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• What to "CRM" in San Francisco? CRM Highlights for OpenWorld '12

  - by Richard Lefebvre

  There is plenty to SEE for CRM during OpenWorld in San Francisco, September 30 - October 4! Here are some of the sessions in the CRM Track that you might want to consider attending for products you currently own or might consider for the future. I think you'll agree, there is quite a bit of investment going on across Oracle CRM. Please use OpenWorld Schedule Builder or check the OpenWorld Content Catalog for all of the session details and any time or location changes. Tip: Pre-enrolled session registrants via Schedule Builder are allowed into the session rooms before anyone else, so Schedule Builder will guarantee you a seat. Many of the sessions below will likely be at capacity. General Session: Oracle Fusion CRM—Improving Sales Effectiveness, Efficiency, and Ease of Use (Session ID: GEN9674) - Oct 2, 11:45 AM - 12:45 PM. Anthony Lye, Senior VP, Oracle leads this general session focused on Oracle Fusion CRM. Oracle Fusion CRM optimizes territories, combines quota management and incentive compensation, integrates sales and marketing, and cleanses and enriches data—all within a single application platform. Oracle Fusion can be configured, changed, and extended at runtime by end users, business managers, IT, and developers. Oracle Fusion CRM can be used from the Web, from a smartphone, from Microsoft Outlook, or from an iPad. Deloitte, sponsor of the CRM Track, will also present key concepts on CRM implementations. Oracle Fusion Customer Relationship Management: Overview/Strategy/Customer Experiences/Roadmap (CON9407) - Oct 1, 3:15PM - 4:15PM. In this session, learn how Oracle Fusion CRM enables companies to create better sales plans, generate more quality leads, and achieve higher win rates and find out why customers are adopting Oracle Fusion CRM. Gain a deeper understanding of the unique capabilities only Oracle Fusion CRM provides, and learn how Oracle’s commitment to CRM innovation is driving a wide range of future enhancements. Oracle RightNow CX Cloud Service Vision and Roadmap (CON9764) - Oct 1, 10:45 AM - 11:45 AM. Oracle RightNow CX Cloud Service combines Web, social, and contact center experiences for a unified, cross-channel service solution in the cloud, enabling organizations to increase sales and adoption, build trust, strengthen relationships, and reduce costs and effort. Come to this session to hear from Oracle experts about where the product is going and how Oracle is committed to accelerating the pace of innovation and value to its customers. Siebel CRM Overview, Strategy, and Roadmap (CON9700) - Oct 1, 12:15PM - 1:15PM. The world’s most complete CRM solution, Oracle’s Siebel CRM helps organizations differentiate their businesses. Come to this session to learn about the Siebel product roadmap and how Oracle is committed to accelerating the pace of innovation and value for its customers on this platform. Additionally, the session covers how Siebel customers can leverage many Oracle assets such as Oracle WebCenter Sites; InQuira, RightNow, and ATG/Endeca applications, and Oracle Policy Automation in conjunction with their current Siebel investments. Oracle Fusion Social CRM Strategy and Roadmap: Future of Collaboration and Social Engagement (CON9750) - Oct 4, 11:15 AM - 12:15 PM. Social is changing the customer experience! Come find out how Oracle can help you know your customers better, encourage brand affinity, and improve collaboration within your ecosystem. This session reviews Oracle’s social media solution and shows how you can discover hidden insights buried in your enterprise and social data. Also learn how Oracle Social Network revolutionizes how enterprise users work, collaborate, and share to achieve successful outcomes. Oracle CRM On Demand Strategy and Roadmap (CON9727) - Oct 1, 10:45AM - 11:45AM. Oracle CRM On Demand is a powerful cloud-based customer relationship management solution. Come to this session to learn directly from Oracle experts about future product plans and hear how Oracle is committed to accelerating the pace of innovation and value to its customers. Knowledge Management Roadmap and Strategy (CON9776) - Oct 1, 12:15PM - 1:15PM. Learn how to harness the knowledge created as a natural byproduct of day-to-day interactions to lower costs and improve customer experience by delivering the right answer at the right time across channels. This session includes an overview of Oracle’s product roadmap and vision for knowledge management for both the Oracle RightNow and Oracle Knowledge (formerly InQuira) product families. Oracle Policy Automation Roadmap: Supercharging the Customer Experience (CON9655) - Oct 1, 12:15PM - 1:15PM. Oracle Policy Automation delivers rapid customer value by streamlining the capture, analysis, and deployment of policies across every facet of the customer experience. This session discusses recent Oracle Policy Automation enhancements for policy analytics; the latest Oracle Policy Automation Connector for Siebel; and planned new capabilities, including availability with the Oracle RightNow product line. There is much more, so stay tuned for more highlights or check out the Content Catalog and search for your areas of interest. 

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• Synergy - easy share of keyboard and mouse between multiple computers

  Did you ever have the urge to share one set of keyboard and mouse between multiple machines? If so, please read on... Using multiple machines Honestly, as a software craftsman it is my daily business to run multiple machines - either physical or virtual - to be able to solve my customers' requirements. Recent hardware equipment allows this very easily. For laptops it's a no-brainer to attach a second or even a third screen in order to extend your native display. This works quite handy and in my case I used to attached two additional screens - one via HD15 connector, the other via HDMI. But... as it's a laptop and therefore a mobile unit there are slight restrictions. Detaching and re-attaching all cables when changing locations is one of them but hardware limitations, too. After all, it's a laptop and not a workstation. I guess, that anyone working in IT (or ICT) has more than one machine at their workplace or their home office and at least I find it quite annoying to have multiple sets of keyboard and mouse conquering my remaining space on my desk. Despite the ugly looks of all those cables and whatsoever 'chaos of distraction' I prefer a more clean solution and working environment. This allows me to actually focus on my work and tasks to do rather than to worry about choosing the right combination of keyboard/mouse. My current workplace is a patch work of various pieces of hardware (approx. 2-3 years): DIY desktop on Ubuntu 12.04 64-bit, Core2 Duo (E7400, 2.8GHz), 4GB RAM, 2x 250GB HDD, nVidia GPU 512MB Dell Inspiron 1525 on Windows 8 64-bit, 4GB RAM, 200GB HDD HP Compaq 6720s on Windows Vista 32-bit, Core2 Duo (T5670, 1.8GHz), 2GB RAM, 160GB HDD Mac mini on Mac OS X 10.7, Core i5 (2.3 GHz), 2GB RAM, 500GB HDD I know... Not the latest and greatest but a decent combination to work with. New system(s) is/are already on the shopping list but I live in the 'wrong' country to buy computer hardware. So, the next trip abroad will provide me with some new stuff. Using multiple operating systems The list of hardware above already names different operating systems, and actually I have only one preference: Linux. But still my job as a software craftsman for Visual FoxPro and .NET development requires other OSes, too. Not a big deal, it's just like this. Additionally to those physical machines, there are a bunch of virtual machines around. Most of them running either Windows XP or Windows 7. Since years I have the practice that each development for one customer is isolated into its own virtual machine and environment. This keeps it clean and version-safe. But as you can easily imagine with that setup there are a couple of constraints referring to keyboard and mouse. Usually, those systems require their own pieces of hardware attached. As stated, I don't like clutter on my desk's surface, so a cross-platform solution has to come in here. In the past, I tried it with various applications, hardware or network protocols like X11, RDP, NX, TeamViewer, RAdmin, KVM switch, etc. but the problem in this case is that they either allow you to remotely connect to the other system or exclusively 'bind' your peripherals to the active system. Not optimal after all. Synergy to the rescue Quote from their website: "Synergy lets you easily share your mouse and keyboard between multiple computers on your desk, and it's Free and Open Source. Just move your mouse off the edge of one computer's screen on to another. You can even share all of your clipboards. All you need is a network connection. Synergy is cross-platform (works on Windows, Mac OS X and Linux)." Yep, that's it! All I need for my setup here... Actually, I couldn't believe it myself that I didn't stumble over synergy earlier but 'Get over it' and there we go. And despite the fact that it is Open Source, no, it's also for free. Donations for the developers are very welcome and recently they introduced Synergy Premium. A possibility to buy so-called premium votes that can be used to put more weight / importance on specific issues or bugs that you would like the developers to look into. Installation and configuration Simply download the installation packages for your systems of choice, run the installer and enter some minor information about your network setup. I chose my desktop machine for the role of the Synergy server and configured my screen setup as follows: The screen setup allows you currently to build or connect up to 15 machines. The number of screens can be higher as those machine might have multiple screens physically attached. Synergy takes this into the overall calculations and simply works as expected. I tried it for fun with a second monitor each connected to both laptops to have a total number of 6 active screens. No flaws after all - stunning! All the other machines are configured as clients like so: Side note: The screenshot was taken on Windows 8 and pasted via clipboard into Gimp running on Ubuntu. Resume Synergy is now definitely in my box of tools for my daily work, and amongst the first pieces of software I install after the operating system. It just simplifies my life and cleans my desk. Never again without Synergy!Now, only waiting for an Android version to integrate my Galaxy Tab 10.1, too. ;-) Please, check out that superb product and enjoy sharing one keyboard, one mouse and one clipboard between your various machines and operating systems.

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• Pirates, Treasure Chests and Architectural Mapping

  Pirate 1: Why do pirates create treasure maps? Pirate 2: I do not know.Pirate 1: So they can find their gold. Yes, that was a bad joke, but it does illustrate a point. Pirates are known for drawing treasure maps to their most prized possession. These documents detail the decisions pirates made in order to hide and find their chests of gold. The map allows them to trace the steps they took originally to hide their treasure so that they may return. As software engineers, programmers, and architects we need to treat software implementations much like our treasure chest. Why is software like a treasure chest? It cost money, time,  and resources to develop (Usually) It can make or save money, time, and resources (Hopefully) If we operate under the assumption that software is like a treasure chest then wouldn’t make sense to document the steps, rationale, concerns, and decisions about how it was designed? Pirates are notorious for documenting where they hide their treasure.  Shouldn’t we as creators of software do the same? By documenting our design decisions and rationale behind them will help others be able to understand and maintain implemented systems. This can only be done if the design decisions are correctly mapped to its corresponding implementation. This allows for architectural decisions to be traced from the conceptual model, architectural design and finally to the implementation. Mapping gives software professional a method to trace the reason why specific areas of code were developed verses other options. Just like the pirates we need to able to trace our steps from the start of a project to its implementation,  so that we will understand why specific choices were chosen. The traceability of a software implementation that actually maps back to its originating design decisions is invaluable for ensuring that architectural drifting and erosion does not take place. The drifting and erosion is prevented by allowing others to understand the rational of why an implementation was created in a specific manor or methodology The process of mapping distinct design concerns/decisions to the location of its implemented is called traceability. In this context traceability is defined as method for connecting distinctive software artifacts. This process allows architectural design models and decisions to be directly connected with its physical implementation. The process of mapping architectural design concerns to a software implementation can be very complex. However, most design decision can be placed in  a few generalized categories. Commonly Mapped Design Decisions Design Rationale Components and Connectors Interfaces Behaviors/Properties Design rational is one of the hardest categories to map directly to an implementation. Typically this rational is mapped or document in code via comments. These comments consist of general design decisions and reasoning because they do not directly refer to a specific part of an application. They typically focus more on the higher level concerns. Components and connectors can directly be mapped to architectural concerns. Typically concerns subdivide an application in to distinct functional areas. These functional areas then can map directly back to their originating concerns.Interfaces can be mapped back to design concerns in one of two ways. Interfaces that pertain to specific function definitions can be directly mapped back to its originating concern(s). However, more complicated interfaces require additional analysis to ensure that the proper mappings are created. Depending on the complexity some Behaviors\Properties can be translated directly into a generic implementation structure that is ready for business logic. In addition, some behaviors can be translated directly in to an actual implementation depending on the complexity and architectural tools used. Mapping design concerns to an implementation is a lot of work to maintain, but is doable. In order to ensure that concerns are mapped correctly and that an implementation correctly reflects its design concerns then one of two standard approaches are usually used. All Changes Come From ArchitectureBy forcing all application changes to come through the architectural model prior to implementation then the existing mappings will be used to locate where in the implementation changes need to occur. Allow Changes From Implementation Or Architecture By allowing changes to come from the implementation and/or the architecture then the other area must be kept in sync. This methodology is more complex compared to the previous approach.  One reason to justify the added complexity for an application is due to the fact that this approach tends to detect and prevent architectural drift and erosion. Additionally, this approach is usually maintained via software because of the complexity. Reference:Taylor, R. N., Medvidovic, N., & Dashofy, E. M. (2009). Software architecture: Foundations, theory, and practice Hoboken, NJ: John Wiley & Sons  

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• The design of a generic data synchronizer, or, an [object] that does [actions] with the aid of [helpers]

  - by acheong87

  I'd like to create a generic data-source "synchronizer," where data-source "types" may include MySQL databases, Google Spreadsheets documents, CSV files, among others. I've been trying to figure out how to structure this in terms of classes and interfaces, keeping in mind (what I've read about) composition vs. inheritance and is-a vs. has-a, but each route I go down seems to violate some principle. For simplicity, assume that all data-sources have a header-row-plus-data-rows format. For example, assume that the first rows of Google Spreadsheets documents and CSV files will have column headers, a.k.a. "fields" (to parallel database fields). Also, eventually, I would like to implement this in PHP, but avoiding language-specific discussion would probably be more productive. Here's an overview of what I've tried. Part 1/4: ISyncable class CMySQL implements ISyncable GetFields() // sql query, pdo statement, whatever AddFields() RemFields() ... _dbh class CGoogleSpreadsheets implements ISyncable GetFields() // zend gdata api AddFields() RemFields() ... _spreadsheetKey _worksheetId class CCsvFile implements ISyncable GetFields() // read from buffer AddFields() RemFields() ... _buffer interface ISyncable GetFields() AddFields($field1, $field2, ...) RemFields($field1, $field2, ...) ... CanAddFields() // maybe the spreadsheet is locked for write, or CanRemFields() // maybe no permission to alter a database table ... AddRow() ModRow() RemRow() ... Open() Close() ... First Question: Does it make sense to use an interface, as above? Part 2/4: CSyncer Next, the thing that does the syncing. class CSyncer __construct(ISyncable $A, ISyncable $B) Push() // sync A to B Pull() // sync B to A Sync() // Push() and Pull() only differ in direction; factor. // Sync()'s job is to make sure that the fields on each side // match, to add fields where appropriate and possible, to // account for different column-orderings, etc., and of // course, to add and remove rows as necessary to sync. ... _A _B Second Question: Does it make sense to define such a class, or am I treading dangerously close to the "Kingdom of Nouns"? Part 3/4: CTranslator? ITranslator? Now, here's where I actually get lost, assuming the above is passable. Sometimes, two ISyncables speak different "dialects." For example, believe it or not, Google Spreadsheets (accessed through the Google Data API "list feed") returns column headers lower-cased and stripped of all spaces and symbols! That is, sys_TIMESTAMP is systimestamp, as far as my code can tell. (Yes, I am aware that the "cell feed" does not strip the name so; however cell-by-cell manipulation is too slow for what I'm doing.) One can imagine other hypothetical examples. Perhaps even the data itself can be in different "dialects." But let's take it as given for now, and not argue this if possible. Third Question: How would you implement "translation"? Note: Taking all this as an exercise, I'm more interested in the "idealized" design, rather than the practical one. (God knows that shipped sailed when I began this project.) Part 4/4: Further Thought Here's my train of thought to demonstrate I've thunk, albeit unfruitfully: First, I thought, primitively, "I'll just modify CMySQL::GetFields() to lower-case and strip field names so they're compatible with Google Spreadsheets." But of course, then my class should really be called, CMySQLForGoogleSpreadsheets, and that can't be right. So, the thing which translates must exist outside of an ISyncable implementor. And surely it can't be right to make each translation a method in CSyncer. If it exists outside of both ISyncable and CSyncer, then what is it? (Is it even an "it"?) Is it an abstract class, i.e. abstract CTranslator? Is it an interface, since a translator only does, not has, i.e. interface ITranslator? Does it even require instantiation? e.g. If it's an ITranslator, then should its translation methods be static? (I learned what "late static binding" meant, today.) And, dear God, whatever it is, how should a CSyncer use it? Does it "have" it? Is it, "it"? Who am I? ...am I, "I"? I've attempted to break up the question into sub-questions, but essentially my question is singular: How does one implement an object A that conceptually "links" (has) two objects b1 and b2 that share a common interface B, where certain pairs of b1 and b2 require a helper, e.g. a translator, to be handled by A? Something tells me that I've overcomplicated this design, or violated a principle much higher up. Thank you all very much for your time and any advice you can provide.

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• returning correct multiTouch id

  - by Max

  I've spent countless hours on reading tutorials and looking at every question related to multiTouch from here and Stackoverflow. But I just cannot figure out how to do this correctly. I use a loop to get my pointerId, I dont see alot of people doing this but its the only way I've managed to get it somewhat working. I have two joysticks on my screen, one for moving and one for controlling my sprites rotation and the angle he shoots, like in Monster Shooter. Both these work fine. My problem is that when I Move my sprite at the same time as Im shooting, my touchingPoint for my movement is set to the touchingPoint of my shooting, since the x and y is higher on the touchingPoint of my shooting (moving-stick on left side of screen, shooting-stick on right side), my sprite speeds up, this creates an unwanted change in speed for my sprite. I will post my entire onTouch method here with some variable-changes to make it more understandable. Since I do not know where Im going wrong. public void update(MotionEvent event) { if (event == null && lastEvent == null) { return; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } int pointerCount = event.getPointerCount(); for (int i = 0; i < pointerCount; i++) { int x = (int) event.getX(i); int y = (int) event.getY(i); int id = event.getPointerId(i); int action = event.getActionMasked(); int actionIndex = event.getActionIndex(); String actionString; switch (action) { case MotionEvent.ACTION_DOWN: actionString = "DOWN"; break; case MotionEvent.ACTION_UP: shooting=false; // when shooting is true, it shoots dragging=false; // when dragging is true, it moves actionString = "UP"; break; case MotionEvent.ACTION_POINTER_DOWN: actionString = "PNTR DOWN"; break; case MotionEvent.ACTION_POINTER_UP: shooting=false; dragging=false; actionString = "PNTR UP"; break; case MotionEvent.ACTION_CANCEL: shooting=false; dragging=false; actionString = "CANCEL"; break; case MotionEvent.ACTION_MOVE: try{ if((int) event.getX(id) > 0 && (int) event.getX(id) < touchingBox && (int) event.getY(id) > touchingBox && (int) event.getY(id) < view.getHeight()){ movingPoint.x = (int) event.getX(id); movingPoint.y = (int) event.getY(id); dragging = true; } else if((int) event.getX(id) > touchingBox && (int) event.getX(id) < view.getWidth() && (int) event.getY(id) > touchingBox && (int) event.getY(id) < view.getHeight()){ shootingPoint.x = (int) event.getX(id); shootingPoint.y = (int) event.getY(id); shooting=true; }else{ shooting=false; dragging=false; } }catch(Exception e){ } actionString = "MOVE"; break; default: actionString = ""; } Wouldnt post this much code if I wasnt at an absolute loss of what I'm doing wrong. I simply can not get a good understanding of how multiTouching works. basicly movingPoint changes for both my first and second finger. I bind it to a box, but aslong as I hold one finger within this box, it changes its value based on where my second finger touches. It moves in the right direction and nothing gives an error, the problem is the speed-change, its almost like it adds up the two touchingPoints.

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• Using XA Transactions in Coherence-based Applications

  - by jpurdy

  While the costs of XA transactions are well known (e.g. increased data contention, higher latency, significant disk I/O for logging, availability challenges, etc.), in many cases they are the most attractive option for coordinating logical transactions across multiple resources. There are a few common approaches when integrating Coherence into applications via the use of an application server's transaction manager: Use of Coherence as a read-only cache, applying transactions to the underlying database (or any system of record) instead of the cache. Use of TransactionMap interface via the included resource adapter. Use of the new ACID transaction framework, introduced in Coherence 3.6.   Each of these may have significant drawbacks for certain workloads. Using Coherence as a read-only cache is the simplest option. In this approach, the application is responsible for managing both the database and the cache (either within the business logic or via application server hooks). This approach also tends to provide limited benefit for many workloads, particularly those workloads that either have queries (given the complexity of maintaining a fully cached data set in Coherence) or are not read-heavy (where the cost of managing the cache may outweigh the benefits of reading from it). All updates are made synchronously to the database, leaving it as both a source of latency as well as a potential bottleneck. This approach also prevents addressing "hot data" problems (when certain objects are updated by many concurrent transactions) since most database servers offer no facilities for explicitly controlling concurrent updates. Finally, this option tends to be a better fit for key-based access (rather than filter-based access such as queries) since this makes it easier to aggressively invalidate cache entries without worrying about when they will be reloaded. The advantage of this approach is that it allows strong data consistency as long as optimistic concurrency control is used to ensure that database updates are applied correctly regardless of whether the cache contains stale (or even dirty) data. Another benefit of this approach is that it avoids the limitations of Coherence's write-through caching implementation. TransactionMap is generally used when Coherence acts as system of record. TransactionMap is not generally compatible with write-through caching, so it will usually be either used to manage a standalone cache or when the cache is backed by a database via write-behind caching. TransactionMap has some restrictions that may limit its utility, the most significant being: The lock-based concurrency model is relatively inefficient and may introduce significant latency and contention. As an example, in a typical configuration, a transaction that updates 20 cache entries will require roughly 40ms just for lock management (assuming all locks are granted immediately, and excluding validation and writing which will require a similar amount of time). This may be partially mitigated by denormalizing (e.g. combining a parent object and its set of child objects into a single cache entry), at the cost of increasing false contention (e.g. transactions will conflict even when updating different child objects). If the client (application server JVM) fails during the commit phase, locks will be released immediately, and the transaction may be partially committed. In practice, this is usually not as bad as it may sound since the commit phase is usually very short (all locks having been previously acquired). Note that this vulnerability does not exist when a single NamedCache is used and all updates are confined to a single partition (generally implying the use of partition affinity). The unconventional TransactionMap API is cumbersome but manageable. Only a few methods are transactional, primarily get(), put() and remove(). The ACID transactions framework (accessed via the Connection class) provides atomicity guarantees by implementing the NamedCache interface, maintaining its own cache data and transaction logs inside a set of private partitioned caches. This feature may be used as either a local transactional resource or as logging XA resource. However, a lack of database integration precludes the use of this functionality for most applications. A side effect of this is that this feature has not seen significant adoption, meaning that any use of this is subject to the usual headaches associated with being an early adopter (greater chance of bugs and greater risk of hitting an unoptimized code path). As a result, for the moment, we generally recommend against using this feature. In summary, it is possible to use Coherence in XA-oriented applications, and several customers are doing this successfully, but it is not a core usage model for the product, so care should be taken before committing to this path. For most applications, the most robust solution is normally to use Coherence as a read-only cache of the underlying data resources, even if this prevents taking advantage of certain product features.

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• Runge-Kutta (RK4) integration for game physics

  - by Kai

  Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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• WPF Animation FPS vs. CPU usage - Am I expecting too much?

  - by Cory Charlton

  Working on a screen saver for my wife, http://cchearts.codeplex.com/, and while I've been able to improve FPS on lower end machines (switch from Path to StreamGeometry, use DrawingVisual instead of UserControl, etc) the CPU usage still seems very high. Here's some numbers I ran from a few 5 minute sampling periods: ~60FPS 35% average CPU on Core 2 Duo T7500 @ 2.2GHz, 3GB ram, NVIDIA Quadro NVS 140M (128MB), Vista [My dev laptop] ~40FPS 50% average CPU on Pentium D @ 3.4GHz, 1.5GB ram, Standard VGA Graphics Adapter (unknown), 2003 Server [A crappy desktop] I can understand the lower frame rate and higher CPU usage on the crappy desktop but it still seems pretty high and 35% on my dev laptop seems high as well. I'd really like to analyze the application to get more details but I'm having issues there as well so I'm wondering if I'm doing something wrong (never profiled WPF before). WPF Performance Suite: Process Launch Error Unable to attach to process: CCHearts.exe Do you want to kill it? This error message occurs when I click cancel after attempting launch. If I don't click cancel it sits there idle, I guess waiting to attach. Performance Explorer: Could not launch C:\Projects2\CC.Hearts\CC.Hearts\bin\Debug (USEVISUAL)\CCHearts.exe. Previous attempt to profile the application finished unsuccessfully. Please restart the application. Output Window from Performance: Profiling started. Profiling process ID 5360 (CCHearts). Process ID 5360 has exited. Data written to C:\Projects2\CC.Hearts\CCHearts100608.vsp. Profiling finished. PRF0025: No data was collected. Profiling complete. So I'm stuck wanting to improve performance but have no concrete way to determine where the bottleneck is. Have been relatively successful throwing darts at this point but I'm beyond that now :) PS: Screensaver is hosted at CodePlex if you want to look at the source and missed the link above. Edit: My RenderOptions darts... // NOTE: Grasping at straws here ;-) RenderOptions.SetBitmapScalingMode(newHeart, BitmapScalingMode.LowQuality); RenderOptions.SetCachingHint(newHeart, CachingHint.Cache); RenderOptions.SetEdgeMode(newHeart, EdgeMode.Aliased); I threw those a little while back and didn't see much difference (not sure if the bitmap scaling even comes into play). Really wish I could get profiling working to know where I should try to optimize. For now I assume there is some overhead in creating a new HeartVisual and the DrawingVisual contained inside. Maybe if I reset and reused the hearts (tossed them in a queue once they completed or something) I'd see an improvement. Shrug Throwing darts while blindfolder is always fun.

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• Detecting 'stealth' web-crawlers

  - by Jacco

  What options are there to detect web-crawlers that do not want to be detected? (I know that listing detection techniques will allow the smart stealth-crawler programmer to make a better spider, but I do not think that we will ever be able to block smart stealth-crawlers anyway, only the ones that make mistakes.) I'm not talking about the nice crawlers such as googlebot and Yahoo! Slurp. I consider a bot nice if it: identifies itself as a bot in the user agent string reads robots.txt (and obeys it) I'm talking about the bad crawlers, hiding behind common user agents, using my bandwidth and never giving me anything in return. There are some trapdoors that can be constructed updated list (thanks Chris, gs): Adding a directory only listed (marked as disallow) in the robots.txt, Adding invisible links (possibly marked as rel="nofollow"?), style="display: none;" on link or parent container placed underneath another element with higher z-index detect who doesn't understand CaPiTaLiSaTioN, detect who tries to post replies but always fail the Captcha. detect GET requests to POST-only resources detect interval between requests detect order of pages requested detect who (consistently) requests https resources over http detect who does not request image file (this in combination with a list of user-agents of known image capable browsers works surprisingly nice) Some traps would be triggered by both 'good' and 'bad' bots. you could combine those with a whitelist: It trigger a trap It request robots.txt? It doest not trigger another trap because it obeyed robots.txt One other important thing here is: Please consider blind people using a screen readers: give people a way to contact you, or solve a (non-image) Captcha to continue browsing. What methods are there to automatically detect the web crawlers trying to mask themselves as normal human visitors. Update The question is not: How do I catch every crawler. The question is: How can I maximize the chance of detecting a crawler. Some spiders are really good, and actually parse and understand html, xhtml, css javascript, VB script etc... I have no illusions: I won't be able to beat them. You would however be surprised how stupid some crawlers are. With the best example of stupidity (in my opinion) being: cast all URLs to lower case before requesting them. And then there is a whole bunch of crawlers that are just 'not good enough' to avoid the various trapdoors.

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• List of freely available programming books

  - by Karan Bhangui

  I'm trying to amass a list of programming books with opensource licenses, like Creative Commons, GPL, etc. The books can be about a particular programming language or about computers in general. Hoping you guys could help: Languages BASH Advanced Bash-Scripting Guide (An in-depth exploration of the art of shell scripting) C The C book C++ Thinking in C++ C++ Annotations How to Think Like a Computer Scientist C# .NET Book Zero: What the C or C++ Programmer Needs to Know About C# and the .NET Framework Illustrated C# 2008 (Dead Link) Data Structures and Algorithms with Object-Oriented Design Patterns in C# Threading in C# Common Lisp Practical Common Lisp On Lisp Java Thinking in Java How to Think Like a Computer Scientist Java Thin-Client Programming JavaScript Eloquent JavaScript Haskell Real world Haskell Learn You a Haskell for Great Good! Objective-C The Objective-C Programming Language Perl Extreme Perl (license not specified - home page is saying "freely available") The Mason Book (Open Publication License) Practical mod_perl (CreativeCommons Attribution Share-Alike License) Higher-Order Perl Learning Perl the Hard Way PHP Practical PHP Programming Zend Framework: Survive the Deep End PowerShell Mastering PowerShell Prolog Building Expert Systems in Prolog Adventure in Prolog Prolog Programming A First Course Logic, Programming and Prolog (2ed) Introduction to Prolog for Mathematicians Learn Prolog Now! Natural Language Processing Techniques in Prolog Python Dive Into Python Dive Into Python 3 How to Think Like a Computer Scientist A Byte of Python Python for Fun Invent Your Own Computer Games With Python Ruby Why's (Poignant) Guide to Ruby Programming Ruby - The Pragmatic Programmer's Guide Mr. Neighborly's Humble Little Ruby Book SQL Practical PostgreSQL x86 assembly Paul Carter's tutorial Lua Programming In Lua (for v5 but still largely relevant) Algorithms and Data Structures Algorithms Data Structures and Algorithms with Object-Oriented Design Patterns in Java Planning Algorithms Frameworks/Projects The Django Book The Pylons Book Introduction to Design Patterns in C++ with Qt 4 (Open Publication License) Version control The SVN Book Mercurial: The Definitive Guide Pro Git UNIX / Linux The Art of Unix Programming Linux Device Drivers, Third Edition Others Structure and Interpretation of Computer Programs The Little Book of Semaphores Mathematical Logic - an Introduction An Introduction to the Theory of Computation Developers Developers Developers Developers Linkers and loaders Beej's Guide to Network Programming Maven: The Definitive Guide I will expand on this list as I get comments or when I think of more :D Related: Programming texts and reference material for my Kindle What are some good free programming books? Can anyone recommend a free software engineering book? Edit: Oh I didn't notice the community wiki feature. Feel free to edit your suggestions right in!

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• Why is code quality not popular?

  - by Peter Kofler

  I like my code being in order, i.e. properly formatted, readable, designed, tested, checked for bugs, etc. In fact I am fanatic about it. (Maybe even more than fanatic...) But in my experience actions helping code quality are hardly implemented. (By code quality I mean the quality of the code you produce day to day. The whole topic of software quality with development processes and such is much broader and not the scope of this question.) Code quality does not seem popular. Some examples from my experience include Probably every Java developer knows JUnit, almost all languages implement xUnit frameworks, but in all companies I know, only very few proper unit tests existed (if at all). I know that it's not always possible to write unit tests due to technical limitations or pressing deadlines, but in the cases I saw, unit testing would have been an option. If a developer wanted to write some tests for his/her new code, he/she could do so. My conclusion is that developers do not want to write tests. Static code analysis is often played around in small projects, but not really used to enforce coding conventions or find possible errors in enterprise projects. Usually even compiler warnings like potential null pointer access are ignored. Conference speakers and magazines would talk a lot about EJB3.1, OSGI, Cloud and other new technologies, but hardly about new testing technologies or tools, new static code analysis approaches (e.g. SAT solving), development processes helping to maintain higher quality, how some nasty beast of legacy code was brought under test, ... (I did not attend many conferences and it propably looks different for conferences on agile topics, as unit testing and CI and such has a higer value there.) So why is code quality so unpopular/considered boring? EDIT: Thank your for your answers. Most of them concern unit testing (and has been discussed in a related question). But there are lots of other things that can be used to keep code quality high (see related question). Even if you are not able to use unit tests, you could use a daily build, add some static code analysis to your IDE or development process, try pair programming or enforce reviews of critical code.

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• NSString drawAtPoint Crash on the iPhone (NSString drawAtPoint)

  - by Kyle

  Hey. I have a very simple text output to buffer system which will crash randomly. It will be fine for DAYS, then sometimes it'll crash a few times in a few minutes. The callstack is almost exactly the same for other guys who use higher level controls: http://discussions.apple.com/thread.jspa?messageID=7949746 http://stackoverflow.com/questions/1978997/iphone-app-crashed-assertion-failed-function-evictglyphentryfromstrike-file It crashes at the line (below as well in drawTextToBuffer()): [nsString drawAtPoint:CGPointMake(0, 0) withFont:clFont]; I have the same call of "evict_glyph_entry_from_cache" with the abort calls immediately following it. Apparently it happens to other people. I can say that my NSString* is perfectly fine at the time of the crash. I can read the text from the debugger just fine. static CGColorSpaceRef curColorSpace; static CGContextRef myContext; static float w, h; static int iFontSize; static NSString* sFontName; static UIFont* clFont; static int iLineHeight; unsigned long* txb; /* 256x256x4 Buffer */ void selectFont(int iSize, NSString* sFont) { iFontSize = iSize; clFont = [UIFont fontWithName:sFont size:iFontSize]; iLineHeight = (int)(ceil([clFont capHeight])); } void initText() { w = 256; h = 256; txb = (unsigned long*)malloc_(w * h * 4); curColorSpace = CGColorSpaceCreateDeviceRGB(); myContext = CGBitmapContextCreate(txb, w, h, 8, w * 4, curColorSpace, kCGImageAlphaPremultipliedLast); selectFont(12, @"Helvetica"); } void drawTextToBuffer(NSString* nsString) { CGContextSaveGState(myContext); CGContextSetRGBFillColor(myContext, 1, 1, 1, 1); UIGraphicsPushContext(myContext); /* This line will crash. It crashes even with constant Strings.. At the time of the crash, the pointer to nsString is perfectly fine. The data looks fine! */ [nsString drawAtPoint:CGPointMake(0, 0) withFont:clFont]; UIGraphicsPopContext(); CGContextRestoreGState(myContext); } It will happen with other non-unicode supporting methods as well such as CGContextShowTextAtPoint(); the callstack is similar with that as well. Is this any kind of known issue with the iPhone? Or, perhaps, can something outside of this cause be causing an exception in this particular call (drawAtPoint)?

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• Silverlight 4 Setting background color of textbox on focus

  - by Sean Riedel

  I am trying to set the background color of a Textbox to white on focus using a Style. My enabled Textbox has a Linear Gradient background by default: <Setter Property="Background"> <Setter.Value> <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1"> <GradientStop Color="#e8e8e8" Offset="0.0" /> <GradientStop Color="#f3f3f3" Offset="0.25" /> <GradientStop Color="#f4f4f4" Offset="0.75" /> <GradientStop Color="#f4f4f4" Offset="1.0" /> </LinearGradientBrush> </Setter.Value> </Setter> I have a focus visual state defined: <VisualStateGroup x:Name="FocusStates"> <VisualState x:Name="Focused"> <Storyboard> <DoubleAnimation Storyboard.TargetName="FocusVisualElement" Storyboard.TargetProperty="Opacity" To="1" Duration="0"/> </Storyboard> </VisualState> Here is the rest of the Control Template: <Border x:Name="Border" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="1" Opacity="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}"> <Grid> <Border x:Name="ReadOnlyVisualElement" Opacity="0" Background="#5EC9C9C9"/> <Border x:Name="MouseOverBorder" BorderThickness="1" BorderBrush="Transparent"> <ScrollViewer x:Name="ContentElement" Padding="{TemplateBinding Padding}" BorderThickness="0" IsTabStop="False"/> </Border> </Grid> </Border> <Border x:Name="DisabledVisualElement" Background="#A5D7D7D7" BorderBrush="#A5D7D7D7" BorderThickness="{TemplateBinding BorderThickness}" Opacity="0" IsHitTestVisible="False"/> <Border x:Name="FocusVisualElement" Background="#A5ffffff" BorderBrush="#FF72c1ec" BorderThickness="{TemplateBinding BorderThickness}" Margin="1" Opacity="0" IsHitTestVisible="False"/> On the last Border tag is where I am trying to set the background to white (#ffffff). Right now I have the opacity at A5 which does turn the background white, however it also starts to obscure the text in the box. Any higher opacity makes the text invisible so I am pretty sure that setting the background of that border is not the right way to do this. Can I set the Background color of the ContentElement somehow through a StoryBoard? Thanks.

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• Android Marketplace Error: "The server could not process your apk. Try again."

  - by jdandrea

  I have an updated apk - tested successfully on various devices and simulator instances - with the following manifest: <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.myCompany.appName" android:versionCode="2" android:versionName="1.0.1"> <uses-sdk android:minSdkVersion="3" android:targetSdkVersion="5" /> <uses-permission android:name="android.permission.INTERNET" /> <supports-screens android:largeScreens="true" android:normalScreens="true" android:smallScreens="true" /> <application android:icon="@drawable/icon" android:label="@string/icon_name" android:debuggable="false"> <activity android:name=".myActivity" android:configChanges="keyboardHidden|orientation"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest> When I post to Android Marketplace as an upgrade to my existing 1.0 app, I get the aforementioned ambiguous message: "The server could not process your apk. Try again." I've searched elsewhere for this message in hopes of finding out what might be happening, to no avail. (A popular suggestion is to move the uses-sdk element to the top of the manifest, but as you can see it's already at the top.) Clues welcome/appreciated. Update: I just tried to upload the same file again. Now I get a new message: The new apk's versionCode (2) in AndroidManifest.xml must be higher than the old apk's versionCode (2). The server could not process your apk. Try again. Soooo Marketplace did get my upgraded apk after all? (The very first accepted apk's versionCode was 1, so this update was of course bumped to 2.) Confused … Bumping it up to 3 and trying again. Surprise surprise, I get the original "could not process" error all over again. Going in circles. Hmm ... :( Nuther Update: If I exit and re-enter the Marketplace page, now it shows that the app has been uploaded! Except there's no app icon. Curiouser and curiouser ... and this is all happening with a cache-cleared (standards-friendly) browser to boot. So - do I trust the upload? Or start over ... with versionCode="4"? All I want is to get a solid "Upload successful, here's the icon, ready to publish" type of response.

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• WCF Timeout issue - should there even be a socket connection?

  - by stiank81

  I have a .Net application which is split into a client and server side. The communication between them is handled using WCF. I'm not using the automagic service references, but instead I've built the connection manually like described in the Screencast by Miguel Castro. Summarized this means that I create a console application on the server side that holds ServiceHost objects for the different services: var myServiceHost = new System.ServiceModel.ServiceHost(typeof(MyService), new Uri("net.tcp://localhost:8002")); myServiceHost.Open(); And on the client side I have service proxies creating channels using the ChannelFactory: IMyService proxy = new ChannelFactory<IMyService>("MyServiceEndpoint").CreateChannel(); The client and server side share the service contract defined in the interface IMyService. And another advantage is that I get minimal App.config files - without all the autogenerated stuff created through the Service References. Example from client side: <?xml version="1.0"?> <configuration> <system.serviceModel> <client> <endpoint address="net.tcp://localhost:8002/MyEndpoint" binding="netTcpBinding" contract="IMyService" name="MyServiceEndpoint"/> </client> </system.serviceModel> </configuration> So - to my problem. I create the proxy once, and it holds a channel all the way through the application. However, if I leave the application without use for a few minutes the channel has timed out, and I get the following exception: The socket connection was aborted. This could be caused by an error processing your message or a receive timeout being exceeded by the remote host, or an underlying network resource issue. Local socket timeout was '00:00:59.9979998'. How do I prevent this? I'm assuming I need to specify a higher timeout in my configuration? But I don't want it to ever time out. But on the other hand - I don't want a socket connection! Do I need one? Thought I could go connection less with WCF... What's the permanent solution and best practice on solving this? Set timeout to "never".. Create a new channel for each request? I'm assuming there is some overhead creating the channel?.. Increase the timeout to e.g. 5minutes and create new channel if the connection did timeout? Make it connection less somehow? (Without the overhead of creating channels..) Something else...

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• Color Theory: How to convert Munsell HVC to RGB/HSB/HSL

  - by Ian Boyd

  I'm looking at at document that describes the standard colors used in dentistry to describe the color of a tooth. They quote hue, value, chroma values, and indicate they are from the 1905 Munsell description of color: The system of colour notation developed by A. H. Munsell in 1905 identifies colour in terms of three attributes: HUE, VALUE (Brightness) and CHROMA (saturation) [15] HUE (H): Munsell defined hue as the quality by which we distinguish one colour from another. He selected five principle colours: red, yellow, green, blue, and purple; and five intermediate colours: yellow-red, green-yellow, blue-green, purple-blue, and red-purple. These were placed around a colour circle at equal points and the colours in between these points are a mixture of the two, in favour of the nearer point/colour (see Fig 1.). VALUE (V): This notation indicates the lightness or darkness of a colour in relation to a neutral grey scale, which extends from absolute black (value symbol 0) to absolute white (value symbol 10). This is essentially how ‘bright’ the colour is. CHROMA (C): This indicates the degree of divergence of a given hue from a neutral grey of the same value. The scale of chroma extends from 0 for a neutral grey to 10, 12, 14 or farther, depending upon the strength (saturation) of the sample to be evaluated. There are various systems for categorising colour, the Vita system is most commonly used in Dentistry. This uses the letters A, B, C and D to notate the hue (colour) of the tooth. The chroma and value are both indicated by a value from 1 to 4. A1 being lighter than A4, but A4 being more saturated than A1. If placed in order of value, i.e. brightness, the order from brightest to darkest would be: A1, B1, B2, A2, A3, D2, C1, B3, D3, D4, A3.5, B4, C2, A4, C3, C4 The exact values of Hue, Value and Chroma for each of the shades is shown below (16) So my question is, can anyone convert Munsell HVC into RGB, HSB or HSL? Hue Value (Brightness) Chroma(Saturation) === ================== ================== 4.5 7.80 1.7 2.4 7.45 2.6 1.3 7.40 2.9 1.6 7.05 3.2 1.6 6.70 3.1 5.1 7.75 1.6 4.3 7.50 2.2 2.3 7.25 3.2 2.4 7.00 3.2 4.3 7.30 1.6 2.8 6.90 2.3 2.6 6.70 2.3 1.6 6.30 2.9 3.0 7.35 1.8 1.8 7.10 2.3 3.7 7.05 2.4 They say that Value(Brightness) varies from 0..10, which is fine. So i take 7.05 to mean 70.5%. But what is Hue measured in? i'm used to hue being measured in degrees (0..360). But the values i see would all be red - when they should be more yellow, or brown. Finally, it says that Choma/Saturation can range from 0..10 ...or even higher - which makes it sound like an arbitrary scale. So can anyone convert Munsell HVC to HSB or HSL, or better yet, RGB?

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• C# SerialPort - Problems mixing ports with different baud rates.

  - by GrandAdmiral

  Greetings, I have two devices that I would like to connect over a serial interface, but they have incompatible connections. To get around this problem, I connected them both to my PC and I'm working on a C# program that will route traffic on COM port X to COM port Y and vice versa. The program connects to two COM ports. In the data received event handler, I read in incoming data and write it to the other COM port. To do this, I have the following code: private void HandleDataReceived(SerialPort inPort, SerialPort outPort) { byte[] data = new byte[1]; while (inPort.BytesToRead > 0) { // Read the data data[0] = (byte)inPort.ReadByte(); // Write the data if (outPort.IsOpen) { outPort.Write(data, 0, 1); } } } That code worked fine as long as the outgoing COM port operated at a higher baud rate than the incoming COM port. If the incoming COM port was faster than the outgoing COM port, I started missing data. I had to correct the code like this: private void HandleDataReceived(SerialPort inPort, SerialPort outPort) { byte[] data = new byte[1]; while (inPort.BytesToRead > 0) { // Read the data data[0] = (byte)inPort.ReadByte(); // Write the data if (outPort.IsOpen) { outPort.Write(data, 0, 1); while (outPort.BytesToWrite > 0); //<-- Change to fix problem } } } I don't understand why I need that fix. I'm new to C# (this is my first program), so I'm wondering if there is something I am missing. The SerialPort defaults to a 2048 byte write buffer and my commands are less than ten bytes. The write buffer should have the ability to buffer the data until it can be written to a slower COM port. In summary, I'm receiving data on COM X and writing the data to COM Y. COM X is connected at a faster baud rate than COM Y. Why doesn't the buffering in the write buffer handle this difference? Why does it seem that I need to wait for the write buffer to drain to avoid losing data? Thanks!

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• Why does filter: blur(0) still cause text to blur under Webkit?

  - by johnkavanagh

  I've come across a bug today that's taken far longer than I would like to admit to identify. Essentially: setting a filter: blur(0) (or the vendor-specific -webkit-filter) on an element should - I believe - mean that no form of blur is applied. However, having tested this today, it would appear that Webkit based browsers still blur the text within any element with either blur(0) or blur(0px) assigned to it. I've knocked together a quick Fiddle here: http://jsfiddle.net/f9rBE/ These are three identical dixs containing text (no custom fonts): This has absolutely nothing assigned Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aliquam facilisis orci in quam venenatis, in tempus ipsum sagittis. Suspendisse potenti. Donec ullamcorper lacus vel odio accumsan, vel aliquam libero tempor. Praesent nec libero venenatis, ultrices arcu non, luctus quam. Morbi scelerisque sit amet turpis sit amet tincidunt. Praesent semper erat non purus pretium consequat. Aenean et iaculis turpis. Curabitur diam tellus, consectetur non massa et, commodo venenatis metus. One has no styles at all assigned, the other two have blur(0) and blur(0px): .no-blur{} .zero-px-blur{ -webkit-filter: blur(0px); -moz-filter: blur(0px); -o-filter: blur(0px); -ms-filter: blur(0px); filter: blur(0px); } .zero-blur{ -webkit-filter: blur(0); -moz-filter: blur(0); -o-filter: blur(0); -ms-filter: blur(0); filter: blur(0); } If you preview this under Chrome/Safari you'll see that the text in the second two are still blurred: A few things worth noting: This unintentional blurring occurs in Safari on iOS7 devices (both iPhones and iPads); It also occurs on Chrome and Safari under OSX; It doesn't happen under FireFox in OSX. Of course, this isn't supported at all in Firefox just yet so it's hard to tell whether the behaviour I'm seeing is intentional/expected behaviour, or whether this is a bug in Webkit? Is it possible that this is only prevalent in higher-density resolution devices (ie: retina MacBook/iPhone/iPad)? With this in mind, how do you actually overwrite an item that has blur applied to it to set it back to non-blurred?

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• How can we implement change notification propagation for WPF and SL in the MVVM pattern?

  - by Firoso

  Here's an example scenario targetting MVVM WPF/SL development: View data binds to view model Property "Target" "Target" exposes a field of an object called "data" that exists in the local application model, called "Original" when "Original" changes, it should raise notification to the view model and then propogate that change notification to the View. Here are the solutions I've come up with, but I don't like any of them all that much. I'm looking for other ideas, by the time we come up with something rock solid I'm certain Microsoft will have released .NET 5 with WPF/SL extensions for better tools for MVVM development. For now the question is, "What have you done to solve this problem and how has it worked out for you?" Option 1. Proposal: Attach a handler to data's PropertyChanged event that watches for string values of properties it cares about that might have changed, and raises the appropriate notification. Why I don't like it: Changes don't bubble naturally, objects must be explicitly watched, if data changes to a new source, events must be un-registered/registered. Why I kind of like it: I get explicit control over propogation of changes, and I don't have to use any types that belong at a higher level of the application such as dependancy properties. Option 2. Proposal: Attach a handler to data's PropertyChanged event that re-raises the event across all properties using the name property name. Why I don't like it: This is essentially the same as option 1, but less intelligent, and forces me to never change my property names, as they have to be the same as the property names on data Why I kind of like it: It's very easy to set up and I don't have to think about it... Then again if I try to think, and change names to things that make sense, I shoot myself in the foot, and then I have to think about it! Option 3. Proposal: Inherit my view model from dependancy object, and notify binding sources of changes directly. Why I don't like it: I'm not even 100% sure dependancy properties/objects can DO this, it was just a thought to look into. Also I don't personally feel that WPF/SL types like Dep Obj belong at the view model level. Why I kind of like it: IF it has the capability that I'm seeking then it's a good answer! minus that pesky layering issue. Option 4. Proposal: Use a consistant agent messaging system based off of Task Parallels DataFlow Library to propogate everything through linked pipelining. Why I don't like it: I've never tried this, and somehow I think it will be lacking, plus it requires me to think about my code completely differently all the way around. Why I kind of like it: It has the possiblity of allowing me to do some VERY fun manipulations with a push based data model and using ActionBlocks as validation AND setters to then privately change view model properties and explicitly control PropertyChanged notifications.

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• CSS: background image does not fill when scrolling

  - by rekindleMyLoveOf

  Hi, working on a very small site which loads in one go, so there is a div which holds all the background images, and on top of that (i.e. higher z-index) there is a content div which holds everything. I can switch backgrounds easily based on what content is selected. Unfortunately, I noticed if you launch in a small window so that scrollbars appear, if you scroll there is no background image in the 'revealed' portions of the page. :-( Page structure: <body> <div id="bg"> <div class="bgone"></div> <div class="bgtwo"></div> </div> <div id="container"> <!-- content panels here --> </div> </body> css: #bg { margin: 0px; position: absolute; top: 0px; left: 0px; width:100%; height: 1024px; z-index:1; } .bgone { margin: 0px; position: absolute; width:100%; height: 1024px; background-image:url(../images/one.jpg); background-position:top; background-repeat:repeat-x; z-index:2; } .bgtwo { margin: 0px; position: absolute; width:100%; height: 1024px; background-image:url(../images/two.jpg); background-position:top; background-repeat:repeat-x; z-index:3; } #container { position:relative; width:900px; padding:0px; margin:0px auto; height:600px; z-index:10; }

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• PriorityQueue update problems

  - by Bharat

  After going through a bunch of questions here on SO, I still have no idea what exactly is going wrong with my code and would appreciate some help. I'm trying to implement a priority queue based on f-costs for an A* algorithm, and while the algorithm works fine for short pathfinding distances, it seems to go wrong when there's an obstacle or when the distance between start and goal points is greater than about 30 squares (although sometimes it screws up for less too). while(!m_qOpenList.isEmpty()) { m_xCurrent=m_qOpenList.poll(); m_xCurrent.setBackground(Color.red); m_qClosedList.add(m_xCurrent); if(m_xCurrent.getStatus()==2) { System.out.println("Target Reached"); solved=true; break; } iX=m_xCurrent.getXCo(); iY=m_xCurrent.getYCo(); for(i=iX-1;i<=iX+1;i++) for(j=iY-1;j<=iY+1;j++) { if(i<0||j<0||i>m_iMazeX||j>m_iMazeX||(i==iX&&j==iY) || m_xNode[i][j].getStatus()==4|| m_qClosedList.contains(m_xNode[i][j])) continue; m_xNode[i][j].score(m_xCurrent,m_xGoal); m_qOpenList.add(m_xNode[i][j]); } } It's quite rudimentary as I'm just trying to get it to work for now. m_qOpenList is the PriorityQueue. The problem is that when I debug the program, at some point (near an obstacle), a Node with a fcost of say 84 has higher priority than a node with an fcost of 70. I am not attempting to modify the values once they're on the priority queue. You'll notice that I add at the end of the while loop (I read somewhere that the priorityqueue reorders itself when stuff is added to it), and poll right after that at the beginning. Status of 2 means the Node is the goal, and a status of 4 means that it is unwalkable. public int compareTo(Node o) { if(m_iF<o.m_iF) return -1; if(m_iF>o.m_iF) return 1; return 0; } And that's the compareTo function. Can you see a problem? =(

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• Windows Service HTTPListener Memory Issue

  - by crawshaws

  Hi all, Im a complete novice to the "best practices" etc of writing in any code. I tend to just write it an if it works, why fix it. Well, this way of working is landing me in some hot water. I am writing a simple windows service to server a single webpage. (This service will be incorperated in to another project which monitors the services and some folders on a group of servers.) My problem is that whenever a request is recieved, the memory usage jumps up by a few K per request and keeps qoing up on every request. Now ive found that by putting GC.Collect in the mix it stops at a certain number but im sure its not meant to be used this way. I was wondering if i am missing something or not doing something i should to free up memory. Here is the code: Public Class SimpleWebService : Inherits ServiceBase 'Set the values for the different event log types. Public Const EVENT_ERROR As Integer = 1 Public Const EVENT_WARNING As Integer = 2 Public Const EVENT_INFORMATION As Integer = 4 Public listenerThread As Thread Dim HTTPListner As HttpListener Dim blnKeepAlive As Boolean = True Shared Sub Main() Dim ServicesToRun As ServiceBase() ServicesToRun = New ServiceBase() {New SimpleWebService()} ServiceBase.Run(ServicesToRun) End Sub Protected Overrides Sub OnStart(ByVal args As String()) If Not HttpListener.IsSupported Then CreateEventLogEntry("Windows XP SP2, Server 2003, or higher is required to " & "use the HttpListener class.") Me.Stop() End If Try listenerThread = New Thread(AddressOf ListenForConnections) listenerThread.Start() Catch ex As Exception CreateEventLogEntry(ex.Message) End Try End Sub Protected Overrides Sub OnStop() blnKeepAlive = False End Sub Private Sub CreateEventLogEntry(ByRef strEventContent As String) Dim sSource As String Dim sLog As String sSource = "Service1" sLog = "Application" If Not EventLog.SourceExists(sSource) Then EventLog.CreateEventSource(sSource, sLog) End If Dim ELog As New EventLog(sLog, ".", sSource) ELog.WriteEntry(strEventContent) End Sub Public Sub ListenForConnections() HTTPListner = New HttpListener HTTPListner.Prefixes.Add("http://*:1986/") HTTPListner.Start() Do While blnKeepAlive Dim ctx As HttpListenerContext = HTTPListner.GetContext() Dim HandlerThread As Thread = New Thread(AddressOf ProcessRequest) HandlerThread.Start(ctx) HandlerThread = Nothing Loop HTTPListner.Stop() End Sub Private Sub ProcessRequest(ByVal ctx As HttpListenerContext) Dim sb As StringBuilder = New StringBuilder sb.Append("<html><body><h1>Test My Service</h1>") sb.Append("</body></html>") Dim buffer() As Byte = Encoding.UTF8.GetBytes(sb.ToString) ctx.Response.ContentLength64 = buffer.Length ctx.Response.OutputStream.Write(buffer, 0, buffer.Length) ctx.Response.OutputStream.Close() ctx.Response.Close() sb = Nothing buffer = Nothing ctx = Nothing 'This line seems to keep the mem leak down 'System.GC.Collect() End Sub End Class Please feel free to critisise and tear the code apart but please BE KIND. I have admitted I dont tend to follow the best practice when it comes to coding.

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• Really "wow" them in the interview

  - by Juliet

  Let me put it to you this way: I'm a top-notch programmer, but a notoriously bad interviewee. I've flunked 3 interviews consecutively because I get so nervous that my voice tightens at least 2 octaves higher and I start visibly shaking -- mind you, I can handle whatever technical questions the interviewer throws at me in that state, but I think it looks bad to come off as a quivering, squeaky-voiced young woman during a job interview. I've just got the personality type of a shy computer programmer. No matter how technical I am, I'm going to get passed up in favor of a smooth talker. I have another interview coming up shortly, and I want to really impress the company. Here are my trouble spots: What can I do to be less nervous during my interview? I always get really excited when I hear I have a face-to-face interview, but get more and more anxious as D-Day the interview approaches. My employers wants me to explain what I used to do at my prior employment. I'm a very chatty person and tend to talk/squeak for 10 minutes at a time. How long or short should I time my answers? On that note, when I'm explaining what I did at prior jobs, what exactly is my interviewer looking for? At some point, my interviewer will ask "do you have any questions for me while you're here?" I should, but what kinds of questions should I ask to show that I'm interested in being employed? My interviewer always asks why I'm looking for a new job. The real reason is that my present salary is $27K/yr [Edit to add: and I've yet to get a raise since I started], and I want to make more money -- otherwise the work environment is fine. How do I sugarcoat "I want to make more money" into something that sounds nicer? I have only one prior programmer job, and I've worked there for 18 months, but I have the skill of someone with 4 to 6 years of experience. What can I say to compete against applicants with more work experience? I took a low-paying $27K/yr programming job just to get my foot in IT, and I've been trying to leverage that job as a stepping stone to better opportunities. I get interviews because I consistently out-score senior-level developers in aptitude tests, and my desired salary range is right in the ballpark of what most companies want to offer. Unfortunately, while I've been a programming as a hobby for 10 years and I'm geared to graduate with my BA in Comp Sci in May '09, employers see me as a junior-level programmer with no degree. I want to prove them wrong and get a job that matches my skill level. I'd appreciate any advice anyone has to offer, especially if they can help me get a better job in the process.

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• MaxReceivedMessageSize adjusted, but still getting the QuotaExceedException with WCF

  - by djerry

  Hey guys, First of all, i have read the "millions" of post on this site and some blogs/forum post on other websites, and no answer is solving my problem. I'm my app, there's a possibility to import a txt or csv file with data. In the case of the error, the file contains 444 rows (file is 14,5 kB). When i try to send it to the server to process it, i get an QuotaExceedException, telling me to increase MaxReceivedMessageSize. So i changed it to a much higher value, but i'm still getting the same exception. I'm using the same exact items for client and server in system.servicemodel in my config file. Config snippet : <system.serviceModel> <bindings> <netTcpBinding> <binding name="NetTcpBinding_IMonitoringSystemService" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions" hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="2147483647" maxBufferSize="2147483647" maxConnections="500" maxReceivedMessageSize="2147483647"> <readerQuotas maxDepth="32" maxStringContentLength="100000" maxArrayLength="100000" maxBytesPerRead="100000" maxNameTableCharCount="100000" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="Message"> <transport clientCredentialType="Windows" protectionLevel="EncryptAndSign"> <extendedProtectionPolicy policyEnforcement="Never" /> </transport> <message clientCredentialType="Windows" /> </security> </binding> </netTcpBinding> </bindings> <client> <endpoint address="net.tcp://localhost:8000/Monitoring%20Server" binding="netTcpBinding" bindingConfiguration="NetTcpBinding_IMonitoringSystemService" contract="IMonitoringSystemService" > <!--name="NetTcpBinding_IMonitoringSystemService"--> <identity> <userPrincipalName value="DJERRYY\djerry" /> </identity> </endpoint> </client> </system.serviceModel> Can i use this sample for client and server config? And what should i not use in that case. Thanks in advance.

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• Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

  - by ke3pup

  Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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