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  • algorithm to find longest non-overlapping sequences

    - by msalvadores
    I am trying to find the best way to solve the following problem. By best way I mean less complex. As an input a list of tuples (start,length) such: [(0,5),(0,1),(1,9),(5,5),(5,7),(10,1)] Each element represets a sequence by its start and length, for example (5,7) is equivalent to the sequence (5,6,7,8,9,10,11) - a list of 7 elements starting with 5. One can assume that the tuples are sorted by the start element. The output should return a non-overlapping combination of tuples that represent the longest continuos sequences(s). This means that, a solution is a subset of ranges with no overlaps and no gaps and is the longest possible - there could be more than one though. For example for the given input the solution is: [(0,5),(5,7)] equivalent to (0,1,2,3,4,5,6,7,8,9,10,11) is it backtracking the best approach to solve this problem ? I'm interested in any different approaches that people could suggest. Also if anyone knows a formal reference of this problem or another one that is similar I'd like to get references. BTW - this is not homework. Edit Just to avoid some mistakes this is another example of expected behaviour for an input like [(0,1),(1,7),(3,20),(8,5)] the right answer is [(3,20)] equivalent to (3,4,5,..,22) with length 20. Some of the answers received would give [(0,1),(1,7),(8,5)] equivalent to (0,1,2,...,11,12) as right answer. But this last answer is not correct because is shorter than [(3,20)].

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  • Why does this static field always get initialized over-eagerly?

    - by TheSilverBullet
    I am looking at this excellent article from Jon Skeet. While executing the demo code, Jon Skeet says that we can expect three different kinds of behaviours. To quote that article: The runtime could decide to run the type initializer on loading the assembly to start with... Or perhaps it will run it when the static method is first run... Or even wait until the field is first accessed... When I try this out (on framework 4), I always get the first result. That is, the static method is initialized before the assembly is loaded. I have tried running this multiple times and get the same result. (I tried both the debug and release versions) Why is this so? Am I missing something?

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  • C#4: Why does this static field always get initialized over-eagerly?

    - by TheSilverBullet
    I am looking at this excellent article from Jon Skeet at this location: http://csharpindepth.com/Articles/General/Beforefieldinit.aspx While executing the demo code, Jon Skeet says that we can expect three different kinds of behaviours. To quote that article: The runtime could decide to run the type initializer on loading the assembly to start with... Or perhaps it will run it when the static method is first run... Or even wait until the field is first accessed... When I try this out (on framework 4), I always get the first result. That is, the static method is initialized before the assembly is loaded. I have tried running this multiple times and get the same result. (I tried both the debug and release versions) Why is this so? Am I missing something?

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  • EJB3 Entity and Lazy Problem

    - by Stefano
    My Entity beAN have 2 list: @Entity @Table(name = "TABLE_INTERNAL") public class Internal implements java.io.Serializable { ...SOME GETTERS AND SETTERS... private List<Match> matchs; private List<Regional> regionals; } mapped one FetchType.LAZY and one FetchType.EAGER : @OneToMany(fetch = FetchType.LAZY,mappedBy = "internal") public List<Match> getMatchs() { return matchs; } public void setMatchs(List<Match> matchs) { this.matchs = matchs; } @ManyToMany(targetEntity = Regional.class, mappedBy = "internals", fetch =FetchType.EAGER) public List<Regional> getRegionals() { return regionals; } public void setRegionals(List<Regional> regionals) { this.regionals = regionals; } I need both lists full ! But I cant put two FetchType.EAGER beacuse it's an error. I try some test: List<Internal> out; out= em.createQuery("from Internal").getResultList(); out= em.createQuery("from Internal i JOIN FETCH i.regionals ").getResultList(); I'm not able to fill both lists...Help!!! Stefano

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  • Lazy non-modifiable list in Google Collections

    - by mindas
    I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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  • Help me understand entity framework 4 caching for lazy loading

    - by Chris
    I am getting some unexpected behaviour with entity framework 4.0 and I am hoping someone can help me understand this. I am using the northwind database for the purposes of this question. I am also using the default code generator (not poco or self tracking). I am expecting that anytime I query the context for the framework to only make a round trip if I have not already fetched those objects. I do get this behaviour if I turn off lazy loading. Currently in my application I am breifly turning on lazy loading and then turning it back off so I can get the desired behaviour. That pretty much sucks, so please help. Here is a good code example that can demonstrate my problem. Public Sub ManyRoundTrips() context.ContextOptions.LazyLoadingEnabled = True Dim employees As List(Of Employee) = context.Employees.Execute(System.Data.Objects.MergeOption.AppendOnly).ToList() 'makes unnessesary round trip to the database, I just loaded the employees' MessageBox.Show(context.Employees.Where(Function(x) x.EmployeeID < 10).ToList().Count) context.Orders.Execute(System.Data.Objects.MergeOption.AppendOnly) For Each emp As Employee In employees 'makes unnessesary trip to database every time despite orders being pre loaded.' Dim i As Integer = emp.Orders.Count Next End Sub Public Sub OneRoundTrip() context.ContextOptions.LazyLoadingEnabled = True Dim employees As List(Of Employee) = context.Employees.Include("Orders").Execute(System.Data.Objects.MergeOption.AppendOnly).ToList() MessageBox.Show(employees.Where(Function(x) x.EmployeeID < 10).ToList().Count) For Each emp As Employee In employees Dim i As Integer = emp.Orders.Count Next End Sub Why is the first block of code making unnessesary round trips?

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  • Lazy non-modifiable list

    - by mindas
    I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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  • Model class for NSDictionary information with Lazy Loading

    - by samfu_1
    My application utilizes approx. 50+ .plists that are used as NSDictionaries. Several of my view controllers need access to the properties of the dictionaries, so instead of writing duplicate code to retrieve the .plist, convert the values to a dictionary, etc, each time I need the info, I thought a model class to hold the data and supply information would be appropriate. The application isn't very large, but it does handle a good deal of data. I'm not as skilled in writing model classes that conform to the MVC paradigm, and I'm looking for some strategies for this implementation that also supports lazy loading.. This model class should serve to supply data to any view controller that needs it and perform operations on the data (such as adding entries to dictionaries) when requested by the controller functions currently planned: returning the count on any dictionary adding one or more dictionaries together Currently, I have this method for supporting the count lookup for any dictionary. Would this be an example of lazy loading? -(NSInteger)countForDictionary: (NSString *)nameOfDictionary { NSBundle *bundle = [NSBundle mainBundle]; NSString *plistPath = [bundle pathForResource: nameOfDictionary ofType: @"plist"]; //load plist into dictionary NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile: plistPath]; NSInteger count = [dictionary count] [dictionary release]; [return count] }

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  • breadth-first traversal of directory tree is not lazy

    - by user855443
    I try to traverse the diretory tree. A naive depth-first traversal seems not to produce the data in a lazy fashion and runs out of memory. I next tried a breadth first approach, which shows the same problem - it uses all the memory available and then crashes. the code i have is: getFilePathBreadtFirst :: FilePath -> IO [FilePath] getFilePathBreadtFirst fp = do fileinfo <- getInfo fp res :: [FilePath] <- if isReadableDirectory fileinfo then do children <- getChildren fp lower <- mapM getFilePathBreadtFirst children return (children ++ concat lower) return (children ++ concat () else return [fp] -- should only return the files? return res getChildren :: FilePath -> IO [FilePath] getChildren path = do names <- getUsefulContents path let namesfull = map (path </>) names return namesfull testBF fn = do -- crashes for /home/frank, does not go to swap fps <- getFilePathBreadtFirst fn putStrLn $ unlines fps I think all the code is either linear or tail recursive, and I would expect that the listing of filenames starts immediately, but in fact it does not. Where is the error in my code and my thinking? where have I lost lazy evaluation?

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  • Stop lazy-loading images?

    - by Greg
    Here's the issue – I followed along with the Apple lazy-load image sample code to handle my graphical tables. It works great. However, my lazy-load image tables are being stacked within a navigation controller so that you can move in and out of menus. While all this works, I'm getting a persistent crash when I move into a table then move immediately back out of it using the "back" button. This appears to be a result of the network connections loading content not being closed properly, or calling back to their released delegates. Now, I've tried working through this and carefully setting all delegates to nil and calling close on all open network connections before releasing a menu. However, I'm still getting the error. Also – short posting my entire application code into this post, I can't really post a specific code snippet that illustrates this situation. I wonder if anyone has ideas for tasks that I may be missing? Do I need to do anything to close a network connection other than closing it and setting it to nil? Also, I'm new to debugging tools – can anyone suggest a good tool to use to watch network connections and see what's causing them to fail? Thanks!

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  • CentOS security for lazy admins

    - by Robby75
    I'm running CentOS 5.5 (basic LAMP with Parallels Power Panel and Plesk) and have thus far neglected security (because it's not my full-time job, there is always something more important on my todo-list). My server does not contain any secret data and also no lives depend on it - Basically what I want is to make sure it does not become part of a botnet, that is "good enough" security in my case. Anyway, I don't want to become a full-time paranoid admin (like constantly watching and patching everything because of some obscure problem), I also don't care about most security problems like DOS attacks or problems that only exist when using some arcane settings. I'm in search of a "happy medium", for example a list of known important problems in the default installation of CentOS 5.5 and/or a list of security problems that have actually been exploited - not the typical endless list of buffer overflows that "maybe" a problem in some special case. The problem that I have with the usually recommended approaches (joining mailing lists, etc.) is that the really important problems (something where an exploit exists, that is exploitable in a common setup and where the attacker can do something really useful - i.e. not a DOS) are completely and utterly swamped by millions of tiny security alerts that surely are important for high-security servers, but not for me. Thanks for all suggestions!

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  • Rsync and Lazy mode ?

    - by fabien-barbier
    Since transferring or copying a file that is being used sometimes causes corruption of the transferred file, can we define a time interval in which Rsync checks each file in a given directory to see if there is a change within that time interval ? Files that are not changed during that interval will be transferred, while those that have changes will not. Can I do that with rsync ? Or another tool ? Is there a script to add this functionality to Rsync ? Thanks

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  • Lazy linux backup system?

    - by Alex
    Ok, so I want to say Time Machine, but that's note exactly what I'm looking for. I want to set up a system that will regularly (hourly?) back up the /home directory of our machine. time Machine style things are naturally preferable since they save space by only saving the changes, but honestly, this is important enough that I can suffer some waste. Any ideas?

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  • Lazy property loading in Nhibernate and Spring

    - by Khash
    I'm using NHibernate 2.1.2 and Spring 1.3 I have two Text columns (blobs) in one of my classes. I'm trying to use lazy="true" for the mapping of those properties but NHProfiler still shows the two columns being added to the SELECT statement when the main object is loaded. I'm using Spring.NHibernate session factory and have configured ProxyFactory with both Castle and Spring with no luck.

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  • hibernate - lazy init joined component

    - by robinmag
    I used the mapping solution from this question to have a joined component. But it make hibernate trigger join query to obtain the component event i use fetch="select" in <join> Please tell me how can i make the joined component lazy init. Thank you

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  • Why toInteger :: Int -> Integer is lazy?

    - by joppux
    I have the following code: {-# NOINLINE i2i #-} i2i :: Int -> Integer i2i x = toInteger x main = print $ i2i 2 Running GHC with -ddump-simpl flag gives: [Arity 1 NoCafRefs Str: DmdType U(L)] Main.i2i = GHC.Real.toInteger1 Seems that conversion from Int to Integer is lazy. Why is it so - is there a case when I can have (toInteger _|_ ::Int) /= _|_ ?

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  • Python lazy property decorator

    - by detly
    Recently I've gone through an existing code base and refactored a lot of instance attributes to be lazy, ie. not be initialised in the constructor but only upon first read. These attributes do not change over the lifetime of the instance, but they're a real bottleneck to calculate that first time and only really accessed for special cases. I find myself typing the following snippet of code over and over again for various attributes across various classes: class testA(object): def __init__(self): self._a = None self._b = None @property def a(self): if self._a is None: # Calculate the attribute now self._a = 7 return self._a @property def b(self): #etc Is there an existing decorator to do this already in Python that I'm simply unaware of? Or, is there a reasonably simple way to define a decorator that does this? I'm working under Python 2.5, but 2.6 answers might still be interesting if they are significantly different.

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  • Lazy loading of ESB in a jruby rails app

    - by brad
    I have a jruby/rails app using: jruby 1.4.0 Rails 2.3.5 ActiveMQ 5.3.0 Mule ESB 2.2.1 Currently in our environment.rb file we start up Mule in the initializer. This becomes a big pain when we go to do normal rake tasks that don't require JMS/Mule such as db:migrate as it takes a long time to startup/shutdown Mule everytime. The code is similar to this: APP_CONTEXT = Java::our.company.package.service_clients.Initializer.getAppContext(MULE_CONFIG_PATH) And we use APP_CONTEXT to fetch the bean to connect to the appropriate service. I'm trying to figure out some mechanism by which APP_CONTEXT could be lazily instantiated (not in initialize) to avoid all of the pains of having to startup Mule on initialize. Currently we have a few ruby client classes that are instantiated as a before_filter in application_controller such as @data_service = DataService.new(APP_CONTEXT) that initialize the proper java client for each request for use in our controllers. I'm open to all suggestions. I'm having a hard time trying to find the right place to put this lazy instantiation.

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  • NHibernate Lazy="Extra"

    - by Adam Rackis
    Is there a good explanation out there on what exactly lazy="extra" is capable of? All the posts I've seen all just repeat the fact that it turns references to MyObject.ItsCollection.Count into select count(*) queries (assuming they're not loaded already). I'd like to know if it's capable of more robust things, like turning MyObject.ItsCollection.Any(o => o.Whatever == 5) into a SELECT ...EXISTS query. Section 18.1 of the docs only touches on it. I'm not an NH developer, so I can't really experiment with it and watch SQL Profiler without doing a bit of work getting everything set up; I'm just looking for some sort of reference describing what this feature is capable of. Thank you!

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  • Can django lazy-load fields in a model?

    - by Leopd
    One of my django models has a large TextField which I often don't need to use. Is there a way to tell django to "lazy-load" this field? i.e. not to bother pulling it from the database unless I explicitly ask for it. I'm wasting a lot of memory and bandwidth pulling this TextField into python every time I refer to these objects. The alternative would be to create a new table for the contents of this field, but I'd rather avoid that complexity if I can.

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  • Algorithm for disordered sequences of strings

    - by Kinopiko
    The Levenshtein distance gives us a way to calculate the distance between two similar strings in terms of disordered individual characters: quick brown fox quikc brown fax The Levenshtein distance = 3. What is a similar algorithm for the distance between two strings with similar subsequences? For example, in quickbrownfox brownquickfox the Levenshtein distance is 10, but this takes no account of the fact that the strings have two similar subsequences, which makes them more "similar" than completely disordered words like quickbrownfox qburiocwknfox and yet the completely disordered version has a Levenshtein distance of eight. What distance measures exist which take the length of subsequences into account, without assuming that the subsequences can be easily broken into distinct words?

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