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// -*-C++-*-
#ifndef MATHFUNCS_EXP_H
#define MATHFUNCS_EXP_H
#include "mathfuncs_base.h"
#include <cassert>
#include <cmath>
namespace vecmathlib {
template<typename realvec_t>
realvec_t mathfuncs<realvec_t>::vml_exp2(realvec_t x)
{
// Rescale
realvec_t x0 = x;
realvec_t round_x = round(x);
x -= round_x;
intvec_t iround_x = convert_int(round_x);
// Approximate
assert(all(x >= RV(-0.5) && x <= RV(0.5)));
// exp(x) = Sum[n=0,nmax] x^n / n!
int const nmax = 15;
x *= RV(M_LN2);
realvec_t y = x; // x^n / n!
realvec_t r = RV(1.0) + y;
for (int n=2; n<nmax; ++n) {
y *= x * RV(R(1.0) / R(n));
r += y;
}
// Undo rescaling
r = ifthen(x0 < RV(R(FP::min_exponent)), RV(0.0), scalbn(r, iround_x));
return r;
}
template<typename realvec_t>
inline
realvec_t mathfuncs<realvec_t>::vml_exp(realvec_t x)
{
return exp2(RV(M_LOG2E) * x);
}
template<typename realvec_t>
inline
realvec_t mathfuncs<realvec_t>::vml_exp10(realvec_t x)
{
return exp(RV(M_LN10) * x);
}
template<typename realvec_t>
inline
realvec_t mathfuncs<realvec_t>::vml_expm1(realvec_t x)
{
return exp(x) - RV(1.0);
#if 0
r = exp(x) - RV(1.0);
return ifthen(r == RV(0.0), x, r);
#endif
}
}; // namespace vecmathlib
#endif // #ifndef MATHFUNCS_EXP_H
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