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#ifndef TNet_MathAux_h
#define TNet_MathAux_h
#include <cmath>
#if !defined(SQR)
# define SQR(x) ((x) * (x))
#endif
#if !defined(LOG_0)
# define LOG_0 (-1.0e10)
#endif
#if !defined(LOG_MIN)
# define LOG_MIN (0.5 * LOG_0)
#endif
#ifndef DBL_EPSILON
#define DBL_EPSILON 2.2204460492503131e-16
#endif
#ifndef M_PI
# define M_PI 3.1415926535897932384626433832795
#endif
#define M_LOG_2PI 1.8378770664093454835606594728112
#if DOUBLEPRECISION
# define FLOAT double
# define EPSILON DBL_EPSILON
# define FLOAT_FMT "%lg"
# define swapFLOAT swap8
# define _ABS fabs
# define _COS cos
# define _EXP exp
# define _LOG log
# define _SQRT sqrt
#else
# define FLOAT float
# define EPSILON FLT_EPSILON
# define FLOAT_FMT "%g"
# define swapFLOAT swap4
# define _ABS fabsf
# define _COS cosf
# define _EXP expf
# define _LOG logf
# define _SQRT sqrtf
#endif
namespace TNet
{
inline float frand(){ // random between 0 and 1.
return (float(rand()) + 1.0f) / (float(RAND_MAX)+2.0f);
}
inline float gauss_rand(){
return _SQRT( -2.0f * _LOG(frand()) ) * _COS(2.0f*float(M_PI)*frand());
}
static const double gMinLogDiff = log(DBL_EPSILON);
//***************************************************************************
//***************************************************************************
inline double
LogAdd(double x, double y)
{
double diff;
if (x < y) {
diff = x - y;
x = y;
} else {
diff = y - x;
}
double res;
if (x >= LOG_MIN) {
if (diff >= gMinLogDiff) {
res = x + log(1.0 + exp(diff));
} else {
res = x;
}
} else {
res = LOG_0;
}
return res;
}
//***************************************************************************
//***************************************************************************
inline double
LogSub(double x, double y) // returns exp(x) - exp(y). Throws exception if y>=x.
{
if(y >= x){
if(y==x) return LOG_0;
else throw std::runtime_error("LogSub: cannot subtract a larger from a smaller number.");
}
double diff = y - x; // Will be negative.
double res = x + log(1.0 - exp(diff));
if(res != res) // test for res==NaN.. could happen if diff ~0.0, so 1.0-exp(diff) == 0.0 to machine precision.
res = LOG_0;
return res;
}
} // namespace TNet
#endif
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