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math-util: introduce iszero_safe() and fp_equal()

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This commit is contained in:
Yu Watanabe 2022-07-19 04:28:57 +09:00
parent 39229a2a0e
commit fbccfa95c4
4 changed files with 130 additions and 0 deletions
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14
src/basic/math-util.h Normal file
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@ -0,0 +1,14 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include <math.h>
#include "macro.h"
/* On some optimization level, iszero(x) is converted to (x == 0.0), and emits warning -Wfloat-equal.
* The argument must be a floating point, i.e. one of float, double, or long double. */
#define iszero_safe(x) (fpclassify(x) == FP_ZERO)
/* To avoid x == y and triggering compile warning -Wfloat-equal. This retuns false if one of the argument is
* NaN or infinity. One of the argument must be a floating point. */
#define fp_equal(x, y) iszero_safe((x) - (y))

1
src/basic/meson.build
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@ -129,6 +129,7 @@ basic_sources = files(
'login-util.c',
'login-util.h',
'macro.h',
'math-util.h',
'memfd-util.c',
'memfd-util.h',
'memory-util.c',

4
src/test/meson.build
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@ -209,6 +209,10 @@ tests += [
[files('test-macro.c')],
[files('test-math-util.c'),
[],
[libm]],
[files('test-mkdir.c')],
[files('test-json.c'),

111
src/test/test-math-util.c Normal file
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@ -0,0 +1,111 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <float.h>
#include "math-util.h"
#include "tests.h"
TEST(iszero_safe) {
/* zeros */
assert_se(iszero_safe(0.0));
assert_se(iszero_safe(-0.0));
assert_se(iszero_safe(0e0));
assert_se(iszero_safe(-0e0));
assert_se(iszero_safe(0e+0));
assert_se(iszero_safe(0e-0));
assert_se(iszero_safe(-0e-0));
assert_se(iszero_safe(-0e000));
assert_se(iszero_safe(0e000));
/* non-zero normal values */
assert_se(!iszero_safe(42.0));
assert_se(!iszero_safe(M_PI));
assert_se(!iszero_safe(DBL_MAX));
assert_se(!iszero_safe(-DBL_MAX));
assert_se(!iszero_safe(DBL_MIN));
assert_se(!iszero_safe(-DBL_MIN));
assert_se(!iszero_safe(1 / DBL_MAX));
/* subnormal values */
assert_se(!iszero_safe(DBL_MIN / 2));
assert_se(!iszero_safe(-DBL_MIN / 42));
assert_se(!iszero_safe(1 / DBL_MAX / 2));
/* too small values which cannot be in subnormal form */
assert_se( iszero_safe(DBL_MIN / DBL_MAX));
assert_se( iszero_safe(DBL_MIN / -DBL_MAX));
assert_se( iszero_safe(-DBL_MIN / DBL_MAX));
assert_se( iszero_safe(-DBL_MIN / -DBL_MAX));
/* NaN or infinity */
assert_se(!iszero_safe(NAN));
assert_se(!iszero_safe(INFINITY));
assert_se(!iszero_safe(-INFINITY));
assert_se(!iszero_safe(1 / NAN));
/* inverse of infinity */
assert_se( iszero_safe(1 / INFINITY));
assert_se( iszero_safe(1 / -INFINITY));
assert_se( iszero_safe(-1 / INFINITY));
assert_se( iszero_safe(-1 / -INFINITY));
assert_se( iszero_safe(42 / -INFINITY));
assert_se( iszero_safe(-42 / -INFINITY));
assert_se( iszero_safe(DBL_MIN / INFINITY));
assert_se( iszero_safe(DBL_MIN / -INFINITY));
assert_se( iszero_safe(DBL_MAX / INFINITY / 2));
assert_se( iszero_safe(DBL_MAX / -INFINITY * DBL_MAX));
assert_se(!iszero_safe(DBL_MAX * 2 / INFINITY));
/* infinity / infinity is NaN */
assert_se(!iszero_safe(INFINITY / INFINITY));
assert_se(!iszero_safe(INFINITY * 2 / INFINITY));
assert_se(!iszero_safe(INFINITY / DBL_MAX / INFINITY));
}
TEST(fp_equal) {
/* normal values */
assert_se( fp_equal(0.0, -0e0));
assert_se( fp_equal(3.0, 3));
assert_se(!fp_equal(3.000001, 3));
assert_se( fp_equal(M_PI, M_PI));
assert_se(!fp_equal(M_PI, -M_PI));
assert_se( fp_equal(DBL_MAX, DBL_MAX));
assert_se(!fp_equal(DBL_MAX, -DBL_MAX));
assert_se(!fp_equal(-DBL_MAX, DBL_MAX));
assert_se( fp_equal(-DBL_MAX, -DBL_MAX));
assert_se( fp_equal(DBL_MIN, DBL_MIN));
assert_se(!fp_equal(DBL_MIN, -DBL_MIN));
assert_se(!fp_equal(-DBL_MIN, DBL_MIN));
assert_se( fp_equal(-DBL_MIN, -DBL_MIN));
/* subnormal values */
assert_se( fp_equal(DBL_MIN / 10, DBL_MIN / 10));
assert_se(!fp_equal(DBL_MIN / 10, -DBL_MIN / 10));
assert_se(!fp_equal(-DBL_MIN / 10, DBL_MIN / 10));
assert_se( fp_equal(-DBL_MIN / 10, -DBL_MIN / 10));
assert_se(!fp_equal(DBL_MIN / 10, DBL_MIN / 15));
assert_se(!fp_equal(DBL_MIN / 10, DBL_MIN / 15));
/* subnormal difference */
assert_se(!fp_equal(DBL_MIN / 10, DBL_MIN + DBL_MIN / 10));
assert_se( fp_equal(3.0, 3.0 + DBL_MIN / 2)); /* 3.0 + DBL_MIN / 2 is truncated to 3.0 */
/* too small values */
assert_se( fp_equal(DBL_MIN / DBL_MAX, -DBL_MIN / DBL_MAX));
/* NaN or infinity */
assert_se(!fp_equal(NAN, NAN));
assert_se(!fp_equal(NAN, 0));
assert_se(!fp_equal(NAN, INFINITY));
assert_se(!fp_equal(INFINITY, INFINITY));
assert_se(!fp_equal(INFINITY, -INFINITY));
assert_se(!fp_equal(-INFINITY, INFINITY));
assert_se(!fp_equal(-INFINITY, -INFINITY));
/* inverse of infinity */
assert_se( fp_equal(0, 1 / INFINITY));
assert_se( fp_equal(42 / INFINITY, 1 / -INFINITY));
assert_se(!fp_equal(42 / INFINITY, INFINITY / INFINITY));
}
DEFINE_TEST_MAIN(LOG_DEBUG);