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  • CPU friendly infinite loop

    - by Adi
    Writing an infinite loop is simple: while(true){ //add whatever break condition here } But this will trash the CPU performance. This execution thread will take as much as possible from CPU's power. What is the best way to lower the impact on CPU? Adding some Thread.Sleep(n) should do the trick, but setting a high timeout value for Sleep() method may indicate an unresponsive application to the operating system. Let's say I need to perform a task each minute or so in a console app. I need to keep Main() running in an "infinite loop" while a timer will fire the event that will do the job. I would like to keep Main() with the lowest impact on CPU. What methods do you suggest. Sleep() can be ok, but as I already mentioned, this might indicate an unresponsive thread to the operating system. LATER EDIT: I want to explain better what I am looking for: I need a console app not Windows service. Console apps can simulate the Windows services on Windows Mobile 6.x systems with Compact Framework. I need a way to keep the app alive as long as the Windows Mobile device is running. We all know that the console app runs as long as its static Main() function runs, so I need a way to prevent Main() function exit. In special situations (like: updating the app), I need to request the app to stop, so I need to infinitely loop and test for some exit condition. For example, this is why Console.ReadLine() is no use for me. There is no exit condition check. Regarding the above, I still want Main() function as resource friendly as possible. Let asside the fingerprint of the function that checks for the exit condition.

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  • Why does my ActivePerl program report 'Sorry. Ran out of threads'?

    - by Zaid
    Tom Christiansen's example code (à la perlthrtut) is a recursive, threaded implementation of finding and printing all prime numbers between 3 and 1000. Below is a mildly adapted version of the script #!/usr/bin/perl # adapted from prime-pthread, courtesy of Tom Christiansen use strict; use warnings; use threads; use Thread::Queue; sub check_prime { my ($upstream,$cur_prime) = @_; my $child; my $downstream = Thread::Queue->new; while (my $num = $upstream->dequeue) { next unless ($num % $cur_prime); if ($child) { $downstream->enqueue($num); } else { $child = threads->create(\&check_prime, $downstream, $num); if ($child) { print "This is thread ",$child->tid,". Found prime: $num\n"; } else { warn "Sorry. Ran out of threads.\n"; last; } } } if ($child) { $downstream->enqueue(undef); $child->join; } } my $stream = Thread::Queue->new(3..shift,undef); check_prime($stream,2); When run on my machine (under ActiveState & Win32), the code was capable of spawning only 118 threads (last prime number found: 653) before terminating with a 'Sorry. Ran out of threads' warning. In trying to figure out why I was limited to the number of threads I could create, I replaced the use threads; line with use threads (stack_size => 1);. The resultant code happily dealt with churning out 2000+ threads. Can anyone explain this behavior?

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  • Ruby custom class to and from YAML;

    - by Sanarothe
    Hi. I'm having trouble deserializing a ruby class that I wrote to YAML. Where I want to be I want to be able to pass one object around as a full 'question' which includes the question text, some possible answers (For multi. choice) and the correct answer. One module (The encoder) takes input, builds a 'question' class out of it and appends it to the question pool. Another module reads a question pool and builds an array of 'question' objects. Where I am currently Sample Question Pool --- | --- !ruby/object:MultiQ a: "no" answer: "no" b: "no" c: "no" d: "no" text: "yes?" Encoder dump to YAML file. Object is a MultiQ filled up with input. (See below.) def dump(file, object) File.open(file, 'a') do |out| YAML.dump(object.to_yaml, out) end object = nil end MultiQ Class definition class MultiQ attr_accessor :text, :answer, :a, :b, :c, :d def initialize(text, answer, a, b, c, d) @text = text @answer = answer @a = a @b = b @c = c @d = d end end The decoder (I've been trying different things, so what's here wasn't my first or best guess. But I'm at a loss and the documentation doesn't really explain things thoroughly enough.) File.open( "test_set.yaml" ) do |yf| YAML.load_documents( yf ) { |item| new = YAML.object_maker( MultiQ, item) puts new } end Questions you can answer How do I achieve my goal? What methods should I use, between parsing, loading files or documents, to successfully deserialize a Ruby class? I've already looked over the YAML Rdoc, and I didn't absorb very much, so please don't just link me to it. What other methods would you suggest using? Is there a better way to store questions like this? Should I be using document db, relational db, xml? Some other format?

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  • Node.js fetching Twitter Streaming API - EADDRNOTAVAIL

    - by Jordan Scales
    I have the following code written in node.js to access to the Twitter Streaming API. If I curl the URL below, it works. However, I cannot get it to work with my code. var https = require('https'); https.request('https://USERNAME:[email protected]/1.1/statuses/sample.json', function(res) { res.on('data', function(chunk) { var d = JSON.parse(chunk); console.log(d); }); }); But I receive the following node.js:201 throw e; // process.nextTick error, or 'error' event on first tick ^ Error: connect EADDRNOTAVAIL at errnoException (net.js:642:11) at connect (net.js:525:18) at Socket.connect (net.js:589:5) at Object.<anonymous> (net.js:77:12) at new ClientRequest (http.js:1073:25) at Object.request (https.js:80:10) at Object.<anonymous> (/Users/jordan/Projects/twitter-stream/app.js:3:7) at Module._compile (module.js:441:26) at Object..js (module.js:459:10) at Module.load (module.js:348:31) If anyone can offer an alternative solution, or explain to me why this doesn't work, I would be very grateful.

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  • Threads in WCF service

    - by dragonfly
    Hi, there is a piece of code: class WCFConsoleHostApp : IBank { private static int _instanceCounter; public WCFConsoleHostApp () { Interlocked.Increment(ref _instanceCounter); Console.WriteLine(string.Format("{0:T} Instance nr " + _instanceCounter + " created", DateTime.Now)); } private static int amount; static void Main(string[] args) { ServiceHost host = new ServiceHost(typeof(WCFConsoleHostApp)); host.Open(); Console.WriteLine("Host is running..."); Console.ReadLine(); } #region IBank Members BankOperationResult IBank.Put(int amount) { Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Putting..."); WCFConsoleHostApp.amount += amount; Thread.Sleep(20000); Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Putting done"); return new BankOperationResult { CurrentAmount = WCFConsoleHostApp.amount, Success = true }; } BankOperationResult IBank.Withdraw(int amount) { Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Withdrawing..."); WCFConsoleHostApp.amount -= amount; Thread.Sleep(20000); Console.WriteLine(string.Format("{0:00} {1}", Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread) + " Withdrawing done"); return new BankOperationResult { CurrentAmount = WCFConsoleHostApp.amount, Success = true }; } #endregion } My test client application calls that service in 50 threads (service is PerCall). What I found very disturbing is when I added Thread.Sleep(20000) WCF creates one service instance per second using different thread from pool. When I remove Thread.Sleep(20000) 50 instances are instanciated straight away, and about 2-4 threads are used to do it - which in fact I consider normal. Could somebody explain why when Thread.Sleep causes those funny delays in creating instances?

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  • Why This Maintainability Index Increase?

    - by Timothy
    I would be appreciative if someone could explain to me the difference between the following two pieces of code in terms of Visual Studio's Code Metrics rules. Why does the Maintainability Index increase slightly if I don't encapsulate everything within using ( )? Sample 1 (MI score of 71) public static String Sha1(String plainText) { using (SHA1Managed sha1 = new SHA1Managed()) { Byte[] text = Encoding.Unicode.GetBytes(plainText); Byte[] hashBytes = sha1.ComputeHash(text); return Convert.ToBase64String(hashBytes); } } Sample 2 (MI score of 73) public static String Sha1(String plainText) { Byte[] text, hashBytes; using (SHA1Managed sha1 = new SHA1Managed()) { text = Encoding.Unicode.GetBytes(plainText); hashBytes = sha1.ComputeHash(text); } return Convert.ToBase64String(hashBytes); } I understand metrics are meaningless outside of a broader context and understanding, and programmers should exercise discretion. While I could boost the score up to 76 with return Convert.ToBase64String(sha1.ComputeHash(Encoding.Unicode.GetBytes(plainText))), I shouldn't. I would clearly be just playing with numbers and it isn't truly any more readable or maintainable at that point. I am curious though as to what the logic might be behind the increase in this case. It's obviously not line-count.

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  • Problem with persisting a collection, that references an internal property, at design time in winfor

    - by Jules
    ETA: Jesus, I'm sick of this. This problem was specifically about persisting an interface collection but now on further testing it doesn't work for a normal collection. Here's some even simpler code: Public Class Anger End Class Public Class MyButton Inherits Button Private _Annoyance As List(Of Anger) <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property Annoyance() As List(Of Anger) Get Return _Annoyance End Get End Property Private _InternalAnger As Anger <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property InternalAnger() As Anger Get Return Me._InternalAnger End Get End Property Public Sub New() Me._Annoyance = New List(Of Anger) Me._InternalAnger = New Anger Me._Annoyance.Add(Me._InternalAnger) End Sub End Class The designer screws up the persistence code in the same way as the original problem. ---- Original Problem The easiest way to explain this problem is to show you some code: Public Interface IAmAnnoyed End Interface Public Class IAmAnnoyedCollection Inherits ObjectModel.Collection(Of IAmAnnoyed) End Class Public Class Anger Implements IAmAnnoyed End Class Public Class MyButton Inherits Button Private _Annoyance As IAmAnnoyedCollection <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property Annoyance() As IAmAnnoyedCollection Get Return _Annoyance End Get End Property Private _InternalAnger As Anger <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property InternalAnger() As Anger Get Return Me._InternalAnger End Get End Property Public Sub New() Me._Annoyance = New IAmAnnoyedCollection Me._InternalAnger = New Anger Me._Annoyance.Add(Me._InternalAnger) End Sub End Class And this is the code that the designer generates: Private Sub InitializeComponent() Dim Anger1 As Anger = New Anger Me.MyButton1 = New MyButton ' 'MyButton1 ' Me.MyButton1.Annoyance.Add(Anger1) // Should be: Me.MyButton1.Annoyance.Add(Me.MyButton1.InternalAnger) ' 'Form1 ' Me.Controls.Add(Me.MyButton1) End Sub I've added a comment to the above to show how the code should have been generated. Now, if I dispense with the interface and just have a collection of Anger, then it persists correctly. Any ideas?

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  • MySQL MyISAM table performance... painfully, painfully slow

    - by Salman A
    I've got a table structure that can be summarized as follows: pagegroup * pagegroupid * name has 3600 rows page * pageid * pagegroupid * data references pagegroup; has 10000 rows; can have anything between 1-700 rows per pagegroup; the data column is of type mediumtext and the column contains 100k - 200kbytes data per row userdata * userdataid * pageid * column1 * column2 * column9 references page; has about 300,000 rows; can have about 1-50 rows per page The above structure is pretty straight forwad, the problem is that that a join from userdata to page group is terribly, terribly slow even though I have indexed all columns that should be indexed. The time needed to run a query for such a join (userdata inner_join page inner_join pagegroup) exceeds 3 minutes. This is terribly slow considering the fact that I am not selecting the data column at all. Example of the query that takes too long: SELECT userdata.column1, pagegroup.name FROM userdata INNER JOIN page USING( pageid ) INNER JOIN pagegroup USING( pagegroupid ) Please help by explaining why does it take so long and what can i do to make it faster. Edit #1 Explain returns following gibberish: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE userdata ALL pageid 372420 1 SIMPLE page eq_ref PRIMARY,pagegroupid PRIMARY 4 topsecret.userdata.pageid 1 1 SIMPLE pagegroup eq_ref PRIMARY PRIMARY 4 topsecret.page.pagegroupid 1 Edit #2 SELECT u.field2, p.pageid FROM userdata u INNER JOIN page p ON u.pageid = p.pageid; /* 0.07 sec execution, 6.05 sec fecth */ id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE u ALL pageid 372420 1 SIMPLE p eq_ref PRIMARY PRIMARY 4 topsecret.u.pageid 1 Using index SELECT p.pageid, g.pagegroupid FROM page p INNER JOIN pagegroup g ON p.pagegroupid = g.pagegroupid; /* 9.37 sec execution, 60.0 sec fetch */ id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE g index PRIMARY PRIMARY 4 3646 Using index 1 SIMPLE p ref pagegroupid pagegroupid 5 topsecret.g.pagegroupid 3 Using where Moral of the story Keep medium/long text columns in a separate table if you run into performance problems such as this one.

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  • jQuery: Inserting li items one by one?

    - by Legend
    I wrote the following (part of a jQuery plugin) to insert a set of items from a JSON object into a <ul> element. ... query: function() { ... $.ajax({ url: fetchURL, type: 'GET', dataType: 'jsonp', timeout: 5000, error: function() { self.html("Network Error"); }, success: function(json) { //Process JSON $.each(json.results, function(i, item) { $("<li></li>") .html(mHTML) .attr('id', "div_li"+i) .attr('class', "divliclass") .prependTo("#" + "div_ul"); $(slotname + "div_li" + i).hide(); $(slotname + "div_li" + i).show("slow") } } }); } }); }, ... Doing this maybe adding the <li> items one by one theoretically but when I load the page, everything shows up instantaneously. Instead, is there an efficient way to make them appear one by one more slowly? I'll explain with a small example: If I have 3 items, this code is making all the 3 items appear instantaneously (at least to my eyes). I want something like 1 fades in, then 2 fades in, then 3 (something like a newsticker perhaps). Anyone has a suggestion?

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  • Calling function using 'new' is less expensive than without it?

    - by Matthew Taylor
    Given this very familiar model of prototypal construction: function Rectangle(w,h) { this.width = w; this.height = h; } Rectangle.prototype.area = function() { return this.width * this.height; }; Can anyone explain why calling "new Rectangle(2,3)" is consistently 10x FASTER than calling "Rectangle(2,3)" without the 'new' keyword? I would have assumed that because new adds more complexity to the execution of a function by getting prototypes involved, it would be slower. Example: var myTime; function startTrack() { myTime = new Date(); } function stopTrack(str) { var diff = new Date().getTime() - myTime.getTime(); println(str + ' time in ms: ' + diff); } function trackFunction(desc, func, times) { var i; if (!times) times = 1; startTrack(); for (i=0; i<times; i++) { func(); } stopTrack('(' + times + ' times) ' + desc); } var TIMES = 1000000; trackFunction('new rect classic', function() { new Rectangle(2,3); }, TIMES); trackFunction('rect classic (without new)', function() { Rectangle(2,3); }, TIMES); Yields (in Chrome): (1000000 times) new rect classic time in ms: 33 (1000000 times) rect classic (without new) time in ms: 368 (1000000 times) new rect classic time in ms: 35 (1000000 times) rect classic (without new) time in ms: 374 (1000000 times) new rect classic time in ms: 31 (1000000 times) rect classic (without new) time in ms: 368

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  • Slow MySQL Query not using filesort

    - by Canadaka
    I have a query on my homepage that is getting slower and slower as my database table grows larger. tablename = tweets_cache rows = 572,327 this is the query I'm currently using that is slow, over 5 seconds. SELECT * FROM tweets_cache t WHERE t.province='' AND t.mp='0' ORDER BY t.published DESC LIMIT 50; If I take out either the WHERE or the ORDER BY, then the query is super fast 0.016 seconds. I have the following indexes on the tweets_cache table. PRIMARY published mp category province author So i'm not sure why its not using the indexes since mp, provice and published all have indexes? Doing a profile of the query shows that its not using an index to sort the query and is using filesort which is really slow. possible_keys = mp,province Extra = Using where; Using filesort I tried adding a new multie-colum index with "profiles & mp". The explain shows that this new index listed under "possible_keys" and "key", but the query time is unchanged, still over 5 seconds. Here is a screenshot of the profiler info on the query. http://i355.photobucket.com/albums/r469/canadaka_bucket/slow_query_profile.png Something weird, I made a dump of my database to test on my local desktop so i don't screw up the live site. The same query on my local runs super fast, milliseconds. So I copied all the same mysql startup variables from the server to my local to make sure there wasn't some setting that might be causing this. But even after that the local query runs super fast, but the one on the live server is over 5 seconds. My database server is only using around 800MB of the 4GB it has available. here are the related my.ini settings i'm using default-storage-engine = MYISAM max_connections = 800 skip-locking key_buffer = 512M max_allowed_packet = 1M table_cache = 512 sort_buffer_size = 4M read_buffer_size = 4M read_rnd_buffer_size = 16M myisam_sort_buffer_size = 64M thread_cache_size = 8 query_cache_size = 128M # Try number of CPU's*2 for thread_concurrency thread_concurrency = 8 # Disable Federated by default skip-federated key_buffer = 512M sort_buffer_size = 256M read_buffer = 2M write_buffer = 2M key_buffer = 512M sort_buffer_size = 256M read_buffer = 2M write_buffer = 2M

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  • How do I show information to users belonging to different groups (web) in modx

    - by Gaurav Sharma
    Hello Everyone, I have created a website using modx evolution v1.0.2. The website that I have developed has 12 different types of users (categorized in groups). Each user will be shown a different price depending on the group to which he belongs. Till now I have been able to fetch the group name of current logged in user (created a snippet for that), but how can I achieve the above mentioned functionality so that each user should be able to see only the price that I have coded according to his group. For example: If a user is associated with the 'ocassional' group then he should be shown the price as , say, 50 bucks and if a user is associated with the 'regular' group then he should be shown the price as, say, 40 bucks I can easily do this by coding a single snippet for every product's variant, but there are a lot of variants (more than 100 and growing). I have created a resource(page) for every product and it's variant. Every variant has a price. It is this price that I want to be shown according to the logged in user group membership. I hope I am able to explain my query clearly. Please help me do this functionality. Thanks

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  • Automatic multi-page multi-column flowing text with QtWebkit (HTML/CSS/JS -> PDF)

    - by Peter Boughton
    I have some HTML documents that are converted to PDF, using software that renders using QtWebkit (not sure which version). Currently, the documents have specific tags to split into columns and pages - so whenever the wording changes, it is a manual time-consuming process to move these tags so that the columns and pages fit. Can anyone provide a way to have text auto-wrapped into the next column/page (as appropriate) when it reaches the bottom of the current container? Any HTML, CSS or JS supported by QtWebkit is ok (assuming it works in the PDF converter). (I have tested the webkit-column-* in CSS3 and it appears QtWebkit does not support this.) To make things more exciting, it also needs to: - put a header at the top of each page, with page X of Y numbering; - if an odd number of pages, add a blank page at the end (with no header); - have the ability to say "don't break inside this block" or "don't break after this header" I have put some quick example initial markup and target markup to help explain what I'm trying to do. (The actual documents are far more complicated than that, but I need a simple proof-of-concept before I attack the real ones.) Any suggestions? Update: I've got a partially working solution using Aaron's "filling up" suggestion - I'll post more details in a bit.

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  • Understanding Hibernate saveOrUpdate

    - by Stephano
    The books that I've read regarding hibernate are, at best, reference tomes. They very seldom have good code examples, so I tend to use online resources for those needs. However, I've always had a problem understanding the basic idea of hibernate persistence. I've read the books and understand the concepts, but in practice, I often see results that I don't understand. Perhaps you all can help, as you have in the past. Let's look at a simple example of a dog and a cat that are friends. This isn't a rare occurrence. It also has the benefit of being much more interesting than my business case. We want a function called "saveFriends" that takes a dog name and a cat name. We'll save the Dog and then the Cat. For this example to work, the cat is going to have a reference back to the dog. I understand this isn't an ideal example, but it's cute and works for our purposes. FriendService.java public int saveFriends(String dogName, String catName) { Dog fido = new Dog(); Cat felix = new Cat(); fido.name = dogName; fido = animalDao.saveDog(fido); felix.name = catName; [ex.A]felix.friend = fido; [ex.B]felix.friend = animalDao.getDogByName(dogName); animalDao.saveCat(felix); } AnimalDao.java (extends HibernateDaoSupport) public Dog saveDog(Dog dog) { getHibernateTemplate().saveOrUpdate(dog); return dog } public Cat saveCat(Cat cat) { getHibernateTemplate().saveOrUpdate(cat); return cat; } public Dog getDogByName(String name) { return (Dog) getHibernateTemplate().find("from Dog where name=?", name).get(0); } Now, assume for a minute that I would like to use either example A or example B to save my friend. Is one better than the other to use? I'll understand if neither of those examples work, but please explain why.

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  • NHibernate: Mapping multiple classes from a single table row

    - by Michael Kurtz
    I couldn't find an answer to this specific question. I am trying to keep my domain model object-oriented and re-use objects where possible. I am having an issue determining how to provide a mapping to multiple classes from a single row. Let me explain with an example: I have a single table, call it Customer. A customer has several attributes; but, for brevity, assume it has Id, Name, Address, City, State, ZipCode. I would like to create a Customer and Address class that look like this: public class Customer { public virtual long Id {get;set;} public virtual string Name {get;set;} public virtual Address Address {get;set;} } public class Address { public virtual string Address {get;set;} public virtual string City {get;set;} public virtual string State {get;set;} public virtual string ZipCode {get;set;} } What I am having trouble with is determining what the mapping would be for the Address class within the Customer class. There is no Address table and there isn't a "set" of addresses associated with a Customer. I just want a more object-oriented view of the Customer table in code. There are several other tables that have address information in them and it would be nice to have a reusable Address class to deal with them. Addresses are not shared so breaking all addresses into a separate table with foreign keys seems to be overkill and, actually, more painful since I would need foreign keys to multiple tables. Can someone enlighten me on this type of mapping? Please provide an example if you can. Thanks for any insights! -Mike

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  • Combining data sets without losing observations in SAS

    - by John
    Hye guys, I know, another post another problem :D :(. I took a screenshot to easily explain my problem. http://i39.tinypic.com/rhms0h.jpg As you can see I want to merge two tables (again), the Base & Analyst table. What I want to achieve is displayed in the right bottom corner table. I’m calculating the number of total analysts and female analysts for each month in the analyst table. In the base table I have different observations for one company (here company Alcoa with ticker AA). When I use the following command: data want; merge base analyst; by month ; run; I get the right up corner problem. My observations in the main table are being narrowed down to only 4 observations (for each different year one observation, 2001, 2002, 2005, 2006). What I want is that the observations are not reduced but that for every year the same data is being placed as shown in the right bottom corner. What am I missing in my merge command? In both tables I have month as a time count variable ( the observations in my base table are monthly) on which I need to merge. For clarity I added 2 screenshots of my real databases in SAS. The base table: http://i42.tinypic.com/dr5jky.jpg The analyst table: http://i40.tinypic.com/eqpmqq.jpg Here is what my merged table looks like: http://i43.tinypic.com/116i62s.jpg You can clearly see that the merged table only has four observations left for AA (one for each unique year) instead of the original 8. Anyone an idea to solve this?

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  • Programming test for ASP.NET C# developer job - Opinions please!

    - by Indy
    Hi all, We are hiring a .NET C# developer and I have developed a technical test for the candidates to complete. They have an hour and it has two parts, some knowledge based questions covering asp.net, C# and SQL and a small practical test. I'd appreciate feedback on the test, is it sufficient to test the programmers ability? What would you change if anything? Part One. What the are events fired as part of the ASP.NET Page lifecycle. What interesting things can you do at each? How does ViewState work and why is it either useful or bad? What is a common way to create web services in ASP.NET 2.0? What is the GAC? What is boxing? What is a delegate? The C# keyword .int. maps to which .NET type? Explain the difference between a Stored Procedure and a Trigger? What is an OUTER Join? What is @@IDENTITY? Part Two: You are provided with the Northwind Database and the attached DB relationship diagram. Please create a page which provides users with the following functionality. You don’t need to be too concerned with the presentation detail of the page. Select a customer from a list, and see all the orders placed by that customer. For the same customer, find all their orders which are Beverages and the quantity is more than 5. I was aware of setting the right balance of difficulty on this as there is an hour's test. I was able to complete the practical test in under 30 mins using SQLDatasource and the query designer in visual studio and the test questions, I am looking to see how they approach it logically and whether they use the tools available. Many thanks!

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  • How to insert an Array/Objet into SQL (bestpractice)

    - by Jason
    I need to store three items as an array in a single column and be able to quickly/easily modify that data in later functions. [---YOU CAN SKIP THIS PART IF YOU TRUST ME--] To be clear, I love and use x_ref tables all the time but an x_ref doesn't work here because this is not a one-to-many relationship. I am making a project management tool that among other things, assigns a user to a project and assigns hours to that project on a weekly basis, per user, sometimes for weeks many weeks into the future. Of course there are many projects, a project can have many team members, a team member can be involved with many projects at one time BUT its not one-to-many because a team member can be working many weeks on the same project but have different hours for different weeks. In other words, each object really is unique. Also/finally, this data can be changed at any time by any team-member - hence it needs to be easily to manipulate. Basically, I need to handle three values (the team member, the week we're talking about, and how many hours) dropped into a project row in the projects table (under the column for project team members) and treated as one item - a team member - that will actually be part of a larger array of all the team members involved on the project. [--END SKIP, START READING HERE :) --] So assuming that the application's general schema and relation tables aren't total crap and that we are in fact up against a wall in this one case to use an array/object as a value for this column, is there a best practice for that? Like a particular SQL data-type? A particular object/array format? CSV? JSON? XML? Most of the app is in C# but (for very odd reasons that I won't explain) we could really use any environment if there is a particular one that handles this well. For the moment, I am thinking either (webservice + JS/JSON) or PHP unserialize/serialize (but I am bit sketched out by the PHP solution because it seems a bit cumbersome when using ajax?) Thoughts anyone?

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  • REST API error return good practices

    - by Remus Rusanu
    I'm looking for guidance on good practices when it comes to return errors from a REST API. I'm working on a new API so I can take it any direction right now. My content type is XML at the moment, but I plan to support JSON in future. I am now adding some error cases, like for instance a client attempts to add a new resource but has exceeded his storage quota. I am already handling certain error cases with HTTP status codes (401 for authentication, 403 for authorization and 404 for plain bad request URIs). I looked over the blessed HTTP error codes but none of the 400-417 range seems right to report application specific errors. So at first I was tempted to return my application error with 200 OK and a specific XML payload (ie. Pay us more and you'll get the storage you need!) but I stopped to think about it and it seems to soapy (/shrug in horror). Besides it feels like I'm splitting the error responses into distinct cases, as some are http status code driven and other are content driven. So what is the SO crowd recommendation? Good practices (please explain why!) and also, from a client pov, what kind of error handling in the REST API makes life easier for the client code?

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  • Perl: Process Communcation

    - by Shiftbit
    Can anyone explain how I can successfully get my process communicating. I find the perldoc on IPC confusing. What I have so far is: $| = 1; $SIG{CHLD} = {wait}; my $parentPid = $$; if ($pid = fork();) ) { if ($pid == 0) { pipe($parentPid, $$); open PARENT, "<$parentPid"; while (<PARENT>) { print $_; } close PARENT; exit(); } else { pipe($parentPid, $pid); open CHILD, ">$pid"; or error("\nError opening: childPid\nRef: $!\n"); open (FH, "<list") or error("\nError opening: list\nRef: $!\n"); while(<FH>) { print CHILD, $_; } close FH or error("\nError closing: list\nRef: $!\n"); close CHILD or error("\nError closing: childPid\nRef: $!\n); } else { error("\nError forking\nRef: $!\n"); } First Question is what does Perldoc pipe mean by READHANDLE, WRITEHANDLE? Second Questions is can I implement a solution without relying on CPAN or other modules?

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  • WPF Border DesiredHeight

    - by Joseph Sturtevant
    The following Microsoft example code contains the following: <Grid> ... <Border Name="Content" ... > ... </Border> </Grid> <ControlTemplate.Triggers> <Trigger Property="IsExpanded" Value="True"> <Setter TargetName="ContentRow" Property="Height" Value="{Binding ElementName=Content,Path=DesiredHeight}" /> </Trigger> ... </ControlTemplate.Triggers> When run, however, this code generates the following databinding error: System.Windows.Data Error: 39 : BindingExpression path error: 'DesiredHeight' property not found on 'object' ''Border' (Name='Content')'. BindingExpression:Path=DesiredHeight; DataItem='Border' (Name='Content'); target element is 'RowDefinition' (HashCode=2034711); target property is 'Height' (type 'GridLength') Despite this error, the code works correctly. I have looked through the documentation and DesiredHeight does not appear to be a member of Border. Can anyone explain where DesiredHeight is coming from? Also, is there any way to resolve/suppress this error so my program output is clean?

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  • Effective java hashcode implementation

    - by Scobal
    I was wondering if someone could explain in detail what (int)(l ^ (l >>> 32)); does in the following hashcode implementation (generated by eclipse, but the same as Effective Java): private int i; private char c; private boolean b; private short s; private long l; private double d; private float f; @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + i; result = prime * result + s; result = prime * result + (b ? 1231 : 1237); result = prime * result + c; long t = Double.doubleToLongBits(d); result = prime * result + (int) (t ^ (t >>> 32)); result = prime * result + Float.floatToIntBits(f); result = prime * result + (int) (l ^ (l >>> 32)); return result; } Thanks!

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  • How do I use foreach with QDomNodeList in Qt?

    - by Venemo
    Hi Everyone, I'm new to Qt and I'm learning something new every day. Currently, I'm developing a small application for my Nokia N900 in my free time. Everything is fine, I am able to compile and run Maemo applications on the device. I've just learned about the foreach keyword in Qt. (I know it is not in C++, so I didn't think about it until I accidentally stumbled upon a Qt doc that mentioned it.) So, I decided to change my quite annoying and unreadable loops to foreach, but I failed with this: QDomNodeList list = doc.lastChild().childNodes().at(1).firstChild().childNodes(); for (int x = 0; x < list.count(); x++) { QDomElement node = list.at(x).toElement(); // Do something with node } This is how I tried: foreach (QDomElement node, doc.lastChild().childNodes().at(1).firstChild().childNodes()) { // Do something with node } For some reason the above code doesn't even compile. I get cryptic error messages from the compiler. Could someone please explain to me how to get it right? If the foreach loop doesn't support QDomNodeList, is there a way of handling XML files that do support foreach?

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  • Algorithm to see if keywords exist inside a string

    - by rksprst
    Let's say I have a set of keywords in an array {"olympics", "sports tennis best", "tennis", "tennis rules"} I then have a large list (up to 50 at a time) of strings (or actually tweets), so they are a max of 140 characters. I want to look at each string and see what keywords are present there. In the case where a keyword is composed of multiple words like "sports tennis best", the words don't have to be together in the string, but all of them have to show up. I've having trouble figuring out an algorithm that does this efficiently. Do you guys have suggestions on a way to do this? Thanks! Edit: To explain a bit better each keyword has an id associated with it, so {1:"olympics", 2:"sports tennis best", 3:"tennis", 4:"tennis rules"} I want to go through the list of strings/tweets and see which group of keywords match. The output should be, this tweet belongs with keyword #4. (multiple matches may be made, so anything that matches keyword 2, would also match 3 -since they both contain tennis). When there are multiple words in the keyword, e.g. "sports tennis best" they don't have to appear together but have to all appear. e.g. this will correctly match: "i just played tennis, i love sports, its the best"... since this string contains "sports tennis best" it will match and be associated with the keywordID (which is 2 for this example).

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  • What is Ruby's analog to Python Metaclasses?

    - by Sean Copenhaver
    Python has the idea of metaclasses that, if I understand correctly, allow you to modify an object of a class at the moment of construction. You are not modifying the class, but instead the object that is to be created then initialized. Python (at least as of 3.0 I believe) also has the idea of class decorators. Again if I understand correctly, class decorators allow the modifying of the class definition at the moment it is being declared. Now I believe there is an equivalent feature or features to the class decorator in Ruby, but I'm currently unaware of something equivalent to metaclasses. I'm sure you can easily pump any Ruby object through some functions and do what you will to it, but is there a feature in the language that sets that up like metaclasses do? So again, Does Ruby have something similar to Python's metaclasses? Edit I was off on the metaclasses for Python. A metaclass and a class decorator do very similar things it appears. They both modify the class when it is defined but in different manners. Hopefully a Python guru will come in and explain better on these features in Python. But a class or the parent of a class can implement a __new__(cls[,..]) function that does customize the construction of the object before it is initialized with __init__(self[,..]).

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