Printing decimal precision upto desiired number in cpp-CodePudding

I have an application I want to print the precision of the calculated prime number up to the desired number. But the number is omitted on the terminal as shown below.

The code I used for this is as

 int  main ()
{
    cout << "Enter the precision for calculation" << endl;
    long num_steps ;
    cin >> num_steps ;
    cout << "Precision = " << num_steps << endl;

    double step;
    double  x=0.0, pi, sum = 0.0;

    cout << "Enter the number of CPU core involved in calculation" << endl;
    int numberOfCpuCore = 0;
    cin >> numberOfCpuCore;

    int i;

    step = 1.0l/( double) num_steps;


        }
    pi = step * sum;
    printf("Pi value = %.10le\n", pi);
return 0;

}

My question is how can I print the precision to the desired number as entered from the command line.

CodePudding user response：

use iomanip. first add #include <iomanip> and then std::setprecision(num_steps) like this :

#include <cstdio>
#include <iostream>
#include <iomanip>
using namespace std;

int  main()
{
    cout << "Enter the precision for calculation" << endl;
    long  num_steps;
    cin >> num_steps;
    cout << "Precision = " << num_steps << endl;

    double  step;
    double  x = 0.0, pi, sum = 0.0;

    cout << "Enter the number of CPU core involved in calculation" << endl;
    int  numberOfCpuCore = 0;
    cin >> numberOfCpuCore;

    int  i;

    step = 1.0l / (double)num_steps;

#pragma omp parallel for reduction( :sum) num_threads(numberOfCpuCore) private(x)

    for (i = 0; i < num_steps; i  )
    {
        x   = (i   0.5) * step;
        sum = sum   4.0 / (1.0   x * x);
// int threadId = omp_get_thread_num();
// printf("Thread index =%i, Pi value in thread = %le\n", threadId, sum);
    }

    pi = step * sum;

    cout << "Pi value =" << std::setprecision(num_steps) << pi << endl;
// printf("Pi value = %.10le\n", pi);

    return 0;
}

this will the output: