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• High memory usage for dummies

  - by zaf

  I've just restarted my firefox web browser again because it started stuttering and slowing down. This happens every other day due to (my understanding) of excessive memory usage. I've noticed it takes 40M when it starts and then, by the time I notice slow down, it goes to 1G and my machine has nothing more to offer unless I close other applications. I'm trying to understand the technical reasons behind why its such a difficult problem to sol ve. Mozilla have a page about high memory usage: http://support.mozilla.com/en-US/kb/High+memory+usage But I'm looking for a slightly more in depth and satisfying explanation. Not super technical but enough to give the issue more respect and please the crowd here. Some questions I'm already pondering (they could be silly so take it easy): When I close all tabs, why doesn't the memory usage go all the way down? Why is there no limits on extensions/themes/plugins memory usage? Why does the memory usage increase if it's left open for long periods of time? Why are memory leaks so difficult to find and fix? App and language agnostic answers also much appreciated.

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• How to access elements in a complex list?

  - by Martin

  Hi, it's me and the lists again. I have a nice list, which looks like this: tmp = NULL t = NULL tmp$resultitem$count = "1057230" tmp$resultitem$status = "Ok" tmp$resultitem$menu = "PubMed" tmp$resultitem$dbname = "pubmed" t$resultitem$count = "305215" t$resultitem$status = "Ok" t$resultitem$menu = "PMC" t$resultitem$dbname = "pmc" tmp = c(tmp, t) t = NULL t$resultitem$count = "1" t$resultitem$status = "Ok" t$resultitem$menu = "Journals" t$resultitem$dbname = "journals" tmp = c(tmp, t) Which produces: str(tmp) List of 3 $ resultitem:List of 4 ..$ count : chr "1057230" ..$ status: chr "Ok" ..$ menu : chr "PubMed" ..$ dbname: chr "pubmed" $ resultitem:List of 4 ..$ count : chr "305215" ..$ status: chr "Ok" ..$ menu : chr "PMC" ..$ dbname: chr "pmc" $ resultitem:List of 4 ..$ count : chr "1" ..$ status: chr "Ok" ..$ menu : chr "Journals" ..$ dbname: chr "journals" Now I want to search through the elements of each "resultitem". I want to know the "dbname" for every database, that has less then 10 "count" (example). In this case it is very easy, as this list only has 3 elements, but the real list is a little bit longer. This could be simply done with a for loop. But is there a way to do this with some other function of R (like rapply)? My problem with those apply functions is, that they only look at one element. If I do a grep to get all "dbname" elements, I can not get the count of each element. rapply(tmp, function(x) paste("Content: ", x))[grep("dbname", names(rapply(tmp, c)))] Does someone has a better idea than a for loop? Thanx, Martin

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• Project management: Implementing custom errors in VS compilation process

  - by David Lively

  Like many architects, I've developed coding standards through years of experience to which I expect my developers to adhere. This is especially a problem with the crowd that believes that three or four years of experience makes you a senior-level developer.Approaching this as a training and code review issue has generated limited success. So, I was thinking that it would be great to be able to add custom compile-time errors to the build process to more strictly enforce this and other guidelines. For instance, we use stored procedures for ALL database access, which provides procedure-level security, db encapsulation (table structure is hidden from the app), and other benefits. (Note: I am not interested in starting a debate about this.) Some developers prefer inline SQL or parametrized queries, and that's fine - on their own time and own projects. I'd like a way to add a compilation check that finds, say, anything that looks like string sql = "insert into some_table (col1,col2) values (@col1, @col2);" and generates an error or, in certain circumstances, a warning, with a message like Inline SQL and parametrized queries are not permitted. Or, if they use the var keyword var x = new MyClass(); Variable definitions must be explicitly typed. Do Visual Studio and MSBuild provide a way to add this functionality? I'm thinking that I could use a regular expression to find unacceptable code and generate the correct error, but I'm not sure what, from a performance standpoint, is the best way to to integrate this into the build process. We could add a pre- or post-build step to run a custom EXE, but how can I return line- and file-specifc errors? Also, I'd like this to run after compilation of each file, rather than post-link. Is a regex the best way to perform this type of pattern matching, or should I go crazy and run the code through a C# parser, which would allow node-level validation via the parse tree? I'd appreciate suggestions and tales of prior experience.

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• Is there a faster way to parse through a large file with regex quickly?

  - by Ray Eatmon

  Problem: Very very, large file I need to parse line by line to get 3 values from each line. Everything works but it takes a long time to parse through the whole file. Is it possible to do this within seconds? Typical time its taking is between 1 minute and 2 minutes. Example file size is 148,208KB I am using regex to parse through every line: Here is my c# code: private static void ReadTheLines(int max, Responder rp, string inputFile) { List<int> rate = new List<int>(); double counter = 1; try { using (var sr = new StreamReader(inputFile, Encoding.UTF8, true, 1024)) { string line; Console.WriteLine("Reading...."); while ((line = sr.ReadLine()) != null) { if (counter <= max) { counter++; rate = rp.GetRateLine(line); } else if(max == 0) { counter++; rate = rp.GetRateLine(line); } } rp.GetRate(rate); Console.ReadLine(); } } catch (Exception e) { Console.WriteLine("The file could not be read:"); Console.WriteLine(e.Message); } } Here is my regex: public List<int> GetRateLine(string justALine) { const string reg = @"^\d{1,}.+\[(.*)\s[\-]\d{1,}].+GET.*HTTP.*\d{3}[\s](\d{1,})[\s](\d{1,})$"; Match match = Regex.Match(justALine, reg, RegexOptions.IgnoreCase); // Here we check the Match instance. if (match.Success) { // Finally, we get the Group value and display it. string theRate = match.Groups[3].Value; Ratestorage.Add(Convert.ToInt32(theRate)); } else { Ratestorage.Add(0); } return Ratestorage; } Here is an example line to parse, usually around 200,000 lines: 10.10.10.10 - - [27/Nov/2002:16:46:20 -0500] "GET /solr/ HTTP/1.1" 200 4926 789

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• Moving UIScrollView in App

  - by jsetting32

  Currently, I am attempting to create the same effect as Yahoo! Weather's App where the vital day information is at the bottom of the page on the top of a UIScrollView, that's contained by a UIView. I am having a hard time thinking about how this is going to happen or how I should implement this. If the user taps on the top of the UIScrollView which is located near the bottom of the laoded UIView, and starts to scroll up (/), the UIScrollView's frame should be moved to the TOP of the current UIView's frame. So the UIScrollView's y-value should change to UIView's (self.view.frame.origin.y) if the user starts scrolling UP on the UIScrollView which is located on the UIView's y-pixel ~280. Here's what the UIViewController should look like in the beginning of loading the ViewController... Then once the user slides his finger from the bottom to the top of the screen... this should happen........ And when the user scrolls to the top of the UIScrollView with all the content within it... the view should go back to the start picture shown... How is this done? I was thinking several UIGestureRecognizer's and Instantiating the UIscrollview at the lower part of the UIView... _weatherView = [[UIScrollView alloc] initWithFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y + 250, self.view.bounds.size.width, self.view.bounds.size.height - 44)]; _weatherView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 4); _weatherView.backgroundColor = [UIColor clearColor]; [self.view addSubview:_weatherView]; The adding some UIGestureRecognizer delegate method.... But anyone have any ideas on the UIGestureRecognizer delegate method? And how it should be implemented? I can write the psuedo-code but I am having problems finding the delegate methods :P Thank you!!! ---- Break Time.... :)

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• node.js beginner tutorials?

  - by TreyK

  Hey all, I'm working on creating my first real node.js http server, and I'm sort of drowning in it. As a good teacher of mine always said, "I'll just shove you in the water for now, and then I'll show you how to swim." Fortunately, she wasn't a swimming instructor, but it's a good analogy nonetheless. I feel like I've jumped into node.js and I've only found a ping pong ball to help, that is to say, most of the tutorials I've read stop shortly after the "Hello World" example and I've mostly been trying to make sense of copied and pasted code (or they assume I have knowledge of lower level HTTP and webserver concepts that have been done for me as an Apache/PHP developer). I have experience in both client-side Javascript and PHP, but node seems to be a beast all of its own. I don't quite have the low-level knowledge that seems necessary for creating a node server, and connect, which seems to be a nice module for simplifying things, seems quite sparsely explained, even in the docs on its Git. Where could I find some tutorials to help me in this situation? TL;DR - Are there any tutorials for node.js that go beyond "Hello World" but don't require much low-level knowledge? Or any tutorials that explain lower-level HTTP and webserver concepts that I would need to effectively create a node HTTP server? Thanks for any help. -Trey

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• php import to mysql hosted on godaddy

  - by julio

  Yeah, I know! It's not my choice. I am doing a large data import using a PHP script into a mysql DB hosted on godaddy. It seems their mysql connection gets killed every few hours regardless of what work it's doing. Their tech support is useless, and I've exhausted myself writing attempted workarounds. Right now, I'm trying to do a mysql_ping every few minutes, and if the ping returns false, I attempt to open up a new db connection. My script (which takes many hours to complete), keeps failing with the very unhelpful message of "mysql server has gone away". I understand mysql trying to close a connection that's been open too long, but the connection is not idle-- it's busy basically the whole time, and with the pings I've written in, it should not be idle longer than 5 minutes at most at any time. (These same scripts work with no errors on Amazon AWS servers, my local servers, etc.) Any help most appreciated! I'm about to give up.

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• Linq is returning too many results when joined

  - by KallDrexx

  In my schema I have two database tables. relationships and relationship_memberships. I am attempting to retrieve all the entries from the relationship table that have a specific member in it, thus having to join it with the relationship_memberships table. I have the following method in my business object: public IList<DBMappings.relationships> GetRelationshipsByObjectId(int objId) { var results = from r in _context.Repository<DBMappings.relationships>() join m in _context.Repository<DBMappings.relationship_memberships>() on r.rel_id equals m.rel_id where m.obj_id == objId select r; return results.ToList<DBMappings.relationships>(); } _Context is my generic repository using code based on the code outlined here. The problem is I have 3 records in the relationships table, and 3 records in the memberships table, each membership tied to a different relationship. 2 membership records have an obj_id value of 2 and the other is 3. I am trying to retrieve a list of all relationships related to object #2. When this linq runs, _context.Repository<DBMappings.relationships>() returns the correct 3 records and _context.Repository<DBMappings.relationship_memberships>() returns 3 records. However, when the results.ToList() executes, the resulting list has 2 issues: 1) The resulting list contains 6 records, all of type DBMappings.relationships(). Upon further inspection there are 2 for each real relationship record, both are an exact copy of each other. 2) All relationships are returned, even if m.obj_id == 3, even though objId variable is correctly passed in as 2. Can anyone see what's going on because I've spent 2 days looking at this code and I am unable to understand what is wrong. I have joins in other linq queries that seem to be working great, and my unit tests show that they are still working, so I must be doing something wrong with this. It seems like I need an extra pair of eyes on this one :)

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• Attention JavaScript gurus: Need a hand with setInterval()

  - by alex

  I am trying to make a non interactive display for a real estate shop window. It's been a while since I've played with setInterval(). The first time my script steps through, it is fine. But when it tries to get the next property via getNextProperty(), it starts to go haywire. If you have Firebug, or an equivalent output of console.log(), you'll see it is calling things it shouldn't! Now there is a fair bit of JavaScript, so I'll feel better linking to it than posting it all. Store Display Offending JavaScript It is worth mentioning all my DOM/AJAX is done with jQuery. I've tried as best to make sure clearInterval() is working, and it seems to not run any code below it. The setInterval() is used to preload the next image, and then display it in the gallery. When the interval detects we are at the last image ((nextListItem.length === 0)), it is meant to clear that interval and start over with a new property. It has been driving me nuts for a while now, so anyone able to help me? It is probably something really obvious! Many thanks!

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• Is the following C code safe?

  - by lali

  #include<cstdio> #include<stdlib.h> int main() { char* ptr=NULL; printf("%s",ptr); return 0; } It prints (null) as output. The above is a sample code. In real code i get char* as a return of a function and i wish to print the character string for logging. However, NULL is also a valid return value of that function and so i am wondering if a null check is required before printing the character string? char* ptr=someFuncion(); // do i need the following if statement? if(ptr!=NULL) { printf("%s",ptr); } I just want to be sure that the output would be same i.e if ptr=NULL then output should be (null) on all platforms and compilers and the above code(without if statement) would not crash on any C standard compatible platform. In short, is the above code(without the if statement) standard compatible? Thanks for your help and patience :) Regards lali

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• Getting a handle on GIS math, where do I start?

  - by Joshua

  I am in charge of a program that is used to create a set of nodes and paths for consumption by an autonomous ground vehicle. The program keeps track of the locations of all items in its map by indicating the item's position as being x meters north and y meters east of an origin point of 0,0. In the real world, the vehicle knows the location of the origin's lat and long, as it is determined by a dgps system and is accurate down to a couple centimeters. My program is ignorant of any lat long coordinates. It is one of my goals to modify the program to keep track of lat long coords of items in addition to an origin point and items' x,y position in relation to that origin. At first blush, it seems that I am going to modify the program to allow the lat long coords of the origin to be passed in, and after that I desire that the program will automatically calculate the lat long of every item currently in a map. From what I've researched so far, I believe that I will need to figure out the math behind converting to lat long coords from a UTM like projection where I specify the origin points and meridians etc as opposed to whatever is defined already for UTM. I've come to ask of you GIS programmers, am I on the right track? It seems to me like there is so much to wrap ones head around, and I'm not sure if the answer isn't something as simple as, "oh yea theres a conversion from meters to lat long, here" Currently, due to the nature of DGPS, the system really doesn't need to care about locations more than oh, what... 40 km? radius away from the origin. Given this, and the fact that I need to make sure that the error on my coordinates is not greater than .5 meters, do I need anything more complex than a simple lat/long to meters conversion constant? I'm knee deep in materials here. I could use some pointers about what concepts to research. Thanks much!

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• Rails wont install at create Makefile stage

  - by mattc

  I am getting this error after running sudo gem install rails /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb creating Makefile make xcrun cc -I. - I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I. -DJSON_GENERATOR -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common -arch i386 -arch x86_64 -g -O3 -pipe -fno-common -DENABLE_DTRACE -fno-common -pipe -fno-common -c generator.c xcrun: Error: failed to exec real xcrun. (No such file or directory) cc -arch i386 -arch x86_64 -pipe -bundle -undefined dynamic_lookup -o generator.bundle generator.o -L. -L/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib -L. -arch i386 -arch x86_64 -lruby -lpthread -ldl -lobjc i686-apple-darwin11-llvm-gcc-4.2: generator.o: No such file or directory i686-apple-darwin11-llvm-gcc-4.2: generator.o: No such file or directory lipo: can't figure out the architecture type of: /var/tmp//ccHCNNwM.out make: *** [generator.bundle] Error 1 I have Homebrew installed, Xcode 4.4 with command line tools installed, Osx 10.6.2 I run gem env and get this but not sure what I'm looking for: RubyGems Environment: - RUBYGEMS VERSION: 1.8.24 - RUBY VERSION: 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0] - INSTALLATION DIRECTORY: /Library/Ruby/Gems/1.8 - RUBY EXECUTABLE: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby - EXECUTABLE DIRECTORY: /usr/bin - RUBYGEMS PLATFORMS: - ruby - universal-darwin-12 - GEM PATHS: - /Library/Ruby/Gems/1.8 - /Users/matthewcleghorn/.gem/ruby/1.8 - /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES: - http://rubygems.org/ Any help greatly appreciated. Thanks.

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• Array of templated structs

  - by Jakub Mertlik

  I have structs templated by int derived from a Base struct. struct Base { int i; double d; }; template< int N > struct Derv : base { static const int mN = N; }; I need to make an array of Derv< N where N can vary for each struct in that array. I know C/C++ does not allow arrays of objects of different types, but is there a way around this? I was thinking of separating the type information somehow (hints like pointers to Base struct or usage of union spring to my mind, but with all of these I don't know how to store the type information of each array element for usage DURING COMPILE TIME). As you can see, the memory pattern of each Derv< N is the same. I need to access the type of each array element for template specialization later in my code. The general aim of this all is to have a compile-time dispatch mechanism without the need to do a runtime "type switch" somewhere in the code. Thank you.

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• Occasional weird Glassfish errors, resolved by a restart?

  - by Pooria

  I'm developing a web app using netbeans with GlassFishv3. Every once in a while when I add a new feature in my app, glassfish starts nagging with stupid errors, after a lot of time wasting and panicking, i restart glassfish and run my application again, then suddenly the errors all go away and my site starts acting correctly. (or in case I have made a real mistake, i receive a reasonable & descriptive error from GF.) [Edit: the rest of the question was revealed to have been my own mistake.] But the problems don't end there. Recently, i added the ability to write comments in a (JSF) page, after the user submits their comment, i add it to the database and redirect to the same page, so that hopefully the page refreshes with the new comment, but it wont! The underlying Mysql database shows that the new comment has been added, but the page just wont show the new comment! I've tried everything (e.g. deleting browser cache, using different browsers) but only after restarting GF is when the page shows the new comment! Do you have any idea what the problem could be? Could this be a Glassfish bug? What i am using: JSF2, EJB3.1, JPA, MySql

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• How to calculate the height of the text rectangle from an NSString?

  - by mystify

  I know there is this one: sizeWithFont:minFontSize:actualFontSize:forWidth:lineBreakMode: But since the CGSize always has the same height and doesn't adjust to any shrinked text or whatsoever, the CGSize is not telling how heigh the text is. Example: Make a UILabel with 320 x 55 points and put a loooooooooooooong text in there. Let the label shrink the text down. Surprise: CGSize.height remains the same height even if the text is so tiny that you need a microscope. Ok so after banging my head against my macbook pro which is half way broken now, the only think that can help is that nasty actualFontSize. But the font size is in pica I think, it's not really what you get on the screen, isn't it? When that font size is 10, is my text really 10 points heigh at maximum? Once in a while I tried exactly that, and as soon as the text had a y or some character that extends to below (like that tail of an y does), it is out of bounds and the whole text is bigger than 10 points. So how would you calculate the real text height for a single line uilabel without getting a long beard and some hospital experience?

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• "pushModalScreen called by a non-event thread" thrown on event thread

  - by JGWeissman

  I am trying to get my Blackberry application to display a custom modal dialog, and have the opening thread wait until the user closes the dialog screen. final Screen dialog = new FullScreen(); ...// Fields are added to dialog Application.getApplication().invokeAndWait(new Runnable() { public void run() { Application.getUiApplication().pushModalScreen(dialog); } }); This is throwing an Exception which says "pushModalScreen called by a non-event thread" despite the fact that I am using invokeAndWait to call pushModalScreen from the event thread. Any ideas about what the real problem is? Here is the code to duplicate this problem: package com.test; import net.rim.device.api.ui.*; import net.rim.device.api.ui.component.*; import net.rim.device.api.ui.container.*; public class Application extends UiApplication { public static void main(String[] args) { new Application(); } private Application() { new Thread() { public void run() { Application.this.enterEventDispatcher(); } }.start(); final Screen dialog = new FullScreen(); final ButtonField closeButton = new ButtonField("Close Dialog"); closeButton.setChangeListener(new FieldChangeListener() { public void fieldChanged(Field field, int context) { Application.getUiApplication().popScreen(dialog); } }); dialog.add(closeButton); Application.getApplication().invokeAndWait(new Runnable() { public void run() { try { Application.getUiApplication().pushModalScreen(dialog); } catch (Exception e) { // To see the Exception in the debugger throw new RuntimeException(e.getMessage()); } } }); System.exit(0); } } I am using Component Package version 4.5.0.

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• How to approach parallel processing of messages?

  - by Dan

  I am redesigning the messaging system for my app to use intel threading building blocks and am stumped trying to decide between two possible approaches. Basically, I have a sequence of message objects and for each message type, a sequence of handlers. For each message object, I apply each handler registered for that message objects type. The sequential version would be something like this (pseudocode): for each message in message_sequence <- SEQUENTIAL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The first approach which I am considering processes the message objects in turn (sequentially) and applies the handlers concurrently. Pros: predictable ordering of messages (ie, we are guaranteed a FIFO processing order) (potentially) lower latency of processing each message Cons: more processing resources available than handlers for a single message type (bad parallelization) bad use of processor cache since message objects need to be copied for each handler to use large overhead for small handlers The pseudocode of this approach would be as follows: for each message in message_sequence <- SEQUENTIAL parallel_for each handler in (handler_table for message.type) apply handler to message <- PARALLEL The second approach is to process the messages in parallel and apply the handlers to each message sequentially. Pros: better use of processor cache (keeps the message object local to all handlers which will use it) small handlers don't impose as much overhead (as long as there are other handlers also to be run) more messages are expected than there are handlers, so the potential for parallelism is greater Cons: Unpredictable ordering - if message A is sent before message B, they may both be processed at the same time, or B may finish processing before all of A's handlers are finished (order is non-deterministic) The pseudocode is as follows: parallel_for each message in message_sequence <- PARALLEL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The second approach has more advantages than the first, but non-deterministic ordering is a big disadvantage.. Which approach would you choose and why? Are there any other approaches I should consider (besides the obvious third approach: parallel messages and parallel handlers, which has the disadvantages of both and no real redeeming factors as far as I can tell)? Thanks!

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• Automatic music rating based on listening habits

  - by marco92w

  I've created a Winamp-like music player in Delphi. Not so complex, of course. Just a simple one. But now I would like to add a more complex feature: Songs in the library should be automatically rated based on the user's listening habits. This means: The application should "understand" if the user likes a song or not. And not only whether he/she likes it but also how much. My approach so far (data which could be used): Simply measure how often a song was played per time. Start counting time when the song was added to the library so that recent songs don't have any disadvantage. Measure how long a song was played on average (minutes). Starting a song but directly change to another one should have a bad influence on the ranking since the user didn't seem to like the song. ... Could you please help me with this problem? I would just like to have some ideas. I don't need the implementation in Delphi.

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• Accepting more simultaneous keyboard inputs

  - by unknownthreat

  Sometimes, a normal computer keyboard will only accept user's inputs up to a certain key simultaneously. I got a logitech keyboard that can accept up to 3-4 key presses at the same time. The computer does not accept any more input if you press more than 4 keys for this keyboard. And it also depends on certain areas of your keyboard as well. Some locations allow more key to be pressed (like the arrow keys), while some locations permit you to press only 1-2 keys. This also differs from keyboard to keyboard as well. Some older keyboards only accept up 1-2 keys. This isn't problematic with usual office work, but when it comes to gaming. For instance, imagine a platform game, where you have to jump, attack, and control direction at the same time. This implies several key presses and some keyboards cannot accept such simultaneous input. However, I've tried this on several games and the amount of possible keyboard inputs seem to be also different. Therefore, we have two issues: Keyboards have different amount of simultaneous inputs. Some games can accept more keyboard inputs than other games. At first, I thought this is hardware only problem, but why do some programs behave differently? Why some programs can accept more keyboard inputs than other programs? So how can we write our programs to accept more keyboard inputs?

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• JTA or LOCAL transactions in JPA2+Hibernate 3.6.0?

  - by Pangea

  We are in the process of re-thinking our tech stack and below are our choices (We can't live without Spring and Hibernate due to the complexity etc of the app). We are also moving from J2EE 1.4 to JEE 5. Tech stack JEE 5 JPA 2.0 (I know JEE 5 only supports JPA 1.0 but we want to use Hibernate as the JPA provider) Hibernate 3.6.0 (We already have lots of hbm files with custom types etc. so we doesn't want to migrate them at this time to JPA. This means we want both jpa/hbm mappings work together and hence the Hibernate as the JPA provider instead of using the default that comes with App Server) Now the problems is that I want to stick with local transactions but other team members want to use JTA. I have been working with J2EE for last 9 years and I've heard time and again people suggesting to stick with local transactions if I doesn't need two phase commits. This is not only for performance reasons but debugging/troubleshooting a local transaction is lot easier than a distributed transaction. My suggestion is to use spring declarative transaction management + local transactions (HibernateTransactionManager) I want to make sure if I am being paranoid or I have a valid point. I'd like to hear what the rest of the JEE world thinks. Thank you.

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• How to create a "Shell IDList Array" to support drag-and-drop of virtual files from C# to Windows Ex

  - by JustABill

  I started trying to implement drag-and-drop of virtual files (from a C# 4/WPF app) with this codeplex tutorial. After spending some time trying to figure out a DV_E_FORMATETC error, I figured out I need to support the "Shell IDList Array" data format. But there seems to be next to zero documentation on what this format actually does. After some searching, I found this page on advanced data transfer which said that a Shell IDList Array was a pointer to a CIDA structure. This CIDA structure then contains the number of PIDLs, and a list of offsets to them. So what the hell is a PIDL? After some more searching, this page sort of implies it's a pointer to an ITEMIDLIST, which itself contains a single member that is a list of SHITEMIDs. My next idea was to try dragging a file from another application with virtual files. I just got a MemoryStream back for this format. At least I know what class to provide for the thing, but that doesn't help at all for explaining what to put in it. So now that that's explained, I still have no idea how to create one of these things so that it's valid. There's two real questions here: What is a valid "abID" member for a SHITEMID? These virtual files only exist with my program; will the thing they are dragged to pass the "abID" back later when it executes GetData? Do they have to be system-unique? Why are there two levels of lists; a list of PIDLs and each PIDL has a list of SHITEMIDs? I'm assuming one of them is one for each file, but what's the other one for? Multiple IDs for the same file? Any help or even links that explain what I should be doing would be greatly appreciated.

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• C++ boost mpl vector

  - by Gokul

  I understand that the following code won't work, as i is a runtime parameter and not a compile time parameter. But i want to know, whether there is a way to achieve the same. i have a list of classes and i need to call a template function, with each of these classes. void GucTable::refreshSessionParams() { typedef boost::mpl::vector< SessionXactDetails, SessionSchemaInfo > SessionParams; for( int i = 0; i < boost::mpl::size<SessionParams>::value; ++i ) boost::mpl::at<SessionParams, i>::type* sparam = g_getSessionParam< boost::mpl::at<SessionParams, i>::type >(); sparam->updateFromGucTable(this); } } Can someone suggest me a easy and elegant way to perform the same? i need to iterate through the mpl::vector and use the type to call a global function and then use that parameter to do some run-time operations. Thanks in advance, Gokul. Working code typedef boost::mpl::vector< SessionXactDetails, SessionSchemaInfo > SessionParams; class GucSessionIterator { private: GucTable& m_table; public: GucSessionIterator(GucTable& table) :m_table(table) { } template< typename U > void operator()(const U& ) { g_getSessionParam<U>()->updateFromGucTable(m_table); } }; void GucTable::refreshSessionParams() { boost::mpl::for_each< SessionParams >( GucSessionIterator(*this) ); return; }

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• _dl_runtime_resolve -- When do the shared objects get loaded in to memory?

  - by windfinder

  We have a message processing system with high performance demands. Recently we have noticed that the first message takes many times longer then subsequent messages. A bunch of transformation and message augmentation happens as this goes through our system, much of it done by way of external lib. I just profiled this issue (using callgrind), comparing a "run" of just one message with a "run" of many messages (providing a baseline of comparison). The main difference I see is the function "do_lookup_x" taking up a huge amount of time. Looking at the various calls to this function, they all seem to be called by the common function: _dl_runtime_resolve. Not sure what this function does, but to me this looks like the first time the various shared libraries are being used, and are then being loaded in to memory by the ld. Is this a correct assumption? That the binary will not load the shared libraries in to memory until they are being prepped for use, therefore we will see a massive slowdown on the first message, but on none of the subsequent? How do we go about avoiding this? Note: We operate on the microsecond scale.

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• Interesting questions related to lighttpd on Amazon EC2

  - by terence410

  This problem appeared today and I have no idea what is going on. Please share you ideas. I have 1 EC2 DB server (MYSQL + NFS File Sharing + Memcached). And I have 3 EC2 Web servers (lighttpd) where it will mounted the NFS folders on the DB server. Everything going smoothly for months but suddenly there is an interesting phenomenon. In every 8 minutes to 10 minutes, PHP file will be unreachable. This will last about 1 minute and then back to normal. Normal files like .html file are unaffected. All servers have the same problem exactly at the same time. I have spent one whole day to analysis the reason. Finally, I find out when the problem appear, the file descriptor of lighttpd suddenly increased a lot. I used ls /proc/1234/fd | wc -l to check the number of fd. The # of fd is around 250 in normal time. However, when the problem appeared, it will be raised to 1500 and then back to normal. It sounds funny, right? Do you have any idea what's going on? ======================== The CPU graph of one of the web server.

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• Handling selection and deselection of objects in a user interface

  - by Dennis

  I'm writing a small audio application (in Silverlight, but that's not really relevant I suppose), and I'm a struggling with a problem I've faced before and never solved properly. This time I want to get it right. In the application there is one Arrangement control, which contains several Track controls, and every Track can contain AudioObject controls (these are all custom user controls). The user needs to be able to select audio objects, and when these objects are selected they are rendered differently. I can make this happen by hooking into the MouseDown event of the AudioObject control and setting state accordingly. So far so good, but when an audio object is selected, all other audio objects need to be deselected (well, unless the user holds the shift key). Audio objects don't know about other audio objects though, so they have no way to tell the rest to deselect themselves. Now if I would approach this problem like I did the last time I would pass a reference to the Arrangement control in the constructor of the AudioObject control and give the Arrangement control a DeselectAll() method or something like that, which would tell all Track controls to deselect all their AudioObject controls. This feels wrong, and if I apply this strategy to similar issues I'm afraid I will soon end up with every object having a reference to every other object, creating one big tightly coupled mess. It feels like opening the floodgates for poorly designed code. Is there a better way to handle this?

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