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• Communication between state machines with hidden transitions

  - by slartibartfast

  The question emerged for me in embedded programming but I think it can be applied to quite a number of general networking situations e.g. when a communication partner fails. Assume we have an application logic (a program) running on a computer and a gadget connected to that computer via e.g. a serial interface like RS232. The gadget has a red/green/blue LED and a button which disables the LED. The LEDs color can be driven by software commands over the serial interface and the state (red/green/blue/off) is read back and causes a reaction in the application logic. Asynchronous behaviour of the application logic with regard to the LED color down to a certain delay (depending on the execution cycle of the application) is tolerated. What we essentially have is a resource (the LED) which can not be reserved and handled atomically by software because the (organic) user can at any time press the button to interfere/break the software attempt to switch the LED color. Stripping this example from its physical outfit I dare to say that we have two communicating state machines A (application logic) and G (gadget) where G executes state changes unbeknownst to A (and also the other way round, but this is not significant in our example) and only A can be modified at a reasonable price. A needs to see the reaction and state of G in one piece of information which may be (slightly) outdated but not inconsistent with respect to the short time window when this information was generated on the side of G. What I am looking for is a concise method to handle such a situation in embedded software (i.e. no layer/framework like CORBA etc. available). A programming technique which is able to map the complete behaviour of both participants on classical interfaces of a classical programming language (C in this case). To complicate matters (or rather, to generalize), a simple high frequency communication cycle of A to G and back (IOW: A is rapidly polling G) is out of focus because of technical restrictions (delay of serial com, A not always active, etc.). What I currently see as a general solution is: the application logic A as one thread of execution an adapter object (proxy) PG (presenting G inside the computer), together with the serial driver as another thread a communication object between the two (A and PG) which is transactionally safe to exchange The two execution contexts (threads) on the computer may be multi-core or just interrupt driven or tasks in an RTOS. The com object contains the following data: suspected state (written by A): effectively a member of the power set of states in G (in our case: red, green, blue, off, red_or_green, red_or_blue, red_or_off...etc.) command data (written by A): test_if_off, switch_to_red, switch_to_green, switch_to_blue operation status (written by PG): operation_pending, success, wrong_state, link_broken new state (written by PG): red, green, blue, off The idea of the com object is that A writes whichever (set of) state it thinks G is in, together with a command. (Example: suspected state="red_or_green", command: "switch_to_blue") Notice that the commands issued by A will not work if the user has switched off the LED and A needs to know this. PG will pick up such a com object and try to send the command to G, receive its answer (or a timeout) and set the operation status and new state accordingly. A will take back the oject once it is no longer at operation_pending and can react to the outcome. The com object could be separated of course (into two objects, one for each direction) but I think it is convenient in nearly all instances to have the command close to the result. I would like to have major flaws pointed out or hear an entirely different view on such a situation.

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• what differs a computer scientist/software engineer to regular people who learn programming language and APIs?

  - by Amumu

  In University, we learn and reinvent the wheel a lot to truly learn the programming concepts. For example, we may learn assembly language to understand, what happens inside the box, and how the system operates, when we execute our code. This helps understanding higher level concepts deeper. For example, memory management like in C is just an abstraction of manually managed memory contents and addresses. The problem is, when we're going to work, usually productivity is required more. I could program my own containers, or string class, or date/time (using POSIX with C system call) to do the job, but then, it would take much longer time to use existing STL or Boost library, which abstract all of those thing and very easy to use. This leads to an issue, that a regular person doesn't need to get through all the low level/under the hood stuffs, who learns only one programming language and using language-related APIs. These people may eventually compete with the mainstream graduates from computer science or software engineer and call themselves programmers. At first, I don't think it's valid to call them programmers. I used to think, a real programmer needs to understand the computer deeply (but not at the electronic level). But then I changed my mind. After all, they get the job done and satisfy all the test criteria (logic, performance, security...), and in business environment, who cares if you're an expert and understand how computer works or not. You may get behind the "amateurs" if you spend to much time learning about how things work inside. It is totally valid for those people to call themselves programmers. This makes me confuse. So, after all, programming should be considered an universal skill? Does programming language and concepts matter or the problems we solve matter? For example, many C/C++ vs Java and other high level language, one of the main reason is because C/C++ features performance, as well as accessing low level facility. One of the main reason (in my opinion), is coding in C/C++ seems complex, so people feel good about it (not trolling anyone, just my observation, and my experience as well. Try to google "C hacker syndrome"). While Java on the other hand, made for simplifying programming tasks to help developers concentrate on solving their problems. Based on Java rationale, if the programing language keeps evolve, one day everyone can map their logic directly with natural language. Everyone can program. On that day, maybe real programmers are mathematicians, who could perform most complex logic (including business logic and academic logic) without worrying about installing/configuring compiler, IDEs? What's our job as a computer scientist/software engineer? To solve computer specific problems or to solve problems in general? For example, take a look at this exame: http://cm.baylor.edu/ICPCWiki/attach/Problem%20Resources/2010WorldFinalProblemSet.pdf . The example requires only basic knowledge about the programming language, but focus more on problem solving with the language. In sum, what differs a computer scientist/software engineer to regular people who learn programming language and APIs? A mathematician can be considered a programmer, if he is good enough to use programming language to implement his formula. Can we programmer do this? Probably not for most of us, since we specialize about computer, not math. An electronic engineer, who learns how to use C to program for his devices, can be considered a programmer. If the programming languages keep being simplified, may one day the software engineers, who implements business logic and create softwares, be obsolete? (Not for computer scientist though, since many of the CS topics are scientific, and science won't change, but technology will).

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• NFJS Central Iowa Software Symposium Des Moines Trip Report

  - by reza_rahman

  As some of you may be aware, I recently joined the well-respected US based No Fluff Just Stuff (NFJS) Tour. If you work in the US and still don't know what the No Fluff Just Stuff (NFJS) Tour is, you are doing yourself a very serious disfavor. NFJS is by far the cheapest and most effective way to stay up to date through some world class speakers and talks. Following the US cultural tradition of old-fashioned roadshows, NFJS is basically a set program of speakers and topics offered at major US cities year round. The NFJS Central Iowa Software Symposium was held August 8 - 10 in Des Moines. The attendance at the event and my sessions was moderate by comparison to some of the other shows. It is one of the few events of it's kind that take place this part the country so it is extremely important. I had five talks total over two days, more or less back-to-back. The first one was my JavaScript + Java EE 7 talk titled "Using JavaScript/HTML5 Rich Clients with Java EE 7". This talk is basically about aligning EE 7 with the emerging JavaScript ecosystem (specifically AngularJS). The slide deck for the talk is here: JavaScript/HTML5 Rich Clients Using Java EE 7 from Reza Rahman The demo application code is posted on GitHub. The code should be a helpful resource if this development model is something that interests you. Do let me know if you need help with it but the instructions should be fairly self-explanatory. I am delivering this material at JavaOne 2014 as a two-hour tutorial. This should give me a little more bandwidth to dig a little deeper, especially on the JavaScript end. The second talk (on the second day) was our flagship Java EE 7/8 talk. Currently the talk is basically about Java EE 7 but I'm slowly evolving the talk to transform it into a Java EE 8 talk as we move forward. The following is the slide deck for the talk: JavaEE.Next(): Java EE 7, 8, and Beyond from Reza Rahman The next talk I delivered was my Cargo Tracker/Java EE + DDD talk. This talk basically overviews DDD and describes how DDD maps to Java EE using code examples/demos from the Cargo Tracker Java EE Blue Prints project. Applied Domain-Driven Design Blue Prints for Java EE from Reza Rahman The third was my talk titled "Using NoSQL with ~JPA, EclipseLink and Java EE". The talk covers an interesting gap that there is surprisingly little material on out there. The talk has three parts -- a birds-eye view of the NoSQL landscape, how to use NoSQL via a JPA centric facade using EclipseLink NoSQL, Hibernate OGM, DataNucleus, Kundera, Easy-Cassandra, etc and how to use NoSQL native APIs in Java EE via CDI. The slides for the talk are here: Using NoSQL with ~JPA, EclipseLink and Java EE from Reza Rahman The JPA based demo is available here, while the CDI based demo is available here. Both demos use MongoDB as the data store. Do let me know if you need help getting the demos up and running. I finishd off the event with a talk titled Building Java HTML5/WebSocket Applications with JSR 356. The talk introduces HTML 5 WebSocket, overviews JSR 356, tours the API and ends with a small WebSocket demo on GlassFish 4. The slide deck for the talk is posted below. Building Java HTML5/WebSocket Applications with JSR 356 from Reza Rahman The demo code is posted on GitHub: https://github.com/m-reza-rahman/hello-websocket. My next NFJS show is the Greater Atlanta Software Symposium on September 12 - 14. Here's my tour schedule so far, I'll keep you up-to-date as the tour goes forward: September 12 - 14, Atlanta. September 19 - 21, Boston. October 17 - 19, Seattle. I hope you'll take this opportunity to get some updates on Java EE as well as the other useful content on the tour?

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• Any tips on getting hired as a software project manager straight out of college?

  - by MHarrison

  I graduated with a BS in compsci last September, and I've been trying (unsuccessfully) to find a job as a project manager ever since. I fell in love with software engineering (the formal practice behind it all, not just coding) in school, and I've dedicated the last 3-4 years of my life to learning everything I can about project management and gaining experience. I've managed several projects (with teams around 12 people) while in school, and I worked with my university's software engineering research lab. My résumé is also decent - I worked as a programmer before I went to school (I'm 27 now), and I did Google Summer of Code for 3 summers. I also have general "people management" experience via working as the photo editor for my university's newspaper for 2 years. My first problem with the job hunt is not getting enough interviews. I use careers.stackoverflow.com, which is awesome because I usually get contacted by non-HR people who know what they're talking about, but there's just not enough companies using it for me to get interviews on a regular basis. I've also tried sites like monster.com, and in a fit of desperation, I sent out no less than 60 applications to project management positions. I've gotten 3 automated rejection letters and that's it. At least careers.stackoverflow gets me a phone interview with 8/10 places I apply to. But the main (and extremely frustrating) problem is the matter of experience. I've successfully managed projects from start to finish (in my software engineering classes we had real customers come in with a real software need and we built it for them), but I've never had to deal with budgets and money (I know this is why HR people immediately turn me away). Most of these positions require 5+ years PM experience, and I've seen absurd things like 12+ years required. Interviews are also maddening. I've had so many places who absolutely loved me and I made it to the final round of interviews, and I left thinking things went extremely well and they'd consider me. However, when I check in with them a week later, they tell me "We really liked you and your qualifications are excellent, but we're hoping to find someone with more experience." The bad interviews I can understand - like the PM position that would have had me managing developers both locally and overseas - I had 3 interviews with them and the ENTIRE interview process was them asking me CS brainteasers and having me waste time on things like writing quicksort on paper or writing binary search trees. Even when I tried steering the discussion towards more relevant PM stuff, they gave me some vague generic replies and went back to the "We want to be Google/MS" crap. But when I have a GOOD interview, they say my "qualifications are excellent" but they want "more experience"...that makes me want to tear my hair out. What else can I DO? While I'm aiming for technically-involved PM positions (not just crunching budget numbers), I really don't want a straight development job because I like creating software from the very high-level vs. spending a lot of time debugging memory leaks. In fact, I can't even GET development positions that I'm qualified for because I make the mistake of telling them that my future career goals are as PM (which usually results in them saying something like "Well we already have PMs and this position isn't really set up to get you there." - which I take to mean "No, that's my job, stay away.") My apologies on the long rant, but I'm seriously hellbent on getting hired as a PM since it's both my career goal and the passion that keeps me awake at night. Any suggestions on what the heck else I can do? I'm currently writing a blog where I talk about my philosophies about software engineering, and I'm writing up specs for an iOS app which I will design, code, and show employers, but this takes an awful lot of time that I don't have.

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• Library order is important

  - by Darryl Gove

  I've written quite extensively about link ordering issues, but I've not discussed the interaction between archive libraries and shared libraries. So let's take a simple program that calls a maths library function: #include <math.h int main() { for (int i=0; i<10000000; i++) { sin(i); } } We compile and run it to get the following performance: bash-3.2$ cc -g -O fp.c -lm bash-3.2$ timex ./a.out real 6.06 user 6.04 sys 0.01 Now most people will have heard of the optimised maths library which is added by the flag -xlibmopt. This contains optimised versions of key mathematical functions, in this instance, using the library doubles performance: bash-3.2$ cc -g -O -xlibmopt fp.c -lm bash-3.2$ timex ./a.out real 2.70 user 2.69 sys 0.00 The optimised maths library is provided as an archive library (libmopt.a), and the driver adds it to the link line just before the maths library - this causes the linker to pick the definitions provided by the static library in preference to those provided by libm. We can see the processing by asking the compiler to print out the link line: bash-3.2$ cc -### -g -O -xlibmopt fp.c -lm /usr/ccs/bin/ld ... fp.o -lmopt -lm -o a.out... The flag to the linker is -lmopt, and this is placed before the -lm flag. So what happens when the -lm flag is in the wrong place on the command line: bash-3.2$ cc -g -O -xlibmopt -lm fp.c bash-3.2$ timex ./a.out real 6.02 user 6.01 sys 0.01 If the -lm flag is before the source file (or object file for that matter), we get the slower performance from the system maths library. Why's that? If we look at the link line we can see the following ordering: /usr/ccs/bin/ld ... -lmopt -lm fp.o -o a.out So the optimised maths library is still placed before the system maths library, but the object file is placed afterwards. This would be ok if the optimised maths library were a shared library, but it is not - instead it's an archive library, and archive library processing is different - as described in the linker and library guide: "The link-editor searches an archive only to resolve undefined or tentative external references that have previously been encountered." An archive library can only be used resolve symbols that are outstanding at that point in the link processing. When fp.o is placed before the libmopt.a archive library, then the linker has an unresolved symbol defined in fp.o, and it will search the archive library to resolve that symbol. If the archive library is placed before fp.o then there are no unresolved symbols at that point, and so the linker doesn't need to use the archive library. This is why libmopt needs to be placed after the object files on the link line. On the other hand if the linker has observed any shared libraries, then at any point these are checked for any unresolved symbols. The consequence of this is that once the linker "sees" libm it will resolve any symbols it can to that library, and it will not check the archive library to resolve them. This is why libmopt needs to be placed before libm on the link line. This leads to the following order for placing files on the link line: Object files Archive libraries Shared libraries If you use this order, then things will consistently get resolved to the archive libraries rather than to the shared libaries.

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• Refactoring existing PHP Project. I need some advices

  - by b0x

  i have a small SAS ERP that was written some years ago using PHP. At that time, it didn't used any framework, but the code isn't a mess as i will explain more detailed in the following lines. Nowadays, the project grow and I’m now working with 3 more programmers. Often, they ask to me why we don’t migrate to a framework such Laravel. Although I'd love trying Laravel, I’m a small business and i don't have time/money to stop and spend a whole year building everything from scratch. I need to live and pay the bills. So, I've read a lot about this matter, and I decided that doing a refactoring is the best way to do it. Also, I'm not so sure that a framework will make things easy. Business goals are: Make the code easier to new hired programmers I must separate the "view", because: I want to release different versions of this product (using the same code), but under different brands and websites at the minimum cost (just changing view) Release different versions to fit mobile/tablet. Make different types of this product, seeling packages as if it were plugins. Develop custom packages for some costumers (like plugins/addon's that they can buy to put on the main application). Code goals: Introduce best pratices, standards for everyone Try to build my own MVC structure Improve validation of data/forms (today they are mixed in both ajax and classes) Create automated testing rotines, to quality assurance. My actual structure project: class\ extra\ hd\ logs\ public_html\ public_html\includes\ public_html\css|js|images\ class\ There are three types of classes. They are all “autoloaded” with something similar with PSR-0, but I don’t use namespaces. 1. class.Something.php Connects to Database using specific methods. I.e: Costumer-list(); It uses “class.Db.php”, that it’s an abstraction of mysqli on every method. 2. class.SomethingProc.php Do things that “join” things that come from “class.Something.php”. Like IF/ELSE, math operations. 3. class.SomethingHTML.php The classes with “HTML” suffix implements only static methods and HTML code only. A real life example: All the programmers need to use $cSomething ($c to class) and $arrSomething (to array). Costumer.php (view) <?php $cCosumter = new Costumer(); $arrCostumer = $cCostumer->list(); echo CostumerHTML::table($arrCostumer); ?> Extra\ Store 3rdparty projects/classes from others, such MPDF, PHPMailer, etc. Hd\ Store user’s fies outsite wwwroot dir. Logs\ Store phplogs and the system itself logs (We have a static Log::error() method, that we put in every method of every class) Public_html\ Stores the files that people use. Public_html\includes\ Store the main “config.php” file and all files that do “ajax things” ajax.Costumer.php, for example. Help is needed ;) So, as you can see we have some standards, and also for database things. But i want to write a manual of our rules. Something that i can give to any new programmer at my companie and he can go on. This is not totally a mess, but It could be better seeing the new practices. What could I do to separate this as MVC, to have multiple VIEW’s. Could you gimme some tips considering my goals? Keep im mind the different products/custom things for specific costumers without breaking the main application. URL for tutorials, books, etc. It would be nice. Thanks!

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• Advice on refactoring PHP Project

  - by b0x

  I have a small SAS ERP that was written some years ago using PHP. At that time, it didn't use any framework, but the code isn't a mess. Nowadays, the project grows and I’m now working with 3 more programmers. Often, they ask to me why we don’t migrate to a framework such as Laravel. Although I'd love trying Laravel, I’m a small business and I don't have time nor money to stop and spend a whole year building everything from scratch. I need to live and pay the bills. So, I've read a lot about this matter, and I decided that doing a refactoring is the best way to do it. Also, I'm not so sure that a framework will make things easy. Business goals are: Make the code easier to new hired programmers Separate the "view", in order to: release different versions of this product (using the same code), but under different brands and websites at the minimum cost (just changing view) release different versions to fit mobile/tablet. Make different types of this product, selling packages as if they were plugins. Develop custom packages for some costumers (like plugins/addon's that they can buy to put on the main application). Code goals: Introduce best pratices, standards for everyone Try to build my own MVC structure Improve validation of data/forms (today they are mixed in both ajax and classes) Create automated testing routines for quality assurance. My current structure project: class\ extra\ hd\ logs\ public_html\ public_html\includes\ public_html\css|js|images\ class\ There are three types of classes. They are all “autoloaded” with something similar with PSR-0, but I don’t use namespaces. 1. class.Something.php Connects to Database using specific methods. I.e: Costumer-list(); It uses “class.Db.php”, that it’s an abstraction of mysql on every method. 2. class.SomethingProc.php Do things that “join” things that come from “class.Something.php”. Like IF/ELSE, math operations. 3. class.SomethingHTML.php The classes with “HTML” suffix implements only static methods and HTML code only. A real life example: All the programmers need to use $cSomething ($c to class) and $arrSomething (to array). Costumer.php (view) <?php $cCosumter = new Costumer(); $arrCostumer = $cCostumer->list(); echo CostumerHTML::table($arrCostumer); ?> Extra\ Store 3rdparty projects/classes from others, such MPDF, PHPMailer, etc. Hd\ Store user’s files outsite wwwroot dir. Logs\ Store phplogs and the system itself logs (We have a static Log::error() method, that we put in every method of every class) Public_html\ Stores the files that people use. Public_html\includes\ Store the main “config.php” file and all files that do “ajax things” ajax.Costumer.php, for example. Help is needed ;) So, as you can see we have some standards, and also for database things. But I want to write a manual of our rules. Something that I can give to any new programmer at my company and he can go on. This is not totally a mess, but it could be better seeing the new practices. What could I do to separate this as MVC, to have multiple views. Could you give me some tips considering my goals? Keep im mind the different products/custom things for specific costumers without breaking the main application. URL for tutorials, books, etc, would be nice.

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• broken upgrade from 10.04 to 12.04 on a VPS - recoverable?

  - by HorusKol

  I have a VPS hosted 1500 km away. It originally came with 9.10 - and this morning I decided that I really should get to an LTS release, and figured I'd jump to 12.04. Researching, I discovered that there is no direct path between 9.10 and 12.04, but that I could upgrade via 10.04. After backing up my data, I dove in. The upgrade to 10.04 was successful, and I proceeded to upgrade to 12.04. Things started to go wrong. First, I got an error with GLIBC - I retried and got the same error. That's when I stopped the upgrade. I then tried another round of apt-get update && apt-get upgrade and got a list of "unmet dependencies": apt: Depends: ubuntu-keyring but it is not going to be installed Depends: libc6 (>= 2.15) but 2.11.1-0ubuntu7.11 is to be installed Depends: libstdc++6 (>= 4.6) but 4.4.3-4ubuntu5.1 is to be installed PreDepends: dpkg (>= 1.15.7.2) but 1.15.5.6ubuntu4.6 is to be installed apt-utils: Depends: libapt-pkg-libc6.10-6-4.8 libapt-inst1.4: Depends: libc6 (>= 2.14) but 2.11.1-0ubuntu7.11 is to be installed libapt-pkg4.12: Depends: libc6 (>= 2.15) but 2.11.1-0ubuntu7.11 is to be installed Depends: libstdc++6 (>= 4.6) but 4.4.3-4ubuntu5.1 is to be installed libc6: Depends: libc-bin (= 2.11.1-0ubuntu7.11) but 2.15-0ubuntu10.2 is to be installed libept0: Depends: libapt-pkg-libc6.10-6-4.8 libnih-dbus1: Depends: libnih1 (= 1.0.3-4ubuntu9) but 1.0.1-1 is to be installed I tried to see if I could do something about these - using apt-get -f install. This told me that I would need to upgrade my kernel. I found instructions on how to do this, but when I ran apt-get to install the new linux headers, I got the same dependency errors. I found another answer here where someone else had had an interruption in their upgrade - and tried the solution that worked for them: sudo apt-get -f dist-upgrade This resulted in the error: E: Could not perform immediate configuration on 'python2.7-minimal'.Please see man 5 apt.conf under APT::Immediate-Configure for details. (2) I tried to resolve this by: apt-get install -o APT::Immediate-Configure=false -f apt python-minimal But this simply ended up with this last list of dependency errors: apt: Depends: ubuntu-keyring but it is not going to be installed Depends: libc6 (>= 2.15) but 2.11.1-0ubuntu7.11 is to be installed Depends: libstdc++6 (>= 4.6) but 4.4.3-4ubuntu5.1 is to be installed PreDepends: dpkg (>= 1.15.7.2) but 1.15.5.6ubuntu4.6 is to be installed apt-utils: Depends: libapt-pkg-libc6.10-6-4.8 libapt-inst1.4: Depends: libc6 (>= 2.14) but 2.11.1-0ubuntu7.11 is to be installed libapt-pkg4.12: Depends: libc6 (>= 2.15) but 2.11.1-0ubuntu7.11 is to be installed Depends: libstdc++6 (>= 4.6) but 4.4.3-4ubuntu5.1 is to be installed libc6: Depends: libc-bin (= 2.11.1-0ubuntu7.11) but 2.15-0ubuntu10.2 is to be installed libept0: Depends: libapt-pkg-libc6.10-6-4.8 libnih-dbus1: Depends: libnih1 (= 1.0.3-4ubuntu9) but 1.0.1-1 is to be installed python: Depends: python-minimal (= 2.6.5-0ubuntu1) but 2.7.3-0ubuntu2 is to be installed python-apt: Depends: libapt-pkg-libc6.10-6-4.8 python-minimal: Depends: python2.7-minimal (>= 2.7.3) but it is not going to be installed Breaks: python-support (< 1.0.10ubuntu2) but 1.0.4ubuntu1 is to be installed synaptic: Depends: libapt-pkg-libc6.10-6-4.8 Any ideas on how to dig out of this hole?

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• Improving the efficiency of frustum culling

  - by DeadMG

  I've got some code which performs frustum culling. However, this defines the "frustum" way too broadly- when I have ~10 objects on screen, the code returns 42 objects to be rendered. I've tried taking "slices" through the frustum to attempt to increase the accuracy of the technique, but it doesn't seem to have made much impact. I also significantly reduced the far plane, so that the objects are barely at the edge. Here's my code (where size is the size in screen space- the resolution of the client area of the window I'm rendering into). Any suggestions? auto&& size = GetDimensions(); D3DVIEWPORT9 vp = { 0, 0, size.x, size.y, 0, 1 }; D3DCALL(device->SetViewport(&vp)); static const int slices = 10; std::vector<Object*> result; for(int i = 0; i < slices; i++) { D3DXVECTOR3 WorldSpaceFrustrumPoints[8] = { D3DXVECTOR3(0, size.y, static_cast<float>(i) / slices), D3DXVECTOR3(size.x, 0, static_cast<float>(i) / slices), D3DXVECTOR3(size.x, size.y, static_cast<float>(i) / slices), D3DXVECTOR3(0, 0, static_cast<float>(i) / slices), D3DXVECTOR3(0, 0, static_cast<float>(i + 1) / slices), D3DXVECTOR3(size.x, 0, static_cast<float>(i + 1) / slices), D3DXVECTOR3(size.x, size.y, static_cast<float>(i + 1) / slices), D3DXVECTOR3(0, size.y, static_cast<float>(i + 1) / slices) }; D3DXMATRIXA16 Identity; D3DXMatrixIdentity(&Identity); D3DXVec3UnprojectArray( WorldSpaceFrustrumPoints, sizeof(D3DXVECTOR3), WorldSpaceFrustrumPoints, sizeof(D3DXVECTOR3), &vp, &Projection, &View, &Identity, 8 ); Math::AABB Frustrum; auto world_begin = std::begin(WorldSpaceFrustrumPoints); auto world_end = std::end(WorldSpaceFrustrumPoints); auto world_initial = WorldSpaceFrustrumPoints[0]; Frustrum.BottomLeftClosest.x = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.x < rhs.x ? lhs : rhs; }).x; Frustrum.BottomLeftClosest.y = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.y < rhs.y ? lhs : rhs; }).y; Frustrum.BottomLeftClosest.z = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.z < rhs.z ? lhs : rhs; }).z; Frustrum.TopRightFurthest.x = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.x > rhs.x ? lhs : rhs; }).x; Frustrum.TopRightFurthest.y = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.y > rhs.y ? lhs : rhs; }).y; Frustrum.TopRightFurthest.z = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.z > rhs.z ? lhs : rhs; }).z; auto slices_result = ObjectTree.collision(Frustrum); result.insert(result.end(), slices_result.begin(), slices_result.end()); } return result;

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• How to upgrade a remote server from 8.10 to newer version?

  - by DisgruntledGoat

  I have a remote server still running Ubuntu 8.10 9.04 that I can only access via SSH. If I run apt-get update I get a bunch of 404 errors on the packages. I've asked a few questions on Server Fault but got nowhere. Here's what I've done: Run apt-get update which returns errors like: Err http://gb.archive.ubuntu.com intrepid/main Packages 404 Not Found [and same for many other packages] Run do-release-upgrade which returns: Checking for a new ubuntu release Failed Upgrade tool signature Failed Upgrade tool Done downloading extracting 'jaunty.tar.gz' Failed to extract Extracting the upgrade failed. There may be a problem with the network or with the server. Edited /etc/update-manager/release-upgrades and changed from Prompt=normal to Prompt=lts (as suggested here). Running do-release-upgrade after this returns: Checking for a new ubuntu release current dist not found in meta-release file No new release found (Updated) I have followed the advice in this question and changed /etc/apt/sources.list to refer to jaunty instead of intrepid. However, that distro is not online anymore either. A comment there says I have to upgrade in chronological order... So basically, it seems like I cannot upgrade because my current distro is out of date and not supported. Is there a way to upgrade direct to 10.x or 11.x? Note, as this is a server I only have command-line access. UPDATE 24/11: I have managed to upgrade from 8.10 to 9.04. Ubuntu's EOL Upgrades page provides some alternate URLs for apt sources. I also needed to update /var/lib/update-manager/meta-release to point to the old-releases server too. However, now I cannot upgrade from 9.04 to 9.10. Running do-release-upgrade produces the same error as #2 above, except it "Failed to fetch" (the URLs in meta-release are valid). The Ubuntu Jaunty upgrade page says it's necessary to upgrade using a CD image. I followed the instructions here, but it didn't work: A fatal error occurred Please report this as a bug and include the files /var/log/dist-upgrade/main.log and /var/log/dist-upgrade/apt.log in your report. The upgrade is now aborted. Your original sources.list was saved in /etc/apt/sources.list.distUpgrade. Traceback (most recent call last): File "/tmp/tmp.JLhTwVUugb/karmic", line 7, in sys.exit(main()) File "/tmp/tmp.JLhTwVUugb/DistUpgradeMain.py", line 132, in main if app.run(): File "/tmp/tmp.JLhTwVUugb/DistUpgradeController.py", line 1590, in run return self.fullUpgrade() File "/tmp/tmp.JLhTwVUugb/DistUpgradeController.py", line 1506, in fullUpgrade if not self.doPostInitialUpdate(): File "/tmp/tmp.JLhTwVUugb/DistUpgradeController.py", line 762, in doPostInitialUpdate self.quirks.run("PostInitialUpdate") File "/tmp/tmp.JLhTwVUugb/DistUpgradeQuirks.py", line 83, in run for plugin in self.plugin_manager.get_plugins(condition): File "/tmp/tmp.JLhTwVUugb/computerjanitor/plugin.py", line 167, in get_plugins filenames = self.get_plugin_files() File "/tmp/tmp.JLhTwVUugb/computerjanitor/plugin.py", line 120, in get_plugin_files basenames = [x for x in os.listdir(dirname) OSError: [Errno 2] No such file or directory: './plugins' It does say to report the bug, but since this is an old unsupported release I don't know if it's worth doing. However, is there a way round this, to upgrade from 9.04 to 9.10 (And then finally to 10.04 LTS.)

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• Using HTML5 Today part 3&ndash; Using Polyfills

  - by Steve Albers

  Shims helps when adding semantic tags to older IE browsers, but there is a huge range of other new HTML5 features that having varying support on browsers.  Polyfills are JavaScript code and/or browser plug-ins that can provide older or less featured browsers with API support.  The best polyfills will detect the whether the current browser has native support, and only adds the functionality if necessary.  The Douglas Crockford JSON2.js library is an example of this approach: if the browser already supports the JSON object, nothing changes.  If JSON is not available, the library adds a JSON property in the global object. This approach provides some big benefits: It lets you add great new HTML5 features to your web sites sooner. It lets the developer focus on writing to the up-and-coming standard rather than proprietary APIs. Where most one-off legacy code fixes tends to break down over time, well done polyfills will stop executing over time (as customer browsers natively support the feature) meaning polyfill code may not need to be tested against new browsers since they will execute the native methods instead. Your should also remember that Polyfills represent an entirely separate code path (and sometimes plug-in) that requires testing for support.  Also Polyfills tend to run on older browsers, which often have slower JavaScript performance.  As a result you might find that performance on older browsers is not comparable. When looking for Polyfills you can start by checking the Modernizr GitHub wiki or the HTML5 Please site. For an example of a polyfill consider a page that writes a few geometric shapes on a <canvas> <script src="jquery-1.7.1.min.js"><script> <script> $(document).ready(function () { drawCanvas(); }); function drawCanvas() { var context = $("canvas")[0].getContext('2d'); //background context.fillStyle = "#8B0000"; context.fillRect(5, 5, 300, 100); // emptybox context.strokeStyle = "#B0C4DE"; context.lineWidth = 4; context.strokeRect(20, 15, 80, 80); // circle context.arc(160, 55, 40, 0, Math.PI * 2, false); context.fillStyle = "#4B0082"; context.fill(); </script>   The result is a simple static canvas with a box & a circle:   …to enable this functionality on a pre-canvas browser we can find a polyfill.  A check on html5please.com references  FlashCanvas.  Pull down the zip and extract the files (flashcanvas.js, flash10canvas.swf, etc) to a directory on your site.  Then based on the documentation you need to add a single line to your original HTML file: <!--[if lt IE 9]><script src="flashcanvas.js"></script><![endif]—> …and you have canvas functionality!  The IE conditional comments ensure that the library is only loaded in browsers where it is useful, improving page load & processing time. Like all Polyfills, you should test to verify the functionality matches your expectations across browsers you need to support.  For instance the Flash Canvas home page advertises 70% support of HTML5 Canvas spec tests.

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• What Counts For a DBA – Depth

  - by Louis Davidson

  SQL Server offers very simple interfaces to many of its features. Most people could open up SSMS, connect to a server, write a simple query and see the results. Even several of the core DBA tasks are deceptively straightforward. It doesn’t take a rocket scientist to perform a basic database backup or run a trace (even using the newfangled Extended Events!). However, appearances can be deceptive, and often times it is really important that a DBA understands not just the basics of how to perform a task, but why we do a task, and how that task works. As an analogy, consider a child walking into a darkened room. Most would know that they need to turn on the light, and how to do it, so they flick the switch. But what happens if light fails to shine forth. Most would immediately tell you that you need to consider changing the light bulb. So you hop in the car and take them to the local home store and instruct them to buy a replacement. Confronted with a 40 foot display of light bulbs, how will they decide which of the hundreds of types of bulbs, of different types, fittings, shapes, colors, power and efficiency ratings, is the right choice? Obviously the main lesson the child is going to learn this day is how to use their cell phone as a flashlight so they don’t have to ask for help the next time. Likewise, when the metaphorical toddlers who use your database server have issues, they will instinctively know something is wrong, and may even have some idea what caused it, but will have no depth of knowledge to figure out the right solution. That is where the DBA comes in and attempts to save the day. However, when one looks beneath the shiny UI, SQL Server has its own “40 foot display of light bulbs”, in the form of the tremendous number of tools and the often-bewildering amount of information they can present to the DBA, to help us find issues. Unfortunately, resorting to guesswork, to trying different “bulbs” over and over, hoping to stumble on the answer. This is where the right depth of knowledge goes a long way. If we need to write a SELECT statement, then knowing the syntax and where to find the data is not enough. Knowledge of indexes and query plans is essential. Without it, we might hit on a query that “works”, but we are basically still a user, not a programmer, because we have no real control over our platform. Is that level of knowledge deep enough? Probably not, since knowledge of the underlying metadata and structures would be very useful in helping us make sense of any query plan. Understanding the structure of an index makes the “key lookup” operator not sound like what you do when someone tapes your car key to the ceiling. So is even this level of understanding deep enough? Do we need to understand the memory architecture used to process the query? It might be a comforting level of knowledge, and will doubtless come in handy at some point, but is not strictly necessary in most cases. Beyond that lies (more or less) full knowledge of SQL language and the intricacies of every step the SQL Server engine takes to process our query. My personal theory is that, as a professional, our knowledge of a given task should extend, at a minimum, one level deeper than is strictly necessary to perform the task. Anything deeper can be left to the ridiculously smart, or obsessive, or both. As an example. tasked with storing an integer value between 0 and 99999999, it’s essential that I know that choosing an Integer over Decimal(8,0) will likely offer performance benefits. It is then useful that I also understand the value of adding a CHECK constraint, to make sure the values are valid to the desired range; and comforting that I know a little about the underlying processors, registers and computer math. Anything further, I leave to the likes of Joe Chang, whose recent blog post on the topic offers depth by the bucketful!  

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• Resolving collisions between dynamic game objects

  - by TheBroodian

  I've been building a 2D platformer for some time now, I'm getting to the point where I am adding dynamic objects to the stage for testing. This has prompted me to consider how I would like my character and other objects to behave when they collide. A typical staple in many 2D platformer type games is that the player takes damage upon touching an enemy, and then essentially becomes able to pass through enemies during a period of invulnerability, and at the same time, enemies are able to pass through eachother freely. I personally don't want to take this approach, it feels strange to me that the player should receive arbitrary damage for harmless contact to an enemy, despite whether the enemy is attacking or not, and I would like my enemies' interactions between each other (and my player) to be a little more organic, so to speak. In my head I sort of have this idea where a game object (player, or non player) would be able to push other game objects around by manner of 'pushing' each other out of one anothers' bounding boxes if there is an intersection, and maybe correlate the repelling force to how much their bounding boxes are intersecting. The problem I'm experiencing is I have no idea what the math might look like for something like this? I'll show what work I've done so far, it sort of works, but it's jittery, and generally not quite what I would pass in a functional game: //Clears the anti-duplicate buffer collisionRecord.Clear(); //pick a thing foreach (GameObject entity in entities) { //pick another thing foreach (GameObject subject in entities) { //check to make sure both things aren't the same thing if (!ReferenceEquals(entity, subject)) { //check to see if thing2 is in semi-near proximity to thing1 if (entity.WideProximityArea.Intersects(subject.CollisionRectangle) || entity.WideProximityArea.Contains(subject.CollisionRectangle)) { //check to see if thing2 and thing1 are colliding. if (entity.CollisionRectangle.Intersects(subject.CollisionRectangle) || entity.CollisionRectangle.Contains(subject.CollisionRectangle) || subject.CollisionRectangle.Contains(entity.CollisionRectangle)) { //check if we've already resolved their collision or not. if (!collisionRecord.ContainsKey(entity.GetHashCode())) { //more duplicate resolution checking. if (!collisionRecord.ContainsKey(subject.GetHashCode())) { //if thing1 is traveling right... if (entity.Velocity.X > 0) { //if it isn't too far to the right... if (subject.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height)) || subject.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = entity.CollisionRectangle.Right - subject.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the left, and thing2 to the right. entity.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //if thing1 is traveling left... if (entity.Velocity.X < 0) { //if thing1 isn't too far left... if (entity.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height)) || entity.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = subject.CollisionRectangle.Right - entity.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the right, and thing2 to the left. entity.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //Make record that thing1 and thing2 have interacted and the collision has been solved, so that if thing2 is picked next in the foreach loop, it isn't checked against thing1 a second time before the next update. collisionRecord.Add(entity.GetHashCode(), subject.GetHashCode()); } } } } } } } } One of the biggest issues with my code aside from the jitteriness is that if one character were to land on top of another character, it very suddenly and abruptly resolves the collision, whereas I would like a more subtle and gradual resolution. Any thoughts or ideas are incredibly welcome and helpful.

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• Problem with sprite direction and rotation

  - by user2236165

  I have a sprite called Tool that moves with a speed represented as a float and in a direction represented as a Vector2. When I click the mouse on the screen the sprite change its direction and starts to move towards the mouseclick. In addition to that I rotate the sprite so that it is facing in the direction it is heading. However, when I add a camera that is suppose to follow the sprite so that the sprite is always centered on the screen, the sprite won't move in the given direction and the rotation isn't accurate anymore. This only happens when I add the Camera.View in the spriteBatch.Begin(). I was hoping anyone could maybe shed a light on what I am missing in my code, that would be highly appreciated. Here is the camera class i use: public class Camera { private const float zoomUpperLimit = 1.5f; private const float zoomLowerLimit = 0.1f; private float _zoom; private Vector2 _pos; private int ViewportWidth, ViewportHeight; #region Properties public float Zoom { get { return _zoom; } set { _zoom = value; if (_zoom < zoomLowerLimit) _zoom = zoomLowerLimit; if (_zoom > zoomUpperLimit) _zoom = zoomUpperLimit; } } public Rectangle Viewport { get { int width = (int)((ViewportWidth / _zoom)); int height = (int)((ViewportHeight / _zoom)); return new Rectangle((int)(_pos.X - width / 2), (int)(_pos.Y - height / 2), width, height); } } public void Move(Vector2 amount) { _pos += amount; } public Vector2 Position { get { return _pos; } set { _pos = value; } } public Matrix View { get { return Matrix.CreateTranslation(new Vector3(-_pos.X, -_pos.Y, 0)) * Matrix.CreateScale(new Vector3(Zoom, Zoom, 1)) * Matrix.CreateTranslation(new Vector3(ViewportWidth * 0.5f, ViewportHeight * 0.5f, 0)); } } #endregion public Camera(Viewport viewport, float initialZoom) { _zoom = initialZoom; _pos = Vector2.Zero; ViewportWidth = viewport.Width; ViewportHeight = viewport.Height; } } And here is my Update and Draw-method: protected override void Update (GameTime gameTime) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; TouchCollection touchCollection = TouchPanel.GetState (); foreach (TouchLocation tl in touchCollection) { if (tl.State == TouchLocationState.Pressed || tl.State == TouchLocationState.Moved) { //direction the tool shall move towards direction = touchCollection [0].Position - toolPos; if (direction != Vector2.Zero) { direction.Normalize (); } //change the direction the tool is moving and find the rotationangle the texture must rotate to point in given direction toolPos += (direction * speed * elapsed); RotationAngle = (float)Math.Atan2 (direction.Y, direction.X); } } if (direction != Vector2.Zero) { direction.Normalize (); } //move tool in given direction toolPos += (direction * speed * elapsed); //change cameracentre to the tools position Camera.Position = toolPos; base.Update (gameTime); } protected override void Draw (GameTime gameTime) { graphics.GraphicsDevice.Clear (Color.Blue); spriteBatch.Begin (SpriteSortMode.BackToFront, BlendState.AlphaBlend, null, null, null, null, Camera.View); spriteBatch.Draw (tool, new Vector2 (toolPos.X, toolPos.Y), null, Color.White, RotationAngle, originOfToolTexture, 1, SpriteEffects.None, 1); spriteBatch.End (); base.Draw (gameTime); }

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• Software and/(x)or Hardware Projects for Pre-School Kids

  - by haylem

  I offered to participate at my kid's pre-school for various activities (yes, I'm crazy like that), and one of them is to help them discover extra-curricular (big word for a pre-school, but by lack of a better one... :)) hobbies, which may or may not relate to a professional activity. At first I thought that it wouldn't be really easy to have pre-schoolers relate to programming or the internal workings of a computer system in general (and I'm more used to teaching middle-school to university-level students), but then I thought there must be a way. So I'm trying to figure out ways to introduce very young kids (3yo) to computer systems in a fun and preferably educational way. Of course, I don't expect them to start smashing the stack for fun and profit right away (or at least not voluntarily, though I could use the occasion for some toddler tests...), but I'm confident there must be ways to get them interested in both: using the systems, becoming curious about understanding what they do, interacting with the systems to modify them. I guess this setting is not really relevant after all, it's pretty much the same as if you were aiming to achieve the same for your own kids at home. Ideas Considering we're talking 3yo pre-schoolers here, and that at this age some kids are already quite confident using a mouse (some even a keyboard, if not for typing, at least to press some buttons they've come to associate with actions) while others have not yet had any interaction with computers of any kind, it needs to be: rather basic, demonstrated and played with in less then 5 or 10 minutes, doable in in groups or alone, scalable and extendable in complexity to accommodate their varying abilities. The obvious options are: basic smallish games to play with, interactive systems like LOGO, Kojo, Squeak and clones (possibly even simpler than that), or thngs like Lego Systems. I guess it can be a thing to reflect on both at the software and the hardware levels: it could be done with a desktop or laptop machine, a tablet, a smartphone (or a crap-phone, for that matter, as long as you can modify it), or even get down to building something from scratch (Raspberry Pi and Arduino being popular options at the moment). I can probably be in the form of games, funny visualizations (which are pretty much games) w/ Prototype, virtual worlds to explore. I also thought on the moment (and I hope this won't offend anyone) that some approaches to teaching pets could work (reward systems, haptic feedback and such things could quickly point a kid in the right direction to understanding how things work, in a similar fashion - I'm not suggesting to shock the kids!). Hmm, Is There an Actual Question in There? What type of systems do you think might be a good fit, both in terms of hardware and software? Do you have seen such systems, or have anything in mind to work on? Are you aware of some research in this domain, with tangible results? Any input is welcome. It's not that I don't see options: there are tons, but I have a harder time pinpointing a more concrete and definite type of project/activity, so I figure some have valuable ideas or existing ones. Note: I am not advocating that every kid should learn to program, be interested in computer systems, or that all of them in a class would even care enough to follow such an introduction with more than a blank stare. I don't buy into the "everybody would benefit from learning to program" thing. Wouldn't hurt, but not necessary in any way. But if I can walk out of there with a few of them having smiled using the thing (or heck, cried because others took them away from them), that'd be good enough. Related Questions I've seen and that seem to complement what I'm looking for, but not exactly for the same age groups or with the same goals: Teaching Programming to Kids Recommendations for teaching kids math concepts & skills for programming?

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• Slide 2d Vector to destination over a period of time

  - by SchautDollar

  I am making a library of GUI controls for games I make with XNA. I am currently developing the library as I make a game so I can test the features and find errors/bugs and hopefully smash them right away. My current issue is on a slide feature I want to implement for my base class that all controls inherit. My goal is to get the control to slide to a specified point over a specified amount of time. Here is the #region containing the code #region Slide private bool sliding; private Vector2 endPoint; private float slideTimeLeft; private float speed; private bool wasEnabled; private Vector2 slideDirection; private float slideDistance; public void Slide(Vector2 startPoint, Vector2 endPoint, float slideTime) { this.location = startPoint; Slide(endPoint,slideTime); } public void Slide(Vector2 endPoint, float slideTime) { this.wasEnabled = this.enabled; this.enabled = false; this.sliding = true; Vector2 tempLength = endPoint - this.location; this.slideDistance = tempLength.Length(); //Was this.slideDistance = (float)Math.Sqrt(tempLength.LengthSquared()); this.speed = slideTime / this.slideDistance; this.endPoint = endPoint; this.slideTimeLeft = slideTime; } private void UpdateSlide(GameTime gameTime) { if (this.sliding) { this.slideTimeLeft -= gameTime.ElapsedGameTime.Milliseconds; if (this.slideTimeLeft >= 0 ) { if ((this.endPoint-this.location).Length() != 0){//Was if (this.endPoint.LengthSquared() > 0 || this.location.LengthSquared() > 0) { this.slideDirection = Vector2.Normalize(this.endPoint - this.location); } this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;//This is where I believe the issue is, but I'm not sure. It seems right to me... (Even though it doesn't work) } else { this.enabled = this.wasEnabled; this.location = this.endPoint;//After time, the controls position will get set to be the endpoint. this.sliding = false; } } } #endregion this.location is the location of the control elsewhere defined in the class. I have looked at this blog as a huge reference and have googled around quite and have looked on many forums but can't find anything that shows how to implement it. Please and Thanks for your time! EDIT: I have switched this line "this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;" several times to see what it does. My issue is getting the control to smoothly move to the end location. It moves after the time has expired, but It doesn't move other then that except flash in my face. EDIT2: I have used the first slide method with 3 parameters and it works except it doesn't do it in a period of time and once it gets to its destination, it starts moving randomly towards the previous location and the end location.

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• Why is 0 false?

  - by Morwenn

  This question may sound dumb, but why does 0 evaluates to false and any other [integer] value to true is most of programming languages? String comparison Since the question seems a little bit too simple, I will explain myself a little bit more: first of all, it may seem evident to any programmer, but why wouldn't there be a programming language - there may actually be, but not any I used - where 0 evaluates to true and all the other [integer] values to false? That one remark may seem random, but I have a few examples where it may have been a good idea. First of all, let's take the example of strings three-way comparison, I will take C's strcmp as example: any programmer trying C as his first language may be tempted to write the following code: if (strcmp(str1, str2)) { // Do something... } Since strcmp returns 0 which evaluates to false when the strings are equal, what the beginning programmer tried to do fails miserably and he generally does not understand why at first. Had 0 evaluated to true instead, this function could have been used in its most simple expression - the one above - when comparing for equality, and the proper checks for -1 and 1 would have been done only when needed. We would have considered the return type as bool (in our minds I mean) most of the time. Moreover, let's introduce a new type, sign, that just takes values -1, 0 and 1. That can be pretty handy. Imagine there is a spaceship operator in C++ and we want it for std::string (well, there already is the compare function, but spaceship operator is more fun). The declaration would currently be the following one: sign operator<=>(const std::string& lhs, const std::string& rhs); Had 0 been evaluated to true, the spaceship operator wouldn't even exist, and we could have declared operator== that way: sign operator==(const std::string& lhs, const std::string& rhs); This operator== would have handled three-way comparison at once, and could still be used to perform the following check while still being able to check which string is lexicographically superior to the other when needed: if (str1 == str2) { // Do something... } Old errors handling We now have exceptions, so this part only applies to the old languages where no such thing exist (C for example). If we look at C's standard library (and POSIX one too), we can see for sure that maaaaany functions return 0 when successful and any integer otherwise. I have sadly seen some people do this kind of things: #define TRUE 0 // ... if (some_function() == TRUE) { // Here, TRUE would mean success... // Do something } If we think about how we think in programming, we often have the following reasoning pattern: Do something Did it work? Yes -> That's ok, one case to handle No -> Why? Many cases to handle If we think about it again, it would have made sense to put the only neutral value, 0, to yes (and that's how C's functions work), while all the other values can be there to solve the many cases of the no. However, in all the programming languages I know (except maybe some experimental esotheric languages), that yes evaluates to false in an if condition, while all the no cases evaluate to true. There are many situations when "it works" represents one case while "it does not work" represents many probable causes. If we think about it that way, having 0 evaluate to true and the rest to false would have made much more sense. Conclusion My conclusion is essentially my original question: why did we design languages where 0 is false and the other values are true, taking in account my few examples above and maybe some more I did not think of? Follow-up: It's nice to see there are many answers with many ideas and as many possible reasons for it to be like that. I love how passionate you seem to be about it. I originaly asked this question out of boredom, but since you seem so passionate, I decided to go a little further and ask about the rationale behind the Boolean choice for 0 and 1 on Math.SE :)

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• Byte array serialization in JSON.NET

  - by Daniel Earwicker

  Given this simple class: class HasBytes { public byte[] Bytes { get; set; } } I can round-trip it through JSON using JSON.NET such that the byte array is base-64 encoded: var bytes = new HasBytes { Bytes = new byte[] { 1, 2, 3, 4 } }; // turn it into a JSON string var json = JsonConvert.SerializeObject(bytes); // get back a new instance of HasBytes var result1 = JsonConvert.DeserializeObject<HasBytes>(json); // all is well Debug.Assert(bytes.Bytes.SequenceEqual(result1.Bytes)); But if I deserialize this-a-wise: var result2 = (HasBytes)new JsonSerializer().Deserialize( new JTokenReader( JToken.ReadFrom(new JsonTextReader( new StringReader(json)))), typeof(HasBytes)); ... it throws an exception, "Expected bytes but got string". What other options/flags/whatever would need to be added to the "complicated" version to make it properly decode the base-64 string to initialize the byte array? Obviously I'd prefer to use the simple version but I'm trying to work with a CouchDB wrapper library called Divan, which sadly uses the complicated version, with the responsibilities for tokenizing/deserializing widely separated, and I want to make the simplest possible patch to how it currently works.

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• getting a job in game industry as a developer, just knowing a game engine

  - by numerical25

  I recently enrolled at a community college for game developement. But I am skeptical about the circulum. I have no experience in the gaming industry so I wouldnt be able to tell rather its a good investment or not. So I am asking you. I dont want to get too much into detail of all the classes I am taking so I will try to be brief. By the time I graduate, I should have a understanding of how a game engine works. I will be working with the unreal engine to develop a Multiplayer game from scratch. So in the process of my final project, I will learn how to work within the unreal engine, Learn python and learn how to use it's API to connect to a remote server and build game mechanics. Overall I will also recieve a associates degree in game development. I learn c++ but not c. The director said he was trying to implement c in the program as well. What I notice is I will not learn how to build a 3d game engine from scratch. They do not teach any AI. I will not learn how to work with the graphics card using a graphic's api such as DirectX or OpenGL. I know building a game engine from scratch is a little complex, but at the same time the track is requireing me to take some advances math courses such a calculus and geotomtry 1 and 2. I also got to take a physic class. I just think thats a little much for just learning how to use the unreal engine but not actually build one or try to learn the anatomy of a game engine. Is this good enough to possibly land my a job in the insdustry. If I left anything out or was not detail, please feel free to ask more questions. Thanks Guys!!

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• Pass dataset to subreport with SQL Server Reporting Services

  - by Juliet

  I'm using SQL Server Reporting Services and the report designer that comes with Visual Studio. I've got a really big report. It's actually so large that Visual Studio hangs (sometimes for hours at a time) or just crashes when I make changes. There is preciously little I can do to solve the problem, so I've decided to just move the bottom half of the report into a sub-report. So, I started with one enormous, unresponsive report and ended with two small, manageable reports -- surprisingly, this actually works. One problem: my subreport uses the same data as my main report. Right now, it populates its dataset by re-querying the database. The extra round-trip to the database causes the report to take twice as long to generate; up from 45 minutes to 1 1/2 hours to generate. I'd like to avoid hitting the database again, and instead use the same dataset in both reports. How can I share or pass a dataset between a report and subreport?

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• Windows Azure : Storage Client Exception Unhandled

  - by veda

  I am writing a code for upload large files into the blobs using blocks... When I tested it, it gave me an StorageClientException It stated: One of the request inputs is out of range. I got this exception in this line of the code: blob.PutBlock(block, ms, null); Here is my code: protected void ButUploadBlocks_click(object sender, EventArgs e) { // store upladed file as a blob storage if (uplFileUpload.HasFile) { name = uplFileUpload.FileName; byte[] byteArray = uplFileUpload.FileBytes; Int64 contentLength = byteArray.Length; int numBytesPerBlock = 250 *1024; // 250KB per block int blocksCount = (int)Math.Ceiling((double)contentLength / numBytesPerBlock); // number of blocks MemoryStream ms ; List<string>BlockIds = new List<string>(); string block; int offset = 0; // get refernce to the cloud blob container CloudBlobContainer blobContainer = cloudBlobClient.GetContainerReference("documents"); // set the name for the uploading files string UploadDocName = name; // get the blob reference and set the metadata properties CloudBlockBlob blob = blobContainer.GetBlockBlobReference(UploadDocName); blob.Properties.ContentType = uplFileUpload.PostedFile.ContentType; for (int i = 0; i < blocksCount; i++, offset = offset + numBytesPerBlock) { block = Convert.ToBase64String(BitConverter.GetBytes(i)); ms = new MemoryStream(); ms.Write(byteArray, offset, numBytesPerBlock); blob.PutBlock(block, ms, null); BlockIds.Add(block); } blob.PutBlockList(BlockIds); blob.Metadata["FILETYPE"] = "text"; } } Can anyone tell me how to solve it...

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• Silverlight 4 WriteableBitmap ScaleTransform Exception but was working in v3

  - by Imran

  I am getting the following exception for code that used to work in silverlight 3 but has stopped working since upgrading to silverlight 4: System.AccessViolationException was unhandled Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt. namespace SilverlightApplication1 { public partial class MainPage : UserControl { public MainPage() { InitializeComponent(); } private void button1_Click(object sender, RoutedEventArgs e) { var OpenFileDialog = new OpenFileDialog(); OpenFileDialog.Filter = "*.jpg|*.jpg"; if (OpenFileDialog.ShowDialog() == true) { var file = OpenFileDialog.Files.ToArray()[0]; ScaleStreamAsBitmap(file.OpenRead(), 200); } } public static WriteableBitmap ScaleStreamAsBitmap(Stream file, int maxEdgeLength) { file.Position = 0; var src = new BitmapImage(); var uiElement = new System.Windows.Controls.Image(); WriteableBitmap b = null; var t = new ScaleTransform(); src.SetSource(file); uiElement.Source = src; //force render uiElement.Effect = new DropShadowEffect() { ShadowDepth = 0, BlurRadius = 0 }; ; //calc scale double scaleX = 1; double scaleY = 1; if (src.PixelWidth > maxEdgeLength) scaleX = ((double)maxEdgeLength) / src.PixelWidth; if (src.PixelHeight > maxEdgeLength) scaleY = ((double)maxEdgeLength) / src.PixelHeight; double scale = Math.Min(scaleX, scaleY); t.ScaleX = scale; t.ScaleY = scale; b = new WriteableBitmap(uiElement, t); return b; } } } Thanks

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• How to implement progress bar and backgroundworker for database calls C#?

  - by go-goo-go

  How to implement progress bar and backgroundworker for database calls C#? I do have some methods that deal with large amounts of data. They do last a lot, so in my windows application, i wanna do something to tell users that the data are being processed. So i thought of using progress bar or status strip label, but since there is a single ui thread, the thread where the database-dealing methods are executed, ui controls are not updated, so progress bar or status strip label are useless to me. I've already seen some examples, but they deal with for-loops, ex: for(int i = 0; i < count; i++){ System.Threading.Thread.Sleep(70); // ... do analysis ... bgWorker.ReportProgress((100 * i) / count);} private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e){ progressBar.Value = Math.Min(e.ProgressPercentage, 100);} Can anybody give an example where I can use a method call, not a for-loop, and let the progress bar run while this method is executing??? thnx in advance, any help and hint is highly appreciated.

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• MP3 Decoding on Android

  - by Rob Szumlakowski

  Hi. We're implementing a program for Android phones that plays audio streamed from the internet. Here's approximately what we do: Download a custom encrypted format. Decrypt to get chunks of regular MP3 data. Decode MP3 data to raw PCM data in a memory buffer. Pipe the raw PCM data to an AudioTrack Our target devices so far are Droid and Nexus One. Everything works great on Nexus One, but the MP3 decode is too slow on Droid. The audio playback starts to skip if we put the Droid under load. We are not permitted to decode the MP3 data to SD card, but I know that's not our problem anyways. We didn't write our own MP3 decoder, but used MPADEC (http://sourceforge.net/projects/mpadec/). It's free and was easy to integrate with our program. We compile it with the NDK. After exhaustive analysis with various profiling tools, we're convinced that it's this decoder that is falling behind. Here's the options we're thinking about: Find another MP3 decoder that we can compile with the Android NDK. This MP3 decoder would have to be either optimized to run on mobile ARM devices or maybe use integer-only math or some other optimizations to increase performance. Since the built-in Android MediaPlayer service will take URLs, we might be able to implement a tiny HTTP server in our program and serve the MediaPlayer with the decrypted MP3s. That way we can take advantage of the built-in MP3 decoder. Get access to the built-in MP3 decoder through the NDK. I don't know if this is possible. Does anyone have any suggestions on what we can do to speed up our MP3 decoding? -- Rob Sz

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• EDM -> POCO -> WCF (.NET4) But transferring Collections causes IsReadOnly set to TRUE

  - by Gary B

  Ok, this may sound a little 'unorthodox', but...using VS2010 and the new POCO t4 template for Entity Framework (http://tinyurl.com/y8wnkt2), I can generate nice POCO's. I can then use these POCO's (as DTO's) in a WCF service essentially going from EDM all the way through to the client. Kinda what this guys is doing (http://tinyurl.com/yb4bslv), except everything is generated automatically. I understand that an entity and a DTO 'should' be different, but in this case, I'm handling client and server, and there's some real advantages to having the DTO in the model and automatically generated. My problem is, that when I transfer an entity that has a relationship, the client generated collection (ICollection) has the read-only value set, so I can't manipulate that relationship. For example, retrieving an existing Order, I can't add a product to the Products collection client-side...the Products collection is read-only. I would prefer to do a bunch of client side 'order-editing' and then send the updated order back rather than making dozens of server round trips (eg AddProductToOrder(product)). I'd also prefer not to have a bunch of thunking between Entity and DTO. So all-in-all this looks good to me...except for the read-only part. Is there a solution, or is this too much against the SOA grain?

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