Eve_math_sigmoid

Detailed Description

Variables
constexpr auto	eve::sigmoid = functor<sigmoid_t>
	elementwise_callable object computing the sigmoid (logistic function).

Variable Documentation

sigmoid

auto eve::sigmoid = functor<sigmoid_t>

inlineconstexpr

elementwise_callable object computing the sigmoid (logistic function).

Header file

#include <eve/module/math.hpp>

Callable Signatures

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

Parameters

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

Return value

1. Returns the elementwise sigmoid of the input. In particular:
   • If the element is \(1/2\), \(1\) is returned
   • If the element is \(-\infty\), \(+0\) is returned
   • If the element is \(\infty\), \(1\) is returned
   • If the element is a NaN, NaN is returned
2. The operation is performed conditionally.

External references

• Wolfram MathWorld
• Wikipedia

Example

// revision 1
#include <eve/module/math.hpp>
#include <iostream>
 
int main()
{
  eve::wide wf = {0.0f, -0.0f, -1.0f, 1.0f, 2.0f,
                  eve::inf(eve::as<float>()), eve::minf(eve::as<float>()), eve::nan(eve::as<float>())};
 
  std::cout << "<- wf                         = " << wf << "\n";
 
  std::cout << "-> sigmoid(wf)                = " << eve::sigmoid(wf) << "\n";
  std::cout << "-> sigmoid[ignore_last(2)](wf)= " << eve::sigmoid[eve::ignore_last(2)](wf) << "\n";
  std::cout << "-> sigmoid[wf != 2.0f](wf)    = " << eve::sigmoid[wf != 2.0f](wf) << "\n";
}