src/gromacs/math/utilities.cpp

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  37 #include "gmxpre.h"
  38
  39 #include "utilities.h"
  40
  41 #include "config.h"
  42
  43 #include <cassert>
  44 #include <climits>
  45 #include <cmath>
  46
  47 #include <algorithm>
  48
  49 #include <cfenv>
  50
  51 //! Floating point exception set that we use and care about
  52 constexpr int c_FPexceptions = FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW;
  53
  54 bool
  55 gmx_within_tol(double   f1,
  56                double   f2,
  57                double   tol)
  58 {
  59     /* The or-equal is important - otherwise we return false if f1==f2==0 */
  60     return fabs(f1-f2) <= tol*0.5*(fabs(f1)+fabs(f2));
  61 }
  62
  63 int
  64 gmx_numzero(double a)
  65 {
  66     return gmx_within_tol(a, 0.0, GMX_REAL_MIN/GMX_REAL_EPS);
  67 }
  68
  69
  70 gmx_bool
  71 check_int_multiply_for_overflow(int64_t  a,
  72                                 int64_t  b,
  73                                 int64_t *result)
  74 {
  75     int64_t sign = 1;
  76     if ((0 == a) || (0 == b))
  77     {
  78         *result = 0;
  79         return TRUE;
  80     }
  81     if (a < 0)
  82     {
  83         a    = -a;
  84         sign = -sign;
  85     }
  86     if (b < 0)
  87     {
  88         b    = -b;
  89         sign = -sign;
  90     }
  91     if (INT64_MAX / b < a)
  92     {
  93         *result = (sign > 0) ? INT64_MAX : INT64_MIN;
  94         return FALSE;
  95     }
  96     *result = sign * a * b;
  97     return TRUE;
  98 }
  99
 100 int gmx_greatest_common_divisor(int p, int q)
 101 {
 102     int tmp;
 103     while (q != 0)
 104     {
 105         tmp = q;
 106         q   = p % q;
 107         p   = tmp;
 108     }
 109     return p;
 110 }
 111
 112 int gmx_feenableexcept()
 113 {
 114 #if HAVE_FEENABLEEXCEPT
 115     return feenableexcept(c_FPexceptions);
 116 #elif (defined(__i386__) || defined(__x86_64__)) && defined(__APPLE__)
 117     /* Author:  David N. Williams
 118      * License:  Public Domain
 119      *
 120      * Might also work on non-Apple Unix. But should be tested
 121      * before enabling.
 122      */
 123     static fenv_t fenv;
 124     unsigned int  new_excepts = c_FPexceptions & FE_ALL_EXCEPT;
 125
 126     if (fegetenv (&fenv) )
 127     {
 128         return -1;
 129     }
 130
 131     // unmask
 132     fenv.__control &= ~new_excepts;
 133     fenv.__mxcsr   &= ~(new_excepts << 7);
 134
 135     return fesetenv(&fenv);
 136 #else
 137     return -1;
 138 #endif
 139 }
 140
 141 int gmx_fedisableexcept()
 142 {
 143 #if HAVE_FEDISABLEEXCEPT
 144     return fedisableexcept(c_FPexceptions);
 145 #elif (defined(__i386__) || defined(__x86_64__)) && defined(__APPLE__)
 146     static fenv_t fenv;
 147     unsigned int  new_excepts = c_FPexceptions & FE_ALL_EXCEPT;
 148     if (fegetenv (&fenv) )
 149     {
 150         return -1;
 151     }
 152
 153     // mask
 154     fenv.__control |= new_excepts;
 155     fenv.__mxcsr   |= new_excepts << 7;
 156
 157     return fesetenv(&fenv);
 158 #else
 159     return -1;
 160 #endif
 161 }
 162
 163 real max_cutoff(real cutoff1, real cutoff2)
 164 {
 165     if (cutoff1 == 0 || cutoff2 == 0)
 166     {
 167         return 0;
 168     }
 169     else
 170     {
 171         return std::max(cutoff1, cutoff2);
 172     }
 173 }