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  • "Most popular" GROUP BY in LINQ?

    - by tags2k
    Assuming a table of tags like the stackoverflow question tags: TagID (bigint), QuestionID (bigint), Tag (varchar) What is the most efficient way to get the 25 most used tags using LINQ? In SQL, a simple GROUP BY will do: SELECT Tag, COUNT(Tag) FROM Tags GROUP BY Tag I've written some LINQ that works: var groups = from t in DataContext.Tags group t by t.Tag into g select new { Tag = g.Key, Frequency = g.Count() }; return groups.OrderByDescending(g => g.Frequency).Take(25); Like, really? Isn't this mega-verbose? The sad thing is that I'm doing this to save a massive number of queries, as my Tag objects already contain a Frequency property that would otherwise need to check back with the database for every Tag if I actually used the property. So I then parse these anonymous types back into Tag objects: groups.OrderByDescending(g => g.Frequency).Take(25).ToList().ForEach(t => tags.Add(new Tag() { Tag = t.Tag, Frequency = t.Frequency })); I'm a LINQ newbie, and this doesn't seem right. Please show me how it's really done.

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  • MVVM and avoiding Monolithic God object

    - by bufferz
    I am in the completion stage of a large project that has several large components: image acquisition, image processing, data storage, factory I/O (automation project) and several others. Each of these components is reasonably independent, but for the project to run as a whole I need at least one instance of each component. Each component also has a ViewModel and View (WPF) for monitoring status and changing things. My question is the safest, most efficient, and most maintainable method of instantiating all of these objects, subscribing one class to an Event in another, and having a common ViewModel and View for all of this. Would it best if I have a class called God that has a private instance of all of these objects? I've done this in the past and regretted it. Or would it be better if God relied on Singleton instances of these objects to get the ball rolling. Alternatively, should Program.cs (or wherever Main(...) is) instantiate all of these components, and pass them to God as parameters and then let Him (snicker) and His ViewModel deal with the particulars of running this projects. Any other suggestions I would love to hear. Thank you!

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  • Any suggestions to improve my PDO connection class?

    - by Scarface
    Hey guys I am pretty new to pdo so I basically just put together a simple connection class using information out of the introductory book I was reading but is this connection efficient? If anyone has any informative suggestions, I would really appreciate it. class PDOConnectionFactory{ public $con = null; // swich database? public $dbType = "mysql"; // connection parameters public $host = "localhost"; public $user = "user"; public $senha = "password"; public $db = "database"; public $persistent = false; // new PDOConnectionFactory( true ) <--- persistent connection // new PDOConnectionFactory() <--- no persistent connection public function PDOConnectionFactory( $persistent=false ){ // it verifies the persistence of the connection if( $persistent != false){ $this->persistent = true; } } public function getConnection(){ try{ $this->con = new PDO($this->dbType.":host=".$this->host.";dbname=".$this->db, $this->user, $this->senha, array( PDO::ATTR_PERSISTENT => $this->persistent ) ); // carried through successfully, it returns connected return $this->con; // in case that an error occurs, it returns the error; }catch ( PDOException $ex ){ echo "We are currently experiencing technical difficulties. We have a bunch of monkies working really hard to fix the problem. Check back soon: ".$ex->getMessage(); } } // close connection public function Close(){ if( $this->con != null ) $this->con = null; } }

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  • C# Type conversion between two similar Datatable objects

    - by Ali
    I have .NET project with sync framework and two separate Datasets for MS SQL and Compact SQL. in my base class I have a generic DataTable object. in my derived classed I assign Typed DataTable to the generic object based on whether the application is operating online or offline: example: if (online) _dataTable = new MSSQLDataSet.Customer; else _dataTable = new CompactSQLDataSet.Customer; Now every where in my code i have to check and do a cast based on the current network mode like this: public void changeCustomerID(int ID) { if (online) (MSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; else (CompactMSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; } but I don't think this is very efficient and I believe it can be done in a smarter way to only use one line of code by dynamically getting the Type of _dataTable on the run time. my problem is at the design time, in order to acess datatable porperties such as "CustomerID" it has to be casted to either MSSQLDataSet.CustomerDataTable or CompactMSSQLDataSet.CustomerDataTable. Is there a way to have a function or a operator to convert the _datatable to its runtime type but still be able to use it's design time properties which are the same between the two types? something like: ((aType)_dataTable)[i].CustomerID = value; //or GetRuntimeType(_dataTable)[i].CustomerID = value;

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  • Need Help finding an appropriate task assignment algorithm for a college project involving coordinat

    - by Trif Mircea
    I am a long time lurker here and have found over time many answers regarding jquery and web development topics so I decided to ask a question of my own. This time I have to create a c++ project for college which should help manage the workflow of a company providing all kinds of services through in the field teams. The ideas I have so far are: client-server application; the server is a dispatcher where all the orders from clients get and the clients are mobile devices (PDAs) each team in the field having one a order from a client is a task. Each task is made up of a series of subtasks. You have a database with estimations on how long a task should take to complete you also know what tasks or subtasks each team on the field can perform based on what kind of specialists made up the team (not going to complicate the problem by adding needed materials, it is considered that if a member of a team can perform a subtask he has the stuff needed) Now knowing these factors, what would a good task assignment algorithm be? The criteria is: how many tasks can a team do, how many tasks they have in the queue, it could also be location, how far away are they from the place but I don't think I can implement that.. It needs to be efficient and also to adapt quickly is the human dispatcher manually assigns a task. Any help or leads would be really appreciated. Also I'm not 100% sure in the idea so if you have another way you would go about creating such an application please share, even if it just a quick outline. I have to write a theoretical part too so even if the ideas are far more complex that what i outlined that would be ok ; I'd write those and implement what I can. Edit: C++ is the only language I know unfortunately.

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  • Set a datetime for next or previous sunday at specific time

    - by Marc
    I have an app where there is always a current contest (defined by start_date and end_date datetime). I have the following code in the application_controller.rb as a before_filter. def load_contest @contest_last = Contest.last @contest_last.present? ? @contest_leftover = (@contest_last.end_date.utc - Time.now.utc).to_i : @contest_leftover = 0 if @contest_last.nil? Contest.create(:start_date => Time.now.utc, :end_date => Time.now.utc + 10.minutes) elsif @contest_leftover < 0 @winner = Organization.order('votes_count DESC').first @contest_last.update_attributes!(:organization_id => @winner.id, :winner_votes => @winner.votes_count) if @winner.present? Organization.update_all(:votes_count => 0) Contest.create(:start_date => @contest_last.end_date.utc, :end_date => Time.now.utc + 10.minutes) end end My questions: 1) I would like to change the :end_date to something that signifies next Sunday at a certain time (eg. next Sunday at 8pm). Similarly, I could then set the :start_date to to the previous Sunday at a certain time. I saw that there is a sunday() class (http://api.rubyonrails.org/classes/Time.html#method-i-sunday), but not sure how to specify a certain time on that day. 2) For this situation of always wanting the current contest, is there a better way of loading it in the app? Would caching it be better and then reloading if a new one is created? Not sure how this would be done, but seems to be more efficient. Thanks!

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  • Linq to xml, retreaving generic interface-based list

    - by Rita
    I have an xml document that looks like this <Elements> <Element> <DisplayName /> <Type /> </Element> </Elements> I have an interface, interface IElement { string DisplayName {get;} } and a couple of derived classes: public class AElement: IElement public class BElement: IElement What I want to do, is to write the most efficient query to iterate through the xml and create a list of IElement, containing AElement or BElement, based on the 'Type' property in the xml. So far I have this: IEnumerable<AElement> elements = from xmlElement in XElement.Load(path).Elements("Element") where xmlElement.Element("type").Value == "AElement" select new AElement(xmlElement.Element("DisplayName").Value); return elements.Cast<IElement>().ToList(); But this is only for AElement, is there a way to add BElement in the same query, and also make it generic IEnumerable? Or would I have to run this query once for each derived type?

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  • How do I access the names of VB6 modules from code?

    - by Mark Bertenshaw
    Hi All - It is unlikely that there is an answer for this one, but I'm asking anyway. I am currently maintaining some code, which is likely to be refactored soon. Before that happens, I want to make the standard error handling code, which is injected by an Add-In, more efficient and take up less space. One thing that annoys me is that every module has a constant called m_ksModuleName that is used to construct a big string, which is then rethrown from the error handler so we can trace the error stack. This is all template code, i.e. repetivitve, but I could easily strip it down to a procedure call. Now, I have fixed the code so that you can pass the Me reference to the procedure - but you can't do that for the BAS modules. Nor can you access the project name (the part which would be passed as part of a ProgramID, for instance) - although you get given it when you raise an error yourself. All these strings are contained in the EXE, DLL or OCX - believe me, I've used a debugger to find them. But how can I access these in code? -- Mark Bertenshaw

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  • How can I build a generic dataset-handling Perl library?

    - by Pep.
    Hello, I want to build a generic Perl module for handling and analysing biomedical character separated datasets and which can, most certain, be used on any kind of datasets that contain a mixture of categorical (A,B,C,..) and continuous (1.2,3,881..) and identifier (XXX1,XXX2...). The plan is to have people initialize the module and then use some arguments to point to the data file(s), the place were the analysis reports should be placed and the structure of the data. By structure of data I mean which variable is in which place and its name/type. And this is where I need some enlightenment. I am baffled how to do this in a clean way. Obviously, having people create a simple schema file, be it XML or some other format would be the cleanest but maybe not all people enjoy doing something like this. The solutions I can think of are: Create a configuration file in XML or similar and with a prespecified format. Pass the information during initialization of the module. Use the first row of the data as headers and try to guess types (ouch) Surely there must be a "canonical" way of doing this that is also usable and efficient. Thanks p.

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  • cross-platform development for mobile devices

    - by user924
    What language/framework is best worth learning for mobile application development? My specific situation is that I'm very familiar with Java and C++ (I especially love Qt), but have limited experience with other languages. Some options I'm considering: 1) Learn Objective-C and all the iPhone-specific tools I do have access to a mac. The downside here is I'm restricted to the iPhone, so I'd have to rewrite almost everything if I wanted to branch off into another mobile device (or move later to a cross-platform framework). Even after knowing Objective-C, it seems like other frameworks might be more efficient/faster to code in? 2) Use some existing cross-platform framework for development I've looked at rhomobile, but I only have limited experience with Ruby (and at first glance, it might be a little pricey comapred to other options). Appcelerator also looks popular and nice, but it uses html/css/javascript. Airplaysdk looks good, but it's new and I haven't been able to see much written about it (is it worth going for?). 3) Wait for something better to come along How far away is Qt for the iPhone? That would be ideal, but it isn't available now. So what do you recommend? Productivity/efficiency is my top priority, although learning a useful language for the long term would also be okay. Thanks

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  • Sorting arrays in java

    - by user360706
    Write a static method in Java : public static void sortByFour (int[] arr) That receives as a paramater an array full of non-negative numbers (zero or positive) and sorts the array in the following way : In the beginning of the array all the numbers that devide by four without a remainder will appear. After them all the numbers in the array that devide by 4 with a remainder of 1 will appear. After them all the numbers in the array that devide by 4 with a remainder of 2 will appear. In the end of the array all the rest numbers (those who divide by 4 with the remainder 3) will appear. (The order of the numbers in each group doesn't matter) The method must be the most efficient it can. This is what I wrote but unfortunately it doesn't work well... :( public static void swap( int[] arr, int left, int right ) { int temp = arr[left]; arr[left] = arr[right]; arr[right] = temp; } public static void sortByFour( int[] arr ) { int left = 0; int right = ( arr.length - 1 ); int mid = ( arr.length / 2 ); while ( left < right ) { if ( ( arr[left] % 4 ) > ( arr[right] % 4 ) ) { swap( arr, left, right ); right--; } if ( ( arr[left] % 4 ) == ( arr[right] % 4 ) ) left++; else left++; } } Can someone please help me by fixing my code so that it will work well or rewriting it?

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  • Best method to search hierarchical data

    - by WDuffy
    I'm looking at building a facility which allows querying for data with hierarchical filtering. I have a few ideas how I'm going to go about it but was wondering if there are any recommendations or suggestions that might be more efficient. As an example imagine that a user is searching for a job. The job areas would be as follows. 1: Scotland 2: --- West Central 3: ------ Glasgow 4: ------ Etc 5: --- North East 6: ------ Ayrshire 7: ------ Etc A user can search specific (i.e. Glasgow) or in a larger area (i.e. Scotland). The two approaches I am considering are: keep a note of children in the database for each record (i.e. cat 1 would have 2, 3, 4 in its children field) and query against that record with a SELECT * FROM Jobs WHERE Category IN Areas.childrenField. Use a recursive function to find all results who have a relation to the selected area. The problems I see from both are: Holding this data in the db will mean having to keep track of all changes to structure. Recursion is slow and inefficent. Any ideas, suggestion or recommendations on the best approach? I'm using C# ASP.NET with MSSQL 2005 DB.

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  • figuring out which field to look for a value in with SQL and perl

    - by Micah
    I'm not too good with SQL and I know there's probably a much more efficient way to accomplish what I'm doing here, so any help would be much appreciated. Thanks in advance for your input! I'm writing a short program for the local school high school. At this school, juniors and seniors who have driver's licenses and cars can opt to drive to school rather than ride the bus. Each driver is assigned exactly one space, and their DLN is used as the primary key of the driver's table. Makes, models, and colors of cars are stored in a separate cars table, related to the drivers table by the License plate number field. My idea is to have a single search box on the main GUI of the program where the school secretary can type in who/what she's looking for and pull up a list of results. Thing is, she could be typing a license plate number, a car color, make, and model, someone driver's name, some student driver's DLN, or a space number. As the programmer, I don't know what exactly she's looking for, so a couple of options come to mind for me to build to be certain I check everywhere for a match: 1) preform a couple of SELECT * FROM [tablename] SQL statements, one per table and cram the results into arrays in my program, then search across the arrays one element at a time with regex, looking for a matched pattern similar to the search term, and if I find one, add the entire record that had a match in it to a results array to display on screen at the end of the search. 2) take whatever she's looking for into the program as a scaler and prepare multiple select statements around it, such as SELECT * FROM DRIVERS WHERE DLN = $Search_Variable SELECT * FROM DRIVERS WHERE First_Name = $Search_Variable SELECT * FROM CARS WHERE LICENSE = $Search_Variable and so on for each attribute of each table, sticking the results into a results array to show on screen when the search is done. Is there a cleaner way to go about this lookup without having to make her specify exactly what she's looking for? Possibly some kind of SQL statement I've never seen before?

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  • object construct a class of objects in java

    - by Mgccl
    There is a super class, A, and there are many subclasses, B,C,D... people can write more subclasses. Each of the class have the method dostuff(), each is different in some way. I want an object that constructs any object that belong to A or any of it's subclass. For example I can pass the name of the subclass, or a object of that class, and it will construct another object of the class. Of course I can write A construct(A var){ stuff = var.dostuff(); domorestuff(stuff) return new A(stuff); } B construct(B var){ stuff = var.dostuff(); domorestuff(stuff) return new B(stuff); } C construct(C var){ stuff = var.dostuff(); domorestuff(stuff) return new C(stuff); } but this is not efficient. I have to write a few new lines every time I make a new subclass. It seems I can't use generics either. Because I can't use dostuff() on objects not in any of the subclass of A. What should I do in this situation?

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  • How to query the SPView object

    - by Hugo Migneron
    I have a SPView object that contains a lot of SPListItem objects (there are many fields in the view). I am only interested in one of these fields. Let's call it specialField Given that view and specialField, I want to know if a value is contained in specialField. Here is a way of doing what I want to do : String specialField = "Special Field"; String specialValue = "value"; SPList list = SPContext.Current.Site.RootWeb.Lists["My List"]; SPView view = list.Views["My View"]; //This is the view I want to query SPQuery query = new SPQuery(); query.Query = view.Query; SPListItemCollection items = list.GetItems(query); foreach(SPListItem item in items) { var value = item[specialField]; if(value != null) && (value.ToString() == specialValue) { //My value is found. This is what I was looking for. //break out of the loop or return } } //My value is not found. However, iterating through each ListItem hardly seems optimal, especially as there might be hundreds of items. This query will be executed often, so I am looking for an efficient way to do this. EDIT I will not always be working with the same view, so my solution cannot be hardcoded (it has to be generic enough that the list, view and specialField can be changed.

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  • Refining Search Results [PHP/MySQL]

    - by Dae
    I'm creating a set of search panes that allow users to tweak their results set after submitting a query. We pull commonly occurring values in certain fields from the results and display them in order of their popularity - you've all seen this sort of thing on eBay. So, if a lot of rows in our results were created in 2009, we'll be able to click "2009" and see only rows created in that year. What in your opinion is the most efficient way of applying these filters? My working solution was to discard entries from the results that didn't match the extra arguments, like: while($row = mysql_fetch_assoc($query)) { foreach($_GET as $key => $val) { if($val !== $row[$key]) { continue 2; } } // Output... } This method should hopefully only query the database once in effect, as adding filters doesn't change the query - MySQL can cache and reuse one data set. On the downside it makes pagination a bit of a headache. The obvious alternative would be to build any additional criteria into the initial query, something like: $sql = "SELECT * FROM tbl MATCH (title, description) AGAINST ('$search_term')"; foreach($_GET as $key => $var) { $sql .= " AND ".$key." = ".$var; } Are there good reasons to do this instead? Or are there better options altogether? Maybe a temporary table? Any thoughts much appreciated!

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  • Quickest way to compare a bunch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • Best Functional Approach

    - by dbyrne
    I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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  • How does the NY Times iPhone app do this?

    - by ArgMan
    Alright, I have an RSS feed that gets arranged in a UITableView and then the user selects a story and it loads in a UIWebView. However, I'd like to stop using the UIWebView and just use a UITextView or UILabel. This png is what I am trying to do (just display the various text aspects of a news story): http://img411.imageshack.us/img411/2449/screenshot20100315at120.png Let me start off by saying that I have tried to use the usualNSString *myText = [webView stringByEvaluatingJavaScriptFromString:@"document.documentElement.textContent"]; and assign it to a UILabel, but it doesn't work the way that I am implementing it (in webViewDidFinishLoad--is that not correct?) and I get a blank textView and normal webView. If I overlay a UITextView on top of a UIWebView on its own (that is, a webView that just loads one page), the code posted above works fine to display the text I require, but the problem arises when the RSS feed is added into the mix. Ideas and/or help, guys? I've been stuck wondering why this doesn't work as it should for a few days now. If you have a better, more efficient way of doing it then placing the code in webViewDidFinishLoad, please let me know! Does it go in my didSelectRowAtIndexPath? I'm lost here, guys. Thank you very much in advance!

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  • Optimize a views drawing code

    - by xon1c
    Hi, in a simple drawing application I have a model which has a NSMutableArray curvedPaths holding all the lines the user has drawn. A line itself is also a NSMutableArray, containing the point objects. As I draw curved NSBezier paths, my point array has the following structure: linePoint, controlPoint, controlPoint, linePoint, controlPoint, controlPoint, etc... I thought having one array holding all the points plus control points would be more efficient than dealing with 2 or 3 different arrays. Obviously my view draws the paths it gets from the model, which leads to the actual question: Is there a way to optimize the following code (inside the view's drawRect method) in terms of speed? int lineCount = [[model curvedPaths] count]; // Go through paths for (int i=0; i < lineCount; i++) { // Get the Color NSColor *theColor = [model getColorOfPath:[[model curvedPaths] objectAtIndex:i]]; // Get the points NSArray *thePoints = [model getPointsOfPath:[[model curvedPaths] objectAtIndex:i]]; // Create a new path for performance reasons NSBezierPath *path = [[NSBezierPath alloc] init]; // Set the color [theColor set]; // Move to first point without drawing [path moveToPoint:[[thePoints objectAtIndex:0] myNSPoint]]; int pointCount = [thePoints count] - 3; // Go through points for (int j=0; j < pointCount; j+=3) { [path curveToPoint:[[thePoints objectAtIndex:j+3] myNSPoint] controlPoint1:[[thePoints objectAtIndex:j+1] myNSPoint] controlPoint2:[[thePoints objectAtIndex:j+2] myNSPoint]]; } // Draw the path [path stroke]; // Bye stuff [path release]; [theColor release]; } Thanks, xonic

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  • what is the best way to optimize my json on an asp.net-mvc site

    - by ooo
    i am currently using jqgrid on an asp.net mvc site and we have a pretty slow network (internal application) and it seems to be taking the grid a long time to load (the issue is both network as well as parsing, rendering) I am trying to determine how to minimized what i send over to the client to make it as fast as possible. Here is a simplified view of my controller action to load data into the grid: [AcceptVerbs(HttpVerbs.Get)] public ActionResult GridData1(GridData args) { var paginatedData = applications.GridPaginate(args.page ?? 1, args.rows ?? 10, i => new { i.Id, Name = "<div class='showDescription' id= '" + i.id+ "'>" + i.Name + "</div>", MyValue = GetImageUrl(_map, i.value, "star"), ExternalId = string.Format("<a href=\"{0}\" target=\"_blank\">{1}</a>", Url.Action("Link", "Order", new { id = i.id }), i.Id), i.Target, i.Owner, EndDate = i.EndDate, Updated = "<div class='showView' aitId= '" + i.AitId + "'>" + GetImage(i.EndDateColumn, "star") + "</div>", }) return Json(paginatedData); } So i am building up a json data (i have about 200 records of the above) and sending it back to the GUI to put in the jqgrid. The one thing i can thihk of is Repeated data. In some of the json fields i am appending HTML on top of the raw "data". This is the same HTML on every record. It seems like it would be more efficient if i could just send the data and "append" the HTML around it on the client side. Is this possible? Then i would just be sending the actual data over the wire and have the client side add on the rest of the HTML tags (the divs, etc) be put together. Also, if there are any other suggestions on how i can minimize the size of my messages, that would be great. I guess at some point these solution will increase the client side load but it may be worth it to cut down on network traffic.

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  • read files from directory and filter files from Java

    - by Adnan
    The following codes goes through all directories and sub-directories and outputs just .java files; import java.io.File; public class DirectoryReader { private static String extension = "none"; private static String fileName; public static void main(String[] args ){ String dir = "C:/tmp"; File aFile = new File(dir); ReadDirectory(aFile); } private static void ReadDirectory(File aFile) { File[] listOfFiles = aFile.listFiles(); if (aFile.isDirectory()) { listOfFiles = aFile.listFiles(); if(listOfFiles!=null) { for(int i=0; i < listOfFiles.length; i++ ) { if (listOfFiles[i].isFile()) { fileName = listOfFiles[i].toString(); int dotPos = fileName.lastIndexOf("."); if (dotPos > 0) { extension = fileName.substring(dotPos); } if (extension.equals(".java")) { System.out.println("FILE:" + listOfFiles[i] ); } } if(listOfFiles[i].isDirectory()) { ReadDirectory(listOfFiles[i]); } } } } } } Is this efficient? What could be done to increase the speed? All ideas are welcome.

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  • Standard term for a thread I/O reorder buffer?

    - by Crashworks
    I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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  • Replacing words in string

    - by abkai
    Okay, so I have the following little function: def swap(inp): inp = inp.split() out = "" for item in inp: ind = inp.index(item) item = item.replace("i am", "you are") item = item.replace("you are", "I am") item = item.replace("i'm", "you're") item = item.replace("you're", "I'm") item = item.replace("my", "your") item = item.replace("your", "my") item = item.replace("you", "I") item = item.replace("my", "your") item = item.replace("i", "you") inp[ind] = item for item in inp: ind = inp.index(item) item = item + " " inp[ind] = item return out.join(inp) Which, while it's not particularly efficient gets the job done for shorter sentences. Basically, all it does is swaps pronoun etc. perspectives. This is fine when I throw a string like "I love you" at it, it returns "you love me" but when I throw something like: you love your version of my couch because I love you, and you're a couch-lover. I get: I love your versyouon of your couch because I love I, and I'm a couch-lover. I'm confused as to why this is happening. I explicitly split the string into a list to avoid this. Why would it be able to detect it as being a part of a list item, rather than just an exact match? Also, slightly deviating to avoid having to post another question so similar; if a solution to this breaks this function, what will happen to commas, full stops, other punctuation? It made some very surprising mistakes. My expected output is: I love my version of your couch because you love I, and I'm a couch-lover. The reason I formatted it like this, is because I eventually hope to be able to replace the item.replace(x, y) variables with words in a database.

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  • Data structure to build and lookup set of integer ranges

    - by actual
    I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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