log_abs_gamma

auto eve::log_abs_gamma = functor<log_abs_gamma_t>

inlineconstexpr

Header file

#include <eve/module/special.hpp>

Callable Signatures

namespace eve
{
   // Regular overload
   constexpr auto log_abs_gamma(floating_value auto x)                          noexcept; // 1
 
   // Lanes masking
   constexpr auto log_abs_gamma[raw](floating_value auto x)                     noexcept; // 2
   constexpr auto log_abs_gamma[fast](floating_value auto x)                    noexcept; // 2
   constexpr auto log_abs_gamma[conditional_expr auto c](floating_value auto x) noexcept; // 3
   constexpr auto log_abs_gamma[logical_value auto m](floating_value auto x)    noexcept; // 3
}

Parameters

• x: floating argument.
• c: Conditional expression masking the operation.
• m: Logical value masking the operation.

Return value

1. the value of the logarithm of the absolute value of the \(\Gamma\) function is returned.
2. faster computations at accuracy price based on "An accurate approximation formula for gamma function" of Zhen-Hang Yang and Jing-Feng Tian.
3. The operation is performed conditionnaly.

External references

• [Wolfram MathWorld: Log Gamma Function](https://mathworld.wolfram.com/LogGammaFunction.html
• Zhen-Hang Yang & al.

Example

// revision 1
#include <eve/module/special.hpp>
#include <iostream>
 
int main()
{
  eve::wide wf = {0.5f, -1.5f, -1.0f, 1.0f, 5.0f,
                  eve::inf(eve::as<float>()), eve::minf(eve::as<float>()), eve::nan(eve::as<float>())};
 
  std::cout << "<- wf                                = " << wf << "\n";
 
  std::cout << "-> log_abs_gamma(wf)                 = " << eve::log_abs_gamma(wf) << "\n";
  std::cout << "-> log_abs_gamma[ignore_last(2)](wf) = " << eve::log_abs_gamma[eve::ignore_last(2)](wf) << "\n";
  std::cout << "-> log_abs_gamma[wf != 2.0f](wf)     = " << eve::log_abs_gamma[wf != 2.0f](wf) << "\n";
}