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• C++ Multithreaded server help

  - by kisplit

  Hello all, I'm working on a multithreaded server in c++ using boost-asio. Currently a design problem I'm running into deals with erasing a connection. I have a single server instance which holds a vector of connection objects. These connections receive commands which I parse. One command in particular deals with sending data to ALL connections in my vector. Now when a connection disconnects I'm currently erasing this connection from the vector and calling the destructor. It seems like I'm going to run into problems when someone 'SendAll' at the same time someone 'Disconnect'. Could anyone recommend a better design or just point me in the right direction? Any help greatly appreciated. Thanks

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• Looking for a clear and concise web page explaining why lower bits of random numbers are usually not

  - by Hamish Grubijan

  I am putting together an internal "every developer should know" wiki page. I saw many discussions regarding rand() % N, but not a single web page that explains it all. For instance, I am curious if this problem is only C- and Linux-specific, or if it also applies to Windows, C++,. Java, .Net, Python, Perl. Please help me get to the bottom of this. Also, just how non-random do the numbers get? Thank you!

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• What's the best way to implement one-dimensional collision detection?

  - by cyclotis04

  I'm writing a piece of simulation software, and need an efficient way to test for collisions along a line. The simulation is of a train crossing several switches on a track. When a wheel comes within N inches of the switch, the switch turns on, then turns off when the wheel leaves. Since all wheels are the same size, and all switches are the same size, I can represent them as a single coordinate X along the track. Switch distances and wheel distances don't change in relation to each other, once set. This is a fairly trivial problem when done through brute force by placing the X coordinates in lists, and traversing them, but I need a way to do so efficiently, because it needs to be extremely accurate, even when the train is moving at high speeds. There's a ton of tutorials on 2D collision detection, but I'm not sure the best way to go about this unique 1D scenario.

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• python: naming a module that has a two-word name

  - by Jason S

  I'm trying to put together a really simple module with one .py source file in it, and have already run into a roadblock. I was going to call it scons-config but import scons-config doesn't work in Python. I found this SO question and looked at PEP8 style guide but am kind of bewildered, it doesn't talk about two-word-name conventions. What's the right way to deal with this? module name: SconsConfig? scons_config? sconsconfig? scons.config? name of the single .py file in it: scons-config.py? scons_config.py?

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• How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

  - by Blankman

  I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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• Data Grid Shows extra column

  - by cre-johnny07

  I have a wpf data Grid where I created twlo columns. But whenever I run the window the datagrid shows a extra column. I can't figure out why.? Below is my code <Custom:DataGrid Background="White" AlternatingRowBackground="#103D7EC5" RowHeaderWidth="20" SelectionMode="Single" SelectionUnit="FullRow" GridLinesVisibility="None" MinRowHeight="30" EnableRowVirtualization="True" EnableColumnVirtualization="True" CanUserAddRows="False" CanUserSortColumns="True" AreRowDetailsFrozen="True" RowDetailsVisibilityMode="Collapsed" ItemsSource="{Binding CurrentEntity.RefDetails, Mode = TwoWay}" AutoGenerateColumns="False" Name="grdDoctor1" ScrollViewer.VerticalScrollBarVisibility="Auto" MaxHeight="200"> <Custom:DataGrid.RowDetailsTemplate> <DataTemplate> </DataTemplate> </Custom:DataGrid.RowDetailsTemplate> <Custom:DataGrid.Columns> <Custom:DataGridTextColumn Binding="{Binding DepId}" Width="100" IsReadOnly="True" Header="Id"/> <Custom:DataGridTextColumn Binding="{Binding DepData}" Width="100" IsReadOnly="False" Header="Data"/> </Custom:DataGrid.Columns> </Custom:DataGrid> Any suggestion why this is happening..?

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• How can I prevent ADO from creating multiple SPIDs?

  - by stusmith

  I'm working on an application that creates a single ADO connection and keeps it open for the lifetime of the application. I have connection pooling turned off. (Please ignore the fact that this might not be best practice for the purposes of this question). If I spawn a new thread and use the exact same ADO connection, it uses a new SPID behind the scenes. Is there anyway to ensure an ADO connection always uses the same SPID, across all threads? (For reference the application is VC++ using ADO via COM to SQL Server).

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• Singletons vs. Application Context in Android?

  - by mschonaker

  Recalling this post enumerating several problems of using singletons and having seen several examples of Android applications using singleton pattern, I wonder if it's a good idea to use Singletons instead of single instances shared through global application state (subclassing android.os.Application and obtaining it through context.getApplication()). What advantages/drawbacks would have both mechanisms? To be honest, I expect the same answer in this post http://stackoverflow.com/questions/2709071/singleton-pattern-with-web-application-not-a-good-idea but applied to Android. Am I correct? What's different in DalvikVM otherwise? EDIT: I would like to have opinions on several aspects involved: Synchronization Reusability Testing Thanks in advance.

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• Understanding the concept of Inodes

  - by darkie15

  Hi All, I am referring to the link: http://www.tux4u.nl/freedocs/unix/draw/inode.pdf I am confused on parts: 1 12 direct block pointers 2 1 single indirect block pointer 3 1 double indirect block pointer 4 1 triple indirect block pointer Now the diagram says that each pointer is 32/64 bits. [Query]: Why and how are these values inferred? I mean why specifically have only 32 or 64 bit pointers? The diagram says, One data block{8 KB} for each pointer {4 bytes/8 bytes} [Query]: How does this actually work out? i.e. 8*1024 bytes / 8 bytes = 1024 bytes? What is the logic behind having a 8 bytes pointer for 8KB block? Regards, darkie.

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• How to store Hierarchical K-Means tree for a large number of images, using Opencv?

  - by AquaAsh

  I am trying to make a program that will find similar images from a dataset of images. The steps are 1)extract SURF descriptors for all images 2)store the descriptors 3)Apply knn on the stored descriptors 4)Match the stored descriptors to the query image descriptor using KNN Now each images SURF descriptor will be stored as Hierarchical k means tree, now do I store each tree as a separate file or is it possible to build some sort of single tree with all the images descriptors and updated as images are added to dataset. This is the paper I am basing the program on www.ijest.info/docs/IJEST10-02-03-13.pdf.

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• Getting highest results in a JOIN

  - by Keithamus

  I've got three tables; Auctions, Auction Bids and Users. The table structure looks something like this: Auctions: id title -- ----- 1 Auction 1 2 Auction 2 Auction Bids: id user_id auction_id bid_amt -- ------- ---------- ------- 1 1 1 200.00 2 2 1 202.00 3 1 2 100.00 Users is just a standard table, with id and user name. My aim is to join these tables so I can get the highest values of these bids, as well as get the usernames related to those bids; so I have a result set like so: auction_id auction_title auctionbid_amt user_username ---------- ------------- -------------- ------------- 1 Auction 1 202.00 Bidder2 2 Auction 2 100.00 Bidder1 So far my query is as follows: SELECT a.id, a.title, ab.bid_points, u.display_name FROM auction a LEFT JOIN auctionbid ab ON a.id = ab.auction_id LEFT JOIN users u ON u.id = ab.user_id GROUP BY a.id This gets the single rows I am after, but it seems to display the lowest bid_amt, not the highest.

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• Using excel, how can I count the number of cells in a column containing the text "true" or "false"?

  - by Jay Elston

  I have a spreadsheet that has a column of cells where each cell contains a single work. I would like to count the occurrences of some words. I can use the COUNTIF function for most words, but if the word is "true" or "false", I get 0. A B 1 apples 2 2 true 0 3 false 0 4 oranges 1 5 apples In the above spreadsheet table, I have these formulas in cells B1, B2, B3 and B4: =COUNTIF(A1:A5,"apples") =COUNTIF(A1:A5,"true") =COUNTIF(A1:A5,"false") =COUNTIF(A1:A5,"oranges) As you can see, I can count apples, but not true or false. I have also tried this: =COUNTIF(A1:A5,TRUE) But that does not work either. Note -- I am using Excel 2007.

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• how to combine changes tracked from several documents

  - by Jessica

  I tried to search the solution in internet, but found nothing, is there anyone who can help me? For my application, there is one document (Microsoft word), and this document is reviewed by several people in the "Track changes" mode, so the input to my application is the original document and the reviewed documents with changes (like insert/delete/comments). By this link , I know how to extract all the changes from the reviewed documents. what i want is to combine all the changes from all the reviewed documents into ONE document, and make all the changes "accepted", so the output of my application is one modified Microsoft document with all the changes (delete/insert/comment) accepted. My problem is that I don't know how to combine the changes from several documents into one single document. Anyone has an idea how to do this? Thank you very much in advance.

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• Database normalization and duplicate values

  - by bretddog

  Consider a Parent / Child / GrandChild structure in a database table schema, or even a deeper hierarchy. These being in the same aggregate. One table DAYS keeps a single row per day, and has a "Date" field. This is the root table, or maybe a child of the root. No row can ever be deleted in this table. In this case, however complex my table schema looks like, however far away in the hierarchy any other table is, is there any reason why any other table would hold a Date value? Can't it instead just have a FK to the DAYS table. I obviously assume that the creation of these date fields happen not before such datefield exist in the DAYS table. I'm now thinking just about the date part to be relevant, not the time part. Not sure if all databases can store these individually. That's maybe relevant, but not really the focus of the question.

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• Can I compose a WCF callback contract out of multiple interfaces?

  - by mafutrct

  Followup question to http://stackoverflow.com/questions/2502930/how-can-i-compose-a-wcf-contract-out-of-multiple-interfaces. I tried to merge multiple callback interfaces in a single interface. This yields an InvalidOperationException claiming that the final interface contains no operations. Technically, this is true, however, the inherited interfaces do contain operations. How can I fix this? Or is this a limitation of WCF? Edit: interface A { [OperationContract]void X(); } interface B { [OperationContract]void Y(); } interface C: A, B {} // this is the public callback contract

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• jQuery: use filter(), but work with both results

  - by Tomalak

  In jQuery, filter() reduces your result to those elements that fulfill a certain condition. This splits the list in two parts. Working with the "good half" of the elements is easy: $("some selector").filter(function() { // determine result... return result; }).each( /* do something */ ); But how can I work with the "other half" of my elements, too - but without doing the equivalent of this: $("some selector").filter(function() { // determine result... return !result; }).each( /* do something */ ); Basically, I'd like to feed two separate /* do something */ parts to a single filter. One for those that match, and one for the others - without having to select and filter twice.

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• SELECT..CASE - Refactor T-SQL

  - by Nev_Rahd

  Hello Can I refactor the below SQL CASE statements into single for each case ? SELECT CASE RDV.DOMAIN_CODE WHEN 'L' THEN CN.FAMILY_NAME ELSE NULL END AS [LEGAL_FAMILY_NAME], CASE RDV.DOMAIN_CODE WHEN 'L' THEN CN.GIVEN_NAME ELSE NULL END AS [LEGAL_GIVEN_NAME], CASE RDV.DOMAIN_CODE WHEN 'L' THEN CN.MIDDLE_NAMES ELSE NULL END AS [LEGAL_MIDDLE_NAMES], CASE RDV.DOMAIN_CODE WHEN 'L' THEN CN.NAME_TITLE ELSE NULL END AS [LEGAL_NAME_TITLE], CASE RDV.DOMAIN_CODE WHEN 'P' THEN CN.FAMILY_NAME ELSE NULL END AS [PREFERRED_FAMILY_NAME], CASE RDV.DOMAIN_CODE WHEN 'P' THEN CN.GIVEN_NAME ELSE NULL END AS [PREFERRED_GIVEN_NAME], CASE RDV.DOMAIN_CODE WHEN 'P' THEN CN.MIDDLE_NAMES ELSE NULL END AS [PREFERRED_MIDDLE_NAMES], CASE RDV.DOMAIN_CODE WHEN 'P' THEN CN.NAME_TITLE ELSE NULL END AS [PREFERRED_NAME_TITLE] FROM dbo.CLIENT_NAME CN JOIN dbo.REFERENCE_DOMAIN_VALUE RDV ON CN.NAME_TYPE_CODE = RDV.DOMAIN_CODE AND RDV.REFERENCE_DOMAIN_ID = '7966'

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• What's the best way to test SQL Server connection programmatically?

  - by backslash17

  I need to develop a single routine that will be fired each 5 minutes to check if a list of SQL Servers (10 to 12) are up and running. I can try to obtain a simple query in each one of the servers but this means that I have to create a table, view or stored procedure in every server, even if I use any already made SP I need to have a registered user in each server too. The servers are not in the same physical location so having those requirements would be a complex task. Is there a way to simply "ping" from C# one SQL Server? Thanks in advance!

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• Is this a possible way to get Drupal AD SSO?

  - by JollyRogers

  I'm currently building a Drupal website in an Active Directory environment. One of the site's requirements is Single Sign On, which to date seems to be impossible because there is no Kerberos SPNEGO/GSSAPI auth module for drupal. I've come up with an idea on how SSO could be attempted on IIS. Since IIS has the option to require Kerberos authentication, we can let IIS handle authentication and use the AUTH_USER server variable to pass the authorized user name to the an 'improved' LDAP_auth module. The LDAP_auth module would then check the user name (but not password since it doesn't know or need to know the password) against LDAP to get the user's roles. (AD groups) Does anyone know if this is possible? If so, does anyone have any ideas on how to implement this?

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• What is the best way to find the digit at n position in a decimal number?

  - by Elijah

  Background I'm working on a symmetric rounding class and I find that I'm stuck with regards to how to best find the number at position x that I will be rounding. I'm sure there is an efficient mathematical way to find the single digit and return it without having to resort to string parsing. Problem Suppose, I have the following (C#) psuedo-code: var position = 3; var value = 102.43587m; // I want this no ? (that is 5) protected static int FindNDigit(decimal value, int position) { // This snippet is what I am searching for } Also, it is worth noting that if my value is a whole number, I will need to return a zero for the result of FindNDigit. Does anyone have any hints on how I should approach this problem? Is this something that is blaringly obvious that I'm missing?

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• How can I avoid setting some columns if others haven't changed, when working with Linq To SQL?

  - by Patrick Szalapski

  In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single() row.Name = "Example" ' line 3 dataContext.SubmitChanges() ' line 4 Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query only when necessary--that is, no SQL will be generated if the customer's name was already "Example". So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?

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• Problem loading js content with ajax

  - by Justin Goodman

  I have a page that loads content into a single div via a script in the page. It works fine but the problem is that I have a lightbox in one of the dynamically loaded pages that only works the first time you navigate to it (the script I got for the page loading is found here). Once you navigate to another area, then back again, the lightbox fails to work and instead just loads the plain image. It's been suggested that the easiest way to fix this would be to have a script unload the js and css that is loaded in with the page, then reload it when you go back to the gallery section. I'm a designer, not a developer though, so I don't know if this is true or not. Any help is really appreciated. The page can be found here: justgooddesign.net/graduation/

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• Versioned cloud-based social code snippet management

  - by Chapso

  It seems a lot to ask, but I'm looking for a cloud-based solution to managing code snippets. I am looking for: Tags User accounts (I want to be able to see all of my snippets on a single page) syntax highlighting versioning - myself or others should be able to edit my snippets to improve them\ straightforward UI with minimal advertising if any Does anyone know of a solution which meets these requirements? If not, would anyone be interested in something like this? As a software engineer, after step zero (does it already exist), I'm perfectly willing to go onto step 1 (would other people use it? If so, make it).

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• "Access violation reading location" troubles retrieveing buffer from directx

  - by numerical25

  Below is my code... ID3D10Texture2D *pBackBuffer; hr = mpSwapChain->GetBuffer(0, __uuidof(ID3D10Texture2D), (LPVOID*) &pBackBuffer); and I get the following error chp1.exe': Unloaded 'C:\Windows\SysWOW64\oleaut32.dll' First-chance exception at 0x757ce124 in chp1.exe: Microsoft C++ exception: _com_error at memory location 0x0018eeb0.. First-chance exception at 0x757ce124 in chp1.exe: Microsoft C++ exception: _com_error at memory location 0x0018edd0.. First-chance exception at 0x757ce124 in chp1.exe: Microsoft C++ exception: _com_error at memory location 0x0018ef1c.. The thread 'Win32 Thread' (0xfc4) has exited with code 0 (0x0). 'chp1.exe': Unloaded 'C:\Windows\SysWOW64\D3D10Ref.DLL' First-chance exception at 0x00b71894 in chp1.exe: 0xC0000005: Access violation reading location 0x00000000. Unhandled ex ception at 0x00b71894 in chp1.exe: 0xC0000005: Access violation reading location 0x00000000. It appears that the error occurs in the last parameter. &pBackBuffer. I added this single line of code and the error occurs.

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• how to write T-SQL to compare and copy data?

  - by George2

  Hello everyone, I have two SQL Server 2008 Enterprise databases (on two machines), and one of the databases is master database and another database is slave database. I want to transfer update from a table in source database to a table in destination database (two tables are of the same schema, both of them are using a single column as unique primary key). The transfer rule is (in short, the rule is keeping the destination database the same as source database because of the update of the source database), if there is a new row in source database but not in destination database, insert the row in destination database; if a row not exists in source database but exists in destination database, delete the row in destination database; if a row's content (i.e. columns other than primary key columns) changes in source database, update the new content into destination database. thanks in advance, George

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