mersenne_twister_engine类的问题 [英] Issues with c++ 11 mersenne_twister_engine class
问题描述
我一直在尝试使用c ++ 11 mersenne_twister_engine类( http://www.cplusplus .com / reference / random / mersenne_twister_engine / )在区间[0,1]中生成数字,但是我在每个数字上不断得到0。
I have been trying to use the c++ 11 mersenne_twister_engine class( http://www.cplusplus.com/reference/random/mersenne_twister_engine/) to generate numbers in the interval [0,1] however I am continually getting 0 on every number.
这是我的代码片段
unsigned seed1 = std::chrono::system_clock::now().time_since_epoch().count();
std::mt19937 generator(seed1);
for (int i=0; i < WIDTH * HEIGHT; i++) //GENERATES THE MATRIX OF CONNECTIVITY
{
double random = generator()/generator.max();
if ( random > VERT_CONNECTIVITY )
vert_con[i] = 0;
else vert_con[i] = 1;
}
generator )似乎是工作...它只是随机,给我0!
generator() and generator.max() seem to be working... It is just random which gives me 0!
谢谢!
推荐答案
在C ++中, /
在整数上产生一个整数。例如11/2得到5,而不是5.5。同样, a / b
如果 a < b
In C++, /
on integer numbers results in an integer number. For example 11 / 2 results in 5, not 5.5. In the same way a / b
is always zero if a < b
.
您的问题在这里:
generator()/generator.max()
和 generator.max()
都返回整数,当然, generator.max()> = generator
,因此结果为零(除非您非常幸运得到 max
数字,在这种情况下结果将是一个)。
generator()
and generator.max()
both return integers and of course, generator.max() >= generator()
, so the result is zero (unless you are very lucky to get the max
number in which case the result would be one).
要解决这个问题,您可以简单地转换:
To fix this, you can simply cast it:
(double)generator()/generator.max()
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