1.计算目标
使用200-bit的精度计算1+1/1!+1/2!+...+1/100!
2.编写程序
#include <stdio.h>
#include <mpfr.h>
int main (void)
{
mpfr_t s, t, u;
unsigned int i;
mpfr_init2(t, 200); //初始化变量为200-bit精度
mpfr_set_d(t, 1.0, MPFR_RNDD); //设置t=1.0
mpfr_init2(s, 200);
mpfr_set_d(s, 1.0, MPFR_RNDD);
mpfr_init2(u, 200);
for(i = 1; i <= 100; i++)
{
mpfr_mul_ui(t, t, i, MPFR_RNDU); //设置t=t*i
mpfr_set_d(u, 1.0, MPFR_RNDD); //设置u=1.0
mpfr_div(u, u, t, MPFR_RNDD); //设置u=u/t
mpfr_add(s, s, u, MPFR_RNDD); //设置s=s+u
}
printf("Sum is ");
mpfr_out_str(stdout, 10, 0, s, MPFR_RNDD); //输出变量s的值
putchar('\n');
mpfr_clear(s); //释放mpfr_t类型变量s
mpfr_clear(t);
mpfr_clear(u);
mpfr_free_cache(); //释放mpfr缓存
return 0;
}
3.编译程序
$ gcc -o example example.c -lmpfr -lgmp
4.运行程序
$ ./example
5.显示结果
Sum is 2.7182818284590452353602874713526624977572470936999595749669131
