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• Communication between state machines with hidden transitions

  - by slartibartfast

  The question emerged for me in embedded programming but I think it can be applied to quite a number of general networking situations e.g. when a communication partner fails. Assume we have an application logic (a program) running on a computer and a gadget connected to that computer via e.g. a serial interface like RS232. The gadget has a red/green/blue LED and a button which disables the LED. The LEDs color can be driven by software commands over the serial interface and the state (red/green/blue/off) is read back and causes a reaction in the application logic. Asynchronous behaviour of the application logic with regard to the LED color down to a certain delay (depending on the execution cycle of the application) is tolerated. What we essentially have is a resource (the LED) which can not be reserved and handled atomically by software because the (organic) user can at any time press the button to interfere/break the software attempt to switch the LED color. Stripping this example from its physical outfit I dare to say that we have two communicating state machines A (application logic) and G (gadget) where G executes state changes unbeknownst to A (and also the other way round, but this is not significant in our example) and only A can be modified at a reasonable price. A needs to see the reaction and state of G in one piece of information which may be (slightly) outdated but not inconsistent with respect to the short time window when this information was generated on the side of G. What I am looking for is a concise method to handle such a situation in embedded software (i.e. no layer/framework like CORBA etc. available). A programming technique which is able to map the complete behaviour of both participants on classical interfaces of a classical programming language (C in this case). To complicate matters (or rather, to generalize), a simple high frequency communication cycle of A to G and back (IOW: A is rapidly polling G) is out of focus because of technical restrictions (delay of serial com, A not always active, etc.). What I currently see as a general solution is: the application logic A as one thread of execution an adapter object (proxy) PG (presenting G inside the computer), together with the serial driver as another thread a communication object between the two (A and PG) which is transactionally safe to exchange The two execution contexts (threads) on the computer may be multi-core or just interrupt driven or tasks in an RTOS. The com object contains the following data: suspected state (written by A): effectively a member of the power set of states in G (in our case: red, green, blue, off, red_or_green, red_or_blue, red_or_off...etc.) command data (written by A): test_if_off, switch_to_red, switch_to_green, switch_to_blue operation status (written by PG): operation_pending, success, wrong_state, link_broken new state (written by PG): red, green, blue, off The idea of the com object is that A writes whichever (set of) state it thinks G is in, together with a command. (Example: suspected state="red_or_green", command: "switch_to_blue") Notice that the commands issued by A will not work if the user has switched off the LED and A needs to know this. PG will pick up such a com object and try to send the command to G, receive its answer (or a timeout) and set the operation status and new state accordingly. A will take back the oject once it is no longer at operation_pending and can react to the outcome. The com object could be separated of course (into two objects, one for each direction) but I think it is convenient in nearly all instances to have the command close to the result. I would like to have major flaws pointed out or hear an entirely different view on such a situation.

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• An Actionable Common Approach to Federal Enterprise Architecture

  - by TedMcLaughlan

  The recent “Common Approach to Federal Enterprise Architecture” (US Executive Office of the President, May 2 2012) is extremely timely and well-organized guidance for the Federal IT investment and deployment community, as useful for Federal Departments and Agencies as it is for their stakeholders and integration partners. The guidance not only helps IT Program Planners and Managers, but also informs and prepares constituents who may be the beneficiaries or otherwise impacted by the investment. The FEA Common Approach extends from and builds on the rapidly-maturing Federal Enterprise Architecture Framework (FEAF) and its associated artifacts and standards, already included to a large degree in the annual Federal Portfolio and Investment Management processes – for example the OMB’s Exhibit 300 (i.e. Business Case justification for IT investments).A very interesting element of this Approach includes the very necessary guidance for actually using an Enterprise Architecture (EA) and/or its collateral – good guidance for any organization charged with maintaining a broad portfolio of IT investments. The associated FEA Reference Models (i.e. the BRM, DRM, TRM, etc.) are very helpful frameworks for organizing, understanding, communicating and standardizing across agencies with respect to vocabularies, architecture patterns and technology standards. Determining when, how and to what level of detail to include these reference models in the typically long-running Federal IT acquisition cycles wasn’t always clear, however, particularly during the first interactions of a Program’s technical and functional leadership with the Mission owners and investment planners. This typically occurs as an agency begins the process of describing its strategy and business case for allocation of new Federal funding, reacting to things like new legislation or policy, real or anticipated mission challenges, or straightforward ROI opportunities (for example the introduction of new technologies that deliver significant cost-savings).The early artifacts (i.e. Resource Allocation Plans, Acquisition Plans, Exhibit 300’s or other Business Case materials, etc.) of the intersection between Mission owners, IT and Program Managers are far easier to understand and discuss, when the overlay of an evolved, actionable Enterprise Architecture (such as the FEA) is applied.  “Actionable” is the key word – too many Public Service entity EA’s (including the FEA) have for too long been used simply as a very highly-abstracted standards reference, duly maintained and nominally-enforced by an Enterprise or System Architect’s office. Refreshing elements of this recent FEA Common Approach include one of the first Federally-documented acknowledgements of the “Solution Architect” (the “Problem-Solving” role). This role collaborates with the Enterprise, System and Business Architecture communities primarily on completing actual “EA Roadmap” documents. These are roadmaps grounded in real cost, technical and functional details that are fully aligned with both contextual expectations (for example the new “Digital Government Strategy” and its required roadmap deliverables - and the rapidly increasing complexities of today’s more portable and transparent IT solutions.  We also expect some very critical synergies to develop in early IT investment cycles between this new breed of “Federal Enterprise Solution Architect” and the first waves of the newly-formal “Federal IT Program Manager” roles operating under more standardized “critical competency” expectations (including EA), likely already to be seriously influencing the quality annual CPIC (Capital Planning and Investment Control) processes.  Our Oracle Enterprise Strategy Team (EST) and associated Oracle Enterprise Architecture (OEA) practices are already engaged in promoting and leveraging the visibility of Enterprise Architecture as a key contributor to early IT investment validation, and we look forward in particular to seeing the real, citizen-centric benefits of this FEA Common Approach in particular surface across the entire Public Service CPIC domain - Federal, State, Local, Tribal and otherwise. Read more Enterprise Architecture blog posts for additional EA insight!

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• The Future of Air Travel: Intelligence and Automation

  - by BobEvans

  Remember those white-knuckle flights through stormy weather where unexpected plunges in altitude result in near-permanent relocations of major internal organs? Perhaps there’s a better way, according to a recent Wall Street Journal article: “Pilots of a Honeywell International Inc. test plane stayed on their initial flight path, relying on the company's latest onboard radar technology to steer through the worst of the weather. The specially outfitted Boeing 757 barely shuddered as it gingerly skirted some of the most ferocious storm cells over Fort Walton Beach and then climbed above the rest in zero visibility.” Or how about the multifaceted check-in process, which might not wreak havoc on liver location but nevertheless makes you wonder if you’ve been trapped in some sort of covert psychological-stress test? Another WSJ article, called “The Self-Service Airport,” says there’s reason for hope there as well: “Airlines are laying the groundwork for the next big step in the airport experience: a trip from the curb to the plane without interacting with a single airline employee. At the airport of the near future, ‘your first interaction could be with a flight attendant,’ said Ben Minicucci, chief operating officer of Alaska Airlines, a unit of Alaska Air Group Inc.” And in the topsy-turvy world of air travel, it’s not just the passengers who’ve been experiencing bumpy rides: the airlines themselves are grappling with a range of challenges—some beyond their control, some not—that make profitability increasingly elusive in spite of heavy demand for their services. A recent piece in The Economist illustrates one of the mega-challenges confronting the airline industry via a striking set of contrasting and very large numbers: while the airlines pay $7 billion per year to third-party computerized reservation services, the airlines themselves earn a collective profit of only $3 billion per year. In that context, the anecdotes above point unmistakably to the future that airlines must pursue if they hope to be able to manage some of the factors outside of their control (e.g., weather) as well as all of those within their control (operating expenses, end-to-end visibility, safety, load optimization, etc.): more intelligence, more automation, more interconnectedness, and more real-time awareness of every facet of their operations. Those moves will benefit both passengers and the air carriers, says the WSJ piece on The Self-Service Airport: “Airlines say the advanced technology will quicken the airport experience for seasoned travelers—shaving a minute or two from the checked-baggage process alone—while freeing airline employees to focus on fliers with questions. ‘It's more about throughput with the resources you have than getting rid of humans,’ said Andrew O'Connor, director of airport solutions at Geneva-based airline IT provider SITA.” Oracle’s attempting to help airlines gain control over these challenges by blending together a range of its technologies into a solution called the Oracle Airline Data Model, which suggests the following steps: • To retain and grow their customer base, airlines need to focus on the customer experience. • To personalize and differentiate the customer experience, airlines need to effectively manage their passenger data. • The Oracle Airline Data Model can help airlines jump-start their customer-experience initiatives by consolidating passenger data into a customer data hub that drives realtime business intelligence and strategic customer insight. • Oracle’s Airline Data Model brings together multiple types of data that can jumpstart your data-warehousing project with rich out-of-the-box functionality. • Oracle’s Intelligent Warehouse for Airlines brings together the powerful capabilities of Oracle Exadata and the Oracle Airline Data Model to give you real-time strategic insights into passenger demand, revenues, sales channels and your flight network. The airline industry aside, the bullet points above offer a broad strategic outline for just about any industry because the customer experience is becoming pre-eminent in each and there is simply no way to deliver world-class customer experiences unless a company can capture, manage, and analyze all of the relevant data in real-time. I’ll leave you with two thoughts from the WSJ article about the new in-flight radar system from Honeywell: first, studies show that a single episode of serious turbulence can wrack up $150,000 in additional costs for an airline—so, it certainly behooves the carriers to gain the intelligence to avoid turbulence as much as possible. And second, it’s back to that top-priority customer-experience thing and the value that ever-increasing levels of intelligence can deliver. As the article says: “In the cabin, reporters watched screens showing the most intense parts of the nearly 10-mile wide storm, which churned some 7,000 feet below, in vibrant red and other colors. The screens also were filled with tiny symbols depicting likely locations of lightning and hail, which can damage planes and wreak havoc on the nerves of white-knuckle flyers.”  (Bob Evans is senior vice-president, communications, for Oracle.)  

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• Move on and look elsewhere, or confront the boss?

  - by Meister

  Background: I have my Associates in Applied Science (Comp/Info Tech) with a strong focus in programming, and I'm taking University classes to get my Bachelors. I was recently hired at a local company to be a Software Engineer I on a team of about 8, and I've been told they're looking to hire more. This is my first job, and I was offered what I feel to be an extremely generous starting salary ($30/hr essentially + benefits and yearly bonus). What got me hired was my passion for programming and a strong set of personal projects. Problem: I had no prior experience when I interviewed, so I didn't know exactly what to ask them about the company when I was hired. I've spotted a number of warning signs and annoyances since then, such as: Four developers when I started, with everyone talking about "Ben" or "Ryan" leaving. One engineer hired thirty days before me, one hired two weeks after me. Most of the department has been hiring a large number of people since I started. Extremely limited internet access. I understand the idea from an IT point of view, but not only is Facebook blocked, but so it Youtube, Twitter, and Pandora. I've also figured out that they block all access to non-DNS websites (http://xxx.xxx.xxx.xxx/) and strangely enough Miranda-IM. Low cubicles. Which is fine because I like my immediate coworkers, but they put the developers with the customer service, customer training, and QA department in a huge open room. Noise, noise, noise, and people stop to chitchat all day long. Headphones only go so far. Several emails have been sent out by my boss since I started telling us programmers to not talk about non-work-related-things like Video Games at our cubicles, despite us only spending maybe five minutes every few hours doing so. Further digging tells me that this is because someone keeps complaining that the programmers are "slacking off". People are looking over my shoulder all day. I was in the Freenode webchat to get help with a programming issue, and within minutes I had an email from my boss (to all the developers) telling us that we should NOT be connected to any outside chat servers at work. Version control system from 2005 that we must access with IE and keep the Java 1.4 JRE installed to be able to use. I accidentally updated to Java 6 one day and spent the next two days fighting with my PC to undo this "problem". No source control, no comments on anything, no standards, no code review, no unit testing, no common sense. I literally found a problem in how they handle string resource translations that stems from the simple fact that they don't trim excess white spaces, leading to developers doing: getResource("Date: ") instead of: getResource("Date") + ": ", and I was told to just add the excess white spaces back to the database instead of dealing with the issue directly. Some of these things I'd like to try to understand, but I like having IRC open to talk in a few different rooms during the day and keep in touch with friends/family over IM. They don't break my concentration (not NEARLY as much as the lady from QA stopping by to talk about her son), but because people are looking over my shoulder all day as they walk by they complain when they see something that's not "programmer-looking work". I've been told by my boss and QA that I do good, fast work. I should be judged on my work output and quality, not what I have up on my screen for the five seconds you're walking by So, my question is, even though I'm just barely at my 90 days: How do you decide to move on from a job and looking elsewhere, or when you should start working with your boss to resolve these issues? Is it even possible to get the boss to work with me in many of these things? This is the only place I heard back from even though I sent out several resume's a day for several months, and this place does pay well for putting up with their many flaws, but I'm just starting to get so miserable working here already. Should I just put up with it?

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• Library order is important

  - by Darryl Gove

  I've written quite extensively about link ordering issues, but I've not discussed the interaction between archive libraries and shared libraries. So let's take a simple program that calls a maths library function: #include <math.h int main() { for (int i=0; i<10000000; i++) { sin(i); } } We compile and run it to get the following performance: bash-3.2$ cc -g -O fp.c -lm bash-3.2$ timex ./a.out real 6.06 user 6.04 sys 0.01 Now most people will have heard of the optimised maths library which is added by the flag -xlibmopt. This contains optimised versions of key mathematical functions, in this instance, using the library doubles performance: bash-3.2$ cc -g -O -xlibmopt fp.c -lm bash-3.2$ timex ./a.out real 2.70 user 2.69 sys 0.00 The optimised maths library is provided as an archive library (libmopt.a), and the driver adds it to the link line just before the maths library - this causes the linker to pick the definitions provided by the static library in preference to those provided by libm. We can see the processing by asking the compiler to print out the link line: bash-3.2$ cc -### -g -O -xlibmopt fp.c -lm /usr/ccs/bin/ld ... fp.o -lmopt -lm -o a.out... The flag to the linker is -lmopt, and this is placed before the -lm flag. So what happens when the -lm flag is in the wrong place on the command line: bash-3.2$ cc -g -O -xlibmopt -lm fp.c bash-3.2$ timex ./a.out real 6.02 user 6.01 sys 0.01 If the -lm flag is before the source file (or object file for that matter), we get the slower performance from the system maths library. Why's that? If we look at the link line we can see the following ordering: /usr/ccs/bin/ld ... -lmopt -lm fp.o -o a.out So the optimised maths library is still placed before the system maths library, but the object file is placed afterwards. This would be ok if the optimised maths library were a shared library, but it is not - instead it's an archive library, and archive library processing is different - as described in the linker and library guide: "The link-editor searches an archive only to resolve undefined or tentative external references that have previously been encountered." An archive library can only be used resolve symbols that are outstanding at that point in the link processing. When fp.o is placed before the libmopt.a archive library, then the linker has an unresolved symbol defined in fp.o, and it will search the archive library to resolve that symbol. If the archive library is placed before fp.o then there are no unresolved symbols at that point, and so the linker doesn't need to use the archive library. This is why libmopt needs to be placed after the object files on the link line. On the other hand if the linker has observed any shared libraries, then at any point these are checked for any unresolved symbols. The consequence of this is that once the linker "sees" libm it will resolve any symbols it can to that library, and it will not check the archive library to resolve them. This is why libmopt needs to be placed before libm on the link line. This leads to the following order for placing files on the link line: Object files Archive libraries Shared libraries If you use this order, then things will consistently get resolved to the archive libraries rather than to the shared libaries.

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• Dont Throw Duplicate Exceptions

  In your code, youll sometimes have write code that validates input using a variety of checks.  Assuming you havent embraced AOP and done everything with attributes, its likely that your defensive coding is going to look something like this: public void Foo(SomeClass someArgument) { if(someArgument == null) { throw new InvalidArgumentException("someArgument"); } if(!someArgument.IsValid()) { throw new InvalidArgumentException("someArgument"); }   // Do Real Work } Do you see a problem here?  Heres the deal Exceptions should be meaningful.  They have value at a number of levels: In the code, throwing an exception lets the develop know that there is an unsupported condition here In calling code, different types of exceptions may be handled differently At runtime, logging of exceptions provides a valuable diagnostic tool Its this last reason I want to focus on.  If you find yourself literally throwing the exact exception in more than one location within a given method, stop.  The stack trace for such an exception is likely going to be identical regardless of which path of execution led to the exception being thrown.  When that happens, you or whomever is debugging the problem will have to guess which exception was thrown.  Guessing is a great way to introduce additional problems and/or greatly increase the amount of time require to properly diagnose and correct any bugs related to this behavior. Dont Guess Be Specific When throwing an exception from multiple code paths within the code, be specific.  Virtually ever exception allows a custom message use it and ensure each case is unique.  If the exception might be handled differently by the caller, than consider implementing a new custom exception type.  Also, dont automatically think that you can improve the code by collapsing the if-then logic into a single call with short-circuiting (e.g. if(x == null || !x.IsValid()) ) that will guarantee that you cant easily throw different information into the message as easily as constructing the exception separately in each case. The code above might be refactored like so:   public void Foo(SomeClass someArgument) { if(someArgument == null) { throw new ArgumentNullException("someArgument"); } if(!someArgument.IsValid()) { throw new InvalidArgumentException("someArgument"); }   // Do Real Work } In this case its taking advantage of the fact that there is already an ArgumentNullException in the framework, but if you didnt have an IsValid() method and were doing validation on your own, it might look like this: public void Foo(SomeClass someArgument) { if(someArgument.Quantity < 0) { throw new InvalidArgumentException("someArgument", "Quantity cannot be less than 0. Quantity: " + someArgument.Quantity); } if(someArgument.Quantity > 100) { throw new InvalidArgumentException("someArgument", "SomeArgument.Quantity cannot exceed 100. Quantity: " + someArgument.Quantity); }   // Do Real Work }   Note that in this last example, Im throwing the same exception type in each case, but with different Message values.  Im also making sure to include the value that resulted in the exception, as this can be extremely useful for debugging.  (How many times have you wished NullReferenceException would tell you the name of the variable it was trying to reference?) Dont add work to those who will follow after you to maintain your application (especially since its likely to be you).  Be specific with your exception messages follow DRY when throwing exceptions within a given method by throwing unique exceptions for each interesting case of invalid state. 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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• Software and/(x)or Hardware Projects for Pre-School Kids

  - by haylem

  I offered to participate at my kid's pre-school for various activities (yes, I'm crazy like that), and one of them is to help them discover extra-curricular (big word for a pre-school, but by lack of a better one... :)) hobbies, which may or may not relate to a professional activity. At first I thought that it wouldn't be really easy to have pre-schoolers relate to programming or the internal workings of a computer system in general (and I'm more used to teaching middle-school to university-level students), but then I thought there must be a way. So I'm trying to figure out ways to introduce very young kids (3yo) to computer systems in a fun and preferably educational way. Of course, I don't expect them to start smashing the stack for fun and profit right away (or at least not voluntarily, though I could use the occasion for some toddler tests...), but I'm confident there must be ways to get them interested in both: using the systems, becoming curious about understanding what they do, interacting with the systems to modify them. I guess this setting is not really relevant after all, it's pretty much the same as if you were aiming to achieve the same for your own kids at home. Ideas Considering we're talking 3yo pre-schoolers here, and that at this age some kids are already quite confident using a mouse (some even a keyboard, if not for typing, at least to press some buttons they've come to associate with actions) while others have not yet had any interaction with computers of any kind, it needs to be: rather basic, demonstrated and played with in less then 5 or 10 minutes, doable in in groups or alone, scalable and extendable in complexity to accommodate their varying abilities. The obvious options are: basic smallish games to play with, interactive systems like LOGO, Kojo, Squeak and clones (possibly even simpler than that), or thngs like Lego Systems. I guess it can be a thing to reflect on both at the software and the hardware levels: it could be done with a desktop or laptop machine, a tablet, a smartphone (or a crap-phone, for that matter, as long as you can modify it), or even get down to building something from scratch (Raspberry Pi and Arduino being popular options at the moment). I can probably be in the form of games, funny visualizations (which are pretty much games) w/ Prototype, virtual worlds to explore. I also thought on the moment (and I hope this won't offend anyone) that some approaches to teaching pets could work (reward systems, haptic feedback and such things could quickly point a kid in the right direction to understanding how things work, in a similar fashion - I'm not suggesting to shock the kids!). Hmm, Is There an Actual Question in There? What type of systems do you think might be a good fit, both in terms of hardware and software? Do you have seen such systems, or have anything in mind to work on? Are you aware of some research in this domain, with tangible results? Any input is welcome. It's not that I don't see options: there are tons, but I have a harder time pinpointing a more concrete and definite type of project/activity, so I figure some have valuable ideas or existing ones. Note: I am not advocating that every kid should learn to program, be interested in computer systems, or that all of them in a class would even care enough to follow such an introduction with more than a blank stare. I don't buy into the "everybody would benefit from learning to program" thing. Wouldn't hurt, but not necessary in any way. But if I can walk out of there with a few of them having smiled using the thing (or heck, cried because others took them away from them), that'd be good enough. Related Questions I've seen and that seem to complement what I'm looking for, but not exactly for the same age groups or with the same goals: Teaching Programming to Kids Recommendations for teaching kids math concepts & skills for programming?

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• What do you need to know to be a world-class master software developer? [closed]

  - by glitch

  I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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• Concurrent Affairs

  - by Tony Davis

  I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

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• ????????????????

  - by Yusuke.Yamamoto

  ????????? ????????? ????????? ????·???? ?????:Oracle???????·??????(????)??:?????????????? Pickup!:IT???????????!|????????:100???????!|???????????? ????????:?Oracle DB?????????????????????Windows?VMware?? ?????:Oracle OpenWorld Tokyo 2012|JavaOne Tokyo 2012|??????:151 ?OTN ???? ?????? ????????:???????100???????! ?????????????????Amazon????Get! ???? Oracle Technology Network, ????/????, ??IT???????·?????????????? ???????/???MySQL?????? ?????? ???????/???MySQL????? ?????????Oracle VM VirtualBox????Oracle Real Application Clusters (RAC) 11g Release 2????? ???????/??????????????????????????????? ???????/?????????????/????·????????Flashback Database with SSD? ????? ????? Oracle?????????????????????????!???????????? Oracle Enterprise Manager 12c(EM12c):????????? ~????????~ ???????????!??????·??????? Oracle Linux 5.8?????????? ???DB?????Oracle SQL Developer 3.1???????????? Oracle??????(OUI:Oracle Universal Installer)???? ????? ???? ????????? ????????????·???????? ????????????? ???????? 11gR2 ?????????? Oracle Database 11g R2 Oracle WebLogic Server 11g R1 Oracle Enterprise Manager 11g R1 ????? ????????? Oracle Database ????????????????·?? ???????/???????????????? ?????????(????????, ???, etc) ????????(???, ?????, REDO, ???·????, etc) ????·?????????????????(?????, ???, ??, ??, ??? etc) ????·?????????(??, etc) ????????????? ???????????????????·?????? ??????? ???? ????????·??|SQL Server Windows Server ??????????PL/SQL|Java|.NET|PHP ??/??? ORACLE MASTER ???? DWH(?????????)??·?? ????? ?????(SAN, NAS, SSD, etc) Oracle Database ??????? Amazon EC2 Microsoft Excel Microsoft Visual Studio MSFC/MSCS(Microsoft Cluster Service) SAP ??·??????? Oracle Database Oracle Database 11g Release 2(11gR2) Oracle Database Standard Edition ????????: Advanced Compression ?????????: Advanced Security Application Express(APEX) Automatic Storage Management(ASM) SSD???Oracle???: Database Smart Flash Cache ??????????: Data Guard/Active Data Guard Data Pump Oracle Data Provider for .NET(ODP.NET) ????: Oracle Text Partitioning(???????/?????????) DB????: Real Application Clusters(RAC) Real Application Testing Recovery Manager(RMAN) SQL*Loader|SQL*Plus|Statspack ??????|????????|???????? Database Appliance Database Firewall Exadata Database Machine SQL Developer ?????DB: TimesTen In-Memory Database Oracle Fusion Middleware Java Oracle Coherence Oracle Data Integrator(ODI) Oracle GoldenGate Oracle JRockit JVM Oracle WebLogic Server Oracle Enterprise Manager for Database|for Middleware ????????????: Oracle Application Testing Suite Oracle Linux Oracle Solaris DTrace|ZFS|???/???? Oracle VM Server for x86 ?????? ???????? ?????????Oracle???????????????·????????????????? ?????????(??·??????) OTN??????(??????) ???????(????????) Oracle University(??) ??????! ?????... ????? ?????? ????? ?????? ?????|?Sun?? ???????? OTN???????? OTN(????) ?????? ???? OTN???|???? OTN?????? ??????? ?????? ???????? ???? ???????

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• CodePlex Daily Summary for Friday, March 09, 2012

  CodePlex Daily Summary for Friday, March 09, 2012Popular ReleasesSSH.NET Library: 2012.3.9: There are still few outstanding issues I wanted to include in this release but since its been a while and there are few new features already I decided to create a new release now. New Features Add SOCKS4, SOCKS5 and HTTP Proxy support when connecting to remote server. For silverlight only IP address can be used for server address when using proxy. Add dynamic port forwarding support using ForwardedPortDynamic class. Add new ShellStream class to work with SSH Shell. Add supports for mu...fnr.exe - Find And Replace Tool: 1.0: You can read all about the new features here: Here is the Summary Preview Matches Stats File errors for read/write Support for regular expressions Fixed a bug that required you to press enter to continue after running fnr.exe from command line Context menu to display containing folder or open the file Double click on results row to open the file (similar to double clicking in windows explorer) Binary detection – skip files that are binaryTest Case Import Utilities for Visual Studio 2010 and Visual Studio 11 Beta: V1.2 RTM: This release (V1.2 RTM) includes: Support for connecting to Hosted Team Foundation Server Preview. Support for connecting to Team Foundation Server 11 Beta. Fix to issue with read-only attribute being set for LinksMapping-ReportFile which may have led to problems when saving the report file. Fix to issue with “related links” not being set properly in certain conditions. Fix to ensure that tool works fine when the Excel file contained rich text data. Note: Data is still imported in pl...Audio Pitch & Shift: Audio Pitch And Shift 3.5.0: Modules (mod, xm, it, etc..) supportcallisto: callisto 2.0.19: BUG FIX: Autorun.load() function in scripting now has sandboxed path (Thanks Mikey!) BUG FIX: UserObject.Name property now allows full 20 byte string replacements. FEATURE REQUEST: File.* script functions now allow file extensions.DotNetNuke® Community Edition CMS: 06.01.04: Major Highlights Fixed issue with loading the splash page skin in the login, privacy and terms of use pages Fixed issue when searching for words with special characters in them Fixed redirection issue when the user does not have permissions to access a resource Fixed issue when clearing the cache using the ClearHostCache() function Fixed issue when displaying the site structure in the link to page feature Fixed issue when inline editing the title of modules Fixed issue with ...Mayhem: Mayhem Developer Preview: This is the developer preview of Mayhem. Enjoy!Magelia WebStore Open-source Ecommerce software: Magelia WebStore 1.2: Medium trust compliant lot of small change for medium trust compliance full refactoring of user management refactoring of Client Refactoring of user management Magelia.WebStore.Client no longer reference Magelia.WebStore.Services.Contract Refactoring page category multi parent category added copy category feature added Refactoring page catalog copy catalog feature added variant management improvement ability to define a default variant for a variable product ability to ord...Delta Engine: Delta Engine Beta Preview v0.9.4: v0.9.4 is the release for February 2012, but it was delayed till 2012-03-07 until content generation worked much better for v0.9.4. The main improvements were done on the server side (content generation and improved build support for iOS and Android). v0.9.4 is also the first version everyone can use to deploy their application onto all supported platforms, see Marketplace Licensing for details: http://deltaengine.net/Marketplace Documentation for this version can be found at: http://help.de...PDFsharp - A .NET library for processing PDF: PDFsharp and MigraDoc Foundation 1.32: PDFsharp and MigraDoc Foundation 1.32 is a stable version that fixes a few bugs that were found with version 1.31. Version 1.32 includes solutions for Visual Studio 2010 only (but it should be possible to add the project files to existing solutions for VS 2005 or VS 2008). Users of VS 2005 or VS 2008 can still download version 1.31 with the solutions for those versions that allow them to easily try the samples that are included. While it may create smaller PDF files than version 1.30 because...Terminals: Version 2.0 - Release: Changes since version 1.9a:New art works New usability in Organize favorites window Improved usability of imports/exports and scans Large number of fixes Improvements in single instance mode Comparing November beta 4, this corrects: New application icons Doesn't show Logon error codes Fixed command line arguments exception for single instance mode Fixed detaching of tabs improved usability in detached window Fixed option settings for Capture manager Fixed system tray noti...AutoLoL: AutoLoL v2.1.5: Updated version of Autolol that works with the Fiora patch.MFCMAPI: March 2012 Release: Build: 15.0.0.1032 Full release notes at SGriffin's blog. If you just want to run the MFCMAPI or MrMAPI, get the executables. If you want to debug them, get the symbol files and the source. The 64 bit builds will only work on a machine with Outlook 2010 64 bit installed. All other machines should use the 32 bit builds, regardless of the operating system. Facebook BadgeSimple Injector: Simple Injector v1.4.1: This release adds two small improvements to the SimpleInjector.Extensions.dll. No changes have been made to the core library. New features and improvements in this release for the SimpleInjector.Extensions.dll The RegisterManyForOpenGeneric extension methods now accept non-generic decorator, as long as they implement the given open generic service type. GetTypesToRegister methods added to the OpenGenericBatchRegistrationExtensions class which allows to customize the behavior. Note that the...SQL Scriptz Runner: Application: Scriptz Runner source code and applicationPowerGUI Visual Studio Extension: PowerGUI VSX 1.5.2: Added support for PowerGUI 3.2.VidCoder: 1.3.1: Updated HandBrake core to 0.9.6 release (svn 4472). Removed erroneous "None" container choice. Change some logic and help text to stop assuming you have to pick the VIDEO_TS folder for a DVD scan. This should make previewing DVD titles on the Queue Multiple Titles window possible when you've picked the root DVD directory.Google Books Downloader for Windows: Google Books Downloader: Google Books Downloader 1.8ExtAspNet: ExtAspNet v3.1.0: ExtAspNet - ?? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ?????????? ExtAspNet ????? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ??????????。 ExtAspNet ??????? JavaScript，?? CSS，?? UpdatePanel，?? ViewState，?? WebServices ???????。 ??????: IE 7.0, Firefox 3.6, Chrome 3.0, Opera 10.5, Safari 3.0+ ????：Apache License 2.0 (Apache) ??：http://extasp.net/ ??：http://bbs.extasp.net/ ??：http://extaspnet.codeplex.com/ ??：http://sanshi.cnblogs.com/ ????： +2012-03-04 v3.1.0 -??Hidden???????（〓?〓）。 -?PageManager??...AcDown????? - Anime&Comic Downloader: AcDown????? v3.9.1: ?? ●AcDown??????????、??、??????，????1M，????，????，?????????????????????????。???????????Acfun、????(Bilibili)、??、??、YouTube、??、???、??????、SF????、????????????。??????AcPlay?????，??????、????????????????。 ● AcDown???????????????????????????，???，???????????????????。 ● AcDown???????C#??，????.NET Framework 2.0??。?????"Acfun?????"。 ????32??64? Windows XP/Vista/7/8 ????????????? ??：????????Windows XP???,?????????.NET Framework 2.0???(x86)，?????"?????????"??? ??????????????，??????????： ??"AcDo...New ProjectsAngry Birds in 1 Hour: This is a simple "Angry Birds" clone on Windows Phone 7 written in just 1 hour.ascent: ascent capture a capture productascentexpress: ascentexpressASP.NET MVVM Excalibur: ASP.NET MVVM Excalibur Project.this is Web Form base, has a new Binding Expression like WPF MVVM.Azure Virtual Directory: A program (or windows service) that registers a virtual directory on your local machine that is actually a gateway into an Azure Blob service. This will allow you to browse, create, modify and delete files directly in Windows Explorer, through a command prompt, or by any software that would be able to do so (as if it was writing to the local machine). This is not a directory that backs-up to Azure, but is rather *only* on Azure. Developed in C#.ClipFlair: ClipFlair - Foreign Language Learning through Interactive Revoicing and Captioning of ClipsCloudSpotter: CloudSpotter is a Windows Azure sample application that can be used for demo purposes or for learning the basic concepts of cloud application development. CloudSpotter makes it possible to convert, webcam based, cloud pictures to time-lapse video footage. Composing Wcf: Basic library providing a service host and service behavior capable of utilizing MEF for runtime composition of WCF SOAP and REST web services. Library provides composing Hosts and Host Factories for standard ServiceHost types, as well as WebServiceHost (RESTful).convert digit to word upto thousand: convert digit to word upto thousandDAL Generator using Database Application Block 5 and T4 Template: T4 template code for generating data base layer for normal CRUD operation using Repository Pattern. Database application block 5 features are used for generating database call and automatic mapping with DTOeuler 12 problem: euler 12 problemeuler 14 problem: euler 14 problemeuler 19 problem: euler 19 problemeuler 28: euler 28euler 30: euler 30euler 36 problem: euler 36 problemeuler 45: euler 45 problemeuler 52 problem: euler 52 problemeuler21: euler 21euler22: euler 22 problemeuler23: euler 23euler29: euler 29 problemeVet: eVet is a guidance project based on the fictional scenario of a Veterinary System used to monitor pets' medical history. It will be based on Azure and leverage the Worker role and SQL Azure datase to illustrate a multi-tenant cloud-based Pet management system. The ORM layer will be NHibernate and it will be based on the repository design pattern. If you want to help and learn Azure at the same time, I am looking for: - Designers (CSS3, HTML 5, Javascript) - Web Developers (ASP.Net ...Firemap: Generates a html page which displays key performance statistics of chosen computers. FolderHiderNet: FolderHiderNet, its a simple application developed in C#, that let users easily hide and unhide folder on their windows systems. It could be used in USB dispositives.Game of Life for Windows Phone: This is an XNA implementation of Conway's Game of Life for Windows Phone. The game is a grid of cells that live and die based on a simple set of rules. The player can arrange the live and dead cells, and start/stop the cell generation to see how the cells are interrelated. Features: - Save and load games - Start and stop generations - Adjust generation speed - Clear grid - Generate random grid - Sample shapes preloaded as saved games For more information on Conway's Game of Life...Gamoliyas: Gamoliyas is an open source John Conway's Game of Life game totally written in DHTML (JavaScript, CSS and HTML). Uses mouse and keyboard. Very configurable. This cross-platform and cross-browser game was tested under BeOS, Linux, *BSD, Windows and others.Gembed: Transform url into Embed code using javascript. It is developed using jQuery, jQuery templates and javascript. Any contribution would be really apreciated.GIFT: gift appImageLoader iOS: ImageLoader is developed on iOS and it can be used in iPhone and iPad. It try to make application to support image downloading and cache easily. It downloads the image file from url, depended on ASIHttpRequest. And it cache the images into local file.MakkysStackOverflow: Learning how to build stackoverflow like site mysimpleproject: This is my test projectNWN Hak Merging Utility: Mostly automated Hak Merging utility for NWN .hak files.Oasis Text: Oasis Text is a simple, free text editor for Windows. It is written in C# and built with the ScintillaNET editing component. It is a work in progress and is free and open source software. Opds4Net: A .NET Library for Open Publication Distribution System (OPDS) Catalog protocol, a syndication format for electronic publications based on Atom. This project is created to simplify the process of creating an OPDS Catalog in .NET and standardize the result OPDS with least effort. Pratiques: Endroit pour gérer les Pratiques.scooby: This is a scooby dooby doo projectStaffKey: Study Project Projet d'étude Permet le lancement d'un serveur web sur une clé usb.SugataTools: SugataTools are the helper classes that I usually use in my projects.testtom03082012hg05: testtom03082012hg05testtom03082012tfs01: testtom03082012tfs01testtom03082012tfs02: testtom03082012tfs02TNTSerializer: A simple serializer which -Is faster than any other serializer -Does not require ISeriablable - Uses generic cached Reflection wrappers (FAST) -Should serialize ANY structure, no questions asked, no special markup required. -Can handle common attributes -handles optional parameteWholemy.LinkedLists: Wholemy Linked Lists realizationsworkApp: workAppWPF Yahoo Stock API: WPF application using PRISM & MVVM to display stock details using Yahoo API (YPL)

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• Android: trouble updating to Android SDK Tools, revision 7.

  - by Arhimed

  Currently I have Android SDK 2.1 (+ tools revision 4). I'd like to upgrade to Android SDK 2.2. When I try to do it I'm informed I need to upgrade Android SDK Tools to revision 7 first. So I agree, the process starts and then I get an error: -= warning! =- A folder failed to be renamed or moved. On Windows this typically means that a program Is using that Folder (for example Windows Explorer or your anti-virus software.) Please momentarily deactivate your anti-virus software. Please also close any running programs that may be accessing the directory 'D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\too!s'. When ready, press YES to try again. Downloading Android SDK Tools, revision 7 Installing Android SDK Tools, revision 7 Failed to rename directory D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\tools to D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\temp\ToolPackage.old01. I am aware of http/https and antivirus issues. So I disactivated my AV. I also closed any application that might hold a handle to the folder. Eclipse is also closed (I start the manager via command line). However I still get the same error. Looks like the only app that can hold a handle to the folder is the manager itself, because its starting directory is the one the error complains about ('\tools'). I am on Win XP Pro + SP3. Does anyone have an idea?

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• Newbie, deciding Python or Erlang

  - by Joe

  Hi Guys, I'm a Administrator (unix, Linux and some windows apps such as Exchange) by experience and have never worked on any programming language besides C# and scripting on Bash and lately on powershell. I'm starting out as a service provider and using multiple network/server monitoring tools based on open source (nagios, opennms etc) in order to monitor them. At this moment, being inspired by a design that I came up with, to do more than what is available with the open source at this time, I would like to start programming and test some of these ideas. The requirement is that a server software that captures a stream of data and store them in a database(CouchDB or MongoDB preferably) and the client side (agent installed on a server) would be sending this stream of data on a schedule of every 10 minutes or so. For these two core ideas, I have been reading about Python and Erlang besides ruby. I do plan to use either Amazon or Rackspace where the server platform would run. This gives me the scalability needed when we have more customers with many servers. For that reason alone, I thought Erlang was a better fit(I could be totally wrong, new to this game) and I understand that Erlang has limited support in some ways compared to Ruby or Python. But also I'm totally new to the programming realm of things and any advise would be appreciated grately. Jo

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• Accessing Yahoo realtime stock quotes

  - by DVK

  There's a fairly easy way of retrieving 15-minute delayed quotes off of Yahoo! Finance web site ("quotes.csv" API). However, so far I was unable to find any info on how to access real-time quotes. The hang-ups with real-time quotes are: Only available to logged-in user No API Non-obvious how to scrape the info - I'm somewhat convinced they are placed on the page by some weird Ajax call. So I was wondering if anyone had managed to develop a publically available solution to retrieve real-time quotes for a stock from Yahoo! Finance. Notes: Implementation language/framework need is flexible but Perl or Excel is highly preferred. Assume that security is not an issue - I'm willing to supply yahoo userid and pasword, even in cleartext. I'm not 100% hung up on Yahoo - they are merely the only provider of free realtime stock quotes I'm familiar with. if the same thing can be done with Google Finance, I'd be just as happy. This is for a personal project, so scalability/fault tolerance/etc... are not important. I'm looking for a "do the whole retrieval" library ideally, but if I'm pointed to partial solutions (e.g. how to retrieve info from Yahoo's user-logged-in pages; how to scrape realtime quotes from Yahoo's page) I can fill in the blanks. I saw Finance::YahooQuote but it does not seem to allow you to supply log-in information and appears to use the lagging quotes.csv API Thanks!

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• Status of VB6/ Best Desktop Application Language with Native Compilation

  - by Sandeep Jindal

  I was looking for a Desktop Application Programming Language with one of the biggest constraint: - “I need to output as native executable”. I explored multiple options: Java is not a very good option for desktop programming, but still you can use it. But Java to Exe is a problem. Only GCJ and Excelsior-Jet provides this. .Net platform does not support native compilation. Only very few expensive tools are available which can do the job. Python is not an option for native compilation. Right? VB6 is the option I am left with. From the above list, if I am correct, VB6 is the only and probably the best option I have. But VB6 itself has issues like: It is no more under development since There are questions on support of VB6 IDE with Vista Thus my questions are: From the list of programming language options, do you want to add any more? If VB6 is good/best option, looking at its development status, would you suggest using VB6 in this era?

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• Python PyQt Timer Firmata

  - by George Cullins

  Hello. I am pretty new to python and working with firmata I am trying to play around with an arduino . Here is what I want to happen: Set arduino up with an LED as a digital out Set potentiometer to analog 0 Set PyQt timer up to update potentiometer position in application Set a threshold in PyQt to turn LED on (Analog in has 1024bit resolution, so say 800 as the threshold) I am using this firmata library : Link Here is the code that I am having trouble with: import sys from PyQt4 import QtCore, QtGui from firmata import * # Arduino setup self.a = Arduino('COM3') self.a.pin_mode(13, firmata.OUTPUT) # Create timer self.appTimer = QtCore.QTimer(self) self.appTimer.start(100) self.appTimer.event(self.updateAppTimer()) def updateAppTimer(self): self.analogPosition = self.a.analog_read(self, 0) self.ui.lblPositionValue.setNum() I am getting the error message: Traceback (most recent call last): File "D:\Programming\Eclipse\IO Demo\src\control.py", line 138, in myapp = MainWindow() File "D:\Programming\Eclipse\IO Demo\src\control.py", line 56, in init self.appTimer.event(self.updateAppTimer()) File "D:\Programming\Eclipse\IO Demo\src\control.py", line 60, in updateAppTimer self.analogPosition = self.a.analog_read(self, 0) TypeError: analog_read() takes exactly 2 arguments (3 given) If I take 'self' out I get the same error message but that only 1 argument is given What is python doing implicitly that I am not aware of? Blockquote

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• JVM CMS Garbage Collecting Issues

  - by jlintz

  I'm seeing the following symptoms on an application's GC log file with the Concurrent Mark-Sweep collector: 4031.248: [CMS-concurrent-preclean-start] 4031.250: [CMS-concurrent-preclean: 0.002/0.002 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 4031.250: [CMS-concurrent-abortable-preclean-start] CMS: abort preclean due to time 4036.346: [CMS-concurrent-abortable-preclean: 0.159/5.096 secs] [Times: user=0.00 sys=0.01, real=5.09 secs] 4036.346: [GC[YG occupancy: 55964 K (118016 K)]4036.347: [Rescan (parallel) , 0.0641200 secs]4036.411: [weak refs processing, 0.0001300 secs]4036.411: [class unloading, 0.0041590 secs]4036.415: [scrub symbol & string tables, 0.0053220 secs] [1 CMS-remark: 16015K(393216K)] 71979K(511232K), 0.0746640 secs] [Times: user=0.08 sys=0.00, real=0.08 secs] The preclean process keeps aborting continously. I've tried adjusting CMSMaxAbortablePrecleanTime to 15 seconds, from the default of 5, but that has not helped. The current JVM options are as follows... Djava.awt.headless=true -Xms512m -Xmx512m -Xmn128m -XX:MaxPermSize=128m -XX:+HeapDumpOnOutOfMemoryError -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:BiasedLockingStartupDelay=0 -XX:+DoEscapeAnalysis -XX:+UseBiasedLocking -XX:+EliminateLocks -XX:+CMSParallelRemarkEnabled -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintHeapAtGC -Xloggc:gc.log -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenPrecleaningEnabled -XX:CMSInitiatingOccupancyFraction=50 -XX:ReservedCodeCacheSize=64m -Dnetworkaddress.cache.ttl=30 -Xss128k It appears the concurrent-abortable-preclean never gets a chance to run. I read through http://blogs.sun.com/jonthecollector/entry/did_you_know which had a suggestion of enabling CMSScavengeBeforeRemark, but the side effects of pausing did not seem ideal. Could anyone offer up any suggestions? Also I was wondering if anyone had a good reference for grokking the CMS GC logs, in particular this line: [1 CMS-remark: 16015K(393216K)] 71979K(511232K), 0.0746640 secs] Not clear on what memory regions those numbers are referring to.

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• Decisions in teaching someone else to program: language selection

  - by Dinah

  My friend would like for me to guide her into learning programming. She's already proven enormous aptitude for thinking like a programmer but is scared of the idea of programming since in her mind it's relegated to some magical realm accessible only to smart people and trained computer scientists (ironically, I am neither but that's beside the point). My main question is the age-old and irritating question: which language should I chose? I've limited it down to these: PHP: dead simple to start with and I remember enough of the language to answer all novice questions. However, I can think of a million reasons why I wouldn't recommend this as a first language. The most diplomatic of which is that there's no desktop app option to which I would feel comfortable subjecting a novice. Python: supposed to be wonderful for beginners and generally everything I've heard about it screams that this is the correct choice. That's the problem: everything I've heard about it. I don't know it yet and have a lot of projects going on right now so I don't feel like learning it yet -- but I'm going to be the tech-support when any little thing goes wrong. I know there are tons of online resources but in the frustration of the moment, it's always going to be just me. C#: this is the language I'm most comfortable with so I know I can be good tech support. I also love this language and its versatility and community. The big drawback here is that I remember when I first learned it after doing mainly PHP, Perl, and JavaScript and I found the experience overwhelming. You are simultaneously learning: programming concepts, C# syntax, strong typing, OOP, and a complex powerful IDE with a bazillion options and buttons all over it.

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• What is the best "forgot my password" method?

  - by Edward Tanguay

  I'm programming a community website. I want to build a "forgot my password" feature. Looking around at different sites, I've found they employ one of three options: send the user an email with a link to a unique, hidden URL that allows him to change his password (Gmail and Amazon) send the user an email with a new, randomly generated password (Wordpress) send the user his current password (www.teach12.com) Option #3 seems the most convenient to the user but since I save passwords as an MD5 hash, I don't see how option #3 would be available to me since MD5 is irreversible. This also seems to be insecure option since it means that the website must be saving the password in clear text somewhere, and at the least the clear-text password is being sent over insecure e-mail to the user. Or am I missing something here? So if I can't do option #1, option #2 seems to be the simplest to program since I just have to change the user's password and send it to him. Although this is somewhat insecure since you have to have a live password being communicated via insecure e-mail. However, this could also be misused by trouble-makers to pester users by typing in random e-mails and constantly changing passwords of various users. Option #1 seems to be the most secure but requires a little extra programming to deal with a hidden URL that expires etc., but it seems to be what the big sites use. What experience have you had using/programming these various options? Are there any options I've missed?

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• Attempting my first fortran 95 program, to solve quadratic eqn. Getting weird errors.

  - by Damon

  So, I'm attempting my first program in Fortran, trying to solve quadratic eqn. I have double and triple checked my code and don't see anything wrong. I keep getting "Invalid character in name at (1)" and "Unclassifiable statement at (1)" at various locations. Any help would be greatly appreciated... ! This program solves quadratic equations ! of the form ax^2 + bx + c = 0. ! Record: ! Name: Date: Notes: ! Damon Robles 4/3/10 Original Code PROGRAM quad_solv IMPLICIT NONE ! Variables REAL :: a, b, c REAL :: discrim, root1, root2, COMPLEX :: comp1, comp2 CHARACTER(len=1) :: correct ! Prompt user for coefficients. WRITE(*,*) "This program solves quadratic equations " WRITE(*,*) "of the form ax^2 + bx + c = 0. " WRITE(*,*) "Please enter the coefficients a, b, and " WRITE(*,*) "c, separated by commas:" READ(*,*) a, b, c WRITE(*,*) "Is this correct: a = ", a, " b = ", b WRITE(*,*) " c = ", c, " [Y/N]? " READ(*,*) correct IF correct = N STOP IF correct = Y THEN ! Definition discrim = b**2 - 4*a*c ! Calculations IF discrim > 0 THEN root1 = (-b + sqrt(discrim))/(2*a) root2 = (-b - sqrt(discrim))/(2*a) WRITE(*,*) "This equation has two real roots. " WRITE(*,*) "x1 = ", root1 WRITE(*,*) "x2 = ", root2 IF discrim = 0 THEN root1 = -b/(2*a) WRITE(*,*) "This equation has a double root. " WRITE(*,*) "x1 = ", root1 IF discrim < 0 THEN comp1 = (-b + sqrt(discrim))/(2*a) comp2 = (-b - sqrt(discrim))/(2*a) WRITE(*,*) "x1 = ", comp1 WRITE(*,*) "x2 = ", comp2 PROGRAM END quad_solv Thanks in advance!

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• slicing a 2d numpy array

  - by MedicalMath

  The following code: import numpy as p myarr=[[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6]] copy=p.array(myarr) p.mean(copy)[:,1] Is generating the following error message: Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> p.mean(copy)[:,1] IndexError: 0-d arrays can only use a single () or a list of newaxes (and a single ...) as an index I looked up the syntax at this link and I seem to be using the correct syntax to slice. However, when I type copy[:,1] into the Python shell, it gives me the following output, which is clearly wrong, and is probably what is throwing the error: array([1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6]) Can anyone show me how to fix my code so that I can extract the second column and then take the mean of the second column as intended in the original code above? EDIT: Thank you for your solutions. However, my posting was an oversimplification of my real problem. I used your solutions in my real code, and got a new error. Here is my real code with one of your solutions that I tried: filteredSignalArray=p.array(filteredSignalArray) logical=p.logical_and(EndTime-10.0<=matchingTimeArray,matchingTimeArray<=EndTime) finalStageTime=matchingTimeArray.compress(logical) finalStageFiltered=filteredSignalArray.compress(logical) for j in range(len(finalStageTime)): if j == 0: outputArray=[[finalStageTime[j],finalStageFiltered[j]]] else: outputArray+=[[finalStageTime[j],finalStageFiltered[j]]] print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() And here is the error message that is now being generated by the new code: File "mypath\myscript.py", line 1545, in WriteToOutput10SecondsBeforeTimeMarker print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() TypeError: list indices must be integers, not tuple Second EDIT: This is solved now that I added: outputArray=p.array(outputArray) above my code. I have been at this too many hours and need to take a break for a while if I am making these kinds of mistakes.

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• iPad + OpenGL ES2. Why the Puzzling Virtual Memory Spike During Device Reorientation?

  - by dugla

  I've been spending the afternoon starring at Xcode Instruments memory monitor trying to decipher the following memory issue. I have a fullscreen OpenGL ES2 app running on iPad. I am fanatical about memory issues so my retains/releases are all nicely balanced. I closely monitor memory leaks. My app is basically squeeky clean. Except occassionally when I reorient the device. Portrait to Landscape. Back and forth I rock the device stress testing my discarding and rebuilding of the OpenGL framebuffer. The ambient memory footprint of my app is about 70MB Real Mems and 180MB Virtual Mems. Real memory hardly varies at all during device rotations. However the virtual mems reading sometimes briefly spikes up to 250MB and then recedes back to 180MB. No real pattern. But clearly related discarding/rebuilding the framebuffer. I see random memory warnings in my NSlogs but the app just hums along, no worries. 1) Since iPhone OS devices don't have VM could someone explain to me what the VM reading actually means? 2) My app totally leak free and generally bulletproof dispite the VM spikes. Never crashes. Rock solid. Should I be concerned about this? 3) There is clearly something happening in OpenGL framebuffer land that is causing this but I am using the API in the proper way: paraphrasing: Discarding the framebuffer: glDeleteRenderbuffers(1, &m_colorbuffer); glDeleteFramebuffers(1, &m_framebuffer); Rebuilding the framebuffer: glGenFramebuffers(1, &m_framebuffer); glGenRenderbuffers(1, &m_colorbuffer); Is there some other memory flushing trick I have missed? Thanks for any insight. Cheers, Doug

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• Implementing arrays using a stack

  - by Zack

  My programming language has no arrays, no lists, no pointers, no eval and no variable variables. All it has: Ordinary variables like you know them from most programming languages: They all have an exact name and a value. One stack. Functions provided are: push (add element to top), pop (remove element from top, get value) and empty (check if stack is empty) My language is turing-complete. (Basic arithmetics, conditional jumps, etc implemented) That means, it must be possible to implement some sort of list or array, right? But I have no idea how... What I want to achieve: Create a function which can retrieve and/or change an element x of the stack. I could easily add this function in the implementation of my language, in the interpreter, but I want to do it in my programming language. "Solution" one (Accessing an element x, counting from the stack top) Create a loop. Pop off the element from the stack top x times. The last element popped of is element number x. I end up with a destroyed stack. Solution two: Do the same as above, but store all popped off values in a second stack. Then you could move all elements back after you are done. But you know what? I don't have a second stack!

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• How do you pass .net objects values around in F#?

  - by Russell

  I am currently learning F# and functional programming in general (from a C# background) and I have a question about using .net CLR objects during my processing. The best way to describe my problem will be to give an example: let xml = new XmlDocument() |> fun doc -> doc.Load("report.xml"); doc let xsl = new XslCompiledTransform() |> fun doc -> doc.Load("report.xsl"); doc let transformedXml = new MemoryStream() |> fun mem -> xsl.Transform(xml.CreateNavigator(), null, mem); mem This code transforms an XML document with an XSLT document using .net objects. Note XslCompiledTransform.Load works on an object, and returns void. Also the XslCompiledTransform.Transform requires a memorystream object and returns void. The above strategy used is to add the object at the end (the ; mem) to return a value and make functional programming work. When we want to do this one after another we have a function on each line with a return value at the end: let myFunc = new XmlDocument("doc") |> fun a -> a.Load("report.xml"); a |> fun a -> a.AppendChild(new XmlElement("Happy")); a Is there a more correct way (in terms of functional programming) to handle .net objects and objects that were created in a more OO environment? The way I returned the value at the end then had inline functions everywhere feels a bit like a hack and not the correct way to do this. Any help is greatly appreciated!

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• Syncronization Exception

  - by Kurru

  Hi I have two threads, one thread processes a queue and the other thread adds stuff into the queue. I want to put the queue processing thread to sleep when its finished processing the queue I want to have the 2nd thread tell it to wake up when it has added an item to the queue However these functions call System.Threading.SynchronizationLockException: Object synchronization method was called from an unsynchronized block of code on the Monitor.PulseAll(waiting); call, because I havent syncronized the function with the waiting object. [which I dont want to do, i want to be able to process while adding items to the queue]. How can I achieve this? Queue<object> items = new Queue<object>(); object waiting = new object(); 1st Thread public void ProcessQueue() { while (true) { if (items.Count == 0) Monitor.Wait(waiting); object real = null; lock(items) { object item = items.Dequeue(); real = item; } if(real == null) continue; .. bla bla bla } } 2nd Thread involves public void AddItem(object o) { ... bla bla bla lock(items) { items.Enqueue(o); } Monitor.PulseAll(waiting); }

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