actualy it was a good idea as well thank you
On 22 יוני, 15:59, "Lee Gunn" <[email protected]> wrote: > Hi, > > The problem is arising because the "Random" class is being instantiated > everytime the foo() method is called. And, as mentioned below, becuase the > code is running so fast the default seed used (current datetime) is the same. > To get round this, simply use a ** static ** "Random" object. There will be > only one instance of it and you can quite happily keep calling Next() to > generate a new unique random number... > > Lee > > --http://www.secretorange.co.uk > > > > -----Original Message----- > From: [email protected] on behalf of Cerebrus > Sent: Mon 22/06/2009 11:21 > To: DotNetDevelopment, VB.NET, C# .NET, ADO.NET, ASP.NET, XML, XML Web > Services,.NET Remoting > Subject: [DotNetDevelopment] Re: intefrace > > Your code functions correctly. The only problem arises from the fact > that the Random object does not generate truly random numbers (It's a > pseudo-random generator). However, the Random class allows you to > generate sufficiently random sequences for this purpose by providing a > unique seed value. > > There are many ways to generate this unique seed. In the below code, I > demonstrate three of them : > > 1. Use a value that depends on the current time. However, since your > loop runs so fast, the system time does not change significantly > enough for seed values to change. Therefore, we must apply a trick... > we must simulate a delay so that the time changes. I do this by > setting the current thread to sleep for a very minimal time (so as not > to affect program performance significantly). This is demonstrated by > the function "SleepingWithRandom" in the code sample. > > 2. Use the loop counter as the seed value, since it is guaranteed to > be unique for each iteration. This is demonstrated by the function > "LoopingRandom" in the code sample. > > 3. Use a seed value derived from the loop value. If it is even, apply > a bitwise complement of the current time (in ticks), else not. This > would greatly increase the probability that the seed value generated > is unique even for the same time. This is demonstrated by the function > "ComplementingRandom" in the code sample. > > The code: (Syntax highlighted version available at: <http:// > dotnetdevelopment.pastebin.com/m5236e4af>) > > --- > using System; > using System.Threading; > > interface IFoo > { > void foo(int a, int b); > } > > class Factory : IFoo > { > private enum Operation > { > add = 1, > subtract = 2, > multiply = 3, > divide = 4, > } > > private int _a, _b; > private int randomSeed = 0; > > public virtual void foo(int a, int b) > { > > this._a = a; > this._b = b; > > Random rand = new Random(randomSeed); > > Operation op = (Operation)rand.Next(1, 5); > > switch (op) > { > case Operation.add: > plus(); > break; > case Operation.subtract: > minus(); > break; > case Operation.multiply: > multiplier(); > break; > case Operation.divide: > dividor(); > break; > } > > //if (rand.Next(4) % 4 == 0) > // plus(); > //else if (rand.Next() % 4 == 1) > // minus(); > //else if (rand.Next() % 4 == 2) > // dividor(); > //else multiplier(); > } > > public void plus() > { > Console.WriteLine("{0}+{1}={2}", _a, _b, _a + _b); > } > > public void minus() > { > Console.WriteLine("{0}-{1}={2}", _a, _b, _a - _b); > } > > public void dividor() > { > Console.WriteLine("{0}/{1}={2}", _a, _b, _a / _b); > } > > public void multiplier() > { > Console.WriteLine("{0}*{1}={2}", _a, _b, _a * _b); > } > > public int RandomSeed > { > set { randomSeed = value; } > } > > } > class MainClass > { > static void Main(string[] args) > { > IFoo[] df = new IFoo[10]; > for (int i = 0; i < 10; i++) > { > Factory f = new Factory(); > > // Uncomment only one of the below 3 approaches at a time: > //SleepingWithRandom(ref f, i); > LoopingRandom(ref f, i); > //ComplementingRandom(ref f, i); > > df[i] = f; > } > } > > private static void SleepingWithRandom(ref Factory f, int i) > { > // Generate a seed from the current time and set the seed value of > the Random to be created. > f.RandomSeed = unchecked((int)(DateTime.Now.Ticks)); > f.foo(i + 1, i + 1); > > // Initiate a delay so as to increase randomness. > Thread.Sleep(20); > } > > private static void LoopingRandom(ref Factory f, int i) > { > // Generate a different seed using the loop variable itself. > f.RandomSeed = i; > f.foo(i + 1, i + 1); > } > > private static void ComplementingRandom(ref Factory f, int i) > { > // Generate a different seed based on whether the loop variable is > even or odd. > if (i % 2 == 0) > f.RandomSeed = ~unchecked((int)(DateTime.Now.Ticks)); > else > f.RandomSeed = unchecked((int)(DateTime.Now.Ticks)); > > f.foo(i + 1, i + 1); > } > > } > > --- > I think the "LoopingRandom" method should be sufficient for your > purposes. You can therefore remove the extraneous code which is only > for illustration of all three approaches to the problem. > > Note that I commented your if-else constructs and used an Enum > variable instead. I think it's more "intuitive", this way ! > > > > winmail.dat > 6Kהצגהורדה-הסתר טקסט מצוטט- > > -הראה טקסט מצוטט-
