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Articles indexed in April 2010

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  • Faster projected-norm (quadratic-form, metric-matrix...) style computations

    - by thekindamzkyoulike
    I need to perform lots of evaluations of the form X(:,i)' * A * X(:,i) i = 1...n where X(:,i) is a vector and A is a symmetric matrix. Ostensibly, I can either do this in a loop for i=1:n z(i) = X(:,i)' * A * X(:,i) end which is slow, or vectorise it as z = diag(X' * A * X) which wastes RAM unacceptably when X has a lot of columns. Currently I am compromising on Y = A * X for i=1:n z(i) = Y(:,i)' * X(:,i) end which is a little faster/lighter but still seems unsatisfactory. I was hoping there might be some matlab/scilab idiom or trick to achieve this result more efficiently?

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  • Django: FloatField or DecimalFied for Currency ?

    - by Hellnar
    I am curious which one would be better fitting as a currency field ? I will do simple operations such as taking difference, the percentage between old and new prices. I plan to keep two digits after the zero (ie 10.50) and majority of the time if these digits are zero, I will be hiding these numbers and display it as "10"

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  • Convert a List of Options to an Option of List using Scalaz

    - by Rafael de F. Ferreira
    The following function transforms a list of Option[T] into a list of Some[T], in the case where all members are Some's, or None, in the case where there is at least one None member. I guess the code is clearer that this explanation: def lo2ol[T](lo: List[Option[T]]): Option[List[T]] = { lo.foldRight[Option[List[T]]](Some(Nil)){(o, ol) => (o, ol) match { case (Some(x), Some(xs)) => Some(x :: xs); case _ => None : Option[List[T]]; }}} I remember seeing somewhere a similar example, but using Scalaz to simplify the code. How would it look like?

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  • WCF Operation contract availability

    - by nettguy
    This question was asked at interview. Say I have a contract. [ServiceContract] public interface IMyService { [OperationContract] void methodForClientA(); [OperationContract] void AnothermethodForClientA(); [OperationContract] void methodForClientB(); [OperationContract] void AnothermethodForClientB(); } When a clientA access the contract it should only see the operation contracts void methodForClientA(),void AnothermethodForClientA(). Is it possible in WCF ?

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  • Mean filter in MATLAB without loops or signal processing toolbox

    - by Doresoom
    I need to implement a mean filter on a data set, but I don't have access to the signal processing toolbox. Is there a way to do this without using a for loop? Here's the code I've got working: x=0:.1:10*pi; noise=0.5*(rand(1,length(x))-0.5); y=sin(x)+noise; %generate noisy signal a=10; %specify moving window size my=zeros(1,length(y)-a); for n=a/2+1:length(y)-a/2 my(n-a/2)=mean(y(n-a/2:n+a/2)); %calculate mean for each window end mx=x(a/2+1:end-a/2); %truncate x array to match plot(x,y) hold on plot(mx,my,'r')

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  • Using Excel to work with SQL data (read/write)

    - by Tyler Brock
    I have a ton of data in a sql database which I would like to be able to import and display in excel (I can already do this) and additionally modify or append to the dataset within excel and write the changes/additions back to the database. What is the best way to go about doing something like this? Please let me know, thanks!

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  • Random DNS Client Issue with BIND9/Windows Server 2003 DNS

    - by upkels
    Within our office, we have a local server running DNS, for internal related "domains", (e.g. .internal, .office, .lan, .vpn, etc.). Randomly, only the hosts configured with those extensions will stop resolving on the Windows-based workstations. Sometimes it'll work for a couple weeks without issue on one machine, then suddenly stop working, or it'll happen on another 15 times per day. It's completely random for all workstations. When troubleshooting, I have opened up a command prompt, and issued various nslookup commands for some of these hosts, and they resolve, however I've been told that nslookup uses different "libraries" for name resolution than other applications such as web browsers, email clients, etc. The only solution thus far, is manually restarting the Windows DNS Client on each workstation when this happens. Issuing the ipconfig /flushdns command multiple times helps every now and then, but is not successful enough to even attempt before restarting the DNS Client. I have tried two different DNS servers; BIND9, and Windows Server 2003 R2 DNS, and the behavior is the same. We have a single Netgear JGS524 switch all workstations and servers are connected to within the office, and a Linksys SR224G switch in another department with workstations attached.

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  • How can I detect if the browser has encountered a JavaScript error ... in JavaScript?

    - by RichH
    For automated testing reasons I want to detect if the browser has encountered JavaScript errors for a page. The type of things that would cause the red numbers in the bottom right in Firebug or yellow warning icon in the Internet Explorer status bar. These JS errors could come from any one of a large numbers of scripts. How in JavaScript can I detect these browser errors? Cross browser solutions prefered, but hey, I'll take anything! As a bonus it would also be great to know the script that caused the error.

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  • Best editor for CodeIgniter?

    - by Rismo
    I'm learning CodeIgniter and I come from Microsoft Visual Studio so I'm used to the auto complete feature. I've been using notepad++ so far but I wonder if anyone knows an editor that works better with CodeIgniter. I would love to see features like: Right-click - Add new model Right-click - Add new view Autocomplete with CodeIgniter helpers and libraries

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  • SharePoint threw "Unknown SQL Exception 206 occured." Anyone familiar with this?

    - by dalehhirt
    Our SharePoint instance threw the following errors when attempting to access data through a Content Query Tool: 04/02/2010 10:45:06.12 w3wp.exe (0x062C) 0x1734 Windows SharePoint Services Database 5586 Critical Unknown SQL Exception 206 occured. Additional error information from SQL Server is included below. Operand type clash: uniqueidentifier is incompatible with datetime 04/02/2010 10:45:06.25 w3wp.exe (0x062C) 0x1734 Office Server Office Server General 900n Critical A runtime exception was detected. Details follow. Message: Operand type clash: uniqueidentifier is incompatible with datetime Techinal Details: System.Data.SqlClient.SqlException: Operand type clash: uniqueidentifier is incompatible with datetime at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.ConsumeMetaData(... 04/02/2010 10:45:06.25* w3wp.exe (0x062C) 0x1734 Office Server Office Server General 900n Critical ...) at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlC 04/02/2010 10:45:06.25 w3wp.exe (0x062C) 0x1734 CMS Publishing 8vyd Exception (Watson Reporting Cancelled) System.Data.SqlClient.SqlException: Operand type clash: uniqueidentifier is incompatible with datetime at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.ConsumeMetaData() at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteRead... 04/02/2010 10:45:06.25* w3wp.exe (0x062C) 0x1734 CMS Publishing 8vyd Exception ...er(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior) at Microsoft.SharePoint.Utilities.SqlSession.ExecuteReader(SqlCommand command, ... 04/02/2010 10:45:06.25* w3wp.exe (0x062C) 0x1734 CMS Publishing 8vyd Exception ...CommandBehavior behavior) at Microsoft.SharePoint.SPSqlClient.ExecuteQuery(Boolean& bSucceed) at Microsoft.SharePoint.Library.SPRequestInternalClass.CrossListQuery(String bstrUrl, String bstrXmlWebs, String bstrXmlLists, String bstrXmlQuery, ISP2DSafeArrayWriter pCallback, Object& pvarColumns) at Microsoft.SharePoint.Library.SPRequest.CrossListQuery(String bstrUrl, String bstrXmlWebs, String bstrXmlLists, String bstrXmlQuery, ISP2DSafeArrayWriter pCallback, Object& pvarColumns) at Microsoft.SharePoint.SPWeb.GetSiteData(SPSiteDataQuery query) at Microsoft.SharePoint.Publishing.CachedArea.GetCrossListQuery(SPSiteDataQuery query, SPWeb currentContext) at Microsoft.SharePoint.Publishing.CrossListQueryCache.GetSiteData(CachedArea cachedArea, SPWeb web, SPSiteDataQuery qu... 04/02/2010 10:45:06.25* w3wp.exe (0x062C) 0x1734 CMS Publishing 8vyd Exception ...ery) 04/02/2010 10:45:06.25 w3wp.exe (0x062C) 0x1734 CMS Publishing 78ed Warning Error occured while processing a Content Query Web Part. Performing the following query ' 04/02/2010 10:45:06.25* w3wp.exe (0x062C) 0x1734 CMS Publishing 78ed Warning ...ue" Type="Number"/ The farm is MOSS 2007 with SQL Server 2005 backend. Any ideas are welcomed. Dale

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  • SPF records - what are the differences ?

    - by progeny
    I'm trying to set up an SPF record for my domain. I've read the RFC, been to Wikipedia, openspf.org, etc. but I'm still confused. What is the difference between 'a' and 'mx'? When do I use 'mx: rather than 'a:' or 'include:'? What's the point of '?all' (Neutral result) except for debugging? Why do so many people use '~all' (Softfail) instead of '-all' ? I've been to the Wizard (http://old.openspf.org/wizard.html) but I don't understand the questions.

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  • Google Page Rank - The Ultimate Popularity Contest

    Although you might initially think of it as simply the way that the Google search engine ranks pages, the term Google Page Rank is actually a trademarked term that actually belongs to Stanford University. The term is a tribute to its creator, Larry Page, and refers to a complex mathematics algorithm that allows today's advanced search engines, like Google, to index and rank the millions and millions of pages that exist on the internet today.

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  • In-House Or Outsource SEO Work?

    Today, having top page rank and excellent website traffic is the primary focus of business owners. Businesses trying to get a better rank of the search engines are always asking themselves one question; should they out-source their SEO work to an industry professional or should they hire an in-house SEO team?

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  • Five Effective Ways Where a Website Can Help Your Business to Grow and Expand

    The internet has brought significant changes to our ways of living, communication, marketing, and in ways of doing business today. There are major enhancements which we have been enjoying since the emergence of Internet where increase in speed and efficiency, cost saving, existence of virtual office and online courses are some of the major changes we have had over the last 20-30 years.

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  • Register for a free Web Camp: Learn and Build on the Microsoft Web Platform

    Interested in learning how new innovations in Microsoft's Web Platform and developer tools like ASP.NET 4 and Visual Studio 2010 can make you a more productive web developer? If you're currently working with PHP, Ruby, ASP or older versions of ASP.NET and want to hear how you can create amazing websites more easily, then register for a Web Camp near you today!

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  • How to post something to Facebook from Android?

    - by Nicholas Key
    Hi stackoverflow'ers, Quick questions here: What are the necessary tools/APIs to post something from Android to Facebook? I looked at this URL http://wiki.developers.facebook.com/index.php/User%3AAndroid and it mentioned a few suggestions. Have anyone tried fbrocket? What is Facebook Connect anyway? Thanks! Nicholas

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  • Online voice chat: Why client-server model vs. peer-to-peer model?

    - by sstallings
    I am adding online voice chat to a Silverlight app. I've been reviewing current apps, services and SDKs found thru online searches and forums. I'm finding that the majority of these implement a client-server (C/S) model and I'm trying to understand why that model versus a peer-to-peer (PTP) model. To me PTP would be preferable because going direct between peers would be more efficient (fewer IP hops and no processing along the way by a server computer) and no need for a server and its costs and dependencies. I found some products offer the ability to switch from PTP to C/S if the PTP proves insufficient. As I thought more about it, I could see that C/S could be better if there are more than two peers involved in a conversation, then the server (supposedly with more bandwidth) could do a better job of relaying each peers outgoing traffic to the multiple other peers. In C/S many-to-many voice chatting, each peer's upstream broadband (which is where the bottleneck inherently is) would only have to carry each item of voice traffic once, then the server would use its superior bandwidth to relay the message to the multiple other peers. But, in a situation with one-on-one voice chatting it seems that PTP would be best. A server would not reduce each of the two peer's bandwidth requirements and would only add unnecessary overhead, dependency and cost. In one-on-one voice chatting: Am I mistaken on anything above? Would peer-to-peer be best? Would a server provide anything of value that could not be provided by a client-only program? Is there anything else that I should be taking into consideration? And lastly, can you recommend any Silverlight PTP or C/S voice chat products? Thanks in advance for any info.

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  • How do I delete a [sub]hash based off of the keys/values of another hash?

    - by Zack
    Lets assume I have two hashes. One of them contains a set of data that only needs to keep things that show up in the other hash. e.g. my %hash1 = ( test1 => { inner1 => { more => "alpha", evenmore => "beta" } }, test2 => { inner2 => { more => "charlie", somethingelse => "delta" } }, test3 => { inner9999 => { ohlookmore => "golf", somethingelse => "foxtrot" } } ); my %hash2 = ( major=> { test2 => "inner2", test3 => "inner3" } ); What I would like to do, is to delete the whole subhash in hash1 if it does not exist as a key/value in hash2{major}, preferably without modules. The information contained in "innerX" does not matter, it merely must be left alone (unless the subhash is to be deleted then it can go away). In the example above after this operation is preformed hash1 would look like: my %hash1 = ( test2 => { inner2 => { more => "charlie", somethingelse => "delta" } }, ); It deletes hash1{test1} and hash1{test3} because they don't match anything in hash2. Here's what I've currently tried, but it doesn't work. Nor is it probably the safest thing to do since I'm looping over the hash while trying to delete from it. However I'm deleting at the each which should be okay? This was my attempt at doing this, however perl complains about: Can't use string ("inner1") as a HASH ref while "strict refs" in use at while(my ($test, $inner) = each %hash1) { if(exists $hash2{major}{$test}{$inner}) { print "$test($inner) is in exists.\n"; } else { print "Looks like $test($inner) does not exist, REMOVING.\n"; #not to sure if $inner is needed to remove the whole entry delete ($hash1{$test}{$inner}); } }

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  • Is there a way to validates_presence_of only one time? (to skip that validation once the user's been

    - by GoodGets
    So, I'd like for a user to see an error message if he submits a comment and the :name is blank (typical error message, don't need help with that). However, I'd then like to allow the user to skip that validation once he's been notified that "we like all comments to have a name." So, he submits the comment once, sees the notification, then can submit the form again unchanged if he really doesn't want to add a name, and the validates_presences_of :name is skipped. But, I'm not sure how to go about doing this. I thought about checking to see where the request is coming from, but after a create, errors are handed off to the "new" action, which is the same as actual "new" comments. I then thought about checking to see if flash[errors] were present, but that won't work because there are other validations a comment has to pass. Finally, I thought about trying a validates_presences_of :name, :unless = :notified but wasn't sure how to define notified. I honestly hate asking such an open ended question, but wasn't sure where to get started. So, is there a way to just check a certain validation once?

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  • To store images in SQL or not?

    - by Brett
    Generally, I had thought it was always better to store images in the filesystem and link to it via the database entry. However, I am trying to optimize my db design and am having a few questions. My images are all really small thumbmails in black and white (not greyscale, but true B&W) and are 70x70 in size. If we take the images (which is basically a 2D array of 1 and 0), it can be stored as binary data that would be approximately 600 bytes each. So my question is whether querying the 600 bytes stored in a db would be faster than querying a link followed by accessing the filesystem; assuming there are a lot of "image" queries being made. Does anyone have any experience with this area? If it matters, I am using MySQL, and MonetDB (separately, but have the same question for both). Many thanks, Brett

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