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• C++ copy-construct construct-and-assign question

  - by Andy

  Blockquote Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is accomplished through a direct invocation of Y::Y(int). The initializations of b and c are more complex. In fact, they're too complex. These are both copy initializations. In the case of the initialization of b, we're requesting the creation of an anonymous temporary of type Y, initialized with the value 1066. We then use this anonymous temporary as a parameter to the copy constructor for class Y to initialize b. Finally, we call the destructor for the anonymous temporary. To test this, I did a simple class with a data member (program attached at the end) and the results were surprising. It seems that for the case of b, the object was constructed by the copy constructor rather than as suggested in the book. Does anybody know if the language standard has changed or is this simply an optimisation feature of the compiler? I was using Visual Studio 2008. Code sample: #include <iostream> class Widget { std::string name; public: // Constructor Widget(std::string n) { name=n; std::cout << "Constructing Widget " << this->name << std::endl; } // Copy constructor Widget (const Widget& rhs) { std::cout << "Copy constructing Widget from " << rhs.name << std::endl; } // Assignment operator Widget& operator=(const Widget& rhs) { std::cout << "Assigning Widget from " << rhs.name << " to " << this->name << std::endl; return *this; } }; int main(void) { // construct Widget a("a"); // copy construct Widget b(a); // construct and assign Widget c("c"); c = a; // copy construct! Widget d = a; // construct! Widget e = "e"; // construct and assign Widget f = Widget("f"); return 0; } Output: Constructing Widget a Copy constructing Widget from a Constructing Widget c Assigning Widget from a to c Copy constructing Widget from a Constructing Widget e Constructing Widget f Copy constructing Widget from f I was most surprised by the results of constructing d and e.

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• Problem with incomplete type while trying to detect existence of a member function

  - by abir

  I was trying to detect existence of a member function for a class where the function tries to use an incomplete type. The typedef is struct foo; typedef std::allocator<foo> foo_alloc; The detection code is struct has_alloc { template<typename U,U x> struct dummy; template<typename U> static char check(dummy<void* (U::*)(std::size_t),&U::allocate>*); template<typename U> static char (&check(...))[2]; const static bool value = (sizeof(check<foo_alloc>(0)) == 1); }; So far I was using incomplete type foo with std::allocator without any error on VS2008. However when I replaced it with nearly an identical implementation as template<typename T> struct allocator { T* allocate(std::size_t n) { return (T*)operator new (sizeof(T)*n); } }; it gives an error saying that as T is incomplete type it has problem instantiating allocator<foo> because allocate uses sizeof. GCC 4.5 with std::allocator also gives the error, so it seems during detection process the class need to be completely instantiated, even when I am not using that function at all. What I was looking for is void* allocate(std::size_t) which is different from T* allocate(std::size_t). My questions are (I have three questions, but as they are correlated , so I thought it is better not to create three separate questions). Why MS std::allocator doesn't check for incomplete type foo while instantiating? Are they following any trick which can be implemented ? Why the compiler need to instantiate allocator<T> to check the existence of the function when sizeof is not used as sfinae mechanism to remove/add allocate in the overload resolutions set? It should be noted that, if I remove the generic implementation of allocate leaving the declaration only, and specialized it for foo afterwards such as struct foo{}; template< struct allocator { foo* allocate(std::size_t n) { return (foo*)operator new (sizeof(foo)*n); } }; after struct has_alloc it compiles in GCC 4.5 while gives error in VS2008 as allocator<T> is already instantiated and explicit specialization for allocator<foo> already defined. Is it legal to use nested types for an std::allocator of incomplete type such as typedef foo_alloc::pointer foo_pointer; ? Though it is practically working for me, I suspect the nested types such as pointer may depend on completeness of type it takes. It will be good to know if there is any possible way to typedef such types as foo_pointer where the type pointer depends on completeness of foo. NOTE : As the code is not copy paste from editor, it may have some syntax error. Will correct it if I find any. Also the codes (such as allocator) are not complete implementation, I simplified and typed only the portion which I think useful for this particular problem.

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• Using javascript, show a certain amount of divs based on an answer

  - by Adam

  I'm building a form that first asks if you have 'foo'. If the answer is 'Yes', a div appears and asks 'How many foo do you have'? Based on the quantity answered, I'd like to show only that many divs. Thus if the user answers 1, only the first div will show. If they answer three, the first three will show. I have it set so that if the user answers no, the question of the amount remains hidden, but if they answer yes, they would be prompted for the quantity. This is what I've got so far... <script type="text/javascript"> $(document).ready(function(){ $(window).load(function() { $('#amt_of_foo,.foo_panels').hide(); }); $('#yes_foo').click(function() { $('#amt_of_foo').show(); }); $('#no_foo').click(function() { $('.foo_panels,#amt_of_foo').hide(); }); }); </script> </head> <body> <ul> <li> <div class="panel section_panel"> <h2>Questions About Your Foo</h2> <span>Do you have foo?:</span> <input type="radio" name="foo" id="no_foo" /> No <br /> <input type="radio" name="foo" id="yes_foo" /> Yes:</span></span> <span id="amt_of_foo"> <span>How many foo do you have?:</span> <span><input id="qty_of_foo" type="text" size="5" /> </span> </span> </div> </li> <!--answered yes to foo, and entered amount--> <div class="foo_panels"> <li> <li> <div class="panel foo_1"> <h1>First foo's information</h1> <span>Foo name:&nbsp;<input type="text" size="20" /></span> </div> </li> <li> <div class="panel foo_2"> <h1>Second foo's information</h1> <span>Foo name:&nbsp;<input type="text" size="20" /></span> </div> </li> <li> <div class="panel foo_3"> <h1>Third foo's information</h1> <span>Foo name:&nbsp;<input type="text" size="20" /></span> </div> </li> </div> <!--answered no to foo--> <li> <div class="panel"> <h1>Next Question, if no foo</h1> </div> </li> </ul> The ul is used for a jQuery 'slider' plugin. the 'panel' class is used for global css.

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• output image is not displayed

  - by gerry chocolatos

  so, im doing an image detection which i have to process on each red, green, n blue element to get the edge map and combine them become one to show the output. but it doesnt show my output image would anyone pls be kind enough to help me? here is my code so far. //get the red element process_red = new int[width * height]; counter = 0; for(int i = 0; i < 256; i++) { for(int j = 0; j < 256; j++) { int clr = buff_red.getRGB(j, i); int red = (clr & 0x00ff0000) >> 16; red = (0xFF<<24)|(red<<16)|(red<<8)|red; process_red[counter] = red; counter++; } } //set threshold value for red element int threshold = 100; for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { int bin = (buff_red.getRGB(x, y) & 0x000000ff); if (bin < threshold) bin = 0; else bin = 255; buff_red.setRGB(x,y, 0xff000000 | bin << 16 | bin << 8 | bin); } } and i do the same way for my green n blue elements. and then i wanted to get to combination of the three by doing it this way: //combine the three elements process_combine = new int[width * height]; counter = 0; for(int i = 0; i < 256; i++) { for(int j = 0; j < 256; j++) { int clr_a = buff_red.getRGB(j, i); int ar = clr_a & 0x000000ff; int clr_b = buff_green.getRGB(j, i); int bg = clr_b & 0x000000ff; int clr_c = buff_blue.getRGB(j, i); int cb = clr_b & 0x000000ff; int alpha = 0xff000000; int combine = alpha|(ar<<16)|(bg<<8)|cb; process_combine[counter] = combine; counter++; } } buff_rgb = new BufferedImage(width,height, BufferedImage.TYPE_INT_ARGB); Graphics rgb; rgb = buff_rgb.getGraphics(); rgb.drawImage(output_rgb, 0, 0, null); rgb.dispose(); repaint(); and to show the output whic is from the combining process, i use a draw method: g.drawImage(buff_rgb,800,100,this); but still it doesnt show the image. can anyone pls help me? ur help is really appreciated. thanks.

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• Draw camera position in specific view port.

  - by snackbar

  Most of this code should be fairly self explanatory. I got an display function and my view port function. There are two modes which is 4 small view ports in the window or one large. I got one camera which can be moved and if in 4 view port mode just 3 fixed angles. The thing is I want the free moving cameras position to be displayed in the 3 other view ports. I tried doing it by drawing spheres using opengl but the problem is that then the position gets draw in the free roaming camera too as it shows the same scene. It doesn't have to be a sphere, just something simple that represents the cameras spacial position in these three other views. Drawing the scene once with camera object showing for the three viewports, render to texture. Clear and draw scene without camera object render to texture and then stitch these together before actually drawing the scene seems like a lot o work for something that should be easy. void display(int what) { if(what==5){ glMatrixMode(GL_MODELVIEW); glLoadIdentity(); camControll();} if(what==1){ glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt(75,15,-5,0,5,-5,0,1,0);} if(what==2){ glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt(0,110,0,0,0,0,1,0,0);} if(what==3){ glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, float(320) / float(240), 0.1f, 100.0f); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); camControll();} if(what==4){ glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt(185,75,25,0,28,0,0,1,0);} glClearColor(0, 0, 0, 1); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); drawScene(); drawCamera(); glutSwapBuffers(); } void viewport(){ glEnable(GL_SCISSOR_TEST); if(!divided_view_port) { glViewport(0, 0, w, h); glScissor(0,0,640,480); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, w / h, 0.1f, 100.0f); display(5); } else { ////////////////////// bottom left - working glViewport(0, 0, w/2, h/2); glScissor(0,0,w/2,h/2); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, w / h, 0.1f, 300.0f); display(1); ////////////////////// ////////////////////// top right - working glViewport(w/2, h/2, w/2, h/2); glScissor(w/2,h/2,w/2,h/2); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, w / h, 0.1f, 300.0f); display(2); ////////////////////// ////////////////////// bottom right -working glViewport(w/2, 0, w/2, h/2); glScissor(w/2,0,w/2,h/2); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, w / h, 0.1f, 300.0f); display(3); //////////////////////// ////////////////////////// top left glViewport(0, h/2, w/2, h/2); glScissor(0,h/2,w/2,h/2); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, w / h, 0.1f, 300.0f); display(4); /////////////////////////// } glDisable(GL_SCISSOR_TEST); glMatrixMode(GL_MODELVIEW); }

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• Calculate the number of ways to roll a certain number

  - by helloworld

  I'm a high school Computer Science student, and today I was given a problem to: Program Description: There is a belief among dice players that in throwing three dice a ten is easier to get than a nine. Can you write a program that proves or disproves this belief? Have the computer compute all the possible ways three dice can be thrown: 1 + 1 + 1, 1 + 1 + 2, 1 + 1 + 3, etc. Add up each of these possibilities and see how many give nine as the result and how many give ten. If more give ten, then the belief is proven. I quickly worked out a brute force solution, as such int sum,tens,nines; tens=nines=0; for(int i=1;i<=6;i++){ for(int j=1;j<=6;j++){ for(int k=1;k<=6;k++){ sum=i+j+k; //Ternary operators are fun! tens+=((sum==10)?1:0); nines+=((sum==9)?1:0); } } } System.out.println("There are "+tens+" ways to roll a 10"); System.out.println("There are "+nines+" ways to roll a 9"); Which works just fine, and a brute force solution is what the teacher wanted us to do. However, it doesn't scale, and I am trying to find a way to make an algorithm that can calculate the number of ways to roll n dice to get a specific number. Therefore, I started generating the number of ways to get each sum with n dice. With 1 die, there is obviously 1 solution for each. I then calculated, through brute force, the combinations with 2 and 3 dice. These are for two: There are 1 ways to roll a 2 There are 2 ways to roll a 3 There are 3 ways to roll a 4 There are 4 ways to roll a 5 There are 5 ways to roll a 6 There are 6 ways to roll a 7 There are 5 ways to roll a 8 There are 4 ways to roll a 9 There are 3 ways to roll a 10 There are 2 ways to roll a 11 There are 1 ways to roll a 12 Which looks straightforward enough; it can be calculated with a simple linear absolute value function. But then things start getting trickier. With 3: There are 1 ways to roll a 3 There are 3 ways to roll a 4 There are 6 ways to roll a 5 There are 10 ways to roll a 6 There are 15 ways to roll a 7 There are 21 ways to roll a 8 There are 25 ways to roll a 9 There are 27 ways to roll a 10 There are 27 ways to roll a 11 There are 25 ways to roll a 12 There are 21 ways to roll a 13 There are 15 ways to roll a 14 There are 10 ways to roll a 15 There are 6 ways to roll a 16 There are 3 ways to roll a 17 There are 1 ways to roll a 18 So I look at that, and I think: Cool, Triangular numbers! However, then I notice those pesky 25s and 27s. So it's obviously not triangular numbers, but still some polynomial expansion, since it's symmetric. So I take to Google, and I come across this page that goes into some detail about how to do this with math. It is fairly easy(albeit long) to find this using repeated derivatives or expansion, but it would be much harder to program that for me. I didn't quite understand the second and third answers, since I have never encountered that notation or those concepts in my math studies before. Could someone please explain how I could write a program to do this, or explain the solutions given on that page, for my own understanding of combinatorics? EDIT: I'm looking for a mathematical way to solve this, that gives an exact theoretical number, not by simulating dice

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• Break in Class Module vs. Break on Unhandled Errors (VB6 Error Trapping, Options Setting in IDE)

  - by Erx_VB.NExT.Coder

  Basically, I'm trying to understand the difference between the "Break in Class Module" and "Break on Unhandled Errors" that appear in the Visual Basic 6.0 IDE under the following path: Tools --> Options --> General --> Error Trapping The three options appear to be: Break on All Errors Break in Class Module Break on Unhandled Errors Now, apparently, according to MSDN, the second option (Break in Class Module) really just means "Break on Unhandled Errors in Class Modules". Also, this option appears to be set by default (ie: I think its set to this out of the box). What I am trying to figure out is, if I have the second option selected, do I get the third option (Break on Unhandled Errors) for free? In that, does it come included by default for all scenarios outside of the Class Module spectrum? To advise, I don't have any Class Modules in my currently active project. I have .bas modules though. Also, is it possible that by Class Mdules they may be referring to normal .bas Modules as well? (this is my second sub-question). Basically, I just want the setting to ensure there won't be any surprises once the exe is released. I want as many errors to display as possible while I am developing, and non to be displayed when in release mode. Normally, I have two types of On Error Resume Next on my forms where there isn't explicit error handling, they are as follows: On Error Resume Next ' REQUIRED On Error Resume Next ' NOT REQUIRED The required ones are things like, checking to see if an array has any length, if a call to its UBound errors out, that means it has no length, if it returns a value 0 or more, then it does have length (and therefore, exists). These types of Error Statements need to remain active even while I am developing. However, the NOT REQUIRED ones shouldn't remain active while I am developing, so I have them all commented out to ensure that I catch all the errors that exist. Once I am ready to release the exe, I do a CTRL+H to find all occurrences of: 'On Error Resume Next ' NOT REQUIRED (You may have noticed they are commented out)... And replace them with: On Error Resume Next ' NOT REQUIRED ... The uncommented version, so that in release mode, if there are any leftover errors, they do not show to users. For more on the description by MSDN on the three options (which I've read twice and still don't find adequate) you can visit the following link: http://webcache.googleusercontent.com/search?q=cache:yUQZZK2n2IYJ:support.microsoft.com/kb/129876&hl=en&lr=lang_en%7Clang_tr&gl=au&tbs=lr:lang_1en%7Clang_1tr&prmd=imvns&strip=1 I’m also interested in hearing your thoughts if you feel like volunteering them (and this would be my tentative/totally optional third sub-question, that being, your thoughts on fall-back error handling techniques). Just to summarize, the first two questions were, do we get option 3 included in all non-class scenarios if we choose option 2? And, is it possible that when they use the term "Class Module" they may be referring to .bas Modules as well? (Since a .bad Module is really just a class module that is pre-instantiated in the background during start-up). Thank you.

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• bulls and cows game -- programming algorithm(python)

  - by IcyFlame

  This is a simulation of the game Cows and Bulls with three digit numbers I am trying to get the number of cows and bulls between two numbers. One of which is generated by the computer and the other is guessed by the user. I have parsed the two numbers I have so that now I have two lists with three elements each and each element is one of the digits in the number. So: 237 will give the list [2,3,7]. And I make sure that the relative indices are maintained.the general pattern is:(hundreds, tens, units). And these two lists are stored in the two lists: machine and person. ALGORITHM 1 So, I wrote the following code, The most intuitive algorithm: cows and bulls are initialized to 0 before the start of this loop. for x in person: if x in machine: if machine.index(x) == person.index(x): bulls += 1 print x,' in correct place' else: print x,' in wrong place' cows += 1 And I started testing this with different type of numbers guessed by the computer. Quite randomly, I decided on 277. And I guessed 447. Here, I got the first clue that this algorithm may not work. I got 1 cow and 0 bulls. Whereas I should have got 1 bull and 1 cow. This is a table of outputs with the first algorithm: Guess Output Expected Output 447 0 bull, 1 cow 1 bull, 1 cow 477 2 bulls, 0 cows 2 bulls, 0 cows 777 0 bulls, 3 cows 2 bulls, 0 cows So obviously this algorithm was not working when there are repeated digits in the number randomly selected by the computer. I tried to understand why these errors are taking place, But I could not. I have tried a lot but I just could not see any mistake in the algorithm(probably because I wrote it!) ALGORITHM 2 On thinking about this for a few days I tried this: cows and bulls are initialized to 0 before the start of this loop. for x in range(3): for y in range(3): if x == y and machine[x] == person[y]: bulls += 1 if not (x == y) and machine[x] == person[y]: cows += 1 I was more hopeful about this one. But when I tested this, this is what I got: Guess Output Expected Output 447 1 bull, 1 cow 1 bull, 1 cow 477 2 bulls, 2 cows 2 bulls, 0 cows 777 2 bulls, 4 cows 2 bulls, 0 cows The mistake I am making is quite clear here, I understood that the numbers were being counted again and again. i.e.: 277 versus 477 When you count for bulls then the 2 bulls come up and thats alright. But when you count for cows: the 7 in 277 at units place is matched with the 7 in 477 in tens place and thus a cow is generated. the 7 in 277 at tens place is matched with the 7 in 477 in units place and thus a cow is generated.' Here the matching is exactly right as I have written the code as per that. But this is not what I want. And I have no idea whatsoever on what to do after this. Furthermore... I would like to stress that both the algorithms work perfectly, if there are no repeated digits in the number selected by the computer. Please help me with this issue. P.S.: I have been thinking about this for over a week, But I could not post a question earlier as my account was blocked(from asking questions) because I asked a foolish question. And did not delete it even though I got 2 downvotes immediately after posting the question.

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• SQL SERVER – Automated Type Conversion using Expressor Studio

  - by pinaldave

  Recently I had an interesting situation during my consultation project. Let me share to you how I solved the problem using Expressor Studio. Consider a situation in which you need to read a field, such as customer_identifier, from a text file and pass that field into a database table. In the source file’s metadata structure, customer_identifier is described as a string; however, in the target database table, customer_identifier is described as an integer. Legitimately, all the source values for customer_identifier are valid numbers, such as “109380”. To implement this in an ETL application, you probably would have hard-coded a type conversion function call, such as: output.customer_identifier=stringToInteger(input.customer_identifier) That wasn’t so bad, was it? For this instance, programming this hard-coded type conversion function call was relatively easy. However, hard-coding, whether type conversion code or other business rule code, almost always means that the application containing hard-coded fields, function calls, and values is: a) specific to an instance of use; b) is difficult to adapt to new situations; and c) doesn’t contain many reusable sub-parts. Therefore, in the long run, applications with hard-coded type conversion function calls don’t scale well. In addition, they increase the overall level of effort and degree of difficulty to write and maintain the ETL applications. To get around the trappings of hard-coding type conversion function calls, developers need an access to smarter typing systems. Expressor Studio product offers this feature exactly, by providing developers with a type conversion automation engine based on type abstraction. The theory behind the engine is quite simple. A user specifies abstract data fields in the engine, and then writes applications against the abstractions (whereas in most ETL software, developers develop applications against the physical model). When a Studio-built application is run, Studio’s engine automatically converts the source type to the abstracted data field’s type and converts the abstracted data field’s type to the target type. The engine can do this because it has a couple of built-in rules for type conversions. So, using the example above, a developer could specify customer_identifier as an abstract data field with a type of integer when using Expressor Studio. Upon reading the string value from the text file, Studio’s type conversion engine automatically converts the source field from the type specified in the source’s metadata structure to the abstract field’s type. At the time of writing the data value to the target database, the engine doesn’t have any work to do because the abstract data type and the target data type are just the same. Had they been different, the engine would have automatically provided the conversion. ?Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Database, Pinal Dave, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology Tagged: SSIS

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• How to find and fix performance problems in ORM powered applications

  - by FransBouma

  Once in a while we get requests about how to fix performance problems with our framework. As it comes down to following the same steps and looking into the same things every single time, I decided to write a blogpost about it instead, so more people can learn from this and solve performance problems in their O/R mapper powered applications. In some parts it's focused on LLBLGen Pro but it's also usable for other O/R mapping frameworks, as the vast majority of performance problems in O/R mapper powered applications are not specific for a certain O/R mapper framework. Too often, the developer looks at the wrong part of the application, trying to fix what isn't a problem in that part, and getting frustrated that 'things are so slow with <insert your favorite framework X here>'. I'm in the O/R mapper business for a long time now (almost 10 years, full time) and as it's a small world, we O/R mapper developers know almost all tricks to pull off by now: we all know what to do to make task ABC faster and what compromises (because there are almost always compromises) to deal with if we decide to make ABC faster that way. Some O/R mapper frameworks are faster in X, others in Y, but you can be sure the difference is mainly a result of a compromise some developers are willing to deal with and others aren't. That's why the O/R mapper frameworks on the market today are different in many ways, even though they all fetch and save entities from and to a database. I'm not suggesting there's no room for improvement in today's O/R mapper frameworks, there always is, but it's not a matter of 'the slowness of the application is caused by the O/R mapper' anymore. Perhaps query generation can be optimized a bit here, row materialization can be optimized a bit there, but it's mainly coming down to milliseconds. Still worth it if you're a framework developer, but it's not much compared to the time spend inside databases and in user code: if a complete fetch takes 40ms or 50ms (from call to entity object collection), it won't make a difference for your application as that 10ms difference won't be noticed. That's why it's very important to find the real locations of the problems so developers can fix them properly and don't get frustrated because their quest to get a fast, performing application failed. Performance tuning basics and rules Finding and fixing performance problems in any application is a strict procedure with four prescribed steps: isolate, analyze, interpret and fix, in that order. It's key that you don't skip a step nor make assumptions: these steps help you find the reason of a problem which seems to be there, and how to fix it or leave it as-is. Skipping a step, or when you assume things will be bad/slow without doing analysis will lead to the path of premature optimization and won't actually solve your problems, only create new ones. The most important rule of finding and fixing performance problems in software is that you have to understand what 'performance problem' actually means. Most developers will say "when a piece of software / code is slow, you have a performance problem". But is that actually the case? If I write a Linq query which will aggregate, group and sort 5 million rows from several tables to produce a resultset of 10 rows, it might take more than a couple of milliseconds before that resultset is ready to be consumed by other logic. If I solely look at the Linq query, the code consuming the resultset of the 10 rows and then look at the time it takes to complete the whole procedure, it will appear to me to be slow: all that time taken to produce and consume 10 rows? But if you look closer, if you analyze and interpret the situation, you'll see it does a tremendous amount of work, and in that light it might even be extremely fast. With every performance problem you encounter, always do realize that what you're trying to solve is perhaps not a technical problem at all, but a perception problem. The second most important rule you have to understand is based on the old saying "Penny wise, Pound Foolish": the part which takes e.g. 5% of the total time T for a given task isn't worth optimizing if you have another part which takes a much larger part of the total time T for that same given task. Optimizing parts which are relatively insignificant for the total time taken is not going to bring you better results overall, even if you totally optimize that part away. This is the core reason why analysis of the complete set of application parts which participate in a given task is key to being successful in solving performance problems: No analysis -> no problem -> no solution. One warning up front: hunting for performance will always include making compromises. Fast software can be made maintainable, but if you want to squeeze as much performance out of your software, you will inevitably be faced with the dilemma of compromising one or more from the group {readability, maintainability, features} for the extra performance you think you'll gain. It's then up to you to decide whether it's worth it. In almost all cases it's not. The reason for this is simple: the vast majority of performance problems can be solved by implementing the proper algorithms, the ones with proven Big O-characteristics so you know the performance you'll get plus you know the algorithm will work. The time taken by the algorithm implementing code is inevitable: you already implemented the best algorithm. You might find some optimizations on the technical level but in general these are minor. Let's look at the four steps to see how they guide us through the quest to find and fix performance problems. Isolate The first thing you need to do is to isolate the areas in your application which are assumed to be slow. For example, if your application is a web application and a given page is taking several seconds or even minutes to load, it's a good candidate to check out. It's important to start with the isolate step because it allows you to focus on a single code path per area with a clear begin and end and ignore the rest. The rest of the steps are taken per identified problematic area. Keep in mind that isolation focuses on tasks in an application, not code snippets. A task is something that's started in your application by either another task or the user, or another program, and has a beginning and an end. You can see a task as a piece of functionality offered by your application.  Analyze Once you've determined the problem areas, you have to perform analysis on the code paths of each area, to see where the performance problems occur and which areas are not the problem. This is a multi-layered effort: an application which uses an O/R mapper typically consists of multiple parts: there's likely some kind of interface (web, webservice, windows etc.), a part which controls the interface and business logic, the O/R mapper part and the RDBMS, all connected with either a network or inter-process connections provided by the OS or other means. Each of these parts, including the connectivity plumbing, eat up a part of the total time it takes to complete a task, e.g. load a webpage with all orders of a given customer X. To understand which parts participate in the task / area we're investigating and how much they contribute to the total time taken to complete the task, analysis of each participating task is essential. Start with the code you wrote which starts the task, analyze the code and track the path it follows through your application. What does the code do along the way, verify whether it's correct or not. Analyze whether you have implemented the right algorithms in your code for this particular area. Remember we're looking at one area at a time, which means we're ignoring all other code paths, just the code path of the current problematic area, from begin to end and back. Don't dig in and start optimizing at the code level just yet. We're just analyzing. If your analysis reveals big architectural stupidity, it's perhaps a good idea to rethink the architecture at this point. For the rest, we're analyzing which means we collect data about what could be wrong, for each participating part of the complete application. Reviewing the code you wrote is a good tool to get deeper understanding of what is going on for a given task but ultimately it lacks precision and overview what really happens: humans aren't good code interpreters, computers are. We therefore need to utilize tools to get deeper understanding about which parts contribute how much time to the total task, triggered by which other parts and for example how many times are they called. There are two different kind of tools which are necessary: .NET profilers and O/R mapper / RDBMS profilers. .NET profiling .NET profilers (e.g. dotTrace by JetBrains or Ants by Red Gate software) show exactly which pieces of code are called, how many times they're called, and the time it took to run that piece of code, at the method level and sometimes even at the line level. The .NET profilers are essential tools for understanding whether the time taken to complete a given task / area in your application is consumed by .NET code, where exactly in your code, the path to that code, how many times that code was called by other code and thus reveals where hotspots are located: the areas where a solution can be found. Importantly, they also reveal which areas can be left alone: remember our penny wise pound foolish saying: if a profiler reveals that a group of methods are fast, or don't contribute much to the total time taken for a given task, ignore them. Even if the code in them is perhaps complex and looks like a candidate for optimization: you can work all day on that, it won't matter.  As we're focusing on a single area of the application, it's best to start profiling right before you actually activate the task/area. Most .NET profilers support this by starting the application without starting the profiling procedure just yet. You navigate to the particular part which is slow, start profiling in the profiler, in your application you perform the actions which are considered slow, and afterwards you get a snapshot in the profiler. The snapshot contains the data collected by the profiler during the slow action, so most data is produced by code in the area to investigate. This is important, because it allows you to stay focused on a single area. O/R mapper and RDBMS profiling .NET profilers give you a good insight in the .NET side of things, but not in the RDBMS side of the application. As this article is about O/R mapper powered applications, we're also looking at databases, and the software making it possible to consume the database in your application: the O/R mapper. To understand which parts of the O/R mapper and database participate how much to the total time taken for task T, we need different tools. There are two kind of tools focusing on O/R mappers and database performance profiling: O/R mapper profilers and RDBMS profilers. For O/R mapper profilers, you can look at LLBLGen Prof by hibernating rhinos or the Linq to Sql/LLBLGen Pro profiler by Huagati. Hibernating rhinos also have profilers for other O/R mappers like NHibernate (NHProf) and Entity Framework (EFProf) and work the same as LLBLGen Prof. For RDBMS profilers, you have to look whether the RDBMS vendor has a profiler. For example for SQL Server, the profiler is shipped with SQL Server, for Oracle it's build into the RDBMS, however there are also 3rd party tools. Which tool you're using isn't really important, what's important is that you get insight in which queries are executed during the task / area we're currently focused on and how long they took. Here, the O/R mapper profilers have an advantage as they collect the time it took to execute the query from the application's perspective so they also collect the time it took to transport data across the network. This is important because a query which returns a massive resultset or a resultset with large blob/clob/ntext/image fields takes more time to get transported across the network than a small resultset and a database profiler doesn't take this into account most of the time. Another tool to use in this case, which is more low level and not all O/R mappers support it (though LLBLGen Pro and NHibernate as well do) is tracing: most O/R mappers offer some form of tracing or logging system which you can use to collect the SQL generated and executed and often also other activity behind the scenes. While tracing can produce a tremendous amount of data in some cases, it also gives insight in what's going on. Interpret After we've completed the analysis step it's time to look at the data we've collected. We've done code reviews to see whether we've done anything stupid and which parts actually take place and if the proper algorithms have been implemented. We've done .NET profiling to see which parts are choke points and how much time they contribute to the total time taken to complete the task we're investigating. We've performed O/R mapper profiling and RDBMS profiling to see which queries were executed during the task, how many queries were generated and executed and how long they took to complete, including network transportation. All this data reveals two things: which parts are big contributors to the total time taken and which parts are irrelevant. Both aspects are very important. The parts which are irrelevant (i.e. don't contribute significantly to the total time taken) can be ignored from now on, we won't look at them. The parts which contribute a lot to the total time taken are important to look at. We now have to first look at the .NET profiler results, to see whether the time taken is consumed in our own code, in .NET framework code, in the O/R mapper itself or somewhere else. For example if most of the time is consumed by DbCommand.ExecuteReader, the time it took to complete the task is depending on the time the data is fetched from the database. If there was just 1 query executed, according to tracing or O/R mapper profilers / RDBMS profilers, check whether that query is optimal, uses indexes or has to deal with a lot of data. Interpret means that you follow the path from begin to end through the data collected and determine where, along the path, the most time is contributed. It also means that you have to check whether this was expected or is totally unexpected. My previous example of the 10 row resultset of a query which groups millions of rows will likely reveal that a long time is spend inside the database and almost no time is spend in the .NET code, meaning the RDBMS part contributes the most to the total time taken, the rest is compared to that time, irrelevant. Considering the vastness of the source data set, it's expected this will take some time. However, does it need tweaking? Perhaps all possible tweaks are already in place. In the interpret step you then have to decide that further action in this area is necessary or not, based on what the analysis results show: if the analysis results were unexpected and in the area where the most time is contributed to the total time taken is room for improvement, action should be taken. If not, you can only accept the situation and move on. In all cases, document your decision together with the analysis you've done. If you decide that the perceived performance problem is actually expected due to the nature of the task performed, it's essential that in the future when someone else looks at the application and starts asking questions you can answer them properly and new analysis is only necessary if situations changed. Fix After interpreting the analysis results you've concluded that some areas need adjustment. This is the fix step: you're actively correcting the performance problem with proper action targeted at the real cause. In many cases related to O/R mapper powered applications it means you'll use different features of the O/R mapper to achieve the same goal, or apply optimizations at the RDBMS level. It could also mean you apply caching inside your application (compromise memory consumption over performance) to avoid unnecessary re-querying data and re-consuming the results. After applying a change, it's key you re-do the analysis and interpretation steps: compare the results and expectations with what you had before, to see whether your actions had any effect or whether it moved the problem to a different part of the application. Don't fall into the trap to do partly analysis: do the full analysis again: .NET profiling and O/R mapper / RDBMS profiling. It might very well be that the changes you've made make one part faster but another part significantly slower, in such a way that the overall problem hasn't changed at all. Performance tuning is dealing with compromises and making choices: to use one feature over the other, to accept a higher memory footprint, to go away from the strict-OO path and execute queries directly onto the RDBMS, these are choices and compromises which will cross your path if you want to fix performance problems with respect to O/R mappers or data-access and databases in general. In most cases it's not a big issue: alternatives are often good choices too and the compromises aren't that hard to deal with. What is important is that you document why you made a choice, a compromise: which analysis data, which interpretation led you to the choice made. This is key for good maintainability in the years to come. Most common performance problems with O/R mappers Below is an incomplete list of common performance problems related to data-access / O/R mappers / RDBMS code. It will help you with fixing the hotspots you found in the interpretation step. SELECT N+1: (Lazy-loading specific). Lazy loading triggered performance bottlenecks. Consider a list of Orders bound to a grid. You have a Field mapped onto a related field in Order, Customer.CompanyName. Showing this column in the grid will make the grid fetch (indirectly) for each row the Customer row. This means you'll get for the single list not 1 query (for the orders) but 1+(the number of orders shown) queries. To solve this: use eager loading using a prefetch path to fetch the customers with the orders. SELECT N+1 is easy to spot with an O/R mapper profiler or RDBMS profiler: if you see a lot of identical queries executed at once, you have this problem. Prefetch paths using many path nodes or sorting, or limiting. Eager loading problem. Prefetch paths can help with performance, but as 1 query is fetched per node, it can be the number of data fetched in a child node is bigger than you think. Also consider that data in every node is merged on the client within the parent. This is fast, but it also can take some time if you fetch massive amounts of entities. If you keep fetches small, you can use tuning parameters like the ParameterizedPrefetchPathThreshold setting to get more optimal queries. Deep inheritance hierarchies of type Target Per Entity/Type. If you use inheritance of type Target per Entity / Type (each type in the inheritance hierarchy is mapped onto its own table/view), fetches will join subtype- and supertype tables in many cases, which can lead to a lot of performance problems if the hierarchy has many types. With this problem, keep inheritance to a minimum if possible, or switch to a hierarchy of type Target Per Hierarchy, which means all entities in the inheritance hierarchy are mapped onto the same table/view. Of course this has its own set of drawbacks, but it's a compromise you might want to take. Fetching massive amounts of data by fetching large lists of entities. LLBLGen Pro supports paging (and limiting the # of rows returned), which is often key to process through large sets of data. Use paging on the RDBMS if possible (so a query is executed which returns only the rows in the page requested). When using paging in a web application, be sure that you switch server-side paging on on the datasourcecontrol used. In this case, paging on the grid alone is not enough: this can lead to fetching a lot of data which is then loaded into the grid and paged there. Keep note that analyzing queries for paging could lead to the false assumption that paging doesn't occur, e.g. when the query contains a field of type ntext/image/clob/blob and DISTINCT can't be applied while it should have (e.g. due to a join): the datareader will do DISTINCT filtering on the client. this is a little slower but it does perform paging functionality on the data-reader so it won't fetch all rows even if the query suggests it does. Fetch massive amounts of data because blob/clob/ntext/image fields aren't excluded. LLBLGen Pro supports field exclusion for queries. You can exclude fields (also in prefetch paths) per query to avoid fetching all fields of an entity, e.g. when you don't need them for the logic consuming the resultset. Excluding fields can greatly reduce the amount of time spend on data-transport across the network. Use this optimization if you see that there's a big difference between query execution time on the RDBMS and the time reported by the .NET profiler for the ExecuteReader method call. Doing client-side aggregates/scalar calculations by consuming a lot of data. If possible, try to formulate a scalar query or group by query using the projection system or GetScalar functionality of LLBLGen Pro to do data consumption on the RDBMS server. It's far more efficient to process data on the RDBMS server than to first load it all in memory, then traverse the data in-memory to calculate a value. Using .ToList() constructs inside linq queries. It might be you use .ToList() somewhere in a Linq query which makes the query be run partially in-memory. Example: var q = from c in metaData.Customers.ToList() where c.Country=="Norway" select c; This will actually fetch all customers in-memory and do an in-memory filtering, as the linq query is defined on an IEnumerable<T>, and not on the IQueryable<T>. Linq is nice, but it can often be a bit unclear where some parts of a Linq query might run. Fetching all entities to delete into memory first. To delete a set of entities it's rather inefficient to first fetch them all into memory and then delete them one by one. It's more efficient to execute a DELETE FROM ... WHERE query on the database directly to delete the entities in one go. LLBLGen Pro supports this feature, and so do some other O/R mappers. It's not always possible to do this operation in the context of an O/R mapper however: if an O/R mapper relies on a cache, these kind of operations are likely not supported because they make it impossible to track whether an entity is actually removed from the DB and thus can be removed from the cache. Fetching all entities to update with an expression into memory first. Similar to the previous point: it is more efficient to update a set of entities directly with a single UPDATE query using an expression instead of fetching the entities into memory first and then updating the entities in a loop, and afterwards saving them. It might however be a compromise you don't want to take as it is working around the idea of having an object graph in memory which is manipulated and instead makes the code fully aware there's a RDBMS somewhere. Conclusion Performance tuning is almost always about compromises and making choices. It's also about knowing where to look and how the systems in play behave and should behave. The four steps I provided should help you stay focused on the real problem and lead you towards the solution. Knowing how to optimally use the systems participating in your own code (.NET framework, O/R mapper, RDBMS, network/services) is key for success as well as knowing what's going on inside the application you built. I hope you'll find this guide useful in tracking down performance problems and dealing with them in a useful way.  

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• Gnome Shell segfault in libglib-2.0

  - by slohui

  I have been using Ubuntu 11.10 + Gnome Shell with a Nvidia card, but now I've moved it to my new PC which has an ATI card, at first it wasn't booting but I installed the driver from amd.com and then it worked. Anyway my problem is that gnome-shell is crashing, mostly when I try to start a VirtualBox machine (it happened in other times but I don't remember what I was doing). Sometimes gnome-shell respawns and it continue working but sometimes it doesn't so I have to restart lightdm and lose all the windows I was using. Here's some of the syslog when the crash occurs: Apr 9 12:20:08 desktop-1 NetworkManager[1032]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/vboxnet0, iface: vboxnet0) Apr 9 12:20:08 desktop-1 NetworkManager[1032]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/vboxnet0, iface: vboxnet0): no ifupdown configuration found. Apr 9 12:20:08 desktop-1 NetworkManager[1032]: <warn> /sys/devices/virtual/net/vboxnet0: couldn't determine device driver; ignoring... Apr 9 12:20:08 desktop-1 kernel: [ 4498.689561] warning: `VirtualBox' uses 32-bit capabilities (legacy support in use) Apr 9 12:24:29 desktop-1 gnome-session[1617]: WARNING: Application 'gnome-shell.desktop' killed by signal Apr 9 12:24:45 desktop-1 gnome-session[1617]: WARNING: App 'gnome-shell.desktop' respawning too quickly Apr 9 12:24:45 desktop-1 gnome-session[1617]: CRITICAL: We failed, but the fail whale is dead. Sorry.... Apr 9 12:25:20 desktop-1 kernel: [ 4810.769775] show_signal_msg: 30 callbacks suppressed |----- > Apr 9 12:25:20 desktop-1 kernel: [ 4810.769785] gnome-shell[3427]: segfault at b0 ip b6bd09cd sp bfc9b650 error 4 in libglib-2.0.so.0.3000.0[b6b71000+f7000]** Apr 9 12:25:20 desktop-1 gnome-session[1617]: WARNING: Application 'gnome-shell.desktop' killed by signal Apr 9 12:25:23 desktop-1 kernel: [ 4814.055705] EXT4-fs (sda1): Unaligned AIO/DIO on inode 133295 by VirtualBox; performance will be poor. Apr 9 12:26:55 desktop-1 gnome-session[1617]: Gdk-WARNING: gnome-session: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.#012 Apr 9 12:26:55 desktop-1 kernel: [ 4905.373256] [fglrx] IRQ 56 Disabled Apr 9 12:26:59 desktop-1 acpid: client 1124[0:0] has disconnected Apr 9 12:26:59 desktop-1 acpid: client connected from 3864[0:0] Apr 9 12:26:59 desktop-1 acpid: 1 client rule loaded Apr 9 12:26:59 desktop-1 kernel: [ 4909.700095] fglrx_pci 0000:02:00.0: irq 56 for MSI/MSI-X Apr 9 12:26:59 desktop-1 kernel: [ 4909.701466] [fglrx] Firegl kernel thread PID: 3867 Apr 9 12:26:59 desktop-1 kernel: [ 4909.701625] [fglrx] Firegl kernel thread PID: 3868 Apr 9 12:26:59 desktop-1 kernel: [ 4909.701852] [fglrx] Firegl kernel thread PID: 3869 Apr 9 12:26:59 desktop-1 kernel: [ 4909.702021] [fglrx] IRQ 56 Enabled Apr 9 12:26:59 desktop-1 kernel: [ 4909.861815] [fglrx] Gart USWC size:1280 M. Apr 9 12:26:59 desktop-1 kernel: [ 4909.861817] [fglrx] Gart cacheable size:508 M. Apr 9 12:26:59 desktop-1 kernel: [ 4909.861820] [fglrx] Reserved FB block: Shared offset:0, size:1000000 Apr 9 12:26:59 desktop-1 kernel: [ 4909.861821] [fglrx] Reserved FB block: Unshared offset:f8fd000, size:403000 Apr 9 12:26:59 desktop-1 kernel: [ 4909.861823] [fglrx] Reserved FB block: Unshared offset:3fff4000, size:c000 Does anyone could guide me on how to fix this? Or the proper place where to ask for help.

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• The importance of Unit Testing in BI

  - by Davide Mauri

  One of the main steps in the process we internally use to develop a BI solution is the implementation of Unit Test of you BI Data. As you may already know, I’ve create a simple (for now) tool that leverages NUnit to allow us to quickly create Unit Testing without having to resort to use Visual Studio Database Professional: http://queryunit.codeplex.com/ Once you have a tool like this one, you can start also to make sure that your BI solution (DWH and CUBE) is not only structurally sound (I mean, the cube or the report gets processed correctly), but you can also check that the logical integrity of your business rules is enforced. For example let’s say that the customer tell you that they will never create an invoice for a specific product-line in 2010 since that product-line is dismissed and will never be sold again. Ok we know that this in theory is true, but a lot of this business rule effectiveness depends on the fact the people does not do a mistake while inserting new orders/invoices and the ERP used implements a check for this business logic. Unfortunately these last two hypotesis are not always true, so you may find yourself really having some invoices for a product line that doesn’t exists anymore. Maybe this kind of situation in future will be solved using Master Data Management but, meanwhile, how you can give and idea of the data quality to your customers? How can you check that logical integrity of the analytical data you produce is exactly what you expect? Well, Unit Testing of a DWH or a CUBE can be a solution. Once you have defined your test suite, by writing SQL and MDX queries that checks that your data is what you expect to be, if you use NUnit (and QueryUnit does), you can then use a tool like NUnit2Report to create a nice HTML report that can be shipped via email to give information of data quality: In addition to that, since NUnit produces an XML file as a result, you can also import it into a SQL Server Database and then monitor the quality of data over time. I’ll be speaking about this approach (and more in general about how to “engineer” a BI solution) at the next European SQL PASS Adaptive BI Best Practices http://www.sqlpass.org/summit/eu2010/Agenda/ProgramSessions/AdaptiveBIBestPratices.aspx I’ll enjoy discussing with you all about this, so see you there! And remember: “if ain't tested it's broken!” (Sorry I don’t remember how said that in first place :-)) Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Silverlight Death Trolls Dancing on XAML&rsquo;s Grave

  - by D'Arcy Lussier

  I’m starting to see a whole bunch of tweets and blog posts on how Silverlight/WPF is dead, or how the XAML team has been disbanded at Microsoft, or how someone predicted Silverlight would die, blah blah blah. They all have a similar ring to it though: “Told ya so!” “They were stupid ideas anyway!” “Serves Microsoft right, boy are they dumb!” Let me tell you something, all those that are gleefully raving about Silverlight/WPF’s demise are nothing more than death trolls. Let’s assume that everything out there is true. Microsoft is obviously moving towards HTML 5 in a huge way (TechCrunch pointed out that SkyDrive has replaced its Silverlight based version with an HTML 5 one), and not just on the web as we’ve seen with recent announcements about how HTML 5 apps will be natively supported on Windows 8. WPF never caught on in the marketplace, regardless of its superior technology offering to Winforms. And Silverlight…well, it gave Flash a good run for its money, but plug-in based web applications are becoming passé in light of HTML 5. (It’s interesting that at a developer conference I put on just a few weeks ago, only 1 out of 60+ sessions included Silverlight. 5 focussed on HTML 5.) So what does this *death* of Silverlight/WPF/XAML mean then in the grand scheme of things (again, assuming that they truly *are* dying/dead)? Well, nothing really…at least nothing bad. Silverlight has given us some fantastic applications and experiences (Vancouver Olympics anyone?), and WP7 couldn’t have launched without Silverlight as its development platform. And WPF, although it had putrid adoption, has had some great success stories. A Canadian company that I talked to recently showed me how they re-wrote their point-of-sale application entirely in WPF, and the product is a huge success providing features their competitors aren’t. Arguably (and I say that only because I know I’m going to get WTF comments for this), VS.NET 2010 is a great example of what a WPF app can provide over previous C++ based applications. Technologies evolve. In a decade we’ve had 5 versions of the .NET framework, seen languages like J# come and go, seen F# appear, see communications layers change with WCF, seen EF go through multiple evolutions and traditional ADO.NET Datasets go extinct (from actual use anyway), and ASP.NET Webforms be replaced with ASP.NET MVC as a preferred web platform. Is Silverlight and WPF done? Maybe…probably?…thing is, it doesn’t really affect me personally in any way, or you…so why would we care if its gets replaced with something better and more robust that we can build better solutions with? Just remember the golden rule: don’t feed the trolls.

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• Does Scrum turn active developers into passive developers?

  - by Saeed Neamati

  I'm a web developer working in a team of three developers and one designer. It's now about five months that we've implemented the agile scrum software development methodology. But I have a weird feeling I just wanted to share in this site. One important factor in human life is decision-making process. However, there is a big difference in decisions you make. Some decisions are just the outcome of an internal or external force, while other decisions are completely based on your free will, and some decisions are simply something in between. The more freedom you have in making decisions, the more self-driven your work would become. This seems to be a rule. Because we tend to shape our lives ourselves. There is a big difference between you deciding what to do, or being told what to do. Before scrum, I felt like having more freedom in making the decisions which were related to development, analysis, prioritizing implementation, etc. I had more feeling like I'm deciding what I'm doing. However, due to the scrum methodology, now many decisions simply come from the product owner. He prioritizes PBIs, he analyzes how the software should work, even sometimes how the UI and functionality should be implemented. I know that this is part of the scrum methodology, and I also know that this may result in better sales of product in future. However, I now feel like I'm always getting told to do something, instead of deciding to do something. This syndrome now has made me more passive towards the work. I tend to search less to find a better solution, approach, or technique I don't wake up in the morning expecting to get to an enjoyable work. Rather, I feel like being forced to work in order to live I have more hunger to work on my own hobby projects after work I won't push the team anymore to get to the higher technological levels I spend more time now on dinner, or tea-times and have less enthusiasm to get back to work I'm now willing more for the work to finish sooner, so that I can get home The big problem is, I see and diagnose this behavior in my colleagues too. Is it the outcome of scrum? Does scrum really makes the development team feel like they have no part in forming the overall software, thus making the passive to the project? How can I overcome this feeling?

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• SQL SERVER – Various Leap Year Logics

  - by pinaldave

  Earlier I wrote one article on Leap Year and created one video about Leap Year. My point of view was to demonstrate how we can use SQL Server 2012 features to identify Leap year. How ever during the conversation I had some really good conversation. Here are updates for those who have missed reading the excellent comments on the blog. Incorrect Logic There are so many people still think Leap Year is the event which is consistently happening at every four year and the way to find it is divide the year with 4 and if the remainder is 0. That year is leap year. Well, it is not correct. Comment by David Bridge Check out this excerpt from wikipedia page http://en.wikipedia.org/wiki/Leap_year “most years that are evenly divisible by 4 are leap years…” “…Some exceptions to this rule are required since the duration of a solar year is slightly less than 365.25 days. Years that are evenly divisible by 100 are not leap years, unless they are also evenly divisible by 400, in which case they are leap years. For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Similarly, 2100, 2200, 2300, 2500, 2600, 2700, 2900 and 3000 will not be leap years, but 2400 and 2800 will be.” If you use logic of divide by 4 and remainder is 0 to find leap year, you will may end up with inaccurate result. The correct way to identify the year is to figure out the days of February and if the count is 29, the year is for sure leap year. Valid Alternate Solutions Comment by sainswor99insworth IIF((@Year%4=0 AND @Year%100 != 0) OR @Year%400=0, 1,0) Comment by Madhivanan Madhivanan has written a blog post about an year ago where he listed multiple ways to find leap year. Comment by Jayan DECLARE @year INT SET @year = 2012 IF (((@year % 4 = 0) AND (@year % 100 != 0)) OR (@year % 400 = 0)) PRINT ’1' ELSE print ’0' Comment by David DECLARE @Year INT = 2012 SELECT ISDATE('2/29/' + CAST(@Year AS CHAR(4))) Comment by David Bridge Incidentally – Another approach would be to take one day off March 1st and see if it is 29. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• What&rsquo;s new in VS.10 &amp; TFS.10?

  - by johndoucette

  Getting my geek on… I have decided to call the products VS.10 (Visual Studio 2010), TP.10 (Test Professional 2010),  and TFS.10 (Team Foundation Server 2010) Thanks Neno Loje. What's new in Visual Studio & Team Foundation Server 2010? Focusing on Visual Studio Team System (VSTS) ALM-related parts: Visual Studio Ultimate 2010 NEW: IntelliTrace® (aka the historical debugger) NEW: Architecture Tools New Project Type: Modeling Project UML Diagrams UML Use Case Diagram UML Class Diagram UML Sequence Diagram (supports reverse enginneering) UML Activity Diagram UML Component Diagram Layer Diagram (with Team Build integration for layer validation) Architecuture Explorer Dependency visualization DGML Web & Load Tests Visual Studio Premium 2010 NEW: Architecture Tools Read-only model viewer Development Tools Code Analysis New Rules like SQL Injection detection Rule Sets Code Profiler Multi-Tier Profiling JScript Profiling Profiling applications on virtual machines in sampling mode Code Metrics Test Tools Code Coverage NEW: Test Impact Analysis NEW: Coded UI Test Database Tools (DB schema versioning & deployment) Visual Studio Professional 2010 Debuger Mixed Mode Debugging for 64-bit Applications Export/Import of Breakpoints and data tips Visual Studio Test Professional 2010 Microsoft Test Manager (MTM, formerly known as "Camano")) Fast Forward Testing Visual Studio Team Foundation Server 2010 Work Item Tracking and Project Management New MSF templatesfor Agile and CMMI (V 5.0) Hierarchical Work Items Custom Work Item Link Types Ready to use Excel agile project management workbooks for managing your backlogs (including capacity planing) Convert Work Item query to an Excel report MS Excel integration Support for Work Item hierarchies Formatting is preserved after doing a 'Refresh' MS Project integration Hierarchy and successor/predecessor info is now synchronized NEW: Test Case Management Version Control Public Workspaces Branch & Merge Visualization Tracking of Changesets & Work Items Gated Check-In Team Build Build Controllers and Agents Workflow 4-based build process NEW: Lab Management (only a pre-release is avaiable at the moment!) Project Portal & Reporting Dashboards (on SharePoint Portal) Burndown Chart TFS Web Parts (to show data from TFS) Administration & Operations Topology enhancements Application tier network load balancing (NLB) SQL Server scale out Improved Sharepoint flexibility Report Server flexibility Zone support Kerberos support Separation of TFS and SQL administration Setup Separate install from configure Improved installation wizards Optional components Simplified account requirements Improved Reporting Services configuration Setup consolidation Upgrading from previous TFS versions Improved IIS flexibility Administration Consolidation of command line tools User rename support Project Collections Archive/restore individual project collections Move Team Project Collections Server consolidation Team Project Collection Split Team Project Collection Isolation Server request cancellation Licensing: TFS server license included in MSDN subscriptions Removed features (former features not part of Visual Studio 2010): Debug » Start With Application Verifier Object Test Bench IntelliSense for C++ / CLI Debugging support for SQL 2000

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• Is your test method self-validating ?

  - by mehfuzh

  Writing state of art unit tests that can validate your every part of the framework is challenging and interesting at the same time, its like becoming a samurai. One of the key concept in this is to keep our test synced all the time as underlying code changes and thus breaking them to the furthest unit as possible.  This also means, we should avoid  multiple conditions embedded in a single test. Let’s consider the following example of transfer funds. [Fact] public void ShouldAssertTranserFunds() {     var currencyService = Mock.Create<ICurrencyService>();     //// current rate     Mock.Arrange(() => currencyService.GetConversionRate("AUS", "CAD")).Returns(0.88f);       Account to = new Account { Currency = "AUS", Balance = 120 };     Account from = new Account { Currency = "CAD" };       AccountService accService = new AccountService(currencyService);       Assert.Throws<InvalidOperationException>(() => accService.TranferFunds(to, from, 200f));       accService.TranferFunds(to, from, 100f);       Assert.Equal(from.Balance, 88);     Assert.Equal(20, to.Balance); } At first look,  it seems ok but as you look more closely , it is actually doing two tasks in one test. At line# 10 it is trying to validate the exception for invalid fund transfer and finally it is asserting if the currency conversion is successfully made. Here, the name of the test itself is pretty vague. The first rule for writing unit test should always reflect to inner working of the target code, where just by looking at their names it is self explanatory. Having a obscure name for a test method not only increase the chances of cluttering the test code, but it also gives the opportunity to add multiple paths into it and eventually makes things messy as possible. I would rater have two test methods that explicitly describes its intent and are more self-validating. ShouldThrowExceptionForInvalidTransferOperation ShouldAssertTransferForExpectedConversionRate Having, this type of breakdown also helps us pin-point reported bugs easily rather wasting any time on debugging for something more general and can minimize confusion among team members. Finally, we should always make our test F.I.R.S.T ( Fast.Independent.Repeatable.Self-validating.Timely) [ Bob martin – Clean Code]. Only this will be enough to ensure, our test is as simple and clean as possible.   Hope that helps

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• Executable Resumes

  - by Liam McLennan

  Over the past twelve months I have been thinking a lot about executable specifications. Long considered the holy grail of agile software development, executable specifications means expressing a program’s functionality in a way that is both readable by the customer and computer verifiable in an automatic, repeatable way. With the current generation of BDD and ATDD tools executable specifications seem finally within the reach of a significant percentage of the development community. Lately, and partly as a result of my craftsmanship tour, I have decided that soon I am going to have to get a job (gasp!). As Dave Hoover describes in Apprenticeship Patters, “you … have mentors and kindred spirits that you meet with periodically, [but] when it comes to developing software, you work alone.” The time may have come where the only way for me to feel satisfied and enriched by my work is to seek out a work environment where I can work with people smarter and more knowledgeable than myself. Having been on both sides of the interview desk many times I know how difficult and unreliable the process can be. Therefore, I am proposing the idea of executable resumes. As a journeyman programmer looking for a fruitful work environment I plan to write an application that demonstrates my understanding of the state of the art. Potential employers can download, view and execute my executable resume and judge wether my aesthetic sensibility matches their own. The concept of the executable resume is based upon the following assertion: A line of code answers a thousand interview questions Asking people about their experiences and skills is not a direct way of assessing their value to your organisation. Often it simple assesses their ability to mislead an interviewer. An executable resume demonstrates: The highest quality code that the person is able to produce. That the person is sufficiently motivated to produce something of value in their own time. That the person loves their craft. The idea of publishing a program to demonstrate a developer’s skills comes from Rob Conery, who suggested that each developer should build their own blog engine since it is the public representation of their level of mastery. Rob said: Luke had to build his own lightsaber – geeks should have to build their own blogs. And that should be their resume. In honour of Rob’s inspiration I plan to build a blog engine as my executable resume. While it is true that the world does not need another blog engine it is as good a project as any, it is a well understood domain, and I have not found an existing blog engine that I like. Executable resumes fit well with the software craftsmanship metaphor. It is not difficult to imagine that under the guild system master craftsmen may have accepted journeymen based on the quality of the work they had produced in the past. We now understand that when it comes to the functionality of an application that code is the final arbiter. Why not apply the same rule to hiring?

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• on coding style

  - by user12607414

  I vastly prefer coding to discussing coding style, just as I would prefer to write poetry instead of talking about how it should be written. Sometimes the topic cannot be put off, either because some individual coder is messing up a shared code base and needs to be corrected, or (worse) because some officious soul has decided, "what we really need around here are some strongly enforced style rules!" Neither is the case at the moment, and yet I will venture a post on the subject. The following are not rules, but suggested etiquette. The idea is to allow a coherent style of coding to flourish safely and sanely, as a humane, inductive, social process. Maxim M1: Observe, respect, and imitate the largest-scale precedents available. (Preserve styles of whitespace, capitalization, punctuation, abbreviation, name choice, code block size, factorization, type of comments, class organization, file naming, etc., etc., etc.) Maxim M2: Don't add weight to small-scale variations. (Realize that Maxim M1 has been broken many times, but don't take that as license to create further irregularities.) Maxim M3: Listen to and rely on your reviewers to help you perceive your own coding quirks. (When you review, help the coder do this.) Maxim M4: When you touch some code, try to leave it more readable than you found it. (When you review such changes, thank the coder for the cleanup. When you plan changes, plan for cleanups.) On the Hotspot project, which is almost 1.5 decades old, we have often practiced and benefited from such etiquette. The process is, and should be, inductive, not prescriptive. An ounce of neighborliness is better than a pound of police-work. Reality check: If you actually look at (or live in) the Hotspot code base, you will find we have accumulated many annoying irregularities in our source base. I suppose this is the normal condition of a lived-in space. Unless you want to spend all your time polishing and tidying, you can't live without some smudge and clutter, can you? Final digression: Grammars and dictionaries and other prescriptive rule books are sometimes useful, but we humans learn and maintain our language by example not grammar. The same applies to style rules. Actually, I think the process of maintaining a clean and pleasant working code base is an instance of a community maintaining its common linguistic identity. BTW, I've been reading and listening to John McWhorter lately with great pleasure. (If you end with a digression, is it a tail-digression?)

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• Handling Coding Standards at Work (I'm not the boss)

  - by Josh Johnson

  I work on a small team, around 10 devs. We have no coding standards at all. There are certain things that have become the norm but some ways of doing things are completely disparate. My big one is indentation. Some use tabs, some use spaces, some use a different number of spaces, which creates a huge problem. I often end up with conflicts when I merge because someone used their IDE to auto format and they use a different character to indent than I do. I don't care which we use I just want us all to use the same one. Or else I'll open a file and some lines have curly brackets on the same line as the condition while others have them on the next line. Again, I don't mind which one so long as they are all the same. I've brought up the issue of standards to my direct manager, one on one and in group meetings, and he is not overly concerned about it (there are several others who share the same view as myself). I brought up my specific concern about indentation characters and he thought a better solution would be to, "create some kind of script that could convert all that when we push/pull from the repo." I suspect that he doesn't want to change and this solution seems overly complicated and prone to maintenance issues down the road (also, this addresses only one manifestation of a larger issue). Have any of you run into a similar situation at work? If so, how did you handle it? What would be some good points to help sell my boss on standards? Would starting a grass roots movement to create coding standards, among those of us who are interested, be a good idea? Am I being too particular, should I just let it go? Thank you all for your time. Note: Thanks everyone for the great feedback so far! To be clear, I don't want to dictate One Style To Rule Them All. I'm willing to concede my preferred way of doing something in favor of what suits everyone the best. I want consistency and I want this to be a democracy. I want it to be a group decision that everyone agrees on. True, not everyone will get their way, but I'm hoping that everyone will be mature enough to compromise for the betterment of the group. Note 2: Some people are getting caught up in the two examples I gave above. I'm more after the heart of the matter. It manifests itself with many examples: naming conventions, huge functions that should be broken up, should something go in a util or service, should something be a constant or injected, should we all use different versions of a dependency or the same, should an interface be used for this case, how should unit tests be set up, what should be unit tested, (Java specific) should we use annotations or external config. I could go on.

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• Separating physics and game logic from UI code

  - by futlib

  I'm working on a simple block-based puzzle game. The game play consists pretty much of moving blocks around in the game area, so it's a trivial physics simulation. My implementation, however, is in my opinion far from ideal and I'm wondering if you can give me any pointers on how to do it better. I've split the code up into two areas: Game logic and UI, as I did with a lot of puzzle games: The game logic is responsible for the general rules of the game (e.g. the formal rule system in chess) The UI displays the game area and pieces (e.g. chess board and pieces) and is responsible for animations (e.g. animated movement of chess pieces) The game logic represents the game state as a logical grid, where each unit is one cell's width/height on the grid. So for a grid of width 6, you can move a block of width 2 four times until it collides with the boundary. The UI takes this grid, and draws it by converting logical sizes into pixel sizes (that is, multiplies it by a constant). However, since the game has hardly any game logic, my game logic layer [1] doesn't have much to do except collision detection. Here's how it works: Player starts to drag a piece UI asks game logic for the legal movement area of that piece and lets the player drag it within that area Player lets go of a piece UI snaps the piece to the grid (so that it is at a valid logical position) UI tells game logic the new logical position (via mutator methods, which I'd rather avoid) I'm not quite happy with that: I'm writing unit tests for my game logic layer, but not the UI, and it turned out all the tricky code is in the UI: Stopping the piece from colliding with others or the boundary and snapping it to the grid. I don't like the fact that the UI tells the game logic about the new state, I would rather have it call a movePieceLeft() method or something like that, as in my other games, but I didn't get far with that approach, because the game logic knows nothing about the dragging and snapping that's possible in the UI. I think the best thing to do would be to get rid of my game logic layer and implement a physics layer instead. I've got a few questions regarding that: Is such a physics layer common, or is it more typical to have the game logic layer do this? Would the snapping to grid and piece dragging code belong to the UI or the physics layer? Would such a physics layer typically work with pixel sizes or with some kind of logical unit, like my game logic layer? I've seen event-based collision detection in a game's code base once, that is, the player would just drag the piece, the UI would render that obediently and notify the physics system, and the physics system would call a onCollision() method on the piece once a collision is detected. What is more common? This approach or asking for the legal movement area first? [1] layer is probably not the right word for what I mean, but subsystem sounds overblown and class is misguiding, because each layer can consist of several classes.

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• Silverlight Cream for December 26, 2010 -- #1015

  - by Dave Campbell

  In this all-submittal Issue: Michael Washington(-2-), Ian T. Lackey(-2-, -3-), Sandrino Di Mattia, Colin Eberhardt(-2-), and Antoni Dol. Above the Fold: Silverlight: "A Style for the Silverlight CoverFlow Control Slider" Antoni Dol WP7: "Getting the right behaviors in your Phone 7 App – Part 1 Phone Home" (and the other two parts) Ian T. Lackey Silverlight/WPF: "A Simplified Grid Markup for Silverlight and WPF" Colin Eberhardt Shoutouts: Dennis Doomen has updated his Coding Guidelines and provided a new WhitePaper, A4 cheat sheet, and VS2010 rule sets: December Update of the Coding Guidelines for C# 3.0 and C# 4.0 From SilverlightCream.com: Windows Phone 7: Saving Data when Keyboard is visible MIchael Washington takes a possible desktop approach to a data-saving issue on WP7... good solution, and one of the commenters brought up another. Windows Phone 7 View Model (MVVM) ApplicationBar Since I'm catching up, there's another post by Michael Washington... this one is looking at the WP7 ApplicationBar, and issues if you're trying to stay MVVM-proper. Michael gets around that by creating the AppBar with a behavior, and shares with all of us! Getting the right behaviors in your Phone 7 App – Part 1 Phone Home Ian T. Lackey has begun a series where he's packaging common tasks into reusable behaviors. First up is a phone dialer launching action that can be dropped on any control in your app. Getting the right behaviors in your Phone 7 App – Part 2 Binding & Browsing In his next post, Ian T. Lackey digs into the WebBrowserTask and provides a behavior allowing you to launch a browser session straight to an URL from any WP7 control. Getting the right behaviors in your Phone 7 App – Part 3 Email ‘em In his last post (all in one day), Ian T. Lackey looks at EmailComposeTask, ending up with a behavior to pre-populate EmailAddress and Subject. Cracking a Microsoft contest or why Silverlight-WCF security is important Sandrino Di Mattia was working on an app while also having a page up for a MSDN/TechNet game, and noticed some interesting WCF traffic that he was easily able to get access to. A Simplified Grid Markup for Silverlight and WPF Colin Eberhardt built us all an attached property for the Grid control that bails us out from the ugly layout we always have to put into position... oh, also for WPF! #uksnow #silverlight The Movie! – Happy Christmas Colin Eberhardt also took some time to have fun with his Twitter/BingMaps mashup for the UKSnow hashtag... you can now playback the snowfall reports, and mouse-over the snowflakes to see the original tweet... very cool stuff, Colin! A Style for the Silverlight CoverFlow Control Slider Antoni Dol got tired of the Silverlight Slider in the CoverFlow control and crafted a very nice-looking style for the Slider ... check it out and grab the source. 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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• Culture Shmulture?

  - by steve.diamond

  I've been thinking about "Customer Experience Management" lately. Here at Oracle, we arguably have the most complete suite of applications for managing the customer experience across and in the context of multiple channels -- from marketing to loyalty to contact center to self-service to analytics offerings, and more. And stay tuned, because in coming months let's just say we'll have even more to talk about on this front. But that said............ Last weekend my wife and I stayed at one of the premiere hotel chains on the planet. I won't name them, but we all know the short list. It could have been the St. Regis or the Ritz Carlton or Four Seasons or Hyatt Park or....This stay, at this particular hotel, was simply outstanding. Within a chain known for providing "above and beyond" levels of service, this particular hotel, under this particular manager, exceeded expectations on so many fronts. For example, at the Spa we mentioned to the two attendants that my wife is seven months pregnant and that we had previously had a lot of trouble conceiving. We then went to our room. Ten minutes later we heard a knock at the door and received a plate of chocolate covered strawberries with a heartfelt note and an inspiring quote, signed by the two spa attendees. The following day we arranged to have a bellhop drive us to the beach. Although they had a pre-arranged beach shuttle service with time limits, etc., he greeted us by saying, "I'm yours for the day until 4 p.m. Whatever you want to do is fine by me, as long as it's legal!" The morning that we left we arranged to have a taxi drive us to the airport--a nearly 40 mile drive. What showed up was a private coach complete with navy blue suited driver dude. And we were charged the taxi fare price. And there were many other awesome exchanges I won't mention here, although I did email the GM of this hotel two nights ago and expressed our effusive praise and gratitude. I'd submit that this hotel chain would have a definitive advantage using even more Oracle software to manage and optimize its customer interactions (yes, they are a customer). But WITHOUT the culture--that management team--and that instillation of aligned values across all employees of exemplifying 'the golden rule,' I wonder how much technology really matters in providing a distinctively positive and memorable customer experience. Lest you think I'm alone in these pontifications, have you read Paul Greenberg's blog lately? Have you seen one of his most recent posts? Now this SPECIFIC post is NOT about customer service per se. But it is about people. So yes, please think long and hard about the technology you seek to deploy. But never forget who will be interacting with your systems, and your customers.

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• What's new in the RightNow November 2012 release?

  - by Richard Lefebvre

  What new in the RightNow November 2012? In order to find out, please watch this tutorial with imbedded demonstration or read the November 2012 Release notes.   News Facts The November 2012 release of     Oracle’s RightNow CX Cloud Service marks the completion of development efforts for 2012 and continues Oracle’s commitment to enhancing the Oracle RightNow offering following the acquisition. New release delivers key capabilities designed to help organizations improve customer experiences in order to increase customer acquisition and retention, while reducing total cost of ownership. Part of the Oracle Cloud, Oracle RightNow CX Cloud Service now integrates Oracle RightNow Chat Cloud Service with Oracle Engagement Engine Cloud Service, helping organizations intelligently and proactively engage with customers through the right channel at the right time. Chat solutions have emerged as an important component of a cross-channel customer experience strategy. According to Forrester Research, Inc., chat adoption has risen dramatically between 2009 and 2011 from 19% to 37%, and it has the highest satisfaction level of all customer service channels at 62% satisfaction. (*) To help companies deliver enhanced customer experiences, Oracle has made significant investments in Oracle RightNow Chat Cloud Service throughout 2012. With the addition of rules-based engagement to existing capabilities such as co-browse, mobile chat, and cross-channel knowledge integration with the contact center, all delivered via the cloud, Oracle RightNow Chat Cloud Service is differentiated as the industry-leading chat solution. The Oracle Cloud offers a broad portfolio of software as-a-service applications, including Oracle Customer Service and Support Cloud Service, which is based on the Oracle RightNow CX Cloud Service. New Capabilities Key Oracle RightNow Chat Cloud Service and other cross-channel capabilities include: Chat Business Rules, with over 70 built-in rule conditions, leverage the Oracle Engagement Engine to help enable organizations capture rich visitor data and invoke complex actions and triggers. Chat Business Rules allow granular control over when to engage a customer via the chat channel based on customer behavior, customer profile information and operational information. Click-to-Call provides the option for a customer to engage with a live agent over the phone during the Web browsing experience. Chat Availability Controls provide organizations with the ability to throttle volume through the chat channel based on real-time agent availability and wait time thresholds. This ability to manage the channel more efficiently allows organizations to provide a better experience to customers using the chat channel. Strategic and Operational Chat Channel Analytics provide better insight into channel and agent productivity and utilization and effectiveness with both out-of-the-box reports and ad hoc reports. New chat channel analytics provide comprehensive metrics with full data transparency. Background Service Updates improve high availability metrics for Oracle RightNow Chat Cloud Service during service update periods, setting the industry leading standard for sales and service delivery to customers via the chat channel. Additional Capabilities include: Improved Web developer tools for more efficient self-service user interface design Improved administration for enhanced user sessions management Increased cross-channel community collaboration Enhanced extensibility widgets and syndication management Streamlined content management and analytics capabilities Read the full announcement here

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• Working with EO composition associations via ADF BC SDO web services

  - by Chris Muir

  ADF Business Components support the ability to publish the underlying Application Modules (AMs) and View Objects (VOs) as web services through Service Data Objects (SDOs).  This blog post looks at a minor challenge to overcome when using SDOs and Entity Objects (EOs) that use a composition association. Using the default ADF BC EO association behaviour ADF BC components allow you to work with VOs that are based on EOs that are a part of a parent-child composition association.  A composition association enforces that you cannot create records for the child outside the context of the parent.  As example when creating invoice-lines you want to enforce the individual lines have a relating parent invoice record, it just simply doesn't make sense to save invoice-lines without their parent invoice record. In the following screenshot using the ADF BC Tester it demonstrates the correct way to create a child Employees record as part of a composition association with Departments: And the following screenshot shows you the wrong way to create an Employee record: Note the error which is enforced by the composition association: (oracle.jbo.InvalidOwnerException) JBO-25030: Detail entity Employees with row key null cannot find or invalidate its owning entity.  Working with composition associations via the SDO web services  Shay Shmeltzer recently recorded a good video which demonstrates how to expose your ADF Business Components through the SDO interface. On exposing the VOs you get a choice of operation to publish including create, update, delete and more: For example through the SDO test interface we can see that the create operation will request the attributes for the VO exposed, in this case EmployeesView1: In this specific case though, just like the ADF BC Tester, an attempt to create this record will fail with JBO-25030, the composition association is still enforced: The correct way to to do this is through the create operation on the DepartmentsView1 which also lets you create employees record in context of the parent, thus satisfying the composition association rule: Yet at issue here is the create operation will always create both the parent Departments and Employees records.  What do we do if we've already previously created the parent Departments records, and we just want to create additional Employees records for that Department?  The create method of the EmployeeView1 as we saw previously doesn't allow us to do that, the JBO-3050 error will be raised. The solution is the "merge" operation on the parent Departments record: In this case for the Departments record you just need to supply the DepartmentId of the Department you want the Employees record to be associated with, as well as the new Employees record.  When invoked only the Employees record is created, and the supply of the DepartmentId of the Departments record satisfies the composition association without actually creating or updating the associated Department record that already exists in the database. Be warned however if you supply any more attributes for the Department record, it will result in a merge (update) of the associated Departments record too. 

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