I ran across the question below in an old exam. My answers just feels a bit short and inadequate. Any extra ideas I can look into or reasons I have overlooked would be great. Thanx Consider the MAD method compression function, mapping an object with hash code i to element [(3i + 7)mod9027]mod6000 of the 6000-element bucket array. Explai...
Looking for good source code either in C or C++ or Python to understand how a hash function is implemented and also how a hash table is implemented using it. Very good material on how hash fn and hash table implementation works. Thanks in advance. ...
I woudl like to know how to use a System.Collections.Hashtable in F#. The reason it is a Hashtable is because I am referencing C# assemblies. How would I call the following methods? - Add - Get value from key I have not been able to find anything useful in google about this. Any help would be appreciated. Thanks ...
Not a real question because I already found out the answer, but still interesting thing. I always thought that hash table is the fastest associative container if you hash properly. However, the following code is terribly slow. It executes only about 1 million iterations and takes more than 2 minutes of time on a Core 2 CPU. The code ...
I read that hash tables in Haskell had performance issues (on the Haskell-Cafe in 2006 and Flying Frog Consultancy's blog in 2009), and since I like Haskell it worried me. That was a year ago, what is the status now (June 2010)? Has the "hash table problem" been fixed in GHC? ...
Possible Duplicate: How to sort a Map<Key, Value> on the values in Java? I have a HashMap of the type: HashMap<String, Integer> h = new HashMap<String, Integer>(); The HashMap contains a list of Strings and the Integer is a counter for the number of times that String has been found. What I would like to be able to do is sor...
I have a Hashtable that maps strings to ints. Strings are unique, but several may be mapped to the same integer. My naive approach was to simply invert the Hashtable to a SortedList that is indexed by the Hashtable's values, but the problem is that you get a clash as soon as two of the Hashtable's strings map to the same value. What is...
I am currently developing a programming language in C, and I want to allow users to create apparently "unlimited" arrays with numerical indices without sacrificing performance in the process. For example, table [1000000000] would ideally be creatable and accessible in an instant without the memory overhead of a table of 1,000,000,000 ite...
I have a thread datatype in the interpreter implementation for a programming language I am working on. For various reasons, it’s a fairly common operation, to need to get the current thread (which is, itself, a pointer: a struct thread*). However, pthread_self(3) hands me a pthread_t, which is an opaque type; on some systems, it seems t...
Hi all, I have an infinite streams of numbers coming and I have to detect the first duplicate element. I think of using hash table for the above problem i.e whenever a number arrives, check whether it is already there in the hash table or not. In case it has, stop otherwise add that number to hash table. Now my question is does hash tab...
Recently I have read about hash-tables in a very famous book "Introduction to Algorithms". I haven't used them in any real applications yet, but wanted to. But don't know how to start. Can anyone give me some samples of using it, for example, how to realize dictionary application (like ABBYY Lingvo) using hash-tables? And finally wanted...
Hi, Although I understand very well what HashCode is and what a Hash Table does, I have to admit I don´t know how to use it (Beyond a common dictionary). I wanted to implement my own Hash Table so first I want to know the very basic about Hash: I know I can get the hash code with getHashCode()/hashCode() in Java and Scala. How is this...
Hi, I am looking for a family of hash function F1,..Fn, where each Fi maps any key in [0,1]. My first implementation was Fi(k) = F(k,i) = hash(i,hash(k,0)),. Here hash is the hashlittle function provided here (http://burtleburtle.net/bob/c/lookup3.c). I haven't looked under the hood of what exactly hashlittle does. As sharp readers wou...
Usually (as in C++), the hash function returns any size_t value -- thus many different hash values are possible (2^32). That is why I always thought that when people talked about them being implemented as tables, that is not really true in practice because the table would be much too big (2^32 entries). Of course my assumption was wrong...
I need to convert a F# map class to a System.Collections.Hashtable for use by C#. This question is not the same as the following: http://stackoverflow.com/questions/3032298/how-do-you-use-get-values-from-keys-add-items-hashtables-in-f That question asked how to return values from a hashtable. I want to build an F# map and then convert ...
I have 3 columns in a DataTable Id Name Count 1 James 4345 2 Kristen 89231 3 James 599 4 Suneel 317113 I need rows 1 and 3 gone, and the new datatable returning only rows 2 and 4. I found a really good related question in the suggestions on SO--this guy. But his solution uses hashtables, and on...
So, I am looking at different hash functions to use for hashing a 4 tuple ip and port to identify flows. One I came across was ((size_t)(key.src.s_addr) * 59) ^ ((size_t)(key.dst.s_addr)) ^ ((size_t)(key.sport) << 16) ^ ((size_t)(key.dport)) ^ ((size_t)(key.proto)); Now for the world of me, I cannot expla...
I'm developing tool, which takes Java code and generate code for getting estimations for execution time of basic blocks, loops and methods. After some block is executed, we put it's time to our tool. The program model is stored in next representation static Hashtable<String, Hashtable<Integer, Hashtable<String, pair>>> method2Data = ne...
I am curious to know what is the reasoning that could overweighs towards using a self-balancing tree technique to store items than using a hash table. I see that hash tables cannot maintain the insertion-order, but I could always use a linked list on top to store the insertion-order sequence. I see that for small number of values, th...
I have a hashtable in VB.NET and I need to get the string value of a key from it's value. For example, if I do: hashtable.add("string1","string2") How would I get the value "string1" if I had "string2"? ...