计算圆周率PI

• 服务器地址 172.16.192.24

• 用户名 2019301110060

• 计算圆周率

#include <time.h>
    #include <stdio.h>
    double step;
    int main(){
        static long num_steps;
        printf("请输入一个1000以上的数字求取PI值\n>>");
        scanf("%ld",&num_steps);
        clock_t start_t, end_t;
        double total_t;
        int i;
        double x,pi,sum =0.0;
        start_t = clock();
        step=1.0/(double)num_steps; //将1平分成100000步
        for(i=1;i<=num_steps;i++){
            x=(i-0.5)*step;//获得0-1的连续值
            sum+=4.0/(1.0+x*x);
        }
        pi =step * sum; //
        end_t = clock();
        total_t=(double)(end_t - start_t)/CLOCKS_PER_SEC;
        printf("运行时间为%fs\t%.10f\r\n",total_t,pi);
        return 0;

    }

• 加上时间和精度的控制

  #include <time.h>
  #include <stdio.h>
  double step;
  int main()
  {
      static long num_steps;
      // printf("请输入一个1000以上的数字求取PI值\n>>");
      // scanf("%ld",&num_steps);
      for (num_steps = 1000000; num_steps <= 10000000; num_steps += 100000)
      {
          int index;
          index = ((double)num_steps - 1000000) / 100000 + 4;
          clock_t start_t, end_t;
          double total_t;
          int i;
          double x, pi, sum = 0.0;
          start_t = clock();
          step = 1.0 / (double)num_steps; //将1平分成100000步
          for (i = 1; i <= num_steps; i++)
          {
              x = (i - 0.5) * step; //获得0-1的连续值
              sum += 4.0 / (1.0 + x * x);
          }
          pi = step * sum; //
          end_t = clock();
          total_t = (double)(end_t - start_t) / CLOCKS_PER_SEC;
          printf("运行时间为%fs\t%.*f\r\n", total_t, pi, index);
      }
      return 0;
  }

• 输出结果

  运行时间为0.020000s    3.1416
  运行时间为0.020000s    3.14159
  运行时间为0.010000s    3.141593
  运行时间为0.020000s    3.1415927
  运行时间为0.020000s    3.14159265
  运行时间为0.030000s    3.141592654
  运行时间为0.020000s    3.1415926536
  运行时间为0.030000s    3.14159265359
  运行时间为0.020000s    3.141592653590
  运行时间为0.030000s    3.1415926535899
  运行时间为0.030000s    3.14159265358999
  运行时间为0.030000s    3.141592653589834
  运行时间为0.040000s    3.1415926535896115
  运行时间为0.030000s    3.14159265358955730
  运行时间为0.040000s    3.141592653589722062
  运行时间为0.040000s    3.1415926535897442662
  运行时间为0.030000s    3.14159265358982242589
  运行时间为0.040000s    3.141592653589698969085
  运行时间为0.050000s    3.1415926535897624738425
  运行时间为0.040000s    3.14159265358961103942192
  运行时间为0.050000s    3.141592653589609707154295
  运行时间为0.040000s    3.1415926535896288029903189
  运行时间为0.050000s    3.14159265358963946113135535
  运行时间为0.050000s    3.141592653589633687971627296
  运行时间为0.050000s    3.1415926535896367965960962465
  运行时间为0.050000s    3.14159265358973316395463371009
  运行时间为0.060000s    3.141592653589739825292781461030
  运行时间为0.060000s    3.1415926535896865345875994535163
  运行时间为0.050000s    3.14159265358964034930977504700422
  运行时间为0.060000s    3.141592653589700301353104805457406
  运行时间为0.060000s    3.1415926535896829818739206530153751
  运行时间为0.070000s    3.14159265358976158566406411409843713
  运行时间为0.060000s    3.141592653590072448110959157929755747
  运行时间为0.060000s    3.1415926535893832216572718607494607568
  运行时间为0.070000s    3.14159265358984018945420757518149912357
  运行时间为0.070000s    3.141592653589813544101616571424528956413