C / C ++：1.00000 <= 1.0f =假

本文介绍了C / C ++：1.00000 <= 1.0f =假的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 有人可以解释为什么1.000000 Can someone explain why 1.000000 <= 1.0f is false?代码：#include <iostream>#include <stdio.h>using namespace std;int main(int argc, char **argv){ float step = 1.0f / 10; float t; for(t = 0; t <= 1.0f; t += step) { printf("t = %f\n", t); cout << "t = " << t << "\n"; cout << "(t <= 1.0f) = " << (t <= 1.0f) << "\n"; } printf("t = %f\n", t ); cout << "t = " << t << "\n"; cout << "(t <= 1.0f) = " << (t <= 1.0f) << "\n"; cout << "\n(1.000000 <= 1.0f) = " << (1.000000 <= 1.0f) << "\n";}结果：t = 0.000000t = 0(t <= 1.0f) = 1t = 0.100000t = 0.1(t <= 1.0f) = 1t = 0.200000t = 0.2(t <= 1.0f) = 1t = 0.300000t = 0.3(t <= 1.0f) = 1t = 0.400000t = 0.4(t <= 1.0f) = 1t = 0.500000t = 0.5(t <= 1.0f) = 1t = 0.600000t = 0.6(t <= 1.0f) = 1t = 0.700000t = 0.7(t <= 1.0f) = 1t = 0.800000t = 0.8(t <= 1.0f) = 1t = 0.900000t = 0.9(t <= 1.0f) = 1t = 1.000000t = 1(t <= 1.0f) = 0(1.000000 <= 1.0f) = 1 推荐答案正如在注释中正确指出的， t 的值实际上并不是你在 1.00000 As correctly pointed out in the comments, the value of t is not actually the same 1.00000 that you are defining in the line below.使用 std :: setprecision（20）以更高的精度打印t将显示其实际值： 1.0000001192092895508 。Printing t with higher precision with std::setprecision(20) will reveal its actual value: 1.0000001192092895508.避免这类问题的常见方法是不与 1 ，但是使用 1 + epsilon ，其中epsilon是一个非常小的数字，也许是一个或两个大于您的浮点精度。The common way to avoid these kinds of issues is to compare not with 1, but with 1 + epsilon, where epsilon is a very small number, that is maybe one or two magnitudes greater than your floating point precision.所以你可以写你的for循环条件为So you would write your for loop condition asfor(t = 0; t <= 1.000001f; t += step) $ b Note that in your case, epsilon should be atleast ten times greater than the maximum possible floating point error, as the float is added ten times.如Muepe和Alain所指出的， t！= 1.0f的原因是 1/10 无法用二进制浮点数精确表示。As pointed out by Muepe and Alain, the reason for t != 1.0f is that 1/10 can not be precisely represented in binary floating point numbers. 这篇关于C / C ++：1.00000 <= 1.0f =假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！