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  • Client Side Prediction for a Look Vector

    - by Mike Sawayda
    So I am making a first person networked shooter. I am working on client-side prediction where I am predicting player position and look vectors client-side based on input messages received from the server. Right now I am only worried about the look vectors though. I am receiving the correct look vector from the server about 20 times per second and I am checking that against the look vector that I have client side. I want to interpolate the clients look vector towards the correct one that is server side over a period of time. Therefore no matter how far you are away from the servers look vector you will interpolate to it over the same amount of time. Ex. if you were 10 degrees off it would take the same amount of time as if you were 2 degrees off to be correctly lined up with the server copy. My code looks something like this but the problem is that the amount that you are changing the clients copy gets infinitesimally small so you will actually never reach the servers copy. This is because I am always calculating the difference and only moving by a percentage of that every frame. Does anyone have any suggestions on how to interpolate towards the servers copy correctly? if(rotationDiffY > ClientSideAttributes::minRotation) { if(serverRotY > clientRotY) { playerObjects[i]->collisionObject->rotation.y += (rotationDiffY * deltaTime); } else { playerObjects[i]->collisionObject->rotation.y -= (rotationDiffY deltaTime); } }

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  • Grub2 attempting to boot hd1 when it should boot hd0

    - by JoBu1324
    I'm attempting to perform a "normal" install on a USB3 SSD (I don't know if it is noteworthy, but I don't have a swap partition). The installation proceeds normally (I'm installing from a USB2 device I created using LiLi Boot, with a copy of Ubuntu 12.10 64bit that I downloaded directly from the source. The system I'm running Ubuntu on has had a more traditional installation of ubuntu running on it without issue (also 12.10), so I know that everything works A-OK when booting from a 7200RPM internal disk. There are a number of oddities that I've noticed so far, including graphics corruption, but the first and most pressing issue is that Grub2 refuses to recognize the correct hd. From /boot/grub/grub.cfg: if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_msdos insmod ext2 set root='hd1,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd1,msdos1 --hint-efi=hd1,msdos1 --hint-baremetal=ahci1,msdos1 b58ee4f7-d41d-400a-b7b8-18bd1f0ae9d3 else search --no-floppy --fs-uuid --set=root b58ee4f7-d41d-400a-b7b8-18bd1f0ae9d3 fi font="/usr/share/grub/unicode.pf2" fi This is from a 100% fresh install of linux (first boot), which was installed while no hard drives were connected to the system, other than the USB2 LiLi drive. The system refuses to boot unless I change the hd1,msdos1 - hd0,msdos1 in the grub menu at boot, when it is the only disk device connected to the PC. What options are left for me to troubleshoot this issue? I've been racking my brains and taxing the internet trying to dig up something on this problem, but now I'd like to see if the Ubuntu community can rise to the challenge and help me fix this boot problem. This is the second time I've attempted this particular setup. The first time, after days of wasted time, I managed to get it to boot every other boot - i.e. every even boot it would boot into Ubuntu like it was happy; every odd boot it would boot into the BusyBox or Grub prompt. At one point it complained that it couldn't find /dev/disk/by-uuid/[the disk], which I found most perplexing, since the disk was there and booted before and after the occurrence (with intervention).

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  • The Real Value Of Certification

    - by Brandye Barrington
    I read a quote recently by Rich Hein of CIO.com "Certifications are, like most things in life: The more you put into them, the more you will get out." This is what we tell candidates all the time. The real value in obtaining a certification is the time spent preparing for the exam. All the hours spent reading books, practicing in hands-on environments, asking questions and searching for answers is valuable. It's valuable preparation for the exam, but it's also valuable preparation for your future job role and for your career. If your goal is just to pass an exam, you've missed a very important part of the value of certification.We receive so many questions through different forms of social media on whether or not certification will help candidates get jobs or get better jobs. Surveys conducted by us and by independent entities all point to the job and salary benefits of certification. However, a key part of that equation is whether a candidate can actually perform successfully in a job role. If preparation time was used to practice and learn and master new skills rather than to memorize a brain dump, the candidate will probably perform successfully in their job role, and job opportunities and higher salary will likely follow. Candidates who do not show that initiative, will not likely reap the full benefits of certification.Keep this in mind as you approach your next certification exam. You are preparing for a career, not an exam. This may help you to be more appreciative of the long hours spent studying!

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  • How can I get a 2D texture to rotate like a compass in XNA?

    - by IronGiraffe
    I'm working on a small maze puzzle game and I'm trying to add a compass to make it somewhat easier for the player to find their way around the maze. The problem is: I'm using XNA's draw method to rotate the arrow and I don't really know how to get it to rotate properly. What I need it to do is point towards the exit from the player's position, but I'm not sure how I can do that. So does anyone know how I can do this? Is there a better way to do it?

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  • Chapter One - Concepts/Requirements (The Fundamentals)

    - by drsql
    So here we are, the starting chapter with the obligatory introductory material that I hope people will read, digest, memorize and really take to heart.  I also realize that that is pretty unlikely. In fact, the first two chapters are kind of like that. First I introduce concepts, and in the next chapter I show how to draw pretty pictures of those concepts. Then comes normalization and after that we really start doing some modeling. In this chapter I am going to cover the basic stuff that you...(read more)

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  • Webmatrix The Site has Stopped Fix

    - by Tarun Arora
    I just got started with AzureWebSites by creating a website by choosing the Wordpress template. Next I tried to install WebMatrix so that I could run the website locally. Every time I tried to run my website from WebMatrix I hit the message “The following site has stopped ‘xxx’” Step 00 – Analysis It took a bit of time to figure out that WebMatrix makes use of IISExpress. But it was easy to figure out that IISExpress was not showing up in the system tray when I started WebMatrix. This was a good indication that IISExpress is having some trouble starting up. So, I opened CMD prompt and tried to run IISExpress.exe this resulted in the below error message So, I ran IISExpress.exe /trace:Error this gave more detailed reason for failure Step 1 – Fixing “The following site has stopped ‘xxx’” Further analysis revealed that the IIS Express config file had been corrupted. So, I navigated to C:\Users\<UserName>\Documents\IISExpress\config and deleted the files applicationhost.config, aspnet.config and redirection.config (please take a backup of these files before deleting them). Come back to CMD and run IISExpress /trace:Error IIS Express successfully started and parked itself in the system tray icon. I opened up WebMatrix and clicked Run, this time the default site successfully loaded up in the browser without any failures. Step 2 – Download WordPress Azure WebSite using WebMatrix Because the config files ‘applicationhost.config’, ‘aspnet.config’ and ‘redirection.config’ were deleted I lost the settings of my Azure based WordPress site that I had downloaded to run from WebMatrix. This was simple to sort out… Open up WebMatrix and go to the Remote tab, click on Download Export the PublishSettings file from Azure Management Portal and upload it on the pop up you get when you had clicked Download in the previous step Now you should have your Azure WordPress website all set up & running from WebMatrix. Enjoy!

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  • Will my game engine be compatible with physics engines?

    - by Bane
    My engine supports Scene handling, Cameras, and has a Renderer. Also, it has a class called Drawable, which has the position, the shape and the picture of an object. The picture property has width, height, rotation and a draw method. All game objects are supposed to inherit from this Drawable class, and are added to the Scene, along with a Map (collection of Tiles, that also inherit from Drawable), lights, and so on and so forth. The shape property of a Drawable is a Polygon, a collection of user defined vertices around the position of a Drawable (this is a relative coordinate system, so [0, 0] is the position of the Drawable. With this setup, will the users of my engine (probably only me) still be able to intergrate physics engines such as Box2DJS into their games?

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  • Packaging MATLAB (or, more generally, a large binary, proprietary piece of software)

    - by nfirvine
    I'm trying to package MATLAB for internal distribution, but this could apply to any piece of software with the same architecture. In fact, I'm packaging multiple releases of MATLAB to be installed concurrently. Key things Very large installation size (~4 GB) Composed of a core, and several plugins (toolboxes) Initially, I created a single "source" package (matlab2011b) that builds several .debs (mainly matlab2011b-core and matlab2011b-toolbox-* for each toolbox). The control file is just the standard all: dh $@ There is no Makefile; only copying files. I use a number of debian/*.install files to specify files to copy from a copy of an installation to /usr/lib/. The problem is, every time I build the thing (say, to make a correction to the core package), it recopies every file listed in the *.install file to e.g debian/$packagename/usr/ (the build phase), and then has to bundle that into a .deb file. It takes a long time, on the order of hours, and is doing a lot of extra work. So my questions are: Can you make dh_install do a hardlink copy (like cp -l) to save time? (AFAICT from the man page, no.) Maybe I should just get it to do this in the Makefile? (That's gonna b e big Makefile.) Can you make debuild only rebuild .debs that need rebuilding? Or specify which .debs to rebuild? Is my approach completely stupid? Should I break each of the toolboxes into its own source package too? (I'll have to do some silly templating or something, because there's hundreds of them. :/)

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  • Silverlight, JavaScript and HTML 5 - Who wins?

    - by Sahil Malik
    SharePoint 2010 Training: more information   Disclaimer: These are just opinions. In the past I have expressed opinions about the future of technology, and have been ridiculously accurate. I have no idea if this will be accurate or not, but that is what it’s all about. Its opinions, predicting the future.   This topic has been boiling inside me for a while, and I have discussed it in private gettogethers with fellow minded techies. But I thought it would be a good idea to put this together as a blogpost. There is some debate about the future of Silverlight, especially in light of technologies such as newer faster browsers, and HTML 5. As a .NET developer, where do I invest my time and skills – remember you have limited time and skills, and not everything that comes out of Microsoft is a smashing success. So it is very very wise for you to consider the facts, macro trends, and allocate what you have limited amounts of – “time”. Read full article ....

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  • GLES2.0 3D Android game performance and multi threading the update?

    - by Ofer
    I have profiled my mixed Java\C++ Android game and I got the following result: https://dl.dropbox.com/u/8025882/PompiDev/AndroidProfile.png As you can see, the pink think is a C++ functions that updates the game. It does things like updating the logic but it mostly it generates a "request list" for rendering. The thing is, I generate DrawLists on C++ and then send them to Java to process and draw using GLES2.0. Since then I was able to improve update from 9ms down to about 7ms, but I would like to ask if I would benefit from multi threading the update? As I understand from that diagram is that the function that takes the most time is the one you see it's color on the timeline. So the pink area is taken mostly by update. The other area has MainOpenGL.Handle as it's main contributor(whch is my java function), but since it's not drawn to the top of the diagram I can conclude other things are happening at the same time that use the CPU? Or even GPU stuff that isn't shown in this diagram. I am not sure how the GPU works on this. Does it calculate stuff in parallel to the CPU? Or is it part of the CPU usage as in SoC? I am not sure. Anyway, in case GPU things DO happen in parallel to CPU, then I would guess that if I do this C++ Update in parallel to the thread that makes the OpenGL calls, I might make use of "dead CPU time" due to GPU stalling or maybe have the GPU calls getting processed earlier because it won't have to wait for Update to finish? How do you suggest to improve performance based on that? Thanks.

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  • Cannot establish ssh connection to computer on local network

    - by ovangle
    I've just (re)installed ubuntu 11.10 on my main pc, and the connection times out every time I try to ssh connect to my laptop (over the local network) to retrieve the files I backed up there. The connection times out every time I try to connect. I can establish a connection in the other direction without issue. Here's the verbose output I get when I try to connect: ovangle@ruby-EP43-DS3:~$ ssh -v [email protected] OpenSSH_5.8p1 Debian-7ubuntu1, OpenSSL 1.0.0e 6 Sep 2011 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to 10.1.1.4 [10.1.1.4] port 22. debug1: connect to address 10.1.1.4 port 22: Connection timed out ssh: connect to host 10.1.1.4 port 22: Connection timed out ssh is installed on both machines, and I've tried deleting '~/.ssh/known_hosts' on both machines, still nada. I've changed the sshd logging on the laptop to VERBOSE and restarted the daemon (because I wasn't getting any relevant syslog entries otherwise), and this is the log for the most recent connection attempt. EDIT: posted wrong logs last time. They just showed that there was a connection received, they weren't actually the sshd logs (which were in auth.log as I recently discovered). Unfortunately, that log is filling up with extremely weird error messages and it gives me no information about the connection. Nov 8 16:02:18 ovangle-A6Rp pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000) Nov 8 16:02:18 ovangle-A6Rp pkexec: pam_ck_connector(polkit-1:session): cannot determine display-device Nov 8 16:02:18 ovangle-A6Rp pkexec[6270]: ovangle: Executing command [USER=root] [TTY=unknown] [CWD=/home/ovangle] [COMMAND=/usr/sbin/gnome-power-backlight-helper --set-brightness 2] Nov 8 16:02:19 ovangle-A6Rp pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000) Nov 8 16:02:19 ovangle-A6Rp pkexec: pam_ck_connector(polkit-1:session): cannot determine display-device Nov 8 16:02:19 ovangle-A6Rp pkexec[6273]: ovangle: Executing command [USER=root] [TTY=unknown] [CWD=/home/ovangle] [COMMAND=/usr/sbin/gnome-power-backlight-helper --set-brightness 7]

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  • JSR Updates and EC Meeting Tuesday @ 15:00 PST

    - by Heather VanCura
    JSR 310, Date and Time API, has moved to JCP 2.9 (first JCP 2.9 JSR!) JSR 236, Concurrency Utilities for Java EE, has published an Early Draft Review. This review ends 15 December 2012.  Tomorrow, Tuesday 20 November is the last Public EC Meeting of 2012, and the first EC meeting with the merged EC. The second hour of this meeting will be open to the public at 3:00 PM PST. The agenda includes  JSR 355,  EC merge implementation report, JSR 358 (JCP.next.3) status report, JCP 2.8 status update and community audit program.  Details are below. We hope you will join us, but if you cannot attend, not to worry--the recording and materials will also be public on the JCP.org multimedia page. Meeting details Date & Time Tuesday November 20, 2012, 3:00 - 4:00 pm PST Location Teleconference Dial-in +1 (866) 682-4770 (US) Conference code: 627-9803 Security code: 52732 ("JCPEC" on your phone handset) For global access numbers see http://www.intercall.com/oracle/access_numbers.htm Or +1 (408) 774-4073 WebEx Browse for the meeting from https://jcp.webex.com No registration required (enter your name and email address) Password: JCPEC Agenda JSR 355 (the EC merge) implementation report JSR 358 (JCP.next.3) status report 2.8 status update and community audit program Discussion/Q&A Note The call will be recorded and the recording published on jcp.org, so those who are unable to join in real-time will still be able to participate.

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  • Diving into a computer science career [closed]

    - by Willis
    Well first I would like to say thank you for taking the time to read my question. I'll give you some background. I graduated two years ago from a local UC in my state with a degree in cognitive psychology and worked in a neuroscience lab. During this time I was exposed to some light Matlab programming and other programming tidbits, but before this I had some basic understanding of programming. My father worked IT for a company when I was younger so I picked up his books and took learned things along the way growing up. Naturally I'm an inquisitive person, constantly learning, love challenges, and have had exposure to some languages. Yet at this point I was fully pursue it as a career and always had this in the back of my head. Where do I start? I'm 25 and feel like I still have time to make a switch. I've immersed myself in the terminal/command prompt to start, but which language do I focus on? I've read the A+ book and planning to take on the exam, then the networking exam, but I want to deal with more programming, development, and troubleshooting. I understand to get involved in open source, but where? I took the next step and got a small IT assistant job, but doesn't really deal with programming, development, just troubling shooting and small network issues. Thank you!

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  • jquery - targetting a select using $this

    - by Maureen
    I am trying to get individual selects (which have the same class as other selects) to respond to a .change function, however it only works on one of the selects. If you test out this code it will make more sense. Try to add a few "ON/OFF events", and then select "Specified Time" in the various selects. You'll see only the first one responds. Any ideas? Thanks! Please see the following code: $(document).ready(function() { var neweventstring = '<div class="event">Turns <select name="ONOFF"><option value="On">ON</option><option value="Off">OFF</option></select> at: <select name="setto" class="setto"><option>Select Time</option><option value="Sunrise">Sunrise</option><option value="Sunset">Sunset</option><option value="specifiedtime">Specified Time</option></select></div>'; $('#addmondaysevent').click(function () { $('#monday .events').append(neweventstring); }); $('.setto').change(function() { alert('The function is called'); if($("option:selected", this).val() =="specifiedtime"){ alert('If returns true'); $(this).css("background-color", "#cc0000"); $(this).after('<div class="specifictime"><input type="text" value="00" style="width:30px"/> : <input type="text" value="00" style="width:30px"> <select name="ampm"><option value="AM" selected>AM</option><option value="PM">PM</option></select></div>') } }); }); And my HTML: <div id="monday"> <h2>Mondays</h2> <div class="events"> <div class="event"> Turn <select name="ONOFF"> <option value="On">ON</option> <option value="Off">OFF</option> </select> at: <select name="setto" class="setto"> <option>Select Time</option> <option value="Sunrise">Sunrise</option> <option value="Sunset">Sunset</option> <option value="specifiedtime">Specified Time</option> </select> </div> [<a id="addmondaysevent">Add an ON/OFF event</a>] </div> </div>

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  • Unable to start Ubuntu 12.04. The system is running in low-graphics

    - by kaleidoscpicsoul
    I am a newbie to Ubuntu. I installed Ubuntu 12.04 using a USB Stick and it was running all fine for a few weeks and this error popped up. According to one of my friend, the best way was to re-install Ubuntu. Being from a non unix background i thought the same too and after the second install it happened again, but only this time was much quicker, in 3 days. I don't want to re-install Ubuntu every time this happens. I am a complete newbie to Linux which means that i am really bad at using terminal. I know there are other people who fixed this issue using this very same forum, but unfortunately the answers provided are too complex for me to understand. Please let me know how to do this. Things I want to let you know: I would need help step by step if that is alright with you. After i get the error i get the options and i click exit to console login I get the following message in a black screen (which i think is a command line sort of thing): * Stopping save kernel messages [OK] apache2: Could not reliably determine the server's fully qualified domain name,using 127.0.1.1 for ServerName [OK] * Starting web server apache2 and a blinking cursor. So basically it looks like a dead end for my non unixy eye. And one final thing is before this issue had happened i had tried configuring Python to Apache2. For that i had uninstalled and installed LAMP server several time and edited the configuration files too. I don't know if this really is a concern, but I don't know.. I have a USB with Ubuntu 12.04 in it so i can install it anytime. (But i want to know what the issue is rather than running away) . I migrated to Ubuntu from Windows and i have no plans to go back. I think that's from my side. Please let me know if there are any questions.

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  • Repelling a rigidbody in the direction an object is rotating

    - by ndg
    Working in Unity, I have a game object which I rotate each frame, like so: void Update() { transform.Rotate(new Vector3(0, 1, 0) * speed * Time.deltaTime); } However, I'm running into problems when it comes to applying a force to rigidbodies that collide with this game objects sphere collider. The effect I'm hoping to achieve is that objects which touch the collider are thrown in roughly the same direction as the object is rotating. To do this, I've tried the following: Vector3 force = ((transform.localRotation * Vector3.forward) * 2000) * Time.deltaTime; collision.gameObject.rigidbody.AddForce(force, ForceMode.Impulse); Unfortunately this doesn't always match the rotation of the object. To debug the issue, I wrote a simple OnDrawGizmos script, which (strangely) appears to draw the line correctly oriented to the rotation. void OnDrawGizmos() { Vector3 pos = transform.position + ((transform.localRotation * Vector3.forward) * 2); Debug.DrawLine(transform.position, pos, Color.red); } You can see the result of the OnDrawGizmos function below: What am I doing wrong?

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  • Should I avoid or embrace asking questions of other developers on the job?

    - by T.K.
    As a CS undergraduate, the people around me are either learning or are paid to teach me, but as a software developer, the people around me have tasks of their own. They aren't paid to teach me, and conversely, I am paid to contribute. When I first started working as a software developer co-op, I was introduced to a huge code base written in a language I had never used before. I had plenty of questions, but didn't want to bother my co-workers with all of them - it wasted their time and hurt my pride. Instead, I spent a lot of time bouncing between IDE and browser, trying to make sense of what had already been written and differentiate between expected behavior and symptoms of bugs. I'd ask my co-workers when I felt that the root of my lack of understanding was an in-house concept that I wouldn't find on the internet, but aside from that, I tried to confine my questions to lunch hours. Naturally, there were occasions where I wasted time trying to understand something in code on the internet that had, at its heart, an in-house concept, but overall, I felt I was productive enough during my first semester, contributing about as much as one could expect and gaining a pretty decent understanding of large parts of the product. I was wondering what senior developers felt about that mindset. Should new developers ask more questions to get to speed faster, or should they do their own research for themselves? I see benefits to both mindsets, and anticipate a large variety of responses, but I figure new developers might appreciate your answers without thinking to ask this question.

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  • Build vs Buy Webcast: November 8, 2012

    - by TammyBednar
    Date: Thursday, November 8, 2012, 1:00 PM EST You have a choice. Do you build your own database platform or buy a pre-engineered database appliance? Building a high-availability database platform presents unique challenges. Combining servers, storage, networking, OS, firmware, and database is complicated and raises important concerns: Will coordination between multiple SME’s delay deployment? Will it be reliable? Will it scale? Will routine maintenance consume precious IT-staff time? Ultimately, will it work? Enter the Oracle Database Appliance, a complete package of software, server, storage, and networking that’s engineered for simplicity. It saves time and money by simplifying deployment, maintenance, and support of database workloads. Plus, it’s based on Intel Xeon processors to ensure a high level of performance and scalability. Attend this Webcast to hear customer stories and discover how the Oracle Database Appliance: Increases ROI by reducing capital and operational expenses Frees IT staff by reducing deployment and management time from weeks to hours Takes the worry out of supporting mission critical application workloads Register For this WebCast today!

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  • How do I implement powerups for my Breakout clone?

    - by Eva
    I'm making a simple Breakout clone in Python that will have very many powerups/powerdowns (so far I came up with 26). Some will affect the paddle (paddle missile, two paddles, short paddle, etc.), some will affect the ball (slow ball, destructo-ball, invisible ball, etc.), some will affect the bricks (brick scramble, move up, bricks indestructible, etc.), and some will affect other game aspects (extra life, more points, less points, etc.). I'm pretty sure I have the code to draw the falling powerups and test for collisions with the paddle down, but I'm confused about how to code the effects of the powerups. Since there are very many powerups, it seemed inefficient to add specific methods to each component as done in this tutorial. However, I can't think of an other ways to implement the powerups. I found a page that hints at some way to design powerup behavior using classes, but I'm at a loss for how to do that. (A short example would help.) Please give me a short code example of another way to implement the effects of the powerups.

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  • How to cache queries in EJB and return result efficient (performance POV)

    - by Maxym
    I use JBoss EJB 3.0 implementation (JBoss 4.2.3 server) At the beginning I created native query all the time using construction like Query query = entityManager.createNativeQuery("select * from _table_"); Of couse it is not that efficient, I performed some tests and found out that it really takes a lot of time... Then I found a better way to deal with it, to use annotation to define native queries: @NamedNativeQuery( name = "fetchData", value = "select * from _table_", resultClass=Entity.class ) and then just use it Query query = entityManager.createNamedQuery("fetchData"); the performance of code line above is two times better than where I started from, but still not that good as I expected... then I found that I can switch to Hibernate annotation for NamedNativeQuery (anyway, JBoss's implementation of EJB is based on Hibernate), and add one more thing: @NamedNativeQuery( name = "fetchData2", value = "select * from _table_", resultClass=Entity.class, readOnly=true) readOnly - marks whether the results are fetched in read-only mode or not. It sounds good, because at least in this case of mine I don't need to update data, I wanna just fetch it for report. When I started server to measure performance I noticed that query without readOnly=true (by default it is false) returns result with each iteration better and better, and at the same time another one (fetchData2) works like "stable" and with time difference between them is shorter and shorter, and after 5 iterations speed of both was almost the same... The questions are: 1) is there any other way to speed query using up? Seems that named queries should be prepared once, but I can't say it... In fact if to create query once and then just use it it would be better from performance point of view, but it is problematic to cache this object, because after creating query I can set parameters (when I use ":variable" in query), and it changes query object (isn't it?). well, is here any way to cache them? Or named query is the best option I can use? 2) any other approaches how to make results retrieveng faster. I mean, for instance I don't need those Entities to be attached, I won't update them, all I need is just fetch collection of data. Maybe readOnly is the only available way, so I can't speed it up, but who knows :) P.S. I don't ask about DB performance, all I need now is how not to create query all the time, so use it efficient, and to "allow" EJB to do less job with the same result concerning data returning.

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  • MySQL - Calculating fields on the fly vs storing calculated data

    - by Christian Varga
    Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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  • XNA content.load Dependancy

    - by Richard
    Quick question, My project i'm building for test purposes is working fine but i have dependencies flying around everywhere due to the XNA framework. In Update i have gametime passed everywhere... this is okay. In Draw i have gametime & spritebatch passed everywhere... this is okay. My issue is in the content.load textures/sounds/fonts. I have them as public variables ie Texture1 = Content.load(of texture2d)("Texture1") I'm passing a 'Game1' pointer into the constructor of every new class being instantiated to gain access to these variables. Am i missing an OOP trick to prevent me having to pass a pointer to 'game1' to every New class?

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  • Should I be looking for developers with specific skill sets or generalists that need to learn?

    - by Lostsoul
    Thanks to the great help of this site and SO, I've been able to make a prototype of a software I want to sell but unfortunately although the prototype works I think my code quality is very low. I didn't use much OOP or design patterns so although my code is understandable to me, I think a normal developer would faint if they had to read it. So I wanted to hire a developer to make it a bit more better quality and improve some of my implementations of API's that I may have not done correctly. I'm having problems hiring a developer though. I have met 2 developers and had them read my software specs.The problem is, they lacked my business's domain knowledge(which is completely understandable and no biggie) but they also lacked knowledge of the underlying tech systems I used such as Hadoop, Hbase, Cuda, etc..I spent alot of time explaining map/reduce, bigtables and other technologies I used. I thought it was common knowledge because of my interactions with people on this site but the people I met with mentioned they never had to deal with these things so they didn't know it. My question is, for software projects that are hiring contractor developers is it a danger if the developer does not have experience with the underlying technologies? or can a general developer who is accomplished in another area realistically pick up new technologies? I did a very very quick back of envelope calculation and I think the upfront costs would be similar if I hire a student or developer with no experience in my technologies who will work many hours versus hiring a highly experienced developer who charges double but finishes in half the time but what other risks should I be considering or worried about? Also, should if I do hire a generalist, should I be paying for the time it takes them to learn hadoop or cuda if they are contractors(seems to make business sense but not sure how fair it is to them if they do not use the skill again). I'm a bit confused so any suggestions would be great.

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  • How can I support scrolling when using batched rendering for my tiles?

    - by dardanel
    I have tiled map 100*75 and tiles are 32*32 pixel.I want to use batching for performance .I don't figure it out , because of my game needs scrolling and every frame i draw 22*16 tiles (my screen is 20*16 tile) .I thought that batching tiles for every frame .Is it good or any suggestion? edit :to more clarify I want to use occlusion culling and batching at the same time.I thought that drawing only visible areas and batching them together .But there is a something i couldn't figure out .When scrolling screen with translate matrix , if one row become invisible , I bind new row and batch them again.Every batched objects needs to buffer again.So I batch tiles and buffer to VBO every time when one row become invisible .I don't know these way is efficient or not .This is my question .And i am open to any suggestions.

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  • Rotation, further I go from 0:0, the further the object positions around the origin while rotating

    - by Serguei Fedorov
    For some reason I am having the issue where the following code: global.spriteBatch.Draw(obj.sprite, obj.getPosition(), null, Color.White, obj.rotation, obj.center, 2f, SpriteEffects.None, 1); causes the object to rotate around the origin in such a way, as though there is an offset to the position relative to its location. The calculation for the center it correct and this happens even if I set the pivot to be the location of the object. The further I get from 0:0 the larger the radius or rotation. I am not sure what is going on here because given the following tutorial http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2D/Rotation.php I have done the code setup correctly. Any ideas? Any help is greatly appreciated!!!

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