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  • How can I design multi-threaded application for larger user base

    - by rokonoid
    Here's my scenario, I need to develop a scalable application. My user base may be over 100K, every user has 10 or more small tasks. Tasks check every minute with a third party application through web services, retrieving data which is written in the database, then the data is forwarded to it's original destination. So here's the processing of a small task: while(true){ Boolean isNewInformationAvailable = checkWhetherInformationIsAvailableOrNot(); If(isNewInformationAvailable ==true){ fetchTheData(); writeToDatabase(); findTheDestination(); deliverTheData(); isAvailable =false; } } As the application is large, how should I approach designing this? I'm going to use Java to write it. Should I use concurrency, and how would you manage the concurrency?

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  • Do ALL your variables need to be declared private?

    - by shovonr
    I know that it's best practice to stay safe, and that we should always prevent others from directly accessing a class' properties. I hear this all the time from university professors, and I also see this all the time in a lot of source code released on the App Hub. In fact, professors say that they will actually take marks off for every variable that gets declared public. Now, this leaves me always declaring variables as private. No matter what. Even if each of these variables were to have both a getter and a setter. But here's the problem: it's tedious work. I tend to quickly loose interest in a project every time I need to have a variable in a class that could have simply been declared public instead of private with a getter and a setter. So my question is, do I really need to declare all my variables private? Or could I declare some variables public whenever they require both a getter and a setter?

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  • What's the best way to cache a growing database table for html generation?

    - by McLeopold
    I've got a database table which will grow in size by about 5000 rows a hour. For a key that I would be querying by, the query will grow in size by about 1 row every hour. I would like a web page to show the latest rows for a key, 50 at a time (this is configurable). I would like to try and implement memcache to keep database activity low for reads. If I run a query and create a cache result for each page of 50 results, that would work until a new entry is added. At that time, the page of latest results gets new result and the oldest results drops off. This cascades down the list of cached pages causing me to update every cache result. It seems like a poor design. I could build the cache pages backwards, then for each page requested I should get the latest 2 pages and truncate to the proper length of 50. I'm not sure if this is good or bad? Ideally, the mechanism I use to insert a new row would also know how to invalidate the proper cache results. Has someone already solved this problem in a widely acceptable way? What's the best method of doing this? EDIT: If my understanding of the MYSQL query cache is correct, it has table level granularity in invalidation. Given the fact that I have about 5000 updates before a query on a key should need to be invalidated, it seems that the database query cache would not be used. MS SQL caches execution plans and frequently accessed data pages, so it may do better in this scenario. My query is not against a single table with TOP N. One version has joins to several tables and another has sub-selects. Also, since I want to cache the html generated table, I'm wondering if a cache at the web server level would be appropriate? Is there really no benefit to any type of caching? Is the best advice really to just allow a website site query to go through all the layers and hit the database every request?

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  • World orientation in OpenGLES clarification

    - by Dev2rights
    I have a 3d tile map made up of individual billboards in OpenGLES. Each is a 2 triangles mesh and has a 3D Vector to determine its position and another defining its rotation from the origin at (0,0,0). Im trying to work out how to rotate the entire tile map around a point be that the origin or some arbitrary point in space. Im guessing i need to set up a Model Matrix instead for each tile. Then set up a world matrix for the world. Then on updating i would translate the world matrix and change the orientation and multiply it with each model matrix before rendering. Is this correct ?

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  • Multiple network installs with cached downloads

    - by popey
    I tend to do lots of Ubuntu installs, and I'd like them to be up to date from the moment I do them, and not have to install a bazillion updates as soon as the install finishes. I'd also like to cache those packages somewhere on a machine on my LAN, so I don't re-download all the packages every time. How easy is this to achieve? Is there a guide somewhere to making this happen? Bonus points if I don't have to burn any CDs or use USB sticks! Edit: I have noticed a lot of guides for PXE booting and would be tempted to set this up but every time I find one they seem to be old/outdated and broken. My home server runs 10.04 LTS.

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  • Failed Vista/Ubuntu 12.04 attempt at dual boot. Can only boot Ubuntu now

    - by mathematician1975
    I recently tried installing Ubuntu 12.04 alongside my Windows Vista install. I can boot fine into Ubuntu every time, but now every time I choose to boot into Windows, the process fails completely and restarts (or shuts down) my laptop. Is there anything I can do to recover this. I am very happy with Ubuntu and I do not want to recover my old Vista installation to overwrite it, but I do need to be able to use both OS's. Is it recoverable or should I start from scratch?

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  • Webpage Content [closed]

    - by Akyl
    I am a web developer and I having problems with the lack of content required to make the website readable to people. Now my solution is to corner him and take his time off his work and answer some in debt questions from a list. The list would described as the content to be read by people(content being eg. point of website what is needed to be placed in). My questions: What is required to be on the list of contents required for general public to see? What are the most important aspects in point of web content required for users to see?

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  • Notes from AT&T ARO Session at Oredev 2013

    - by Geertjan
    The mobile internet is 12 times bigger than internet was 12 years ago. Explosive growth, faster networks, and more powerful devices. 85% of users prefer mobile apps, while 56% have problems. Almost 60% want less than 2 second mobile app startup. App with poor mobile experience results in not buying stuff, going to competitor, not liking your company. Battery life. Bad mobile app is worse than no app at all because it turns people away from brand, etc. Apps didn't exist 10 years ago, 72 billion dollars a year in 2013, 151 billion in 2017.Testing performance. Mobile is different than regular app. Need to fix issues before customers discover them. ARO is free and open source AT&T tool for identifying mobile app performance problems. Mobile data is different -- radio resource control state machine. Radio resource control -- radio from idle to continuous reception -- drains battery, sends data, packets coming through, after packets come through radio is still on which is tail time, after 10 seconds of no data coming through radio goes off. For example, YouTube, e.g., 10 to 15 seconds after every connection, can be huge drain on battery, app traffic triggers RRC state. Goal. Balance fast network connectivity against battery usage. ARO is free and open source and test any platform and won awards. How do I test my app? pcap or tcdump network. Native collector: Android and iOS. Android rooted device is needed. Test app on phone, background data, idle for ads and analytics. Graded against 25 best practices. See all the processes, all network traffic mapped to processes, stats about trace, can look just at your app, exlude Facebook, etc. Many tests conducted, e.g., file download, HTML (wrapped applications, e.g., cordova). Best Practices. Make stuff smaller. GZIP, smaller files, download faster, best for files larger than 800 bytes, minification -- remove tabs and commenting -- browser doesn't need that, just give processor what it needs remove wheat from chaff. Images -- make images smaller, 1024x1024 image for a checkmark, swish it, make it 33% smaller, ARO records the screen, probably could be 9 times smaller. Download less stuff. 17% of HTTP content on mobile is duplicate data because of caching, reloading from cache is 75% to 99% faster than downloading again, 75% possible savings which means app will start up faster because using cache -- everyone wants app starting up 2 seconds. Make fewer HTTP requests. Inline and combine CSS and JS when possible reduces the number of requests, spread images used often. Fewer connections. Faster and use less battery, for example, download an image every 60 secs, download an add every 60 seconds, send analytics every 60 seconds -- instead of that, use transaction manager, download everything at once, reduce amount of time connected to network by 40% also -- 80% of applications do NOT close connections when they are finished, e.g., download picture, 10 seconds later the radio turns off, if you do not explicitly close, eventually server closes, 38% more tail time, 40% less energy if you close connection right away, background data traffic is 27% of data and 55% of network time, this kills the battery. Look at redirection. Adds 200 to 600 ms on each connection, waterfall diagram to all the requests -- e.g., xyz.com redirect to www.xyz.com redirect to xyz.mobi to www.xyz.com, waterfall visualization of packets, minimize redirects but redirects are fine. HTML best practices. Order matters and hiding code (JS downloading blocks rendering, always do CSS before JS or JS asynchronously, CSS 'display:none' hides images from user but the browser downloads them which adds latency to application. Some apps turn on GPS for no reason. Tell network when down, but maybe some other app is using the radio at the same time. It's all about knowing best practices: everyone wins with ARO (carriers, e.g., AT&T, developers, customers). Faster apps, better battery usage, network traffic better, better app reviews, happier customers. MBTA app, referenced as an example.ARO is free, open source, can test all platforms.

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  • Happy Birthday LearnVisualStudio.NET?

    - by TATWORTH
    Back in 2003, I made the changeover to Dot Net with the help of LearnViusal Studio.NET. They provide an excellent learning resource. I commend membership to you. This week only, you can get started for as little as $48.97 for a 1 Year Subscription! Save 30% at LearnVisualStudio.NET http://www.learnvisualstudio.net?awt_l=BN5TZ&awt_m=JaSOlFqKSr1QwB You can also get a Lifetime membership for only $139.97! That's over $59 in savings! A lifetime membership will grant you access to every video on the site and every video we ever create for LearnVisualStudio.NET without giving us another dime! This is a great chance to access over 900 tutorials to help you learn C#, VB, ASP NET and more. Get started today! http://www.learnvisualstudio.net?awt_l=BN5TZ&awt_m=JaSOlFqKSr1QwB

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  • Triggering State Changes with Health Counter

    - by Hairgami_Master
    I'm developing a game where the player changes states as their health decreases. Below 50, it should trigger animation1. Below 30, it should trigger animation2. The problem is, I only want to trigger animation1 once. But my game timer is checking every "frame", so it's triggering animation1 every cycle below 50. I only want it to trigger once, then not again until it's gone over 50 and then naturally decreased back to below 50. Are there any tried and true strategies for triggering state changes as a timer counts down (without the over-triggering problem)? I thought I could say: if (health == 50) animation1.play(); but sometimes, health never equals exactly 50, so it will skip right past that statement.

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  • Calculate random points (pixel) within a circle (image)

    - by DMills
    I have an image that contains a circles at a specific location, and of a specific diameter. What I need to do is to be able to calculate random points within the circle, and then manipulate said the pixels they correlate to. I have the following code already: private Point CalculatePoint() { var angle = _random.NextDouble() * ( Math.PI * 2 ); var x = _originX + ( _radius * Math.Cos( angle ) ); var y = _originY + ( _radius * Math.Sin( angle ) ); return new Point( ( int )x, ( int )y ); } And that works fine for finding all the points at the circumference of the circle, but I need all points from anywhere in the circle. If this doesn't make sense let me know and I will do my best to clarify.

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  • Detect rotated rectangle collision

    - by handyface
    I'm trying to implement a script that detects whether two rotated rectangles collide for my game. I used the method explained in the following article for my implementation in Google Dart. 2D Rotated Rectangle Collision I tried to implement this code into my game. Basically from what I understood was that I have two rectangles, these two rectangles can produce four axis (two per rectangle) by subtracting adjacent corner coordinates. Then all the corners from both rectangles need to be projected onto each axis, then multiplying the coordinates of the projection by the axis coordinates (point.x*axis.x+point.y*axis.y) to make a scalar value and checking whether the range of both the rectangle's projections overlap. When all the axis have overlapping projections, there's a collision. First of all, I'm wondering whether my comprehension about this algorithm is correct. If so I'd like to get some pointers in where my implementation (written in Dart, which is very readable for people comfortable with C-syntax) goes wrong. Thanks!

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  • (Phaser) Preload Future States in Create?

    - by Brian
    I'm a first time user of Phaser, been trying to make a simple point and click type game. I'm trying to keep things very modular, so I'm defining a list of levels (states) in a JSON, and then every level has its own JSON containing the objects within that level. However, I'm encountering an issue in that, when changing states, I get a black flash while the assets for the next state load (this happens whether I iterate through the JSON list or define everything manually). From what I've read, all sprites should be loaded in the preload stage, however, by doing this I'm causing that tiny but noticeable black pause. I know one way would be to simply load every asset at the start of the game, but that seems incredibly inefficient (wouldn't that fill up the memory immensely?). I would rather load a state's assets from the "parent" state. However, in my quick test (which maybe I did wrong) it seems that game.load doesn't work properly if done within the create stage? What is the best approach to doing this?

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  • nVidia GT 220 not working properly with Ubuntu 12.10

    - by Glaedr
    I used to enable proprietary nVidia drivers on every previous Ubuntu release to get it working properly (elseway I was forced to a very low resolution and no graphic acceleration), and everything worked fine then. In particular, I noticed - still I don't know why - that the GPU fan on every OS gets noisy until the video drivers are loaded (runlevel 5, it seems, in Linux), and then slows down to a normal speed. Today I installed 12.10. Running the Live CD, surprisingly, everything was working fine: full resolution, acceleration, silent fan, and so on. The running driver was nvidia-current (GT 216). After installing and booting I found that the fan was overrunning. The installed driver is nouveau. I tried installing nvidia-current, or any other proprietary driver, even installing the kernel headers & source and then the drivers (as suggested here), but all I'm getting with proprietary drivers is, the irony, low resolution, noisy fan and no acceleration (thus obviously unity and compiz refusing to start). Does anybody know a way out?

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  • A c++ program that computes the min and max of f(x) for a rectangle inputed by user

    - by StreetBallerX
    So bassicly this is the problem quoted from my teacher : "You have to write a program in C++ that computes the minimal and the maximal value of function f(x,y) obtained on an integer point in a given rectangle [a, b] x [c, d]. Your program should prompt the user to input numerical values of a, b, c and d, as floating point numbers, which are expected to be in a range from -100 thru 100. In case when minimal or maximal values do not exists, your program should output appropriate messages. f(x,y)=x+x*x+x*x*x+y+y*y " So before anyone tell me that i should try do it myself , i'll tell them that ive been trying to do it myself for the past 8 days but my deadline is aproaching and i just cant figure it out its a really simple program but i just cant understand it ... I wont post my attempts because all i saw in these forums is that when someone posts their try and a milion people start to say dont look it this way thry this and bla bla and the guy who posted it was just wondering for minor thing ... so what ever thank you all in advance and thats it :)

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  • How to use HTTP Handler to make a client2client communication? [closed]

    - by meorfi
    I'm new to Web programming! I try to make an app (something like Client to Client communication with C# Handlers and jQuery). I.E.: When 1Client make a click on his clientSide(browser), there paints one point, and on the same time the 2Client sees what 1Client did. And, in turn, where 2Client make a click on his browser, there paints one point, and the 1Client also sees what 2Client did. I could done already the configuration of IIS, I made an simple show Hello World and it run OK. And, further, what should i done.... Can you advice me, please, with some exemples, or tutorials, how to do this job. Sorry for my questions which seems to be not studied.

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  • Testing complex compositions

    - by phlipsy
    I have a rather large collection of classes which check and mutate a given data structure. They can be composed via the composition pattern into arbitrarily complex tree-like structures. The final product contains a lot of these composed structures. My question is now: How can I test those? Albeit it is easy to test every single unit of these compositions, it is rather expensive to test the whole compositions in the following sense: Testing the correct layout of the composition-tree results in a huge number of test cases Changes in the compositions result in a very laborious review of every single test case What is the general guideline here?

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  • Driver inversion

    - by Val
    I have a GUI game, which is driven by user every time it clicks the mouse. Every time user clicks a square on a board, the board state is updated (we re-compute the score, the player to make next move and legal movements it can make) and repainted. Both mouse click, state recomputation and painting are handled in the GUI thread. Now, suppose that I want to train AI to play without GUI. That is, game engine should consume next move by simply calling AI's makeMove function in one thread. This would allow to play millions of games per second automatically. GUI may just screenshot some arbitrary states time after time. How do you switch to this strategy?

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  • Game Object Design

    - by oisin
    I'm having a problem with the way I designed my first simple game in C++. I have GameObject (abstract class) and ObjectA which inherits the update() and draw() methods from GameObject. My main loop contains a linked list of GameObject*, and while that list is not empty it cycles through it, calling update on each one. Up until this point, I thought the design was standard(?) and would work. However, when I call update on ObjectA() I run into two problems: ObjectA can die which messes up the list, which in turn throws off the loop in main. ObjectA can spawn more ObjectA's but these are local scope and the update() goes out of scope, creating problems in main's list of GameObjects. I think my design if alright, but I'm having such problems with segmentation faults that there must be something seriously wrong with at least one part of my implementation. If anyone could point out any serious mistakes or simple examples of this being done (or even alternative designs) then I would greatly appreciate it!

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