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Is using Random and OrderBy a good shuffle algorithm? [closed]
(13 answers)
Are GUIDs timely ordered ? If ORDER BY used with a GUID variable type, will records created lately come late?
(3 answers)
Closed 5 years ago.
Which one is faster?
Im doing tests on a ConcurrentDictionary and want to randomize it and just return 1 result. Essentially pick a random result from it.
Which method is faster/more efficient?
Efficiency as in, as little cpu/memory while having low possible errors like conflicts and such.
Method A.
Random rand = new Random();
var result = concDict.ElementAt(rand.Next(concDict.Count() - 1));
Method B.
var result = concDict.OrderBy(x=>Guid.NewGuid()).First();
In my "vague" testing I dont see much difference apart from Method B being more efficient. Method A can succum to the concDict's Count being out of sync with the concDict.ElementAt causing ArgumentOutOfRangeException: 'maxValue' must be greater than zero. while Method B literally cant cause that.
Related
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FindAll vs Where extension-method
(5 answers)
Slow LINQ query for .ToArray()
(3 answers)
C# FindAll VS Where Speed
(5 answers)
Closed 3 years ago.
I have an array of structs and I need to locate all the elements that share a certain condition.
Currently I use:
Array.FindAll(someArray, x => x.eg == "*Perfomance Test*")
But after some googling I noticed that there is a much faster way by using the LINQ Where-method.
someArray.Where(x => x.eg == "*Perfomance Test*")
I did some testing and the results are pretty impressive:
FindAll: 00:00:03.06
Where: 00:00:00.20
The problem is that Where returns IEnumerable. And I call this method that returns all these certain elements from the array within the for loop. Which is the type of loop I need to use. I used the .ToArray() method, but that made it much worse so that FindAll() is the faster approach.
Because of that it seems to me that if I need to get an array of elements, Where is much slower option than FindAll. But maybe I'm missing something.
Are there any better, faster options?
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C# - Asserting two objects are equal in unit tests
(8 answers)
Comparing Two objects using Assert.AreEqual()
(5 answers)
Closed 4 years ago.
I want to know, when an object is equal or not equal to another object with the method Assert.AreEqual.
I have to objects, which are tested false.
But when I test every single property with AreEqual the tests are successfull.
That would mean equality does not only depend on properties. Could someone explain that?
(It's a theoretical question, I cannot provide any data)
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Is using static bytecode analysis to determine all the possible paths through a given method a variant of trying to solve the Halting Problem?
(1 answer)
Closed 4 years ago.
Suppose there's a method which returns enum. But it returns only a subset of all the values of the enumeration. Can I find out programmatically which values are obtainable?
Example. I have an enum, which describes color with 100 values. Method GetCurrentTrafficLightsState can return only 3 colors of 100. I want to pass the method GetCurrentTrafficLightsState into some other method and get 3 colors as response.
No there isn't. You cannot even determine if it will return at all, see https://en.wikipedia.org/wiki/Halting_problem
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Algorithm to return all combinations of k elements from n
(77 answers)
What is the best way to find all combinations of items in an array?
(11 answers)
Closed 9 years ago.
Given:
{1,2,3}
Expected result:
{1,2,3},
{1,2},{1,3},{2,3},
{1},{2},{3}
So I want basically ALL possible combinations in a list ( but including all possible combinations of - when every element is removed ).
I hope you get what I mean ;)
Question: Which algorithm achieves this?
You want the power set algorithm.
There are some examples on Rosetta Code.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
What's the purpose of the Tuple(T1)/Singleton in .net?
Trying to mimic a Tuple as implemented in .Net 4 (For .Net 3) I just realized there is a Tuple(Of T)? This was quite a surprize!
Why would anyone do this
Tuple<string> result = new Tuple<string>("Data");
Instead of this
return "Data";
Isn't the whole point of a tuple that its a container for "loosely related data that isnt cohesive enough to make another class"? Am I missing something?
There are a finite number of tuple-arities in the library, so to define an 8-tuple, you use the kind with 7-elements whose 'rest' argument is a one-tuple. See
http://msdn.microsoft.com/en-us/library/dd383325.aspx
This is a carry over from set theory that might not have much use for a software developer.
Tuples are simply ordered lists of elements. An N-tuple has n elements, and n can be one, which is called a singleton. You probably won't have much use for a 1-tuple in code, but I'm guessing the C# team put it in there for completeness.
http://en.wikipedia.org/wiki/Tuple#Etymology