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 <assert.h>
  44 #include <limits.h>
  45
  46 #include <cmath>
  47
  48 #include <algorithm>
  49
  50 #include <cfenv>
  51
  52 //! Floating point exception set that we use and care about
  53 constexpr int c_FPexceptions = FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW;
  54
  55 int
  56 gmx_within_tol(double   f1,
  57                double   f2,
  58                double   tol)
  59 {
  60     /* The or-equal is important - otherwise we return false if f1==f2==0 */
  61     if (fabs(f1-f2) <= tol*0.5*(fabs(f1)+fabs(f2)) )
  62     {
  63         return 1;
  64     }
  65     else
  66     {
  67         return 0;
  68     }
  69 }
  70
  71 int
  72 gmx_numzero(double a)
  73 {
  74     return gmx_within_tol(a, 0.0, GMX_REAL_MIN/GMX_REAL_EPS);
  75 }
  76
  77
  78 gmx_bool
  79 check_int_multiply_for_overflow(gmx_int64_t  a,
  80                                 gmx_int64_t  b,
  81                                 gmx_int64_t *result)
  82 {
  83     gmx_int64_t sign = 1;
  84     if ((0 == a) || (0 == b))
  85     {
  86         *result = 0;
  87         return TRUE;
  88     }
  89     if (a < 0)
  90     {
  91         a    = -a;
  92         sign = -sign;
  93     }
  94     if (b < 0)
  95     {
  96         b    = -b;
  97         sign = -sign;
  98     }
  99     if (GMX_INT64_MAX / b < a)
 100     {
 101         *result = (sign > 0) ? GMX_INT64_MAX : GMX_INT64_MIN;
 102         return FALSE;
 103     }
 104     *result = sign * a * b;
 105     return TRUE;
 106 }
 107
 108 int gmx_greatest_common_divisor(int p, int q)
 109 {
 110     int tmp;
 111     while (q != 0)
 112     {
 113         tmp = q;
 114         q   = p % q;
 115         p   = tmp;
 116     }
 117     return p;
 118 }
 119
 120 int gmx_feenableexcept()
 121 {
 122 #if HAVE_FEENABLEEXCEPT
 123     return feenableexcept(c_FPexceptions);
 124 #elif (defined(__i386__) || defined(__x86_64__)) && defined(__APPLE__)
 125     /* Author:  David N. Williams
 126      * License:  Public Domain
 127      *
 128      * Might also work on non-Apple Unix. But should be tested
 129      * before enabling.
 130      */
 131     static fenv_t fenv;
 132     unsigned int  new_excepts = c_FPexceptions & FE_ALL_EXCEPT;
 133
 134     if (fegetenv (&fenv) )
 135     {
 136         return -1;
 137     }
 138
 139     // unmask
 140     fenv.__control &= ~new_excepts;
 141     fenv.__mxcsr   &= ~(new_excepts << 7);
 142
 143     return fesetenv(&fenv);
 144 #else
 145     return -1;
 146 #endif
 147 }
 148
 149 int gmx_fedisableexcept()
 150 {
 151 #if HAVE_FEDISABLEEXCEPT
 152     return fedisableexcept(c_FPexceptions);
 153 #elif (defined(__i386__) || defined(__x86_64__)) && defined(__APPLE__)
 154     static fenv_t fenv;
 155     unsigned int  new_excepts = c_FPexceptions & FE_ALL_EXCEPT;
 156     if (fegetenv (&fenv) )
 157     {
 158         return -1;
 159     }
 160
 161     // mask
 162     fenv.__control |= new_excepts;
 163     fenv.__mxcsr   |= new_excepts << 7;
 164
 165     return fesetenv(&fenv);
 166 #else
 167     return -1;
 168 #endif
 169 }
 170
 171 real max_cutoff(real cutoff1, real cutoff2)
 172 {
 173     if (cutoff1 == 0 || cutoff2 == 0)
 174     {
 175         return 0;
 176     }
 177     else
 178     {
 179         return std::max(cutoff1, cutoff2);
 180     }
 181 }