双重计算问题 [英] double calculation issue

问题描述

您好，在我的C ++代码中，我有2个双变量，其值分别为.4和.1


当我从.4中减去.1时，我得到的值是.30000000004.请问为什么编译器给出了这样的值以及如何解决这个问题.


例如代码

double d = .4;
double dec = .1

double result =  d- dec;

因此，当我从.1中减去.1时，我得到的是.00000000027而不是zeo.它们存储在二进制文件中.这意味着以10为底的精确数字在以2为底的数字中不是那么精确:

在此处 [

如果计算精度很重要，建议您编写或找到一个使用整数分子和分母处理有理数的类.这样，您就可以消除舍入误差，或者至少推迟舍入误差直到出现.

对float或double的100％精度计算是不可能的，而且永远不可能.你必须忍受那个.

阅读该书以了解浮点运算的工作原理:
http://en.wikipedia.org/wiki/Floating_point [ 解决方案

It happens because numbers aren''t stored in base ten - they are stored in binary. This means that what is a precise number is base 10 is not so precise in base 2:

There is a guide to the details here[^] which explains it better than I could: see about half way down under "Converting Decimal Fractions to Binary Reals"

If calculation accuracy is important, I suggest you write or find a class that handles rational numbers, using an integer numerator and denominator. That way you can rid yourself of, or a least postpone, the rounding error until presentation.

100% precision computation on float or double are not possible and will never be. You have to live with that.

Read that to understand how floating point operations work:
http://en.wikipedia.org/wiki/Floating_point[^]

If you don''t want any rounding errors, then I suggest you to work with int, long, or int64 types.

这篇关于双重计算问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！