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