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  • From TFS to Git

    - by Saeed Neamati
    I'm a .NET developer and I've used TFS (team foundation server) as my source control software many times. Good features of TFS are: Good integration with Visual Studio (so I do almost everything visually; no console commands) Easy check-out, check-in process Easy merging and conflict resolution Easy automated builds Branching Now, I want to use Git as the backbone, repository, and source control of my open source projects. My projects are in C#, JavaScript, or PHP language with MySQL, or SQL Server databases as the storage mechanism. I just used github.com's help for this purpose and I created a profile there, and downloaded a GUI for Git. Up to this part was so easy. But I'm almost stuck at going along any further. I just want to do some simple (really simple) operations, including: Creating a project on Git and mapping it to a folder on my laptop Checking out/checking in files and folders Resolving conflicts That's all I need to do now. But it seems that the GUI is not that user friendly. I expect the GUI to have a Connect To... or something like that, and then I expect a list of projects to be shown, and when I choose one, I expect to see the list of files and folders of that project, just like exploring your TFS project in Visual Studio. Then I want to be able to right click a file and select check-in... or check-out and stuff like that. Do I expect much? What should I do to easily use Git just like TFS? What am I missing here?

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  • Help Creating a Google Analytics Funnel for Check out process

    - by Drew
    have a funnel question. I am currently working on tracking (through GA) guest and logged in member activity once they get to my sites shopping cart. But need help with setting up funnels. Specifically to see; Total sales Logged in member total sales List item Guest member sales The urls associated to the check out proces are: Logged in members /cart (arriving to checkout) /checkout (checking out as a logged in member) /checkout/confirmation (thank you - confirmed sale) Guest members - /cart (arriving to checkout) - /checkout-guest (checking out as a guest) - /checkout/confirmation (thanks you - confirmed sale) I've tested the funnels set up for the above with 9 transactions. But the end maths doesn't seem to line up. Total sales funnel shows 9 completed transactions when only tracking these to urls: - /cart - /checkout/confirmation Which is great - cause it's working Logged in member sales show a total of 9 completed transactions based on each step of the logged in url steps (above) being tracked in a funnel. Not good because this number should be 3. Guest check out funnel (see guest steps above) shows 9 as well. What the?!?!?!? The results I am looking for should reflect the following - total sales = 9, logged in members = 3, guest members = 6 Is there any way to set these urls up so that the funnels report the correct results - or do I need to changed the urls and provide logged in members and guest stand alone purchase confirmation pages (this would mean I can not track total sales which combine results from both streams)? Any knowledge in this area is welcome. Thanks.

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  • What exactly do I have to pay attention for when choosing Windows Hosting Provider?

    - by user850010
    This is my first time choosing a hosting company. It is for a web site made in asp.net mvc3. So I was thinking choosing a provider would be easy since I found this page http://www.microsoft.com/web/Hosting/Home which contains hosting offers. Now hours later, I am still searching. The reason is that as soon as I start investigating about particular company, something stands out that I do not like. Here are some examples what I noticed when checking various companies in more detail: Company "about us" page is lacking in information about their company. Few of them had just general description what they do and nothing else, while some others had information like company name but had no address. Checking company name in Business Registry Searches gave no results. Two of the companies I checked had both company name and address but I was unable to find them in the registry. Putting company domain into Google gave mostly results from that domain or web hosting review sites but not much else. I am assuming that good companies should have search results from other sites too. Low Alexa Traffic Rank. There was one company which had a site that looked very professional but their alexa traffic ranking was like 2 million. Are there any other factors I should pay attention to when choosing a hosting company? Do I have legitimate concerns or am I just too paranoid?

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  • I want to be a programmer, work in corporate environment, earn well, learn fast and eventually become a great programmer [on hold]

    - by Shin San
    I'll try to keep this simple: I'm 29, been dabbling with computers for the past 10 years, had entry level jobs in tech support for different apps, been fixing computers for a while and now want to specialize in something. I'm not 100% stranger to programming but haven't gone past if/then/else with anything. A bit of JavaScript, PHP, Python and currently checking out the "SELECT" statement in SQL :)) I'm curious about programming, I enjoy it and I'm thinking of making a living out of it. So, while I'm at it, why not earn a bit more than the average Joe? So, that's why I'm checking what the best solution, the best learning path and the most useful languages are considering: a) how easy/fast can you find a job by knowing it b) how much would I be able to earn c) how fast can I learn it By reading 10-20 articles online I've come up with an example, but I'm here for some expert advice. Example: * ratings from a) and b) point of view #1 sql ; #2 java ; #3 html (please don't start the markup language debate) ; #4 javascript From this ratings, I'd say a good way to go is learn html/css/(javascript or php) for the web part of apps, some SQL/MySQL/whateverSQL for holding data and loads of Java for the program itself. Please let me know if this is a good idea and if so, what should be the order for learning all of the above. Else, please let me know a better way and why it would be better. Many thanks for taking the time to read my question. Best wishes to you guys Edit: if I think Java + SQL + HTML&JavaScript is the way to go, does the order I'm learning them in matter? Or can I try to learn them all at once?

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  • Finding shapes in 2D Array, then optimising

    - by assemblism
    I'm new so I can't do an image, but below is a diagram for a game I am working on, moving bricks into patterns, and I currently have my code checking for rotated instances of a "T" shape of any colour. The X and O blocks would be the same colour, and my last batch of code would find the "T" shape where the X's are, but what I wanted was more like the second diagram, with two "T"s Current result      Desired Result [X][O][O]                [1][1][1] [X][X][_]                [2][1][_] [X][O][_]                [2][2][_] [O][_][_]                [2][_][_] My code loops through x/y, marks blocks as used, rotates the shape, repeats, changes colour, repeats. I have started trying to fix this checking with great trepidation. The current idea is to: loop through the grid and make note of all pattern occurrences (NOT marking blocks as used), and putting these to an array loop through the grid again, this time noting which blocks are occupied by which patterns, and therefore which are occupied by multiple patterns. looping through the grid again, this time noting which patterns obstruct which patterns That much feels right... What do I do now? I think I would have to try various combinations of conflicting shapes, starting with those that obstruct the most other patterns first.How do I approach this one? use the rational that says I have 3 conflicting shapes occupying 8 blocks, and the shapes are 4 blocks each, therefore I can only have a maximum of two shapes. (I also intend to incorporate other shapes, and there will probably be score weighting which will need to be considered when going through the conflicting shapes, but that can be another day) I don't think it's a bin packing problem, but I'm not sure what to look for. Hope that makes sense, thanks for your help

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  • Generic software code style enforcer

    - by FuzziBear
    It seems to me to be a fairly common thing to do, where you have some code that you'd like to automatically run through a code style tool to catch when people break your coding style guide(s). Particularly if you're working on code that has multiple languages (which is becoming more common with web-language-x and javascript), you generally want to apply similar code style guides to both and have them enforced. I've done a bit of research, but I've only been able to find tools to enforce code style guidelines (not necessarily applying the code style, just telling you when you break code style guidelines) for a particular language. It would seem to me a reasonably trivial thing to do by just using current IDE rules for syntax highlighting (so that you don't check style guide rules inside quotes or strings, etc) and a whole lot of regexes to enforce some really generic things. Examples: if ( rather than if( checking lines with only whitespace Are there any tools that do this kind of really generic style checking? I'd prefer it to be easily configurable for different languages (because like it or not, some things would just not work cross language) and to add new "rules" to check new things.

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  • HTG Explains: What Is RSS and How Can I Benefit From Using It?

    - by Jason Fitzpatrick
    If you’re trying to keep up with news and content on multiple web sites, you’re faced with the never ending task of visiting those sites to check for new content. Read on to learn about RSS and how it can deliver the content right to your digital doorstep. In many ways, content on the internet is beautifully linked together and accessible, but despite the interconnectivity of it all we still frequently find ourselves visiting this site, then that site, then another site, all in an effort to check for updates and get the content we want. That’s not particular efficient and there’s a much better way to go about it. Imagine if you will a simple hypothetical situation. You’re a fan of a web comic, a few tech sites, an infrequently updated but excellent blog about an obscure music genre you’re a fan of, and you like to keep an eye on announcements from your favorite video game vendor. If you rely on manually visiting all those sites—and, let’s be honest, our hypothetical example has a scant half-dozen sites while the average person would have many, many, more—then you’re either going to be wasting a lot of time checking the sites every day for new content or you’re going to be missing out on content as you either forget to visit the sites or find the content after it’s not as useful or relevant to you. RSS can break you free from that cycle of either over-checking or under-finding content by delivering the content to you as it is published. Let’s take a look at what RSS is how it can help. HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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  • Buffer System For Items

    - by Ohmages
    I am going to reference this image of what I want to accomplish in JavaScript. This is the Diablo buffer system. This question may be a bit advanced (or possibly not even allowed). But I was wondering how you might go about implementing this type of system in a JavaScript game. Currently to implement such a system in JavaScript escapes me, and I am turning to SO to get some suggestions, ideas, and hopefully some insight in how I could accomplish this without being to costly on the CPU. Some thoughts of mine for implementing such a system would be to: Create DIVS within a DIV that hold each position of the inventory Go through each item you own in a container and see which DIV it belongs to Make said item images the DIVs image This type of system might possibly work if ALL items were 1x1, but for this example its not going to work out. I am at a complete lost of ideas how to even accomplish this. Although, maybe rendering directly to the canvas and checking mouse cords could work, there would more than likely be A HUGE annoyance when checking if other items are overlapping each other (meaning you cant place the item down, and possibly switching item with the cursor item ). That said, what am I left with? Do I need to makeshift my own hack system with messy code, or is there some source out there (that I don't know about) that has replicated this type of system in their own game. I would be very grateful to get some replies on how you might go about doing this, and will accept answers that can logically explain how you might implement such a system (code is not required). P.S. Id like to use pure JavaScript, and nothing else (even though it might be "reinventing the wheel", I also like to learn).

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  • The clock problem - to if or not to if?

    - by trejder
    Let's say, we have a simple digital clock. To "power" it, we use a routine executed every second. We update seconds part in it. But, what about minutes and hours part? What is better / more professional / offers better performance: Ignore all checking and update hour, minute and seconds part each time, every second. Use if + a variable for checking, if 60 (or 3600) seconds passed and update minute / hour part only at that precise moments. This leads us to a question, what is better -- unnecessary drawings (first approach) or extra ifs? I've just spotted a Javascript digital clock, one of millions similar on one of billions pages. And I noticed that all three parts (hours, minutes and seconds) are updated every second, though first changes its value only once per 3600 seconds and second once per 60 seconds. I'm not to experienced developer, so I might me wrong. But everything, what I've learnt up until now, tells me, that if are far better then executing drawing / refreshing sequences only to draw the same content.

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  • SSH asks for password

    - by user1435470
    I have already : Installed the server Generated the pub/pri keys with -P "" Copied the id_rsa.pub to authorized_keys ssh localhost answered "yes", copied to known_hosts tried ssh localhost still asks for password Output: hduser@hduser1-desktop:~$ ssh -v localhost OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to localhost [127.0.0.1] port 22. debug1: Connection established. debug1: identity file /home/hduser/.ssh/identity type -1 debug1: identity file /home/hduser/.ssh/id_rsa type 1 debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048 debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048 debug1: identity file /home/hduser/.ssh/id_dsa type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3p1 Debian- 3ubuntu7 debug1: match: OpenSSH_5.3p1 Debian-3ubuntu7 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'localhost' is known and matches the RSA host key. debug1: Found key in /home/hduser/.ssh/known_hosts:3 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,password debug1: Next authentication method: publickey debug1: Offering public key: /home/hduser/.ssh/id_rsa debug1: Authentications that can continue: publickey,password debug1: Trying private key: /home/hduser/.ssh/identity debug1: Trying private key: /home/hduser/.ssh/id_dsa debug1: Next authentication method: password Any suggestions ? Cheers

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  • Need efficient way to keep enemy from getting hit multiple times by same source

    - by TenFour04
    My game's a simple 2D one, but this probably applies to many types of scenarios. Suppose my player has a sword, or a gun that shoots a projectile that can pass through and hit multiple enemies. While the sword is swinging, there is a duration where I am checking for the sword making contact with any enemy on every frame. But once an enemy is hit by that sword, I don't want him to continue getting hit over and over as the sword follows through. (I do want the sword to continue checking whether it is hitting other enemies.) I've thought of a couple different approaches (below), but they don't seem like good ones to me. I'm looking for a way that doesn't force cross-referencing (I don't want the enemy to have to send a message back to the sword/projectile). And I'd like to avoid generating/resetting multiple array lists with every attack. Each time the sword swings it generates a unique id (maybe by just incrementing a global static long). Every enemy keeps a list of id's of swipes or projectiles that have already hit them, so the enemy knows not to get hurt by something multiple times. Downside is that every enemy may have a big list to compare to. So projectiles and sword swipes would have to broadcast their end-of-life to all enemies and cause a search and remove on every enemy's array list. Seems kind of slow. Each sword swipe or projectile keeps its own list of enemies that it has already hit so it knows not to apply damage. Downsides: Have to generate a new list (probably pull from a pool and clear one) every time a sword is swung or a projectile shot. Also, this breaks down modularity, because now the sword has to send a message to the enemy, and the enemy has to send a message back to the sword. Seems to me that two-way streets like this are a great way to create very difficult-to-find bugs.

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  • How to start Ubuntu with no working video card?

    - by ViliusK
    I have a laptop with broken video card. It has two operating systems installed - Windows 7 and Ubuntu 10.10 Desktop Edition. It has GRUB to manage which operating system to boot up. Windows is default OS. And Windows fails to boot up without video card. I'm checking with ping to the ports which are shown as used by DHCP in my router. Normal boot of Ubuntu also fails and it restarts after a while. But when I choose (blindly, but checking HDD indicator and by counting button presses when GRUB menu appears) to boot second option of Ubuntu (rescue mode) it starts and I can ping it. But when I try to connect to it through SSH, I'm getting "connection refused" error from putty. I've took out HDD from my laptop already and inserted it to WD Passport case so now I can connect it to other computer to edit configuration files. How can I check if SSH server is working? How to enable it in rescue mode? Or better, how to disable video card to be required while booting Ubuntu in normal mode?

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  • XML Rules Engine and Validation Tutorial with NIEM

    - by drrwebber
    Our new XML Validation Framework tutorial video is now available. See how to easily integrate code-free adaptive XML validation services into your web services using the Java CAMV validation engine. CAMV allows you to build fault tolerant content checking with XPath that optionally use SQL data lookups. This can provide warnings as well as error conditions to tailor your validation layer to exactly meet your business application needs. Also available is developing test suites using Apache ANT scripting of validations.  This allows a community to share sets of conformance checking test and tools . On the technical XML side the video introduces XPath validation rules and illustrates and the concepts of XML content and structure validation. CAM validation templates allow contextual parameter driven dynamic validation services to be implemented compared to using a static and brittle XSD schema approach.The SQL table lookup and code list validation are discussed and examples presented.Features are highlighted along with a demonstration of the interactive generation of actual live XML data from a SQL data store and then validation processing complete with errors and warnings detection.The presentation provides a primer for developing web service XML validation and integration into a SOA approach along with examples and resources. Also alignment with the NIEM IEPD process for interoperable information exchanges is discussed along with NIEM rules services.The CAMV engine is a high performance scalable Java component for rapidly implementing code-free validation services and methods. CAMV is a next generation WYSIWYG approach that builds from older Schematron coding based interpretative runtime tools and provides a simpler declarative metaphor for rules definition. See: http://www.youtube.com/user/TheCAMeditor

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  • Dom U Installation on Ubuntu 11.10

    - by sridutt
    I am trying to add a DomU Operating system on Ubuntu 11.10. I have successfully installed Xen. Verified with xm info virsh-version which returns: Compiled against library: libvir 0.9.2 Using library: libvir 0.9.2 Using API: Xen 3.0.1 Running hypervisor: Xen 4.1. Now when I tried to install Dom0 it said: unable to connect to 'localhost:8000': , in VMM. So, I followed this bug link. I could now start adding DomU. When adding DomU, in last stage, it gives the following error: Unable to complete install: 'POST operation failed: xend_post: error from xen daemon: (xend.err "Error creating domain: device model '/usr/lib/xen/bin/qemu-dm' not found")' Traceback (most recent call last): File "/usr/share/virt-manager/virtManager/asyncjob.py", line 44, in cb_wrapper callback(asyncjob, *args, **kwargs) File "/usr/share/virt-manager/virtManager/create.py", line 1899, in do_install guest.start_install(False, meter=meter) File "/usr/lib/pymodules/python2.7/virtinst/Guest.py", line 1223, in start_install noboot) File "/usr/lib/pymodules/python2.7/virtinst/Guest.py", line 1291, in _create_guest dom = self.conn.createLinux(start_xml or final_xml, 0) File "/usr/lib/python2.7/dist-packages/libvirt.py", line 1686, in createLinux if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self) libvirtError: POST operation failed: xend_post: error from xen daemon: (xend.err "Error creating domain: device model '/usr/lib/xen/bin/qemu-dm' not found") I tried following this bug link that said, the bug is solved in the below package. When I run ./configure in this, I am getting an error: checking for LIBXML... no checking libxml2 xml2-config >= 2.6.0 ... configure: error: Could not find libxml2 anywhere (see config.log for details). What is the problem?

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  • Using 2d collision with 3d objects

    - by Lyise
    I'm planning to write a fairly basic scrolling shoot 'em up, however, I have run into a query with regards to checking for collision. I plan to have a fixed top down view, where the player and enemies are all 3d objects on a fixed plane, and when the enemy or player fires at the other, their shots will also be along this fixed plane. In order to handle the collision, I have read up a bit on collision detection in 3d, as it is not something I have looked into previously, but I'm not sure what would be ideal for this situation. My options appear to be: Sphere collision, however, this lacks the pixel precision I would like Detection using all vertexes and planes of each object, but this seems overly convoluted for a fixed plane of play Rendering the play screen in black and white (where white is an object, black is empty space), once for enemies and once for the player, and checking for collisions that way (if a pixel is white on both, there is a collision) Which of these would be the best approach, or is there another option that I am missing? I have done this previously using 2d sprites, however I can't use the same thinking here as I don't have the image to refer to.

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  • Do there exist programming languages where a variable can truly know its own name?

    - by Job
    In PHP and Python one can iterate over the local variables and, if there is only once choice where the value matches, you could say that you know what the variable's name is, but this does not always work. Machine code does not have variable names. C compiles to assembly and does not have any native reflection capabilities, so it would not know it's name. (Edit: per Anton's answer the pre-processor can know the variable's name). Do there exist programming languages where a variable would know it's name? It gets tricky if you do something like b = a and b does not become a copy of a but a reference to the same place. EDIT: Why in the world would you want this? I can think of one example: error checking that can survive automatic refactoring. Consider this C# snippet: private void CheckEnumStr(string paramName, string paramValue) { if (paramName != "pony" && paramName != "horse") { string exceptionMessage = String.Format( "Unexpected value '{0}' of the parameter named '{1}'.", paramValue, paramName); throw new ArgumentException(exceptionMessage); } } ... CheckEnumStr("a", a); // Var 'a' does not know its name - this will not survive naive auto-refactoring There are other libraries provided by Microsoft and others that allow to check for errors (sorry the names have escaped me). I have seen one library which with the help of closures/lambdas can accomplish error checking that can survive refactoring, but it does not feel idiomatic. This would be one reason why I might want a language where a variable knows its name.

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  • share code between check and process methods

    - by undu
    My job is to refactor an old library for GIS vector data processing. The main class encapsulates a collection of building outlines, and offers different methods for checking data consistency. Those checking functions have an optional parameter that allows to perform some process. For instance: std::vector<Point> checkIntersections(int process_mode = 0); This method tests if some building outlines are intersecting, and return the intersection points. But if you pass a non null argument, the method will modify the outlines to remove the intersection. I think it's pretty bad (at call site, a reader not familiar with the code base will assume that a method called checkSomething only performs a check and doesn't modifiy data) and I want to change this. I also want to avoid code duplication as check and process methods are mostly similar. So I was thinking to something like this: // a private worker std::vector<Point> workerIntersections(int process_mode = 0) { // it's the equivalent of the current checkIntersections, it may perform // a process depending on process_mode } // public interfaces for check and process std::vector<Point> checkIntersections() /* const */ { workerIntersections(0); } std::vector<Point> processIntersections(int process_mode /*I have different process modes*/) { workerIntersections(process_mode); } But that forces me to break const correctness as workerIntersections is a non-const method. How can I separate check and process, avoiding code duplication and keeping const-correctness?

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  • What Counts For a DBA: Simplicity

    - by Louis Davidson
    Too many computer processes do an apparently simple task in a bizarrely complex way. They remind me of this strip by one of my favorite artists: Rube Goldberg. In order to keep the boss from knowing one was late, a process is devised whereby the cuckoo clock kisses a live cuckoo bird, who then pulls a string, which triggers a hat flinging, which in turn lands on a rod that removes a typewriter cover…and so on. We rely on creating automated processes to keep on top of tasks. DBAs have a lot of tasks to perform: backups, performance tuning, data movement, system monitoring, and of course, avoiding being noticed.  Every day, there are many steps to perform to maintain the database infrastructure, including: checking physical structures, re-indexing tables where needed, backing up the databases, checking those backups, running the ETL, and preparing the daily reports and yes, all of these processes have to complete before you can call it a day, and probably before many others have started that same day. Some of these tasks are just naturally complicated on their own. Other tasks become complicated because the database architecture is excessively rigid, and we often discover during “production testing” that certain processes need to be changed because the written requirements barely resembled the actual customer requirements.   Then, with no time to change that rigid structure, we are forced to heap layer upon layer of code onto the problematic processes. Instead of a slight table change and a new index, we end up with 4 new ETL processes, 20 temp tables, 30 extra queries, and 1000 lines of SQL code.  Report writers then need to build reports and make magical numbers appear from those toxic data structures that are overly complex and probably filled with inconsistent data. What starts out as a collection of fairly simple tasks turns into a Goldbergian nightmare of daily processes that are likely to cause your dinner to be interrupted by the smartphone doing the vibration dance that signifies trouble at the mill. So what to do? Well, if it is at all possible, simplify the problem by either going into the code and refactoring the complex code to simple, or taking all of the processes and simplifying them into small, independent, easily-tested steps.  The former approach usually requires an agreement on changing underlying structures that requires countless mind-numbing meetings; while the latter can generally be done to any complex process without the same frustration or anger, though it will still leave you with lots of steps to complete, the ability to test each step independently will definitely increase the quality of the overall process (and with each step reporting status back, finding an actual problem within the process will be definitely less unpleasant.) We all know the principle behind simplifying a sequence of processes because we learned it in math classes in our early years of attending school, starting with elementary school. In my 4 years (ok, 9 years) of undergraduate work, I remember pretty much one thing from my many math classes that I apply daily to my career as a data architect, data programmer, and as an occasional indentured DBA: “show your work”. This process of showing your work was my first lesson in simplification. Each step in the process was in fact, far simpler than the entire process.  When you were working an equation that took both sides of 4 sheets of paper, showing your work was important because the teacher could see every step, judge it, and mark it accordingly.  So often I would make an error in the first few lines of a problem which meant that the rest of the work was actually moving me closer to a very wrong answer, no matter how correct the math was in the subsequent steps. Yet, when I got my grade back, I would sometimes be pleasantly surprised. I passed, yet missed every problem on the test. But why? While I got the fact that 1+1=2 wrong in every problem, the teacher could see that I was using the right process. In a computer process, the process is very similar. We take complex processes, show our work by storing intermediate values, and test each step independently. When a process has 100 steps, each step becomes a simple step that is tested and verified, such that there will be 100 places where data is stored, validated, and can be checked off as complete. If you get step 1 of 100 wrong, you can fix it and be confident (that if you did your job of testing the other steps better than the one you had to repair,) that the rest of the process works. If you have 100 steps, and store the state of the process exactly once, the resulting testable chunk of code will be far more complex and finding the error will require checking all 100 steps as one, and usually it would be easier to find a specific needle in a stack of similarly shaped needles.  The goal is to strive for simplicity either in the solution, or at least by simplifying every process down to as many, independent, testable, simple tasks as possible.  For the tasks that really can’t be done completely independently, minimally take those tasks and break them down into simpler steps that can be tested independently.  Like working out division problems longhand, have each step of the larger problem verified and tested.

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  • PASS Summit 2011 &ndash; Part III

    - by Tara Kizer
    Well we’re about a month past PASS Summit 2011, and yet I haven’t finished blogging my notes! Between work and home life, I haven’t been able to come up for air in a bit.  Now on to my notes… On Thursday of the PASS Summit 2011, I attended Klaus Aschenbrenner’s (blog|twitter) “Advanced SQL Server 2008 Troubleshooting”, Joe Webb’s (blog|twitter) “SQL Server Locking & Blocking Made Simple”, Kalen Delaney’s (blog|twitter) “What Happened? Exploring the Plan Cache”, and Paul Randal’s (blog|twitter) “More DBA Mythbusters”.  I think my head grew two times in size from the Thursday sessions.  Just WOW! I took a ton of notes in Klaus' session.  He took a deep dive into how to troubleshoot performance problems.  Here is how he goes about solving a performance problem: Start by checking the wait stats DMV System health Memory issues I/O issues I normally start with blocking and then hit the wait stats.  Here’s the wait stat query (Paul Randal’s) that I use when working on a performance problem.  He highlighted a few waits to be aware of such as WRITELOG (indicates IO subsystem problem), SOS_SCHEDULER_YIELD (indicates CPU problem), and PAGEIOLATCH_XX (indicates an IO subsystem problem or a buffer pool problem).  Regarding memory issues, Klaus recommended that as a bare minimum, one should set the “max server memory (MB)” in sp_configure to 2GB or 10% reserved for the OS (whichever comes first).  This is just a starting point though! Regarding I/O issues, Klaus talked about disk partition alignment, which can improve SQL I/O performance by up to 100%.  You should use 64kb for NTFS cluster, and it’s automatic in Windows 2008 R2. Joe’s locking and blocking presentation was a good session to really clear up the fog in my mind about locking.  One takeaway that I had no idea could be done was that you can set a timeout in T-SQL code view LOCK_TIMEOUT.  If you do this via the application, you should trap error 1222. Kalen’s session went into execution plans.  The minimum size of a plan is 24k.  This adds up fast especially if you have a lot of plans that don’t get reused much.  You can use sys.dm_exec_cached_plans to check how often a plan is being reused by checking the usecounts column.  She said that we can use DBCC FLUSHPROCINDB to clear out the stored procedure cache for a specific database.  I didn’t know we had this available, so this was great to hear.  This will be less intrusive when an emergency comes up where I’ve needed to run DBCC FREEPROCCACHE. Kalen said one should enable “optimize for ad hoc workloads” if you have an adhoc loc.  This stores only a 300-byte stub of the first plan, and if it gets run again, it’ll store the whole thing.  This helps with plan cache bloat.  I have a lot of systems that use prepared statements, and Kalen says we simulate those calls by using sp_executesql.  Cool! Paul did a series of posts last year to debunk various myths and misconceptions around SQL Server.  He continues to debunk things via “DBA Mythbusters”.  You can get a PDF of a bunch of these here.  One of the myths he went over is the number of tempdb data files that you should have.  Back in 2000, the recommendation was to have as many tempdb data files as there are CPU cores on your server.  This no longer holds true due to the numerous cores we have on our servers.  Paul says you should start out with 1/4 to 1/2 the number of cores and work your way up from there.  BUT!  Paul likes what Bob Ward (twitter) says on this topic: 8 or less cores –> set number of files equal to the number of cores Greater than 8 cores –> start with 8 files and increase in blocks of 4 One common myth out there is to set your MAXDOP to 1 for an OLTP workload with high CXPACKET waits.  Instead of that, dig deeper first.  Look for missing indexes, out-of-date statistics, increase the “cost threshold for parallelism” setting, and perhaps set MAXDOP at the query level.  Paul stressed that you should not plan a backup strategy but instead plan a restore strategy.  What are your recoverability requirements?  Once you know that, now plan out your backups. As Paul always does, he talked about DBCC CHECKDB.  He said how fabulous it is.  I didn’t want to interrupt the presentation, so after his session had ended, I asked Paul about the need to run DBCC CHECKDB on your mirror systems.  You could have data corruption occur at the mirror and not at the principal server.  If you aren’t checking for data corruption on your mirror systems, you could be failing over to a corrupt database in the case of a disaster or even a planned failover.  You can’t run DBCC CHECKDB against the mirrored database, but you can run it against a snapshot off the mirrored database.

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  • Clean way to use mutable implementation of Immutable interfaces for encapsulation

    - by dsollen
    My code is working on some compost relationship which creates a tree structure, class A has many children of type B, which has many children of type C etc. The lowest level class, call it bar, also points to a connected bar class. This effectively makes nearly every object in my domain inter-connected. Immutable objects would be problematic due to the expense of rebuilding almost all of my domain to make a single change to one class. I chose to go with an interface approach. Every object has an Immutable interface which only publishes the getter methods. I have controller objects which constructs the domain objects and thus has reference to the full objects, thus capable of calling the setter methods; but only ever publishes the immutable interface. Any change requested will go through the controller. So something like this: public interface ImmutableFoo{ public Bar getBar(); public Location getLocation(); } public class Foo implements ImmutableFoo{ private Bar bar; private Location location; @Override public Bar getBar(){ return Bar; } public void setBar(Bar bar){ this.bar=bar; } @Override public Location getLocation(){ return Location; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); if(foo!=null) foo.addBar(bar); return foo; } } I felt the basic approach seems sensible, however, when I speak to others they always seem to have trouble envisioning what I'm describing, which leaves me concerned that I may have a larger design issue then I'm aware of. Is it problematic to have domain objects so tightly coupled, or to use the quasi-mutable approach to modifying them? Assuming that the design approach itself isn't inherently flawed the particular discussion which left me wondering about my approach had to do with the presence of business logic in the domain objects. Currently I have my setter methods in the mutable objects do error checking and all other logic required to verify and make a change to the object. It was suggested that this should be pulled out into a service class, which applies all the business logic, to simplify my domain objects. I understand the advantage in mocking/testing and general separation of logic into two classes. However, with a service method/object It seems I loose some of the advantage of polymorphism, I can't override a base class to add in new error checking or business logic. It seems, if my polymorphic classes were complicated enough, I would end up with a service method that has to check a dozen flags to decide what error checking and business logic applies. So, for example, if I wanted to have a childFoo which also had a size field which should be compared to bar before adding par my current approach would look something like this. public class Foo implements ImmutableFoo{ public void addBar(Bar bar){ if(!getLocation().equals(bar.getLocation()) throw new LocationException(); this.bar=bar; } } public interface ImmutableChildFoo extends ImmutableFoo{ public int getSize(); } public ChildFoo extends Foo implements ImmutableChildFoo{ private int size; @Override public int getSize(){ return size; } @Override public void addBar(Bar bar){ if(getSize()<bar.getSize()){ throw new LocationException(); super.addBar(bar); } My colleague was suggesting instead having a service object that looks something like this (over simplified, the 'service' object would likely be more complex). public interface ImmutableFoo{ ///original interface, presumably used in other methods public Location getLocation(); public boolean isChildFoo(); } public interface ImmutableSizedFoo implements ImmutableFoo{ public int getSize(); } public class Foo implements ImmutableSizedFoo{ public Bar bar; @Override public void addBar(Bar bar){ this.bar=bar; } @Override public int getSize(){ //default size if no size is known return 0; } @Override public boolean isChildFoo return false; } } public ChildFoo extends Foo{ private int size; @Override public int getSize(){ return size; } @Override public boolean isChildFoo(); return true; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableSizedFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); service.addBarToFoo(foo, bar); returned foo; } public class Service{ public static void addBarToFoo(Foo foo, Bar bar){ if(foo==null) return; if(!foo.getLocation().equals(bar.getLocation())) throw new LocationException(); if(foo.isChildFoo() && foo.getSize()<bar.getSize()) throw new LocationException(); foo.setBar(bar); } } } Is the recommended approach of using services and inversion of control inherently superior, or superior in certain cases, to overriding methods directly? If so is there a good way to go with the service approach while not loosing the power of polymorphism to override some of the behavior?

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  • Physics System ignores collision in some rare cases

    - by Gajoo
    I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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  • Example: Controlling randomizer using code contracts

    - by DigiMortal
    One cool addition to Visual Studio 2010 is support for code contracts. Code contracts make sure that all conditions under what method is supposed to run correctly are met. Those who are familiar with unit tests will find code contracts easy to use. In this posting I will show you simple example about static contract checking (example solution is included). To try out code contracts you need at least Visual Studio 2010 Standard Edition. Also you need code contracts package. You can download package from DevLabs Code Contracts page. NB! Speakers, you can use the example solution in your presentations as long as you mention me and this blog in your sessions. Solution has readme.txt file that gives you steps to go through when presenting solution in sessions. This blog posting is companion posting for Visual Studio solution referred below. As an example let’s look at the following class. public class Randomizer {     public static int GetRandomFromRange(int min, int max)     {         var rnd = new Random();         return rnd.Next(min, max);     }       public static int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires(min < max, "Min must be less than max");           var rnd = new Random();         return rnd.Next(min, max);     } } GetRandomFromRange() method returns results without any checking. GetRandomFromRangeContracted() uses one code contract that makes sure that minimum value is less than maximum value. Now let’s run the following code. class Program {     static void Main(string[] args)     {         var random1 = Randomizer.GetRandomFromRange(0, 9);         Console.WriteLine("Random 1: " + random1);           var random2 = Randomizer.GetRandomFromRange(1, 1);         Console.WriteLine("Random 2: " + random2);           var random3 = Randomizer.GetRandomFromRangeContracted(5, 5);         Console.WriteLine("Random 3: " + random3);           Console.WriteLine(" ");         Console.WriteLine("Press any key to exit ...");         Console.ReadKey();     } } As we have not turned on support for code contracts the code runs without any problems and we get no warnings by Visual Studio that something is wrong. Now let’s turn on static checking for code contracts. As you can see then code still compiles without any errors but Visual Studio warns you about possible problems with contracts. Click on image to see it at original size.  When we open Error list and run our application we get the following output to errors list. Note that these messages are not shown immediately. There is little delay between application starting and appearance of these messages. So wait couple of seconds before going out of your mind. Click on image to see it at original size.  If you look at these warnings you can see that warnings show you illegal calls and also contracts against what they are going. Third warning points to GetRandomFromRange() method and shows that there should be also problem that can be detected by contract. Download Code Contracts example VS2010 solution | 30KB

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  • java.util.zip.ZipException: Error opening file When Deploying an Application to Weblogic Server

    - by lmestre
    The latest weeks we had a hard time trying to solve a deployment issue.* WebLogic Server 10.3.6* Target: WLS Cluster<21-10-2013 05:29:40 PM CLST> <Error> <Console> <BEA-240003> <Console encountered the following error weblogic.management.DeploymentException:        at weblogic.servlet.internal.WarDeploymentFactory.findOrCreateComponentMBeans(WarDeploymentFactory.java:69)        at weblogic.application.internal.MBeanFactoryImpl.findOrCreateComponentMBeans(MBeanFactoryImpl.java:48)        at weblogic.application.internal.MBeanFactoryImpl.createComponentMBeans(MBeanFactoryImpl.java:110)        at weblogic.application.internal.MBeanFactoryImpl.initializeMBeans(MBeanFactoryImpl.java:76)        at weblogic.management.deploy.internal.MBeanConverter.createApplicationMBean(MBeanConverter.java:89)        at weblogic.management.deploy.internal.MBeanConverter.createApplicationForAppDeployment(MBeanConverter.java:67)        at weblogic.management.deploy.internal.MBeanConverter.setupNew81MBean(MBeanConverter.java:315)        at weblogic.deploy.internal.targetserver.operations.ActivateOperation.compatibilityProcessor(ActivateOperation.java:81)        at weblogic.deploy.internal.targetserver.operations.AbstractOperation.setupPrepare(AbstractOperation.java:295)        at weblogic.deploy.internal.targetserver.operations.ActivateOperation.doPrepare(ActivateOperation.java:97)        at weblogic.deploy.internal.targetserver.operations.AbstractOperation.prepare(AbstractOperation.java:217)        at weblogic.deploy.internal.targetserver.DeploymentManager.handleDeploymentPrepare(DeploymentManager.java:747)        at weblogic.deploy.internal.targetserver.DeploymentManager.prepareDeploymentList(DeploymentManager.java:1216)        at weblogic.deploy.internal.targetserver.DeploymentManager.handlePrepare(DeploymentManager.java:250)        at weblogic.deploy.internal.targetserver.DeploymentServiceDispatcher.prepare(DeploymentServiceDispatcher.java:159)        at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.doPrepareCallback(DeploymentReceiverCallbackDeliverer.java:171)        at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.access$000(DeploymentReceiverCallbackDeliverer.java:13)        at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer$1.run(DeploymentReceiverCallbackDeliverer.java:46)        at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:545)        at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)        at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)Caused by: java.util.zip.ZipException: Error opening file - C:\Oracle\Middleware\user_projects\domains\MyDomain\servers\MyServer\stage\myapp\myapp.war Message - error in opening zip file        at weblogic.servlet.utils.WarUtils.existsInWar(WarUtils.java:87)        at weblogic.servlet.utils.WarUtils.isWebServices(WarUtils.java:76)        at weblogic.servlet.internal.WarDeploymentFactory.findOrCreateComponentMBeans(WarDeploymentFactory.java:61) So the first idea you have with that error is that the war file is corrupted or has incorrect privileges.        We tried:1. Unzipping the  war file, the file was perfect.2. Checking the size, same size as in other environments.3. Checking the ownership of the file, same as in other environments.4. Checking the permissions of the file, same as other applications.Then we accepted the file was fine, so we tried enabling some deployment debugs, but no clues.We also tried:1. Delete all contents of <MyDomain/servers/<MyServer>/tmp> a and <MyDomain/servers/<MyServer>/cache> folders, the issue persisted.2. When renaming the application the deployment was sucessful3. When targeting to the Admin Server, deployment was also working.4. Using 'Copy this application onto every target for me' didn't help either.Finally, my friend 'Test Case' solved the issue again.I saw this name in the config.xml<jdbc-system-resource>    <name>myapp</name>    <target></target>    <descriptor-file-name>jdbc/myapp-jdbc.xml</descriptor-file-name>  </jdbc-system-resource> So, it turned out that customer had created a DataSource with the same name as the application 'myapp' in the above example.By deleting the datasource and created another exact DataSource with a different name the issue was solved.At this point, Do you know Why 'java.util.zip.ZipException: Error opening file' was occurring?Because all names is WebLogic Server need to be unique.References: http://docs.oracle.com/cd/E23943_01/web.1111/e13709/setup.htm"Assigning Names to WebLogic Server ResourcesMake sure that each configurable resource in your WebLogic Server environment has a unique name. Each, domain, server, machine, cluster, JDBC data source, virtual host, or other resource must have a unique name." Enjoy!

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  • Applications: The Mathematics of Movement, Part 3

    - by TechTwaddle
    Previously: Part 1, Part 2 As promised in the previous post, this post will cover two variations of the marble move program. The first one, Infinite Move, keeps the marble moving towards the click point, rebounding it off the screen edges and changing its direction when the user clicks again. The second version, Finite Move, is the same as first except that the marble does not move forever. It moves towards the click point, rebounds off the screen edges and slowly comes to rest. The amount of time that it moves depends on the distance between the click point and marble. Infinite Move This case is simple (actually both cases are simple). In this case all we need is the direction information which is exactly what the unit vector stores. So when the user clicks, you calculate the unit vector towards the click point and then keep updating the marbles position like crazy. And, of course, there is no stop condition. There’s a little more additional code in the bounds checking conditions. Whenever the marble goes off the screen boundaries, we need to reverse its direction.  Here is the code for mouse up event and UpdatePosition() method, //stores the unit vector double unitX = 0, unitY = 0; double speed = 6; //speed times the unit vector double incrX = 0, incrY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = e.X - marble1.x;     double y = e.Y - marble1.y;     //calculate distance between click point and current marble position     double lenSqrd = x * x + y * y;     double len = Math.Sqrt(lenSqrd);     //unit vector along the same direction (from marble towards click point)     unitX = x / len;     unitY = y / len;     timer1.Enabled = true; } private void UpdatePosition() {     //amount by which to increment marble position     incrX = speed * unitX;     incrY = speed * unitY;     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     } } So whenever the user clicks we calculate the unit vector along that direction and also the amount by which the marble position needs to be incremented. The speed in this case is fixed at 6. You can experiment with different values. And under bounds checking, whenever the marble position goes out of bounds along the x or y direction we reverse the direction of the unit vector along that direction. Here’s a video of it running;   Finite Move The code for finite move is almost exactly same as that of Infinite Move, except for the difference that the speed is not fixed and there is an end condition, so the marble comes to rest after a while. Code follows, //unit vector along the direction of click point double unitX = 0, unitY = 0; //speed of the marble double speed = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = 0, y = 0;     double lengthSqrd = 0, length = 0;     x = e.X - marble1.x;     y = e.Y - marble1.y;     lengthSqrd = x * x + y * y;     //length in pixels (between click point and current marble pos)     length = Math.Sqrt(lengthSqrd);     //unit vector along the same direction as vector(x, y)     unitX = x / length;     unitY = y / length;     speed = length / 12;     timer1.Enabled = true; } private void UpdatePosition() {     marble1.x += speed * unitX;     marble1.y += speed * unitY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     }     //reduce speed by 3% in every loop     speed = speed * 0.97f;     if ((int)speed <= 0)     {         timer1.Enabled = false;     } } So the only difference is that the speed is calculated as a function of length when the mouse up event occurs. Again, this can be experimented with. Bounds checking is same as before. In the update and draw cycle, we reduce the speed by 3% in every cycle. Since speed is calculated as a function of length, speed = length/12, the amount of time it takes speed to reach zero is directly proportional to length. Note that the speed is in ‘pixels per 40ms’ because the timeout value of the timer is 40ms.  The readability can be improved by representing speed in ‘pixels per second’. This would require you to add some more calculations to the code, which I leave out as an exercise. Here’s a video of this second version,

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  • Efficient Way to Draw Grids in XNA

    - by sm81095
    So I am working on a game right now, using Monogame as my framework, and it has come time to render my world. My world is made up of a grid (think Terraria but top-down instead of from the side), and it has multiple layers of grids in a single world. Knowing how inefficient it is to call SpriteBatch.Draw() a lot of times, I tried to implement a system where the tile would only be drawn if it wasn't hidden by the layers above it. The problem is, I'm getting worse performance by checking if it's hidden than when I just let everything draw even if it's not visible. So my question is: how to I efficiently check if a tile is hidden to cut down on the draw() calls? Here is my draw code for a single layer, drawing floors, and then the tiles (which act like walls): public void Draw(GameTime gameTime) { int drawAmt = 0; int width = Tile.TILE_DIM; int startX = (int)_parent.XOffset; int startY = (int)_parent.YOffset; //Gets the starting tiles and the dimensions to draw tiles, so only onscreen tiles are drawn, allowing for the drawing of large worlds int tileDrawWidth = ((CIGame.Instance.Graphics.PreferredBackBufferWidth / width) + 4); int tileDrawHeight = ((CIGame.Instance.Graphics.PreferredBackBufferHeight / width) + 4); int tileStartX = (int)MathHelper.Clamp((-startX / width) - 2, 0, this.Width); int tileStartY = (int)MathHelper.Clamp((-startY / width) - 2, 0, this.Height); #region Draw Floors and Tiles CIGame.Instance.GraphicsDevice.SetRenderTarget(_worldTarget); CIGame.Instance.GraphicsDevice.Clear(Color.Black); CIGame.Instance.SpriteBatch.Begin(); //Draw floors for (int x = tileStartX; x < (int)MathHelper.Clamp(tileStartX + tileDrawWidth, 0, this.Width); x++) { for (int y = tileStartY; y < (int)MathHelper.Clamp(tileStartY + tileDrawHeight, 0, this.Height); y++) { //Check if this tile is hidden by layer above it bool visible = true; for (int i = this.LayerNumber; i <= _parent.ActiveLayer; i++) { if (this.LayerNumber != (_parent.Layers - 1) && (_parent.GetTileAt(x, y, i + 1).Opacity >= 1.0f || _parent.GetFloorAt(x, y, i + 1).Opacity >= 1.0f)) { visible = false; break; } } //Only draw if visible under the tile above it if (visible && this.GetTileAt(x, y).Opacity < 1.0f) { Texture2D tex = WorldTextureManager.GetFloorTexture((Floor)_floors[x, y]); Rectangle source = WorldTextureManager.GetSourceForIndex(((Floor)_floors[x, y]).GetTextureIndexFromSurroundings(x, y, this), tex); Rectangle draw = new Rectangle(startX + x * width, startY + y * width, width, width); CIGame.Instance.SpriteBatch.Draw(tex, draw, source, Color.White * ((Floor)_floors[x, y]).Opacity); drawAmt++; } } } //Draw tiles for (int x = tileStartX; x < (int)MathHelper.Clamp(tileStartX + tileDrawWidth, 0, this.Width); x++) { for (int y = tileStartY; y < (int)MathHelper.Clamp(tileStartY + tileDrawHeight, 0, this.Height); y++) { //Check if this tile is hidden by layers above it bool visible = true; for (int i = this.LayerNumber; i <= _parent.ActiveLayer; i++) { if (this.LayerNumber != (_parent.Layers - 1) && (_parent.GetTileAt(x, y, i + 1).Opacity >= 1.0f || _parent.GetFloorAt(x, y, i + 1).Opacity >= 1.0f)) { visible = false; break; } } if (visible) { Texture2D tex = WorldTextureManager.GetTileTexture((Tile)_tiles[x, y]); Rectangle source = WorldTextureManager.GetSourceForIndex(((Tile)_tiles[x, y]).GetTextureIndexFromSurroundings(x, y, this), tex); Rectangle draw = new Rectangle(startX + x * width, startY + y * width, width, width); CIGame.Instance.SpriteBatch.Draw(tex, draw, source, Color.White * ((Tile)_tiles[x, y]).Opacity); drawAmt++; } } } CIGame.Instance.SpriteBatch.End(); Console.WriteLine(drawAmt); CIGame.Instance.GraphicsDevice.SetRenderTarget(null); //TODO: Change to new rendertarget instead of null #endregion } So I was wondering if this is an efficient way, but I'm going about it wrongly, or if there is a different, more efficient way to check if the tiles are hidden. EDIT: For example of how much it affects performance: using a world with three layers, allowing everything to draw no matter what gives me 60FPS, but checking if its visible with all of the layers above it gives me only 20FPS, while checking only the layer immediately above it gives me a fluctuating FPS between 30 and 40FPS.

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