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• Is there any algorithm that can solve ANY traditional sudoku puzzles, WITHOUT guessing (or similar techniques)?

  - by justin

  Is there any algorithm that solves ANY traditional sudoku puzzle, WITHOUT guessing? Here Guessing means trying an candidate and see how far it goes, if a contradiction is found with the guess, backtracking to the guessing step and try another candidate; when all candidates are exhausted without success, backtracking to the previous guessing step (if there is one; otherwise the puzzle proofs invalid.), etc. EDIT1: Thank you for your replies. traditional sudoku means 81-box sudoku, without any other constraints. Let us say the we know the solution is unique, is there any algorithm that can GUARANTEE to solve it without backtracking? Backtracking is a universal tool, I have nothing wrong with it but, using a universal tool to solve sudoku decreases the value and fun in deciphering (manually, or by computer) sudoku puzzles. How can a human being solve the so called "the hardest sudoku in the world", does he need to guess? I heard some researcher accidentally found that their algorithm for some data analysis can solve all sudoku. Is that true, do they have to guess too?

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• Why two subprocesses created by Java behave differently?

  - by Lily

  I use Java Runtime.getRuntime().exec(command) to create a subprocess and print its pid as follows: public static void main(String[] args) { Process p2; try { p2 = Runtime.getRuntime().exec(cmd); Field f2 = p2.getClass().getDeclaredField("pid"); f2.setAccessible(true); System.out.println( f2.get( p2 ) ); } catch (Exception ie) { System.out.println("Yikes, you are not supposed to be here"); } } I tried both C++ executable and Java executable (.jar file). Both executables will continuously print out "Hello World" to stdout. When cmd is the C++ executable, the pid is printed out to console but the subprocess gets killed as soon as main() returns. However, when I call the .jar executable in cmd, the subprocess does not get killed, which is the desired behavior. I don't understand why same Java code, with different executables can behave so differently. How should I modify my code so that I could have persistent subprocesses in Java. Newbie in this field. Any suggestion is welcomed. Lily

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• Really cool way to create custom UITabBar for iPhone app?

  - by ludicco

  Hi, I am doing a lot of researching lately about how to get a different looking with nice effects UITabBar on my iPhone app, but unfortunately I am only finding things on how to replace background color etc. Well, I've checked out this app called Momento which is pretty cool and presents a very slick tabBar: So there are a couple of elements here I would like to ask you guys if you could help me by giving me the right directions on how to get a similar effect :) Arrow above items: as you can see this app has this animated arrow that runs above the selected item with a very smooth animation. Selected Stated of the item's image is not that blue-ish default one neither the default state which displays in a different shade of brown and gray version. nice Items separators with beveled vertical lines. diferrent background image for the tabBar different height for the tabBar At this point after some research I am able to set the height and background image by subclassing UITabBarController but I'm still not sure on how to accomplish the other items specially the first one related to the nice arrow effect. If someone knows about a very good tutorial on how to do this it would be great for clarifying what can or can't be done by subclassing the UITabBarController and specially if can be done in Interface Builder :) I am just starting on this world off app development for iOS so if you could help me on that it would be really appreciated Thanks a lot in advance

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• jQuery Checkbox Error

  - by Zack Fernandes

  Hello, I am working on a jQuery-based todo list interface, and have hit a bit of a wall. The jQuery I am working with is a bit hacked together from various tutorials I have read, as I'm a bit of a beginner. $('#todo input:checkbox').click(function(){ var id = this.attr("value"); if(!$(this).is(":checked")) { alert("Starting."); $.ajax({ type: "GET", url: "/todos/check/"+id, success: function(){ alert("It worked.") } }); } }) This is the HTML I am using, <div id="todo"> <input type="checkbox" checked="yes" value="1"> Hello, world. <br /> </div> Any help on this would be greatly appreciated. For reference, thereason I have alerts in the jQuery is for debugging. The reason I can tell the code isn't working is because I am not getting these alerts. Thanks.

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• Multi threading in WCF RIA Services

  - by synergetic

  I use WCF RIA Services to update customer database. In domain service: public void UpdateCustomer(Customer customer) { this.ObjectContext.Customers.AttachAsModified(customer); syncCustomer(customer); } After update, a database trigger launches and depending on the columns updated it may insert a new record in CustomerChange table. syncCustomer(customer) method is executed to check for a new record in the CustomerChange table and if found it will create a text file which contains customer information and forwards that file to external system for import. Now this synchronization may take a time so I wanted to execute it in different thread. So: private void syncCustomer(Customer customer) { this.ObjectContext.SaveChanges(); new Thread(() => syncCustomerInfo(customer.CustomerID)) { IsBackground = true }.Start(); } private void syncCustomerInfo(int customerID) { //Thread.Sleep(2000); //does real job here ... ... } The problem is in most cases syncCustomerInfo method cannot find any new CustomerChange record even if it was definitely there. If I force thread sleep then it finds a new record. I also looked Entity Framework events but the only event provided by object context is SavingChanges which occur before changes are saved. Please suggest me what else to try.

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• Is Stream.Write thread-safe?

  - by Mike Spross

  I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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• How to solve generic algebra using solver/library programmatically? Matlab, Mathematica, Wolfram etc?

  - by DevDevDev

  I'm trying to build an algebra trainer for students. I want to construct a representative problem, define constraints and relationships on the parameters, and then generate a bunch of Latex formatted problems from the representation. As an example: A specific question might be: If y < 0 and (x+3)(y-5) = 0, what is x? Answer (x = -3) I would like to encode this as a Latex formatted problem like. If $y<0$ and $(x+constant_1)(y+constant_2)=0$ what is the value of x? Answer = -constant_1 And plug into my problem solver constant_1 > 0, constant_1 < 60, constant_1 = INTEGER constant_2 < 0, constant_2 > -60, constant_2 = INTEGER Then it will randomly construct me pairs of (constant_1, constant_2) that I can feed into my Latex generator. Obviously this is an extremely simple example with no real "solving" but hopefully it gets the point across. Things I'm looking for ideally in priority order * Solve algebra problems * Definition of relationships relatively straight forward * Rich support for latex formatting (not just writing encoded strings) Thanks!

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• Screen information while Windows system is locked (.NET)

  - by Matt

  We have a nightly process that updates applications on a user's pc, and that requires bringing the application down and back up again (not looking to get into changing that process). The problem is that we are building a Windows AppBar on launch which requires a valid screen, and when the system is locked there isn't one in the Screen class. So none of the visual effects are enabled and it shows up real ugly. The only way we currently have around this is to detect a locked screen and just spin and wait until the user unlocks the desktop, then continue launching. Leaving it down isn't an option, as this is a key part of our user's workflow, and they expect it to be up and running if they left it that way the night before. Any ideas?? I can't seem to find the display information anywhere, but it has to be stored off someplace, since the user is still logged in. The contents of the Screen.AllScreens array: ** When Locked: Device Name : DISPLAY Primary : True Bits Per Pixel : 0 Bounds : {X=-1280,Y=0,Width=2560,Height=1024} Working Area : {X=0,Y=0,Width=1280,Height=1024} ** When Unlocked: Device Name : \\.\DISPLAY1 Primary : True Bits Per Pixel : 32 Bounds : {X=0,Y=0,Width=1280,Height=1024} Working Area : {X=0,Y=0,Width=1280,Height=994} Device Name : \\.\DISPLAY2 Primary : False Bits Per Pixel : 32 Bounds : {X=-1280,Y=0,Width=1280,Height=1024} Working Area : {X=-1280,Y=0,Width=1280,Height=964}

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• Ideal directory structure for web application

  - by rno

  I'm about to create a user based website and will have to store photo, docs and other data for each user. If I take a silly number like 1 000 000 000 users, I believe than one folder with 1 000 000 000 won't be the fastest thing in the world! So I was thinking of creating something like 1st level : [a-z] 2nd level : [a-z] 3rd level : [a-z] Therefor bobby will be in /b/o/b/by But this also mean that it won't be spread equaly, because there will be very few user starting with a z and many more with a m,s,l ... so I was thinking of using a user id such as "000000000001", "000000000001" etc... 1st level : [000-999] 2nd level : [000-999] 3rd level : [000-999] therefore data of the user 000000000001 will be store in /data/000/000/000/001 then I will be sure to have a maximum of 1000 folder in each level. What do you guys think about it, what I should do or not do ? The server will be running Centos 5.4 with EXT3 on raid 1, if the I/O get's too bad i will probably go for a raid 10.

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• Interchange structured data between Haskell and C

  - by Eonil

  First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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• How to get to the key name of a referenced entity property from an entity instance without a datastore read in google app engine?

  - by Sumeet Pareek

  Consider I have the following models - class Team(db.Model): # say I have just 5 teams name = db.StringProperty() class Player(db.Model): # say I have thousands of players name = db.StringProperty() team = db.ReferenceProperty(Team, collection_name="player_set") Key name for each Team entity = 'team_' , and for each Player entity = 'player_' By some prior arrangement I have a Team entity's (key_name, name) mapping available to me. For example (team_01, United States Of America), (team_02, Russia) etc I have to show all the players and their teams on a page. One way of doing this would be - players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(player.team.name) #This is a total of 1x1000 = 1000 DB reads That is a 1001 DB reads for a silly thing. The interesting part is that when I do a db.to_dict() on players, it shows that for every player in that list there is 'name' of the player and there is the 'key_name' of the team available too. So how can I do the below ?? players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(team_list[player.<SOME WAY OF GETTING TEAM KEY NAME>]) # Here 'team_list' already has (key_name, name) for all 5 teams I have been struggling with this for a long time. Have read every available documentation. I could just hug the person that can help me here :-) Disclaimer: The above problem description is not a real scenario. It is a simplified arrangement that represents my problem exactly. I have run into it in a rater complex and big GAE appication.

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• Inconsistent table width when hideing/showing a set of columns

  - by Salman A. Kagzi

  I have got a an HTML table of around 40+ columns. To make this table fit in the screen and have the data in a re presentable format we have section in this table. i.e. there are some column that are always visible and the remainder a made visible when s specific radio button (describing a section) is selected. Each radio button is associated to different number of columns. We show/hide a column by setting/removing "display:none" style in all the cell under that column. This all works Just fine. Now the real problem is with the width of the columns in this table. I cant use fixed with with pixel settings. I have tried using the percentage setting by giving 50% to the always visible part and rest 50% is divided between the column in a section. But I am unable to get a fixed behavior i.e. the size of the table columns across IE & FF. Some columns are just right while some are really huge. How can I get the table to give consistent column width across browsers?

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• not able to run c/cpp execs in eclipse cdt

  - by user1658323

  i installed eclipse and then cdt on an ubuntu system recently and was trying to make the first runnable c/c++ proj.. i installed g++ also, and then created the first executable cpp 'Hello World' project some files are created... then some issues... 1) even though Build Automatically is selected, I have to goto the project n do a Build Project to build it manually, and this i have to do everytime i make a change 2) After Building manually, there are some new folders created with Binaries and Debug files and i can see g++ commands in the console being executed. The project binary is output both to debug n binaries folder. But i am not able to run these through the Green Play Button or any other way in eclipse. Even Run configuration is not showing any option for c/C++ proj.. though i can goto terminal and run the binary myself through ./ But i want to be able to run n debug this through eclipse. plz help in fixing me this problem as i really love eclipse n have some c/cpp assignments coming soon.. Console info on doing a manual project build - Build of configuration Debug for project qwe ** make all Building file: ../src/qwe.cpp Invoking: GCC C++ Compiler g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/qwe.d" -MT"src/qwe.d" -o "src/qwe.o" "../src/qwe.cpp" Finished building: ../src/qwe.cpp Building target: qwe Invoking: GCC C++ Linker g++ -o "qwe" ./src/qwe.o Finished building target: qwe Build Finished **

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• JAX-RS --- How to return JSON and HTTP Status code together?

  - by masato-san

  I'm writing REST web app (Netbean6.9, JAX-RS, Toplink-essential) and trying to return JSON and Http status code. I have code ready and working just to return JSON when HTTP GET Method is called from client. Code snippet @Path("get/id") @GET @Produces("application/json") public M_?? getMachineToUpdate(@PathParam("id") String id) { //some code to return JSON . . return myJson But I also want to return HTTP status code (500, 200, 204 etc) along with returning JSON. I tried using HttpServletResponse object, response.sendError("error message", 500); But this made browser to think it's real 500 so output web page was regular Http 500 error page. What I want to is just to return status code so that my Javascript on client side can handle some logic depending on what HTTP status code is returned. (maybe just to display the error code and message on html page.) Is it possible to do so? or should HTTP status code not be used for such thing?

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• Java object graph -> xml when direction of object association needs to be reversed.

  - by Sigmoidal

  An application I have been working on has objects with a relationship similar to below. In the real application both objects are JPA entities. class Underlying{} class Thing { private Underlying underlying; public Underlying getUnderlying() { return underlying; } public void setUnderlying(final Underlying underlying) { this.underlying = underlying; } } There is a requirement in the application to create xml of the form: <template> <underlying> <thing/> <thing/> <thing/> </underlying> </template> So we have a situation where the object graph expresses the relationship between Thing and Underlying in the opposite direction to how it's expressed in the xml. I expect to use JAXB to create the xml but ideally I don't want to have to create a new object hierarchy to reflect the associations in the xml. Is there any way to create xml of the form required from the entities in their current form (through the use of xml annotations or something)? I don't have any experience using JAXB but from the limited research I've done it doesn't seem like it's possible to reverse the direction of association in any straightforward way. Any help/advice would be greatly appreciated. One other option that has been suggested is to use XLST to transform the xml into the correct format. I have done no research on this topic as yet but I'll add to the question when I have some more info. Thanks, Matt.

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• How to encrypt/decrypt a file in Java?

  - by Petike

  Hello, I am writing a Java application which can "encrypt" and consequently "decrypt" whatever binary file. I am just a beginner in the "cryptography" area so I would like to write a very simple application for the beginning. For reading the original file, I would probably use the java.io.FileInputStream class to get the "array of bytes" byte originalBytes[] of the file. Then I would probably use some very simple cipher, for example "shift up every byte by 1" and then I would get the "encrypted" bytes byte encryptedBytes[] and let's say that I would also set a "password" for it, for example "123456789". Next, when somebody wants to "decrypt" that file, he has to enter the password ("123456789") first and after that the file could be decrypted (thus "shift down every byte by 1") and consequently saved to the output file via java.io.FileOutputStream I am just wondering how to "store" the password information to the encrypted file so that the decrypting application knows if the entered password and the "real" password equals? Probably it would be silly to add the password (for example the ASCII ordinal numbers of the password letters) to the beginning of the file (before the encrypted data). So my main question is how to store the password information to the encrypted file?

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• How to get the most out of a 3 month intern?

  - by firoso

  We've got a software engineering intern coming in who's fairly competent and shows promise. There's one catch: we have him for 3 months full time and can't count on anything past that. He still has a year of school left, which is why we can't say for sure that we have him past 3 months. We have a specific project we're putting him on. How can we maximize his productivity while still giving him a positive learning experience? He wants to learn about development cycles and real-world software engineering. Anything that you think would be critical that you wish you had learned earlier? Nearly six months later: He's preformed admirably and even I have learned a lot from him. Thank you all for the input. Now I want to provide feedback to YOU! He has benefited most from sitting down and writing code. However, he has had a nasty history of bad software engineering practices which I'm trying to replace with good habits (properly finishing a method before moving on, not hacking code together, proper error channeling, etc). He has also really gained a lot by feeling involved in design decisions, even if most of the time they're related to my own design plans.

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• HTML Submit button vs AJAX based Post (ASP.NET MVC)

  - by Graham

  I'm after some design advice. I'm working on an application with a fellow developer. I'm from the Webforms world and he's done a lot with jQuery and AJAX stuff. We're collaborating on a new ASP.MVC 1.0 app. He's done some pretty amazing stuff that I'm just getting my head around, and used some 3rd party tools etc. for datagrids etc. but... He rarely uses Submit buttons whereas I use them most of the time. He uses a button but then attaches Javascript to it that calls an MVC action which returns a JSON object. He then parses the object to update the datagrid. I'm not sure how he deals with server-side validation - I think he adds a message property to the JSON object. A sample scenario would be to "Save" a new record that then gets added to the gridview. The user doesn't see a postback as such, so he uses jQuery to disable the UI whilst the controller action is running. TBH, it looks pretty cool. However, the way I'd do it would be to use a Submit button to postback, let the ModelBinder populate a typed model class, parse that in my controller Action method, update the model (and apply any validation against the model), update it with the new record, then send it back to be rendered by the View. Unlike him, I don't return a JSON object, I let the View (and datagrid) bind to the new model data. Both solutions "work" but we're obviously taking the application down different paths so one of us has to re-work our code... and we don't mind whose has to be done. What I'd prefer though is that we adopt the "industry-standard" way of doing this. I'm unsure as to whether my WebForms background is influencing the fact that his way just "doesn't feel right", in that a "submit" is meant to submit data to the server. Any advice at all please - many thanks.

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• SQL Server Long Query

  - by thormj

  Ok... I don't understand why this query is taking so long (MSSQL Server 2005): [Typical output 3K rows, 5.5 minute execution time] SELECT dbo.Point.PointDriverID, dbo.Point.AssetID, dbo.Point.PointID, dbo.Point.PointTypeID, dbo.Point.PointName, dbo.Point.ForeignID, dbo.Pointtype.TrendInterval, coalesce(dbo.Point.trendpts,5) AS TrendPts, LastTimeStamp = PointDTTM, LastValue=PointValue, Timezone FROM dbo.Point LEFT JOIN dbo.PointType ON dbo.PointType.PointTypeID = dbo.Point.PointTypeID LEFT JOIN dbo.PointData ON dbo.Point.PointID = dbo.PointData.PointID AND PointDTTM = (SELECT Max(PointDTTM) FROM dbo.PointData WHERE PointData.PointID = Point.PointID) LEFT JOIN dbo.SiteAsset ON dbo.SiteAsset.AssetID = dbo.Point.AssetID LEFT JOIN dbo.Site ON dbo.Site.SiteID = dbo.SiteAsset.SiteID WHERE onlinetrended =1 and WantTrend=1 PointData is the biggun, but I thought its definition should allow me to pick up what I want easily enough: CREATE TABLE [dbo].[PointData]( [PointID] [int] NOT NULL, [PointDTTM] [datetime] NOT NULL, [PointValue] [real] NULL, [DataQuality] [tinyint] NULL, CONSTRAINT [PK_PointData_1] PRIMARY KEY CLUSTERED ( [PointID] ASC, [PointDTTM] ASC ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO CREATE NONCLUSTERED INDEX [IX_PointDataDesc] ON [dbo].[PointData] ( [PointID] ASC, [PointDTTM] DESC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] GO PointData is 550M rows, and Point (source of PointID) is only 28K rows. I tried making an Indexed View, but I can't figure out how to get the Last Timestamp/Value out of it in a compatible way (no Max, no subquery, no CTE). This runs twice an hour, and after it runs I put more data into those 3K PointID's that I selected. I thought about creating LastTime/LastValue tables directly into Point, but that seems like the wrong approach. Am I missing something, or should I rebuild something? (I'm also the DBA, but I know very little about A'ing a DB!)

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• Event feed implementation - will it scale?

  - by SlappyTheFish

  Situation: I am currently designing a feed system for a social website whereby each user has a feed of their friends' activities. I have two possible methods how to generate the feeds and I would like to ask which is best in terms of ability to scale. Events from all users are collected in one central database table, event_log. Users are paired as friends in the table friends. The RDBMS we are using is MySQL. Standard method: When a user requests their feed page, the system generates the feed by inner joining event_log with friends. The result is then cached and set to timeout after 5 minutes. Scaling is achieved by varying this timeout. Hypothesised method: A task runs in the background and for each new, unprocessed item in event_log, it creates entries in the database table user_feed pairing that event with all of the users who are friends with the user who initiated the event. One table row pairs one event with one user. The problems with the standard method are well known – what if a lot of people's caches expire at the same time? The solution also does not scale well – the brief is for feeds to update as close to real-time as possible The hypothesised solution in my eyes seems much better; all processing is done offline so no user waits for a page to generate and there are no joins so database tables can be sharded across physical machines. However, if a user has 100,000 friends and creates 20 events in one session, then that results in inserting 2,000,000 rows into the database. Question: The question boils down to two points: Is this worst-case scenario mentioned above problematic, i.e. does table size have an impact on MySQL performance and are there any issues with this mass inserting of data for each event? Is there anything else I have missed?

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• UTF-8 HTML and CSS files with BOM (and how to remove the BOM with Python)

  - by Cameron

  First, some background: I'm developing a web application using Python. All of my (text) files are currently stored in UTF-8 with the BOM. This includes all my HTML templates and CSS files. These resources are stored as binary data (BOM and all) in my DB. When I retrieve the templates from the DB, I decode them using template.decode('utf-8'). When the HTML arrives in the browser, the BOM is present at the beginning of the HTTP response body. This generates a very interesting error in Chrome: Extra <html> encountered. Migrating attributes back to the original <html> element and ignoring the tag. Chrome seems to generate an <html> tag automatically when it sees the BOM and mistakes it for content, making the real <html> tag an error. So, using Python, what is the best way to remove the BOM from my UTF-8 encoded templates (if it exists -- I can't guarantee this in the future)? For other text-based files like CSS, will major browsers correctly interpret (or ignore) the BOM? They are being sent as plain binary data without .decode('utf-8'). Note: I am using Python 2.5. Thanks!

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• Am I going the right way to make login system secure with this simple password salting?

  - by LoVeSmItH

  I have two fields in login table password salt And I have this little function to generate salt function random_salt($h_algo="sha512"){ $salt1=uniqid(rand(),TRUE); $salt2=date("YmdHis").microtime(true); if(function_exists('dechex')){ $salt2=dechex($salt2); } $salt3=$_SERVER['REMOTE_ADDR']; $salt=$salt1.$salt2.$salt3; if(function_exists('hash')){ $hash=(in_array($h_algo,hash_algos()))?$h_algo:"sha512"; $randomsalt=hash($hash,md5($salt)); //returns 128 character long hash if sha512 algorithm is used. }else{ $randomsalt=sha1(md5($salt)); //returns 40 characters long hash } return $randomsalt; } Now to create user password I have following $userinput=$_POST["password"] //don't bother about escaping, i have done it in my real project. $static_salt="THIS-3434-95456-IS-RANDOM-27883478274-SALT"; //some static hard to predict secret salt. $salt=random_salt(); //generates 128 character long hash. $password =sha1($salt.$userinput.$static_salt); $salt is saved in salt field of database and $password is saved in password field. My problem, In function random_salt(), I m having this FEELING that I'm just making things complicated while this may not generate secure salt as it should. Can someone throw me a light whether I m going in a right direction? P.S. I do have an idea about crypt functions and like such. Just want to know is my code okay? Thanks.

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• How to put JFrame into existing JPanel in Java Swing?

  - by suud

  I have an open-source java swing application like this: http://i47.tinypic.com/dff4f7.jpg You can see in the screenshot, there is a JPanel divided into two area, left and right area. The left area has many text links. When I click the SLA Criteria link, it will pop-up the SLA Criteria window. The pop-up window is JFrame object. Now, I'm trying to put the pop-up window into right area of the JPanel, so that means no pop-up window anymore, i.e. when I click the SLA Criteria link, its contents will be displayed at the right area of the JPanel. The existing content of the right area of JPanel will not be used anymore. The example illustration (note: it's made and edited using image editor, this is not the real screenshot of working application) is like this: http://i48.tinypic.com/5vrxaa.jpg So, I would like to know is there a way to put JFrame into JPanel? I'm thinking of using JInternalFrame, is it possible? Or is there another way? UPDATE: Source code: http://pastebin.com/tiqRbWP8 (VTreePanel.java, this is the JPanel) http://pastebin.com/330z3yuT (CPanel.java, this is the super class of VTreePanel) http://pastebin.com/MkNsbtjh (AWindow.java, this is the JFrame, pop-up window) http://pastebin.com/2rsppQeE (CFrame.java, this is the super class of AWindow)

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• How accurately (in terms of time) does Windows play audio?

  - by MusiGenesis

  Let's say I play a stereo WAV file with 317,520,000 samples, which is theoretically 1 hour long. Assuming no interruptions of the playback, will the file finish playing in exactly one hour, or is there some occasional tiny variation in the playback speed such that it would be slightly more or slightly less (by some number of milliseconds) than one hour? I am trying to synchronize animation with audio, and I am using a System.Diagnostics.Stopwatch to keep the frames matching the audio. But if the playback speed of WAV audio in Windows can vary slightly over time, then the audio will drift out of sync with the Stopwatch-driven animation. Which leads to a second question: it appears that a Stopwatch - while highly granular and accurate for short durations - runs slightly fast. On my laptop, a Stopwatch run for exactly 24 hours (as measured by the computer's system time and a real stopwatch) shows an elapsed time of 24 hours plus about 5 seconds (not milliseconds). Is this a known problem with Stopwatch? (A related question would be "am I crazy?", but you can try it for yourself.) Given its usage as a diagnostics tool, I can see where a discrepancy like this would only show up when measuring long durations, for which most people would use something other than a Stopwatch. If I'm really lucky, then both Stopwatch and audio playback are driven by the same underlying mechanism, and thus will stay in sync with each other for days on end. Any chance this is true?

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• How to build a simulation of a login hardware token in .Net

  - by Michel

  Hi, i have a hardware token for remote login to some citrix environment. When i click the button on the device, i get an id and i can use that to login to the citrix farm. I can click the button as much as i like, and every time a new code gets generated, and they all work. Now i want to secure my private website likewise, but not with the hardware token, but with a 'token app' on my phone. So i run an app on my phone, generate a key, and use that to (partly) authenticate myself on the server. But here's the point: i don't know how it works! How can i generate 1, 2 or 100 keys at one time which i can see (on the server) are all valid, but without the server and the phone app having contact (the hardware token also is an 'offline' solution). Can you help me with a hint how i would do this? This is what i thought of so far: the phone app and the server app know (hardcoded) the same encryption key. The phone app encrypts the current time. The server app decrypts the string to the current time and if the diff between that time and the actual server time is less than 10 minutes it's an ok. Difficult for other users to fake a key, but encryption gives such nasty strings to enter, and the hardware token gives me nice things like 'H554TU8' And this is probably not how the real hardware token works, because the server and the phone app must 'know' the same encryption key. Michel

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