[英]Why does this result in 0 and upsidedown not?
Currently I am writing my thesis and I was confronted with a behavior of .Net C# that I had never seen before. 目前,我正在写论文,而且遇到了从未见过的.Net C#行为。 I am talking about an error in a calculation.
我说的是计算中的错误。 I implemented this formula:
我实现了这个公式:
1/2 * (Theta i-1 + Theta i) + Sum(Alph k, k=1, i-1) 1/2 *(Theta i-1 + Theta i)+ Sum(Alph k,k = 1,i-1)
This formula is applied to 4 objects. 此公式适用于4个对象。 Theta is in all objects declared as float with the value 1,5708.
Theta在所有声明为float的对象中,其值为1,5708。 Alpha is initialized with 0 and will be increased by each iteration.
Alpha初始化为0,并且每次迭代都会增加。
First implmentation 第一次实施
float alpha = 0;
float value = 0;
for (int sphereCount = 1; sphereCount < this.spheres.Count; sphereCount++)
{
value = (1/2) * (this.spheres[sphereCount - 1].Theta + this.spheres[sphereCount].Theta);
alpha += value;
}
With this version value is always 0.0! 使用此版本值始终为0.0! So I changed it to:
所以我将其更改为:
Working implementaion 工作实施
float alpha = 0;
float value = 0;
for (int sphereCount = 1; sphereCount < this.spheres.Count; sphereCount++)
{
value =(this.spheres[sphereCount - 1].Theta + this.spheres[sphereCount].Theta) * 1/2;
alpha += value;
}
By removing the brackets around the 1/2 and placing it at the end of the calculation it worked. 通过移除1/2周围的括号并将其放在计算的末尾,它可以正常工作。
WHY IS THAT SO??? 为什么会这样???
It seems when you place 1/2 in brackets not depending on the position of 1/2 the result is 0.0. 似乎将1/2放在方括号中而不取决于1/2的位置时,结果是0.0。 But also when i place (1/2) at the end it results in 0.0.
而且当我将(1/2)放在最后时,它也会导致0.0。 Does anyone here have an idea why?
这里有人知道为什么吗?
This 这个
(1 / 2)
evaluates to 0 because it's integer division. 计算为0,因为它是整数除法。 If you say
如果你说
(1 / 2f)
or 要么
(1 / (float) 2)
you'll be fine because it forces float divsion. 您会好起来的,因为它会强制浮动除法。 Or, even better, just write
0.5
. 或者,甚至更好,只写
0.5
。
If you write 1/2 the result is calculated using integer division that gives an integer result. 如果您写1/2,则使用给出整数结果的整数除法来计算结果。 You can force a floating point division by changing one of the numbers to a floating point number, as in
1/2f
. 您可以通过将数字之一更改为浮点数来强制进行浮点除法,如
1/2f
。
Or you could just write 0.5
which IMHO is more readable than 1/2. 或者,您可以只写
0.5
,恕我直言,它比1/2更易读。
Why multiply by 1
? 为什么要乘以
1
? Rather than this: 而不是这样:
value =(this.spheres[sphereCount - 1].Theta + this.spheres[sphereCount].Theta) * 1/2;
why not write this: 为什么不这样写:
value =(this.spheres[sphereCount - 1].Theta + this.spheres[sphereCount].Theta) / 2;
You should write 1.0/2 or 0.5 instead 1/2. 您应该写1.0 / 2或0.5而不是1/2。
1/2 is an integer division which results in an integer 0. 1/2是一个整数除法,得出整数0。
Because 1/2 is treated as integer arithmetic and as such is rounded to 0. 因为1/2被视为整数算术,因此四舍五入为0。
Removing the parenthesis changes the order of operations, and now you are dividing your whole (floating point) formula by two and arriving at a floating point answer. 删除括号会更改操作顺序,现在您将整个(浮点)公式除以二,得出一个浮点答案。
That's because 1
and 2
are integer values, not floating point values. 这是因为
1
和2
是整数值,而不是浮点值。
When you divide the integer value 1
by the integer value 2
, the result is the integer value 0
, not the floating point value 0.5
. 当您将整数值
1
除以整数值2
,结果是整数值0
,而不是浮点值0.5
。
When you remove the parentheses and change the order of the multiplication, the other part of the expression will first be multiplied by 1
, which will implicitly convert the integer value 1
into a floating point value. 当您删除括号并更改乘法顺序时,表达式的另一部分将首先乘以
1
,这将隐式将整数值1
转换为浮点值。 Then the result is divided by 2
, which will also be implicitly converted into a floating point value. 然后将结果除以
2
,这也将隐式转换为浮点值。
So what you end up doing is: 因此,您最终要做的是:
value = ( (this.spheres[sphereCount - 1].Theta + this.spheres[sphereCount].Theta) * (float)1 ) / (float)2;
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