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• log activity. intrusion detection. user event notification ( interraction ). messaging

  - by Julian Davchev

  Have three questions that I somehow find related so I put them in same place. Currently building relatively large LAMP system - making use of messaging(activeMQ) , memcache and other goodies. I wonder if there are best practices or nice tips and tricks on howto implement those. System is user aware - meaning all actions done can be bind to particular logged user. 1. How to log all actions/activities of users? So that stats/graphics might be extracted later for analysing. At best that will include all url calls, post data etc etc. Meaning tons of inserts. I am thinking sending messages to activeMQ and later cron dumping in DB and cron analysing might be good idea here. Since using Zend Framework I guess I may use some request plugin so I don't have to make the log() call all over the code. 2.How to log stuff so may be used for intrusion detection? I know most things might be done on http level using apache mods for example but there are also specific cases like (5 failed login attempts in a row (leads to captcha) etc etc..) This also would include tons of inserts. Here I guess direct usage of memcache might be best approach as data don't seem vital to be permanantly persisted. Not sure if cannot use data from point 1. 3.System will notify users of some events. Like need approval , something broke..whatever.Some events will need feedback(action) from user, others are just informational. Wonder if there is common solutions for needs like this. Example: Based on occuring event(s) user will be notifed (user inbox for example) what happend. There will be link or something to lead him to details of thingy that happend and take action accordingly. Those seem trivial at first look but problem I see if coding it directly is becoming really fast hard to maintain.

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• How do I retrieve twitter xml for Flash site via php properly

  - by daidai

  Am I using TwitterScript to retrieve Twitter data for inside a Flash site. Due to Twitter's crossdomain policy, I need to setup a php proxy... Firstly I made a simple one <?php $url = $_GET['url']; readfile($url); ?> but I then get this error URL file-access is disabled in the server configuration which is only resolved by getting my host to turn fopen() on, which I don't want to do. Then I found this <?php function get_content($url) { $ch = curl_init(); curl_setopt ($ch, CURLOPT_URL, $url); curl_setopt ($ch, CURLOPT_HEADER, 0); ob_start(); curl_exec ($ch); curl_close ($ch); $string = ob_get_contents(); ob_end_clean(); return $string; } #usage: $url = $_GET['url']; $content = get_content ($url); var_dump ($content); ?> which solves that problem but the data now is the correct XML but looks like: string(39950) "<?xml version="1.0" encoding="UTF-8"?> <statuses type="array"> <status> ... </statuses>" How do I get the XML data out of that string?

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• Flash browser game - HTTP + PHP vs Socket + Something else

  - by Maurycy Zarzycki

  I am developing a non-real time browser RPG game (think Kingdom of Loathing) which would be played from within a Flash app. At first I just wanted to make the communication with server using simply URLLoader to tell PHP what I am doing, and using $_SESSION to store data needed in-between request. I wonder if it wouldn't be better to base it on a socket connection, an app residing on a server written in Java or Python. The problem is I have never ever written such an app so I have no idea how much I'd have to "shift" my thoughts from simple responding do request (like PHP) to continuously working application. I won't hide I am also concerned about the memory and CPU usage of such Server app, when for example there would be hundreds of users connected. I've done some research. I have tried to do some research, but thanks to my nil knowledge on the sockets subject I haven't found anything helpful. So, considering the fact I don't need real time data exchange, will it be wise to develop the server side part as socket server, not in plain ol' PHP?

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• [PHP/MySQL] How to create text diff web app

  - by Adam Kiss

  Hello, idea I would like to create a little app for myself to store ideas (the thing is - I want it to do MY WAY) database I'm thinking going simple: id - unique id of revision in database text_id - identification number of text rev_id - number of revision flags - various purposes - expl. later title - self expl. desc - description text - self expl . flags - if I (i.e.) add flag rb;65, instead of storing whole text, I just said, that whenever I ask for latest revision, I go again in DB and check revision 65 Question: Is this setup the best? Is it better to store the diff, or whole text (i know, place is cheap...)? Does that revision flag make sense (wouldn't it be better to just copy text - more disk space, but less db and php processing. php I'm thinking, that I'll go with PEAR here. Although main point is to open-edit-save, possiblity to view revisions can't be that hard to program and can be life-saver in certain situations (good ideas got deleted, saving wrong version, etc...). However, I've never used PEAR in a long-time or full-project relationship, however, brief encounters in my previous experience left rather bad feeling - as I remember, it was too difficult to implement, slow and humongous to play with, so I don't know, if there's anything better. why? Although there are bazillions of various time/project/idea management tools, everything lacks something for me, whether it's sharing with users, syncing on more PCs, time-tracking, project management... And I believe, that this text diff webapp will be for internal use with various different tools later. So if you know any good and nice-UI-having project management app with support for text-heavy usage, just let me know, so I'll save my time for something better than redesigning the weel.

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• My method is too specific. How can I make it more generic?

  - by EricBoersma

  I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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• How to make a plot from summaryRprof?

  - by ThorDivDev

  This is a question for an university assignment. I was given three algorithms to calculate the GCD that I already did. My problem is getting the Rprof results to a plot so I can compare them side by side. From what little understanding I have about Rprof, summaryRprof and plot is that Rprof is used like this: Rprof() #To start #functions here Rprof(NULL) #TO end summaryRprof() # to print results I understand that plot has many different types of inputs, x and y values and something called a data frame which I assume is a fancy word for table. and to draw different lines and things I need to use this: http://www.harding.edu/fmccown/r/ what I cant figure out is how to get the summaryRprof results to the plot() function. > Rprof(filename="RProfOut2.out", interval=0.0001) > gcdBruteForce(10000, 33) [1] 1 > gcdEuclid(10000, 33) [1] 1 > gcdPrimeFact(10000, 33) [1] 1 > Rprof(NULL) > summaryRprof() ?????plot???? I have been reading on stack overflow that and other sites that I can also try to use profr and proftools although I am not very clear on the usage. The only graph I have been able to make is one using plot(system.time(gcdFunction(10,100))) As always any help is appreciated.

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• C++ RPC library suggestions

  - by Oxsnarder

  I'm looking for suggestions regarding RPC libraries implemented in C++, for C++ developers. Some requirements constraints: Should work on both linux/unix and win32 systems Be able to execute free function and class methods Hopefully written in modern C++ not 90's/java-esque C++ Be able to function over networks and hetrogenous architectures Not too slow or inefficient Hopefully provide interfaces for TR1 style std::function's et al. My example usage is to invoke the free function foo on a remote machine. ---snip--- // foo translation unit int foo(int i, int j) { return i + j; } ---snip--- ---snip--- // client side main int main() { //register foo on client and server //setup necassary connections and states int result; if (RPCmechanism.invoke("foo",4,9,result)) std::cout << "foo(4,9) = " result << std::endl; else std::cout << "failed to invoke foo(4,9)!" << std::endl; return 0; } ---snip--- Something that can achieve the above or similar would be great.

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• Multithreading for loop while maintaining order

  - by David

  I started messing around with multithreading for a CPU intensive batch process I'm running. Essentially I'm trying to condense multiple single page tiffs into single PDF documents. This works fine with a foreach loop or standard iteration but can be very slow for several 100 page documents. I tried the following based on a some examples I found to use multithreading and it has significant performance improvements however it obliterates the page order instead of 1,2,3,4 it will be 1,3,4,2,6,5 on what thread completes first. My question is how would I utilize this technique while maintaining the page order and if I can will it negate the performance benefit of the multithreading? Thank you in advance. PdfDocument doc = new PdfDocument(); string mail = textBox1.Text; string[] split = mail.Split(new string[] { Environment.NewLine }, StringSplitOptions.None); int counter = split.Count(); // Source must be array or IList. var source = Enumerable.Range(0, 100000).ToArray(); // Partition the entire source array. var rangePartitioner = Partitioner.Create(0, counter); double[] results = new double[counter]; // Loop over the partitions in parallel. Parallel.ForEach(rangePartitioner, (range, loopState) => { // Loop over each range element without a delegate invocation. for (int i = range.Item1; i < range.Item2; i++) { f_prime = split[i].Replace(" " , ""); PdfPage page = doc.AddPage(); XGraphics gfx = XGraphics.FromPdfPage(page); XImage image = XImage.FromFile(f_prime); double x = 0; gfx.DrawImage(image, x, 0); } });

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• Whether to put method code in a VB.Net data storage class, or put it in a separate class?

  - by Alan K

  TLDR summary: (a) Should I include (lengthy) method code in classes which may spawn multiple objects at runtime, (b) does doing so cause memory usage bloat, (c) if so should I "outsource" the code to a class that is loaded only once and have the class methods call that, or alternatively (d) does the code get loaded only once with the object definition anyway and I'm worrying about nothing? ........ I don't know whether there's a good answer to this but if there is I haven't found it yet by searching in the usual places. In my VB.Net (2010 if it matters) WinForms project I have about a dozen or so class objects in an object model. Some of these are pretty simple and do little more than act as data storage repositories. The ones further up the object model, however, have an increasing number of methods. There can be a significant number of higher level objects in use though the exact number will be runtime dependent so I can't be more precise than that. As I was writing the method code for one of the top level ones I noticed that it was starting to get quite lengthy. Memory optimisation is something of a lost art given how much memory the average PC has these days but I don't want to make my application a resource hog. So my questions for anyone who knows .Net way better than I do (of which there will be many) are: Is the code loaded into memory with each instance of the class that's created? Alternatively is it loaded only once with the definition of the class, and all derived objects just refer to that definition? (I'm not really sure how that could be possible given that, for example, event handlers can be assigned dynamically, but no harm asking.) If the answer to the first one is yes, would it be more efficient to write the code in a "utility" object which is loaded only once and called from the real class' methods? Any thoughts appreciated.

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• Porting Perl to C++ `print "\x{2501}" x 12;`

  - by jippie

  I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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• How do software events work internally?

  - by Duddle

  Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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• PHP, MySQL, Memcache / Ajax Scaling Problem

  - by Jeff Andersen

  I'm building a ajax tic tac toe game in PHP/MySQL. The premise of the game is to be able to share a url like mygame.com/123 with your friends and you play multiple simultaneous games. The way I have it set up is that a file (reload.php) is being called every 3 seconds while the user is viewing their game board space. This reload.php builds their game boards and the output (html) replaces their current game board (thus showing games in which it is their turn) Initially I built it entirely with PHP/MySQL and had zero caching. A friend gave me a suggestion to try doing all of the temporary/quick read information through memcache (storing moves, and ID matchups) and then building the game boards from this information. My issue is that, both solutions encounter a wall when there is roughly 30-40 active users with roughly 40-50 games running. It is running on a VPS from VPS.net with 2 nodes. (Dedicated CPU: 1.2GHz, RAM: 752MB) Each call to reload.php peforms 3 selects and 2 insert queries. The size of the data being pulled is negligible. The same actions happen on index.php to build the boards for the initial visit. Now that the backstory is done, my question is: Would there be a bottleneck in that each user is polling the same file every 3 seconds to rebuild their gameboards, and that all users are sitting on index.php from which the AJAX calls are made within the HTML. If so, is it possible to spread the users' calls out over a set of files designated to building the game boards (eg. reload1.php 2, 3 etc) and direct users to the appropriate file. Would this relieve the pressure? A long winded explanation; however, I didn't have anywhere else to ask. Thanks very much for any insight.

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• Mercurial repository narrow clone?

  - by Berry Langerak

  Hi. I'm currently in the process of moving from Subversion to Mercurial, and I have to say I don't regret that decision. However, when trying to convert my project, I ran into a problem of Mercurial, which I can't seem to get fixed. I have two distinct projects: one is a framework, and the other is an application that relies on that framework. Here's what the repositories look like: The Framework repository: docs/ deploy/ lib/ tests/ The Application repository: application/ config/ lib/ tests/ www/ What I'd like is for the application's lib directory to contain a copy of the frameworks' lib/ directory. I used to do this using svn:externals. Now, I am aware that Mercurial supports the concept of subrepositories, but that doesn't seem like the "correct" solution, as it doesn't actually pull in the lib/ directory like I wanted, as you'll still have to pull and push changes manually. That, plus once you clone the framework repository, you'll get all of it, not just the lib/ directory. I only need the lib/ directory, not the tests, or the docs. Now, I thought up two different solutions to this problem, but I wonder which is the best. The first solution would be to clone the framework in a different directory altogether and create symlink in the application's lib/ directory which points to the framework's lib/ directory. Putting the symlink in .hgignore should make sure all is well, I think? That means that you could edit the frameworks code, and commit that, and you could edit the application's code and commit that, too. The other option is to have multiple repositories. The framework gets pulled as a whole, which means you'll get the docs/, deploy/, test/ etc. directories, which are not needed for usage of the framework. I thought maybe creating a repository purely for the library might be a solution, although I sincerely doubt it, as the Unit Tests are very dependant upon the library itself. Does anyone know a decent solution for this problem?

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• Hadoop File Read

  - by user3684584

  Hadoop Distributed Cache Wordcount example in hadoop 2.2.0. Copied file into hdfs filesystem to be used inside setup of mapper class. protected void setup(Context context) throws IOException,InterruptedException { Path[] uris = DistributedCache.getLocalCacheFiles(context.getConfiguration()); cacheData=new HashMap(); for(Path urifile: uris) { try { BufferedReader readBuffer1 = new BufferedReader(new FileReader(urifile.toString())); String line; while ((line=readBuffer1.readLine())!=null) { System.out.println("**************"+line); cacheData.put(line,line); } readBuffer1.close(); } catch (Exception e) { System.out.println(e.toString()); } } } Inside Driver Main class Configuration conf = new Configuration(); String[] otherArgs = new GenericOptionsParser(conf,args).getRemainingArgs(); if (otherArgs.length != 3) { System.err.println("Usage: wordcount <in> <out>"); System.exit(2); } Job job = new Job(conf, "word_count"); job.setJarByClass(WordCount.class); job.setMapperClass(Map.class); job.setReducerClass(Reduce.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); Path outputpath=new Path(otherArgs[1]); outputpath.getFileSystem(conf).delete(outputpath,true); FileOutputFormat.setOutputPath(job,outputpath); System.out.println("CachePath****************"+otherArgs[2]); DistributedCache.addCacheFile(new URI(otherArgs[2]),job.getConfiguration()); System.exit(job.waitForCompletion(true) ? 0 : 1); But getting exception java.io.FileNotFoundException: file:/home/user12/tmp/mapred/local/1408960542382/cache (No such file or directory) So Cache functionality not working properly. Any Idea ?

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• lua metatable __lt __le __eq forced boolean conversion of return value

  - by chris g.

  Overloading __eq, __lt, and __le in a metatable always converts the returning value to a boolean. Is there a way to access the actual return value? This would be used in the following little lua script to create an expression tree for an argument usage: print(_.a + _.b - _.c * _.d + _.a) -> prints "(((a+b)-(c*d))+a)" which is perfectly what I would like to have but it doesn't work for print(_.a == _.b) since the return value gets converted to a boolean ps: print should be replaced later with a function processing the expression tree -- snip from lua script -- function binop(op1,op2, event) if op1[event] then return op1[event](op1, op2) end if op2[event] then return op2[event](op1, op2) end return nil end function eq(op1, op2)return binop(op1,op2, "eq") end ... function div(op1, op2)return binop(op1,op2, "div") end function exprObj(tostr) expr = { eq = binExpr("=="), lt = binExpr("<"), le = binExpr("<="), add = binExpr("+"), sub=binExpr("-"), mul = binExpr("*"), div= binExpr("/") } setmetatable(expr, { __eq = eq, __lt = lt, __le = le, __add = add, __sub = sub, __mul = mul, __div = div, __tostring = tostr }) return expr end function binExpr(exprType) function binExprBind(lhs, rhs) return exprObj(function(op) return "(" .. tostring(lhs) .. exprType .. tostring(rhs) .. ")" end) end return binExprBind end function varExpr(obj, name) return exprObj(function() return name end) end _ = {} setmetatable(_, { __index = varExpr }) -- snap -- Modifing the lua vm IS an option, however it would be nice if I could use an official release

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• How can flash call jquery function in its event

  - by user2955639

  I want jquery to do something during some of the events when an audio is playing. So I'm coding a function like this <script> $.fn.playMedia = function(options){ var opts = $.extend({}, { swfSrc: '' timeUpdated: function(currentTime){}, startPlay: function(){}, endPlay: function(){} }, options); return $(this).each(function(){ // call flash to play the media whose src is opts.swfSrc // Is it possible that flash can call the js functions(opts.timeUpdate, opts.startPlay and opts.endPlay) at each time of the event is triggered? }); }}; </script> // Usage <div id="player"></div> <script> $('#player').playMedia({ swfSrc: '/path/song.mp3', timeUpdated: function(currentTime){ comsole.log(currentTime); } }); </script> I'm a totally layman of flash, I just guess this works. Hope someone could tell me how to make up a swf file for this jquery function. Or is there any existing jquery plugin which does this thing but can re-design apperance flexibly. Thank you very much!

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• Minimizing server load in case of many XMLHttpRequest calls

  - by user1888975

  I am making a website where users are to like some articles. Whenever the like button is clicked I am sending a XMLHttpRequest to the server to run a file called like_clicked.php along with the get data of article id and user id. This file takes article id and user id and updates the sql database and also adds a node in an xml file related to the user. This is the first time I am doing something for mass usage. I am worried about the server load when too many users call the like_clicked.php file. Please help me, if this method is ok. I am also thinking of an alternative in case the above method fails. I am thinking of making many like_clicked files (namely like_clicked1.php, like_clicked2.php ... ) to minimize load on a single i-node. Is there a method to detect that it is better to call the next like_clicked file. Here we would need to detect how many calls per unit time are coming for the particular file. How do we handle this? Thanks in advance.

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• C# Linq Select Problem in Method Chain.

  - by Gnought

  Note that the _src inherit IQueryable<U> and V inherit new(); I wrote the following statement, there is no syntax error. IQueryable<V> a = from s in _src where (s.Right - 1 == s.Left) select new V(); But if i re-wrote it as follows, the Visual Studio editor complains an error in the "Select" IQueryable<V> d = _src.Where(s => s.Right - 1 == s.Left).Select(s=> new V()); The Error is: The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly. Candidates are: System.Collections.Generic.IEnumerable<V> Select<U,V>(this System.Collections.Generic.IEnumerable<U>, System.Func<U,V>) (in class Enumerable) System.Linq.IQueryable<V> Select<U,V>(this System.Linq.IQueryable<U>, System.Linq.Expressions.Expression<System.Func<U,V>>) (in class Queryable) Could anyone explain this phenomenon, and what the solution is to fix the error?

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• Method returns an IDisposable - Should I dispose of the result, even if it's not assigned to anythin

  - by mjd79

  This seems like a fairly straightforward question, but I couldn't find this particular use-case after some searching around. Suppose I have a simple method that, say, determines if a file is opened by some process. I can do this (not 100% correctly, but fairly well) with this: public bool IsOpen(string fileName) { try { File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None); } catch { // if an exception is thrown, the file must be opened by some other process return true; } } (obviously this isn't the best or even correct way to determine this - File.Open throws a number of different exceptions, all with different meanings, but it works for this example) Now the File.Open call returns a FileStream, and FileStream implements IDisposable. Normally we'd want to wrap the usage of any FileStream instantiations in a using block to make sure they're disposed of properly. But what happens in the case where we don't actually assign the return value to anything? Is it still necessary to dispose of the FileStream, like so: try { using (File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); { /* nop */ } } catch { return true; } Should I create a FileStream instance and dispose of that? try { using (FileStream fs = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); } ... Or are these totally unnecessary? Can we simply call File.Open and not assign it to anything (first code example), and let the GC dispose of it right away?

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• Best approach to cache Counts from SQL tables ?

  - by pixel3cs

  I would like to develop a Forum from scratch, with special needs and customization. I would like to prepare my forum for intensive usage and wondering how to cache things like User posts count and User replies count. Having only three tables, tblForum, tblForumTopics, tblForumReplies, what is the best approach of cache the User topics and replies counts ? Think at a simple scenario: user press a link and open the Replies.aspx?id=x&page=y page, and start reading replies. On the HTTP Request, the server will run an SQL command wich will fetch all replies for that page, also "inner joining with tblForumReplies to find out the number of User replies for each user that replied." select tblForumReplies.*, tblFR.TotalReplies from tblForumReplies inner join ( select IdRepliedBy, count(*) as TotalReplies from tblForumReplies group by IdRepliedBy ) as tblFR on tblFR.IdRepliedBy = tblForumReplies.IdRepliedBy Unfortunately this approach is very cpu intensive, and I would like to see your ideas of how to cache things like table Counts. If counting replies for each user on insert/delete, and store it in a separate field, how to syncronize with manual data changing. Suppose I will manually delete Replies from SQL.

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• I need to make a multithreading program (python)

  - by Andreawu98

  import multiprocessing import time from itertools import product out_file = open("test.txt", 'w') P = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p','q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',] N = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] M = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'] c = int(input("Insert the number of digits you want: ")) n = int(input("If you need number press 1: ")) m = int(input("If you need upper letters press 1: ")) i = [] if n == 1: P = P + N if m == 1: P = P + M then = time.time() def worker(): for i in product(P, repeat=c): #check every possibilities k = '' for z in range(0, c): # k = k + str(i[z]) # print each possibility in a txt without parentesis or comma out_file.write( k + '\n') # out_file.close() now = time.time() diff = str(now - then) # To see how long does it take print(diff) worker() time.sleep(10) # just to check console The code check every single possibility and print it out in a test.txt file. It works but I really can't understand how can I speed it up. I saw it use 1 core out of my quad core CPU so I thought Multi-threading might work even though I don't know how. Please help me. Sorry for my English, I am from Italy.

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• Are programming languages and methods ineffective? (assembler and C knowledge needed)

  - by b-gen-jack-o-neill

  Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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• Is the 'var' keyword bad? Or am I just old school?

  - by WaggingSiberian

  Recently I overheard junior developer ask "why do you use 'var' so much?". The mid-level developer responded "I use VAR all the time. I love it! I don't have to figure out the type." I didn't have the time or energy to get into a religious war and hey, I'm still the new guy here :-) I understand var has its place. LINQ comes to mind. But I have also always been told the use of var represents lazy programming and I should just use the correct type to begin with. If it's an int, define it as an int, not a var. When reviewing code, seeing the type makes it easier to follow. My opinion is, it's just lazy but there are exceptions. Var also reminds me of the VB/VBA variant type. It also had its place. I recall (from many years ago) its usage being less-than-desirable type and it was rather resource hungry. Am I just being stuck in my ways? Should we start using var all the time as my co-worker does?

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• How to provide warnings during validation in ASP.NET MVC?

  - by Alex

  Sometimes user input is not strictly invalid but can be considered problematic. For example: A user enters a long sentence in a single-line Name field. He probably should have used the Description field instead. A user enters a Name that is very similar to that of an existing entity. Perhaps he's inputting the same entity but didn't realize it already exists, or some concurrent user has just entered it. Some of these can easily be checked client-side, some require server-side checks. What's the best way, perhaps something similar to DataAnnotations validation, to provide warnings to the user in such cases? The key here is that the user has to be able to override the warning and still submit the form (or re-submit the form, depending on the implementation). The most viable solution that comes to mind is to create some attribute, similar to a CustomValidationAttribute, that may make an AJAX call and would display some warning text but doesn't affect the ModelState. The intended usage is this: [WarningOnFieldLength(MaxLength = 150)] [WarningOnPossibleDuplicate()] public string Name { get; set; } In the view: @Html.EditorFor(model => model.Name) @Html.WarningMessageFor(model => model.Name) @Html.ValidationMessageFor(model => model.Name) So, any ideas?

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• Aliasing `T*` with `char*` is allowed. Is it also allowed the other way around?

  - by StackedCrooked

  Note: This question has been renamed and reduced to make it more focused and readable. Most of the comments refer to the old text. According to the standard objects of different type may not share the same memory location. So this would not be legal: int i = 0; short * s = reinterpret_cast<short*>(&i); // BAD! The standard however allows an exception to this rule: any object may be accessed through a pointer to char or unsigned char: int i = 0; char * c = reinterpret_cast<char*>(&i); // OK However, it is not clear to me if this is also allowed the other way around. For example: char * c = read_socket(...); unsigned * u = reinterpret_cast<unsigned*>(c); // huh? Summary of the answers The answer is NO for two reasons: You an only access an existing object as char*. There is no object in my sample code, only a byte buffer. The pointer address may not have the right alignment for the target object. In that case dereferencing it would result in undefined behavior. On the Intel and AMD platforms it will result performance overhead. On ARM it will trigger a CPU trap and your program will be terminated! This is a simplified explanation. For more detailed information see answers by @Luc Danton, @Cheers and hth. - Alf and @David Rodríguez.

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