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• Collision detection of convex shapes on voxel terrain

  - by Dave

  I have some standard convex shapes (cubes, capsules) on a voxel terrain. It is very easy to detect single vertex collisions. However, it becomes computationally expensive when many vertices are involved. To clarify, currently my algorithm represents a cube as multiple vertices covering every face of the cube, not just the corners. This is because the cubes can be much bigger than the voxels, so multiple sample points (vertices) are required (the distance between sample points must be at least the width of a voxel). This very rapidly becomes intractable. It would be great if there were some standard algorithm(s) for collision detection between convex shapes and arbitrary voxel based terrain (like there is with OBB's and seperating axis theorem etc). Any help much appreciated.

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• Silverlight Cream for December 08, 2010 -- #1005

  - by Dave Campbell

  In this Issue: Peter Kuhn, David Anson, Jesse Liberty, Mike Taulty(-2-, -3-), Kunal Chowdhury, Jeremy Likness, Martin Krüger, Beth Massi(-2-, -3-)/ Above the Fold: Silverlight: "Rebuilding the PDC 2010 Silverlight Application (Part 1)" Mike Taulty WP7: "WP7: Glossy text block custom control" Martin Krüger Lightswitch: "How to Create a Screen with Multiple Search Parameters in LightSwitch" Beth Massi From SilverlightCream.com: Requirements of and pitfalls in Windows Phone 7 serialization Peter Kuhn discusses Data Contract Serializer issuses on WP7 and how to work around them. Managed implementation of CRC32 and MD5 algorithms updated; new release of ComputeFileHashes for Silverlight, WPF, and the command-line! David Anson ties up some loose ends from a prior post on hash functions, and updates his CRC32 and MD5 algorithms. Windows Phone From Scratch #9 – Visual State Jesse Liberty's latest Windows Phone from Scratch tutorial up... and is on the Visual State... he extends a Button and codes up the State Transitions. Rebuilding the PDC 2010 Silverlight Application (Part 1) Mike Taulty has taken the time to rebuild the PDC2010 Silverlight App that folks wanted the source for... and he's taking multiple posts to explain the heck out of it. This first one is mostly infrastructure. Rebuilding the PDC 2010 Silverlight Application (Part 2) In the 2nd post of the series, Mike Taulty is handling the In/Out of Browser business because he eventually is going to be going OOB. Rebuilding the PDC 2010 Silverlight Application (Part 3) Part 3 finds Mike Taulty delving into WCF Data Services and getting some data on the screen. Paginating Records in Silverlight DataGrid using PagedCollectionView Kunal Chowdhury continues with his investigation of the PagedCollectionView with this post on Pagination of your data. Old School Silverlight Effects If you haven't seen Jeremy Likness' 'Old School' Effects page yet, go just for the entertainment... you'll find yourself hanging around for the code :) WP7: Glossy text block custom control Martin Krüger's latest post is a very cool custom control for WP7 that displays Glossy text... it ain't Metro, but it looks pretty nice... some of it almost like etched text. How to Create a Screen with Multiple Search Parameters in LightSwitch Looks like Beth Massi got a few Lightswitch posts in while I wasn't looking. First up is this one on a multiple-parameter search screen. Adding Static Images and Logos to LightSwitch Applications In the 2nd post, Beth Massi shows how to add your own static images and logos to Lightswitch apps... in response to reader questions. Getting the Most out of LightSwitch Summary Properties In her latest post, Beth Massi explains what Summary Properties are in Lightswitch and how to use them to get the best results for your users. 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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• Kent .Net/SqlServer User Group – Upcoming events

  - by Dave Ballantyne

  At the Kent user group we have two upcoming events.  Both are to be held at F-Keys Training suite http://f-keys.co.uk/ in Rochester, Kent. If you haven’t attended before please note the location here. 14-June Is your code S.O.L.I.D ? Nathan Gloyn Everybody keeps on about SOLID principles but what are they? and why should you care? This session is an introduction to SOLID and I'll aim to walk through each principle telling you about that principle and then show how a code base can be refactored using the principles to make your life easier, Come the end of the session you should have a basic understanding of the principle, why to use it and how using it can improve your code. Building composite applications with OpenRasta 3 Sebastien Lambla A wave of change is coming to Web development on .NET. Packaging technologies are bringing dependency management to .NET for the first time, streamlining development workflow and creating new possibilities for deployment and administration. The sky's the limit, and in this session we'll explore how open frameworks can help us leverage composition for the web. Register here for this event http://www.eventbrite.com/event/1643797643 05-July Tony Rogerson Achieving a throughput of 1.5Terabytes or over 92,000 8Kbyte of 100% random reads per second on kit costing less that 2.5K, and of course what to do with it! The session will focus on commodity kit and how it can be used within business to provide massive performance benefits at little cost. End to End Report Creation and Management using SQL Server Reporting Services  Chris Testa-O'NeillThis session will walk through the authoring, management and delivery of reports with a focus on the new features of Reporting Services 2008 R2. At the end of this session you will understand how to create a report in the new report designer. Be aware of the Report management options available and the delivery mechanisms that can be used to deliver reports. Register here for this event http://www.eventbrite.com/event/1643805667 Hope to see you at one or other ( or even both if you are that way inclined).

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• GIS-based data visualization and maintenance tool

  - by Dave Jarvis

  Background Looking to leverage an existing GIS system for exploring organizational data. Architecture The following figure represents a high-level overview of the system's desired features: The most basic usage would be as follows: The user visits a web site. The system presents a map (having regions, cities, and buildings). The user drills-down on the map to a particular building. The system provides a basic CRUD interface. The user can view and modify information about personnel (e.g., their assigned teams), equipment (e.g., network appliances), applications, and the building itself (e.g., contact and phone numbers). Ideally, all the components should be open-source (or otherwise free). Problem This must be a small project that needs a quick (but functional) prototype, mostly to confirm whether or not such a system would be useful in the long term. Questions What software components would you use to quickly develop a working prototype? What open-source solutions already exist, if any? Ideas Here is what I am thinking: PostGIS - Define the regions, cities, and sites Google Maps - Display an interactive, clickable map geoJSON - Protocol between PostGIS and Google Maps Seam - CRUD interface Custom Development For example, this would entail: Installation and configuration Configure SSH for remote logins Subversion (or git) PostgreSQL PostGIS Java Tomcat Seam JasperReports Enter GIS information into PostGIS Aggregate data sources into PostgreSQL database Develop starting page for map interface Develop clickable Google Maps interface Develop summary reports Develop CRUD interface using Seam for data maintenance Surely something like this already exists? Thank you!

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• Addicted to the MIX Buzz

  - by Dave Campbell

  Well it's the Friday before MIX10, and I'm officially of no use to anybody. I'll be driving up to 'Vegas Sunday ... hopefully rolling in mid-late afternoon, checking in at my $31.50/night (including WiFi) Motel, and getting registered then hanging out around registration to see who is there. First organized thing to do is 9PM, so I'm open to suggestions Sunday evening... maybe we can get a gang together for dinner ?? Monday is the Keynote ... I'm addicted to the buzz in the ballroom the first day, hope to be close to the front, trying to live blog. Then straight to Ballroom A and stake out the spot I'll be in for all 3 days, and you all know why :) I've tagged 40 sessions that I 'want' to see, and there's only 12 slots... damn... if I could, I'd try the Multiplicity thing, but I'm afraid I'd get the idiot first try -- or maybe got that one already :) ... but at least I tagged them to make it easy to find after the videos are up. Stuff going on Sunday, Monday, and Tuesday night. I'm staying over for an event on Thursday, and driving back on Friday. I'm not sure how much blogging I'll be doing, but I'll try to hit some 'Cream high spots. I'm sure everyone #NotAtMIX is going to be tuned into the sessions online. I'll be wearing TShirts with WynApse.com and SilverlightCream.com printed on the back... so if you see some old curmudgeon with such a shirt, IT'S ME! I look forward to seeing all the people I only see once or twice a year, and meeting ones I haven't met yet What a week... Bring It On and Stay in the 'Light! Technorati Tags: Silverlight    Silverlight 4    MIX10

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• Silverlight Cream for May 25, 2010 -- #869

  - by Dave Campbell

  In this Issue: Miroslav Miroslavov, Victor Gaudioso, Phil Middlemiss, Jonathan van de Veen, Lee, and Domagoj Pavlešic. From SilverlightCream.com: Book Folding effect using Pixel Shader On the new CompleteIT site, did you know the page-folding was done using PixelShaders? I hadn't put much thought into it, but that's pretty cool, and Miroslav Miroslavov has a blog post up discussing it, and the code behind it. New Silverlight Video Tutorial: How to create a Slider with a ToolTip that shows the Value of the Slider This is pretty cool... Victor Gaudioso's latest video tutorial shows how to put the slider position in the slider tooltip... code and video tutorial included. Backlighting a ListBox Put this in the cool category as well... Phil Middlemiss worked out a ListBox styling that makes the selected item be 'backlit' ... check out the screenshot on the post... and then grab the code :) Adventures while building a Silverlight Enterprise application part #33 Jonathan van de Veen is discussing changes to his project/team and how that has affected development. Read about what they did right and some of their struggles. RIA Services and Storedprocedures Lee's discussing Stored Procs and RIA Services ... he begins with one that just works, then moves on to demonstrate the kernel of the problem he's attacking and the solution of it. DoubleClick in Silverlight Domagoj Pavlešic got inspiration from one of Mike Snow's Tips of the Day and took off on the double-click idea... project source included. 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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• iPad Discussion

  - by Dave Campbell

  I had reason to meet up with someone I don't see very often a bit ago. In the course of the conversation, he told me he bought an iPad. I don't know if I was expected to ooh and ahh, but I didn't. After he finished saying how cool it was and how much he and his wife liked it, I commented "no Flash and no Silverlight" after which followed this: Him: "You don't need it, HTML5 can do everything Flash and Silverlight does" Me: "Wait... you're telling me that the iPad converts existing Flash content into HTML5 and then renders it?" Him: "No, but once all the existing sites are converted to HTML 5 it'll be fine and we don't need Flash... or Silverlight" 'all the existing sites' ... huh ... I didn't get a notice, maybe they're doing them alphabetically or something :) Ok Spanky... you keep drinking that Kool-Aide from Steve, I've got mine... it's blue with Silverlight:

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• SQL Server XML Schemas

  - by Dave Ballantyne

  Ever been curious about the schema of , say an SSRS rdl file ?  How about the execution plan ? Not only should you already have the .XSD files , check out the folder ‘Microsoft SQL Server\100\Tools\Binn\schemas\sqlserver’ , but they are also available online here. 

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• How do I properly use String literals for loading content?

  - by Dave Voyles

  I've been using verbatim string literals for some time now, and never quite thought about using a regular string literal until I started to come across them in Microsoft provided XNA samples. With that said, I'm trying to implement a new AudioManager class from the Net Rumble sample. I have two (2) issues here: Question 1: In my code for my GameplayScreen screen I have a folder location written as the following, and it works fine: menuButton = content.Load<SoundEffect>(@"sfx/menuButton"); menuClose = content.Load<SoundEffect>(@"sfx/menuClose"); If you notice, you'll see that I'm using a verbatim string, with a forward slash "/". In the AudioManager class, they use a regular string literal, but with two backslashes "\". I understand that one is used as an escape, but why are they BACK instead of FORWARD? (See below) soundList[soundName] = game.Content.Load<SoundEffect>("audio\\wav\\"+ soundName); Question 2: I seem to be doing everything correctly in my AudioManager class, but I'm not sure of what this line means: audioFileList = audioFolder.GetFiles("*.xnb"); I suppose that the *xnb means look for everything BUT files that end in *xnb? I can't figure out what I'm doing wrong with my file locations, as the sound effects are not playing. My code is not much different from what I've linked to above. private AudioManager(Game game, DirectoryInfo audioDirectory) : base(game) { try { audioFolder = audioDirectory; audioFileList = audioFolder.GetFiles("*.mp3"); soundList = new Dictionary<string, SoundEffect>(); for (int i = 0; i < audioFileList.Length; i++) { string soundName = Path.GetFileNameWithoutExtension(audioFileList[i].Name); soundList[soundName] = game.Content.Load<SoundEffect>(@"sfx\" + soundName); soundList[soundName].Name = soundName; } // Plays this track while the GameplayScreen is active soundtrack = game.Content.Load<Song>("boomer"); } catch (NoAudioHardwareException) { // silently fall back to silence } }

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• Silverlight Cream for November 27, 2011 -- #1176

  - by Dave Campbell

  In this Issue: Matt Eland, Parag Joshi, Jerrel Blankenship, and Joost van Schaik. Above the Fold: WP7: "Safe event detachment base class for Windows Phone 7 behaviors" Joost van Schaik Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up From SilverlightCream.com:31 Days of Mango | Day #22: App ConnectMatt Eland takes the reigns of Jeff's blog for Day 22 and is talking about App Connect... App Connect allows apps to be listed on Quick Cards relative to an app's subject matter, and Quick Cards are items that appear in searches to let users find out more info... check out the blog post if you're not familiar with this31 Days of Mango | Day #21: SocketsJeff's Day 21 is written by Parag Joshi, and is on sockets... and is building a WP7 app for posting restaurant orders to a Silverlight OOB app running on a host machine... good sized tutorial and discussion, plus a project to download and play with31 Days of Mango | Day #20: Creating RingtonesJerrel Blankenship has Day 20 for Jeff Blankenburg's 31 Days of Mango and is discussing Ringtones... how to create and save a custom ringtone for your userSafe event detachment base class for Windows Phone 7 behaviorsJoost van Schaik revisits his Safe Event Detachment pattern for WP7 and built a base class to take care of the initialization involved to be kind to us, the developers... code includedStay in the 'Light!Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCreamJoin me @ SilverlightCream | Phoenix Silverlight User GroupTechnorati Tags:Silverlight    Silverlight 3    Silverlight 4    Windows PhoneMIX10

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• To Serve Man?

  - by Dave Convery

  Since the announcement of Windows 8 and its 'Metro' interface, the .NET community has wondered if the skills they've spent so long developing might be swept aside,in favour of HTML5 and JavaScript. Mercifully, that only seems to be true of SilverLight (as Simon Cooper points out), but it did leave me thinking how easy it is to impose a technology upon people without directly serving their needs. Case in point: QR codes. Once, probably, benign in purpose, they seem to have become a marketer's tool for determining when someone has engaged with an advert in the real world, with the same certainty as is possible online. Nobody really wants to use QR codes - it's far too much hassle. But advertisers want that data - they want to know that someone actually read their billboard / poster / cereal box, and so this flawed technology is suddenly everywhere, providing little to no value to the people who are actually meant to use it. What about 3D cinema? Profits from the film industry have been steadily increasing throughout the period that digital piracy and mass sharing has been possible, yet the industry cinema chains have forced 3D films upon a broadly uninterested audience, as a way of providing more purpose to going to a cinema, rather than watching it at home. Despite advances in digital projection, 3D cinema is scarcely more immersive to us than were William Castle's hoary old tricks of skeletons on wires and buzzing chairs were to our grandparents. iTunes - originally just a piece of software that catalogued and ripped music for you, but which is now multi-purpose bloatware; a massive, system-hogging behemoth. If it was being built for the people that used it, it would have been split into three or more separate pieces of software long ago. But as bloatware, it serves Apple primarily rather than us, stuffed with Music, Video, Various stores and phone / iPad management all bolted into one. Why? It's because, that way, you're more likely to bump into something you want to buy. You can't even buy a new laptop without finding that a significant chunk of your hard drive has been sold to 'select partners' - advertisers, suppliers of virus-busting software, and endless bloatware-flogging pop-ups that make using a new laptop without reformatting the hard drive like stepping back in time. The product you want is not the one you paid for. This is without even looking at services like Facebook and Klout, who provide a notional service with the intention of slurping up as much data about you as possible (in Klout's case, whether you create an account with them or not). What technologies do you find annoying or intrusive, and who benefits from keeping them around?

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• Visual Studio 2010 Short Cut Links!

  - by Dave Noderer

  This week Scott Cate came to South Florida and gave a great talk on his Visual Studio shortcuts and how he uses them. You can find a collection of short video’s he has done at: http://scottcate.com/tricks/ Also you might want to check out Sara Ford’s blog: http://blogs.msdn.com/saraford/default.aspx, she started doing a tip a day but has many more now. Scott covers many of these in the videos. And.. as with past releases, the languages team has provided PDF’s with a lot of keyboard shortcuts, this time for VB, C#, F# and C++. You can find downloads for all of these at the top of the FlaDotNet.com page and are included below: VB: http://www.fladotnet.com/downloads/VS2010VB.pdf C#: http://www.fladotnet.com/downloads/VS2010CSharp.pdf F#: http://www.fladotnet.com/downloads/VS2010FSharp.pdf C++: http://www.fladotnet.com/downloads/VS2010CPP.pdf Happy Keyboarding!!

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• First time android game development [on hold]

  - by Dave

  My friend and i are developing a android game. This is my first time develop android game, so we don't know how to code The game is 2d game and we develop it without 3rd party engine / framework. Now we got a few questions, hope you can help us. In game play, using 'Surfaceview' only to achieve it. Is it best practice? On 'Surfaceview', a lot of difference button(Menu, pause, game object..etc) is on it, but I don't know how to code it? (actually, i have already done, but...so stupid way. Detect the user touch position (x, y) to identify where they touch[rect(x1,y1,x2,y2).contain(x,y)] Is it right? Teach me how to do if wrong. View / Surfaceview / OpenGL, which is suitable for us? (if like Tetris) Thank you for your help. Ps: My english is not good, hope you can understand what i mean.

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• How can a large, Fortran-based number crunching codebase be modernized?

  - by Dave Mateer

  A friend in academia asked me for advice (I'm a C# business application developer). He has a legacy codebase which he wrote in Fortran in the medical imaging field. It does a huge amount of number crunching using vectors. He uses a cluster (30ish cores) and has now gone towards a single workstation with 500ish GPUS in it. However where to go next with the codebase so: Other people can maintain it over next 10 year cycle Get faster at tweaking the software Can run on different infrastructures without recompiles After some research from me (this is a super interesting area) some options are: Use Python and CUDA from Nvidia Rewrite in a functional language. For example, F# or Haskell Go cloud based and use something like Hadoop and Java Learn C What has been your experience with this? What should my friend be looking at to modernize his codebase? UPDATE: Thanks @Mark and everyone who has answered. The reasons my friend is asking this question is that it's a perfect time in the projects lifecycle to do a review. Bringing research assistants up to speed in Fortran takes time (I like C#, and especially the tooling and can't imagine going back to older languages!!) I liked the suggestion of keeping the pure number crunching in Fortran, but wrapping it in something newer. Perhaps Python as that seems to be getting a stronghold in academia as a general-purpose programming language that is fairly easy to pick up. See Medical Imaging and a guy who has written a Fortran wrapper for CUDA, Can I legally publish my Fortran 90 wrappers to Nvidias' CUFFT library (from the CUDA SDK)?.

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• No keyboard input until after GRUB

  - by Dave M G

  I have a computer that I dual boot between Ubuntu 11.10 and Windows 7. I installed Windows first, and Ubuntu second. When I boot, the GRUB menu comes up, showing me the option to select to boot to Ubuntu at the top of the list, and to boot to Windows at the bottom. Unfortunately, as far as I can tell, any key I press on the keyboard (connected by USB) does not get any response, so I can't actually select to boot to anything but Ubuntu (which is the default selection). Once Ubuntu loads and I am at the log in screen, then the keyboard (and mouse) work perfectly normally thereafter. Why would my keyboard not work only during GRUB? And how do I fix it?

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• Silverlight Cream Monday WP7 App Review # 1

  - by Dave Campbell

  I'm going to try something here... if it seems useful, I'll continue, if it doesn't, I'll stop... so give me feedback! There are *lots* of Apps in the WP7 Marketplace, and heaven help me, but the Marketplace sucks for finding stuff. I won't rehash what's already been said in the blogs, but I agree with one and all. I went out last Saturday to find 2 apps that I knew were released, and couldn't do so on my device. Even in the Zune app, it took quite a while to find them... ok, I'll back off a bit, because I just found out I can do 'Search' now if I know the name... I didn't think that was working before. So my thought is on Monday (like today), I will post a review of 5 apps/games I either use or have played with on my device. These are strictly my opinions, you understand, but hey... it's better than a poke in the eye with an iPhone! A few disclaimers:     Feel free to write me about your app and tell me about it. While it would be very cool to receive a whole bunch of xap files to review, at this point, for technical reasons, I'm unable to side-load my device. Since I plan on only doing this one day a week, and only 5, I may never get caught up, so if you send me some info, be patient. Re: games ... remember I'm old... I'm from the era of Colossal Cave and Zork. Duke-Nukem 2D and Captain Comic were awesome. I don't own an XBOX or any other game system, so take game reviews from my perspective -- who knows, it may be refreshing :) I won't pay for an app or game just to try it. If you expect me to test-drive your app, it's going to have to have a Free Trial. In this Issue:   Jingo! is the first app I bought, just to see what the experience was like. It's very much like a game we used to play in school in the Army in 1971 on paper we passed around. Sort of a cross between hangman and Mastermind, you try to figure out the hidden word in 5 tries. You get really good at 5-letter words after a while. I like this because you have to think, and you're not pressured by a clock Jingo! is by James Furdell and is $1.99 I reviewed René Schulte's Pictures Lab a while back, and have not changed my mind. This is an excellent app for playing with any photo on your device... one you've just taken, one you've synced from your PC, or one you've saved from email. I like this because you can get some cool effects for your photos, and it just works. Pictures Lab is by Schulte Software Development and is $1.99 Since I work as a consultant, and from home, I wanted something I could track my time with. I've test-driven all the contenders I could find so far on the phone, and so far I like ONTRACK! the best. If asked, I have some suggestions, but it's probably just the way I work or think. What I do like is I can tap a project to start/stop/restart a counter, and at the end of the day it shows me how much time I've been working. If there's a way to make an adjustment in case you forget to tap the counter, I don't know how to do it, and that's my biggest complaint. I like this because you can get a daily readout which you can also email as a spreadsheet. The daily results display is very good. ONTRACK! is by Qmino and is $2.99 Remember Item 4 above... I've been playing guitar for 48 years... obviously since before the invention of 'tuners', so I'm not as dependent upon these as some folks are. I've tried some in the past and have always felt I can do just as good by ear (I have perfect relative pitch). So, I gave this app by András Velvárt a dance just to see how it works, and it is surprisingly good. If you're used to one of the stage tuners this may take a little getting used to, but it does the job. The difference with this one is there is no real 'null' point inside which you can think your guitar is in tune. The soundwave stays visible on the device, and if it's moving to the right, your string is flat, if it's moving to the left, your string is sharp. Getting it exact might be tricky, but it is exact! If you need to rely on a tuner, this is a good choice in my opinion, exactly because of the sensitivity.. tune up with this and you're dead-on. Guitar Tuner is by Kinabalu Innovation Limited and is $0.99 Popper 2 is the WP7 version of a wildly popular game by Bill Reiss named Dr. Popper. You can get a trial, or you can now get a free lite version of the game. Popper 2 is a fast-paced bubble breaker game. I find it something fun to play when I just want to buzz out, but maybe the best review is that my daughter didn't want to give my phone back when I showed it to her, and always wants to grab my phone to play 'that game'. A fun distraction with great graphics and a great price Popper 2 is by Blue Rose Systems, LLC and is $1.29 Let me know what you think of the idea of doing reviews, or the layout/whatever, and 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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• Cross Apply Ambiguity

  - by Dave Ballantyne

  Cross apply (and outer apply)  are a very welcome addition to the TSQL language.  However, today after a few hours of head scratching, I have found an simple issue which could cause big big problems. What would you expect from this statement ? select * from sys.objects b join sys.objects a on a.object_id = object_id No prizes for guessing SQL server errors with “Ambiguous column name 'object_id'”. What would you expect from this statement ? Select * from sys.objects a cross apply( Select * from sys.objects b where b.object_id = object_id) as c Surprisingly, perhaps, the result is a cross join of sys.objects.  Well, what happened there ? If you look at the apply statement, within the where clause, only one of the conditions is qualified with a table name.  This meant that is has be interpreted as “b.object_id = b.object_id” causing the cross apply to have no join the the parent sys.objects table and causing the cross join. The fix is , obviously, simple Select * from sys.objects a cross apply( Select * from sys.objects b where b.object_id = a.object_id) as c So why no “Ambiguous column name ” error ?  I’ve raised a connect item on this issue here.

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• Google analytics and Adwords showing very different figures

  - by Dave Rook

  In AdWords I have 1 advert running only. The landing page includes a querystring so I can track it. EG, www.mydomain.com/products?source=CPC I also use Google Analytics. For February I have approx 1450 clicks in AdWords. This means, 1450 went to my website. In Google Analytics, according to my landing page, there were only ~850 visits. In Google Analytics, in the Acquisition - All traffic page, it suggests that Google CPC brought 517 visits... I know tracking tools are not 100% reliable but this figure seems to be showing something is very wrong. How can I tell which of the figures is accurate or is this just a limitation of reporting tools?

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• Polite busy-waiting with WRPAUSE on SPARC

  - by Dave

  Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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• SilverlightShow for 06-12 Dec 2010

  - by Dave Campbell

  In an effort to get some synergy in the Silverlight community, the SilverlightShow folks and I have decided to share some information. As always, I'm running a bit behind, so I get to post first with the material they provided to me :) Check out the five most popular news at SilverlightShow for last week (06 - 12 Dec 2010). The news that hit the top is the announcement for the upcoming SilverlightShow webinar with Gill Cleeren [which I posted about a couple weeks ago] (check other webinars Gill delivered for SilverlightShow) and the free Telerik license given away to attendees. Michael Crump's digest of Silverlight 5 news announced at Firestarter was the next most attention-grabbing news. Here is SilverlightShow's weekly top 5: Join our next webinar and win a license for Telerik RadControls for Silverlight Silverlight 5 - What's New (Including Screenshots & Code Snippets) Glossy TextBlock Custom Control For Windows Phone WP7 development vs iOS, Android and mobile Web Silverlight Simple Drag And Drop / Or Browse View Model / MVVM File Upload Control Visit and bookmark SilverlightShow... they've got a lot of good things happening over there. Stay in the 'Light

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• Activist shared printing material gallery

  - by Dave

  What would you say would be the best way to do this: We would like to create a section on our activist community FB page and website in order to share with everyone images and files ready for printing panflets, brochures, t-shirts, stickers, etc. Let's say we have some cool slogans for t-shirts, so we would like to show them on a gallery, and offer for download the original design files needed for a print shop to create the t-shirts. And the same thing for all other kinds of media. We want to enable anyone to be able to just download the files for free, and easily create printed materials with them. But besides offering this hybrid between picture gallery and downloads manager, we would also like to make it very easy for anyone to upload and share their own files with the community, to make it a true collaboration initiative, be it that they get posted automatically, or that we first review and approve all uploads. Cafepress or Spreadshirt let you upload your design and sell your own merchandise. We need something similar, but where people can then download working files for making quality printings and materials. What apps, tools, services or methods are out there with which you think this could be best done?? We have some ideas, but we would like to hear some more!!

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• I&rsquo;m back, now with Windows Live Writer goodness

  - by Dave Yasko

  I’ve reimaged my home laptop.  I’m trying to populate it with as much free goodness as possible to see if the free way is as good as the old pay way.  Turns out, I’ve got access to Windows Live Writer.  I’m not sure where that came from, maybe with Vista Ultimate.  I don’t know.  Either way, it makes my blog posting a whole lot easier.  So, maybe, just maybe, it will make me more likely to post.  We’ll see. Later.

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• Why does my system use so much cache?

  - by Dave M G

  Previously, on my desktop computer running Ubuntu 14.04, I had 4GB RAM, which I thought should be plenty. However, after being on for a while, my computer would seem to get slow. I have a system resource monitor app in my Gnome panel, which I assume represents the available RAM (?). It shows a dark green area as being "Memory", and a light green area as "Cache". The "Cache" would slowly grow until it filled the whole graph, and then programs would get slow to load, or it would take a while to switch programs. I could alleviate the problem somewhat with this command, but eventually the computer cache fills up again, so it's only a bandaid: sudo sh -c "sync; echo 3 > /proc/sys/vm/drop_caches" So, I figured I'd get more RAM, so I replaced one 2GB stick with an 8GB stick, and now I have 10 GB ram. And my "cache" still slowly maxes out and my computer slows as a result. Also, sometimes the computer starts out with "cache" maxed when I first boot and log in. Not always though, I don't know if there's a pattern that determines why it happens. Why is Ubuntu using up so much cache? Is 10GB not enough for Ubuntu? Here's what my system monitor looks like in my Gnome panel. The middle square shows RAM usage. The light green area is the "cache": This is my memory and swap history, which doesn't seem to include any information about "cache". I realize at this point I'm not totally clear on the difference between "cache" and "swap":

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• How do I turn on wireless adapter on HP Envy dv6 7200 under Ubuntu (any version)?

  - by Dave B.

  I have a new HP Envy dv6 7200 with dual boot Windows 8 / Ubuntu 12.04. In windows, the F12 key in Windows activates the "airplane mode" switch which enables/disables both on-board (mini PCIe) and USB wireless adapters. In Ubuntu, however, the wireless adapter is turned off by default and cannot be turned back on via the F12 key (or any other combination of F12 and Ctrl, Fn, Shift, etc.). Let me explain the "fixes" I've seen in various forums and explain what did or did not happen. These are listed in no particular order. (Spoiler alert: wireless is still broke). Solution 1? Use HP's "Wireless Assistant" utility to permanently activate the wireless card in Windows, then boot into Ubuntu to happily find it working. Unfortunately, this utility works in Windows 7 but not Windows 8. On the other hand, hardware drivers from HP are only available for Windows 8 for this model. Catch 22 (I could not find a comparable utility for Windows 8). Solution 2? Use a USB wireless adapter to sidestep the on-board device. I purchased such a device from thinkpenguin.com to be sure that it would be Linux-friendly. However, the wireless switch enables / disables all wireless devices including USB. So, there's my $50 donation to the nice folks at thinkpenguin.com, but still no solution. Solution 3? Following the Think Penguin folk's suggestion, modify the mini PCI express adapter following instructions here: http://www.notebookforums.com/t/225429/broken-wireless-hardware-switch-fix Tempting, but I then violate the terms of my warranty mere days after opening the box. This might be a good solution for an older machine that you want to get your geek on with, but not for a new box. Solution 4? rfkill unblock all No effect whatsoever. ubuntu@ubuntu-hp-evny:~$ rfkill unblock all ubuntu@ubuntu-hp-evny:~$ rfkill list all 0: hp-wifi: Wireless LAN Soft blocked: no Hard blocked: yes Solution 5? Re-install drivers. Done and done. Ubuntu recognizes the device - perhaps even without re-installing the drivers? - but cannot turn it on. How do I know this? In the Network Manager drop-down menu, the wireless option is blacked out and a message reads something like: "wireless network is disabled by a hardware switch". Solution 6? Identify a physical switch on the laptop and flip it. There is no such switch on this machine. In fact, walking through Best Buy yesterday, I checked and not a single new laptop PC had a physical switch on it. All of the wireless switches are either the F2 or F12 key ... I wonder if askubuntu will not be plagued by this exact issue in the near future? Additional info - lspci ubuntu@ubuntu-hp-evny:~$ lspci 00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09) 00:01.0 PCI bridge: Intel Corporation Ivy Bridge PCI Express Root Port (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Ivy Bridge Graphics Controller (rev 09) 00:14.0 USB controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04) 00:1a.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4) 00:1c.2 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 3 (rev c4) 00:1c.3 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 4 (rev c4) 00:1c.5 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 6 (rev c4) 00:1d.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04) 00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04) 00:1f.2 RAID bus controller: Intel Corporation 82801 Mobile SATA Controller [RAID mode] (rev 04) 00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04) 01:00.0 VGA compatible controller: NVIDIA Corporation Device 0de9 (rev a1) 08:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. Device 5229 (rev 01) 0a:00.0 Network controller: Ralink corp. Device 539b 0b:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 07) Any suggestions would be much appreciated!

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• NUMA-aware placement of communication variables

  - by Dave

  For classic NUMA-aware programming I'm typically most concerned about simple cold, capacity and compulsory misses and whether we can satisfy the miss by locally connected memory or whether we have to pull the line from its home node over the coherent interconnect -- we'd like to minimize channel contention and conserve interconnect bandwidth. That is, for this style of programming we're quite aware of where memory is homed relative to the threads that will be accessing it. Ideally, a page is collocated on the node with the thread that's expected to most frequently access the page, as simple misses on the page can be satisfied without resorting to transferring the line over the interconnect. The default "first touch" NUMA page placement policy tends to work reasonable well in this regard. When a virtual page is first accessed, the operating system will attempt to provision and map that virtual page to a physical page allocated from the node where the accessing thread is running. It's worth noting that the node-level memory interleaving granularity is usually a multiple of the page size, so we can say that a given page P resides on some node N. That is, the memory underlying a page resides on just one node. But when thinking about accesses to heavily-written communication variables we normally consider what caches the lines underlying such variables might be resident in, and in what states. We want to minimize coherence misses and cache probe activity and interconnect traffic in general. I don't usually give much thought to the location of the home NUMA node underlying such highly shared variables. On a SPARC T5440, for instance, which consists of 4 T2+ processors connected by a central coherence hub, the home node and placement of heavily accessed communication variables has very little impact on performance. The variables are frequently accessed so likely in M-state in some cache, and the location of the home node is of little consequence because a requester can use cache-to-cache transfers to get the line. Or at least that's what I thought. Recently, though, I was exploring a simple shared memory point-to-point communication model where a client writes a request into a request mailbox and then busy-waits on a response variable. It's a simple example of delegation based on message passing. The server polls the request mailbox, and having fetched a new request value, performs some operation and then writes a reply value into the response variable. As noted above, on a T5440 performance is insensitive to the placement of the communication variables -- the request and response mailbox words. But on a Sun/Oracle X4800 I noticed that was not the case and that NUMA placement of the communication variables was actually quite important. For background an X4800 system consists of 8 Intel X7560 Xeons . Each package (socket) has 8 cores with 2 contexts per core, so the system is 8x8x2. Each package is also a NUMA node and has locally attached memory. Every package has 3 point-to-point QPI links for cache coherence, and the system is configured with a twisted ladder "mobius" topology. The cache coherence fabric is glueless -- there's not central arbiter or coherence hub. The maximum distance between any two nodes is just 2 hops over the QPI links. For any given node, 3 other nodes are 1 hop distant and the remaining 4 nodes are 2 hops distant. Using a single request (client) thread and a single response (server) thread, a benchmark harness explored all permutations of NUMA placement for the two threads and the two communication variables, measuring the average round-trip-time and throughput rate between the client and server. In this benchmark the server simply acts as a simple transponder, writing the request value plus 1 back into the reply field, so there's no particular computation phase and we're only measuring communication overheads. In addition to varying the placement of communication variables over pairs of nodes, we also explored variations where both variables were placed on one page (and thus on one node) -- either on the same cache line or different cache lines -- while varying the node where the variables reside along with the placement of the threads. The key observation was that if the client and server threads were on different nodes, then the best placement of variables was to have the request variable (written by the client and read by the server) reside on the same node as the client thread, and to place the response variable (written by the server and read by the client) on the same node as the server. That is, if you have a variable that's to be written by one thread and read by another, it should be homed with the writer thread. For our simple client-server model that means using split request and response communication variables with unidirectional message flow on a given page. This can yield up to twice the throughput of less favorable placement strategies. Our X4800 uses the QPI 1.0 protocol with source-based snooping. Briefly, when node A needs to probe a cache line it fires off snoop requests to all the nodes in the system. Those recipients then forward their response not to the original requester, but to the home node H of the cache line. H waits for and collects the responses, adjudicates and resolves conflicts and ensures memory-model ordering, and then sends a definitive reply back to the original requester A. If some node B needed to transfer the line to A, it will do so by cache-to-cache transfer and let H know about the disposition of the cache line. A needs to wait for the authoritative response from H. So if a thread on node A wants to write a value to be read by a thread on node B, the latency is dependent on the distances between A, B, and H. We observe the best performance when the written-to variable is co-homed with the writer A. That is, we want H and A to be the same node, as the writer doesn't need the home to respond over the QPI link, as the writer and the home reside on the very same node. With architecturally informed placement of communication variables we eliminate at least one QPI hop from the critical path. Newer Intel processors use the QPI 1.1 coherence protocol with home-based snooping. As noted above, under source-snooping a requester broadcasts snoop requests to all nodes. Those nodes send their response to the home node of the location, which provides memory ordering, reconciles conflicts, etc., and then posts a definitive reply to the requester. In home-based snooping the snoop probe goes directly to the home node and are not broadcast. The home node can consult snoop filters -- if present -- and send out requests to retrieve the line if necessary. The 3rd party owner of the line, if any, can respond either to the home or the original requester (or even to both) according to the protocol policies. There are myriad variations that have been implemented, and unfortunately vendor terminology doesn't always agree between vendors or with the academic taxonomy papers. The key is that home-snooping enables the use of a snoop filter to reduce interconnect traffic. And while home-snooping might have a longer critical path (latency) than source-based snooping, it also may require fewer messages and less overall bandwidth. It'll be interesting to reprise these experiments on a platform with home-based snooping. While collecting data I also noticed that there are placement concerns even in the seemingly trivial case when both threads and both variables reside on a single node. Internally, the cores on each X7560 package are connected by an internal ring. (Actually there are multiple contra-rotating rings). And the last-level on-chip cache (LLC) is partitioned in banks or slices, which with each slice being associated with a core on the ring topology. A hardware hash function associates each physical address with a specific home bank. Thus we face distance and topology concerns even for intra-package communications, although the latencies are not nearly the magnitude we see inter-package. I've not seen such communication distance artifacts on the T2+, where the cache banks are connected to the cores via a high-speed crossbar instead of a ring -- communication latencies seem more regular.

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