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• Using UIImageViews for 'pages' in an iPhone/iPad storybook app?

  - by outtoplayinc

  I'm new to iPhone programming, and well, what seems obvious to me may seem silly to a seasoned coder. I did a few 'switching views' tutorials on Youtube, and basically, they seems to work nicely for adding pages to a storybook type app. You add a UIViewController and associated view for each page. My question is would this become insanely slow, or a memory hog if I continued this method for say....35+ pages? Each page would also have a sound file associated with it that would play narration when a page load and stops when we leave. Basically, think of a powerpoint type app, with sound, possibly animated image elements, next & back buttons. I'm probably thinking of this very simplistically, but that's where my experience is at for the moment. Any insight or tips as to better and or more efficient ways to proceed would be greatly appreciated.

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• How to solve recursion relations in mathematica efficiently?

  - by Qiang Li

  I have a recursion to solve for. f(m,n)=Sum[f[m - 1, n - 1 - i] + f[m - 3, n - 5 - i], {i, 2, n - 2*m + 2}] + f[m - 1, n - 3] + f[m - 3, n - 7] f(0,n)=1, f(1,n)=n However, the following mma code is very inefficient f[m_, n_] := Module[{}, If[m < 0, Return[0];]; If[m == 0, Return[1];]; If[m == 1, Return[n];]; Return[Sum[f[m - 1, n - 1 - i] + f[m - 3, n - 5 - i], {i, 2, n - 2*m + 2}] + f[m - 1, n - 3] + f[m - 3, n - 7]];] It takes unbearably long to compute f[40,20]. Could anyone please suggest an efficient way of doing this? Many thanks!

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• C#, Fastest (Best?) Method of Identifying Duplicate Files in an Array of Directories

  - by Nate Greenwood

  I want to recurse several directories and find duplicate files between the n number of directories. My knee-jerk idea at this is to have a global hashtable or some other data structure to hold each file I find; then check each subsequent file to determine if it's in the "master" list of files. Obviously, I don't think this would be very efficient and the "there's got to be a better way!" keeps ringing in my brain. Any advice on a better way to handle this situation would be appreciated.

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• Sorting 2 arrays that have been added together

  - by tyler

  In my app, users can create galleries that their work may or may not be in. Users have and belong to many Galleries, and each gallery has a 'creator' that is designated by the gallery's user_id field. So to get the 5 latest galleries a user is in, I can do something like: included_in = @user.galleries.order('created_at DESC').uniq.first(5) # SELECT DISTINCT "galleries".* FROM "galleries" INNER JOIN "galleries_users" ON "galleries"."id" = "galleries_users"."gallery_id" WHERE "galleries_users"."user_id" = 10 ORDER BY created_at DESC LIMIT 5 and to get the 5 latest galleries they've created, I can do: created = Gallery.where(user_id: id).order('created_at DESC').uniq.first(5) # SELECT DISTINCT "galleries".* FROM "galleries" WHERE "galleries"."user_id" = 10 ORDER BY created_at DESC LIMIT 5 I want to display these two together, so that it's the 5 latest galleries that they've created OR they're in. Something like the equivalent of: (included_in + created).order('created_at DESC').uniq.first(5) Does anyone know how to construct an efficient query or post-query loop that does this?

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• Best Design Pattern to Implement while Mapping Actions in MVC

  - by FidEliO

  What could be the best practices of writing the following case: We have a controller which based on what paths users take, take different actions. For example: if user chooses the path /path1/hello it will say hello. If a user chooses /path1/bye?name="Philipp" it will invoke sayGoodBye() and etc. I have written a switch statement inside the controller which is simple, however IMO not efficient. What are the best way to implement this, considering that paths are generally String. private void takeAction() { switch (path[1]) { case "hello": //sayHello(); break; case "bye": //sayBye(); break; case "case3": //Blah(); break; ... } }

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• Is it a good idea to apply some basic macros to simplify code in a large project?

  - by DoctorT

  I've been working on a foundational c++ library for some time now, and there are a variety of ideas I've had that could really simplify the code writing and managing process. One of these is the concept of introducing some macros to help simplify statements that appear very often, but are a bit more complicated than should be necessary. For example, I've come up with this basic macro to simplify the most common type of for loop: #define loop(v,n) for(unsigned long v=0; v<n; ++v) This would enable you to replace those clunky for loops you see so much of: for (int i = 0, i < max_things; i++) With something much easier to write, and even slightly more efficient: loop (i, max_things) Is it a good idea to use conventions like this? Are there any problems you might run into with different types of compilers? Would it just be too confusing for someone unfamiliar with the macro(s)?

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• Displaying objects based on if a user is logged in or not

  - by MaxMackie

  I'm learning about PHP sessions for user authentication on my website. I know how to restrict the viewing of a complete page using sessions (simply check if the 'uid' session variable is set and if it is, show content, if not redirect to an error). However I'm trying to figure out the best way to selectively show and hide different objects (div, text, images) based on if a user is logged in or not. Is it as simple as checking for the 'uid' session variable and displaying based on if it set or not? Is there a more efficient way of doing this id there are a lot of conditional elements on a page?

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• Javascript find if english alphabets only

  - by Alec Smart

  Hello, Am trying to find some text only if it contains english letters and numbers using Javascript/jQuery. Am wondering what is the most efficient way to do this? Since there could be thousands of words, it should be as fast as possible and I don't want to use regex. var names[0] = 'test'; var names[1] = '???'; var names[2] = '??????'; for (i=0;i<names.length;i++) { if (names[i] == ENGLISHMATCHCODEHERE) { // do something here } } Thank you for your time.

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• Appengine backreferences - need composite index?

  - by davezor

  I have a query that is very recently starting to throw: "The built-in indices are not efficient enough for this query and your data. Please add a composite index for this query." I checked the line on which this exception is being thrown, and the problem query is this one: count = self.vote_set.filter("direction =", 1).count() This is literally a one-filter operation using appengine's built-in backreferences. I have no idea how to optimize this query...anyone have any suggestions? I tried to add this index: - kind: Vote properties: - name: direction direction: desc - kind: Vote properties: - name: direction And I got a message (obviously) saying this was an unnecessary index. Thanks for your help in advance.

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• Use count or have a field that tallies?

  - by Dan LaManna

  Fairly simple concept, making an extremely basic message board system and I want users to have a post count. Now I was debating on whether or not to have a tally in their row that is added each time a post by them is created, or subtracted by one each time a post of theirs is deleted. However I'm sure that performing a count query when the post count is requested would be more accurate due to unforseen circumstances (say a thread gets deleted and it doesn't lower their tally properly), however this seems like it would be less efficient to run a query EVERY time their post count is loaded, especially in the case of them having 10 posts on the same page and it lists their post count each post. Thoughts/Advice? Thanks

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• solutions for rapid front-end development?

  - by fayer

  im using mvc framework and i have learned some techniques that help me with different parts of RAD. models: doctrine/visual paradigm controllers/libraries: various design patterns now i only need to know what technique/solution i should use for the views so that i can create views more rapidly. cause i don't think it's efficient to code css/html manually, even though i understand it. its the same principle when using visual paradigm to create both my mysql database tables and doctrine model classes. i believe in using right tools will boost up development speed. so what could i use for the views to save time and energy and don't reinvent the wheel all the time? dreamweaver? any css generation tools? 960/blueprint for layout? suggestions? thanks

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• Python - Create a list with initial capacity

  - by Claudiu

  Code like this often happens: l = [] while foo: #baz l.append(bar) #qux This is really slow if you're about to append thousands of elements to your list, as the list will have to constantly be re-initialized to grow. (I understand that lists aren't just wrappers around some array-type-thing, but something more complicated. I think this still applies, though; let me know if not). In Java, you can create an ArrayList with an initial capacity. If you have some idea how big your list will be, this will be a lot more efficient. I understand that code like this can often be re-factored into a list comprehension. If the for/while loop is very complicated, though, this is unfeasible. Is there any equivalent for us python programmers?

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• How do I ensure data consistency in this concurrent situation?

  - by MalcomTucker

  The problem is this: I have multiple competing threads (100+) that need to access one database table Each thread will pass a String name - where that name exists in the table, the database should return the id for the row, where the name doesn't already exist, the name should be inserted and the id returned. There can only ever be one instance of name in the database - ie. name must be unique How do I ensure that thread one doesn't insert name1 at the same time as thread two also tries to insert name1? In other words, how do I guarantee the uniqueness of name in a concurrent environment? This also needs to be as efficient as possible - this has the potential to be a serious bottleneck. I am using MySQL and Java. Thanks

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• best method for creating a universal extention/plugin

  - by rashcroft44

  Hi, I'm looking to create an extension for the leading browsers (firefox, safari and ie). Its rather simple, and I'm looking for the most efficient way to go about this. I need to get the hostname of the current site the user is on, and if it matches a certain parameter(eg, mysite.org), I'll need to append to the link some extra data and refresh to the new link. What is the simplest way to go about this? (I don't want to go in the direction of a bookmarklet - since this would require the user to click. I'd like this to happen automatically) sort of something like this: if(window.location.hostname == 'mysite.org') { location.replace(document.location.href + '/&mystuff=xyz'); } Thanks!

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• Overhead of serving pages - JSPs vs. PHP vs. ASPXs vs. C

  - by John Shedletsky

  I am interested in writing my own internet ad server. I want to serve billions of impressions with as little hardware possible. Which server-side technologies are best suited for this task? I am asking about the relative overhead of serving my ad pages as either pages rendered by PHP, or Java, or .net, or coding Http responses directly in C and writing some multi-socket IO monster to serve requests (I assume this one wins, but if my assumption is wrong, that would actually be most interesting). Obviously all the most efficient optimizations are done at the algorithm level, but I figure there has got to be some speed differences at the end of the day that makes one method of serving ads better than another. How much overhead does something like apache or IIS introduce? There's got to be a ton of extra junk in there I don't need. At some point I guess this is more a question of which platform/language combo is best suited - please excuse the in-adroitly posed question, hopefully you understand what I am trying to get at.

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• Is scala functional programming slower than traditional coding?

  - by Fred Haslam

  In one of my first attempts to create functional code, I ran into a performance issue. I started with a common task - multiply the elements of two arrays and sum up the results: var first:Array[Float] ... var second:Array[Float] ... var sum=0f; for(ix<-0 until first.length) sum += first(ix) * second(ix); Here is how I reformed the work: sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_) When I benchmarked the two approaches, the second method takes 40 times as long to complete! Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

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• Efficiently draw a grid in Windows Forms

  - by Joel

  I'm writing an implementation of Conway's Game of Life in C#. This is the code I'm using to draw the grid, it's in my panel_Paint event. g is the graphics context. for (int y = 0; y < numOfCells * cellSize; y += cellSize) { for (int x = 0; x < numOfCells * cellSize; x += cellSize) { g.DrawLine(p, x, 0, x, y + numOfCells * cellSize); g.DrawLine(p, 0, x, y + size * drawnGrid, x); } } When I run my program, it is unresponsive until it finishes drawing the grid, which takes a few seconds at numOfCells = 100 & cellSize = 10. Removing all the multiplication makes it faster, but not by very much. Is there a better/more efficient way to draw my grid? Thanks

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• ColdFusion Timeout Error

  - by Jason

  I have a scheduled task that runs once a day that builds an XML file that I pass off to another group. Recently the amount of data has greatly increased and is now causing the task to time out (I think). I have tried to optimize my script as much as possible but with no luck. It times out long before an hour and I don't get any kind of ColdFusion error. Instead I get a "This page cannot be found" after it runs. Could this be a timeout someplace other than Coldfusion? Is there a more efficient way to build this XML file? select PersonID, FirstName, LastName from People select d.DepartmentID, DepartmentName, pd.PersonID from Department d inner join PersonDepartment pd on d.DepartmentID = pd.DepartmentID select PaperID, PaperTitle, PaperDescription, pp.PersonID from Paper p inner join PersonPaper pp on p.PaperID = pp.PaperID select DepartmentID, DepartmentName from getDepartments where PersonID = #getPeople.PersonID# select PaperID, PaperDescription from getpapers where PersonID = #getPeople.PersonID# #getPeople.PersonID# #getPeople.Firstname# #getPeople.LastName# #getPersonDepartments.DepartmentID# #getPersonDepartments.DepartmentName# #getPersonPapers.PaperID# #getPersonPapers.PaperDescription# Done!

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• Store data in an inconvenient table or create a derived table?

  - by user1705685

  I have a certain predefined database structure that I am stuck with. The question is whether this structure is OK for ORM or I whether should add a processing layer that would create a more convenient structure every time something is inserted into the original DB. To simplify, here's what it kind of looks like. I have a person table: PersonId Name And I have a properties table: PersonId PropertyType PropertyValue So, for person John Doe... (1, 'John Doe') ...I could have three properties: (1, 'phone', '555-55-55'), (1, 'email', '[email protected]), (1, 'type', 'employee') By using ORM I would like to get a "person" object that would have properties "name", "phone", "email", "type". Can Propel do that? How efficient is it? Is it a better idea to create a table with columns "phone", "email", "type" and fill it automatically as new rows are inserted into the properties table?

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• JavaScript BubbleSort

  - by Alyn

  Hi, Have a bubblesort routine similar the this. I need to make it more efficient by stopping the loop when the array is sorted or if the array is already sorted. function sortNumbers(listbox) { var x, y, holder; // The Bubble Sort method. for(x = 0; x < ranarray.length; x++) { for(y = 0; y < (ranarray.length-1); y++) { if(ranarray[y] > ranarray[y+1]) { holder = ranarray[y+1]; ranarray[y+1] = ranarray[y]; ranarray[y] = holder; } } }

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• which is time consuming construct in following program?

  - by user388338

  while submitting a solution for practise problem 6(odd) i got TLE error but while using using print and scanf in place cin and cout my sol was submitted successfully with 0.77s time..i want to know how can i make it more efficient link to problem is codechef problem 6 #include<iostream> #include<cstdio> using namespace std; int main() {int n,N; scanf("%d",&n); for(int l=0;l<n;l++) { scanf("%d",&N); int i=0,x; if(N<=0) continue; for(;N>=(x=(2<<i));i++); printf("%d",x/2); cout<<"\n"; } }

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• Efficiently Reshaping/Reordering Numpy Array to Properly Ordered Tiles (Image)

  - by Phelix

  I would like to be able to somehow reorder a numpy array for efficient processing of tiles. what I got: >>> A = np.array([[1,2],[3,4]]).repeat(2,0).repeat(2,1) >>> A # image like array array([[[1, 1, 2, 2], [1, 1, 2, 2]], [[3, 3, 4, 4], [3, 3, 4, 4]]]) >>> A.reshape(2,2,4) array([[[1, 1, 2, 2], [1, 1, 2, 2]], [[3, 3, 4, 4], [3, 3, 4, 4]]]) what I want: X >>> X array([[[1, 1, 1, 1], [2, 2, 2, 2]], [[3, 3, 3, 3], [4, 4, 4, 4]]]) to be able to do something like: >>> X[X.sum(2)>12] -= 1 >>> X array([[[1, 1, 1, 1], [2, 2, 2, 2]], [[3, 3, 3, 3], [3, 3, 3, 3]]]) Is this possible without a slow python loop? Bonus: Conversion back from X to A Edit: How can I get X from A?

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• Custom deleters for std::shared_ptrs

  - by Kristian D'Amato

  Is it possible to use a custom deleter after creating a std::shared_ptr without using new? My problem is that object creation is handled by a factory class and its constructors & destructors are protected, which gives a compile error, and I don't want to use new because of its drawbacks. To elaborate: I prefer to create shared pointers like this, which doesn't let you set a custom deleter (I think): auto sp1 = make_shared<Song>(L"The Beatles", L"Im Happy Just to Dance With You"); Or I can create them like this, which does let met set a deleter through an argument: auto sp2(new Song, MyDeleterFunc); But the second one uses new, which AFAIK isn't as efficient as the top sort of allocation. Maybe this is clearer: is it possible to get the benefits of make_shared<> as well as a custom deleter? Would that mean having to write an allocator?

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• C# GroupJoin efficiency

  - by bsnote

  without using GroupJoin: var playersDictionary = players.ToDictionary(player => player.Id, element => new PlayerDto { Rounds = new List<RoundDto>() }); foreach (var round in rounds) { PlayerDto playerDto; playersDictionary.TryGetValue(round.PlayerId, out playerDto); if (playerDto != null) { playerDto.Rounds.Add(new RoundDto { }); } } var playerDtoItems = playersDictionary.Values; using GroupJoin: var playerDtoItems = from player in players join round in rounds on player.Id equals round.PlayerId into playerRounds select new PlayerDto { Rounds = playerRounds.Select(playerRound => new RoundDto {}) }; Which of these two pieces is more efficient?

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• Algorithm to Group All the Cycles Together

  - by Ngu Soon Hui

  I have a lot of cycles ( indicated by numeric values, for example, 1-2-3-4 corresponds to a cycle, with 4 edges, edge 1 is {1:2}, edge 2 is {2:3}, edge 3 is {3,4}, edge 4 is {4,1}, and so on). A cycle is said to be connected to another cycle if they share one and only one edge. For example, let's say I have two cycles 1-2-3-4 and 5-6-7-8, then there are two cycle groups because these two cycles are not connecting to each other. If I have two cycles 1-2-3-4 and 3-4-5-6, then I have only one cycle group because these two cycles share the same edge. What is the most efficient way to find all the cycle groups?

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