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• Optimized 2D Tile Scrolling in OpenGL

  - by silicus

  Hello, I'm developing a 2D sidescrolling game and I need to optimize my tiling code to get a better frame rate. As of right now I'm using a texture atlas and 16x16 tiles for 480x320 screen resolution. The level scrolls in both directions, and is significantly larger than 1 screen (thousands of pixels). I use glTranslate for the actual scrolling. So far I've tried: Drawing only the on-screen tiles using glTriangles, 2 per square tile (too much overhead) Drawing the entire map as a Display List (great on a small level, way to slow on a large one) Partitioning the map into Display Lists half the size of the screen, then culling display lists (still slows down for 2-directional scrolling, overdraw is not efficient) Any advice is appreciated, but in particular I'm wondering: I've seen Vertex Arrays/VBOs suggested for this because they're dynamic. What's the best way to take advantage of this? If I simply keep 1 screen of vertices plus a bit of overdraw, I'd have to recopy the array every few frames to account for the change in relative coordinates (shift everything over and add the new rows/columns). If I use more overdraw this doesn't seem like a big win; it's like the half-screen display list idea. Does glScissor give any gain if used on a bunch of small tiles like this, be it a display list or a vertex array/VBO Would it be better just to build the level out of large textures and then use glScissor? Would losing the memory saving of tiling be an issue for mobile development if I do this (just curious, I'm currently on a PC)? This approach was mentioned here Thanks :)

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• Rails: creating a model in the new action

  - by Joseph Silvashy

  I have an interesting situation, well it's probably not that unique at all, but I'm not totally sure how to tackle it. I have a model, in this case a recipe and the user navigates to the new path /recipes/new however the situation is that I need to be able to have the user upload images and make associations to that model in the new action, but the model doesn't have an ID yet. So I assume I need to rethink my controller, but I don't want to have redirects and whatnot, how can accomplish this? Here is the basic controller, barebones obviously: ... def new # I should be creating the model first, so it has an ID @recipe = Recipe.new end def create @recipe = Recipe.new(params[:recipe]) if @recipe.save redirect_to @recipe else render 'new' end end ... update Perhaps I can have a column thats like state which could have values like new/incomplete/complete or what-have-you. I'm mostly trying to figure out what would also be most efficient for the DB. It would be nice if I could still have a url that said '/new', instead of it be the edit path with the id, for usability sake, but I'm not sure this can be simply accomplished in the new action of my controller. Thoughts?

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• What is the best way to get a reference to a spring bean in the backend layers?

  - by java_pill

  I have two spring config files and I'm specifying them in my web.xml as in below. web.xml snippet .. <context-param> <param-name>contextConfigLocation</param-name> <param-value>WEB-INF/classes/domain-context.xml WEB-INF/classes/client-ws.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> .. From my domain object I have to invoke a Web Service Client and in order to get a reference to the Web Service client I do this: ApplicationContext context = new ClassPathXmlApplicationContext("client-ws.xml"); //b'cos I don't want to use WebApplicationContextUtils ProductServiceClient client = (ProductServiceClient) context.getBean("productClient"); .. client.find(prodID); //calls a Web Service .. However, I have concerns that looking up the client-ws.xml file and getting a reference to the ProductServiceClient bean is not efficient. I thought of getting it using WebApplicationContextUtils. However, I don't want my domain objects to have a dependency on the ServletContext (a web/control layer object) because WebApplicationContextUtils depends on ServletContext. What is the best way to get a reference to a spring bean in the backend layers? Thanks!

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• How to get notified about changes of the history via history.pushState?

  - by Felix Kling

  So now that HTML5 introduces history.pushState to change the browsers history, websites start using this in combination with Ajax instead of changing the fragment identifier of the URL. Sadly that means that those calls cannot be detect anymore by onhashchange. My question is: Is there a reliable way (hack? ;)) to detect when a website uses history.pushState? The specification does not state anything about events that are raised (at least I couldn't find anything). I tried to create a facade and replaced window.history with my own JavaScript object, but it didn't have any effect at all. Further explanation: I'm developing a Firefox add-on that needs to detect these changes and act accordingly. I know there was a similar question a few days ago that asked whether listening to some DOM events would be efficient but I would rather not rely on that because these events can be generated for a lot of different reasons. Update: Here is a jsfiddle (use Firefox 4 or Chrome 8) that shows that onpopstate is not triggered when pushState is called (or am I doing something wrong? Feel free to improve it!). Update 2: Another (side) problem is that window.location is not updated when using pushState (but I read about this already here on SO I think).

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• Better way to compare neighboring cells in matrix

  - by HyperCube

  Suppose I have a matrix of size 100x100 and I would like to compare each pixel to its direct neighbor (left, upper, right, lower) and then do some operations on the current matrix or a new one of the same size. A sample code in Python/Numpy could look like the following: (the comparison 0.5 has no meaning, I just want to give a working example for some operation while comparing the neighbors) import numpy as np my_matrix = np.random.rand(100,100) new_matrix = np.array((100,100)) my_range = np.arange(1,99) for i in my_range: for j in my_range: if my_matrix[i,j+1] > 0.5: new_matrix[i,j+1] = 1 if my_matrix[i,j-1] > 0.5: new_matrix[i,j-1] = 1 if my_matrix[i+1,j] > 0.5: new_matrix[i+1,j] = 1 if my_matrix[i-1,j] > 0.5: new_matrix[i-1,j] = 1 if my_matrix[i+1,j+1] > 0.5: new_matrix[i+1,j+1] = 1 if my_matrix[i+1,j-1] > 0.5: new_matrix[i+1,j-1] = 1 if my_matrix[i-1,j+1] > 0.5: new_matrix[i-1,j+1] = 1 This can get really nasty if I want to step into one neighboring cell and start from it to do a similar task... Do you have some suggestions how this can be done in a more efficient manner? Is this even possible?

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• How can multiple variables be passed to a function cleanly in C?

  - by aquanar

  I am working on an embedded system that has different output capabilities (digital out, serial, analog, etc). I am trying to figure out a clean way to pass many of the variables that will control those functions. I don't need to pass ALL of them too often, but I was hoping to have a function that would read the input data (in this case from a TCP network), and then parse the data (IE, the 3rd byte contains the states of 8 of the digital outputs (according to which bit in that byte is high or low)), and put that into a variable where I can then use elsewhere in the program. I wanted that function to be separate from the main() function, but to do so would require passing pointers to some 20 or so variables that it would be writing to. I know I could make the variables global, but I am trying to make it easier to debug by making it obvious when a function is allowed to edit that variable, by passing it to the function. My best idea was a struct, and just pass a pointer to it, but wasn't sure if there was a more efficient way, especially since there is only really 1 function that would need to access all of them at once, while most others only require parts of the information that will be stored in this bunch of state variables. So anyway, is there a clean way to send many variables between functions at once that need to be edited?

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• What's a good way to do testing a plug-in on multiple Windows and Outlook versions?

  - by Andrei

  Hello, We're building a plug-in for Outlook that should work on multiple Windows versions (XP, Vista, 7) and also with different Outlook versions (2003, 2007, 2010). The testing problem I am facing right now, is that I can't figure out a good/convenient/thorough way to test the application on multiple Windows and Outlook versions. At the moment, I have a VirtualBox which runs many virtual machines, with different Windows versions and Outlook versions. So I would have a virtual machine with Windows 7 testing Outlook 2010, and another one with Windows 7 testing Outlook 2007, Windows Vista with Outlook 2010 and so on, going through some of the possible combinations. It kind of gets the job done, although it is cumbersome and takes a long time to test. Some of the testing included in the application is unit testing, but this is also rather tied in with the machine I test it on (windows 7 with outlook 2010). For example, I was using ManagementObject recently, which worked fine on my system (and thus passed the unit test for that method), however, using that object threw an exception in another person's system, which crashed the application. I work on Visual Studio 2010 Ultimate. The questions: Is there a more elegant way to make the testing process more streamline and more efficient? Any other testing methods you recommend? How would you deal with this problem? Thanks! Looking forward to your replies.

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• Parallelizing L2S Entity Retrieval

  - by MarkB

  Assuming a typical domain entity approach with SQL Server and a dbml/L2S DAL with a logic layer on top of that: In situations where lazy loading is not an option, I have settled on a convention where getting a list of entities does not also get each item's child entities (no loading), but getting a single entity does (eager loading). Since getting a single entity also gets children, it causes a cascading effect in which each child then gets its children too. This sounds bad, but as long as the model is not too deep, I usually don't see performance problems that outweigh the benefits of the ease of use. So if I want to get a list in which each of the items is fully hydrated with children, I combine the GetList and GetItem methods. So I'll get a list and then loop through it getting each item with the full cascade. Even this is generally acceptable in many of the projects I've worked on - but I have recently encountered situations with larger models and/or more data in which it needs to be more efficient. I've found that partitioning the loop and executing it on multiple threads yields excellent results. In my first experiment with a list of 50 items from one particular project, I did 5 threads of 10 items each and got a 3X improvement in time. Of course, the mileage will vary depending on the project but all else being equal this is clearly a big opportunity. However, before I go further, I was wondering what others have done that have already been through this. What are some good approaches to parallelizing this type of thing?

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• Logic: Best way to sample & count bytes of a 100MB+ file

  - by Jami

  Let's say I have this 170mb file (roughly 180 million bytes). What I need to do is to create a table that lists: all 4096 byte combinations found [column 'bytes'], and the number of times each byte combination appeared in it [column 'occurrences'] Assume two things: I can save data very fast, but I can update my saved data very slow. How should I sample the file and save the needed information? Here're some suggestions that are (extremely) slow: Go through each 4096 byte combinations in the file, save each data, but search the table first for existing combinations and update it's values. this is unbelievably slow Go through each 4096 byte combinations in the file, save until 1 million rows of data in a temporary table. Go through that table and fix the entries (combine repeating byte combinations), then copy to the big table. Repeat going through another 1 million rows of data and repeat the process. this is faster by a bit, but still unbelievably slow This is kind of like taking the statistics of the file. NOTE: I know that sampling the file can generate tons of data (around 22Gb from experience), and I know that any solution posted would take a bit of time to finish. I need the most efficient saving process

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• Interview Q: sorting an almost sorted array (elements misplaced by no more than k)

  - by polygenelubricants

  I was asked this interview question recently: You're given an array that is almost sorted, in that each of the N elements may be misplaced by no more than k positions from the correct sorted order. Find a space-and-time efficient algorithm to sort the array. I have an O(N log k) solution as follows. Let's denote arr[0..n) to mean the elements of the array from index 0 (inclusive) to N (exclusive). Sort arr[0..2k) Now we know that arr[0..k) are in their final sorted positions... ...but arr[k..2k) may still be misplaced by k! Sort arr[k..3k) Now we know that arr[k..2k) are in their final sorted positions... ...but arr[2k..3k) may still be misplaced by k Sort arr[2k..4k) .... Until you sort arr[ik..N), then you're done! This final step may be cheaper than the other steps when you have less than 2k elements left In each step, you sort at most 2k elements in O(k log k), putting at least k elements in their final sorted positions at the end of each step. There are O(N/k) steps, so the overall complexity is O(N log k). My questions are: Is O(N log k) optimal? Can this be improved upon? Can you do this without (partially) re-sorting the same elements?

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• merging two tables, while applying aggregates on the duplicates (max,min and sum)

  - by cloudraven

  I have a table (let's call it log) with a few millions of records. Among the fields I have Id, Count, FirstHit, LastHit. Id - The record id Count - number of times this Id has been reported FirstHit - earliest timestamp with which this Id was reported LastHit - latest timestamp with which this Id was reported This table only has one record for any given Id Everyday I get into another table (let's call it feed) with around half a million records with these fields among many others: Id Timestamp - Entry date and time. This table can have many records for the same id What I want to do is to update log in the following way. Count - log count value, plus the count() of records for that id found in feed FirstHit - the earliest of the current value in log or the minimum value in feed for that id LastHit - the latest of the current value in log or the maximum value in feed for that id. It should be noticed that many of the ids in feed are already in log. The simple thing that worked is to create a temporary table and insert into it the union of both as in Select Id, Min(Timestamp) As FirstHit, MAX(Timestamp) as LastHit, Count(*) as Count FROM feed GROUP BY Id UNION ALL Select Id, FirstHit,LastHit,Count FROM log; From that temporary table I do a select that aggregates Min(firsthit), max(lasthit) and sum(Count) Select Id, Min(FirstHit),Max(LastHit),Sum(Count) FROM @temp GROUP BY Id; and that gives me the end result. I could then delete everything from log and replace it with everything with temp, or craft an update for the common records and insert the new ones. However, I think both are highly inefficient. Is there a more efficient way of doing this. Perhaps doing the update in place in the log table?

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• Is programming overrated?

  - by aengine

  [Subjective and intended to be a community wiki] I am sorry for such an offensive question: But here are my arguments Most of the progress in "computing" has came from non-programming sources. i.e. People invented faster microprocessors and better routers and novel memory devices. I dont think on average people are writting more efficient programs than those written 10 years ago. And the newer and popular languages are infact slower than C. though speed is one of the lesser criterias. Most of the progress came from novel paradigms. Web, Internet, Cloud computing and Social networking are novel paradigms and did not involve progress in programming as such. Heck even facebook was written in PHP and not some extreme language. Though it did face scalability issues (same with twitter) but i believe money and better programmers (who came in much later) took care of that. Thus ideating capability trumped programming capability/ Even things like Map-Reduce, Column oriented database and Probablistic algorithms (E.g. bloom filters) came from hardcore Algorithms research, rather than some programming convention. Thus my final point is why programming skill is so overstressed? To point a recent example about how only 10% of programmers can "write code" (binary search) without debugging. Isnt it a bit hypocritical, considering your real successs lies in coming up with better algorithm or a novel feature rather than getting right first time???

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• Adding new elements into DOM using JavaScript (appendChild)

  - by KatieK

  I sometimes need to add elements (such as a new link and image) to an existing HTML page, but I only have access to a small portion of the page far from where I need to insert elements. I want to use DOM based JavaScript techniques, and I must avoid using document.write(). Thus far, I've been using something like this: // Create new image element var newImg = document.createElement("img"); newImg.src = "images/button.jpg"; newImg.height = "50"; newImg.width = "150"; newImg.alt = "Click Me"; // Create new link element var newLink = document.createElement("a"); newLink.href = "/dir/signup.html"; // Append new image into new link newLink.appendChild(newImg); // Append new link (with image) into its destination on the page document.getElementById("newLinkDestination").appendChild(newLink); Is there a more efficient way that I could use to accomplish the same thing? It all seems necessary, but I'd like to know if there's a better way I could be doing this. Thanks!

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• Read huge free text docs in one file for lucene indexing

  - by Jun

  I have heaps of free text news docs in one big file. The structure of each news doc is like: (Header line) Category, Doc1, Date (day, month, year) (body text) ... ... ... (Header line) Category, Doc2, Date (day, month, year) (body text) ... ... ... If I extract each doc from the big file, it costs too much time and not efficient. Therefore, I decide to read the file line by line and feed information to lucene the same time. I write c# code to index each doc to lucene like: Streamreader sr = new Streamreader(file); string line = ""; while((line = sr.ReadLine()) != null) { How can I tell this line is a doc header line from text line and get the metadata and all the text lines of a doc for lucene to index. Also, the text is read by OCR which can not give correct line-separating. Captions are mixed with content text iterate the process till the end of the file } with thanks

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• When to use a foreign key in MySQL

  - by Mel

  Is there official guidance or a threshold to indicate when it is best practice to use a foreign key in a MySQL database? Suppose you created a table for movies. One way to do it is to integrate the producer and director data into the same table. (movieID, movieName, directorName, producerName). However, suppose most directors and producers have worked on many movies. Would it be best to create two other tables for producers and directors, and use a foreign key in the movie table? When does it become best practice to do this? When many of the directors and producers are appearing several times in the column? Or is it best practice to employ a foreign key approach at the start? While it seems more efficient to use a foreign key, it also raises the complexity of the database. So when does the trade off between complexity and normalization become worth it? I'm not sure if there is a threshold or a certain number of cell repetitions that makes it more sensible to use a foreign key. I'm thinking about a database that will be used by hundreds of users, many concurrently. Many thanks!

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• model.matrix() with na.action=NULL?

  - by Vincent

  I have a formula and a data frame, and I want to extract the model.matrix(). However, I need the resulting matrix to include the NAs that were found in the original dataset. If I were to use model.frame() to do this, I would simply pass it na.action=NULL. However, the output I need is of the model.matrix() format. Specifically, I need only the right-hand side variables, I need the output to be a matrix (not a data frame), and I need factors to be converted to a series of dummy variables. I'm sure I could hack something together using loops or something, but I was wondering if anyone could suggest a cleaner and more efficient workaround. Thanks a lot for your time! And here's an example: dat <- data.frame(matrix(rnorm(20),5,4), gl(5,2)) dat[3,5] <- NA names(dat) <- c(letters[1:4], 'fact') ff <- a ~ b + fact # This omits the row with a missing observation on the factor model.matrix(ff, dat) # This keeps the NA, but it gives me a data frame and does not dichotomize the factor model.frame(ff, dat, na.action=NULL) Here is what I would like to obtain: (Intercept) b fact2 fact3 fact4 fact5 1 1 0.7266086 0 0 0 0 2 1 -0.6088697 0 0 0 0 3 NA 0.4643360 NA NA NA NA 4 1 -1.1666248 1 0 0 0 5 1 -0.7577394 0 1 0 0 6 1 0.7266086 0 1 0 0 7 1 -0.6088697 0 0 1 0 8 1 0.4643360 0 0 1 0 9 1 -1.1666248 0 0 0 1 10 1 -0.7577394 0 0 0 1

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• Fast serialization/deserialization of structs

  - by user256890

  I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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• Recursion - Ship Battle

  - by rgorrosini

  I'm trying to write a little ship battle game in java. It is 100% academic, I made it to practice recursion, so... I want to use it instead of iteration, even if it's simpler and more efficient in most some cases. Let's get down to business. These are the rules: Ships are 1, 2 or 3 cells wide and are placed horizontally only. Water is represented with 0, non-hit ship cells are 1, hit ship cells are 2 and sunken ships have all it's cells in 3. With those rules set, I'm using the following array for testing: int[][] board = new int[][] { {0, 1, 2, 0, 1, 0}, {0, 0, 1, 1, 1, 0}, {0, 3, 0, 0, 0, 0}, {0, 0, 2, 1, 2, 0}, {0, 0, 0, 1, 1, 1}, }; It works pretty good so far, and to make it more user-friendly I would like to add a couple of reports. these are the methods I need for them: Given the matrix, return the amount of ships in it. Same as a), but separating them by state (amount of non-hit ships, hit and sunken ones). I will need a hand with those reports, and I would like to get some ideas. Remember it must be done using recursion, I want to understand this, and the only way to go is practice! Thanks a lot for your time and patience :).

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• How to call shared_ptr<boost::signal> from a vector in a loop?

  - by BTR

  I've got a working callback system that uses boost::signal. I'm extending it into a more flexible and efficient callback manager which uses a vector of shared_ptr's to my signals. I've been able to successfully create and add callbacks to the list, but I'm unclear as to how to actually execute the signals. ... // Signal aliases typedef boost::signal<void (float *, int32_t)> Callback; typedef std::shared_ptr<Callback> CallbackRef; // The callback list std::vector<CallbackRef> mCallbacks; // Adds a callback to the list template<typename T> void addCallback(void (T::* callbackFunction)(float * data, int32_t size), T * callbackObject) { CallbackRef mCallback = CallbackRef(new Callback()); mCallback->connect(boost::function<void (float *, int32_t)>(boost::bind(callbackFunction, callbackObject, _1, _2))); mCallbacks.push_back(mCallback); } // Pass the float array and its size to the callbacks void execute(float * data, int32_t size) { // Iterate through the callback list for (vector<CallbackRef>::iterator i = mCallbacks.begin(); i != mCallbacks.end(); ++i) { // What do I do here? // (* i)(data, size); // <-- Dereferencing doesn't work } } ... All of this code works. I'm just not sure how to run the call from within a shared_ptr from with a vector. Any help would be neat-o. Thanks, in advance.

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• Accessing HTML DOM elements from javascript using `.childNodes`

  - by Martin

  I'm wondering about the .childNodes property, I have the code below, and for some reason I get 18 children, while 6 are HTMLInputElements as expected, and the rest are undefined. What is this about? Is there an efficient way to iterate over the input elements? <html> <head> <script> window.onload = function(e){ form = document.getElementById('myForm'); alert(form.childNodes.length); for(i=0; i<form.childNodes.length; i++){ alert(form[i]); } } </script> </head> <body> <form id='myForm' action="haha" method="post"> Name: <input type="text" id="fnameAdd" name="name" /><br /> Phone1: <input type="text" id="phone1Add" name="phone1" /><br /> Phone2: <input type="text" id="phone2Add" name="phone2" /><br /> E-Mail: <input type="text" id="emailAdd" name="email" /><br /> Address: <input type="text" id="addressAdd" name="address" /><br /> <input type="submit" value="Save" /> </body> </html>

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• Coding the R-ight way - avoiding the for loop

  - by mropa

  I am going through one of my .R files and by cleaning it up a little bit I am trying to get more familiar with writing the code the r-ight way. As a beginner, one of my favorite starting points is to get rid of the for() loops and try to transform the expression into a functional programming form. So here is the scenario: I am assembling a bunch of data.frames into a list for later usage. dataList <- list (dataA, dataB, dataC, dataD, dataE ) Now I like to take a look at each data.frame's column names and substitute certain character strings. Eg I like to substitute each "foo" and "bar" with "baz". At the moment I am getting the job done with a for() loop which looks a bit awkward. colnames(dataList[[1]]) [1] "foo" "code" "lp15" "bar" "lh15" colnames(dataList[[2]]) [1] "a" "code" "lp50" "ls50" "foo" matchVec <- c("foo", "bar") for (i in seq(dataList)) { for (j in seq(matchVec)) { colnames (dataList[[i]])[grep(pattern=matchVec[j], x=colnames (dataList[[i]]))] <- c("baz") } } Since I am working here with a list I thought about the lapply function. My attempts handling the job with the lapply function all seem to look alright but only at first sight. If I write f <- function(i, xList) { gsub(pattern=c("foo"), replacement=c("baz"), x=colnames(xList[[i]])) } lapply(seq(dataList), f, xList=dataList) the last line prints out almost what I am looking for. However, if i take another look at the actual names of the data.frames in dataList: lapply (dataList, colnames) I see that no changes have been made to the initial character strings. So how can I rewrite the for() loop and transform it into a functional programming form? And how do I substitute both strings, "foo" and "bar", in an efficient way? Since the gsub() function takes as its pattern argument only a character vector of length one.

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• Top n items in a List ( including duplicates )

  - by Krishnan

  Trying to find an efficient way to obtain the top N items in a very large list, possibly containing duplicates. I first tried sorting & slicing, which works. But this seems unnnecessary. You shouldn't need to sort a very large list if you just want the top 20 members. So I wrote a recursive routine which builds the top-n list. This also works, but is very much slower than the non-recursive one! Question: Which is my second routine (elite2) so much slower than elite, and how do I make it faster ? My code is attached below. Thanks. import scala.collection.SeqView import scala.math.min object X { def elite(s: SeqView[Int, List[Int]], k:Int):List[Int] = { s.sorted.reverse.force.slice(0,min(k,s.size)) } def elite2(s: SeqView[Int, List[Int]], k:Int, s2:List[Int]=Nil):List[Int] = { if( k == 0 || s.size == 0) s2.reverse else { val m = s.max val parts = s.force.partition(_==m) val whole = if( parts._1.size > 1) parts._1.tail:::parts._2 else parts._2 elite2( whole.view, k-1, m::s2 ) } } def main(args:Array[String]) = { val N = 1000000/3 val x = List(N to 1 by -1).flatten.map(x=>List(x,x,x)).flatten.view println(elite2(x,20)) println(elite(x,20)) } }

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• Velocity CTP: can we 'search' for objects?

  - by Stato Machino

  It appears that 'tags' allow us to associate a 'search term' with the objects placed into the Velocity cache space. However, these can only be queried within a 'region'. Further, regions somehow limit the locality of objects in the cache to a single server (or maybe something kinda like that). So this appears to make it hard to perform any operation for which the unique Id of the cached item is not persisted or continuously available to the application that stores and retrieves objects to and from the cache. In any case, I can't see an easy way to 'cleanse' the cache of objects or to find objects across the entire cache that may share some prefix, postfix or infix values in the cache key so that i can clear out the cache of object repeatedly created in unit tests, for example. And I am unsure about the consequences of regions being associated with single server cache locations. So I would appreciate any help with the following questions: What is the difference between a 'distributed cache' (called a 'partitioned' cache??) when using regions, and a 'local cache'? 1.a. In particular, are the region-oriented values in a distributed cache visible through a cache factory that is configured to 'see' the entire cache space? Are the operations of creating and removing 'regions' efficient enough that it would be reasonable to create a region and a group of tags for each bundle of objects that need to be cached? 2.a. Or does this just push the problem of scoping the 'search for objects' up the chain because the ability of the DataCache object to query down through regions and tags as limited as querying for the cache keys of objects themselves. Thanks, Stato

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• Database (MySQL) structuring: pros and cons of multiple tables

  - by Gideon

  I am collecting data and storing it MySQL, for: 75 variables 55 countries Each year I have, at this stage since I am building this tool created a single table, of variables / countries (storing 1 year worth of data). Next year (and for several years after that) a new set of data will be input for each country. There are therefore 3 variables in controlling data returned to a user reviewing all collected data. The general form of any query would be: Show me these specifics variables, for these specific countries, for these specific years. (Show me average age and weight, for USA and Canada, for 2012 and 2009, for example) My question is, it seems that I have two options for arranging this data: -Multiple tables where I create a table of country / variable for each year data is collected - Single table and simply add a column (field) for the year that data relates to. As far as I can tell I could make these database calls with either sructure, but is one more powerful / efficient / quicker, and why? Thanks for your consideration. It's a PDO / PHP interface if that is relevent.

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• PHP Arrays: Pop an array of single-element arrays into one array.

  - by Rob Drimmie

  Using a proprietary framework, I am frequently finding myself in the situation where I get a resultset from the database in the following format: array(5) { [0] => array(1) { ["id"] => int(241) } [1] => array(1) { ["id"] => int(2) } [2] => array(1) { ["id"] => int(81) } [3] => array(1) { ["id"] => int(560) } [4] => array(1) { ["id"] => int(10) } } I'd much rather have a single array of ids, such as: array(5) { [0] => int(241) [1] => int(2) [2] => int(81) [3] => int(560) [4] => int(10) } To get there, I frequently find myself writing: $justIds = array(); foreach( $allIds as $id ) { $justIds[] = $id["id"]; } Is there a more efficient way to do this?

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