9.2
general documentation
cs_debug.h
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1#ifndef CS_DEBUG_H
2#define CS_DEBUG_H
3
4/*============================================================================
5 * Debug macros and utilities
6 *============================================================================*/
7
8/*
9 This file is part of code_saturne, a general-purpose CFD tool.
10
11 Copyright (C) 1998-2026 EDF S.A.
12
13 This program is free software; you can redistribute it and/or modify it under
14 the terms of the GNU General Public License as published by the Free Software
15 Foundation; either version 2 of the License, or (at your option) any later
16 version.
17
18 This program is distributed in the hope that it will be useful, but WITHOUT
19 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
20 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
21 details.
22
23 You should have received a copy of the GNU General Public License along with
24 this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
25 Street, Fifth Floor, Boston, MA 02110-1301, USA.
26*/
27
28/*----------------------------------------------------------------------------*/
29
30#if defined(HAVE_MPI)
31#include <mpi.h>
32#endif
33
34/*----------------------------------------------------------------------------
35 * Local headers
36 *----------------------------------------------------------------------------*/
37
38#include "base/cs_defs.h"
39
40/*=============================================================================
41 * Macro definitions
42 *============================================================================*/
43
44/*============================================================================
45 * Type definitions
46 *============================================================================*/
47
48/*=============================================================================
49 * Global variables
50 *============================================================================*/
51
52/*=============================================================================
53 * Public function prototypes
54 *============================================================================*/
55
56/*=============================================================================
57 * Templated function definitions
58 *============================================================================*/
59
60/* Compute the unit in the last place (ULP) */
61template <class T>
62typename std::enable_if<!std::numeric_limits<T>::is_integer, T>::type
63cs_diff_ulp(T x,
64 T y)
65{
66 // Since `epsilon()` is the gap size (ULP, unit in the last place)
67 // of floating-point numbers in interval [1, 2), we can scale it to
68 // the gap size in interval [2^e, 2^{e+1}), where `e` is the exponent
69 // of `x` and `y`.
70
71 // If `x` and `y` have different gap sizes (which means they have
72 // different exponents), we take the smaller one. Taking the bigger
73 // one is also reasonable, I guess.
74 const T m = fmin(std::fabs(x), std::fabs(y));
75
76 // Subnormal numbers have fixed exponent, which is `min_exponent - 1`.
77 const int exp = m < std::numeric_limits<T>::min()
78 ? std::numeric_limits<T>::min_exponent - 1
79 : std::ilogb(m);
80
81 // We divide the absolute difference by
82 // the epsilon times the exponent (1 ulp)
83 return std::fabs(x - y) / std::ldexp(std::numeric_limits<T>::epsilon(), exp);
84}
85
86/*----------------------------------------------------------------------------*/
87
88#endif /* CS_DEBUG_H */
cs_diff_ulp
std::enable_if<!std::numeric_limits< T >::is_integer, T >::type cs_diff_ulp(T x, T y)
Definition: cs_debug.h:63
cs_defs.h
cs::min
CS_F_HOST_DEVICE T min(const T a, const T b)
Definition: cs_defs.h:712