用C++程序找到Machine Epsilon

机器Epsilon是最小的EPS(ε)，因此1 + EPS不等于1。机器Epsilon是与机器相关的浮点值，由于浮点算术中的舍入，它提供了相对误差的上限。在数学上，对于每种浮点类型，它等于1.0与大于1.0的最小可表示值之间的差。

在C语言中，机器epsilon在标准标头中指定，名称为FLT_EPSILON，DBL_EPSILON和LDBL_EPSILON。这三个宏分别为浮点型，双精度型和长双精度型提供了机器epsilon。

在C++中，标准标头中提供了类似的宏。 C++中的首选方法是使用std :: numeric_limits :: epsilon()–在标准标头中指定。

在Java，它称为ULP(最后一个单位)。您可以使用Java.lang.Math包和Math.ulp()方法找到它。

在Python3中，该信息在sys.float_info中可用，该信息与C99中的float.h相对应。
这与std :: numeric_limits :: epsilon()的C++等效。
>>>导入系统
>>> sys.float_info.epsilon

CPP

// C++ program to find machine epsilon
#include
#include 
using namespace std;
  
// Function for Machine Epsilon with an
// initial value provided as EPS.
void machineEpsilon(float EPS)
{
    // taking a floating type variable
    float prev_epsilon;
  
    // run until condition satisfy
    while ((1+EPS) != 1)
    {
        // copying value of epsilon into previous epsilon
        prev_epsilon = EPS;
  
        // dividing epsilon by 2
        EPS /=2;
    }
  
    // print output of the program
    cout << "Machine Epsilon is : " << prev_epsilon << endl;
}
  
// Driver Code
int main()
{
    // calling function which calculate machine epsilon
    // with initial value provided as 0.5
    machineEpsilon(0.5);
  
    return 0;
}

Java

// Java program to find machine epsilon
  
import java.util.*;
  
class Count{
  
    // Function for Machine Epsilon with an
    // initial value provided as EPS.
  
    public static void machineEpsilon(double EPS)
    {
        // taking a floating type variable
        double prev_epsilon = 0.0;
   
        // run until condition satisfy
        while ((1+EPS) != 1)
        {
            // copying value of epsilon
            // into previous epsilon
            prev_epsilon = EPS;
   
            // dividing epsilon by 2
            EPS /=2;
        }
   
        // print output of the program
        System.out.print( "Machine Epsilon is : "
                         + prev_epsilon);
    }   
      
    public static void main(String[] args)
    {
        // calling function which
        // calculate machine epsilon
        // with initial value provided as 0.5
        machineEpsilon(0.5);
  
    }
}
  
// This code is contributed by rishabh_jain

Python3

# Python program to find machine epsilon
  
# Function for Machine Epsilon with an
# initial value provided as EPS.
def machineEpsilon(EPS):
  
    # taking a floating type variable
    # run until condition satisfy
    while ((1+EPS) != 1):
  
        # copying value of epsilon
        # into previous epsilon
        prev_epsilon = EPS
   
        # dividing epsilon by 2
        EPS = EPS / 2
   
    # print output of the program
    print( "Machine Epsilon is : " ,
            prev_epsilon )
  
# Driven code
# calling function which
# calculate machine epsilon
# with initial value provided as 0.5
machineEpsilon(0.5);
      
# This code is contributed by
# "rishabh_jain".

输出：

Machine Epsilon is : 1.19209e-07

请注意，以上结果因机器而异。

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