src/gromacs/math/utilities.h

   1 /*
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  37 #ifndef GMX_MATH_UTILITIES_H
  38 #define GMX_MATH_UTILITIES_H
  39
  40 #include <limits.h>
  41 #include <math.h>
  42
  43 #include "gromacs/utility/basedefinitions.h"
  44 #include "gromacs/utility/real.h"
  45
  46 #ifdef __cplusplus
  47 extern "C" {
  48 #endif
  49
  50 #ifndef M_PI
  51 #define M_PI        3.14159265358979323846
  52 #endif
  53
  54 #ifndef M_PI_2
  55 #define M_PI_2      1.57079632679489661923
  56 #endif
  57
  58 #ifndef M_2PI
  59 #define M_2PI       6.28318530717958647692
  60 #endif
  61
  62 #ifndef M_SQRT2
  63 #define M_SQRT2 sqrt(2.0)
  64 #endif
  65
  66 #ifndef M_1_PI
  67 #define M_1_PI      0.31830988618379067154
  68 #endif
  69
  70 #ifndef M_FLOAT_1_SQRTPI /* used in GPU kernels */
  71 /* 1.0 / sqrt(M_PI) */
  72 #define M_FLOAT_1_SQRTPI 0.564189583547756f
  73 #endif
  74
  75 #ifndef M_1_SQRTPI
  76 /* 1.0 / sqrt(M_PI) */
  77 #define M_1_SQRTPI 0.564189583547756
  78 #endif
  79
  80 #ifndef M_2_SQRTPI
  81 /* 2.0 / sqrt(M_PI) */
  82 #define M_2_SQRTPI  1.128379167095513
  83 #endif
  84
  85 int     gmx_nint(real a);
  86 real    sign(real x, real y);
  87
  88 real    cuberoot (real a);
  89 double  gmx_erfd(double x);
  90 double  gmx_erfcd(double x);
  91 float   gmx_erff(float x);
  92 float   gmx_erfcf(float x);
  93 #ifdef GMX_DOUBLE
  94 #define gmx_erf(x)   gmx_erfd(x)
  95 #define gmx_erfc(x)  gmx_erfcd(x)
  96 #else
  97 #define gmx_erf(x)   gmx_erff(x)
  98 #define gmx_erfc(x)  gmx_erfcf(x)
  99 #endif
 100
 101 #if defined(_MSC_VER) && _MSC_VER < 1800
 102 #define gmx_expm1(x) (exp(x)-1)
 103 #define gmx_log1p(x) log(1+x)
 104 #else
 105 #define gmx_expm1 expm1
 106 #define gmx_log1p log1p
 107 #endif
 108
 109 gmx_bool gmx_isfinite(real x);
 110 gmx_bool gmx_isnan(real x);
 111
 112 /*! \brief Check if two numbers are within a tolerance
 113  *
 114  *  This routine checks if the relative difference between two numbers is
 115  *  approximately within the given tolerance, defined as
 116  *  fabs(f1-f2)<=tolerance*fabs(f1+f2).
 117  *
 118  *  To check if two floating-point numbers are almost identical, use this routine
 119  *  with the tolerance GMX_REAL_EPS, or GMX_DOUBLE_EPS if the check should be
 120  *  done in double regardless of Gromacs precision.
 121  *
 122  *  To check if two algorithms produce similar results you will normally need
 123  *  to relax the tolerance significantly since many operations (e.g. summation)
 124  *  accumulate floating point errors.
 125  *
 126  *  \param f1  First number to compare
 127  *  \param f2  Second number to compare
 128  *  \param tol Tolerance to use
 129  *
 130  *  \return 1 if the relative difference is within tolerance, 0 if not.
 131  */
 132 int
 133 gmx_within_tol(double   f1,
 134                double   f2,
 135                double   tol);
 136
 137 /*!
 138  * \brief Check if a number is smaller than some preset safe minimum
 139  * value, currently defined as GMX_REAL_MIN/GMX_REAL_EPS.
 140  *
 141  * If a number is smaller than this value we risk numerical overflow
 142  * if any number larger than 1.0/GMX_REAL_EPS is divided by it.
 143  *
 144  * \return 1  if 'almost' numerically zero, 0 otherwise.
 145  */
 146 int
 147 gmx_numzero(double a);
 148
 149 /*! \brief Compute floor of logarithm to base 2
 150  *
 151  * \return log2(x)
 152  */
 153 unsigned int
 154 gmx_log2i(unsigned int x);
 155
 156 /*! \brief Multiply two large ints
 157  *
 158  * \return False iff overflow occured
 159  */
 160 gmx_bool
 161 check_int_multiply_for_overflow(gmx_int64_t  a,
 162                                 gmx_int64_t  b,
 163                                 gmx_int64_t *result);
 164
 165 /*! \brief Find greatest common divisor of two numbers
 166  *
 167  * \return GCD of the two inputs
 168  */
 169 int
 170 gmx_greatest_common_divisor(int p, int q);
 171
 172
 173 /*! \brief Enable floating-point exceptions if supported on OS
 174  *
 175  * Enables division-by-zero, invalid, and overflow.
 176  */
 177 int gmx_feenableexcept();
 178
 179 #ifdef __cplusplus
 180 }
 181 #endif
 182
 183 #endif