今天在根据需求写代码时候，偶尔发现linux 下 设置变量类型 float 和double 计算时，

得到的结果是不一样的。

要求： 设定值 = 传入值 * 10 * 122.88 /1000;

case： 设定值 = 1666*10*122.88/1000

= 2047.1808

设置成 float时，代码：

#include

#include

unsigned int fun(unsigned int sfn_threshold)

{

float f_sfn_threshold;

printf("input parameter=%d\n",sfn_threshold);

f_sfn_threshold = (float)sfn_threshold*1.2288;

printf("f_sfn_threshold = %8lf\n",f_sfn_threshold);

printf("%.8lf\n",fabs(f_sfn_threshold -(unsigned int)f_sfn_threshold ));

return 0;

}

int main(int argc, char **argv)

{

unsigned int a=1666;

unsigned int b=10000;

unsigned int c=12888;

unsigned int d=65535;

fun(a);

return 0;

}

执行结果(与要得到的结果不一致)：

[root@localhost test_float_compare]# gcc test_float_double_diff.c -o test_float_double_diff_1666

[root@localhost test_float_compare]#

[root@localhost test_float_compare]# ./test_float_double_diff_1666

input parameter=1666

f_sfn_threshold = 2047.180786

0.18078613

[root@localhost test_float_compare]#

设置成 double时，代码：

#include

#include

unsigned int fun(unsigned int sfn_threshold)

{

double f_sfn_threshold;

printf("input parameter=%d\n",sfn_threshold);

f_sfn_threshold = (double)sfn_threshold*1.2288;

printf("f_sfn_threshold = %8lf\n",f_sfn_threshold);

printf("%.8lf\n",fabs(f_sfn_threshold -(unsigned int)f_sfn_threshold ));

return 0;

}

int main(int argc, char **argv)

{

unsigned int a=1666;

unsigned int b=10000;

unsigned int c=12888;

unsigned int d=65535;

fun(a);

return 0;

}

执行结果：

[root@localhost test_float_compare]#

[root@localhost test_float_compare]# ./test_float_double_diff_1666

input parameter=1666

f_sfn_threshold = 2047.180800

0.18080000

[root@localhost test_float_compare]#