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• Visual Studio setup problem - 'A problem has been encountered while loading the setup components. Ca

  - by kronoz

  Hi All, I've had a serious issue with my Visual Studio 2008 setup. I receive the ever-so-useful error 'A problem has been encountered while loading the setup components. Canceling setup.' whenever I try to uninstall, reinstall or repair Visual Studio 2008 (team system version). If I can't resolve this issue I have no choice but to completely wipe my computer and start again which will take all day long! I've recently received very strange errors when trying to build projects regarding components running out of memory (despite having ~2gb physical memory free at the time) which has rendered my current VS install useless. Note I installed VS2005 shell version using the vs_setup.msi file in the SQL Server folder after I had installed VS2008, in order to gain access to the SQL Server 2005 Reporting Services designer in Business Intelligence Development Studio (this is inexplicably unavailable in VS2008). Does anyone have any solutions to this problem? P.S.: I know this isn't directly related to programming, however I feel this is appropriate to SO as it is directly related to my ability to program at all! Note: A colleague found a solution to this problem, hopefully this should help others with this problem.

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• Legit? Two foreign keys referencing the same primary key.

  - by Ryan

  Hi All, I'm a web developer and have recently started a project with a company. Currently, I'm working with their DBA on getting the schema laid out for the site, and we've come to a disagreement regarding the design on a couple tables, and I'd like some opinions on the matter. Basically, we are working on a site that will implement a "friends" network. All users of the site will be contained in a table tblUsers with (PersonID int identity PK, etc). What I am wanting to do is to create a second table, tblNetwork, that will hold all of the relationships between users, with (NetworkID int identity PK, Owners_PersonID int FK, Friends_PersonID int FK, etc). Or conversely, remove the NetworkID, and have both the Owners_PersonID and Friends_PersonID shared as the Primary key. This is where the DBA has his problem. Saying that "he would only implement this kind of architecture in a data warehousing schema, and not for a website, and this is just another example of web developers trying to take the easy way out." Now obviously, his remark was a bit inflammatory, and that have helped motivate me to find an suitable answer, but more so, I'd just like to know how to do it right. I've been developing databases and programming for over 10 years, have worked with some top-notch minds, and have never heard this kind of argument. What the DBA is wanting to do is instead of storing both the Owners_PersonId and Friends_PersonId in the same table, is to create a third table tblFriends to store the Friends_PersonId, and have the tblNetwork have (NetworkID int identity PK, Owner_PersonID int FK, FriendsID int FK(from TBLFriends)). All that tblFriends would house would be (FriendsID int identity PK, Friends_PersonID(related back to Persons)). To me, creating the third table is just excessive in nature, and does nothing but create an alias for the Friends_PersonID, and cause me to have to add (what I view as unneeded) joins to all my queries, not to mention the extra cycles that will be necessary to perform the join on every query. Thanks for reading, appreciate comments. Ryan

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• Which pattern should be used for editing properties with modal view controller on iPhone?

  - by Matthew Daugherty

  I am looking for a good pattern for performing basic property editing via a modal view on the iPhone. Assume I am putting together an application that works like the Contacts application. The "detail" view controller displays all of the contact's properties in a UITableView. When the UITableView goes into edit mode a disclosure icon is displayed in the cells. Clicking a cell causes a modal "editor" view controller to display a view that allows the user to modify the selected property. This view will often contain only a single text box or picker. The user clicks Cancel/Save and the "editor" view is dismissed and the "detail" view is updated. In this scenario, which view is responsible for updating the model? The "editor" view could update the property directly using Key-Value Coding. This appears in the CoreDataBooks example. This makes sense to me on some level because it treats the property as the model for the editor view controller. However, this is not the pattern suggested by the View Controller Programming Guide. It suggests that the "editor" view controller should define a protocol that the "detail" controller adopts. When the user indicates they are done with the edit, the "detail" view controller is called back with the entered value and it dismisses the "editor" view. Using this approach the "detail" controller updates the model. This approach seems problematic if you are using the same "editor" view for multiple properties since there is only a single call-back method. Would love to get some feedback on what approach works best.

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• What is the difference between the Lego Mindstorms 1.0 and 2.0

  - by Gavimoss

  I am thinking about buying a mindstorms kit (I don't currently own one but I have used 1.0 at university) and I am a bit unsure as to the benefits of 2.0 over 1.0. I have seen other posts on the subject all saying generally 2.0 is better but I have some more specific questions about this that I can't seem to find any answers on. Apart from the different lego pieces and sensors you get with the 2.0 kit, is there any difference between a 1.0 nxt brick and 2.0 nxt brick? From what I can determine from other sources, they are the same except for the firmware installed. Am I right in saying I could buy a 1.0 kit and install the same firmware that comes with the 2.0 kit and the bricks would be the same or is the 1.0 brick not compatible with the 2.0 firmware??? Also, I plan to use a different programming language like c or java so I need to install specific firmware for that anyway like librcx or lejos right? So if using c or java as opposed to the provided lego coding methods it doesn't matter if I am using 1.0 or 2.0 (except for the lego pieces in the kit) am I right? In a nutshell, assuming I am using librcx or lejos and I don't care about the sensors and lego pieces included, is there any benefit to buying a 2.0 kit over the 1.0 kit? Thanks in advance

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• WCF fault logging and SQL Exception 4060 error.

  - by Bill

  I have been attempting to compile/run a sample WCF application from Juval Lowy's website (author of Programming WCF Services & founder of IDesign) for several days. The example app utilizes Juval's ServiceModelEx library which logs faults/errors to a "WCFLogbook" SQL database. Unfortunately, when the sample app faults, I get the following error: SQL Exception 4060: "Cannot open database \"WCFLogbook\" requested by the login. The login failed.\r\nLogin failed for user 'Bill-PC\Bill'." I confirmed that the SQL WCFLogbook database has been created and have granted all of the appropriate permissions for my (Bill-PC\Bill) access to the database. Additionally port 8006 and port 1433 have been opened in the Firewall. TCP/IP has been enabled and "Allow remote connections to this server" has been checked. I am using the following endpoint within the App.Config file: <client> <endpoint name="LogbookTCP" address="net.tcp://Bill-PC:8006/LogbookManager" binding="netTcpBinding" contract="ILogbookManager" /> </client> Unfortunately SQL is a 'world' that I hadn't needed to venture into before now and I am terribly frustrated with my lack of success. Would anyone have any other suggestions on how to get this working? Have I missed anything?

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• what can be causes of http server crash?

  - by mithunmo

  Hello , I am using WAMP server on Windows XP. - Apache 2.2.11 - MySQL 5.1.36 (INNODB engine) - PHP 5.3.0 I observe that my WAMP server crashes in the following scenarios 1) IF I use a Low end PC ( low processor speed and low RAM) 2) After making some changes to httpd.conf file .For eg changing the Allow from IP address . But here it crashes only once and then it starts to work fine. 3) Random crashes CRASH LOG szAppName : httpd.exe szAppVer : 2.2.11.0 szModName : php5ts.dll szModVer : 5.3.0.0 offset : 0000c309 C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\httpd.exe.mdmp C:\DOCUME~1\blrcom\LOCALS~1\Temp\WERc677.dir00\appcompat.txt My questions 1) Does high CPU utilization/LOW RAM can also cause the HTTP server to crash ? 2) excessive file reading as in every 10 seconds ? 3) unlimited script execution time . I have set the maximum execution time in php script to 0 as my script has to execute for sometimes 2-3 days. Is there any way to avoid this ? 4) Access to Database ? Should we use lock before reading and writing Can these be the reasons for random wamp server crashes ? OR is is some other programming error ? Please guide me . Regards, Mithun

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• What do you do when your team leader doesn't know something simple?

  - by leppie

  What do you do when your team leader does not know why the following is wrong: a.SomeProp = a.SomeProp; // no funny side-effects, plain old property He claims 15 years of programming experience, and 7 years of C#/.NET. To me, someone of 3-6 months experience should know this. What I have done: Tried to make him understand why it is wrong. He told me not to criticize him. Told him it's not about criticism, but project risk. He got upset with me. I have addressed the risk of this person with our manager (few weeks back). I have addressed my concerns with this person with our manager several times, since 1 month after I started there (7 months now). Currently, I just feel like just not going back to work... I hardly have any nails left, and this is really just the tip of the iceberg. As nothing has changed after I have spoken to the manager for the last 6 months, I feel like I need to make some sort of ultimatum. Do you have any suggestions? PS: Please do not make this subjective. I have no need for arguing. The level of incompetence is pretty clear. I just need some advice before going insane. Update: Thanks for all the answers (trying to update before close, buggers). I think I will forward this thread to our manager :) Update 2: I sent my manager another mail with my concerns, and a link to this question. Awaiting response.

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• Algorithm to get through a maze

  - by Sam

  Hello, We are currently programming a game (its a pretty unknown language: modula 2), And the problem we encountered is the following: we have a maze (not a perfect maze) in a 17 x 12 grid. The computer has to generate a way from the starting point (9, 12) to the end point (9, 1). I found some algorithms but they dont work when the robot has to go back: xxxxx x => x x xxx or: xxxxx x xxxxxx x x x x x xxxxxx x => x xxxxxxxxx I found a solution for the first example type but then the second type couldn't be solved and the solution I made up for the second type would cause the robot to get stuck in the first type of situation. It's a lot of code so i'll give the idea: WHILE (end destination not reached) DO { try to go right, if nothing blocks you: go right if you encounter a block, try up until you can go right, if you cant go up anymore try going down until you can go right, (starting from the place you first were blocked), if you cant go down anymore, try one step left and fill the spaces you tested with blocks. } This works for the first type of problem ... not for the second one. Now it could be that i started wrong so i am open for better algorithms or solutions specificaly to how i could improve my algorithm. Thanks a lot!!

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• Suggestions for entering mobile development -- pure iPhone SDK, Android SDK, Mono Touch or Titanium

  - by Tom Cabanski

  I am entering mobile development. I have been working primarily in .NET since 1.0 came out in beta. Before that, I was mostly a C++ and Delphi guy and still dabble in C++ from time to time. I do web apps quite a bit so I am reasonably proficient with Javascript, JQuery and CSS. I have also done a few Java applications. I started web programming with CGI and live mostly in the ASP.NET MVC world these days. I am trying to decide on which platform/OS and tool to select. I am concerned with the size of the market available for my applications as well as the marketibility of the skills I will pick up. The apps I have in mind would work on both phones and pads. Some aspects of what I have in mind will play better on the bigger screens that will be available on pads. Here are the options I am considering: Apple iPhone/iPad using pure Apple SDK (Objective-C) Apple iPhone/iPad using Mono Touch (C#) Android using pure Android SDK (Java) Multiple platforms using something like Titanium to generate native apps from web technologies (HTML, CSS and Javascript) Multiple platforms using HTML5 web applications that run in the browser (HTML, CSS and Javascript). Which option would you choose? Do you have a different suggestion? What are the pros and cons?

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• ps forrest for session id

  - by azatoth

  Often I want to get a nice readout what process are running and their relationship; I usually by habit runs ps auxfww and eventual grep for the process in question. Having been thinking about the problem I tried to create an oneliner to get the process tree in ps ufww format for all processes which has the session id specified by arbitrary process name(s); ending up in following code: ps ufww --sid=$(ps -C apache2 -o sess --no-headers | sort | uniq | grep -v -E '^ +0$' | awk 'NR==1{x=$0;next}NF{x=x","$0};END{gsub(/[[:space:]]*/,"",x);print x}') giving for example following output: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 4157 0.0 0.1 41264 3120 ? Ss Jun11 0:00 /usr/sbin/apache2 -k start www-data 4329 0.0 0.0 41264 1976 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 4330 0.0 0.0 41264 2028 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 4331 0.0 0.0 41264 2028 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 4332 0.0 0.0 41264 2028 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 4333 0.0 0.0 41264 2032 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 6648 0.0 0.0 41264 1884 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 6654 0.0 0.0 41264 1884 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start www-data 6655 0.0 0.0 41264 1884 ? S Jun11 0:00 \_ /usr/sbin/apache2 -k start I do wonder now if anyone has an better idea to solve this issue? Are there anything out there that is easier to "oneline" and gives above or better information? For example I would actually want to have included all childs relative any parent. (uncertain if this should be on SF instead, but felt it was more like an programming question)

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• How does Visual Studio decide the order in which stack variables should be allocated?

  - by Jason

  I'm trying to turn some of the programs in gera's Insecure Programming by example into client/server applications that could be used in capture the flag scenarios to teach exploit development. The problem I'm having is that I'm not sure how Visual Studio (I'm using 2005 Professional Edition) decides where to allocate variables on the stack. When I compile and run example 1: int main() { int cookie; char buf[80]; printf("buf: %08x cookie: %08x\n", &buf, &cookie); gets(buf); if (cookie == 0x41424344) printf("you win!\n"); } I get the following result: buf: 0012ff14 cookie: 0012ff64 buf starts at an address eighty bytes lower than cookie, and any four bytes that are copied in buf after the first eighty will appear in cookie. The problem I'm having is when I place this code in some other function. When I compile and run the following code, I get a different result: buf appears at an address greater than cookie's. void ClientSocketHandler(SOCKET cs){ int cookie; char buf[80]; char stringToSend[160]; int numBytesRecved; int totalNumBytes; sprintf(stringToSend,"buf: %08x cookie: %08x\n",&buf,&cookie); send(cs,stringToSend,strlen(stringToSend),NULL); The result is: buf: 0012fd00 cookie: 0012fcfc Now there is no way to set cookie to arbitrary data via overwriting buf. Is there any way to tell Visual Studio to allocate cookie before buf? Is there any way to tell beforehand how the variables will be allocated? Thanks, Jason

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• How do you use asynchronous ORMs without huge callback chains?

  - by hornairs

  I'm using the relatively immature Joose Javascript ORM plugin (project page) to persist objects in an Appcelerator Titanium (company page) mobile project. Since it's client side storage, the application has to check to see if the database is initialized before starting up the ORM since it inspects the DB tables to construct the classes. My problem is that this sequence of operations (and if this one is like this, other things down the road) takes a lot of callbacks to complete. I have a lot of jumping around in the code that isn't apparent to a maintainer and results in some complex call graphs and whatnot. So, I ask these questions: How would you asynchronously initialize a database and populate it with seed data using an ORM that needs the schema to be correct to function? Do you have any general strategies or links for async/event driven programming and keeping the call graph simple and understandable? Do you have any suggestions for Javascript ORMs/meta object systems that work with HTML 5 as a storage engine and are hopefully framework agnostic? Am I just a big newb and should be able to work this out with ease? Thanks folks!

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• -[CFString length]: message sent to deallocated instance 0x3881940 when i scroll to near the bottom

  - by James

  Hey guys, i've got a problem debugging an iphone app that i'm attempting to write and it's got me stumped, bear with me, i'm a n00b to programming and might get some of the terminology wrong but i'll try to explain it as best as i can. The app gets an XML doc from the a web site, parses it into an array, and then displays it in a table view, i have the parser in a separate file. The ViewDidLoad in RootViewController sends it a url, the parser goes to work and then returns an NSMutableArray. When i run the app it works fine with small XML files (5 entries or so, and 1-3 sections), but when i use a larger one(20+ rows, over 12 sections) i get the error "-[CFString length]: message sent to deallocated instance 0x3881940" when i scroll near the bottom of the tableview, just as the last section title is about to come onto the viewable area on the screen to be precise. if i return a static string instead of the object in my array in this method it doesn't crash, but i can use NSLog to call the array and it returns the title no problems. - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)indexPath { return [[returnedEvents objectAtIndex:indexPath ] objectAtIndex:0]; } The returnedEvents array isn't released until -(void) dealloc {} I have read a few other posts on here, and a few guides on debugging and as of yet am unable to find anything that was able to help me, i'd be more than happy to post some code up here and any more information, i'm just not sure where to start... Thanks in advance for anyone willing to have a go at helping me out.

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• Is this error caused by a 64-bit library being accessed by a Java program running in a 32-bit JVM?

  - by Mike

  I'm trying to create a simple Java app that uses JNI to call some native functions. I've followed the examples in the JNI Programming Guide and can't seem to get them to work. I have the following Hello World program, written in Java: class HelloWorld { private native void print(); public static void main(String [] args) { new HelloWorld().print(); } static { System.load("/home/mike/Desktop/libHelloWorld.so"); } } I compile it using javac HelloWorld.java, just like normal. Then I run javah -jni HelloWorld, and finally the following: gcc34 -shared -fpic -o libHelloWorld.so -I/<path to JDK>/include -I/<path to JDK>/include/linux HelloWorld.c gcc34 is the name of the GCC program on my machine here at work (I don't control that) and I obviously place the real path to the JDK in that command. When I run my program, using the standard java HelloWorld, I get an error saying the following: Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/mike/Desktop/libHelloWorld.so: /home/mike/Desktop/libHelloWorld.so: wrong ELF class: ELFCLASS64 (Possible causes: architecture word width mismatch) at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1778) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1674) at java.lang.Runtime.load0(Runtime.java:770) at java.lang.System.load(System.java:1003) at HelloWorld.<clinit>(HelloWorld.java:8) Could not find the main class: HelloWorld. Program will exit. I know I'm running a 32-bit JVM (and unfortunately, as of right now, I'm not allowed to get a 64-bit JVM). I tried telling GCC to compile in 32-bit mode using the "-m32" option, but we don't have (and again, can't get) what we need for that. Does this sound like a 32/64-bit conflict or something else?

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• Android: Creating a Scrollable Layout

  - by MD

  I'm trying to create a "scrollable" layout in Android. Even using developers.android.com, though, I feel a little bit lost at the moment. I'm somewhat new to Java, but not so much that I feel I should be having these issues--being new to Android is the bigger problem right now. The layout I'm trying to create should scroll in a sort of a "grid". I THINK what I'm looking for is the Gallery view, but I'm really lost as to how to implement it at the moment. I want it to "snap" to center the frame, like in the actual Gallery application. Essentially, if I had a photo gallery of 9 pictures, the idea is to scroll between them up/down AND side to side, in a 3x3 manner. Doesn't need to dynamically adjust, or anything like that, I just want a grid I can scroll through. I'm also not asking for anyone to give me explicit code for it--I'm trying to learn, more than anything. But pointing me in the right direction for helpful layout programming resources would be greatly appreciated, and confirming if it's a Gallery view I'm looking for would also be really helpful. EDIT: To clarify, the goal is to have ONE item on screen at a time. If you scroll between one item and the next, the previous one leaves the screen, and the new one snaps into place. So if it were a photo gallery, each spot on the grid would take up the entire screen size, approximately, and would be flung out of the viewable area when you slide across to the next photo, in either direction. (Photos are just an example for illustration purposes)

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• How to handle One View with multiple ViewModel and fire different Commands

  - by Naresh

  Hi All, I have senario in which one view and view has binding with multiple ViewModel. Eg. One View displaying Phone Detail and ViewModel as per bellow: Phone basic features- PhoneViewModel, Phone Price Detail- PhoneSubscriptionViewModel, Phone Accessories- PhoneAccessoryViewModel For general properties- PhoneDetailViewModel I have placed View's general properties to PhoneViewModel.Now senario is like this: By default View displays Phone Basic feaures which is bind with ObservationCollection of PhoneViewModel. My view have button - 'View Accessories', onclick of this button one popup screen- in my design I have display/hide Grid and bind it with ObservationCollection of PhoneAccessoryViewModel. Now problem begins- Accessory List also have button 'View Detail' onclick I have to open one popup screen, here also I had placed one Grid and Visible/Hide it. I have bind 'ViewAccessoryDetailCommand' command to 'View Detail' button. And on command execution one function fires and set property which Visible the Popup screen. Using such programming command fires, function calls but the property change not raises and so my view does not display popup. Summary: One View-- ViewModel1--Grid Bind view ViewModel2 --Grid Have Button and Onclick display new Grid which binded with ViewModel3-this Command fires but property not raises. I think there is some problem in my methodology, Please, give your suggetions.

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• Why are floating point values so prolific?

  - by Kibbee

  So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster with floating point numbers, however, I can think of only a few cases that they actually the right data type would be using. If you sat back and think about every time you used a floating point value, how many times did you say, well, some error would be ok, as long as the result was a few microseconds faster. It really makes me think because Jeff was talking about NP completeness, and how heuristics give an answer that is kind of right. And well, computers shouldn't do that. They should give you the answer that is correct. Yet we see floating point values used in many applications where they are completely not valid. What really bugs me, isn't that floating point exists, but that in many languages, there isn't even a viable alternative, non-floating point, decimal value. A lot of programmers when doing financial applications have to fall back to storing the number of cents in an integer field. Which brings with it all kinds of other problems. Why do floats continue to be so prolific, even though they can't represent the real answer, and we expect computers to be accurate? [EDIT] Just to clarify, I was talking about Base 2 floating points, and not base 10 floating points. .Net offers the Decimal data type, which is a base 10 floating point value which offers a much better representation of the numbers we deal with on a daily basis in most computer programs. I find it hard to believe that even modern languages like Java don't support base 10 floating point values, unless you want to move into the realm of things like BigDecimal, which isn't really the right answer either in a lot of situations.

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• Nested Routes and Parameters for Rails URLs (Best Practice)

  - by viatropos

  Hey there, I have a decent understanding of RESTful urls and all the theory behind not nesting urls, but I'm still not quite sure how this looks in an enterprise application, like something like Amazon, StackOverflow, or Google... Google has urls like this: http://code.google.com/apis/ajax/ http://code.google.com/apis/maps/documentation/staticmaps/ https://www.google.com/calendar/render?tab=mc Amazon like this: http://www.amazon.com/books-used-books-textbooks/b/ref=sa_menu_bo0?ie=UTF8&node=283155&pf_rd_p=328655101&pf_rd_s=left-nav-1&pf_rd_t=101&pf_rd_i=507846&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1PK4ZKN4YWJJ9B86ANC9 http://www.amazon.com/Ruby-Programming-Language-David-Flanagan/dp/0596516177/ref=sr_1_1?ie=UTF8&s=books&qid=1258755625&sr=1-1 And StackOverflow like this: http://stackoverflow.com/users/169992/viatropos http://stackoverflow.com/questions/tagged/html http://stackoverflow.com/questions/tagged?tagnames=html&sort=newest&pagesize=15 So my question is, what is best practice in terms of creating urls for systems like these? When do you start storing parameters in the url, when don't you? These big companies don't seem to be following the rules so hotly debated in the ruby community (that you should almost never nest URLs for example), so I'm wondering how you go about implementing your own urls in larger scale projects because it seems like the idea of not nesting urls breaks down at anything larger than a blog. Any tips?

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• Starter question of declarative style SQLAlchemy relation()

  - by jfding

  I am quite new to SQLAlchemy, or even database programming, maybe my question is too simple. Now I have two class/table: class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(40)) ... class Computer(Base): __tablename__ = 'comps' id = Column(Integer, primary_key=True) buyer_id = Column(None, ForeignKey('users.id')) user_id = Column(None, ForeignKey('users.id')) buyer = relation(User, backref=backref('buys', order_by=id)) user = relation(User, backref=backref('usings', order_by=id)) Of course, it cannot run. This is the backtrace: File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/state.py", line 71, in initialize_instance fn(self, instance, args, kwargs) File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 1829, in _event_on_init instrumenting_mapper.compile() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 687, in compile mapper._post_configure_properties() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/mapper.py", line 716, in _post_configure_properties prop.init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/interfaces.py", line 408, in init self.do_init() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 716, in do_init self._determine_joins() File "/Library/Python/2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/properties.py", line 806, in _determine_joins "many-to-many relation, 'secondaryjoin' is needed as well." % (self)) sqlalchemy.exc.ArgumentError: Could not determine join condition between parent/child tables on relation Package.maintainer. Specify a 'primaryjoin' expression. If this is a many-to-many relation, 'secondaryjoin' is needed as well. There's two foreign keys in class Computer, so the relation() callings cannot determine which one should be used. I think I must use extra arguments to specify it, right? And howto? Thanks

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• What is the recommended coding style for PowerShell?

  - by stej

  Is there any recommended coding style how to write PowerShell scripts? It's not about how to structure the code (how many functions, if to use module, ...). It's about 'how to write the code so that it is readable'. In programming languages there are some recommended coding styles (what to indent, how to indent - spaces/tabs, where to make new line, where to put braces,...), but I haven't seen any suggestion for PowerShell. What I'm interested particularly in: How to write parameters function New-XYZItem ( [string] $ItemName , [scriptblock] $definition ) { ... (I see that it's more like 'V1' syntax) or function New-PSClass { param([string] $ClassName ,[scriptblock] $definition )... or (why to add empty attribute?) function New-PSClass { param([Parameter()][string] $ClassName ,[Parameter()][scriptblock] $definition )... or (other formatting I saw maybe in Jaykul's code) function New-PSClass { param( [Parameter()] [string] $ClassName , [Parameter()] [scriptblock] $definition )... or ..? How to write complex pipeline Get-SomeData -param1 abc -param2 xyz | % { $temp1 = $_ 1..100 | % { Process-somehow $temp1 $_ } } | % { Process-Again $_ } | Sort-Object -desc or (name of cmdlet on new line) Get-SomeData -param1 abc -param2 xyz | % { $temp1 = $_ 1..100 | % { Process-somehow $temp1 $_ } } | % { Process-Again $_ } | Sort-Object -desc | and what if there are -begin -process -end params? how to make it the most readable? Get-SomeData -param1 abc -param2 xyz | % -begin { init } -process { Process-somehow2 ... } -end { Process-somehow3 ... } | % -begin { } .... or Get-SomeData -param1 abc -param2 xyz | % ` -begin { init } ` -process { Process-somehow2 ... } ` -end { Process-somehow3 ... } | % -begin { } .... the indentitation is important here and what element is put on new line as well. I have covered only questions that come on my mind very frequently. There are some others, but I'd like to keep this SO question 'short'. Any other suggestions are welcome.

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• How to force two process to run on the same CPU?

  - by kovan

  Context: I'm programming a software system that consists of multiple processes. It is programmed in C++ under Linux. and they communicate among them using Linux shared memory. Usually, in software development, is in the final stage when the performance optimization is made. Here I came to a big problem. The software has high performance requirements, but in machines with 4 or 8 CPU cores (usually with more than one CPU), it was only able to use 3 cores, thus wasting 25% of the CPU power in the first ones, and more than 60% in the second ones. After many research, and having discarded mutex and lock contention, I found out that the time was being wasted on shmdt/shmat calls (detach and attach to shared memory segments). After some more research, I found out that these CPUs, which usually are AMD Opteron and Intel Xeon, use a memory system called NUMA, which basically means that each processor has its fast, "local memory", and accessing memory from other CPUs is expensive. After doing some tests, the problem seems to be that the software is designed so that, basically, any process can pass shared memory segments to any other process, and to any thread in them. This seems to kill performance, as process are constantly accessing memory from other processes. Question: Now, the question is, is there any way to force pairs of processes to execute in the same CPU?. I don't mean to force them to execute always in the same processor, as I don't care in which one they are executed, altough that would do the job. Ideally, there would be a way to tell the kernel: If you schedule this process in one processor, you must also schedule this "brother" process (which is the process with which it communicates through shared memory) in that same processor, so that performance is not penalized.

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• what type of bug causes a program to slowly use more processor power and all of a sudden go to 100%?

  - by reinier

  Hi, I was hoping to get some good ideas as to what might be causing a really nasty bug. This is a program which is transmitting data over a socket, and also receives messages back. I could explain lots more, but I don't think this will help here. I'm just searching for hypothetical problems which can cause the following behaviour: program runs processor time slowly accumulates (till around 60%) all of a sudden (could be after 30 but also after 60 seconds) the processor time shoots to 100%. the program halts completely In my syslog it always ends on one line with a memory allocation (something similar to: myArray = new byte[16384]) in the same thread. now here is the weird part: if I set the debugger anywhere...it immediately stops on that line. So just the act of setting a breakpoint, made the thread continue (it wasn't running since I saw no log output anymore) I was thinking 'deadlock' but that would not cause 100% processor power. If anything, the opposite. Also, setting a breakpoint would not cause a deadlock to end. anyone else a theoretical suggestion as to what kind of 'construct' might cause this effect? (apart from 'bad programming') ;^) thanks EDIT: I just noticed.... by setting the sendspeed slower, the problem shows itself much later than expected. I would think around the same amount of packets send...but no the amount of packets send is much higher this way before it has the same problem.

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• Implementing Naïve Bayes algorithm in Java - Need some guidance

  - by techventure

  hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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• Ruby Shoes packager including Shoes in the app

  - by user206481

  I can't seem to get the Ruby Shoes packager to correctly create an exe with Shoes included. I'm using the Raisins release (0.r1134), with the pack.rb replaced from github. The exe's the packager makes are all 70-80K files (they obviously don't include shoes or ruby). These exe's will run on my XP machine that already has Shoes on it. but when I copy them to another laptop they start a "Shoes is downloading" dialog that does nothing and then goes away. I need to make standalone Windows exe's, and my understanding was that the "Yes, I want Shoes included" option in the packager would do that. Did I misunderstand the intent? Is there a way to make this work? Hope so, because I love Shoes. As most women do. Hmm... maybe Shoes was _why's attempt at getting more women into programming as well as kids...but I digress. The other threads I've found here imply this will work: http://stackoverflow.com/questions/1390721/problem-in-ruby-shoes-packaging http://stackoverflow.com/questions/363218/shoes-packager-problem

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• Trouble with Rails has_many relationships

  - by Tchock

  I'm writing an app where a user can both create their own pages for people to post on, and follow posts on pages that users have created. Here is what my model relationships look like at the moment... class User < ActiveRecord::Base has_many :pages has_many :posts has_many :followings has_many :pages, :through => :followings, :source => :user class Page < ActiveRecord::Base has_many :posts belongs_to :user has_many :followings has_many :users, :through => :followings class Following < ActiveRecord::Base belongs_to :user belongs_to :page class Post < ActiveRecord::Base belongs_to :page belongs_to :user The trouble happens when I try to work my way down through the relationships in order to create a homepage of pages (and corresponding posts) a given user is following (similar to the way Twitter's user homepage works when you login - a page that provides you a consolidated view of all the latest posts from the pages you are following)... I get a "method not found" error when I try to call followings.pages. Ideally, I'd like to be able to call User.pages in a way that gets me the pages a user is following, rather than the pages they have created. I'm a programming and Rails newb, so any help would be much appreciated! I tried to search through as much of this site as possible before posting this question (along with numerous Google searches), but nothing seemed as specific as my problem...

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