math4610

Homework, Material, and Software Manual for Math 4610

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Double Precision Machine Epsilon

Routine Name: dmaceps

Author: Tanner Wheeler

Language: C. The code can be compiled using the GNU gcc compiler (gcc).

For example,

gcc smaceps.c -o MachineEps

will produce an executable which can be run by

./MachineEps

Description/Purpose: This routine will compute the double precision value for the machine epsilon.

Input: There are no inputs needed.

Output: This routine returns an integer value of the double precision value for the machine epsilon.

Usage/Example: This function must be called from the main function or another function. For example:

int main()
{
  int precision = dmaceps();
  
  printf("%i\n", precision);
  
  return 0;
}

This code will print

53 (or some other number depending on the machine)

to the console.

Implementation/Code: The following is the code for dmaceps()

int dmaceps(){
    float one = 1.0;
    double seps = 1.0;
    double appone = one + seps;

    int power = 0;

    double test = fabs(appone - one);
    while(test != 0.0)
    {
        power = power + 1;

        seps = seps / 2;
        appone = one + seps;

        test = fabs(appone - one);
    }
    
    return power;
}

Last Modified: September/2018