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  • What does it mean - to get billed to the 95th percentile at $x.xx per meg?

    - by timofey
    I got a quote from a colo, saying "I could do 3U, the power and 20 megs burstable to 100 for $250 a month with each additional meg billed to the 95th percentile at 6.50 per meg..so you would have he ability to burst if you needed it but not pay for the full 24/7 amount of the IP." I'm assuming it means - 20Mbits unmetered, anything above is billed on the 95th percentile at the rate of $6.50/Mbit. Am I right? And how do you measure the $x.xx per meg, at 95th percentile?

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  • Chrome becomes totally unresponsive - Linux Mint

    - by SpyrosR
    Iam running Linux Mint on my laptop and i have some (serious) problems with Google Chrome.Randomly Chrome becomes totally unresponsive and iam not able to do anything,except restart the system from the power button.I think it's not an issue with system load and/or RAM,because if i for example open lot of "heavy" programs everything seems to work quite fine.When i only run Chrome with not many tabs at random times it freezes the whole system.The weird thing is that Chrome is not heavily loaded with tabs or extensions.I can't figure out what is causing this problem.Any suggestion?Thank you in advance.

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  • run a 2nd computer as an extra processor

    - by MMK
    I have a laptop with a busted l.c.d., but otherwise works fine with an external monitor. I was wondering if it is possible to connect it to my main pc as an extra processor(main pc is getting old, it's only single core processor) and if so how? I currently have them connected with a network cable so that I can access the laptop's hard drive but would like to use it to give my pc a bit more power. Both my pc and my laptop have 2 gb ram and are running windows vista sp2

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  • How to run your own cloud network at home?

    - by Xeoncross
    I have 7 PC's around the house that total more than 10Ghz in CPU power. I was wondering if I could put them to use building my own "cloud computing" network to help with rendering videos, blender animations, Photoshop effects, or anything else. Does something like this exists - and if so what is it called and where do I find it?

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  • Computer randomly reboots during "intensive activity".

    - by Reznor
    My friend has been playing games on his new build for some time now. However, lately, his computer will randomly reboot out of nowhere, so far only happening in game, and presumably only to happen in game as it happens nowhere else. This can happen in game during play or even in the options. Note, it isn't a crash or blue screen. It's just a normal reboot. This started today, I believe, and has only occured in two games: Dead Space and Stalker: Shadow of Chernobyl. He has played a handful of games before these, for about a week or so, without this problem. We theorized on two possibilities: Maybe something is overheating? Maybe the power supply is inadequate? These two were quickly dismissed, as all his components were operating at normal temperatures when he got back to his desktop from the reboot, and we all know these parts don't exactly cool down quickly, especially if they get hot enough to trigger a reboot. Besides, I know at-least my motherboard reports processor overheating at start-up, and requests I press f1 to continue into boot. The PSU one was dismissed too. He has an 850w power supply on a rig that was estimated to take only 720 some watts, that's with some overcompensating to be safe. He opened up his case to make sure nothing was seated wrong or in the way. All was fine, but he did notice a sticker on his video card. It had a giant barcode on it and some numbers. Now, I'm used to seeing these stickers, they're the warranty stickers, right, and removal voids the warranty? Yeah, well, we find it odd because this sticker is slapped right over the circuits of the video card, not on a block or anything. Is this normal? Should he remove it? Right now, I am concerned with the memory. Could that be at fault? Here are his specs: Windows 7 Home Premium, 64-Bit Intel i7 950 EVGA GeForce 570 GTX 4 GB DDR3 PC10666 dual-channel Corsair RAM Corsair 850w PSU Gigabyte GA-X58A-UD3R Western Digital 1 TB WD1001FALS

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  • How to Export/Transfer DHCP data ?

    - by sreevatsa
    We have a very old server HP ML110 its giving hardware ( Power )trouble and we are hosting DHCP services on this on windows 2000 . Now i would like to transfer all the DHCP data ( it has reserved IP ) from this old server to a new server which is win2003 . How do i do ?

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  • Switching efficiently between windows, not apps, in OS X

    - by Vultan
    Previous questions have asked "how can I efficiently switch between windows, not applications, in OS X"? (Switching windows on OS X, Switch between windows on Mac OS X? and others). The most recommended suggestions seem to be: Use some combo of cmd-tab and cmd-~. Use Expose, and possibly Spaces Use Witch I spent the money on Witch, and have been using it for a few weeks; it's ok, but it is sometimes slow to respond, sometimes buggy on window order, crashes my system if I disable and re-enable it too many times, and doesn't work properly with X11 apps. The built-in cmd-tab and cmd-~ are ok, but still bring an entire application to the forefront. I find a very common workflow I use is to bounce back and forth between two windows (for example, a browser window and a Thunderbird email in progress), when both apps (the browser and email software) have multiple windows open. I can use Cmd-Tab to get back and forth between apps, but whenever I switch to an app, ALL windows from that app pop up. That suddenly fills my screen with irrelevant data and windows, and often drops those other windows in front of the single window from the other app that I was using and would conveniently like to keep viewing even though it isn't in focus. Expose seems to be the preferred "OS X natural way," but I can't seem to get myself to use it efficiently. I hit F9, and see 10 windows; I then need to squint, try to find the window I want, then use the mouse or the cursor keys to navigate to the one I want. Given the number of power users who say they use Expose, I must be missing the boat here. My goal is not to make this a repeat of previous questions. I'm not asking "what are my alternatives?" (unless I've missed one above!) Rather, I'm asking: what are you, OS X power users, actually doing to handle the use case I described above? Another common use case for me is having multiple Excel spreadsheets open and multiple browser windows open, and I'm rapidly switching back and forth between one spreadsheet in particular and one browser window. Every time I Cmd-Tab, all spreadsheets or all browser windows appear: I don't want to see the ones I'm not working with, and they tend to hide the windows from the alternative app that I don't have in focus but I'd like to at least eyeball. Can you describe what your workflow is like, and how you rapidly and thoughtlessly switch between windows from apps that have multiple windows open?

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  • After turning off my monitor, the computer won't display again

    - by Nick Lassonde
    If I physically turn off the monitor (DVI connection) and then turn it back on, the connection does not wake back up. The monitor enters "Power Saving" mode. I've tried unplugging the DVI cable and plugging back in, I've tried updating the video card drivers (it's Windows Vista; Windows 7 failed to install on this machine). I can use VNC to connect to the machine again, and after a reboot, the monitor works again. Does anyone have any idea?

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  • New laptop battery: 80% capacity

    - by Danilo
    I have got an old laptop (HP Pavilion DV2000, 5.5 years old) and I just bought a new battery for it (10,8V 5200mAh 6 Cells) probably not an original one. When I charged it full the first time, it reached a capacity (as see through the Ubuntu 12.04 Power Statistics tool) of 80%. After 3 full cycles, it's at 79.5%. Do you think it is normal, or the battery may be damaged (and I can complain with the vendor)?

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  • How can I minimize the amount my router slows down my Internet connection speed?

    - by Lord Torgamus
    Background I'm working with what I assume is a pretty common Internet setup: a cable modem, a wireless router and a few Internet-connected devices. Lately, I've started being more demanding on my Internet connection, and noticed that using my router slows down my download speeds considerably. I just kind of dealt with it until Zune Marketplace on the Xbox 360 told me that a movie was going to take well over ten hours to download, and I just didn't want to wait that long. Good little scientist that I am, I tried to reduce the problem down to one variable. The test As a control, I turned off all the devices in the house that use wireless Internet, and unplugged all the wired devices except for the Xbox. I also power-cycled both the modem and the router. I then tried to download the movie again, and was told that it would still take over ten hours. Next, I unplugged the router, and connected the Xbox directly to the modem. The movie downloaded in just over one hour. As far as I can tell, this means that my ISP, other cable users near me, the remote servers, anything wireless-related and my machines' disk speeds can't be at fault. A similar experiment that replaced the Xbox with a wired laptop produced similar results. To me, this says "the router is responsible for things taking around ten times longer to download." My question I'd still prefer to use the router for a few reasons: it's a pain to connect and disconnect everything every time there's a big file to download direct connection to the modem isn't good for security only one machine can be connected directly to the modem at a time What can I do to have fast connection speeds while still using the router? I don't mind turning other machines off, as long as I don't have to mess with power and ethernet cables. EDIT : After asking this followup question and then this one, I installed dd-wrt on my router, and I seem to be getting higher and more consistent speeds. Perhaps more importantly, my memory use is fairly constant. I know this isn't an answer — which is why I'm not posting it as an answer — but it is how I resolved the situation, and hopefully it'll be helpful for someone.

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  • VMWare Player does not save changes in guest operating system

    - by Giorgos Manoltzas
    I have installed VMWare Player in my Windows 7 Ultimate and I have added Ubuntu 12.10 in a virtual machine. The problem is that every time I power off the virtual machine everything is lost. I mean every program I install or folder i save or anything else is lost completely. And when I start the again the virtual machine is like newly installed. Is there an option to change this (strange) behaviour?

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  • Secure Standalone Server Plus Firewall Unit [closed]

    - by orbitron
    We need to send a 2U server, 1U UPS and 1U firewall to a third-party. The thing is, it needs to be a secured case (locked unit) that has proper airflow and we can have power and networking cables coming out of the back. We've googled far and wide and have only been able to find 'hard case' units that offer some level of security but they are extremely bulky and require freight delivery. Thank you for any insight or solutions.

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  • AGENT: The World's Smartest Watch

    - by Rob Chartier
    AGENT: The World's Smartest Watch by Secret Labs + House of Horology Disclaimer: Most if not all of this content has been gleaned from the comments on the Kickstarter project page and comments section. Any discrepancies between this post and any documentation on agentwatches.com, kickstarter.com, etc.., those official sites take precedence. Overview The next generation smartwatch with brand-new technology. World-class developer tools, unparalleled battery life, Qi wireless charging. Kickstarter Page, Comments Funding period : May 21, 2013 - Jun 20, 2013 MSRP : $249 Other Urls http://www.agentwatches.com/ https://www.facebook.com/agentwatches http://twitter.com/agentwatches http://pinterest.com/agentwatches/ http://paper.li/robchartier/1371234640 Developer Story The first official launch of the preview SDK and emulator will happen on 20-Jun-2013.  All development will be done in Visual Studio 2012, using the .NET Micro Framework SDK 2.3.  The SDK will ship with the first round of the expected API for developers along with an emulator. With that said, there is no need to wait for the SDK.  You can download the tooling now and get started with Apps and Faces immediately.  The only thing that you will not be able to work with is the API; but for example, watch faces, you can start building the basic face rendering with the Bitmap graphics drawing in the .NET Micro Framework.   Does it look good? Before we dig into any more of the gory details, here are a few photos of the current available prototype models.   The watch on the tiny QI Charter   If you wander too far away from your phone, your watch will let you know with a vibration and a message, all but one button will dismiss the message.   An app showing the premium weather data!   Nice stitching on the straps, leather and silicon will be available, along with a few lengths to choose from (short, regular, long lengths). On to those gory details…. Hardware Specs Processor 120MHz ARM Cortex-M4 processor (ATSAM4SD32) with secondary AVR co-processor Flash & RAM 2MB of onboard flash and 160KB of RAM 1/4 of the onboard flash will be used by the OS The flash is permanent (non-volatile) storage. Bluetooth Bluetooth 4.0 BD/EDR + LE Bluetooth 4.0 is backwards compatible with Bluetooth 2.1, so classic Bluetooth functions (BD/EDR, SPP/AVRCP/PBAP/etc.) will work fine. Sensors 3D Accelerometer (Motion) ST LSM303DLHC Ambient Light Sensor Hardware power metering Vibration Motor (You can pulse it to create vibration patterns, not sure about the vibration strength - driven with PWM) No piezo/speaker or microphone. Other QI Wireless Charging, no NFC, no wall adapter included Custom LED Backlight No GPS in the watch. It uses the GPS in your phone. AGENT watch apps are deployed and debugged wirelessly from your PC via Bluetooth. RoHS, Pb-free Battery Expected to use a CR2430-sized rechargeable battery – replaceable (Mouser, Amazon) Estimated charging time from empty is 2 hours with provided charger 7 Days typical with Bluetooth on, 30 days with Bluetooth off (watch-face only mode) The battery should last at least 2 years, with 100s of charge cycles. Physical dimensions Roughly 38mm top-to-bottom on the front face 35mm left-to-right on the front face and around 12mm in depth 22mm strap Two ~1/16" hex screws to attach the watch pin The top watchcase material candidates are PVD stainless steel, brushed matte ceramic, and high-quality polycarbonate (TBD). The glass lens is mineral glass, Anti-glare glass lens Strap options Leather and silicon straps will be available Expected to have three sizes Display 1.28" Sharp Memory Display The display stays on 100% of the time. Dimensions: 128x128 pixels Buttons Custom "Pusher" buttons, they will not make noise like a mouse click, and are very durable. The top-left button activates the backlight; bottom-left changes apps; three buttons on the right are up/select/down and can be used for custom purposes by apps. Backup reset procedure is currently activated by holding the home/menu button and the top-right user button for about ten seconds Device Support Android 2.3 or newer iPhone 4S or newer Windows Phone 8 or newer Heart Rate monitors - Bluetooth SPP or Bluetooth LE (GATT) is what you'll want the heart monitor to support. Almost limitless Bluetooth device support! Internationalization & Localization Full UTF8 Support from the ground up. AGENT's user interface is in English. Your content (caller ID, music tracks, notifications) will be in your native language. We have a plan to cover most major character sets, with Latin characters pre-loaded on the watch. Simplified Chinese will be available Feature overview Phone lost alert Caller ID Music Control (possible volume control) Wireless Charging Timer Stopwatch Vibrating Alarm (possibly custom vibrations for caller id) A few default watch faces Airplane mode (by demand or low power) Can be turned off completely Customizable 3rd party watch faces, applications which can be loaded over bluetooth. Sample apps that maybe installed Weather Sample Apps not installed Exercise App Other Possible Skype integration over Bluetooth. They will provide an AGENT app for your smartphone (iPhone, Android, Windows Phone). You'll be able to use it to load apps onto the watch.. You will be able to cancel phone calls. With compatible phones you can also answer, end, etc. They are adopting the standard hands-free profile to provide these features and caller ID.

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  • Understanding and Controlling Parallel Query Processing in SQL Server

    Data warehousing and general reporting applications tend to be CPU intensive because they need to read and process a large number of rows. To facilitate quick data processing for queries that touch a large amount of data, Microsoft SQL Server exploits the power of multiple logical processors to provide parallel query processing operations such as parallel scans. Through extensive testing, we have learned that, for most large queries that are executed in a parallel fashion, SQL Server can deliver linear or nearly linear response time speedup as the number of logical processors increases. However, some queries in high parallelism scenarios perform suboptimally. There are also some parallelism issues that can occur in a multi-user parallel query workload. This white paper describes parallel performance problems you might encounter when you run such queries and workloads, and it explains why these issues occur. In addition, it presents how data warehouse developers can detect these issues, and how they can work around them or mitigate them.

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  • Parallelism in .NET – Part 16, Creating Tasks via a TaskFactory

    - by Reed
    The Task class in the Task Parallel Library supplies a large set of features.  However, when creating the task, and assigning it to a TaskScheduler, and starting the Task, there are quite a few steps involved.  This gets even more cumbersome when multiple tasks are involved.  Each task must be constructed, duplicating any options required, then started individually, potentially on a specific scheduler.  At first glance, this makes the new Task class seem like more work than ThreadPool.QueueUserWorkItem in .NET 3.5. In order to simplify this process, and make Tasks simple to use in simple cases, without sacrificing their power and flexibility, the Task Parallel Library added a new class: TaskFactory. The TaskFactory class is intended to “Provide support for creating and scheduling Task objects.”  Its entire purpose is to simplify development when working with Task instances.  The Task class provides access to the default TaskFactory via the Task.Factory static property.  By default, TaskFactory uses the default TaskScheduler to schedule tasks on a ThreadPool thread.  By using Task.Factory, we can automatically create and start a task in a single “fire and forget” manner, similar to how we did with ThreadPool.QueueUserWorkItem: Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This provides us with the same level of simplicity we had with ThreadPool.QueueUserWorkItem, but even more power.  For example, we can now easily wait on the task: // Start our task on a background thread var task = Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); // Do other work on the main thread, // while the task above executes in the background this.ExecuteWorkSynchronously(); // Wait for the background task to finish task.Wait(); TaskFactory simplifies creation and startup of simple background tasks dramatically. In addition to using the default TaskFactory, it’s often useful to construct a custom TaskFactory.  The TaskFactory class includes an entire set of constructors which allow you to specify the default configuration for every Task instance created by that factory.  This is particularly useful when using a custom TaskScheduler.  For example, look at the sample code for starting a task on the UI thread in Part 15: // Given the following, constructed on the UI thread // TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // When inside a background task, we can do string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); This is actually quite a bit more complicated than necessary.  When we create the uiScheduler instance, we can use that to construct a TaskFactory that will automatically schedule tasks on the UI thread.  To do that, we’d create the following on our main thread, prior to constructing our background tasks: // Construct a task scheduler from the current SynchronizationContext (UI thread) var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Construct a new TaskFactory using our UI scheduler var uiTaskFactory = new TaskFactory(uiScheduler); If we do this, when we’re on a background thread, we can use this new TaskFactory to marshal a Task back onto the UI thread.  Our previous code simplifies to: // When inside a background task, we can do string status = GetUpdatedStatus(); // Update our UI uiTaskFactory.StartNew( () => statusLabel.Text = status); Notice how much simpler this becomes!  By taking advantage of the convenience provided by a custom TaskFactory, we can now marshal to set data on the UI thread in a single, clear line of code!

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  • Discoverer 11g 11.1.1.2 Certified with EBS 12 on Five New Platforms

    - by Steven Chan
    Oracle Fusion Middleware 11g Release 1 includes Oracle Discoverer.  Discoverer is an ad-hoc query, reporting, analysis, and Web-publishing tool that allows end-users to work directly with Oracle E-Business Suite OLTP data.We certified Discoverer 11gR1 11.1.1.2 with the E-Business Suite Release 11i and 12 on Linux earlier this year.  Our Applications Platforms Group has just released five additional platform certifications for Discoverer 11.1.1.2 for Oracle E-Business Suite Release 12 (12.0.x and 12.1.x).Certified EBS 12 PlatformsLinux x86-64 (Oracle Enterprise Linux 4, 5) Linux x86-64 (RHEL 4, 5) Linux x86-64 (SLES 10) Oracle Solaris on SPARC (64-bit) (Solaris 9, 10) HP-UX Itanium (11.23, 11.31) HP-UX PA-RISC (64-bit) (11.23, 11.31) IBM AIX on Power Systems (64-bit) (5.3, 6.1) Microsoft Windows Server (32-bit) (2003, 2008)

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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  • Ubuntu 10.10 Mouse and Keyboard Freeze

    - by Kev
    I installed Ubuntu 10.10 today and have had mouse problem since. Symptoms: At some arbitrary point in time (frequency: 2-3 times per hour), the mouse and keyboard stops working for ever(may be). I start System monitor, I found out network was shutdown just before mouse freeze. Some time my keyboard keep typing one key. For example:77777777777777777777777777777777777777777777777777777.....(it keep typing for 20 sec) I found out a script just solve the freeze problem:(I hit Powerbutton) -----------------/etc/acpi/powerbtn.sh------------------------ event=button[ /]power action=/usr/sbin/fix_mouse.sh -----------------/usr/sbin/fix_mouse.sh------------------------ rmmod psmouse modprobe psmouse Yesterday I install Ubuntu 10.04 FAILED also have mouse problem. When I switch back to Windows XP. The network card is down. It kept connecting and disconnecting 1 time per sec. CPU: i5 Motherboard: ASUS P7P55D OS: Windows XP + Ubuntu 10.10 Video Card: ATI 5770 Mouse,Keyboard: PS/2

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  • Dell Latitude E6520 overheating

    - by Wu Yi Han
    I'm a newcomer to Ubuntu 11.10. My laptop is a Dell Latitude E6520, Sandy Bridge platform. The system cooling fan is crazy all the time. I don't do any intensive tasks. I really hope my laptop doesn't become a mushroom cloud. I suppose there's no perfect way to solve this... Can I lower the CPU frequency? Jupiter 0.0.51 was installed (power save mode). Cooling worked in my Windows 7 system until I deleted it. (I won't go back to Windows 7.)

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  • Diagnose PC Hardware Problems with an Ubuntu Live CD

    - by Trevor Bekolay
    So your PC randomly shuts down or gives you the blue screen of death, but you can’t figure out what’s wrong. The problem could be bad memory or hardware related, and thankfully the Ubuntu Live CD has some tools to help you figure it out. Test your RAM with memtest86+ RAM problems are difficult to diagnose—they can range from annoying program crashes, or crippling reboot loops. Even if you’re not having problems, when you install new RAM it’s a good idea to thoroughly test it. The Ubuntu Live CD includes a tool called Memtest86+ that will do just that—test your computer’s RAM! Unlike many of the Live CD tools that we’ve looked at so far, Memtest86+ has to be run outside of a graphical Ubuntu session. Fortunately, it only takes a few keystrokes. Note: If you used UNetbootin to create an Ubuntu flash drive, then memtest86+ will not be available. We recommend using the Universal USB Installer from Pendrivelinux instead (persistence is possible with Universal USB Installer, but not mandatory). Boot up your computer with a Ubuntu Live CD or USB drive. You will be greeted with this screen: Use the down arrow key to select the Test memory option and hit Enter. Memtest86+ will immediately start testing your RAM. If you suspect that a certain part of memory is the problem, you can select certain portions of memory by pressing “c” and changing that option. You can also select specific tests to run. However, the default settings of Memtest86+ will exhaustively test your memory, so we recommend leaving the settings alone. Memtest86+ will run a variety of tests that can take some time to complete, so start it running before you go to bed to give it adequate time. Test your CPU with cpuburn Random shutdowns – especially when doing computationally intensive tasks – can be a sign of a faulty CPU, power supply, or cooling system. A utility called cpuburn can help you determine if one of these pieces of hardware is the problem. Note: cpuburn is designed to stress test your computer – it will run it fast and cause the CPU to heat up, which may exacerbate small problems that otherwise would be minor. It is a powerful diagnostic tool, but should be used with caution. Boot up your computer with a Ubuntu Live CD or USB drive, and choose to run Ubuntu from the CD or USB drive. When the desktop environment loads up, open the Synaptic Package Manager by clicking on the System menu in the top-left of the screen, then selecting Administration, and then Synaptic Package Manager. Cpuburn is in the universe repository. To enable the universe repository, click on Settings in the menu at the top, and then Repositories. Add a checkmark in the box labeled “Community-maintained Open Source software (universe)”. Click close. In the main Synaptic window, click the Reload button. After the package list has reloaded and the search index has been rebuilt, enter “cpuburn” in the Quick search text box. Click the checkbox in the left column, and select Mark for Installation. Click the Apply button near the top of the window. As cpuburn installs, it will caution you about the possible dangers of its use. Assuming you wish to take the risk (and if your computer is randomly restarting constantly, it’s probably worth it), open a terminal window by clicking on the Applications menu in the top-left of the screen and then selection Applications > Terminal. Cpuburn includes a number of tools to test different types of CPUs. If your CPU is more than six years old, see the full list; for modern AMD CPUs, use the terminal command burnK7 and for modern Intel processors, use the terminal command burnP6 Our processor is an Intel, so we ran burnP6. Once it started up, it immediately pushed the CPU up to 99.7% total usage, according to the Linux utility “top”. If your computer is having a CPU, power supply, or cooling problem, then your computer is likely to shutdown within ten or fifteen minutes. Because of the strain this program puts on your computer, we don’t recommend leaving it running overnight – if there’s a problem, it should crop up relatively quickly. Cpuburn’s tools, including burnP6, have no interface; once they start running, they will start driving your CPU until you stop them. To stop a program like burnP6, press Ctrl+C in the terminal window that is running the program. Conclusion The Ubuntu Live CD provides two great testing tools to diagnose a tricky computer problem, or to stress test a new computer. While they are advanced tools that should be used with caution, they’re extremely useful and easy enough that anyone can use them. Similar Articles Productive Geek Tips Reset Your Ubuntu Password Easily from the Live CDCreate a Persistent Bootable Ubuntu USB Flash DriveAdding extra Repositories on UbuntuHow to Share folders with your Ubuntu Virtual Machine (guest)Building a New Computer – Part 3: Setting it Up TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Have Fun Editing Photo Editing with Citrify Outlook Connector Upgrade Error Gadfly is a cool Twitter/Silverlight app Enable DreamScene in Windows 7 Microsoft’s “How Do I ?” Videos Home Networks – How do they look like & the problems they cause

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  • Ubuntu 12.04 installation problem

    - by LittleLego
    Okay, at the beginning of the installation, it went well. My laptop is connected to power source, the internet, I have also checked the boxes "install updates while installation", "install third party plugin". After inputting location, keyboard layout info and user's details and password, the installation took place. But after 3/4 of the installation, it stopped, right above the progress bar, it displayed "installing system", I clicked on the arrow below it, the terminal-like screen also stopped carrying out the process. I then clicked on the "Skip" button, nothing happens. I thought it was the problem of my laptop, then I did another fresh installation, same thing happened. The terminal-like screen was showing some different words. But it's not an error message, just some installation info. Does anyone have valuable solution to this problem?

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