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• Error "initializer element is not constant" when trying to initialize variable with const

  - by tomlogic

  I get an error on line 6 (initialize my_foo to foo_init) of the following program and I'm not sure I understand why. typedef struct foo_t { int a, b, c; } foo_t; const foo_t foo_init = { 1, 2, 3 }; foo_t my_foo = foo_init; int main() { return 0; } Keep in mind this is a simplified version of a larger, multi-file project I'm working on. The goal was to have a single constant in the object file, that multiple files could use to initialize a state structure. Since it's an embedded target with limited resources and the struct isn't that small, I don't want multiple copies of the source. I'd prefer not to use: #define foo_init { 1, 2, 3 } I'm also trying to write portable code, so I need a solution that's valid C89 or C99. Does this have to do with the ORGs in an object file? That initialized variables go into one ORG and are initialized by copying the contents of a second ORG? Maybe I'll just need to change my tactic, and have an initializing function do all of the copies at startup. Unless there are other ideas out there?

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• Low Throughput on Windows Named Pipe Over WAN

  - by MichaelB76

  I'm having problems with low performance using a Windows named pipe. The throughput drops off rapidly as the network latency increases. There is a roughly linear relationship between messages sent per second and round trip time. It seems that the client must ack each message before the server will send the next one. This leads to very poor performance, I can only send 5 (~100 byte) messages per second over a link with an RTT of 200 ms. The pipe is asynchronous, using multiple overlapped write operations (and multiple overlapped reads at the client end), but this is not improving throughput. Is it possible to send messages in parallel over a named pipe? The pipe is created using PIPE_TYPE_MESSAGE, would PIPE_READMODE_BYTE work better? Is there any other way I can improve performance? This is a deployed solution, so I can't simply replace the pipe with a socket connection (I've read that Windows named pipe aren't recommended for use over a WAN, and I'm wondering if this is why). I'd be grateful for any help with this matter.

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• Help with simple javascript loop

  - by Gabriel

  Hello, I have a simple javascript that I'd like to loop for multiple elements. Here's my code: <script type='text/javascript'> for(i = 1; i < 100; i++) { $('#link'+i).click(function() { $('#container').removeClass(); $('#container').addClass('templateid'+i); }); } </script> What I'd like to achieve is the same addClass function for multiple id's (e.g. link2, link3, link4), with the corresponding class (e.g. template2, template3, template4). Any help would be hugely appreciated! For reference, an individual call like this one, does work, so I don't see why the loop above doesn't function the same: <script type='text/javascript'> $('#link2').click(function() { $('#container').removeClass(); $('#container').addClass('templateid2'); }); </script>

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• In Rails, how to respect :scope when using validates_uniqueness_of in an embedded object form?

  - by mkirk

  I have a Book model, which has_many Chapters (which belong_to a Book). I want to ensure uniqueness of Chapter titles, but only within the scope of a single book. The catch is that the form for creating chapters is embedded in the Book model's form (The Book model accepts_nested_attributes_for :chapters). Within the Chapter model: validates_uniqueness_of( :chapter_title, :scope = :book_id, :case_sensitive = false, :message = "No book can have multiple chapters with the same title.") However, when I submit the Book creation form (which also includes multiple embedded Chapter forms), if the chapter title exists in another chapter for a different book, I fail the validation test. Book.create( :chapters => [ Chapter.new(:title => "Introduction"), Chapter.new(:title => "How to build things") => Book 1 successfully created Book.create( :chapters => [ Chapter.new(:title => "Introduction"), Chapter.new(:title => "Destroy things") => Book 2 fails to validate second_book = Book.create( :chapters => [ Chapter.new(:title => "A temporary Introduction title"), Chapter.new(:title => "Destroy things") => Book 2 succesfully created second_book.chapters[0].title= "Introduction" => success second_book.chapters.save => success second_book.save => success Can anyone shed some light on how to do this? Or why it's happening?

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• initialize jquery slider with hidden input value from database.

  - by ludwigs3rd

  I'm using a slider as user input for a screen. Basically it's a bulk update screen where there is a table with multiple rows, thus multiple sliders. I created it so that the hidden value is what gets posted in the form. <td> <input class="percentageProvidedHidden" type="hidden" name='<%= "Values[" + i + "].Percentage" %>' value='<%=item.Percentage %>' /> <div class="percentageProvidedSlider"></div> </td> I have the update working just fine (move slider changes hidden input value, submit, values are updated in db), however, I can't get the damn thing to initialize with the value of the hidden input (note the "value: " parameter below). In this case I think $(this) isn't actually $('percentageProvidedSlider') but the page itself. Can someone help me get the slider value to initialize with the hidden input field? I'm using ASP .Net MVC 2 so if there are any methods I should try with that I welcome them as well. $('.percentageProvidedSlider').slider( { min: 0, max: 100, step: 25, value: $(this).parents('tr').find('input.percentageProvidedHidden').val(), slide: function(e, ui) { var mypos = ui.value; $(this).find('.ui-slider-handle').text(ui.value); }, change: function(event, ui) { var myVal = $(this).slider("option", "value"); $(this).parents('tr').find('input.percentageProvidedHidden').val(myVal); var myDropDown = $(this).parents('tr').find('select.verified'); } });

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• Good C++ array class for dealing with large arrays of data in a fast and memory efficient way?

  - by Shane MacLaughlin

  Following on from a previous question relating to heap usage restrictions, I'm looking for a good standard C++ class for dealing with big arrays of data in a way that is both memory efficient and speed efficient. I had been allocating the array using a single malloc/HealAlloc but after multiple trys using various calls, keep falling foul of heap fragmentation. So the conclusion I've come to, other than porting to 64 bit, is to use a mechanism that allows me to have a large array spanning multiple smaller memory fragments. I don't want an alloc per element as that is very memory inefficient, so the plan is to write a class that overrides the [] operator and select an appropriate element based on the index. Is there already a decent class out there to do this, or am I better off rolling my own? From my understanding, and some googling, a 32 bit Windows process should theoretically be able address up to 2GB. Now assuming I've 2GB installed, and various other processes and services are hogging about 400MB, how much usable memory do you think my program can reasonably expect to get from the heap? I'm currently using various flavours of Visual C++.

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• Considering moving from Java/Spring MVC to Grails

  - by MDS

  I'm currently using Java & Spring (MVC) to create a webapp, and I'm considering moving to Grails. I'd appreciate feedback/insight on the following: I have multiple application contexts in the current Java/Spring webapp that I load through the web.xml ContextLoaderListener; is it possible to have multiple application contexts in Grails? If, yes, how? This webapp extensively uses a CXF restful web service and the current Java/Spring webapp uses the bundled CXF HTTP client. Can I continue to use the (Java) CXF HTTP Client in Grails? I implemented Spring Security using a custom implementation of UserDetails and UserDetailsService, can I re-use these implementations in Grails "as is" or must I re-implement them? There is an instance where I've relied on Spring's jdbc template (rather than the available ORM) and an additional data source I defined in app context, can I re-use this in Grails? I plan on using Maven as the project management tool; are there any issues of using Maven with Grails where there is a combination of groovy and java?

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• Why doesn't Firefox redownload images already on a page?

  - by vvo

  Hello, i just read this article : https://developer.mozilla.org/en/HTTP_Caching_FAQ There's a firefox behavior (and some other browsers i guess) i'd like to understand : if i take any webpage and try to insert the same image multiple times in javascript, the image is only downloaded ONCE even if i specifiy all needed headers to say "do no ever use cache". (see article) I know there are workarounds (like addind query strings to end of urls etc) but why do firefox act like that, if i say that an image do not have to be cached, why is the image still taken from cache when i try to re-insert it ? Plus, what cache is used for this ? (I guess it's the memory cache) Is this behavior the same for dynamic inclusion for example ? ANSWSER IS NO :) I just tested it and the same headers for a js script will make firefox redownload it each time you append the script to the DOM. PS: I know you're wondering WHY i need to do that (appending same image multiple times and force to redownload but this is the way our app works) thank you The good answer is : firefox will store images for the current page load in the memory cache even if you specify he doesnt have to cache them. You can't change this behavior but this is odd because it's not the same for javascript files for example Could someone explain or link to a document describing how firefox cache WORKS?

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• Displaying Query Results Horizontally

  - by AndyD273

  I am wondering if it is possible to take the results of a query and return them as a CSV string instead of as a column of cells. Basically, we have a table called Customers, and we have a table called CustomerTypeLines, and each Customer can have multiple CustomerTypeLines. When I run a query against it, I run into problems when I want to check multiple types, for instance: Select * from Customers a Inner Join CustomerTypeLines b on a.CustomerID = b.CustomerID where b.CustomerTypeID = 14 and b.CustomerTypeID = 66 ...returns nothing because a customer can't have both on the same line, obviously. In order to make it work, I had to add a field to Customers called CustomerTypes that looks like ,14,66,67, so I can do a Where a.CustomerTypes like '%,14,%' and a.CustomerTypes like '%,66,%' which returns 85 rows. Of course this is a pain because I have to make my program rebuild this field for that Customer each time the CustomerTypeLines table is changed. It would be nice if I could do a sub query in my where that would do the work for me, so instead of returning the results like: 14 66 67 it would return them like ,14,66,67, Is this possible?

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• How to get values from SQL query made by php?

  - by Ole Jak

  So I made a query like this global $connection; $query = "SELECT * FROM streams "; $streams_set = mysql_query($query, $connection); confirm_query($streams_set); in my DB there are filds ID, UID, SID, TIME (all INT type exept time) So I am triing to print query relult into form <form> <select class="multiselect" multiple="multiple" name="SIDs"> <?php global $connection; $query = "SELECT * FROM streams "; $streams_set = mysql_query($query, $connection); confirm_query($streams_set); $streams_count = mysql_num_rows($streams_set); for ($count=1; $count <= $streams_count; $count++) { echo "<option value=\"{$count}\""; echo ">{$count}</option>"; } ?> </select> <br/> <input type="submit" value="Submit Form"/> </form> How to print out as "option" "values" SID's from my sql query?

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• Two video card on one Mobo

  - by InfinityKing

  I recently purchased a new HP Pavilion p6-2265eo. It was then that I realised that it has only one DVI and one HDMI output.. I will connect my TV with the HDMI. so I am letft with only one DVI output. I need to have two monitors. Please help. Should I purchase a new video card and install it? My knowledge is limited. The specifications of my comp says that there is 1 x PCI-E x16, 3 x PCI-E x1. 1) I suppose that the video card already present in my purchase is connected on the PCI-E x16. Am I right? I dont want to open my desktop right now and check it for myself as it can void the warrenty. so I need an experienced person to tell me that. 2) I have an old nvidia geforce 7200 gt. Is it possible for me to connect it to my left over PCI-E x1? I searched for PCI-E x1 on the net and as far as I can understand the slot is too small for my old nvidia geforce 7200 gt graphic card. 3) what are the options? Please help this dummo :) Thankign you in advance,

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• How to use strtok in C properly so there is no memory leak?

  - by user246392

  I am somewhat confused by what happens when you call strtok on a char pointer in C. I know that it modifies the contents of the string, so if I call strtok on a variable named 'line', its content will change. Assume I follow the bellow approach: void function myFunc(char* line) { // get a pointer to the original memory block char* garbageLine = line; // Do some work // Call strtok on 'line' multiple times until it returns NULL // Do more work free(garbageLine); } Further assume that 'line' is malloced before it is passed to myFunc. Am I supposed to free the original string after using strtok or does it do the job for us? Also, what happens if 'line' is not malloced and I attempt to use the function above? Is it safer to do the following instead? (Assume the programmer won't call free if he knows the line is not malloced) Invocation char* garbageLine = line; myFunc(line); free(garbageLine); Function definition void function myFunc(char* line) { // Do some work // Call strtok on 'line' multiple times until it returns NULL // Do more work }

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• How to approach socket programming between C# -> Java (Android)

  - by Alex

  I've recently knocked up a server/client app for Windows & Android that allows one to send a file from Windows to an android phone over a socket connection. It works great for a single file but trying to send multiple files over in a single stream is causing me problems. I've also realised that aside from the binary data, I will need to send messages over the socket to indicate error states and other application messages. I have little experience with network programming and and wondering what is the best way forward. Basically the C# server side of the app just goes into a listening state and uses Socket.SendFile to transmit the file. On Android I use the standard Java Socket.getInputStream() to receive the file. That works great for a single file transfer, but how should I handle multiple files and error/messaging information? Do I need to use a different socket for each file? Should I be using a higher level framework to handle this or can I send everything over the single socket? Any other suggestions for frameworks or learning materials?

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• Problems Expanding an Array in C++

  - by dxq

  I'm writing a simulation for class, and part of it involves the reproduction of organisms. My organisms are kept in an array, and I need to increase the size of the array when they reproduce. Because I have multiple classes for multiple organisms, I used a template: template <class orgType> void expandarray(orgType* oldarray, int& numitems, int reproductioncount) { orgType *newarray = new orgType[numitems+reproductioncount]; for (int i=0; i<numitems; i++) { newarray[i] = oldarray[i]; } numitems += reproductioncount; delete[] oldarray; oldarray = newarray; newarray = NULL; } However, this template seems to be somehow corrupting my data. I can run the program fine without reproduction (commenting out the calls to expandarray), but calling this function causes my program to crash. The program does not crash DURING the expandarray function, but crashes on access violation later on. I've written functions to expand an array hundreds of times, and I have no idea what I screwed up this time. Is there something blatantly wrong in my function? Does it look right to you? EDIT: Thanks for everyone's help. I can't believe I missed something so obvious. In response to using std::vector: we haven't discussed it in class yet, and as silly as it seems, I need to write code using the methods we've been taught.

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• What db fits me?

  - by afvasd

  Dear Everyone I am currently using mysql. I am finding that my schema is getting incredibly complicated. I seek to find a new db that will suit my needs: Let's assume I am building a news aggregrator (which collects news from multiple website). I then run algorithms to determine if two news from different sites are actually referring to the same topic. I run this algorithm to cluster news together. The relationship is depicted below: cluster \--news1 \--word1 \--word2 \--news2 \--word3 \--news3 \--word1 \--word3 And then I will apply some magic and determine the importance of each word. Summing all the importance of each word gives me the importance of a news article. Summing the importance of each news article gives me the importance of a cluster. Note that above cluster there are also subgroups( like split by region etc), and categories (like sports, etc) which I have to determine the importance of that in a particular day per se. I have used views in the past to do so, but I realized that views are very slow. So i will normally do an insert into an actual table and index them for better performance. As you can see this leads to multiple tables derived like (cluster, importance), (news, importance), (words, importance) etc which can get pretty messy. Also the "importance" metric will change. It has become increasingly difficult to alter tables, update data (which I am using TRUNCATE TABLE) and then inserting from null. I am currently looking into something schemaless like Mongodb. I do not need distributedness. I would very much want something that is reasonably fast (which can be indexed) and something that is a lot more flexible that traditional RDMBS. Also, I need something that has some kind of ORM because I personally like ORM a lot. I am currently using sqlalchemy Please help!

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• What 20 Lines (or less) of code did you find really useful?

  - by Ygam

  You can share your code or other's code. Here's a snippet from an array function in Kohana: public static function rotate($source_array, $keep_keys = TRUE) { $new_array = array(); foreach ($source_array as $key => $value) { $value = ($keep_keys === TRUE) ? $value : array_values($value); foreach ($value as $k => $v) { $new_array[$k][$key] = $v; } } return $new_array; } It was helpful when I was uploading multiple images using multiple file upload forms. It turned this array array('images' => array( 'name' => array( 0 => 'img1', 1 => 'img0', 2 =>'img2' ), 'error' => array( 0 => '', 1 => '', 2 => '' into : array('images' => array( 0 => array( 'name' => 'img1' 'error' => '' ),//rest goes here How about you? What 20 or less lines of code did you find useful?

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• Page specific CSS or a single css file when developing a mobile (webkit) based site?

  - by Mike

  I am working on a mobile site for webkit browsers. I have been trying to find information on using multiple style sheets versus a single css file. There is a lot of information on this topic, but it not a lot of information pertaining to mobile browsers. My site will have a bunch of pages that while have page specific css. For a non-mobile site, it seems like generally people say that a single file will be faster, but that multiple files are easier to develop. However, on a mobile site is that still the case? If you put everything in one file, that will get cached after load, but that will make the first load slower. If you had page specific files, the first page would get loaded quicker, but every other page would then take a hit while making the page specific css http request. Does anyone have any thoughts on this? It sounds like they are saying one file is better as long as its under 1 MB (which my files def will)? http://www.yuiblog.com/blog/2010/07/12/mobile-browser-cache-limits-revisited/

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• Mercurial on shared network drive?

  - by user1164199

  Right now I have my repo on my local drive. In order to back it up, I have to copy .hg to a window's network drive. At Is it a good idea to put Mercurial Repository in shared Network drive?, Lasse Karlsen said the repo shouldn't be on a shared folder on a network server because "mercurial cannot reliably hold locks in all situations". Would this still be an issue when the repository is only updated by a single user? If so, can someone explain to me why the corruption happens? A while back our IT had problem setting up a mercurial server. I am very fond of mercurial (it has a great interface and is very easy to work with), but if it's going to be such a pain in the neck to set up for multiple users, I am willing to look for something else. Does anyone have any suggestions (with reasons)? I am looking for a revision control program that has the following attributes: 2. Good interface (allow you to easily see revision and changes to the code over multiple revisions). 3. Work as a local repo or a network repo. 4. IT will feel comfortable installing on their network. Thanks, Stephen

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• Add Your Gmail Account to Outlook 2010 Using IMAP

  - by Mysticgeek

  If you’re upgrading from Outlook 2003 to 2010, you might want to use IMAP with your Gmail account to synchronize mail across multiple machines. Using our guide, you will be able to start using it in no time. Enable IMAP in Gmail First log into your Gmail account and open the Settings panel. Click on the Forwarding and POP/IMAP tab and verify IMAP is enabled and save changes. Next open Outlook 2010, click on the File tab to access the Backstage view. Click on Account Settings and Add and remove accounts or change existing connection settings. In the Account Settings window click on the New button. Enter in your name, email address, and password twice then click Next. Outlook will configure the email server settings, the amount of time it takes will vary. Provided everything goes correctly, the configuration will be successful and you can begin using your account. Manually Configure IMAP Settings If the above instructions don’t work, then we’ll need to manually configure the settings. Again, go into Auto Account Setup and select Manually configure server settings or additional server types and click Next.   Select Internet E-mail – Connect to POP or IMAP server to send and receive e-mail messages. Now we need to manually enter in our settings similar to the following. Under the Server Information section verify the following. Account Type: IMAP Incoming mail server: imap.gmail.com Outgoing mail server (SMTP): smtp.gmail.com Note: If you have a Google Apps account make sure to put the full email address ([email protected]) in the Your Name and User Name fields. Note: If you live outside of the US you might need to use imap.googlemail.com and smtp.googlemail.com Next, we need to click on the More Settings button… In the Internet E-mail Settings screen that pops up, click on the Outgoing Server tab, and check the box next to My outgoing server (SMTP) requires authentication. Also select the radio button next to Use same settings as my incoming mail server. In the same window click on the Advanced tab and verify the following. Incoming server: 993 Incoming server encrypted connection: SSL Outgoing server encrypted connection TLS Outgoing server: 587 Note: You will need to change the Outgoing server encrypted connection first, otherwise it will default back to port 25. Also, if TLS doesn’t work, we were able to successfully use Auto. Click OK when finished. Now we want to test the settings, before continuing on…it’s just easier that way incase something was entered incorrectly. To make sure the settings are tested, check the box Test Account Settings by clicking the Next button. If you’ve entered everything in correctly, both tasks will be completed successfully and you can close out of the window. and begin using your account via Outlook 2010. You’ll get a final congratulations message you can close out of… And begin using your account via Outlook 2010. Conclusion Using IMAP allows you to synchronize email across multiple machines and devices. The IMAP feature in Gmail is free to use, and this should get you started using it with Outlook 2010. If you’re still using 2007 or just upgraded to it, check out our guide on how to use Gmail IMAP in Outlook 2007. Similar Articles Productive Geek Tips Add Your Gmail To Windows Live MailForce Outlook 2007 to Download Complete IMAP ItemsUse Gmail IMAP in Microsoft Outlook 2007Prevent Outlook with Gmail IMAP from Showing Duplicate Tasks in the To-Do BarSetting up Gmail IMAP Support for Windows Vista Mail TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips VMware Workstation 7 Acronis Online Backup DVDFab 6 Revo Uninstaller Pro Cool Looking Skins for Windows Media Player 12 Move the Mouse Pointer With Your Face Movement Using eViacam Boot Windows Faster With Boot Performance Diagnostics Create Ringtones For Your Android Phone With RingDroid Enhance Your Laptop’s Battery Life With These Tips Easily Search Food Recipes With Recipe Chimp

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• What is the Oracle Utilities Application Framework?

  - by Anthony Shorten

  The Oracle Utilities Application Framework is a reusable, scalable and flexible java based framework which allows other products to be built, configured and implemented in a standard way. Note: Even though the Framework is built in java it can be integrated with COBOL based extensions for backward compatibility. When Oracle Utilities Customer Care & Billing was migrated from V1 to V2, it was decided that the technical aspects of that product be separated to allow for reuse and independence from technical issues. The idea was that all the technical aspects would be concentrated in this separate product (i.e. a framework) and allow all products using the framework to concentrate on delivering superior functionality. The product was named the Oracle Utilities Application Framework (oufw is the product code). The technical components are contained in the Oracle Utilities Application Framework which can be summarized as follows: Metadata - The Oracle Utilities Application Framework is responsible for defining and using the metadata to define the runtime behavior of the product. All the metadata definition and management is contained within the Oracle Utilities Application Framework. UI Management - The Oracle Utilities Application Framework is responsible for defining and rendering the pages and responsible for ensuring the pages are in the appropriate format for the locale. Integration - The Oracle Utilities Application Framework is responsible for providing the integration points to the architecture. Refer to the Oracle Utilities Application Framework Integration Overview for more details Tools - The Oracle Utilities Application Framework provides a common set of facilities and tools that can be used across all products. Technology - The Oracle Utilities Application Framework is responsible for all technology standards compliance, platform support and integration. There are a number of products from the Tax and Utilities Global Business Unit as well as from the Financial Services Global Business Unit that are built upon the Oracle Utilities Application Framework. These products require the Oracle Utilities Application Framework to be installed first and then the product itself installed onto the framework to complete the installation process. There are a number of key benefits that the Oracle Utilities Application Framework provides to these products: Common facilities - The Oracle Utilities Application Framework provides a standard set of technical facilities that mean that products can concentrate in the unique aspects of their markets rather than making technical decisions. Common methods of configuration - The Oracle Utilities Application Framework standardizes the technical configuration process for a product. Customers can effectively reuse the configuration process across products. Multi-lingual and Multi-platform - The Oracle Utilities Application Framework allows the products to be offered in more markets and across multiple platforms for maximized flexibility. Common methods of implementation - The Oracle Utilities Application Framework standardizes the technical aspects of a product implementation. Customers can effectively reuse the technical implementation process across products. Quicker adoption of new technologies - As new technologies and standards are identified as being important for the product line, they can be integrated centrally benefiting multiple products. Cross product reuse - As enhancements to the Oracle Utilities Application Framework are identified by a particular product, all products can potentially benefit from the enhancement. Note: Use of the Oracle Utilities Application Framework does not preclude the introduction of product specific technologies or facilities to satisfy market needs. The framework minimizes the need and assists in the quick integration of a new product specific piece of technology (if necessary). The Framework is not available as a product itself and is bundled with Tax and Utilities Global Business Unit prodicts. At the present time the following products are on the Framework: Oracle Utilities Customer Care And Billing (V2 and above) Oracle Enterprise Taxation Management (V2 and above) Oracle Utilities Business Intelligence (V2 and above) Oracle Utilities Mobile Workforice Management (V2 and above)

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• Performance and Optimization Isn’t Evil

  - by Reed

  Donald Knuth is a fairly amazing guy.  I consider him one of the most influential contributors to computer science of all time.  Unfortunately, most of the time I hear his name, I cringe.  This is because it’s typically somebody quoting a small portion of one of his famous statements on optimization: “premature optimization is the root of all evil.” I mention that this is only a portion of the entire quote, and, as such, I feel that Knuth is being quoted out of context.  Optimization is important.  It is a critical part of every software development effort, and should never be ignored.  A developer who ignores optimization is not a professional.  Every developer should understand optimization – know what to optimize, when to optimize it, and how to think about code in a way that is intelligent and productive from day one. I want to start by discussing my own, personal motivation here.  I recently wrote about a performance issue I ran across, and was slammed by multiple comments and emails that effectively boiled down to: “You’re an idiot.  Premature optimization is the root of all evil.  This doesn’t matter.”  It didn’t matter that I discovered this while measuring in a profiler, and that it was a portion of my code base that can take “many hours to complete.”  Even so, multiple people instantly jump to “it’s premature – it doesn’t matter.” This is a common thread I see.  For example, StackOverflow has many pages of posts with answers that boil down to (mis)quoting Knuth.  In fact, just about any question relating to a performance related issue gets this quote thrown at it immediately – whether it deserves it or not.  That being said, I did receive some positive comments and emails as well.  Many people want to understand how to optimize their code, approaches to take, tools and techniques they can use, and any other advice they can discover. First, lets get back to Knuth – I mentioned before that Knuth is being quoted out of context.  Lets start by looking at the entire quote from his 1974 paper Structured Programming with go to Statements: “We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified.” Ironically, if you read Knuth’s original paper, this statement was made in the middle of a discussion of how Knuth himself had changed how he approaches optimization.  It was never a statement saying “don’t optimize”, but rather, “optimizing intelligently provides huge advantages.”  His approach had three benefits: “a) it doesn’t take long” … “b) the payoff is real”, c) you can “be less efficient in the other parts of my programs, which therefore are more readable and more easily written and debugged.” Looking at Knuth’s premise here, and reading that section of his paper, really leads to a few observations: Optimization is important  “he will be wise to look carefully at the critical code” Normally, 3% of your code – three lines out of every 100 you write, are “critical code” and will require some optimization: “we should not pass up our opportunities in that critical 3%” Optimization, if done well, should not be time consuming: “it doesn’t take long” Optimization, if done correctly, provides real benefits: “the payoff is real” None of this is new information.  People who care about optimization have been discussing this for years – for example, Rico Mariani’s Designing For Performance (a fantastic article) discusses many of the same issues very intelligently. That being said, many developers seem unable or unwilling to consider optimization.  Many others don’t seem to know where to start.  As such, I’m going to spend some time writing about optimization – what is it, how should we think about it, and what can we do to improve our own code.

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• Something for the weekend - Whats the most complex query?

  - by simonsabin

  Whenever I teach about SQL Server performance tuning I try can get across the message that there is no such thing as a table. Does that sound odd, well it isn't, trust me. Rather than tables you need to consider structures. You have 1. Heaps 2. Indexes (b-trees) Some people split indexes in two, clustered and non-clustered, this I feel confuses the situation as people associate clustered indexes with sorting, but don't associate non clustered indexes with sorting, this is wrong. Clustered and non-clustered indexes are the same b-tree structure(and even more so with SQL 2005) with the leaf pages sorted in a linked list according to the keys of the index.. The difference is that non clustered indexes include in their structure either, the clustered key(s), or the row identifier for the row in the table (see http://sqlblog.com/blogs/kalen_delaney/archive/2008/03/16/nonclustered-index-keys.aspx for more details). Beyond that they are the same, they have key columns which are stored on the root and intermediary pages, and included columns which are on the leaf level. The reason this is important is that this is how the optimiser sees the world, this means it can use any of these structures to resolve your query. Even if your query only accesses one table, the optimiser can access multiple structures to get your results. One commonly sees this with a non-clustered index scan and then a key lookup (clustered index seek), but importantly it's not restricted to just using one non-clustered index and the clustered index or heap, and that's the challenge for the weekend. So the challenge for the weekend is to produce the most complex single table query. For those clever bods amongst you that are thinking, great I will just use lots of xquery functions, sorry these are the rules. 1. You have to use a table from AdventureWorks (2005 or 2008) 2. You can add whatever indexes you like, but you must document these 3. You cannot use XQuery, Spatial, HierarchyId, Full Text or any open rowset function. 4. You can only reference your table once, i..e a FROM clause with ONE table and no JOINs 5. No Sub queries. The aim of this is to show how the optimiser can use multiple structures to build the results of a query and to also highlight why the optimiser is doing that. How many structures can you get the optimiser to use? As an example create these two indexes on AdventureWorks2008 create index IX_Person_Person on Person.Person (lastName, FirstName,NameStyle,PersonType) create index IX_Person_Person on Person.Person(BusinessentityId,ModifiedDate)with drop_existing    select lastName, ModifiedDate   from Person.Person  where LastName = 'Smith' You will see that the optimiser has decided to not access the underlying clustered index of the table but to use two indexes above to resolve the query. This highlights how the optimiser considers all storage structures, clustered indexes, non clustered indexes and heaps when trying to resolve a query. So are you up to the challenge for the weekend to produce the most complex single table query? The prize is a pdf version of a popular SQL Server book, or a physical book if you live in the UK.  

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• Silverlight Cream for March 24, 2010 -- #819

  - by Dave Campbell

  In this Issue: Nokola, Tim Heuer, Christian Schormann, Brad Abrams, David Kelley, Phil Middlemiss, Michael Klucher, Brandon Watson, Kunal Chowdhury, Jacek Ciereszko, and Unni. Shoutouts: Michael Klucher has a short post up For Love of the Game (Development)…, where he's looking for some input from the developer community. Shawn Hargreaves has a link post up of all the Windows Phone MIX10 presentations Chris Cavanagh has a Soft-Body Physics for Windows Phone 7 post up that goes along with one he did 1-1/2 years ago! Jeff Weber posted An Open Letter To Microsoft Regarding The Silverlight Game Development Community Pete Brown posted his MIX10 Recap ... lots of information, and discussion of what he was up to ... I liked the Trivia app Pete... glad to hear that was yours :) I've changed my mind and added a WP7 tag to SilverlightCream. I'll straighten out all the Mobile plus Silverlight links to point at the WP7 tab hopefully tonight. From SilverlightCream.com: EasyPainter Source Pack 3: Adorners, Mouse Cursors and Frames Nokola has been busy with EasyPainter adding in Custom, Extensible Mouse Cursors and Customizable Adorners with extensible adorner frames, and best of all... all with source code! Simulate Geo Location in Silverlight Windows Phone 7 emulator Among the things we don't have in our WP7 emulators is Geo Location... Tim Heuer comes to the rescue with a simulator for it... too cool, Tim! Blend 4: About Path Layout, Part II Christian Schormann is back with Part 2 of his tutorial sequence on the new Path Layout. Really good info and definitely cool presentations of the control. Silverlight 4 + RIA Services - Ready for Business: Exposing OData Services Brad Abrams continues his series with a post on exposing OData services. This looks like a great tutorial on the topic... will probably resolve some questions I've been having :) No Silverlight and Preloader Experience(ish) - in 10 seconds... David Kelley exposes the code he uses on his site, designed to be friendly to Silverlight and non-Silverlight users alike. Merged Dictionaries of Style Resources and Blend Phil Middlemiss has a nice article up on Merged Dictionaries and using multiple resource dictionaries that the app chooses, but also be compatible with Prism and Blend while not eating your system resources out of house and home. XNA Game Studio and Windows Phone Emulator Compatibility Michael Klucher has a definitive post up about getting your XNA and system up-to-speed for WP7... a must-read if you've been running any of the other XNA drops. Windows Phone 7 301 Redirect Bug Brandon Watson reports a 301 Redirect bug on WP7 ... see the code and how he got it, then follow along as he explains all the debug paths he took and what the resolution (?) really is :) Silverlight 4: How to use the new Printing API? Kunal Chowdhury has a tutorial up on printing with Silverlight 4 RC... from the project layout to printing and then printing a smaller section... all good Printing problem in Silverlight 4.0 RC - loading images in code behind Jacek Ciereszko also is writing about printing, and in his case he had problems with loading an image dynamically and printing it... plus he provides a solution to the 'blank page' problem. ToolboxExampleAttribute - a new extension point in Blend 4 (and a few other extensibility related changes) Unni has an article up about Expression Blend 4's new ToolboxExampleAttribute which allow you to have multiple examples of the same type resulting in different XAML produced. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone    MIX10

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• T-SQL Improvements And Data Types in ms sql 2008

  - by Aamir Hasan

   Microsoft SQL Server 2008 is a new version released in the first half of 2008 introducing new properties and capabilities to SQL Server product family. All these new and enhanced capabilities can be defined as the classic words like secure, reliable, scalable and manageable. SQL Server 2008 is secure. It is reliable. SQL2008 is scalable and is more manageable when compared to previous releases. Now we will have a look at the features that are making MS SQL Server 2008 more secure, more reliable, more scalable, etc. in details.Microsoft SQL Server 2008 provides T-SQL enhancements that improve performance and reliability. Itzik discusses composable DML, the ability to declare and initialize variables in the same statement, compound assignment operators, and more reliable object dependency information. Table-Valued ParametersInserts into structures with 1-N cardinality problematicOne order -> N order line items"N" is variable and can be largeDon't want to force a new order for every 20 line itemsOne database round-trip / line item slows things downNo ARRAY data type in SQL ServerXML composition/decomposition used as an alternativeTable-valued parameters solve this problemTable-Valued ParametersSQL Server has table variablesDECLARE @t TABLE (id int);SQL Server 2008 adds strongly typed table variablesCREATE TYPE mytab AS TABLE (id int);DECLARE @t mytab;Parameters must use strongly typed table variables Table Variables are Input OnlyDeclare and initialize TABLE variable  DECLARE @t mytab;  INSERT @t VALUES (1), (2), (3);  EXEC myproc @t;Procedure must declare variable READONLY  CREATE PROCEDURE usetable (    @t mytab READONLY ...)  AS    INSERT INTO lineitems SELECT * FROM @t;    UPDATE @t SET... -- no!T-SQL Syntax EnhancementsSingle statement declare and initialize  DECLARE @iint = 4;Compound Assignment Operators  SET @i += 1;Row constructors  DECLARE @t TABLE (id int, name varchar(20));  INSERT INTO @t VALUES    (1, 'Fred'), (2, 'Jim'), (3, 'Sue');Grouping SetsGrouping Sets allow multiple GROUP BY clauses in a single SQL statementMultiple, arbitrary, sets of subtotalsSingle read pass for performanceNested subtotals provide ever better performanceGrouping Sets are an ANSI-standardCOMPUTE BY is deprecatedGROUPING SETS, ROLLUP, CUBESQL Server 2008 - ANSI-syntax ROLLUP and CUBEPre-2008 non-ANSI syntax is deprecatedWITH ROLLUP produces n+1 different groupings of datawhere n is the number of columns in GROUP BYWITH CUBE produces 2^n different groupingswhere n is the number of columns in GROUP BYGROUPING SETS provide a "halfway measure"Just the number of different groupings you needGrouping Sets are visible in query planGROUPING_ID and GROUPINGGrouping Sets can produce non-homogeneous setsGrouping set includes NULL values for group membersNeed to distinguish by grouping and NULL valuesGROUPING (column expression) returns 0 or 1Is this a group based on column expr. or NULL value?GROUPING_ID (a,b,c) is a bitmaskGROUPING_ID bits are set based on column expressions a, b, and cMERGE StatementMultiple set operations in a single SQL statementUses multiple sets as inputMERGE target USING source ON ...Operations can be INSERT, UPDATE, DELETEOperations based onWHEN MATCHEDWHEN NOT MATCHED [BY TARGET] WHEN NOT MATCHED [BY SOURCE]More on MERGEMERGE statement can reference a $action columnUsed when MERGE used with OUTPUT clauseMultiple WHEN clauses possible For MATCHED and NOT MATCHED BY SOURCEOnly one WHEN clause for NOT MATCHED BY TARGETMERGE can be used with any table sourceA MERGE statement causes triggers to be fired onceRows affected includes total rows affected by all clausesMERGE PerformanceMERGE statement is transactionalNo explicit transaction requiredOne Pass Through TablesAt most a full outer joinMatching rows = when matchedLeft-outer join rows = when not matched by targetRight-outer join rows = when not matched by sourceMERGE and DeterminismUPDATE using a JOIN is non-deterministicIf more than one row in source matches ON clause, either/any row can be used for the UPDATEMERGE is deterministicIf more than one row in source matches ON clause, its an errorKeeping Track of DependenciesNew dependency views replace sp_dependsViews are kept in sync as changes occursys.dm_sql_referenced_entitiesLists all named entities that an object referencesExample: which objects does this stored procedure use?sys.dm_sql_referencing_entities 

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• SQL SERVER – Reducing CXPACKET Wait Stats for High Transactional Database

  - by pinaldave

  While engaging in a performance tuning consultation for a client, a situation occurred where they were facing a lot of CXPACKET Waits Stats. The client asked me if I could help them reduce this huge number of wait stats. I usually receive this kind of request from other client as well, but the important thing to understand is whether this question has any merits or benefits, or not. Before we continue the resolution, let us understand what CXPACKET Wait Stats are. The official definition suggests that CXPACKET Wait Stats occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if a conflict concerning this wait type develops into a problem. (from BOL) In simpler words, when a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. Threads which came first have to wait for the slower thread to finish. The Wait by a specific completed thread is called CXPACKET Wait Stat. Note that CXPACKET Wait is done by completed thread and not the one which are unfinished. “Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is also unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query.” Now let us see what the best practices to reduce the CXPACKET Wait Stats are. The suggestions, with which you will find that if you search online through the browser, would play a major role as and might be asked about their jobs In addition, might tell you that you should set ‘maximum degree of parallelism’ to 1. I do agree with these suggestions, too; however, I think this is not the final resolutions. As soon as you set your entire query to run on single CPU, you will get a very bad performance from the queries which are actually performing okay when using parallelism. The best suggestion to this is that you set ‘the maximum degree of parallelism’ to a lower number or 1 (be very careful with this – it can create more problems) but tune the queries which can be benefited from multiple CPU’s. You can use query hint OPTION (MAXDOP 0) to run the server to use parallelism. Here is the two-quick script which helps to resolve these issues: Change MAXDOP at Server Level EXEC sys.sp_configure N'max degree of parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Run Query with all the CPU (using parallelism) USE AdventureWorks GO SELECT * FROM Sales.SalesOrderDetail ORDER BY ProductID OPTION (MAXDOP 0) GO Below is the blog post which will help you to find all the parallel query in your server. SQL SERVER – Find Queries using Parallelism from Cached Plan Please note running Queries in single CPU may worsen your performance and it is not recommended at all. Infect this can be very bad advise. I strongly suggest that you identify the queries which are offending and tune them instead of following any other suggestions. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, SQLAuthority News, T SQL, Technology

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