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  • Presenting at the San Francisco SQL Server User Group - 12-Sep-2012

    - by RickHeiges
    I have a business trip scheduled out far enough in advance for a change. I was able to schedule a presentation at the San Francisco SQL Server User Group on Sep 12 about SQL Server Consolidation Strategies. If you will be in the SF area on Sep 12, I invite you to attend ar just drop by to say hello. You can find out more about the group at http://www.meetup.com/The-San-Francisco-SQL-Server-Meetup-Group/ Hope to see you there!...(read more)

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  • Silverlight As Transmedia Platform Silverlight TV

    I’m very excited to say that my discussion with John Papa about Silverlight as a Transmedia Storytelling Platform is live....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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  • What change in mindset are needed for a Jave/C# programmer when learning Swift?

    - by Ian
    Swift seem to fit into the same “space” as Java/C# as it was created to make it easier to create end user applications. It is also used to target smart phones like Java/C#. However reading it’s documentation it seems to come from anther universe, you could say it is from Jupiter while C#/Java is from Saturn. As a C# programmer I am finding myself making assumptions that are not true, so what are the conceptual “traps” that I should look out for while leaning about Swift?

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  • Augmented Reality and Translation: Use Case in Enterprise?

    - by ultan o'broin
    Really love this iPhone app from Visual Quest: Word Lens Great to see the concept of augmented reality (a hot topic in UX) and translation coming together. Of course, I've downloaded the app and I'm trying it out already! Mashable say it all about this app in terms of how it seems like Sci-Fi is coming to life. However, the question remains: How could such an app be used in the enterprise applications space? Opinions welcome!

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  • Silverlight Cream for May 22, 2010 -- #867

    - by Dave Campbell
    In this Issue: Michael Washington, Xianzhong Zhu, Jim Lynn, Laurent Bugnion, and Kyle McClellan. A ton of Shoutouts this time: Cigdem Patlak (CrocusGirl) is interviewed about Silverlight 4 on Channel 9: Silverlight discussion with Cigdem Patlak Timmy Kokke has material up from a presentation he did, and check out the SilverAmp project he's got going: Code & Slides – SDE – What’s new in Silverlight 4 Graham Odds at ScottLogic has an interesting post up: Contextual cues in user interface design Einar Ingebrigtsen is discussing Balder licensing and is asking for input: Balder - Licensing SilverLaw has updated two of his stylings at the Expression Gallery to Silverlight 4: ChildWindow and Accordion Styling Silverlight 4 Keep this page bookmarked -- it's the only page you'll need for Silverlight and Expression links.. well, that and my blog :) .. from Adam Kinney: Silverlight and Expression Blend Jeremy Boyd and John-Daniel Trask have some sweet-looking controls in their new release: Introducing Silverlight Elements 1.1 Matthias Shapiro entered the Design for America competition with his Recovery Review: A Silverlight Sunlight Foundation Visualization Project be sure to check out his blog post about it -- there's a link at the bottom. Koen Zwikstra announed a new release: Document Toolkit 2 Beta 1 available ... built for SL4 and lots of features -- check out the blog post. From SilverlightCream.com: Simple Example To Secure WCF Data Service OData Methods Michael Washington has a follow-on tutorial up on WCF Data Security with OData -- essentially this is the 'securing the data' part ... the Silverlight part was in the previous post... all code is available. Developing Freecell Game Using Silverlight 3 Part 1 Xianzhong Zhu has the first of a two-part tutorial up on building Freecell in Silverlight 3 ... yeah... SL3 -- oh, can you say WP7?? :) Silverlight Top Tip: Startup page for Navigation Apps Jim Lynn has detailed how to go straight to a specific page you're working on in a complex Silverlight app say for debug purposes rather than page/page/page ... I was just thinking yesterday about putting a shortcut on my taskbar for something similar in .NET :) Handling DataGrid.SelectedItems in an MVVM-friendly manner Laurent Bugnion responded with code to a question about getting a DataGrid's SelectedItems into the ViewModel in MVVMLight. Demo code available too. RIA Services and Windows Live ID Kyle McClellan has a post up discussing using LiveID and RIA Services and Silverlight. Lots of external links sprinkled around. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • upstart-supervised init script for Apache?

    - by Ben Williams
    I want to run apache on Ubuntu 10.04, and use the nice supervision stuff in upstart (I'm not just talking about the apache init script, but proper service supervision a la daemontools - which is to say, restarting apache when it dies, things like that). Does anyone have a running upstart config for supervising apache on ubuntu 10.04? The Googles have been no help to me, but it could be that my google-fu is weak.

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  • Personal Development : Time, Planning , Repairs & Maintenance

    - by Rajesh Pillai
    Personal Development : Time, Planning, Repairs & Maintenance These are just my thoughts, but some you may find something interesting in it. Please think over it. We may know many things, but still we always keeps procrastinating it. I have written this as I have heard many people coming back and saying they don’t have time to do things they like. These are my thoughts buy may be useful to someone else too. Certain things in life needs periodic repairs and maintenance. To cite some examples , your CAR, your HOUSE, your personal laptop/desktop, your health etc. Likewise there are certain other things in professional life that requires repair/ maintenance /or some kind of polishing, so that you always stay on top of it. But they are not always obvious. Some of them are - Improving your communication skills - Increasing your vocabulary - Upgrading your technical skills - Pursuing your hobby - Increasing your knowledge/awareness etc… etc… And then there are certain things that we are always short of…. one is TIME. We all know TIME is one of the most precious things in life and yet we all are very miserable at managing it. Remember you can only manage it and not control it. You can only control which you own or which you create. In theory time is infinite. So, there should be abundant of it. But remember one thing, you know this, it’s not reversible. Once it has elapsed you cannot live it again. Think over it. So, how do find that golden 25th hour every day. To find the 25th hour you need to reflect back on your current daily activities. Analyze them and see where you are spending most of your time and is it really important. Even the 8 hours that you spent in the office, is it spent fruitfully. At the end of the day is the 8 precious hour that you spent was worth it. Just reflect back on your activities. Did you learn something? If yes did you make a point to NOTE IT. If you didn’t NOTED it then was the time you spent really worth it. Just ponder over it. Some calculations of your daily activities where most of the time is spent. Let’s start (in no particular order though) - Sleep (6.5 hours) [Remember you only require 6 good hours of sleep every day]. Some may thing it is 8, but it’s a myth.   o To achive 6 hours of sleep and be in good health you can practice 15 minutes of daily meditation. So effectively you can    round it to 6.5 hours. - Morning chores(2 hours) : Some may need to prepare breakfast and all other things. - Office commuting (avg. to and fro 3 hours) - Office Work (avg 9.5 hours) Total Hours: 21 hours effective time which is spent irrespective of what you do. There may be some variations here and there. Still you have 3 hours EXTRA. Where do these 3 hours go? If you can find it, then you may get that golden 25th hour out of these 3 hours. Let’s discount 2 hours for contingencies, still you have 1 hour with you. If you can’t find it then you are living a direction less life. As you can see, the 25th Hour lies within the 24 hours of the day. It’s upto each one of us to find and make use of it. Now what can you do with that 25th hour i.e. 1 hour extra of your life. Imagine the possibility. Again some calculations 1 hour daily * 30 days = 30 hours every month 30 hours pm * 12 month = 360 hours every year. 360 hours every year seems very promising. Let’s add some contingencies, say, let’s be optimistic and say 50 % contingency. Still you have 180 hours every year. That leaves with 30 minutes every day of extra time. That’s hell a lot of time, if you could manage it. These may sound like a high talk [yes, it is, unless you apply these simple rules and rationalize your everyday living and stop procrastinating]. NOTE: I haven’t taken weekend, holidays and leaves into account. So, that leaves us with a lot of buffer time. You can meet family friends, relatives, other tasks, and yet have these 180 pure hours of joy every year. Do whatever you want to do with it. So, how important is this 180 hours per year to you? Just think over it. You may use it the way you like - 50 hours [pursue your hobby like drawing, crafting, learn dance, learn juggling, learn swimming, travelling hmm.. anything you like doing and you didn’t had time to do it.] - 30 hours you can learn a new programming language or technology (i.e. you can get comfortable with it) - 50 hours [improve existing skills] - 20 hours [improve you communication skill]. Do some light reading. - 30 hours [YOU DECIDE WHAT TO DO]? So, if you had done this for one year you would have learnt a new programming language, upgraded existing skills, improved you communication etc.. If you had done this for two years.. imagine the level of personal development or growth which you may have attained….. If you had done this for three years….. NOW I think I don’t need to mention this… So, you still have TIME, as they say TIME is infinite. So, make judicious use of this precious thing. And never ever comeback saying “I don’t have time”. So, if you are RICH in TIME, everything else will be automatically taken care of, as those things may just be a byproduct of how you spend your time… So, happy TIMING your TIME everyday.

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  • Is Wireless LTSP possible?

    - by DaimyoKirby
    Background: I've been doing research into LTSP, to see if it would be a viable option for my school. However, (almost) everything I've found say that wireless LTSP isn't possible. This is a problem since my school almost exclusively uses Apple laptops. Question: Having every classroom wire its laptops into the network is unrealistic, so is there a way to have clients wirelessly boot into the LTSP server?

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  • Xcode workspace with Unity3D as a sub-project?

    - by Di Wu
    Let's say we're developing a 2D game with Cocos2d-iPhone and UIKit and CoreAnimation. But we're also considering leveraging the 3D capabilities of Unity 3D. Is it possible that we add the Unity3D-generated Xcode project as a sub-project into the workspace and expose the 3D UI element as some kind of UIView subclass so that the native UIKit and CoreAnimation code could use them without the need to mess up with their underlying Unity3D implementation?

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  • SQLBeat Episode 11 – Ted the Fred Krueger Halloween SQL

    - by SQLBeat
    In this episode of the SQLBeat Podcast I speak conversationally (Ok I will just say I converse) with Ted Krueger about Elm Street, where he works as a DBA who stores nightmares in SQL Server database tables. The joke about it being BLOB storage is only one of several that may scare you away from this Halloween Special. If you like listening to two SQL guys talking about the bands they used to be in, rainbow trout and video games, come on in. Bwaaaa Haaaa Haaa…..Ok I will stop. Download the MP3

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  • Should I register the domain name that has not popular top level domain name

    - by sreginogemoh
    Lets say for example you want to register domain name assembly.com or assembly.net and find out that they are already registered(not available). Would you go with the domain name assemb.ly in such case? By having .ly the domain name represent word assembly but I think .ly domain is not so friendly for search engines? What do you think? Do you see any advantage of asemb.ly over assembly.com or assembly.net except it is shorter?

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  • What Problems Are Better Solved By SOAP Over REST?

    In the battle for web service supremacy SOAP and REST have been battling for years. In my personal opinion this debate should have never existed. Yes, both forms can be used to create an interactive web service, but each form of a service was developed independent of each other to solve two different yet similar problems. Based my research and experience I would have to say that REST should be the preferred web service methodology and SOAP should only be used in specific situations. Note, I did not say that I was against SOAP, and in fact I actually like to use SOAP when it is needed. Criteria for using SOAP: Does the service need a guaranteed level of reliability and security? Did the provider and consumer of the service agreed on a standardized data exchange format? Does the service need data context and state management? If you answer yes to any of these questions, then you may want to consider SOAP as the format for the web service. Another way to look at the relationship between REST and SOAP is to look at the medical field.  For most things a general doctor or you family health care provider can acceptably treat most conditions from the case of a common cold to a broken bone. A general doctor more aligns with REST in my opinion because for most service requirements REST fulfills a projects needs, but what happens if you need more of an advanced examination, you would go to a specialist. A specialist would already have experience dealing with specific issues that you are experiencing giving them specific context to how best treat you going forward. SOAP acts more like a specialist doctor giving that they understand the context of an issue and can treat it based on the state of other patients they have already treated. An example of where I would use SOAP over REST in real life would be a single sign-on application. I n these cases I need to check validate a username and password for authentication and authorization of a web page request. This service would need to maintain state while it authenticated a user and while it validated access to a web page on a subsequent request. This service must process every request for access and not allow caching to ensure that every request is processed and the appropriate users are allowed to view selected web pages. References: Rozlog, M. (2010). REST and SOAP: When Should I Use Each (or Both)? Retrieved 11 20, 2011, from Infoq.com: http://www.infoq.com/articles/rest-soap-when-to-use-each

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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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  • .net Interviews

    - by pdiddy
    When interviewing a .net candidate what do you look for? Let's say for a senior candidate. What kind of memorable interview have you experience, good or bad? This is going to be my first time I'll be the Interviewer. This is my second job and so I haven't got a lot of interview experience. Sure I can ask lots of .net technical questions, but what other questions can I ask and what can it bring by asking that question? Thanks,

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  • 10 Annoying Habits of a Geeky Spouse (GeekDad Wayback Machine)

    <b>Wired:</b> "Everyone has annoying habits, and a sizable part of every successful marriage is learning to live with those things each other does that annoy you. I think it&#8217;s safe to say, too, that geeks have some habits that we think are awesome, but that non-geeks find a little&#8230;less awesome."

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  • Excel Solver vs Solver Foundation

    - by JoshReuben
    I recently read a book http://www.amazon.com/Scientific-Engineering-Cookbook-Cookbooks-OReilly/dp/0596008791/ref=sr_1_1?ie=UTF8&s=books&qid=1296593374&sr=8-1 - the Excel Scientific and Engineering Cookbook.     The 2 main tools that this book leveraged were the Data Analysis Pack and Excel Solver. I had previously been aquanted with Microsoft Solver Foundation - this is a full fledged API for solving optimization problems, and went beyond being a mere Excel plugin - it exposed a C# programmatic interface for in process and a web service interface for out of process integration. were they the same? apparently not!   2 different solver frameworks for Excel: http://www.solver.com/index.html http://www.solverfoundation.com/ I contacted both vendors to get their perspectives.   Heres what the Excel Solver guys had to say:   "The Solver Foundation requires you to learn and use a very specific modeling language (OML). The Excel solver allows you to formulate your optimization problems without learning any new language simply by entering the formulas into cells on the Excel spreadsheet, something that nearly everyone is already familiar with doing.   The Excel Solver also allows you to seamlessly upgrade to products that combine Monte Carlo Simulation capabilities (our Risk Solver Premium and Risk Solver Platform products) which allow you to include uncertainty into your models when appropriate.   Our advanced Excel Solver Products also have a number of built in reporting tools for advanced analysis of the your model and it's results"           And Heres what the Microsoft Solver Foundation guys had to say:   "  With the release of Solver Foundation 3.0, Solver Foundation has the same kinds of solvers (plus a few more) than what is found in Excel Solver. I think there are two main differences:   1.      Problems are described differently. In Excel Solver the goals and constraints are specified inside the spreadsheet, in formulas. In Solver Foundation they are described either in .Net code that uses the Solver Foundation Services API, or using the OML modeling language in Excel. 2.      Solver Foundation’s primary strength is on solving large linear, mixed integer, and constraint models. That is, models that contain arbitrary nonlinear functions (such as trig functions, IF(), powers, etc) are handled a bit better by the Excel Solver at this point. "

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  • How In-Memory Database Objects Affect Database Design: The Conceptual Model

    - by drsql
    After a rather long break in the action to get through some heavy tech editing work (paid work before blogging, I always say!) it is time to start working on this presentation about In-Memory Databases. I have been trying to decide on the scope of the demo code in the back of my head, and I have added more and taken away bits and pieces over time trying to find the balance of "enough" complexity to show data integrity issues and joins, but not so much that we get lost in the process of trying to...(read more)

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  • Donald Farmer left Microsoft for QlikView

    - by Marco Russo (SQLBI)
    As many of you probably already know, Donald Farmer left Microsoft to join QlikView . There are no doubts that Donald have been “the face of Microsoft BI” in the last years. This news has been initially perceived (me included, I admit) as a possible lack of confidence in Microsoft BI Vision, but after reading his blog and many other comments from Microsoft people, I can say it is not. This is more a personal choice, looking for a new challenge in a brilliant career in a relatively smaller environment...(read more)

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  • Can Microsoft Build Appliances?

    - by andrewbrust
    Billy Hollis, my Visual Studio Live! colleague and fellow Microsoft Regional Director said recently, and I am paraphrasing, that the computing world, especially on the consumer side, has shifted from one of building hardware and software that makes things possible to do, to building products and technologies that make things easy to do.  Billy crystalized things perfectly, as he often does. In this new world of “easy to do,” Apple has done very well and Microsoft has struggled.  In the old world, customers wanted a Swiss Army Knife, with the most gimmicks and gadgets possible.  In the new world, people want elegantly cutlery.  They may want cake cutters and utility knives too, but they don’t want one device that works for all three tasks.  People don’t want tools, they want utensils.  People don’t want machines.  They want appliances. Microsoft Appliances: They Do Exist Microsoft has built a few appliance-like devices.  I would say XBox 360 is an appliance,  It’s versatile, mind you, but it’s the kind of thing you plug in, turn on and use, as opposed to set-up, tune, and open up to upgrade the internals.  Windows Phone 7 is an appliance too.  It’s a true smartphone, unlike Windows Mobile which was a handheld computer with a radio stack.  Zune is an appliance too, and a nice one.  It hasn’t attained much traction in the market, but that’s probably because the seminal consumer computing appliance -- the iPod – got there so much more quickly. In the embedded world, Mediaroom, Microsoft’s set-top product for the cable industry (used by AT&T U-Verse and others) is an appliance.  So is Microsoft’s Sync technology, used in Ford automobiles.  Even on the enterprise side, Microsoft has an appliance: SQL Server Parallel Data Warehouse Edition (PDW) combines Microsoft software with select OEMs’ server, networking and storage hardware.  You buy the appliance units from the OEMs, plug them in, connect them and go. I would even say that Bing is an appliance.  Not in the hardware sense, mind you.  But from the software perspective, it’s a single-purpose product that you visit or run, use and then move on.  You don’t have to install it (except the iOS and Android native apps where it’s pretty straightforward), you don’t have to customize it, you don’t have to program it.  Basically, you just use it. Microsoft Appliances that Should Exist But Microsoft builds a bunch of things that are not appliances.  Media Center is not an appliance, and it most certainly should be.  Instead, it’s an app that runs on Windows 7.  It runs full-screen and you can use this configuration to conceal the fact that Windows is under it, but eventually something will cause you to abandon that masquerade (like Patch Tuesday). The next version of Windows Home Server won’t, in my opinion, be an appliance either.  Now that the Drive Extender technology is gone, and users can’t just add and remove drives into and from a single storage pool, the product is much more like a IT server and less like an appliance-premised one.  Much has been written about this decision by Microsoft.  I’ll just sum it up in one word: pity. Microsoft doesn’t have anything remotely appliance-like in the tablet category, either.  Until it does, it likely won’t have much market share in that space either.  And of course, the bulk of Microsoft’s product catalog on the business side is geared to enterprise machines and not personal appliances. Appliance DNA: They Gotta Have It. The consumerization of IT is real, because businesspeople are consumers too.  They appreciate the fit and finish of appliances at home, and they increasingly feel entitled to have it at work too.  Secure and reliable push email in a smartphone is necessary, but it isn’t enough.  People want great apps and a pleasurable user experience too.  The full Microsoft Office product is needed at work, but a PC with a keyboard and mouse, or maybe a touch screen that uses a stylus (or requires really small fingers), to run Office isn’t enough either.  People want a flawless touch experience available for the times they want to read and take quick notes.  Until Microsoft realizes this fully and internalizes it, it will suffer defeats in the consumer market and even setbacks in the business market.  Think about how slow the Office upgrade cycle is…now imagine if the next version of Office had a first-class alternate touch UI and consider the possible acceleration in adoption rates. Can Microsoft make the appliance switch?  Can the appliance mentality become pervasive at the company?  Can Microsoft hasten its release cycles dramatically and shed the “some assembly required” paradigm upon which many of its products are based?  Let’s face it, the chances that Microsoft won’t make this transition are significant. But there are also encouraging signs, and they should not be ignored.  The appliances we have already discussed, especially Xbox, Zune and Windows Phone 7, are the most obvious in this regard.  The fact that SQL Server has an appliance SKU now is a more subtle but perhaps also more significant outcome, because that product sits so smack in the middle of Microsoft’s enterprise stack.  Bing is encouraging too, especially given its integrated travel, maps and augmented reality capabilities.  As Bing gains market share, Microsoft has tangible proof that it can transform and win, even when everyone outside the company, and many within it, would bet otherwise. That Great Big Appliance in the Sky Perhaps the most promising (and evolving) proof points toward the appliance mentality, though, are Microsoft’s cloud offerings -- Azure and BPOS/Office 365.  While the cloud does not represent a physical appliance (quite the opposite in fact) its ability to make acquisition, deployment and use of technology simple for the user is absolutely an embodiment of the appliance mentality and spirit.  Azure is primarily a platform as a service offering; it doesn’t just provide infrastructure.  SQL Azure does likewise for databases.  And Office 365 does likewise for SharePoint, Exchange and Lync. You don’t administer, tune and manage servers; instead, you create databases or site collections or mailboxes and start using them. Upgrades come automatically, and it seems like releases will come more frequently.  Fault tolerance and content distribution is just there.  No muss.  No fuss.  You use these services; you don’t have to set them up and think about them.  That’s how appliances work.  To me, these signs point out that Microsoft has the full capability of transforming itself.  But there’s a lot of work ahead.  Microsoft may say they’re “all in” on the cloud, but the majority of the company is still oriented around its old products and models.  There needs to be a wholesale cultural transformation in Redmond.  It can happen, but product management, program management, the field and executive ranks must unify in the effort. So must partners, and even customers.  New leaders must rise up and Microsoft must be able to see itself as a winner.  If Microsoft does this, it could lock-in decades of new success, and be a standard business school case study for doing so.  If not, the company will have missed an opportunity, and may see its undoing.

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  • Mathemagics - 3 consecutive number

    - by PointsToShare
    © 2011 By: Dov Trietsch. All rights reserved Three Consecutive numbers When I was young and handsome (OK, OK, just young), my father used to challenge us with riddles and tricks involving Logic, Math and general knowledge. Most of the time, at least after reaching the ripe age of 10, I would see thru his tricks in no time. This one is a bit more subtle. I had to think about it for close to an hour and then when I had the ‘AHA!’ effect, I could not understand why it had taken me so long. So here it is. You select a volunteer from the audience (or a shill, but that would be cheating!) and ask him to select three consecutive numbers, all of them 1 or 2 digits. So {1, 2, 3} would be good, albeit trivial set, as would {8, 9, 10} or {97, 98, 99} but not {99, 99, 100} (why?!). Now, using a calculator – and these days almost every phone has a built in calculator – he is to perform these steps: 1.      Select a single digit 2.      Multiply it by 3 and write it down 3.      Add the 3 consecutive numbers 4.      Add the number from step 2 5.      Multiply the sum by 67 6.      Now tell me the last 2 digits of the result and also the number you wrote down in step 2 I will tell you which numbers you selected. How do I do this? I’ll give you the mechanical answer, but because I like you to have the pleasure of an ‘AHA!’ effect, I will not really explain the ‘why’. So let’s you selected 30, 31, and 32 and also that your 3 multiple was 24, so here is what you get 30 + 31 + 32 = 93 93 + 24 = 117 117 x 67 = 7839, last 2 digits are 39, so you say “the last 2 digits are 39, and the other number is 24.” Now, I divide 24 by 3 getting 8. I subtract 8 from 39 and get 31. I then subtract 1 from this getting 30, and say: “You selected 30, 31, and 32.” This is the ‘how’. I leave the ‘why’ to you! That’s all folks! PS do you really want to know why? Post a feedback below. When 11 people or more will have asked for it, I’ll add a link to the full explanation.

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  • Mailing Lists Are Parties. Or They Should Be.

    <b>Luis Villa's Internet Home:</b> "I can&#8217;t go to bed because Mairin is right on the internet and so I want to (1) say she&#8217;s awesome and (2) add two cents on mailing lists and using the power of a web interface to make them better. Bear with me; maybe this is completely off-base (probably I should just stick to law), but it has been bouncing around in my head for years and maybe me writing it down will help the lightbulb go off for someone who can actually implement it :)"

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