO_MANT_DIG =
43 /* Assume MANT_DIG <= 5 * 31.
45 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
46 (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
47 * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
48 * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
49 * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
50 * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
53 floor_reference (DOUBLE x)
55 /* The use of 'volatile' guarantees that excess precision bits are dropped
56 at each addition step and before the following comparison at the caller's
57 site. It is necessary on x86 systems where double-floats are not IEEE
58 compliant by default, to avoid that the results become platform and compiler
59 option dependent. 'volatile' is a portable alternative to gcc's
60 -ffloat-store option. */
61 volatile DOUBLE y = x;
62 volatile DOUBLE z = y;
66 /* For 0 < x < 1, return +0.0 even if the current rounding mode is
70 /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */
71 else if (z < TWO_MANT_DIG)
73 /* Round to the next integer (nearest or up or down, doesn't matter). */
76 /* Enforce rounding down. */
83 /* Work around ICC's desire to optimize denormal floats to 0. */
86 /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */
87 if (z > - TWO_MANT_DIG)
89 /* Round to the next integer (nearest or up or down, doesn't matter). */
92 /* Enforce rounding down. */
101 /* Test for equality. */
103 equal (DOUBLE x, DOUBLE y)
105 return (isnand (x) ? isnand (y) : x == y);
108 /* Test whether the result for a given argument is correct. */
110 correct_result_p (DOUBLE x, DOUBLE result)
113 (x < 0 && x >= -1 ? result == - L_(1.0) :
114 x - 1 < x ? result <= x && result >= x - 1 && x - result < 1 :
118 /* Test the function for a given argument. */
122 /* If the reference implementation is incorrect, bail out immediately. */
123 double reference = floor_reference (x);
124 ASSERT (correct_result_p (x, reference));
125 /* If the actual implementation is wrong, return an error code. */
127 double result = floor (x);
128 if (correct_result_p (x, result))
132 #if GNULIB_TEST_FPRINTF_POSIX
133 fprintf (stderr, "floor %g(%a) = %g(%a) or %g(%a)?\n",
134 x, x, reference, reference, result, result);
141 #define NUM_HIGHBITS 15
142 #define NUM_LOWBITS 4
148 unsigned int highbits;
149 unsigned int lowbits;
151 for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
152 for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
154 /* Combine highbits and lowbits into a floating-point number,
155 sign-extending the lowbits to 64-NUM_HIGHBITS bits. */
156 union { double f; uint64_t i; } janus;
157 janus.i = ((uint64_t) highbits << (64 - NUM_HIGHBITS))
158 | ((uint64_t) ((int64_t) ((uint64_t) lowbits << (64 - NUM_LOWBITS))
159 >> (64 - NUM_LOWBITS - NUM_HIGHBITS))
161 error |= check (janus.f);
163 return (error ? 1 : 0);
165 fprintf (stderr, "Skipping test: no 64-bit integer type available\n");