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  • Is there a network diagram standard for illustrating web services?

    - by Phil.Wheeler
    I'm putting together a Solution Architecture document for an enhancement we're adding to our site and it occurs to me that I've never formally illustrated a web service call before. Is there a convention for how web service calls are illustrated on your garden-variety network diagram? Can anyone point me to examples or share something on Create.ly (or similar service)?

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  • Windows Phone 7 review

    - by Jeff
    I finally got around to composing some thoughts on what I think about Windows Phone 7, and I posted those impressions on my personal blog. I'll save a few bytes and not repost it here.It should be obvious that my general impression is overwhelmingly positive. What I don't go into very deeply is how much I enjoy developing stuff for it. Baby Stopwatch was not even remotely hard to build, because it wasn't complex, but also because the platform itself is so easy to deal with. I've been messing around and building something a little more involved, and it too has been fun to work with. Sure, you have the quirks of Silverlight to work out, and then the phone-specific quirks after that, but it really is a lot of fun. If you haven't come up with a science project for the phone, I would encourage you to do so.Now if only I could find a gig here at Microsoft where people just build phone apps all day! (But not games... I know we already do that quite a bit.)

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  • [GEEK SCHOOL] Network Security 1: Securing User Accounts and Passwords in Windows

    - by Matt Klein
    This How-To Geek School class is intended for people who want to learn more about security when using Windows operating systems. You will learn many principles that will help you have a more secure computing experience and will get the chance to use all the important security tools and features that are bundled with Windows. Obviously, we will share everything you need to know about using them effectively. In this first lesson, we will talk about password security; the different ways of logging into Windows and how secure they are. In the proceeding lesson, we will explain where Windows stores all the user names and passwords you enter while working in this operating systems, how safe they are, and how to manage this data. Moving on in the series, we will talk about User Account Control, its role in improving the security of your system, and how to use Windows Defender in order to protect your system from malware. Then, we will talk about the Windows Firewall, how to use it in order to manage the apps that get access to the network and the Internet, and how to create your own filtering rules. After that, we will discuss the SmartScreen Filter – a security feature that gets more and more attention from Microsoft and is now widely used in its Windows 8.x operating systems. Moving on, we will discuss ways to keep your software and apps up-to-date, why this is important and which tools you can use to automate this process as much as possible. Last but not least, we will discuss the Action Center and its role in keeping you informed about what’s going on with your system and share several tips and tricks about how to stay safe when using your computer and the Internet. Let’s get started by discussing everyone’s favorite subject: passwords. The Types of Passwords Found in Windows In Windows 7, you have only local user accounts, which may or may not have a password. For example, you can easily set a blank password for any user account, even if that one is an administrator. The only exception to this rule are business networks where domain policies force all user accounts to use a non-blank password. In Windows 8.x, you have both local accounts and Microsoft accounts. If you would like to learn more about them, don’t hesitate to read the lesson on User Accounts, Groups, Permissions & Their Role in Sharing, in our Windows Networking series. Microsoft accounts are obliged to use a non-blank password due to the fact that a Microsoft account gives you access to Microsoft services. Using a blank password would mean exposing yourself to lots of problems. Local accounts in Windows 8.1 however, can use a blank password. On top of traditional passwords, any user account can create and use a 4-digit PIN or a picture password. These concepts were introduced by Microsoft to speed up the sign in process for the Windows 8.x operating system. However, they do not replace the use of a traditional password and can be used only in conjunction with a traditional user account password. Another type of password that you encounter in Windows operating systems is the Homegroup password. In a typical home network, users can use the Homegroup to easily share resources. A Homegroup can be joined by a Windows device only by using the Homegroup password. If you would like to learn more about the Homegroup and how to use it for network sharing, don’t hesitate to read our Windows Networking series. What to Keep in Mind When Creating Passwords, PINs and Picture Passwords When creating passwords, a PIN, or a picture password for your user account, we would like you keep in mind the following recommendations: Do not use blank passwords, even on the desktop computers in your home. You never know who may gain unwanted access to them. Also, malware can run more easily as administrator because you do not have a password. Trading your security for convenience when logging in is never a good idea. When creating a password, make it at least eight characters long. Make sure that it includes a random mix of upper and lowercase letters, numbers, and symbols. Ideally, it should not be related in any way to your name, username, or company name. Make sure that your passwords do not include complete words from any dictionary. Dictionaries are the first thing crackers use to hack passwords. Do not use the same password for more than one account. All of your passwords should be unique and you should use a system like LastPass, KeePass, Roboform or something similar to keep track of them. When creating a PIN use four different digits to make things slightly harder to crack. When creating a picture password, pick a photo that has at least 10 “points of interests”. Points of interests are areas that serve as a landmark for your gestures. Use a random mixture of gesture types and sequence and make sure that you do not repeat the same gesture twice. Be aware that smudges on the screen could potentially reveal your gestures to others. The Security of Your Password vs. the PIN and the Picture Password Any kind of password can be cracked with enough effort and the appropriate tools. There is no such thing as a completely secure password. However, passwords created using only a few security principles are much harder to crack than others. If you respect the recommendations shared in the previous section of this lesson, you will end up having reasonably secure passwords. Out of all the log in methods in Windows 8.x, the PIN is the easiest to brute force because PINs are restricted to four digits and there are only 10,000 possible unique combinations available. The picture password is more secure than the PIN because it provides many more opportunities for creating unique combinations of gestures. Microsoft have compared the two login options from a security perspective in this post: Signing in with a picture password. In order to discourage brute force attacks against picture passwords and PINs, Windows defaults to your traditional text password after five failed attempts. The PIN and the picture password function only as alternative login methods to Windows 8.x. Therefore, if someone cracks them, he or she doesn’t have access to your user account password. However, that person can use all the apps installed on your Windows 8.x device, access your files, data, and so on. How to Create a PIN in Windows 8.x If you log in to a Windows 8.x device with a user account that has a non-blank password, then you can create a 4-digit PIN for it, to use it as a complementary login method. In order to create one, you need to go to “PC Settings”. If you don’t know how, then press Windows + C on your keyboard or flick from the right edge of the screen, on a touch-enabled device, then press “Settings”. The Settings charm is now open. Click or tap the link that says “Change PC settings”, on the bottom of the charm. In PC settings, go to Accounts and then to “Sign-in options”. Here you will find all the necessary options for changing your existing password, creating a PIN, or a picture password. To create a PIN, press the “Add” button in the PIN section. The “Create a PIN” wizard is started and you are asked to enter the password of your user account. Type it and press “OK”. Now you are asked to enter a 4-digit pin in the “Enter PIN” and “Confirm PIN” fields. The PIN has been created and you can now use it to log in to Windows. How to Create a Picture Password in Windows 8.x If you log in to a Windows 8.x device with a user account that has a non-blank password, then you can also create a picture password and use it as a complementary login method. In order to create one, you need to go to “PC settings”. In PC Settings, go to Accounts and then to “Sign-in options”. Here you will find all the necessary options for changing your existing password, creating a PIN, or a picture password. To create a picture password, press the “Add” button in the “Picture password” section. The “Create a picture password” wizard is started and you are asked to enter the password of your user account. You are shown a guide on how the picture password works. Take a few seconds to watch it and learn the gestures that can be used for your picture password. You will learn that you can create a combination of circles, straight lines, and taps. When ready, press “Choose picture”. Browse your Windows 8.x device and select the picture you want to use for your password and press “Open”. Now you can drag the picture to position it the way you want. When you like how the picture is positioned, press “Use this picture” on the left. If you are not happy with the picture, press “Choose new picture” and select a new one, as shown during the previous step. After you have confirmed that you want to use this picture, you are asked to set up your gestures for the picture password. Draw three gestures on the picture, any combination you wish. Please remember that you can use only three gestures: circles, straight lines, and taps. Once you have drawn those three gestures, you are asked to confirm. Draw the same gestures one more time. If everything goes well, you are informed that you have created your picture password and that you can use it the next time you sign in to Windows. If you don’t confirm the gestures correctly, you will be asked to try again, until you draw the same gestures twice. To close the picture password wizard, press “Finish”. Where Does Windows Store Your Passwords? Are They Safe? All the passwords that you enter in Windows and save for future use are stored in the Credential Manager. This tool is a vault with the usernames and passwords that you use to log on to your computer, to other computers on the network, to apps from the Windows Store, or to websites using Internet Explorer. By storing these credentials, Windows can automatically log you the next time you access the same app, network share, or website. Everything that is stored in the Credential Manager is encrypted for your protection.

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  • Oracle Enterprise Manager Ops Center 12c is now available for download at Oracle technology Network

    - by Anand Akela
    Oracle Enterprise Manager Ops Center 12c is available now for download at Oracle Technology Network (OTN ) . Oracle Enterprise Manager Ops Center web page at Oracle Technology Network Join Oracle Launch Webcast : Total Cloud Control for Systems on April 12th at 9 AM PST to learn more about  Oracle Enterprise Manager Ops Center 12c from Oracle Senior Vice President John Fowler, Oracle Vice President of Systems Management Steve Wilson and a panel of Oracle executive. Stay connected with  Oracle Enterprise Manager   :  Twitter | Facebook | YouTube | Linkedin | Newsletter

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  • How To Block Web Sites at the Router Level for Network Wide Filtering

    - by Jason Fitzpatrick
    A comprehensive network filtering system is overkill if all you want to do is block a handful of web sites. Read on as we show you how—with nothing more than your router—you can selectively block and temporarily restrict individual websites. For many people a massive commercial internet filter is overkill. What if you just want to block Facebook when your kids are supposed to be doing their homework or Reddit when you’re supposed to be getting work done? You don’t need a huge system for that, all you need is the access restrictions module in your router. Today we’re looking at how you can quickly and easily block traffic on your network using router-based access restrictions. HTG Explains: When Do You Need to Update Your Drivers? How to Make the Kindle Fire Silk Browser *Actually* Fast! Amazon’s New Kindle Fire Tablet: the How-To Geek Review

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  • Terminal Errors/Package Erros

    - by Bryan
    After running some updates a week ago or so, I've noticed that after any installations via the Ubuntu Software Center or any installed in the GUI have given an error message stating that there was a package error. Also any installations done through the terminal have given the E: Sub-process /usr/bin/dpkg returned an error code (1) message at the end of each install. Oddly, the software is still installed and seems to function properly. Is there any way to get rid of this? I've tried to run apt-get autoclean as recommended on another site, but this doesn't seem to work. I'm fairly new to Linux/Ubuntu, just FYI.

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  • Enterprise Data Quality - New and Improved on Oracle Technology Network

    - by Mala Narasimharajan
    Looking for Enterprise Data Quality technical and developer resources on your projects? Wondering where the best place is to go for finding the latest documentations, downloads and even code samples and libraries?  Check out the new and improved Oracle Technical Network pages for Oracle Enterprise Data Quality.  This section features developer forums as well for EDQ and Master Data Management so that you can connect with other technical professionals who have submitted concerns or posted tips and tricks and learn from them.  Here are the links to bookmark:    Oracle Technology Network website * NEW *   Installation Guide for Enterprise Data Quality Address Verification  Enterprise Data Quality Forum For more information on Oracle's software offerings for data quality and master data management visit:  http://www.oracle.com/us/products/applications/master-data-management/index.html http://www.oracle.com/us/products/middleware/data-integration/enterprise-data-quality/overview/index.html   

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  • Any online network topology to study?

    - by Gok Demir
    I want to study network. But I don't have an access to a sample network (routers, DNS, IP4, IP6 windows linux mixed heterogenous system). Do you know any online network to study (Free as possible). Is it possible to simulate network topologies with a sing PC using virtual machine. If so could you guide me?

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  • SUPINFO International University in Mauritius

    Since a while I'm considering to pick up my activities as a student and I'd like to get a degree in Computer Science. Personal motivation I mean after all this years as a professional software (and database) developer I have the personal urge to complete this part of my education. Having various certifications by Microsoft and being awarded as an Microsoft Most Valuable Professional (MVP) twice looks pretty awesome on a resume but having a "proper" degree would just complete my package. During the last couple of years I already got in touch with C-SAC (local business school with degree courses), the University of Mauritius and BCS, the Chartered Institute for IT to check the options to enroll as an experienced software developer. Quite frankly, it was kind of alienating to receive that feedback: Start from scratch! No seriously? Spending x amount of years to sit for courses that might be outdated and form part of your daily routine? Probably being in an awkward situation in which your professional expertise might exceed the lecturers knowledge? I don't know... but if that's path to walk... Well, then I might have to go for it. SUPINFO International University Some weeks ago I was contacted by the General Manager, Education Recruitment and Development of Medine Education Village, Yamal Matabudul, to have a chat on how the local IT scene, namely the Mauritius Software Craftsmanship Community (MSCC), could assist in their plans to promote their upcoming campus. Medine went into partnership with the French-based SUPINFO International University and Mauritius will be the 36th location world-wide for SUPINFO. Actually, the concept of SUPINFO is very likely to the common understanding of an apprenticeship in Germany. Not only does a student enroll into the programme but will also be placed into various internships as part of the curriculum. It's a big advantage in my opinion as the person stays in touch with the daily procedures and workflows in the real world of IT. Statements like "We just received a 'crash course' of information and learned new technology which is equivalent to 1.5 months of lectures at the university" wouldn't form part of the experience of such an education. Open Day at the Medine Education Village Last Saturday, Medine organised their Open Day and it was the official inauguration of the SUPINFO campus in Mauritius. It's now listed on their website, too - but be warned, the site is mainly in French language although the courses are all done in English. Not only was it a big opportunity to "hang out" on the campus of Medine but it was great to see the first professional partners for their internship programme, too. Oh, just for the records, IOS Indian Ocean Software Ltd. will also be among the future employers for SUPINFO students. More about that in an upcoming blog entry. Open Day at Medine Education Village - SUPINFO International University in Mauritius Mr Alick Mouriesse, President of SUPINFO, arrived the previous day and he gave all attendees a great overview of the roots of SUPINFO, the general development of the educational syllabus and their high emphasis on their partnerships with local IT companies in order to assist their students to get future jobs but also feel the heartbeat of technology live. Something which is completely missing in classic institutions of tertiary education in Computer Science. And since I was on tour with my children, as usual during weekends, he also talked about the outlook of having a SUPINFO campus in Mauritius. Apart from the close connection to IT companies and providing internships to students, SUPINFO clearly works on an international level. Meaning students of SUPINFO can move around the globe and can continue their studies seamlessly. For example, you might enroll for your first year in France, then continue to do 2nd and 3rd year in Canada or any other country with a SUPINFO campus to earn your bachelor degree, and then live and study in Mauritius for the next 2 years to achieve a Master degree. Having a chat with Dale Smith, Expand Technologies, after his interesting session on Technological Entrepreneurship - TechPreneur More questions by other craftsmen of the Mauritius Software Craftsmanship Community And of course, this concept works in any direction, giving Mauritian students a huge (!) opportunity to live, study and work abroad. And thanks to this, Medine already announced that there will be new facilities near Cascavelle to provide dormitories and other facilities to international students coming to our island. Awesome! Okay, but why SUPINFO? Well, coming back to my original statement - I'd like to get a degree in Computer Science - SUPINFO has a process called Validation of Acquired Experience (VAE) which is tailor-made for employees in the field of IT, and allows you to enroll in their course programme. I already got in touch with their online support chat but was only redirected to some FAQs on their website, unfortunately. So, during the Open Day I seized the opportunity to have an one-on-one conversation with Alick Mouriesse, and he clearly encouraged me to gather my certifications and working experience. SUPINFO does an individual evaluation prior to their assignment regarding course level, and hopefully my chances of getting some modules ahead of studies are looking better than compared to the other institutes. Don't get me wrong, I don't want to go down the easy route but why should someone sit for "Database 101" or "Principles of OOP" when applying and preaching database normalisation and practicing Clean Code Developer are like flesh and blood? Anyway, I'll be off to get my transcripts of certificates together with my course assignments from the old days at the university. Yes, I studied Applied Chemistry for a couple of years before intersecting into IT and software development particularly... ;-)

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  • New Energy Harvesting Network

    University of Southampton School of Electronics and Computer Science to manage EH Network, also hosts 'More-than-Moore' and 'Beyond CMOS' symposium Southampton University - Computer science - Education - England - Colleges and Universities

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  • Difference between $ and # in ADF/JSF/JSP

    - by pavan.pvj
    Found this one interesting. So, picked it from one of the books and posting here.JSP 2.1 and JSF 1.2 - both of them use a unified Expression language. One major and the most obvious difference is between $ and #. JSP 2.1 uses $ and JSF 1.2 uses # in an EL. $ - immediate evaluation# - deferred evaluation$ - $ syntax executes expressions eagerly/immediately, which means that the result is returned immediately when the page renders.# - # syntax defers the expression evaluation to a point defined by the implementing technology. In general, JSF uses deferred EL evaluation because of its multiple lifecycle phases in which events are handled. To ensure the model is prepared before the values are accessed by EL, it must defer EL evaluation until the appropriate point in the life cycle.Note: This is picked up from Oracle Fusion Developer Guide (ISBN: 9780071622547). There is also a very good article here:http://java.sun.com/products/jsp/reference/techart/unifiedEL.html

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • Can't connect to Wired Network after installing 12.04

    - by ezz9
    I have installed 12.04 into a used HP Compaq DC 7100 CMT. Plugged in LAN cable into the computer and it says network disconnected. from what I understand on the things I've read, it's not getting the address right, maybe it's just a guess (hardware address 00:16:35:78:47:bb). I know the LAN cable is working I can get on the net with the old computer. (Old computer is using device MAC address; Auto eth0 00:11:11:E6:4F:FE). I have put this address into the newer HP and it shows last used (minutes ago) but no Internet sever not found. I tried the hardware address it says never. I feel and think this should be easy to fix. But I just don't know. Here is the info everyone has asked for, but they never say what I should do. sudo lshw -C network; rfkill list; cat /etc/network/interfaces; cat /etc/lsb-release; lspci -nn; lsusb; uname -a; ifconfig; route -n *-network description: ethernet interface product; NetXtreme BCM5751 Gigabit Ethernet PCI Express vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:40:00.0 logical name: eth0 verson: 01 serial: 00:16:35:78:47:bb size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000-fd configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion= 3.121 duplex=full firmware=5751-v3.29a latency=0 link=yes multicast=yes port=twi sted pair speed=100Mbit/s resources: irq:17 memory:f0400000-f040ffff auto lo iface lo inet loopback DISTRIB_ID=Ubuntu DISTRIB_RELEASE=12.04 DISTRIB_CODENAME=precise DISTRIB_DESCRIPTION= "Ubuntu 12.04 LTS" 00:00.0 host bridge [0600]: Inter Corporation 82915G/P/GV/GL/PL/910GL Memory Con troller Hub [8086:2580] (rev 04) 00.02.0 VGA compatible controller [0300]: Intel Corporation 82915G/GV/910GL inte grated Graphics Controller [8086:2582] (rev 04) 00:1c.0 PCI bridge [0604]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 1 [8086:2660] (rev 03) 00:1c.1 PCI bridge [0604]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 2 [8086:2662] (rev 03) 00:1d.0 USB controller [0c03]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Fam ily) USB UHCI #1 [8086:2658] (rev 03) 00:1d.1 USB controller [0c03]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Fam ily) USB UHCI #2 [8086:2659] (rev 03) 00:1d.2 USB controller [0c03]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Fam ily) USB UHCI #3 [8086:265a] (rev 03) 00:1d.3 USB controller [0c03]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Fam ily) USB UHCI #4 [8086:265b] (rev 03) 00:1d.7 USB controller [0c03]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Fam ily) USB2 UHCI Controller [8086:265c] (rev 03) 00:1e.0 PCI bridge [0604]: Intel Corporation 82801 PCI bridge [8086:244e] (rev d 3) 00:1e.2 Multimedia audio controller [0401]: Intel Corporation 82801FB/FBM/FR/FW/ FRW (ICH6 Family) AC'97 Autio conrtroller [8086:266e] (rev 03) 00:1f.0 ISA bridge [0601]: Intel Corporation 82801FB/RF (ICH6/ICH6R) LPC Interfa ce Bridge [8086:2640] (rev 03) 00:1f.1 IDE interface [0101]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 fami ly) IDE Controller [8086:266f] (rev 03) 00:1f.2 IDE interface [0101]: Intel Corporation 82801FB/FW (ICH6/ICH6W) SATA Con troller [8086:2651] (rev 03) 40:00.0 Ethernet controller [0200]: Broadcom Corporation NetXreme BCM5751 Gigab it Ethernet PCI Express [14e4:1677} (rev 01) Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Linux bob-desktop 3.2.0-23-generic-pae #36-Ubuntu SMP Tpr 10 22:19:09 UTC 20 12 i686 i686 i386 GNU/Linux eth0 Link encap:Ethernet HWaddr 00:16:35:78:47:bb inet6 addr: fe80::216:35ff:47bb/64 Scope:link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2517 errors:0 dropped:0 overruns:0 frame:0 TX packets:164 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:164508 (164.5 KB) TX bytes: 40884 (40.0 KB) Interrupt:17 lo Link encap:Local loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:3290 errors:0 dropped:0 overruns:0 frame:0 TX packets:3290 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen: 0 RX bytes:267212 (267.2 KB) TX bytes: 267212 (267.2 KB) Kernel Ip routing table Destination Gateway Genmask Flags Metric Ref Use Iface ran this sudo dhclient eth0 no reply ran this ip addr 1: lo <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST ,MULTICAST ,UP ,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000 link/enter 00:16:35:78:47:BB brd ff:ff:ff:ff:ff:ff inet 169.254.7.172/16 brd 169.254.255.255 scope link eth0:avahi inet6 fe80::216:35ff:fe78:47bb/64 scope link valid_lft forever preferred_lft forever Help please.

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  • SSD Fresh Does Not Start

    - by Jim Fell
    I recently installed a new 60GB SSD as my primary hard drive and re-installed Windows 7 Professional 64-bit. I then installed SSD Fress from Abelssoft to optimize Windows to run on the SSD. It seemed to install okay, but when I try to run the utility, its splash screen appears briefly before it quietly closes. No errors are displayed; the utility just fails to launch. I have run SSD Fresh on another SSD-equipped Windows 7 Pro x64 computer in the past without any problems. Does anyone know what might be preventing the program from running? I tried shutting down the Spybot Resident and disabling the firewall and virus scanner with no luck. I also tried running the tool as administrator; I even tried reinstalling it, running the installer as administrator. No luck. Every time I try to launch the program the Event Viewer logs this same set of errors: Error 4/2/2012 11:35:44 PM Application Error 1000 (100) Error 4/2/2012 11:35:43 PM .NET Runtime 1026 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None Error 4/2/2012 11:35:39 PM SideBySide 59 None For those who are interested, here is my system configuration: ASRock M3A770DE AM3 AMD 770 ATX AMD Motherboard AMD Athlon II X3 455 Rana 3.3GHz Socket AM3 95W Triple-Core Desktop Processor ADX455WFGMBOX G.SKILL Value Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model F3-10600CL9D-8GBNT Mushkin Enhanced Chronos Deluxe MKNSSDCR60GB-DX 2.5" 60GB SATA III Synchronous MLC Internal Solid State Drive (SSD) (Primary/Boot HD) Western Digital Caviar Blue RFHWD1600AAJS 160GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive (Secondary HD) Sony Optiarc CD/DVD Burner Black SATA Model AD-7261S-0B LightScribe Support RAIDMAX RX-850AE 850W ATX12V v2.3 / EPS12V SLI Certified CrossFire Ready 80 PLUS GOLD Certified Modular Active PFC Power Supply ASUS HD7850-DC2-2GD5 Radeon HD 7850 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card Asus ML228H 21.5" Full HD LED BackLight LED Monitor Slim Design (x3)

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  • Can't connect to my own wifi network

    - by Nicolas
    I use ubuntu 12.04 on various differents laptops/netbooks on my home. I was able to connect to my own wifi network. But sometimes, I couldn't connect to my wifi network, it ask me for password again and again. After many tries (a lot of them), sometimes I can connect, but sometimes I can't. I have this problem with a Samsung netbook and with a HP laptop. Right now, I can't connect with the HP laptop. I'll be grateful for any help. Best regards, Nicolás

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  • A Method for Reducing Contention and Overhead in Worker Queues for Multithreaded Java Applications

    - by Janice J. Heiss
    A java.net article, rich in practical resources, by IBM India Labs’ Sathiskumar Palaniappan, Kavitha Varadarajan, and Jayashree Viswanathan, explores the challenge of writing code in a way that that effectively makes use of the resources of modern multicore processors and multiprocessor servers.As the article states: “Many server applications, such as Web servers, application servers, database servers, file servers, and mail servers, maintain worker queues and thread pools to handle large numbers of short tasks that arrive from remote sources. In general, a ‘worker queue’ holds all the short tasks that need to be executed, and the threads in the thread pool retrieve the tasks from the worker queue and complete the tasks. Since multiple threads act on the worker queue, adding tasks to and deleting tasks from the worker queue needs to be synchronized, which introduces contention in the worker queue.” The article goes on to explain ways that developers can reduce contention by maintaining one queue per thread. It also demonstrates a work-stealing technique that helps in effectively utilizing the CPU in multicore systems. Read the rest of the article here.

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  • Deny to administrators to change network configuration settings

    - by moronrats
    I need to provide admin rights to every user but the users should not able to change network configuration settings. For this I have enabled following policies in User Configuration\Administrative Templates\Network\Network connections Enable Windows 2000 network connection settings for administrators Prohibit access to properties of a LAN connection Prohibit access to properties of components a LAN connection Users (that exist in administrators) still can change the LAN properties. Are there any other solutions?

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  • Which computer side has more salary chance in future programmer , sys admin , network admin , web developer

    - by Name
    I want to know which computer field has more probability of getting high salary with experience in the following fields 1)Programmer c , c++ , java 2)Sys admin MIcrosoft . linux 3)Network admin (Cisco ccna ccnp 4)web developer Any more idea will be good i work as web developer for 3 years and stiing at 40K$. I have to find new job and still look like i don't have offer more than 50K. may be i have chosen the wrong path. My friend in network admin has started from 65K and with experince he is going the ccnp or ccie with more high packages. I may e wrong , please correct me

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