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• fdisk shows overlapping partitions

  - by Campa

  At every boot to start Ubuntu, a partition gets re-mounted more than 1 times, sometimes causing very long boots. Example below: > dmesg ... [ 21.472020] EXT4-fs (sda5): re-mounted. Opts: errors=remount-ro ... [ 42.021537] EXT4-fs (sda5): re-mounted. Opts: errors=remount-ro,commit=0 ... I suspect there is a problem of overlapping partitions here, regarding sda4 and sda5: > sudo fdisk -l Device Boot Start End Blocks Id System /dev/sda1 63 610469 305203+ de Dell Utility /dev/sda2 612352 32069631 15728640 7 HPFS/NTFS/exFAT /dev/sda3 * 32069632 238979788 103455078+ 7 HPFS/NTFS/exFAT /dev/sda4 238983166 625141759 193079297 5 Extended /dev/sda5 238983168 612630527 186823680 83 Linux /dev/sda6 612632576 625141759 6254592 82 Linux swap / Solaris Further details: > more /etc/fstab ... # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda6 during installation UUID=b33be99b-5c9e-449e-ad48-be608aeff001 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda7 during installation UUID=7c9071cc-b77b-40da-9f80-6b8a9a220cb1 none swap sw and > mount /dev/sda5 on / type ext4 (rw,errors=remount-ro,commit=0) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) fusectl on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) gvfs-fuse-daemon on /home/piero/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=piero) I am Running Ubuntu Oneiric + LXDE on Dell Studio XPS machine 64-bit, dual booting with Windows 7. A months ago, I resized the Ubuntu partition and maybe I messed up something by doing that. Do you have any idea, why this long booting is happening?

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• Box2D Difference Between WorldCenter and Position

  - by Free Lancer

  So this problem has been brothering for a couple of days now. First off, what is the difference between say Body.getWorldCenter() and Body.getPosition(). I heard that WorldCenter might have to do with the center of gravity or something. Second, When I create a Box2D Body for a sprite the Body is always at the lower left corner. I check it by printing a Rectangle of 1 pixel around the box.getWorldCenter(). From what I understand the Body should be in the center of the Sprite and its bounding box should wrap around the Sprite, correct? Here's an image of what I mean (The Sprite is Red, Body Blue): Here's some code: Body Creator: public static Body createBoxBody( final World pPhysicsWorld, final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pCenterX = pSprite.getX() + pSprite.getWidth() / 2; float pCenterY = pSprite.getY() + pSprite.getHeight() / 2; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; //boxBodyDef.position.x = pCenterX / Constants.PIXEL_METER_RATIO; //boxBodyDef.position.y = pCenterY / Constants.PIXEL_METER_RATIO; boxBodyDef.position.x = pSprite.getX() / Constants.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Constants.PIXEL_METER_RATIO; Vector2 v = new Vector2( boxBodyDef.position.x * Constants.PIXEL_METER_RATIO, boxBodyDef.position.y * Constants.PIXEL_METER_RATIO ); Gdx.app.log("@Physics", "createBoxBody():: Box Position: " + v); // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Constants.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Constants.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = pPhysicsWorld.createBody(boxBodyDef); Gdx.app.log("@Physics", "createBoxBody():: Box Center: " + boxBody.getPosition().mul(Constants.PIXEL_METER_RATIO)); boxBody.createFixture(pFixtureDef); boxBody.setTransform( boxBody.getWorldCenter(), MathUtils.degreesToRadians * pRotation ); boxPoly.dispose(); return boxBody; } Making the Sprite: public Car( Texture texture, float pX, float pY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( mSprite.getWidth() / 6, mSprite.getHeight() / 6 ); mSprite.setPosition( pX, pY ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); FixtureDef carFixtureDef = new FixtureDef(); // Set the Fixture's properties, like friction, using the car's shape carFixtureDef.restitution = 1f; carFixtureDef.friction = 1f; carFixtureDef.density = 1f; // needed to rotate body using applyTorque mBody = Physics.createBoxBody( world, BodyDef.BodyType.DynamicBody, carFixtureDef, mSprite ); }

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• Are they asking too much of me?

  - by Tesserex

  Or am I just whining? Background: I work for a "startup," which I put in air quotes because the company has been around for 4 years. We have about 40 employees in three offices, 9 here plus some part time. We have a good amount of investment and bring in about 75% of what we spend (so not profitable just yet.) Standard work week is supposed to be about 60 hours, but they justify that as we have to be online when our international (Taiwan and Vietnam) offices are awake. When I started the job 6 months ago, I spent about a month prototyping an iphone app and did really well on my own. They also found out about my facebook applications and how many users they got. Putting 2 and 2 together (and winding up at -7) they realized 1. I'm independent and innovative (because I was able to use stackoverflow to answer my iOS questions instead of bugging my superiors) and 2. I must have an eye for marketing (since my fb apps grew totally organically without me doing any advertising), and assigned me to a project optimizing adwords campaigns. Today I got reviewed, and then chewed out, by our CEO for not totally rocking this project. Now I thought I was doing ok, but the CEO said the project is stagnant and they're expecting more from me. But since it's a startup, they play loose with job roles and I've had plenty of other things to do in the past three months. Every time I ask what's most important, I get conflicting responses depending who I ask, and the end result is that almost everything has equal priority - high. I could go on about how I don't think adwords is worthwhile for us since our profit margin is so slim, and how we should be trying to improve our website first, but that's not the point. I also have explained to the office director (who originally assigned me the project, not the CEO) that I don't actually know anything about marketing, I'm just a decent programmer, but they think my general smarts will prove capable of tackling this challenge. The CEO also clarified that he wants a more technical and algorithmic approach to the problem. So is there something I can do to address this? Combined with my existing and confusing workload, should I be raising an issue? Or should I do the grown up thing and give it my all, asking for help when I need it and hoping for the best? Sorry if this is very rant-ish.

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• PASS Summit for SQL Starters

  - by Davide Mauri

  I’ve received a buch of emails from PASS Summit “First Timers” that are also somehow new to SQL Server (for “somehow” I mean people with less than 6 month experience but with some basic knowledge of SQL Server engine) or are catching up from SQL Server 2000. The common question regards the session one should not miss to have a broad view of the entire SQL Server platform have some insight into some specific areas of SQL Server Given that I’m on (semi-)vacantion and that I have more free time (not true, I have to prepare slides & demos for several conferences, PASS Summit  - Building the Agile Data Warehouse with SQL Server 2012 - and PASS 24H - Agile Data Warehousing with SQL Server 2012 - among them…but let’s pretend it to be true), I’ve decided to make a post to answer to this common questions. Of course this is my personal point of view and given the fact that the number and quality of session that will be delivered at PASS Summit is so high that is very difficoult to make a choice, fell free to jump into the discussion and leave your feedback or – even better – answer with another post. I’m sure it will be very helpful to all the SQL Server beginners out there. I’ve imposed to myself to choose 6 session at maximum for each Track. Why 6? Because it’s the maximum number of session you can follow in one day, and given that all the session will be on the Summit DVD, they are the answer to the following question: “If I have one day to spend in training, which session I should watch?”. Of course a Summit is not like a Course so a lot of very basics concept of well-established technologies won’t be found here. Analysis Services, Integration Services, MDX are not part of the Summit this time (at least for the basic part of them). Enough with that, let’s start with the session list ideal to have a good Overview of all the SQL Server Platform: Geospatial Data Types in SQL Server 2012 Inside Unstructured Data: SQL Server 2012 FileTable and Semantic Search XQuery and XML in SQL Server: Common Problems and Best Practice Solutions Microsoft's Big Play for Big Data Dashboards: When to Choose Which MSBI Tool Microsoft BI End-User Tools 360° for what concern Database Development, I recommend the following sessions Understanding Transaction Isolation Levels What to Look for in Execution Plans Improve Query Performance by Fixing Bad Parameter Sniffing A Window into Your Data: Using SQL Window Functions Practical Uses and Optimization of New T-SQL Features in SQL Server 2012 Taking MERGE Beyond the Basics For Business Intelligence Information Delivery Analyzing SSAS Data with Excel Building Compelling Power View Reports Managed Self-Service BI PowerPivot 101  SharePoint for Business Intelligence The Best Microsoft BI Tools You've Never Heard Of and for Business Intelligence Architecture & Development BI Power Hour Building a Tabular Model Database Enterprise Information Management: Bringing Together SSIS, DQS, and MDS SSIS Design Patterns Storing Columnstore Indexes Hadoop and Its Ecosystem Components in Action Beside the listed sessions, First Timers should also take a look the the page PASS set up for them: http://www.sqlpass.org/summit/2012/Connect/FirstTimers.aspx See you at PASS Summit!

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• New grad; To overcome complete lack of experience, should I ditch a creative pet project in lieu of one that would demonstrate more applicable skills?

  - by Hart Simha

  I am currently working on a project on github that I think would be a good demonstration of my initiative, creativity and enthusiasm. It is an educational game I am developing in pygame that enables the user to learn to improve their development productivity by using vim, specifically with python, though learning to code faster with vim should be transferable to any language. I think this is something that might have a mass appeal and benefit to a lot of people in a measurable way. -However- I am graduating from college in a month (my degree is computer science with a minor in English), with no experience that is relevant to helping me get any kind of job in the field, and a gpa that doesn't tout my merits. I could pursue a career in game development, but it's not necessarily what I'm most interested in, and see myself applying to startups around the country. To the places I am looking at applying, showing that I have experience with pygame is going to be largely irrelevant, except in demonstration of my ability to code, period. A lot of skills that ARE more marketable, such a data modeling, GIS, mobile application, development, javascript, .net framework, and various web development technologies, are not going to be showcased by this project (on the upside, employers do like to see familiarity with git and python). I'm wondering if I should sink all my free time in the next couple of months into this project, since I'm motivated and interested in it, and if the value of being able to demonstrate ambition and 'good ideas' (for lack of a better term, and in my own opinion) will compensate for the absence of demonstrating more sought-after skills. I am probably at a point where I should either commit fully to this project now, or put it on the backburner in favor of something else, and I am leaning towards continuing with what I am already working on, because I think it's a great idea, and something achievable to me with enough dedication over the next couple months. But the most important thing to me is being able to get a job out of college, which I am exceedingly concerned about as the professional landscape which I am navigating for the first time is a lot more intimidating than I could have anticipated, with almost every job (even short-term contract positions) requiring years of experience which I lack. So in brief, the common denominator to answering the question "How can I overcome experience requirements for a job" seems to be "Show off your own project." I want to know WHICH project I should work on to best increase my chances of getting a job out of college, keeping in mind that I have no experience. I believe this question is applicable to any new grad that lacks demonstrable experience.

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• Multi-Part Map Troubleshooting

  - by Michael Stephenson

  Scenario I came across a nice little one with multi-part maps the other day. I had an orchestration where I needed to combine 4 input messages into one output message like in the below table:   Input Messages Output Messages Company Details Member Details Event Message Member Search Member Import   I thought my orchestration was working fine but for some reason when I was trying to send my message it had no content under the root node like below <ns0:ImportMemberChange xmlns:ns0="http://---------------/"></ns0:ImportMemberChange>   My map is displayed in the below picture. I knew that the member search message may not have any elements under it but its root element would always exist. The rest of the messages were expected to be fully populated. I tried a number of different things and testing my map outside of the orchestration it always worked fine. The Eureka Moment The eureka moment came when I was looking at the xslt produced by the map. Even though I'd tried swapping the order of the messages in the input of the map you can see in the below picture that the first part of the processing of the message (with the red circle around it) is doing a for-each over the GetCompanyDetailsResult element within the GetCompanyDetailsResponse message. This is because the processing is driven by the output message format and the first element to output is the OrganisationID which comes from the GetCompanyDetailsResponse message. At this point I could focus my attention on this message as the xslt shows that if this xpath statement doesn’t return the an element from the GetCompanyDetailsResponse message then the whole body of the output message will not be produced and the output from the map would look like the message I was getting. <ns0:ImportMemberChange xmlns:ns0="http://---------------/"></ns0:ImportMemberChange> I was quickly able to prove this in my map test which proved this was a likely candidate for the problem. I revisited the orchestration focusing on the creation of the GetCompanyDetailsResponse message and there was actually a bug in the orchestration which resulted in the message being incorrectly created, once this was fixed everything worked as expected. Conclusion Originally I thought it was a problem with the map itself, and looking online there wasn’t really much in the way of content around troubleshooting for multi-part map problems so I thought I'd write this up. I guess technically it isn't a multi-part map problem, but I spend a good couple of hours the other day thinking it was.

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• Documenting sp_ssiscatalog

  - by jamiet

  What is the best way to document an API? Moreover, what is the best way to document a T-SQL API? Before I try to answer those questions I should explain what I mean by “a T-SQL API”. I think of an API as being a collection of well-defined, known, code modules that provide some notion of a service to whomever uses it; in T-SQL terms I tend to think of a collection of stored procedures and functions as a form of API. Its a loose definition, I admit, and in SQL Server circles we don’t tend to think of stored procedures collectively as an API but if you think about it that’s exactly what they are. The question of how to document a T-SQL API came to my mind as I worked on sp_ssiscatalog. How could I make it easy for people to learn about the capabilities of sp_ssiscatalog without forcing them to dig through the code and find out for themselves? My opening gambit was to write documentation pages on the wiki at http://ssisreportingpack.codeplex.com. That’s kinda useful but it does suffer the disadvantage that someone using sp_ssiscatalog needs to go visit a webpage to read it – I want the documentation to be available wherever the user is using sp_ssiscatalog. Moreover, maintaining the wiki is a real PITA. Intellisense works up to a point, I guess: but that only shows whatever SQL Server knows about the various parameters, which isn’t all that much! I wanted a better way for my API users to learn about its capabilities and so I hit upon the idea of simply using PRINT statements within the code itself to inform the user what options are available; hence I added such PRINT statements in the latest check-in. Now when you execute (for example): EXEC sp_ssiscatalog @operation_type='execs' you can hit F6 a few times to view the messages pane and you shall see something like this: Notice that I’m returning information about all the parameters that can be used to affect the results that just got returned. I really do think this will be very useful to anyone using sp_ssiscatalog; I myself am always forgetting what the parameters are and I wrote the damn thing so I can’t really expect anyone else to remember them. I have not yet made available a release that has these changes in it but when I do I’ll blog about it right here. At the time of writing the latest available release of sp_ssiscatalog is DB v1.0.1.0 but if you want to the latest and greatest simply download it straight from source. Feedback is welcome as always. @Jamiet

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• Innovation for Retailers

  - by David Dorf

  One of my main objectives for this blog is to point out emerging technologies and how they might apply to the retail industry.  But ideas are just the beginning; retailers either have to rely on vendors or have their own lab to explore these ideas and see which ones work.  (A healthy dose of both is probably the best solution.)  The Nordstrom Innovation Lab is a fine example of dedicating resources to cultivate ideas and test prototypes. The video below, from 2011, is a case study in which the team builds an iPad app that helps customers purchase sunglasses in the store.  Customers take pictures of themselves wearing different sunglasses, then can do side-by-side comparisons. There are a few interesting take-aways from their process.  First, they are working in the store alongside employees and customers.  There's no concept of documenting all the requirements then building the product.  Instead, they work closely with those that will be using the app in order to fully understand what's needed.  When they find an issue, they change the software onsite and try again.  This iterative prototyping ensures their product hits the mark.  Feels like Extreme Programming if you recall that movement. Second, they have time-boxed the project to one week.  Either it works or it doesn't, and either way they've only expended a week's worth of resources.  Innovation always entails failure, and those that succeed are often good at detecting failure quickly then adjusting.  Fail fast and fail often. Third, its not always about technology.  I was impressed they used paper designs to walk through user stories and help understand the needs of the customer.  Pen and paper is the innovator's most powerful tool. Our Retail Applied Research (RAR) team uses some of these concepts in our development process.  (Calling it a process is probably overkill.)  We try to give life to concepts quickly so the rest of organization can help us decide if we're heading the right direction.  It takes many failures before finding a successful product.

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• Our own Daily WTF

  - by Dennis Vroegop

  Originally posted on: http://geekswithblogs.net/dvroegop/archive/2014/08/20/our-own-daily-wtf.aspxIf you're a developer, you've probably heard of the website the DailyWTF. If you haven't, head on over to http://www.thedailywtf.com and read. And laugh. I'll wait. Read it? Good. If you're a bit like me probably you've been wondering how on earth some people ever get hired as a software engineer. Most of the stories there seem to weird to be true: no developer would write software like that right? And then you run into a little nugget of code one of your co-workers wrote. And then you realize: "Hey, it happens everywhere!" Look at this piece of art I found in our codebase recently: public static decimal ToDecimal(this string input) {     System.Globalization.CultureInfo cultureInfo = System.Globalization.CultureInfo.InstalledUICulture;     var numberFormatInfo = (System.Globalization.NumberFormatInfo)cultureInfo.NumberFormat.Clone();     int dotIndex = input.IndexOf(".");     int commaIndex = input.IndexOf(",");     if (dotIndex > commaIndex)         numberFormatInfo.NumberDecimalSeparator = ".";     else if (commaIndex > dotIndex)         numberFormatInfo.NumberDecimalSeparator = ",";     decimal result;     if (decimal.TryParse(input, System.Globalization.NumberStyles.Float, numberFormatInfo, out result))         return result;     else         throw new Exception(string.Format("Invalid input for decimal parsing: {0}. Decimal separator: {1}.", input, numberFormatInfo.NumberDecimalSeparator)); }  Me and a collegue have been looking long and hard at this and what we concluded was the following: Apparently, we don't trust our users to be able to correctly set the culture in Windows. Users aren't able to determine if they should tell Windows to use a decimal point or a comma to display numbers. So what we've done here is make sure that whatever the user enters, we'll translate that into whatever the user WANTS to enter instead of what he actually did. So if you set your locale to US, since you're a US citizen, but you want to enter the number 12.34 in the Dutch style (because, you know, the Dutch are way cooler with numbers) so you enter 12,34 we will understand this and respect your wishes! Of course, if you change your mind and in the next input field you decide to use the decimal dot again, that's fine with us as well. We will do the hard work. Now, I am all for smart software. Software that can handle all sorts of input the user can think of. But this feels a little uhm, I don't know.. wrong.. Or am I too old fashioned?

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• What does path finding in internet routing do and how is it different from A*?

  - by alan2here

  Note: If you don't understand this question then feel free to ask clarification in the comments instead of voting down, it might be that this question needs some more work at the moment. I've been directed here from the Stack Excange chat room Root Access because my question didn't fit on Super User. In many aspects path finding algorithms like A star are very similar to internet routing. For example: A node in an A* path finding system can search for a path though edges between other nodes. A router that's part of the internet can search for a route though cables between other routers. In the case of A*, open and closed lists are kept by the system as a whole, sepratly from any individual node as well as each node being able to temporarily store a state involving several numbers. Routers on the internet seem to have remarkable properties, as I understand it: They are very performant. New nodes can be added at any time that use a free address from a finite (not tree like) address space. It's real routing, like A*, there's never any doubling back for example. Similar IP addresses don't have to be geographically nearby. The network reacts quickly to changes to the networks shape, for example if a line is down. Routers share information and it takes time for new IP's to be registered everywhere, but presumably every router doesn't have to store a list of all the addresses each of it's directions leads most directly to. I'm looking for a basic, general, high level description of the algorithms workings from the point of view of an individual router. Does anyone have one? I presume public internet routers don't use A* as the overheads would be to large, and scale to poorly. I also presume there is a single method worldwide because it seems as if must involve a lot of transferring data to update and communicate a reasonable amount of state between neighboring routers. For example, perhaps the amount of data that needs to be stored in each router scales logarithmically with the number of routers that exist worldwide, the detail and reliability of the routing is reduced over increasing distances, there is increasing backtracking involved in parts of the network that are less geographically uniform or maybe each router really does perform an A* style search, temporarily maintaining open and closed lists when a packet arrives.

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• Problem trying to lock framerate at 60 FPS

  - by shad0w

  I've written a simple class to limit the framerate of my current project. But it does not work as it should. Here is the code: void FpsCounter::Process() { deltaTime = static_cast<double>(frameTimer.GetMsecs()); waitTime = 1000.0/fpsLimit - deltaTime; frameTimer.Reset(); if(waitTime <= 0) { std::cout << "error, waittime: " << waitTime << std::endl; } else { SDL_Delay(static_cast<Uint32>(waitTime)); } if(deltaTime == 0) { currFps = -1; } else { currFps = 1000/deltaTime; } std::cout << "--Timings--" << std::endl; std::cout << "Delta: \t" << deltaTime << std::endl; std::cout << "Delay: \t" << waitTime << std::endl; std::cout << "FPS: \t" << currFps << std::endl; std::cout << "-- --" << std::endl; } Timer::Timer() { startMsecs = 0; } Timer::~Timer() { // TODO Auto-generated destructor stub } void Timer::Start() { started = true; paused = false; Reset(); } void Timer::Pause() { if(started && !paused) { paused = true; pausedMsecs = SDL_GetTicks() - startMsecs; } } void Timer::Resume() { if(paused) { paused = false; startMsecs = SDL_GetTicks() - pausedMsecs; pausedMsecs = 0; } } int Timer::GetMsecs() { if(started) { if(paused) { return pausedMsecs; } else { return SDL_GetTicks() - startMsecs; } } return 0; } void Timer::Reset() { startMsecs = SDL_GetTicks(); } The "FpsCounter::Process()" Method is called everytime at the end of my gameloop. I've got the problem that the loop is correctly delayed only every second frame, so it runs one frame delayed at 60 FPS and the next without delay at over 1000 fps. I am searching the error quite a while now, but I do not find it. I hope somebody can point me in the right direction.

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• How do I randomly generate a top-down 2D level with separate sections and is infinite?

  - by Bagofsheep

  I've read many other questions/answers about random level generation but most of them deal with either randomly/proceduraly generating 2D levels viewed from the side or 3D levels. What I'm trying to achieve is sort of like you were looking straight down on a Minecraft map. There is no height, but the borders of each "biome" or "section" of the map are random and varied. I already have basic code that can generate a perfectly square level with the same tileset (randomly picking segments from the tileset image), but I've encountered a major issue for wanting the level to be infinite: Beyond a certain point, the tiles' positions become negative on one or both of the axis. The code I use to only draw tiles the player can see relies on taking the tiles position and converting it to the index number that represents it in the array. As you well know, arrays cannot have a negative index. Here is some of my code: This generates the square (or rectangle) of tiles: //Scale is in tiles public void Generate(int sX, int sY) { scaleX = sX; scaleY = sY; for (int y = 0; y <= scaleY; y++) { tiles.Add(new List<Tile>()); for (int x = 0; x <= scaleX; x++) { tiles[tiles.Count - 1].Add(tileset.randomTile(x * tileset.TileSize, y * tileset.TileSize)); } } } Before I changed the code after realizing an array index couldn't be negative my for loops looked something like this to center the map around (0, 0): for (int y = -scaleY / 2; y <= scaleY / 2; y++) for (int x = -scaleX / 2; x <= scaleX / 2; x++) Here is the code that draws the tiles: int startX = (int)Math.Floor((player.Position.X - (graphics.Viewport.Width) - tileset.TileSize) / tileset.TileSize); int endX = (int)Math.Ceiling((player.Position.X + (graphics.Viewport.Width) + tileset.TileSize) / tileset.TileSize); int startY = (int)Math.Floor((player.Position.Y - (graphics.Viewport.Height) - tileset.TileSize) / tileset.TileSize); int endY = (int)Math.Ceiling((player.Position.Y + (graphics.Viewport.Height) + tileset.TileSize) / tileset.TileSize); for (int y = startY; y < endY; y++) { for (int x = startX; x < endX; x++) { if (x >= 0 && y >= 0 && x <= scaleX && y <= scaleY) tiles[y][x].Draw(spriteBatch); } } So to summarize what I'm asking: First, how do I randomly generate a top-down 2D map with different sections (not chunks per se, but areas with different tile sets) and second, how do I get past this negative array index issue?

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• Unintentional run-in with C# thread concurrency

  - by geekrutherford

  For the first time today we began conducting load testing on a ASP.NET application already in production. Obviously you would normally want to load test prior to releasing to a production environment, but that isn't the point here.   We ran a test which simulated 5 users hitting the application doing the same actions simultaneously. The first few pages visited seemed fine and then things just hung for a while before the test failed. While the test was running I was viewing the performance counters on the server noting that the CPU was consistently pegged at 100% until the testing tool gave up.   Fortunately the application logs all exceptions including those unhandled to the database (thanks to log4net). I checked the log and low and behold the error was:   System.ArgumentException: An item with the same key has already been added. (The rest of the stack trace intentionally omitted)   Since the code was running with debug on the line number where the exception occured was also provided. I began inspecting the code and almost immediately it hit me, the section of code responsible for the exception is trying to initialize a static class. My next question was how is this code being hit multiple times when I have a rudimentary check already in place to prevent this kind of thing (i.e. a check on a public variable of the static class before entering the initializing routine). The answer...the check fails because the value is not set before other threads have already made it through.   Not being one who consistently works with threading I wasn't quite sure how to handle this problem. Fortunately a co-worker recalled having to lock a section of code in the past but couldn't recall exactly how. After a quick search on Google the solution is as follows:   Object objLock = new Object(); lock(objLock) { //logic requiring lock }   The lock statement takes an object and tells the .NET runtime that the current thread has exclusive access while the code within brackets is executing. Once the code completes, the lock is released for another thread to utilize.   In my case, I only need to execute the inner code once to initialize my static class. So within the brackets I have a check on a public variable to prevent it from being initialized again.

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• Is IE9 a modern browser?

  - by anirudha

  Is IE9 a modern browser? i show you a post who compare IE as well as they compare chrome. Is IE9 a modern browser? well Are you thing that they make something bettter then thing another that what Firefox and chrome do whenever Microsoft do this. that's point that Microsoft always blast IE because they make version upon version not upon update like Firefox make 3.6.14 after 3.6.13 and chrome give update soon as possible but IE not come soon. they will thing for making 10 instead of giving update on 9. well what they tell us new. they make fool public everytime i believe they make fool public as same as today they maked for version 9 they show developer tool in 9 have three new tabs or pael are this enough. whenever  in chrome and firefox their is many plugin who make development easier IE still have a developer tool who not have enough power like Firebug in Firefox. they show performance but forget luna user [window xp] and their IE never runs on other plateform but chrome and firefox can. no customization in IE whenever chrome and firefox have uncountable plugin and addons. show features now in IE who already implemented in firefox very early. well their is no rule that static goes right every time not sure that IE and Firefox both are right in their language. their is no one predict what thing goes better in future. so well keep a thing in mind never wasted time and also thing to make task easier even you need to use sollution opensource or closesoure inside or outside MS does not matter. well everyone tell you much more then they do even IE and some other. they never tell you this thing not in IE but in another can be found they never tell you use other whenever you need a thing and never can be found in their software. you need to more beware of IE because they make them commorcial not really for public if really then why they stop wxp user to use them as well firefox and chrome never force. because they need a thing that force more then more copy of windows sale. so they thing to add a thing in window 8. the IE9 they thing to make before that they thing to make  this for windows 8. they always force user to purchase this for this. this for this. and this trick sell their software. well outside MS Mozilla and Chrome all behave better with user and their feedback. they respect user their privacy and feedback. if you not believe that how much problem you found in IE and they got solved soon as in chrome and firefox bug kill soon. because IE not opensource we need to  boycutt them secondly their is no customization then they make user task easier even with twitter and facebook.

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• Wireless connection by using command screen

  - by Amadeus

  I installed Ubuntu 12.04 armhf to my beagleboard-xm and now trying to connect to a wireless network. First, I checked if I can search for available networks: ubuntu@arm:~$ iwlist scan lo Interface doesn't support scanning. usb0 Interface doesn't support scanning. wlan0 Scan completed : Cell 01 - Address: EA:7D:EF:60:C9:0B Channel:1 Frequency:2.412 GHz (Channel 1) Quality=70/70 Signal level=-23 dBm Encryption key:on ESSID:"ghostrider" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s 24 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s Mode:Ad-Hoc Extra:tsf=000000005a1ab50e Extra: Last beacon: 6242ms ago IE: Unknown: 000A67686F73747269646572 IE: Unknown: 010882848B962430486C IE: Unknown: 030101 IE: Unknown: 06020000 IE: Unknown: 2A0100 IE: Unknown: 2F0100 IE: Unknown: 32040C121860 IE: Unknown: 2D1A2C181BFF00000000000000000000000000000000000000000000 IE: Unknown: 3D16010800000000FF000000000000000000000000000000 IE: Unknown: DD09001018020000000000 Then I edited /etc/network/interfaces file to the following: root@arm:/etc/wpa_supplicant# cat /etc/network/interfaces auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp # Example to keep MAC address between reboots #hwaddress ether DE:AD:BE:EF:CA:FE # WiFi Example auto wlan0 iface wlan0 inet dhcp wpa-ssid "ghostrider" wpa-psk "b34d373eb2fb836a43b0afffe783c7d0af694724506c9e77b06d1021302905bf" But I cannot still connect to the wireless network: root@arm:/etc/wpa_supplicant# iwconfig lo no wireless extensions. usb0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:off/any Mode:Managed Access Point: Not-Asociated Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:on eth0 no wireless extensions. root@arm:/etc/network# ifup wlan0 Failed to bring up wlan0. What is wrong? Should I change any other files also? But I think it was enough. By the way if you are curious about where that wpa-psk came from: zero@ghostrider:~$ wpa_passphrase ghostrider 34bddf67c2 network={ ssid="ghostrider" #psk="34bddf67c2" psk=b34d373eb2fb836a43b0afffe783c7d0af694724506c9e77b06d1021302905bf } I will appreciate any effort to help. Regards, Amadeus ps: Also I tried to connect manually: root@arm:/etc/network# iwconfig wlan0 essid ghostrider key s:34bddf67c2 But this did not solve my problem also.

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• TechEd 2010 Day Three: The Database Designer (Isn't)

  - by BuckWoody

  Yesterday at TechEd 2010 here in New Orleans I worked the front-booth, answering general SQL Server questions for the masses. I was actually a little surprised to find most of the questions I got were from folks that wanted to know more about Stream Insight and Master Data Services. In past conferences I've been asked a lot of "free consulting" questions, about problems folks have had from older products. I don't mind that a bit - in fact, I'm always happy to help in any way I can. But this time people are really interested in the new features in the product, and I like that they are thinking ahead, not just having to solve problems in production. My presentation was on "Database Design in an Hour". We had the usual fun, and SideShow Bob made an appearance - I kid you not. The guy in the back of the room looked just like Sideshow Bob, so I quickly held a "bes thair" contest, and he won. Duing the presentation, I explain the tools you can use to design databases. I also explain that the "Database Designer" tool in SQL Server Management Studio (SSMS) isn't truly a desinger - it uses non-standard notation, doesn't have a meta-data dictionary, and worst of all, it works at the physical level. In other words, whatever you do in SSMS will automatically change the field/table/relationship structures in the database. We fixed this in SSMS 2008 and higher by adding an option to block that, but the tool is not a good design function nonetheless. To be fair, no one I know of at Microsoft recommends that it is - but I was shocked to hear so many developers in the room defending it as a good tool. I think the main issue for someone who doesn't have to work with Relational Systems a great deal is that it can be difficult to figure out Foreign Keys. The syntax makes them look "backwards", so it's just easier to grab a field and place it on the table you want to point to. There are options. You can download a couple of free tools (CA has a community edition of ER-WIN, Quest has one, and Embarcadero also has one) and if you design more than one or two databases a year, it may be worth buying a true design tool. For years I used Visio, but we changed it so that it doesn't forward-engineer (create the DDL) any more, so it isn't a true design tool either. So investigate those free and not-so-free tools. You'll find they help you in your job - but stay away from the Database Designer in SSMS. Or I'll send Sideshow Bob over there to straighten you out. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• June 2013 release of SSDT contains a minor bug that you should be aware of

  - by jamiet

  I have discovered what seems, to me, like a bug in the June 2013 release of SSDT and given the problems that it created yesterday on my current gig I thought it prudent to write this blog post to inform people of it. I’ve built a very simple SSDT project to reproduce the problem that has just two tables, [Table1] and [Table2], and also a procedure [Procedure1]: The two tables have exactly the same definition, both a have a single column called [Id] of type integer. CREATE TABLE [dbo].[Table1] (     [Id] INT NOT NULL PRIMARY KEY ) My stored procedure simply joins the two together, orders them by the column used in the join predicate, and returns the results: CREATE PROCEDURE [dbo].[Procedure1] AS     SELECT t1.*     FROM    Table1 t1     INNER JOIN Table2 t2         ON    t1.Id = t2.Id     ORDER BY Id Now if I create those three objects manually and then execute the stored procedure, it works fine: So we know that the code works. Unfortunately, SSDT thinks that there is an error here: The text of that error is: Procedure: [dbo].[Procedure1] contains an unresolved reference to an object. Either the object does not exist or the reference is ambiguous because it could refer to any of the following objects: [dbo].[Table1].[Id] or [dbo].[Table2].[Id]. Its complaining that the [Id] field in the ORDER BY clause is ambiguous. Now you may well be thinking at this point “OK, just stick a table alias into the ORDER BY predicate and everything will be fine!” Well that’s true, but there’s a bigger problem here. One of the developers at my current client installed this drop of SSDT and all of a sudden all the builds started failing on his machine – he had errors left right and centre because, as it transpires, we have a fair bit of code that exhibits this scenario.  Worse, previous installations of SSDT do not flag this code as erroneous and therein lies the rub. We immediately had a mass panic where we had to run around the department to our developers (of which there are many) ensuring that none of them should upgrade their SSDT installation if they wanted to carry on being productive for the rest of the day. Also bear in mind that as soon as a new drop of SSDT comes out then the previous version is instantly unavailable so rolling back is going to be impossible unless you have created an administrative install of SSDT for that previous version. Just thought you should know! In the grand schema of things this isn’t a big deal as the bug can be worked around with a simple code modification but forewarned is forearmed so they say! Last thing to say, if you want to know which version of SSDT you are running check my blog post Which version of SSDT Database Projects do I have installed? @Jamiet

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• Storing hierarchical template into a database

  - by pduersteler

  If this title is ambiguous, feel free to change it, I don't know how to put this in a one-liner. Example: Let's assume you have a html template which contains some custom tags, like <text_field />. We now create a page based on a template containing more of those custom tags. When a user wants to edit the page, he sees a text field. he can input things and save it. This looks fairly easy to set up. You either have something like a template_positions table which stores the content of those fields. Case: I now have a bit of a blockade keeping things as simple as possible. Assume you have the same tag given in your example, and additionally, <layout> and <repeat> tags. Here's an example how they should be used: <repeat> <layout name="image-left"> <image /> <text_field /> </layout> <layout name="image-right"> <text_field /> <image /> </layout> </repeat> We now have a block which can be repeated, obviously. This means: when creting/editing a page containing such a template block, I can choose between a layout image-left and image-right which then gets inserted as content element (where content for <image /> and <text_field /> gets stored). And because this is inside a <repeat>, content elements from the given layouts can be inserted multiple times. How do you store this? Simply said, this could be stored with the same setup I've wrote in the example above, I just need to add a parent_id or something similiar to maintain a hierarchy. but I think I am missing something. At least the relation between an inserted content element and the origin/insertion point is missing. And what happens when I update the template file? Do I have to give every custom tag that acts as editable part of a template an identifier that matches an identifier in the template to substitue them correctly? Or can you think of a clean solution that might be better?

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• Designing Snake AI

  - by Ronald

  I'm new to this gamedev stackechange but have used the math and cs sites before. So, I'm in a competition to create AI for a snake that will compete with 3 other snakes in 5 minute rounds where the rules are much like the traditional Nokia snake game except that there are 4 snakes, the board is 50x50 and there are a number of small obstacles on the field. Like the Nokia game, your snake grows when you get to the fruit and if you crash into yourself, another snake or the wall you die. The game runs with a 50ms delay between moves and the server sends the new game state every 50ms which the code must analyze and what not and output the next move. The winner is the snake who had the longest length at any point in the game. Tie breakers are decided by kills. So far what I have done is implemented an A* graph search from each snake to determine if my snake is the closest to the apple and if it is, it goes for the apple. Otherwise, I made a neat little algorithm to determine the emptiest area of the board, which my snake goes for, to anticipate the next apple. Other than this I have some small survivability checks to ensure my snake isn't walking into a trap that it can't get out and if it does get stuck, I have something to give it a better chance of getting out. ... Anyway, I've tested my snake on a test server and it does quite well. Generally, my strategy of only going for the apple when its a sure thing and finding space when its not makes it grow faster than any other snakes (some snakes do a similar thing but often just go to the middle or a corner) sometimes it wins these trial games but is more often than not beaten by the same snake who seems to have the edge on survivability(my snake grows quicker but then dies somehow and this other snake just plods slowly along and wins on consistency. So I was wondering about any ideas anyone has to try and improve my snake. Or maybe ideas at a new approach to take. My functions and classes are good so changes that might seem drastic shouldn't be too bad. I encourage all ideas. Any thoughts ??

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• 'Unable to mount Filesystem' Error

  - by Charles

  Trying to extract data from a 'bricked' Western Digital MyBook Live 2tb drive. I came across a forum that advised to use Ubuntu (booted from a CD) on my Macbook. Managed to download and create a boot CD for Ubuntu (like this little operating system btw). Booted the machine with the CD and plugged the drive (which I had extracted from it's casing and placed into a external USB SATA case & plugged to the laptop). The drive is seen by Ubuntu but each time I click on the drive, it gives me the following error: Unable to mount 2.0 TB Filesystem Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sdb4, missing codepage or helper program, or other error In some cases useful info is found in syslog -try dmesg | tail or so I am new to this and spent quite some time searching this site to see if I could find a solution to this problem without troubling anyone. I came up with a few that came close but some of the questioners mentioned that they had lost data...which scared me from going further. I need to basically extract 1 particular folder from the drive. If I can get to mount this volume 'sdb4', there is a folder called 'My_Work' which I need to back up. The rest I have/had a copy of. When I typed in dmesg | tail...I got several lines..but I think ones that are relevant are: [ 406.864677] EXT4-fs (sdb4): bad block size 65536 [ 429.098776] hfs: write access to a journaled filesystem is not supported, use the force option at your own risk, mounting read-only [ 439.786365] hfs: write access to a journaled filesystem is not supported, use the force option at your own risk, mounting read-only [ 445.982692] EXT4-fs (sdb4): bad block size 65536 [ 1565.841690] EXT4-fs (sdb4): bad block size 65536 I read somewhere to try/check 'sudo fdisk -l /dev/sdb4'. It gave me the following result: Disk /dev/sdb44: 1995.8 GB, 1995774623744 bytes 255 heads, 63 sectors/track, 242639 cylinders, total 3897997312 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdb4 doesn't contain a valid partition table This is where I reached and got frustrated and decided to try & get help on this without digging myself deeper into a hole! I understand that the answer may already be out there. If so, could someone please point me in the right direction. And if not, could someone please resolve (if possible) my situation!

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• Are separate business objects needed when persistent data can be stored in a usable format?

  - by Kylotan

  I have a system where data is stored in a persistent store and read by a server application. Some of this data is only ever seen by the server, but some of it is passed through unaltered to clients. So, there is a big temptation to persist data - whether whole rows/documents or individual fields/sub-documents - in the exact form that the client can use (eg. JSON), as this removes various layers of boilerplate, whether in the form of procedural SQL, an ORM, or any proxy structure which exists just to hold the values before having to re-encode them into a client-suitable form. This form can usually be used on the server too, though business logic may have to live outside of the object, On the other hand, this approach ends up leaking implementation details everywhere. 9 times out of 10 I'm happy just to read a JSON structure out of the DB and send it to the client, but 1 in every 10 times I have to know the details of that implicit structure (and be able to refactor access to it if the stored data ever changes). And this makes me think that maybe I should be pulling this data into separate business objects, so that business logic doesn't have to change when the data schema does. (Though you could argue this just moves the problem rather than solves it.) There is a complicating factor in that our data schema is constantly changing rapidly, to the point where we dropped our previous ORM/RDBMS system in favour of MongoDB and an implicit schema which was much easier to work with. So far I've not decided whether the rapid schema changes make me wish for separate business objects (so that server-side calculations need less refactoring, since all changes are restricted to the persistence layer) or for no separate business objects (because every change to the schema requires the business objects to change to stay in sync, even if the new sub-object or field is never used on the server except to pass verbatim to a client). So my question is whether it is sensible to store objects in the form they are usually going to be used, or if it's better to copy them into intermediate business objects to insulate both sides from each other (even when that isn't strictly necessary)? And I'd like to hear from anybody else who has had experience of a similar situation, perhaps choosing to persist XML or JSON instead of having an explicit schema which has to be assembled into a client format each time.

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• How to get around the Circular Reference issue with JSON and Entity

  - by DanScan

  I have been experimenting with creating a website that leverages MVC with JSON for my presentation layer and Entity framework for data model/database. My Issue comes into play with serializing my Model objects into JSON. I am using the code first method to create my database. When doing the code first method a one to many relationship (parent/child) requires the child to have a reference back to the parent. (Example code my be a typo but you get the picture) class parent { public List<child> Children{get;set;} public int Id{get;set;} } class child { public int ParentId{get;set;} [ForeignKey("ParentId")] public parent MyParent{get;set;} public string name{get;set;} } When returning a "parent" object via a JsonResult a circular reference error is thrown because "child" has a property of class parent. I have tried the ScriptIgnore attribute but I lose the ability to look at the child objects. I will need to display information in a parent child view at some point. I have tried to make base classes for both parent and child that do not have a circular reference. Unfortunately when I attempt to send the baseParent and baseChild these are read by the JSON Parser as their derived classes (I am pretty sure this concept is escaping me). Base.baseParent basep = (Base.baseParent)parent; return Json(basep, JsonRequestBehavior.AllowGet); The one solution I have come up with is to create "View" Models. I create simple versions of the database models that do not include the reference to the parent class. These view models each have method to return the Database Version and a constructor that takes the database model as a parameter (viewmodel.name = databasemodel.name). This method seems forced although it works. NOTE:I am posting here because I think this is more discussion worthy. I could leverage a different design pattern to over come this issue or it could be as simple as using a different attribute on my model. In my searching I have not seen a good method to overcome this problem. My end goal would be to have a nice MVC application that heavily leverages JSON for communicating with the server and displaying data. While maintaining a consistant model across layers (or as best as I can come up with).

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• What are different ways to reduce latency between a server and a web application? [closed]

  - by jjoensuu

  this is a question about a web application that provides SOAP web services. For the sake of this question, this web app is hosted on a server SERVER B which is located in California. We have an automated, scheduled, process running on a server SERVER A, located in New York. This scheduled process is supposed to send SOAP messages to SERVER B every so often, but this process typically dies soon after starting. We have now been told by the vendor that reason why the process dies is because of the latency between SERVER A and SERVER B. The data traffic is routed through many diffent public networks. There is no dedicated line between SERVER A and SERVER B. As a result I have been asked to look into ways to reduce the latency between SERVER A and SERVER B. So I wanted to ask, what are the different ways to reduce latency in a situation like this? For example, would it help to switch from HTTPS to some other secure protocol? (the thought here is that perhaps some other alternative would require fewer handshakes than HTTPS). Or would a VPN help? If a VPN would reduce the latency, how would it do that? NOTE: I am not looking for an explicit answer that would work in my specific situation. I am more like looking just for a simple list of what technologies could be used for this. I will still have to evaluate the technologies and discuss them internally with others, so the list would just be a starting point. Here I am assuming that there exists very few ways to reduce latency between two servers that communicate across public networks using HTTPS. Feel free to correct me if this assumption is wrong and please ask if there is a need for specific information. NOTE 2: A list of technologies is a specific answer to the question I stated in the title. NOTE 3: Its rather dumb to close this question when it is after all about me looking for information and furthermore this information can clearly be useful for others. Anyway luckily there are other sites where I can ask around. StackExchange seems to attached to their own philosophical principles. Many thanks

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• Understanding the levels of computing

  - by RParadox

  Sorry, for my confused question. I'm looking for some pointers. Up to now I have been working mostly with Java and Python on the application layer and I have only a vague understanding of operating systems and hardware. I want to understand much more about the lower levels of computing, but it gets really overwhelming somehow. At university I took a class about microprogramming, i.e. how processors get hard-wired to implement the ASM codes. Up to now I always thought I wouldn't get more done if learned more about the "low level". One question I have is: how is it even possible that hardware gets hidden almost completely from the developer? Is it accurate to say that the operating system is a software layer for the hardware? One small example: in programming I have never come across the need to understand what L2 or L3 Cache is. For the typical business application environment one almost never needs to understand assembler and the lower levels of computing, because nowadays there is a technology stack for almost anything. I guess the whole point of these lower levels is to provide an interface to higher levels. On the other hand I wonder how much influence the lower levels can have, for example this whole graphics computing thing. So, on the other hand, there is this theoretical computer science branch, which works on abstract computing models. However, I also rarely encountered situations, where I found it helpful thinking in the categories of complexity models, proof verification, etc. I sort of know, that there is a complexity class called NP, and that they are kind of impossible to solve for a big number of N. What I'm missing is a reference for a framework to think about these things. It seems to me, that there all kinds of different camps, who rarely interact. The last few weeks I have been reading about security issues. Here somehow, much of the different layers come together. Attacks and exploits almost always occur on the lower level, so in this case it is necessary to learn about the details of the OSI layers, the inner workings of an OS, etc.

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