blocks|key|4097716|text|你多久播种一次随机？它应该只在程序开始时执行一次。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4097717|一旦播种了一个给定值，它将始终产生完全相同的序列。|4097718|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

How often are you seeding Random? It should be done only once at the start of the program. 

And once seeded with a given value, it will always produce the exact same sequence.

blocks|key|4097741|text|看看这个http://msdn.microsoft.com/en-us/library/system.random.aspx，它应该能解释为什么你会得到相同的值。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4097742|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.random.aspx^0|4|1M|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

have a look at this <a href="http://msdn.microsoft.com/en-us/library/system.random.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/system.random.aspx</a> it should explain why your getting the same value.

blocks|key|883904|text|.NET中的随机数生成器不是线程安全的。其他开发人员也注意到了同样的行为，一种解决方案如下(来自http://blogs.msdn.com/brada/archive/2003/08/14/50226.aspx)：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|883905|class+ThreadSafeRandom
{
++++private+static+Random+random+=+new+Random();

++++public+static+int+Next()
++++{
+++++++lock+(random)
+++++++{
+++++++++++return+random.Next();
+++++++}
++++}
}|code-block|syntax|javascript|883906|entityMap|0|LINK|mutability|MUTABLE|url|http://blogs.msdn.com/brada/archive/2003/08/14/50226.aspx^0|1C|1L|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

The random number generator in .NET is not thread safe. Other developers have noticed the same behaviour, and one solution is as follows (from <a href="http://blogs.msdn.com/brada/archive/2003/08/14/50226.aspx" rel="noreferrer"><a href="http://blogs.msdn.com/brada/archive/2003/08/14/50226.aspx" rel="noreferrer">http://blogs.msdn.com/brada/archive/2003/08/14/50226.aspx</a></a>):

<pre><code>class ThreadSafeRandom
{
 private static Random random = new Random();

 public static int Next()
 {
 lock (random)
 {
 return random.Next();
 }
 }
}</code></pre>

blocks|key|30518|text|Tomas，我以前遇到过这个"bug“，我的解决方案是让_rnd变量成为模块级的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|30519|Private+Shared+_rnd+As+System.Random()
Public+Shared+Function+RandRange(ByVal+low+As+Integer,+ByVal+high+As+Integer)+As+Integer
++++If+_rnd+Is+Nothing+Then
++++++++_rnd+=+New+System.Random()
++++End+If
++++Return+rnd.Next(low,+high)
End+Function|code-block|syntax|javascript|30520|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Tomas, I ran into this "bug" before and the solution for me was to make the _rnd variable module-level:

<pre><code>Private Shared _rnd As System.Random()
Public Shared Function RandRange(ByVal low As Integer, ByVal high As Integer) As Integer
 If _rnd Is Nothing Then
 _rnd = New System.Random()
 End If
 Return rnd.Next(low, high)
End Function
</code></pre>

blocks|key|883929|text|其他人已经做了很好的工作来解释它并提供解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|883930|无论如何，Erik之前已经回答过一个类似的问题，请查看它：|offset|length|883931|Pseudo+Random+Generator+with+same+output|883932|您还可以在以下位置获得与该主题(随机数生成器)相关的更多问题和答案：|883933|Stackoverflow.com+random-number-generator|883934|基因|883935|附言:这只是对公认答案的补充。|883936|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/16942/erik|1|https://stackoverflow.com/questions/239063/pseudo-random-generator-with-same-output|2|https://stackoverflow.com/questions/tagged/random-number-generator^0|0|5|4|0|0|0|14|1|0|0|0|15|2|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@$D|13|E|14|1|15]]|A|$]]|$1|F|3|G|5|6|7|16|8|@]|9|@$D|17|E|18|1|19]]|A|$]]|$1|H|3|I|5|6|7|1A|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1B|8|@]|9|@$D|1C|E|1D|1|1E]]|A|$]]|$1|L|3|M|5|6|7|1F|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1G|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]|X|$5|S|T|U|A|$V|Y]]|Z|$5|S|T|U|A|$V|10]]]]

Other folks have already done a decent job explaining it and providing solutions.

Anyway, a similiar question has been answered before by <a href="https://stackoverflow.com/users/16942/erik">Erik</a>, check it out:

<a href="https://stackoverflow.com/questions/239063/pseudo-random-generator-with-same-output">Pseudo Random Generator with same output</a>

You also get more questions and answers related to the topic (Random Number Generators) at:

<a href="https://stackoverflow.com/questions/tagged/random-number-generator">Stackoverflow.com random-number-generator</a>

Gene

P.S. This is just to supplement the accepted answer.

I am using a System.Random object which is instantiated with a fixed seed all thoughout the application. I am calling the NextDouble method and after some time passed I am getting 0.0 as result.

Is there any remedy to this, has anyone else encountered this ?

EDIT: I have one seed for the whole run which is set to 1000 for convience sake. The random.NextDouble is called several hundred thousand times. It is an optimizer application and could run for couple hours, but this actually happens after 10-0 mins of execution. I have recently added little bit more random calls to the app.

System.Random keeps on returning the same value

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用的是一个System.Random对象，它是通过一个固定的种子实例化的，所有这些都考虑了应用程序。我正在调用NextDouble方法，经过一段时间后，我得到的结果是0.0。有什么办法解决这个问题吗?有没有其他人遇到过这个问题？编辑:为了方便起见，我在整个运行过程中只有一个种子设置为1000。random.Next...

问System.Random一直返回相同的值
EN

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问System.Random一直返回相同的值EN