average

eve::average = {}

inlineconstexpr

Computes the arithmetic mean of its arguments.

Defined in Header

#include <eve/module/core.hpp>

Callable Signatures

namespace eve
{
   template< eve::value T, eve::value U >
   eve::common_compatible_t<T, U> average(T x, U y) noexcept;
 
   template< eve::floating_value Ts ... >
   eve::common_compatible_t<Ts ...> average(Ts ... xs) noexcept;
}

Parameters

• x, y: real or complex arguments.
• xs... : floating or complex arguments.

Return value

The value of the arithmetic mean of the arguments is returned.

Note

• For two parameters half the sum of x and y. No overflow occurs.
• For more than two parameters only floating or complex entries are allowed. No overflow occurs.
• If x and y are integral values and the sum is odd, the result is a rounded value at a distance guaranteed to be less than or equal to 0.5 of the average floating value, but may differ by unity from the truncation given by (x+y)/2. Moreover, as some architectures provide simd intrinsics to perform the operation, the scalar results may differ by one unit from simd ones which are system dependent.

Example

#include <eve/module/core.hpp>
#include <eve/wide.hpp>
#include <vector>
#include <iostream>
 
float mean(std::vector<float>  ary) {
  float avg = 0;
  int t = 1;
  for (float x : ary) {
    avg += (x - avg) / t;
    ++t;
  }
  return avg;
}
 
int main()
{
  using w_t = eve::wide<std::uint32_t, eve::fixed<4>>;
  w_t pi = {3, 2, 3, 3}, qi = {4, 1, 1, ~0};
 
  std::cout << "---- simd" << '\n'
            << " <- pi              = " << pi << '\n'
            << " <- qi              = " << qi << '\n'
            << " -> average(pi, qi) = " << eve::average(pi, qi) << '\n';
 
  std::uint32_t xi = 3, yi = 4;
 
  std::cout << "---- scalar" << '\n'
            << " xi                 = " << xi << '\n'
            << " yi                 = " << yi << '\n'
            << " -> average(xi, yi) = " << eve::average(xi, yi) << '\n';
 
  using w_ft = eve::wide<float, eve::fixed<4>>;
  w_ft pf = {3, 4, 3, 10}, qf = {4, 1, 1, 15};;
  std::cout << "---- multi" << '\n'
            << " <- pf                               = " << pf << '\n'
            << " <- qf                               = " << qf << '\n'
            << " -> average(pf, 0.0f, qf, pf, 11.0f) = " << eve::average(pf, 0.0f, qf, pf, 11.0f) <<  '\n';
 
  std::cout << "---- multi parameters" << '\n';
  return 0;
}

Semantic Modifiers

• Masked Call

  The call eve::average[mask](x, ...) provides a masked version of average which is equivalent to if_else(mask, average(x, ...), x)

  Example

  #include <eve/module/core.hpp>
  #include <eve/wide.hpp>
  #include <vector>
  #include <iostream>
   
   
  int main()
  {
    using w_t = eve::wide<std::uint32_t, eve::fixed<4>>;
    w_t pi = {3, 2, 3, 3}, qi = {4, 1, 1, ~0};
   
    std::cout << "---- simd" << '\n'
              << " <- pi              = " << pi << '\n'
              << " <- qi              = " << qi << '\n'
              << " -> average[pi > qi](pi, qi) = " << eve::average[pi > qi](pi, qi) << '\n';
    return 0;
  }

• eve::raw

  when raw(average)(x, args, ...) is used, no provision is made to avoid overflows for more than 2 parameters.

  Example

  #include <eve/module/core.hpp>
  #include <eve/wide.hpp>
  #include <vector>
  #include <iostream>
   
  int main()
  {
    using w_t = eve::wide<float, eve::fixed<4>>;
    w_t pi = {3, 2, 3, 3},
        qi = {4, 1, 1, eve::valmax(eve::as<float>())},
        ri = {4, 1, 1, eve::valmax(eve::as<float>())};
   
    std::cout << "---- simd" << '\n'
              << " <- pi                       = " << pi << '\n'
              << " <- qi                       = " << qi << '\n'
              << " <- ri                       = " << ri << '\n'
              << " -> raw(average)(pi, qi, ri) = " << eve::raw(eve::average)(pi, qi, ri) << '\n'
              << " -> average(pi, qi, ri)      = " << eve::average(pi, qi, ri) << '\n';
   
    return 0;
  }