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  • Big datastructures in functional programming

    - by Denis Gorodetskiy
    I'm newbie in Functional Programming. I have a huge neural network with thousands of neurons and every connection between neurons has its weight. I have to update these weights very often, several thousand times per learning session. Is FP still applicable here? I mean in fp we can't modify variables and only able to return new variables not changing previous values. Does this mean I have to recreate whole network on every weight update?

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  • Writing a new programming language - when and how to bootstrap datastructures?

    - by OnResolve
    I'm in the process of writing my own programming language which, thus far, has been going great in terms of what I set out to accomplish. However, now, I'd like to bootstrap some pre-existing data structures and/or objects. My problem is that I'm not really sure on how to begin. When the compiler begins do I splice in these add-ins so their part of the scope of the application? If I make these in some core library, my concern is how I distribute the library in addition to the compiler--or are they part of the compiler? I get that there are probably a number of plausible ways to approach this, but I'm having trouble with the setting my direction. If it helps, the language is on top of the .NET core (i.e it compiles to CLR code). Any help or suggestions are very much appreciated!

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  • Write a function that compares two strings and returns a third string containing only the letters th

    - by Pritam
    Hi All, I got this homework. And have solved it in following way. I need your comments whether it is a good approach or I need to use any other data sturcture to solve it in better way. public string ReturnCommon(string firstString, string scndString) { StringBuilder newStb = new StringBuilder(); if (firstString != null && scndString != null) { foreach (char ichar in firstString) { if (!newStb.ToString().Contains(ichar) && scndString.Contains(ichar)) newStb.Append(ichar); } } return newStb.ToString(); }

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  • Thread-safe data structures

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of exists call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? Thank you.

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  • Algorithm for autocomplete?

    - by StackUnderflow
    I am referring to the algorithm that is used to give query suggestions when a user type a search term in google. I am mainly interested in how google algorithm is able to show: 1. Most important results (most likely queries rather than anything that matches) 2. Match substrings 3. Fuzzy matches I know you could use Trie or generalized trie to find matches but it wouldn't meet the above requirements... Similar questions asked earlier here Thanks

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  • delta-dictionary/dictionary with revision awareness in python?

    - by shabbychef
    I am looking to create a dictionary with 'roll-back' capabilities in python. The dictionary would start with a revision number of 0, and the revision would be bumped up only by explicit method call. I do not need to delete keys, only add and update key,value pairs, and then roll back. I will never need to 'roll forward', that is, when rolling the dictionary back, all the newer revisions can be discarded, and I can start re-reving up again. thus I want behaviour like: >>> rr = rev_dictionary() >>> rr.rev 0 >>> rr["a"] = 17 >>> rr[('b',23)] = 'foo' >>> rr["a"] 17 >>> rr.rev 0 >>> rr.roll_rev() >>> rr.rev 1 >>> rr["a"] 17 >>> rr["a"] = 0 >>> rr["a"] 0 >>> rr[('b',23)] 'foo' >>> rr.roll_to(0) >>> rr.rev 0 >>> rr["a"] 17 >>> rr.roll_to(1) Exception ... Just to be clear, the state associated with a revision is the state of the dictionary just prior to the roll_rev() method call. thus if I can alter the value associated with a key several times 'within' a revision, and only have the last one remembered. I would like a fairly memory-efficient implementation of this: the memory usage should be proportional to the deltas. Thus simply having a list of copies of the dictionary will not scale for my problem. One should assume the keys are in the tens of thousands, and the revisions are in the hundreds of thousands. We can assume the values are immutable, but need not be numeric. For the case where the values are e.g. integers, there is a fairly straightforward implementation (have a list of dictionaries of the numerical delta from revision to revision). I am not sure how to turn this into the general form. Maybe bootstrap the integer version and add on an array of values? all help appreciated.

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  • about Randomized-select algorithm

    - by matin1234
    Hi I have this array A = <3,2,9,0,7,5,4,8,6,1> and I want to write all its worst partitions are these correct?thanks a1 = <0,2,9,3,7,5,4,8,6,1> a2 = <1,9,3,7,5,4,8,6,2> a3 = <2,3,7,5,4,8,6,9> a4 = <3,7,5,4,8,6,9> a5 = <4,5,7,8,6,9> a6 = <5,7,8,6,9> a7 = <6,8,7,9> a8 = <7,8,9> a9 = <8,9> a10 = <9>

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  • adjacency list creation , out of Memory error

    - by p1
    Hello , I am trying to create an adjacency list to store a graph.The implementation works fine while storing 100,000 records. However,when I tried to store around 1million records I ran into OutofMemory Error : Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOfRange(Arrays.java:3209) at java.lang.String.(String.java:215) at java.io.BufferedReader.readLine(BufferedReader.java:331) at java.io.BufferedReader.readLine(BufferedReader.java:362) at liarliar.main(liarliar.java:39) Following is my implementation HashMap<String,ArrayList<String>> adj = new HashMap<String,ArrayList<String>>(num); while ((str = in.readLine()) != null) { StringTokenizer Tok = new StringTokenizer(str); name = (String) Tok.nextElement(); cnt = Integer.valueOf(Tok.nextToken()); ArrayList<String> templist = new ArrayList<String>(cnt); while(cnt>0) { templist.add(in.readLine()); cnt--; } adj.put(name,templist); } //done creating a adjacency list I am wondering, if there is any better way to implement the adjacency list. Also, I know number of nodes right in the begining and , in the future I flatten the list as I visit nodes. Any suggestions ? Thanks

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  • Suggest a good method with least lookup time complexity

    - by Amrish
    I have a structure which has 3 identifier fields and one value field. I have a list of these objects. To give an analogy, the identifier fields are like the primary keys to the object. These 3 fields uniquely identify an object. Class { int a1; int a2; int a3; int value; }; I would be having a list of say 1000 object of this datatype. I need to check for specific values of these identity key values by passing values of a1, a2 and a3 to a lookup function which would check if any object with those specific values of a1, a2 and a3 is present and returns that value. What is the most effective way to implement this to achieve a best lookup time? One solution I could think of is to have a 3 dimensional matrix of length say 1000 and populate the value in it. This has a lookup time of O(1). But the disadvantages are. 1. I need to know the length of array. 2. For higher identity fields (say 20), then I will need a 20 dimension matrix which would be an overkill on the memory. For my actual implementation, I have 23 identity fields. Can you suggest a good way to store this data which would give me the best look up time?

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  • Java Generics Type Safety warning with recursive Hashmap

    - by GC
    Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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  • Create a mirrored linked list in Java

    - by glacier89
    Linked-List: Mirror Consider the following private class for a node of a singly-linked list of integers: private class Node{ public int value; public Node next; } A wrapper-class, called, ListImpl, contains a pointer, called start to the first node of a linked list of Node. Write an instance-method for ListImpl with the signature: public void mirror(); That makes a reversed copy of the linked-list pointed to by start and appends that copy to the end of the list. So, for example the list: start 1 2 3 after a call to mirror, becomes: start 1 2 3 3 2 1 Note: in your answer you do not need to dene the rest of the class for ListImpl just the mirror method.

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  • To have an Integer pointing to 3 ordered lists in Java

    - by Masi
    Which datastructure would you use in the place of X to have efficient merges, sorts and additions as described below? #1 Possible solution: one HashMap to X -datastructure Having a HashMap pointing from fileID to some datastructure linking word, wordCount and wordID may be a good solution. However, I have not found a way to implement it. I am not allowed to use Postgres or any similar tool to keep my data neutralized. I want to have efficient merges, sorts and additions according to fileID, wordID or wordCount for the type below. I have the type Words which has th field fileID that points to a list of words and to relating pieces of information: The Type class Words =================================== fileID: int [list of words] : ArrayList [list of wordCounts] : ArrayList [list of wordIDs] : ArrayList Example of the data in fileID word wordCount wordID instance1 of words 1 He 123 1111 1 llo 321 2 instance2 of words 2 Van 213 666 2 cou 777 932 Example of needed merge fileID wordID fileID wordID 1 2 1 3 wordID=2 2 2 ========> 1 2 2 3 2 2 I cannot see any usage of set-operations such as intersections here because order is needed. Having about three HashMaps makes sorting difficult: from word to wordID in a given fileID from wordID to fileID from wordID to wordCount in a given fileID

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  • Matching unmatched strings based on a unknown pattern

    - by Polity
    Alright guys, i really hurt my brain over this one and i'm curious if you guys can give me any pointers towards the right direction i should be taking. The situation is this: Lets say, i have a collection of strings (let it be clear that the pattern of this strings is unknown. For a fact, i can say that the string contain only signs from the ASCII table and therefore, i dont have to worry about weird Chinese signs). For this example, i take the following collection of strings (note that the strings dont have to make any human sence so dont try figguring them out :)): "[001].[FOO].[TEST] - 'foofoo.test'", "[002].[FOO].[TEST] - 'foofoo.test'", "[003].[FOO].[TEST] - 'foofoo.test'", "[001].[FOO].[TEST] - 'foofoo.test.sample'", "[002].[FOO].[TEST] - 'foofoo.test.sample'", "-001- BAR.[TEST] - 'bartest.xx1", "-002- BAR.[TEST] - 'bartest.xx1" Now, what i need to have is a way of finding logical groups (and subgroups) of these set of strings, so in the above example, just by rational thinking, you can combine the first 3, the 2 after that and the last 2. Also the resulting groups from the first 5 can be combined in one main group with 2 subgroups, this should give you something like this: { { "[001].[FOO].[TEST] - 'foofoo.test'", "[002].[FOO].[TEST] - 'foofoo.test'", "[003].[FOO].[TEST] - 'foofoo.test'", } { "[001].[FOO].[TEST] - 'foofoo.test.sample'", "[002].[FOO].[TEST] - 'foofoo.test.sample'", } { "-001- BAR.[TEST] - 'bartest.xx1", "-002- BAR.[TEST] - 'bartest.xx1" } } Sorry for the layout above but indenting with 4 spaces doesnt seem to work correctly (or im frakk'n it up). Anyways, I'm not sure how to approach this problem (how to get the result desired as indicated above). First of, i thought of creating a huge set of regexes which would parse most known patterns but the amount of different patterns is just to huge that this isn't realistic. Another think i thought of was parsing each indidual word within a string (so strip all non alphabetic or numeric characters and split by those), and if X% matches, i can assume the strings belong to the same group. (where X wil probably be around 80/90). However, i find the area of speculation kinda big. For example, when matching strings with each 20 words, the change of hitting above 80% is kinda big (that means that 4 words can differ), however when matching only 8 words, 2 words at most can differ. My question to you is, what would be a logical approach in the above situation? Thanks in advance!

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  • Java or php tree structure problem

    - by agazerboy
    Hi All, I have all my data in my database. It has following 4 columns id source_clust target_clust result_clust 1 7 72 649 2 9 572 650 3 649 454 651 4 32 650 435 This data is like tree structure. source_clust and target_clust generate target_clust. target_clust can be source_clust or target_clust to make a new target_clust. Is there any php function or class that I can use to generate tree structure for my data???? I see this MySql site they are doing exactly what I need but I couldn't find how to implement that query in my data. Thanks ! Edited Is there any way in java to do it? if we have same data in array ??

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  • What is the best way to handle validity dates in applications ?

    - by user214626
    Hello, How do we model these objects ? Scenario 1: Price changes in a time period EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-02-01 Null 900$ So, if the price changes to 910$ on 2009-02-15, then the system should automatically update the expiry date on the previous effective price to 2009-02-14, to keep it consistent. Scenario 2: No price specified between 2009-02-01 to 2009-02-28 EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-03-01 Null 900$ So, if new price is specified for 2009-02-15 onwards , then the system should automatically set the expiry date on the record to be inserted to 2009-02-28, because already a record effective from 2009-03-01 exists. Please suggest an effective way to handle these scenarios to model my framework, or are there any frameworks around that can do this . Thanks

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  • storing/retrieving data for graph with long continuous stretches

    - by james
    i have a large 2-dimensional data set which i would like to graph. the graph is displayed in a browser and the data is retrieved via ajax. long stretches of this graph will be continuous - e.g., for x=0 through x=1000, y=9, then for x=1001 through x=1100, y=80, etc. the approach i'm considering is to send (from the server) and store (in the browser) only the points where the data changes. so for the example above, i would say data[0] = 9, then data[1001] = 80. then given x=999 for example, retrieving data[999] would actually look up data[0]. the problem that arises is finding a dictionary-like data structure which behaves like this. the approach i'm considering is to store the data in a traditional dictionary object, then also maintain a sorted array of key for that object. when given x=999, it would look at the mid-point of this array, determine whether the nearest lower key is left or right of that midpoint, then repeat with the correct subsection, etc.. does anyone have thoughts on this problem/approach?

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  • about Select algorithm

    - by matin1234
    Hi I have read about the select algorithm and I have a question maybe it looks silly!!! but why we consider the array as groups of 5 elements ?? can we consider it with 7 or 3 elements??thanks

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  • Data structure in c for fast look-up/insertion/removal of integers (from a known finite domain)

    - by MrDatabase
    I'm writing a mobile phone based game in c. I'm interested in a data structure that supports fast (amortized O(1) if possible) insertion, look-up, and removal. The data structure will store integers from the domain [0, n] where n is known ahead of time (it's a constant) and n is relatively small (on the order of 100000). So far I've considered an array of integers where the "ith" bit is set iff the "ith" integer is contained in the set (so a[0] is integers 0 through 31, a[1] is integers 32 through 63 etc). Is there an easier way to do this in c?

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