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  • Visual Basic Book Excerpt: Useful Namespaces

    This chapter provides an overview of some of the most important system namespaces and gives more detailed examples that demonstrate regular expressions, XML, cryptography, reflection, threading, parallel programming, and Direct3D....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How would you gather client's data on Google App Engine without using Datastore/Backend Instances too much?

    - by ruslan
    I'm relatively new to StackExchange and not sure if it's appropriate place to ask design question. Site gives me a hint "The question you're asking appears subjective and is likely to be closed". Please let me know. Anyway.. One of the projects I'm working on is online survey engine. It's my first big commercial project on Google App Engine. I need your advice on how to collect stats and efficiently record them in DataStore without bankrupting me. Initial requirements are: After user finishes survey client sends list of pairs [ID (int) + PercentHit (double)]. This list shows how close answers of this user match predefined answers of reference answerers (which identified by IDs). I call them "target IDs". Creator of the survey wants to see aggregated % for given IDs for last hour, particular timeframe or from the beginning of the survey. Some surveys may have thousands of target/reference answerers. So I created entity public class HitsStatsDO implements Serializable { @Id transient private Long id; transient private Long version = (long) 0; transient private Long startDate; @Parent transient private Key parent; // fake parent which contains target id @Transient int targetId; private double avgPercent; private long hitCount; } But writing HitsStatsDO for each target from each user would give a lot of data. For instance I had a survey with 3000 targets which was answered by ~4 million people within one week with 300K people taking survey in first day. Even if we assume they were answering it evenly for 24 hours it would give us ~1040 writes/second. Obviously it hits concurrent writes limit of Datastore. I decided I'll collect data for one hour and save that, that's why there are avgPercent and hitCount in HitsStatsDO. GAE instances are stateless so I had to use dynamic backend instance. There I have something like this: // Contains stats for one hour private class Shard { ReadWriteLock lock = new ReentrantReadWriteLock(); Map<Integer, HitsStatsDO> map = new HashMap<Integer, HitsStatsDO>(); // Key is target ID public void saveToDatastore(); public void updateStats(Long startDate, Map<Integer, Double> hits); } and map with shard for current hour and previous hour (which doesn't stay here for long) private HashMap<Long, Shard> shards = new HashMap<Long, Shard>(); // Key is HitsStatsDO.startDate So once per hour I dump Shard for previous hour to Datastore. Plus I have class LifetimeStats which keeps Map<Integer, HitsStatsDO> in memcached where map-key is target ID. Also in my backend shutdown hook method I dump stats for unfinished hour to Datastore. There is only one major issue here - I have only ONE backend instance :) It raises following questions on which I'd like to hear your opinion: Can I do this without using backend instance ? What if one instance is not enough ? How can I split data between multiple dynamic backend instances? It hard because I don't know how many I have because Google creates new one as load increases. I know I can launch exact number of resident backend instances. But how many ? 2, 5, 10 ? What if I have no load at all for a week. Constantly running 10 backend instances is too expensive. What do I do with data from clients while backend instance is dead/restarting? Thank you very much in advance for your thoughts.

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  • Sprinkle Some Magik on that Java Virtual Machine

    - by Jim Connors
    GE Energy, through its Smallworld subsidiary, has been providing geospatial software solutions to the utility and telco markets for over 20 years.  One of the fundamental building blocks of their technology is a dynamically-typed object oriented programming language called Magik.  Like Java, Magik source code is compiled down to bytecodes that run on a virtual machine -- in this case the Magik Virtual Machine. Throughout the years, GE has invested considerable engineering talent in the support and maintenance of this virtual machine.  At the same time vast energy and resources have been invested in the Java Virtual Machine. The question for GE has been whether to continue to make that investment on its own or to leverage massive effort provided by the Java community? Utilizing the Java Virtual Machine instead of maintaining its own virtual machine would give GE more opportunity to focus on application solutions.   At last count, there are dozens, perhaps hundreds of examples of programming languages that have been hosted atop the Java Virtual Machine.  Prior to the release of Java 7, that effort, although certainly possible, was generally less than optimal for languages like Magik because of its dynamic nature.  Java, as a statically typed language had little use for this capability.  In the quest to be a more universal virtual machine, Java 7, via JSR-292, introduced a new bytecode called invokedynamic.  In short, invokedynamic affords a more flexible method call mechanism needed by dynamic languages like Magik. With this new capability GE Energy has succeeded in hosting their Magik environment on top of the Java Virtual Machine.  So you may ask, why would GE wish to do such a thing?  The benefits are many: Competitors to GE Energy claimed that the Magik environment was proprietary.  By utilizing the Java Virtual Machine, that argument gets put to bed.  JVM development is done in open source, where contributions are made world-wide by all types of organizations and individuals. The unprecedented wealth of class libraries and applications written for the Java platform are now opened up to Magik/JVM platform as first class citizens. In addition, the Magik/JVM solution vastly increases the developer pool to include the 9 million Java developers -- the largest developer community on the planet. Applications running on the JVM showed substantial performance gains, in some cases as much as a 5x speed up over the original Magik platform. Legacy Magik applications can still run on the original platform.  They can be seamlessly migrated to run on the JVM by simply recompiling the source code. GE can now leverage the huge Java community.  Undeniably the best virtual machine ever created, hundreds if not thousands of world class developers continually improve, poke, prod and scrutinize all aspects of the Java platform.  As enhancements are made, GE automatically gains access to these. As Magik has little in the way of support for multi-threading, GE will benefit from current and future Java offerings (e.g. lambda expressions) that aim to further facilitate multi-core/multi-threaded application development. As the JVM is available for many more platforms, it broadens the reach of Magik, including the potential to run on a class devices never envisioned just a few short years ago.  For example, Java SE compatible runtime environments are available for popular embedded ARM/Intel/PowerPC configurations that could theoretically host this software too. As compared to other JVM language projects, the Magik integration differs in that it represents a serious commercial entity betting a sizable part of its business on the success of this effort.  Expect to see announcements not only from General Electric, but other organizations as they realize the benefits of utilizing the Java Virtual Machine.

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  • Critical Threads Optimization

    - by Rafael Vanoni
    Background One of the more common issues we've been seeing in the field is the growing difficulty in optimizing performance of multi-threaded applications. A good portion of this difficulty is due to the increasing complexity of modern processors that present various degrees of sharing relationships between hardware components. Take any current CMT processor and you'll find any number of CPUs sharing execution pipelines, floating point units, caches, etc. Consequently, applying the traditional recipe of one software thread for each CPU will have varying degrees of success, according to the layout of the underlying hardware. On top of this increasing complexity we've also seen processors with features that aim at dynamically resourcing software threads according to their utilization. Intel's Turbo Boost allows processors to increase their operating frequency if there is enough thermal headroom available and the processor isn't fully utilized. More recently, the SPARC T4 processor introduced dynamic threading, allowing each core to dynamically allocate more resources to its active CPUs. Both cases are in essence recognizing that current processors will be running a wide mix of workloads, some will be designed for throughput, others for low latency. The hardware is providing mechanisms to dynamically resource threads according to their runtime behavior. We're very aware of these challenges in Solaris, and have been working to provide the best out of box performance while providing mechanisms to further optimize applications when necessary. The Critical Threads Optimzation was introduced in Solaris 10 8/11 and Solaris 11 as one such mechanism that allows customers to both address issues caused by contention over shared hardware resources and explicitly take advantage of features such as T4's dynamic threading. What it is The basic idea is to allow performance critical threads to execute with more exclusive access to hardware resources. For example, when deploying an application that implements a producer/consumer model, it'll likely be advantageous to give the producer more exclusive access to the hardware instead of having it competing for resources with all the consumers. In the case of a T4 based system, we may want to have a producer running by itself on a single core and create one consumer for each of the remaining CPUs. With the Critical Threads Optimization we're extending the semantics of scheduling priorities (which thread should run first) to include priority over shared resources (which thread should have more "space"). Now the scheduler will not only run higher priority threads first: it will also provide them with more exclusive access to hardware resources if they are available. How does it work ? Using the previous example in Solaris 11, all you'd have to do would be to place the producer in the Fixed Priority (FX) scheduling class at priority 60, or in the Real Time (RT) class at any priority and Solaris will try to give it more "hardware space". On both Solaris 10 8/11 and Solaris 11 this can be achieved through the existing priocntl(1,2) and priocntlset(2) interfaces. If your application already assigns these priorities to performance critical threads, there's no additional step you need to take. One important aspect of this optimization is that it requires some level of idleness in the system, either as a result of sizing the application before hand or through periods of transient idleness during runtime. If the system is fully committed, the scheduler will put all the available CPUs to work.Best practices If you're an application developer, we encourage you to look into assigning the right priorities for the different threads in your application. Solaris provides different scheduling classes (Time Share, Interactive, Fair Share, Fixed Priority and Real Time) that offer different policies and behaviors. It is not always simple to figure out which set of threads are critical to the performance of a workload, and it may not always be feasible to take advantage of this optimization, but we believe that this can be correctly (and safely) done during development. Overall, the out of box performance in Solaris should meet your workload's requirements. If you are looking into that extra bit of performance, then the Critical Threads Optimization may be what you're looking for.

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  • Looking for a short book on C# 2010 for experienced programmers

    - by Gaz Davidson
    Hi I'm an experienced programmer (C++, Java, Python, C, Objective-C, and others) and need to take a crash course in C# for my current job. I've never done any C# programming before though have read a bit about the syntax etc, I'm looking for a guide that quickly introduces advanced topics so I can get a handle on the language and begin hacking ASAP. Does anyone know of such a book? Amazon and Google are drawing a blank. Thanks in advance!

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  • Importance of a 1st Class Degree

    - by Nipuna Silva
    I'm currently at the 3rd year following a degree in Software Engineering. I'm thinking of moving into a research field in the future (programming language design, AI etc.) My problems are, What is the advantage/importance of carrying a 1st Class Degree (Honors for Americans) in to the industry rather than with just simple pass. Is it really important to have a 1st Class? Is it the practical knowledge i have to give priority or the theoretical knowledge, or both?

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  • Fireball.CodeEditor

    - by csharp-source.net
    Fireball.CodeEditor is a source editor control with syntax highlight support. It supports some common programming language and you can add your own syntax. Also on the website you can find a software called FireEdit. It is a open source small code editor with support for extensibility from plugins system, more info on the web site, join the forum and help the staff to add feature and find bugs, by testing the control or the application or by making a plugin.

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  • Will polishing my current project be a better learning experience than starting a new one?

    - by Alejandro Cámara
    I started programming many years ago. Now I'm trying to make games. I have read many recommendations to start cloning some well known games like galaga, tetris, arkanoid, etc. I have also read that I should go for the whole game (including menus, sound, score, etc.). Yesterday I finished the first complete version of my arkanoid clone. But it is far from over. I can still work on it for months (I program as a hobby in my free time) implementing a screen resolution switcher, remap of the control keys, power-ups falling from broken bricks, and a huge etc. But I do not want to be forever learning how to clone ONE game. I have the urge to get to the next clone in order to apply some design ideas I have come upon while developing this arkanoid clone (at the same time I am reading the GoF book and much source code from Ludum Dare 21 game contest). So the question is: Should I keep improving the arkanoid clone until it has all the features the original game had? or should I move to the next clone (there are almost infinite games to clone) and start mending the things I did wrong with the previous clone? This can be a very subjective question, so please restrain the answers to the most effective way to learn how to make my own games (not cloning someone ideas). Thank you! CLARIFICATION In order to clarify what I have implemented I make this list: Features implemented: Bouncing capabilities (the ball bounces on walls, on bricks, and on the bar). Sounds when bouncing on bricks and the bar, and when the player wins or loses. Basic title menu (new game and exit only). Also in-game menu and win/lose menus. Only three levels, but the map system is so easy I do not think it will teach me much (am I wrong?). Features not-implemented: Power-ups when breaking the bricks. Complex bricks (with more than one "hit point" and invincible). Better graphics (I am not really good at it). Programming polishing (use more intensively the design patterns). Here's a link to its (minimal) webpage: http://blog.acamara.es/piperine/ I kind of feel ashamed to show it, so please do not hit me too hard :-) My question was related to the not-implemented features. I wondered what was the fastest (optimal) path to learn. 1) implement the not-implemented features in this project which is getting big, or 2) make a new game which probably will teach me those lessons and new ones. ANSWER I choose @ashes999 answer because, in my case, I think I should polish more and try to "ship" the game. I think all the other answers are also important to bear in mind, so if you came here having the same question, before taking a rush decision read all the discussion. Thank you all!

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  • Scriptable user-interfaces/frameworks for automated UI testing

    - by AareP
    I'm planning on using scripting for automated UI testing. Main application is written in c#, and I want it to be scriptable, so I can do everything end-user can do, but programmatically. What do you think of software that provides an interface for scripting, like VBA macros in Excel? Can this be future of all programming, big and small? What is the best way to build such an interface for your own application, dll-based or by parsing own scripting language?

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  • Run On Sentences in Technical Writing

    - by Sean Noodleson Neilan
    This is just a question to think about. When you write technical documentation and programming comments, do you ever find yourself writing run-on sentences in order to be more precise? Is packing more technical information into one sentence better than creating many little sentences each with a little bit of technical information? I know it's better to have lots of little classes in their own little files. Perhaps this doesn't apply to writing?

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  • Why&rsquo;s Poignant Guide To Ruby

    - by Liam McLennan
    According to Wikipedia, “why the lucky stiff was the persona of an anonymous, but prolific writer, cartoonist, musician, artist, and computer programmer”. He looks a bit like Jack Black. His book, Why’s Poignant Guide to Ruby, is a classic, though it can be hard to find since Why disappeared. If you want to learn the Ruby programming language I highly recommend Why’s Poignant Guide to Ruby. I am including a link here so that others who search for it may find it more easily.

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  • Do you have to be good at math to be a good programmer?

    - by Charles Roper
    It seems that conventional wisdom suggests that good programmers are also good at math. Or that the two are somehow intrinsically linked. Many programming books I have read provide many examples that are solutions to math problems, or are somehow related to math as if these examples are what make sense to most people. So the question I would like to float is: do you have to be good at math to be a good programmer?

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  • Essential Tools for the WPF Novice

    When Michael sets out to do something, there are no half-measures; So when he set out to learn WPF, we all stand to benefit from the thorough research that he put into the task. He wondered what utility applications could assist programming in WPF. Here are the fruits of all his work.

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  • Windows 8 AppFest coming to Bangalore on September 21 - 22, 2012

    - by SanjeevAgarwal
    Date: September 21 - 22, 2012 Venue: Karnataka Trade Promotion Organisation (KTPO), Whitefield Below is the itinerary for appfest: AppFest Invitation Participants will be selected based on their app idea. Choose from any of the existing categories in the Windows Store. We look forward to your ideas! Pre AppFest Webcast Tune in for exciting details about AppFest. Stay Tuned AppFest Mentors Microsoft engineers, programming specialists, trainers, and industry-recognized app developers will be onsite...(read more)

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  • What effects do various drugs have on coding style / productivity? [closed]

    - by codecraft
    Can anyone tell me what the effect of various drugs are on coding style, and if coding on drugs can be more productive, or more fun? Are some types of drugs better suited to certain tasks and phases of software development? And which programming languages are best suited to coding on drugs? It would be great if you could back up your answers by data, probably even code snippets showcasing the effect of the drug experience.

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  • What are some reasonable arguments in favor of closed source software? [closed]

    - by Goma
    I like a technology (including programming language) but its platform is closed sourece and many times I meet people who ask me, "why do you use a closed source platform, why not use an open source alternative? If there is something wrong it should be with the closed source not with the open source, (as they say)". Actually I don't know how to answer their question. Could anyone tell me a good answer? Why do you use a closed source platform?

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  • Cloud service and IM protocol advice, for a backend to group chat mobile app

    - by Jonathan
    Overview I’m going to develop an app on Android and iOS. It will allow users to set up group ‘chat rooms’ and talk on chat rooms set up by other users. The service needs to be highly scalable, such that it could accommodate a massive increase in users overnight (we can only dream). Chat requirements The chat protocol used should be flexible: it should allow me to determine who can view/post on ‘chat rooms’ based on certain other factors, as determined by the first poster/creator of the particular ‘chat room’. It should also allow for users to simply install the app and begin using the service, after only providing a simple nickname (which could be changed later). Chat protocol plans Having looked around I think the XMPP protocol is the best candidate. In particular the Multi-user chat extension looks like what I’ll need. Would this be most suited to my requirements, or do you know another potential solution? Cloud service I have been deciding between Amazon Web Services, Google App Engine and Windows Azure. I’m coming to the conclusion that Azure will be best, as it is easier to manage than AWS (ease of scalability will be a key factor in the design), I think it may be less restricted than GAE, plus Azure will soon have toolkits to allow easy interfacing with both Android and iOS phones. Is this the decision you would have made, or would you recommend/look into other cloud services? General project philosophy I have only recently started looking into this project’s feasibility, and am no expert on any of its aspects. So wherever possible I will leave the actual implementations to experts, i.e. choosing a higher-level cloud service, using a well-documented plugin of a, proven reliable, group chat protocol etc. My background I have some programming knowledge from a computer science degree. Main languages I’ve used have been Java and Python, but I don’t want this to affect design decisions for the project. The most appropriate languages for the task should be used, i.e. I don’t mind learning a lot of new skills (my current programming levels are relatively basic anyway). Thank you Thanks for reading, and any advice you have about any aspect would be greatly appreciated :-)

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