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• BufferedImage & ColorModel in Java

  - by spol

  I am using a image processing library in java to manipulate images.The first step I do is I read an image and create a java.awt.Image.BufferedImage object. I do it in this way, BufferedImage sourceImage = ImageIO.read( new File( filePath ) ); The above code creates a BufferedImage ojbect with a DirectColorModel: rmask=ff0000 gmask=ff00 bmask=ff amask=0. This is what happens when I run the above code on my macbook. But when I run this same code on a linux machine (hosted server), this creates a BufferedImage object with ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace@c39a20 transparency = 1 has alpha = false isAlphaPre = false. And I use the same jpg image in both the cases. I don't know why the color model on the same image is different when run on mac and linux. The colormodel for mac has 4 components and the colormodel for linux has 3 components.There is a problem arising because of this, the image processing library that I use always assumes that there are always 4 components in the colormodel of the image passed, and it throws array out of bounds exception when run on linux box. But on macbook, it runs fine. I am not sure if I am doing something wrong or there is a problem with the library. Please let me know your thoughts. Also ask me any questions if I am not making sense!

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• Using boost::random to select from an std::list where elements are being removed

  - by user144182

  See this related question on more generic use of the Boost Random library. My questions involves selecting a random element from an std::list, doing some operation, which could potentally include removing the element from the list, and then choosing another random element, until some condition is satisfied. The boost code and for loop look roughly like this: // create and insert elements into list std::list<MyClass> myList; //[...] // select uniformly from list indices boost::uniform_int<> indices( 0, myList.size()-1 ); boost::variate_generator< boost::mt19937, boost::uniform_int<> > selectIndex(boost::mt19937(), indices); for( int i = 0; i <= maxOperations; ++i ) { int index = selectIndex(); MyClass & mc = myList.begin() + index; // do operations with mc, potentially removing it from myList //[...] } My problem is as soon as the operations that are performed on an element result in the removal of an element, the variate_generator has the potential to select an invalid index in the list. I don't think it makes sense to completely recreate the variate_generator each time, especially if I seed it with time(0).

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• Passing user_id, site_id, and question_id to same table on create...

  - by bgadoci

  I can't seem to figure out how to do this. I am trying to pass four different variables to a single table. To be more specific I am trying to create a "like" in a likes table that also captures the site_id (like an answer), user_id, and the question_id. Here is the set up. class Like < ActiveRecord::Base belongs_to :site belongs_to :user belongs_to :question end I will spare you the reverse, has_many associations but they are there. Here is the likes controller where I think the problem is. class LikesController < ApplicationController def create @user = current_user @site = Site.find(params[:site_id]) @like = @site.likes.create!(params[:like]) @like.user = current_user @like.save respond_to do |format| format.html { redirect_to @site} format.js end end end This code successfully passes the like and site_id but after many different variations of trying I can't get it to pass the question id. Here is my form: /views/sites/_site.html.erb (though the partial is being displayed in the /views/questions/show.html.erb file). <% remote_form_for [site, Like.new] do |f| %> <%= f.hidden_field :site_name, :value => "#{site.name}" %> <%= f.hidden_field :ip_address, :value => "#{request.remote_ip}" %> <%= f.hidden_field :like, :value => "1" %> <%= submit_tag "^" , :class => 'voteup' %> <% end %>

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• Typical Search, Result and Detail Workflow Staying Within an Android Tab

  - by Justin

  So, I've been banging my head looking for a good solution for a few days and am stuck. I have a search screen (Activity) in a tab, and after the user enters a value and clicks "search" I would like the results to come back in that same tab, and then if an item from the results is selected, to show more detailed results, in that same tab. I have it all working now in separate activities, and even the first step working in a tab, but as soon as I call the activity to process he search results... i.e. startActivity(i); for the results Activity, the results displayed are not in the tab! I am having a very difficult time getting this flow to work all under a tab. Any thoughts on how to make this happen? I keep hearing that Android views should be used instead of activities, but am I then to assume that all the logic I have right now for 3 activity needs to go inside 1 activity and then I need to handle setting the content and state for each of these cases? Plus, won't the history stack not work as pressing the back button will take the user out of the application, instead of taking them from say the search result to the search screen, or the details to the search results, etc. This seems like a mess. Can anyone show a more complex example of tabs or how one might have a simple search, result and detail workflow staying in a tab? I have seen a few questions on this concept of keeping activities "within a tab", but no good resolution. Please help.

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• Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

  - by volnet

  #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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• Please clarify how create/update happens against child entities of an aggregate root

  - by christian

  After much reading and thinking as I begin to get my head wrapped around DDD, I am a bit confused about the best practices for dealing with complex hierarchies under an aggregate root. I think this is a FAQ but after reading countless examples and discussions, no one is quite talking about the issue I'm seeing. If I am aligned with the DDD thinking, entities below the aggregate root should be immutable. This is the crux of my trouble, so if that isn't correct, that is why I'm lost. Here is a fabricated example...hope it holds enough water to discuss. Consider an automobile insurance policy (I'm not in insurance, but this matches the language I hear when on the phone w/ my insurance company). Policy is clearly an entity. Within the policy, let's say we have Auto. Auto, for the sake of this example, only exists within a policy (maybe you could transfer an Auto to another policy, so this is potential for an aggregate as well, which changes Policy...but assume it simpler than that for now). Since an Auto cannot exist without a Policy, I think it should be an Entity but not a root. So Policy in this case is an aggregate root. Now, to create a Policy, let's assume it has to have at least one auto. This is where I get frustrated. Assume Auto is fairly complex, including many fields and maybe a child for where it is garaged (a Location). If I understand correctly, a "create Policy" constructor/factory would have to take as input an Auto or be restricted via a builder to not be created without this Auto. And the Auto's creation, since it is an entity, can't be done beforehand (because it is immutable? maybe this is just an incorrect interpretation). So you don't get to say new Auto and then setX, setY, add(Z). If Auto is more than somewhat trivial, you end up having to build a huge hierarchy of builders and such to try to manage creating an Auto within the context of the Policy. One more twist to this is later, after the Policy is created and one wishes to add another Auto...or update an existing Auto. Clearly, the Policy controls this...fine...but Policy.addAuto() won't quite fly because one can't just pass in a new Auto (right!?). Examples say things like Policy.addAuto(VIN, make, model, etc.) but are all so simple that that looks reasonable. But if this factory method approach falls apart with too many parameters (the entire Auto interface, conceivably) I need a solution. From that point in my thinking, I'm realizing that having a transient reference to an entity is OK. So, maybe it is fine to have a entity created outside of its parent within the aggregate in a transient environment, so maybe it is OK to say something like: auto = AutoFactory.createAuto(); auto.setX auto.setY or if sticking to immutability, AutoBuilder.new().setX().setY().build() and then have it get sorted out when you say Policy.addAuto(auto) This insurance example gets more interesting if you add Events, such as an Accident with its PolicyReports or RepairEstimates...some value objects but most entities that are all really meaningless outside the policy...at least for my simple example. The lifecycle of Policy with its growing hierarchy over time seems the fundamental picture I must draw before really starting to dig in...and it is more the factory concept or how the child entities get built/attached to an aggregate root that I haven't seen a solid example of. I think I'm close. Hope this is clear and not just a repeat FAQ that has answers all over the place.

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• Grails - Where to store properties related to domains

  - by GalmWing

  This is something I have been struggling about for some time now. The thing is: I have many (20 or so) static arrays of values. I say static because that is how I'm actually storing them, as static arrays inside some domains. For example, if I have a list of known websites, I do: class Website { ... static websites = ["web1", "web2" ...] } But I do this just while developing, because I can easily change the arrays if needed, but what I'm going to do when the application is ready for deployment? In my project it is very probable that, at some point, these arrays of values change. I've been researching on that matter, one can store application properties inside an external .properties file, but it will be impossible to store an array, even futile, because if some array gets an additional value, the application can't recognize it until the name of the new property is added where needed. Another approach is to store this information in the database, but for some reason it seems like a waste to add 20 or more tables that will have just two rows, an id and a name. And the last option, as far as I know, would be an XML, but I'm not very experienced with those. It seems groovy has a way of creating and reading XML files relatively easy, but I don't know how difficult would be to modify an XML whose layout is predefined in the application. Needless to say that storing them in the config.groovy is not an option since any change will require to recompile. I haven't come across some "standard" (maybe a best practice?) way of dealing with these. So the questions is: Where to store these arrays?

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• FBML wallpost by clicking on image or button

  - by psaha

  Hello, I'm creating one facebook application with FBML. What I want is: I have several images like, <fb:tag name="img"> <fb:tag-attribute name="src">http://My_Img_Url_1.jpg</fb:tag-attribute> </fb:tag> <fb:tag name="img"> <fb:tag-attribute name="src">http://My_Img_Url_2.jpg</fb:tag-attribute> </fb:tag> While I click on the image it should open one popup "post to wall" or "Post to your Friend's wall" with the corresponding image My_Img_Url_n.jpg. I can use FBML share button like: METHOD-1 <fb:share-button class="meta"> <meta name="title" content="Image_TITLE"/> <meta name="description" content="Image_Descrip"/> <link rel="image_src" href="http://My_Img_Url_1.jpg"/> <link rel="target_url" href="Some_Target_URL"/> </fb:share-button> OR, METHOD-2: I can call fb:ui <script> FB.init({ appId:'111111111111111', cookie:true, status:true, xfbml:true }); FB.ui({ method: 'feed', name: '', link: '', picture: 'http://My_Img_Url_1.jpg' }); </script> Now the questions are: If I click on any image it will call either METHOD-1 or METHOD-2 and it will popup with that image. How can I do that? If I use <fb:multi-friend-input /> for posting to friend's wall, How can I do?

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• Visual Studio internal project references not always working

  - by Chris

  I am using Visual Studio and a solution with 10 or so projects in (mostly VB, some C#) which have various dependencies set up. Usually when I compile the solution it works fine. Occasionally when I do it I get a build error saying that one of the projects referenced is the wrong version (I think always the same one, possibly may be two that can cause problems). In this case going to the solution explorer and right clicking on the mentioned project and saying "rebuild" followed by another full build makes it work fine. I assume there is something set up wrong somewhere but I didn't set up the solution myself initially and a quick look through doesn't show anything immediately wrong. It feels like there is some kind of race condition, that VS is internally setting the version number of the project it needs before that project has been rebuilt and thus gets it wrong or something like that but I'm sure VS should handle all this sort of thing properly. Can anybody please suggest places that I could check for whether this has been correctly set up... And I should finally note that since I don't have reliable repro of this I may not be able to respond to questions too quickly. For example the obvious one of "Could you give the exact error message" will have to wait since I didn't think to copy it this morning, it was only after I cleared it up with the above steps that I thought to post here. Similarly any solutions may take a while to confirm.

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• Confused about Android API's and compatability

  - by Keith

  I have purchased an HTC Incredible and have dived into the world of android! Only to find myself totally confused about the API levels and backward compatibility. My device runs the 2.1 OS, but I know that most of the devices out there run 1.5 or 1.6; and soon the 2.2 OS will be running on new devices. The SDK has gone through such enormous changes, that even constants have been renamed (from VIEW_ACTION to ACTION_VIEW for example). Methods have been added and removed (onPause replacing the earlier call, etc al). So, If I want to write an application that will work from 1.6+, does that mean I have to install and write my code using the 1.6 API; then test on later versions? Or can I write using the 2.1 SDK and just set the minSDK level and not use "new" features? I have never worked with an SDK that changes SO drastically from release to release! So I am not sure what to do.... I read through an article on the Android Development site(and this posting on stack overflow that references it: http://stackoverflow.com/questions/2076150/should-a-legacy-android-application-be-rebuilt-using-sdk-2-1), but it was still not very clear to me. Any help would be appreciated

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• Including Data From DropDownList Into Gridview

  - by Mike Keller

  I feel a little embarassed posting two questions relating to the same problem, but the first one ended up answering a question that I believe is unrelated to the solution so I'm leaving it up and outlining what I'm trying to accomplish with the hopes that someone can help out a .Net noob. What I need to be able to do is create a field in my gridview that contains a link that passes two variables. One is pulled from within the gridviews datasource and the other needs to be pulled from a textbox control outside the gridview. From what I've read so far you cannot use a hyperlinkfield for this as the datanavigateurlfields cannot be set to pull from anything but the gridview's data source. What I attempted to do was create a template field where in the itemtemplate I called: <a href="example.aspx?e=<%# Eval(ExampleList.SelectedItem.Value) %>">Test</a> That comes back with an error like this: DataBinding: 'System.Data.DataRowView' does not contain a property with the value 'TestData' Any clues to make this happen would be appreciated, like I said I'm pretty new to .Net so please be gentle. I tried to do my homework before posting this.

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• Fast find object by string property

  - by Andrew Kalashnikov

  Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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• Why is Excel's 'Evaluate' method a general expression evaluator?

  - by jtolle

  A few questions have come up recently involving the Application.Evaluate method callable from Excel VBA. The old XLM macro language also exposes an EVALUATE() function. Both can be quite useful. Does anyone know why the evaluator that is exposed can handle general expressions, though? My own hunch is that Excel needed to give people a way to get ranges from string addresses, and to get the value of named formulas, and just opening a portal to the expression evaluator was the easiest way. (The help for the VBA version does say its purpose it to "convert a Microsoft Excel name to an object or a value".) But of course you don't need the ability to evaluate arbitrary expressions just to do that. (That is, Excel could provide a Name.Evaluate method or something instead.) Application.Evaluate seems kind of...unfinished. It's full behavior isn't very well documented, and there are quite a few quirks and limitations (as described by Charles Williams here: http://www.decisionmodels.com/calcsecretsh.htm) with what is exposed. I suppose the answer could be simply "why not expose it?", but I'd be interested to know what design decisions led to this feature taking the form that it does. Failing that, I'd be interested to hear other hunches.

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• How can I run some common code from both (a) scheduled via Windows Task & (b) manually from within W

  - by Greg

  Hi, QUESTION - How can I run some common code from both (a) scheduled via Windows Task & (b) manually from within WinForms app? BACKGROUND: This follows on from the http://stackoverflow.com/questions/2489999/how-can-i-schedule-tasks-in-a-winforms-app thread REQUIREMENTS C# .NETv3.5 project using VS2008 There is an existing function which I want to run both (a) manually from within the WinForms application, and (b) scheduled via Windows Task. APPROACHES So what I'm trying to understand is what options are there to make this work eg Is it possible for a windows task to trigger a function to run within a running/existing WinForms application? (doesn't sound solid I guess) Split code out into two projects and duplicate for both console application that the task manager would run AND code that the winforms app would run Create a common library and re-use this for both the above-mentioned projects in the bullet above Create a service with an interface that both the task manager can access plus the winforms app can manage Actually each of these approaches sounds quite messy/complex - would be really nice to drop back to have the code only once within the one project in VS2008, the only reason I ask about this is I need to have a scheduling function and the suggestion has been to use http://taskscheduler.codeplex.com/ as the means to do this, which takes the scheduling out of my VS2008 project... thanks

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• Jquery (non-gem) plugin won't work in my rails 3.2 app

  - by jfdimark

  I'm trying to equalize columns in my rails 3.2 app, and while there may be a better way to do it then my current attempt, after hours of trying to make it work I'd like to see if anyone can point out specifically why this jQuery plugin (which isn't a gem) is not working. I'm not getting any errors in the developer console, so it's hard to pin point. Here's the relevant code: The index view, where I've followed the plugin's instructions: div id="column-group"> <div class="equalize span5 offset1 UserProfile"> <% if user_signed_in? %> <h3>Hello <%= current_user.name %>!</h3> </div> <div class="equalize span5 MemberDisplay"> My application.js file, where I've also included the specific js code, so it would definitely be picked up by the application: //= require jquery //= require jquery_ujs //= require bootstrap //= require equalize_column_heights //= require_tree . $(document).ready(function() { $("#column-group").equalize_column_heights("equalize"); }); The jQuery plugin code, which is saved in my vendor/assets/javascripts folder: (function ($) { $.fn.equalize_column_heights = function (equalize_class) { var tallest_column=0; parent_id = "column-group" + $(this).attr("id") + " ." + equalize_class; $(parent_id).each(function(index, value) { if (tallest_column < $(this).height()){ tallest_column = $(this).height(); } }); $(parent_id).each(function(index, value) { $(this).css({'min-height': tallest_column}); }); } }(jQuery)); I've read all the rails guides documentation on the asset pipeline and all the relevant jQuery-rails3 questions on SO, but after several hours, I just can't seem to figure this one out. If anyone can point to other tutorials on how to get non-gem jQuery plugins to work in a Rails 3.2 app then I'd be glad to take a look!

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• MySQL: optimization of table (indexing, foreign key) with no primary keys

  - by Haradzieniec

  Each member has 0 or more orders. Each order contains at least 1 item. memberid - varchar, not integer - that's OK (please do not mention that's not very good, I can't change it). So, thera 3 tables: members, orders and order_items. Orders and order_items are below: CREATE TABLE `orders` ( `orderid` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT, `memberid` VARCHAR( 20 ), `Time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , `info` VARCHAR( 3200 ) NULL , PRIMARY KEY (orderid) , FOREIGN KEY (memberid) REFERENCES members(memberid) ) ENGINE = InnoDB; CREATE TABLE `order_items` ( `orderid` INT(11) UNSIGNED NOT NULL, `item_number_in_cart` tinyint(1) NOT NULL , --- 5 items in cart= 5 rows `price` DECIMAL (6,2) NOT NULL, FOREIGN KEY (orderid) REFERENCES orders(orderid) ) ENGINE = InnoDB; So, order_items table looks like: orderid - item_number_in_cart - price: ... 1000456 - 1 - 24.99 1000456 - 2 - 39.99 1000456 - 3 - 4.99 1000456 - 4 - 17.97 1000457 - 1 - 20.00 1000458 - 1 - 99.99 1000459 - 1 - 2.99 1000459 - 2 - 69.99 1000460 - 1 - 4.99 ... As you see, order_items table has no primary keys (and I think there is no sense to create an auto_increment id for this table, because once we want to extract data, we always extract it as WHERE orderid='1000456' order by item_number_in_card asc - the whole block, id woudn't be helpful in queries). Once data is inserted into order_items, it's not UPDATEd, just SELECTed. The questions are: I think it's a good idea to put index on item_number_in_cart. Could anybody please confirm that? Is there anything else I have to do with order_items to increase the performance, or that looks pretty good? I could miss something because I'm a newbie. Thank you in advance.

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• Practicing inserting data into an array by using binary search, few problems

  - by HelpNeeder

  I'm trying to create a method which inserts and then sort elements in form of binary form. The problem I am experiencing that my code doesn't insert data correctly which means that output does not appear to be in order at all. The list is not organized, and data is added in order that is being inserted. Now, 2 questions, what am I doing wrong here? And how to fix this? public void insertBinarySearch(long value) // put element into array { int j = 0; int lower = 0; int upper = elems-1; int cur = 0; while (cur < elems) { curIn = (lower + upper ) / 2; if(a[cur] < value) { j = cur + 1; break; } else if(a[cur] > value) { j = cur; break; } else { if(a[cur] < value) lower = cur + 1; else upper = cur - 1; } } for(int k = elems; k > j; k--) a[k] = a[k-1]; a[j] = value; elems++; }

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• MySQL: Limit rows linked to each joined row

  - by SolidSnakeGTI

  Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

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• What should a hobbyist do to develop good programming skills after basics?

  - by thyrgle

  So I'll say right here that I'm no professional coder. I'm a hobbyist. And pretty much like other people I feel like I'm doing it wrong. Like this question A feeling that I'm not a good programmer if have began to feel like that. Now I know basically that they say you shouldn't worry and that your good even if you continuously doubt yourself. But, they are talking to him. I'm not like him (in the sense I'm more of a newbie)... I've been coding as a hobbyist for 3 years (3 hobbyist years mind you!) unlike his 10-11 years that he states. Also, the only thing I've probably read in-depth is Teach Yourself C++ in 21 Days. And before I continue, just so your not confused about the various questions I've posted on (mostly) iPhone and OpenGL, I have poked and prodded at those two things for a few months each and finally sort of got a hang of both of them. But, from what I've noticed, is that I suck at making good code. For me its not even a debate of whether I'm doing it wrong or not: I can tell (from the various spaghetti code I create and other various discrepancies I, and others, can see and have noted in my code). What is a good way to get rid of these awful habits of mine and do it in a more correct, or if there is no "correct way" then I mean "typical", way?

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• Populate JOIN into a list in one database query

  - by axio

  I am trying to get the records from the 'many' table of a one-to-many relationship and add them as a list to the relevant record from the 'one' table. I am also trying to do this in a single database request. Code derived from http://stackoverflow.com/questions/1580199/linq-to-sql-populate-join-result-into-a-list almost achieves the intended result, but makes one database request per entry in the 'one' table which is unacceptable. That failing code is here: var res = from variable in _dc.GetTable<VARIABLE>() select new { x = variable, y = variable.VARIABLE_VALUEs }; However if I do a similar query but loop through all the results, then only a single database request is made. This code achieves all goals: var res = from variable in _dc.GetTable<VARIABLE>() select variable; List<GDO.Variable> output = new List<GDO.Variable>(); foreach (var v2 in res) { List<GDO.VariableValue> values = new List<GDO.VariableValue>(); foreach (var vv in v2.VARIABLE_VALUEs) { values.Add(VariableValue.EntityToGDO(vv)); } output.Add(EntityToGDO(v2)); output[output.Count - 1].VariableValues = values; } However the latter code is ugly as hell, and it really feels like something that should be do-able in a single linq query. So, how can this be done in a single linq query that makes only a single database query? In both cases the table is set to preload using the following code: _dc = _db.CreateLinqDataContext(); var loadOptions = new DataLoadOptions(); loadOptions.LoadWith<VARIABLE>(v => v.VARIABLE_VALUEs); _dc.LoadOptions = loadOptions; I am using .NET 3.5, and the database back-end was generated using SqlMetal.

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• Effective optimization strategies on modern C++ compilers

  - by user168715

  I'm working on scientific code that is very performance-critical. An initial version of the code has been written and tested, and now, with profiler in hand, it's time to start shaving cycles from the hot spots. It's well-known that some optimizations, e.g. loop unrolling, are handled these days much more effectively by the compiler than by a programmer meddling by hand. Which techniques are still worthwhile? Obviously, I'll run everything I try through a profiler, but if there's conventional wisdom as to what tends to work and what doesn't, it would save me significant time. I know that optimization is very compiler- and architecture- dependent. I'm using Intel's C++ compiler targeting the Core 2 Duo, but I'm also interested in what works well for gcc, or for "any modern compiler." Here are some concrete ideas I'm considering: Is there any benefit to replacing STL containers/algorithms with hand-rolled ones? In particular, my program includes a very large priority queue (currently a std::priority_queue) whose manipulation is taking a lot of total time. Is this something worth looking into, or is the STL implementation already likely the fastest possible? Along similar lines, for std::vectors whose needed sizes are unknown but have a reasonably small upper bound, is it profitable to replace them with statically-allocated arrays? I've found that dynamic memory allocation is often a severe bottleneck, and that eliminating it can lead to significant speedups. As a consequence I'm interesting in the performance tradeoffs of returning large temporary data structures by value vs. returning by pointer vs. passing the result in by reference. Is there a way to reliably determine whether or not the compiler will use RVO for a given method (assuming the caller doesn't need to modify the result, of course)? How cache-aware do compilers tend to be? For example, is it worth looking into reordering nested loops? Given the scientific nature of the program, floating-point numbers are used everywhere. A significant bottleneck in my code used to be conversions from floating point to integers: the compiler would emit code to save the current rounding mode, change it, perform the conversion, then restore the old rounding mode --- even though nothing in the program ever changed the rounding mode! Disabling this behavior significantly sped up my code. Are there any similar floating-point-related gotchas I should be aware of? One consequence of C++ being compiled and linked separately is that the compiler is unable to do what would seem to be very simple optimizations, such as move method calls like strlen() out of the termination conditions of loop. Are there any optimization like this one that I should look out for because they can't be done by the compiler and must be done by hand? On the flip side, are there any techniques I should avoid because they are likely to interfere with the compiler's ability to automatically optimize code? Lastly, to nip certain kinds of answers in the bud: I understand that optimization has a cost in terms of complexity, reliability, and maintainability. For this particular application, increased performance is worth these costs. I understand that the best optimizations are often to improve the high-level algorithms, and this has already been done.

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• Should I go to school and get my degree in computer science?

  - by ryan

  I'll try and keep this short and simple. I've always enjoyed programming and I've been doing it since high school. Right after I graduated from high school (2002), I opted to skip college because I was offered a software engineer position. I quit after a couple of years later to team up on various startup companies. However, most of them did not launch as well as expected. But it honestly did not matter to me because I've learned so much from that experience. So fast forwarding to today, now turned 25, I need a job due to this tough economic climate. Looking on Craigslist, a lot of the listings require computer science degrees. It's evident now that programming is what I want to do because I seem to never get enough of it. But just the thought of having to push 2 years without attending any real computer class for an Associates at age 25 is very, very discouraging. And the thought of having to learn from basic (Hello WOOOOORRLLLD) just does not seem exciting. I guess I have 3 questions to wrap this up: Should I just suck it up and go back to school while working at McDonalds at age 25? Is there a way where I can just skip all the boring stuff and just get tested with what I know? From your experience, how many jobs use computer science degrees as prerequisites? Or am I screwed and better pray that my next startup will be the next big thing?

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• Strange response from WCF service, how to return json easily

  - by Exitos

  I want to get a service to respond with just JSON. I have written the following code: namespace BM.Security { [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class AssocFileService { [OperationContract] [WebGet(ResponseFormat = WebMessageFormat.Json)] public List<Person> GetPeople(int message) { List<Person> myList = new List<Person>(); Person p = new Person() { Age = 28, Name="Name1" }; Person p2 = new Person() { Age = 26, Name = "Name2" }; myList.Add(p); myList.Add(p2); return myList; } } [DataContract] public class Person { [DataMember] public string Name { get; set; } [DataMember] public int Age { get; set; } } } But im getting the following JSON back which is really wierd... { "d" : [ { "Age" : 28, "Name" : "Name1", "__type" : "Person:#Bm.Security" }, { "Age" : 26, "Name" : "Name2", "__type" : "Person:#BM.Security" } ] } I'm totally stumped by the "d" no idea where that has come from. And also by the __type variable, no thanks don't really want that in my Json :-( How do I set the root node in my data to replace that d? Where did the d come from? So many questions... Hope someone can help....

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• How do I tell whether my IE is 64-bit? (For that matter, Java too?)

  - by user225626

  Millions of questions already on the web about how to tell whether the OS is 64-bit, but not whether IE and/or Java runtime is 64-bit. Some background: I installed 64-bit Win 7, and IE installed automatically with it from CD; I didn't download IE. I did download Java runtime. Mouseover tips in Control Panel!Programs shows it as: "Java 32-bit Java(TM) Control Panel" Then I went to http://java.com/en/download/manual.jsp and that page says... We have detected you may be viewing this page in a 32-bit browser. If you use 32-bit and 64-bit browsers interchangeably, you will need to install both 32-bit and 64-bit Java in order to have the Java plug-in for both browsers. But I cannot tell in the aftermath whether my Java is 64-bit. Evidently the "Java(TM) Control Panel" is, but I don't know if that's the same as the runtime. (I'm afraid to ask on the offical Java forums, because they're such a-holes.) Also, How do I issue a command to the OS to tell whether this IE is 64-bit? Help!About doesn't say on that. Thanks.

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• Undefined Variable? But I defined it...

  - by Rob

  Well before anyone claims that theres a duplicate question... (I've noticed that people who can't answer the question tend to run and look for a duplicate, and then report it.) Here is the duplicate you are looking for: http://stackoverflow.com/questions/2481382/php-claims-my-defined-variable-is-undefined However, this isn't quite a duplicate. It gives me a solution, but I'm not really looking for this particular solution. Here is my problem: Notice: Undefined variable: custom Now here is my code: $headers = apache_request_headers(); // Request the visitor's headers. $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; //This is what the header should be. foreach ($headers as $header => $value) { $custom .= "$header: $value"; } Clearly, $custom is defined. According to the other question, it's a global and should be marked as one. But how is it a global? And how can I make it a (non-global)? The script works fine, it still displays what its supposed to and acts correctly, but when I turn on error messages, it simply outputs that notice as well. I suppose its not currently necessary to fix it, but I'd like to anyway, as well as know why its doing this.

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