sigmoid equation compare

sigmoid_compare.cpp

#include <iostream>
#include <cmath>
#include <cfloat>

static float sigmoid1(float x) {
  return 1.0 / (1.0 + exp(-x));
}
static float sigmoid2(float x) {
  return exp(x) / (1.0 + exp(x));
}

int main(void) {
  float x, xarr[] = {FLT_MAX, 1000, 710, 709, 100, 89, 88, 10, 0, -10, -88, -89, -100, -709, -710, -1000, -FLT_MAX};
  for (int i = 0 ; i < sizeof(xarr)/sizeof(xarr[0]) ; i++) {
    x = xarr[i];
    std::cerr << "| " << x << " | ";
    std::cerr << exp(-x) << " | " << sigmoid1(x) << " | ";
    std::cerr << exp(x)  << " | " << sigmoid2(x) << " |" << std::endl;
  }
  return 0;
}