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IRQ Conflicts Causing Video Card and Boot Problems?

- by sanpatricio

tl;dr - I have 4 devices sharing 1 IRQ. Is this bad and how do I tell the BIOS to stop it? Background: I have an old Dell GX280 dual Pentium 4 that I (semi) resurrected last weekend with an installation of Ubuntu 12.04. Everything was going fine the first several hours until a problem that plagued me when WinXP was on that machine happened -- it froze. Completely froze. None of the myriad of ways I have found here on askubuntu helped me to regain control except a long-press of the power button to shut it off. Clearly, this wasn't a software/WinXP issue. After much googling, I found that hardware conflicts can often cause this sort of total lock-up and with all the odd blocks of yellow and flecks of color showing on my screen (both WinXP and Ubuntu) I figured my old GeForce 7600 was failing and causing me these odd issues. (A good canned-air dusting of the entire interior fixed the color fleck problem) Again, through much googling and numerous answers found on askubuntu, I somehow stumbled my way onto the lshw command. After going through it, line by line, I found that I have four devices sharing IRQ 16: eth0, wlan0, ide0 (DVD-RW), and my video card. In hindsight, I can recall weird instances of my Ethernet connection to another computer not working when I thought it should. I never full troubleshot those issues so it could be a coincidence. The other thing that has been plaguing me since installing Ubuntu (wasn't there during WinXP) has been periodic moments of my monitor getting no signal from Ubuntu during boot. The first couple days, it would disappear after the Dell boot screen and reappear at Ubuntu login. Now, it disappears after the Dell boot screen and doesn't return at all -- I have to hit F12 where I can load a safe mode version of Ubuntu and get more details like dmesg and lsdev. I also ran memtest86 overnight and woke up to zero errors, so failing RAM is out. Where do I go from here?

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Tracking Outgoing Links With Google Analytics Events

- by the_archer

I've been trying to track clicks on external links on my website using the events tracking method. So I've got my Google Analytics code setup before body ends as shown below (note: quotes have been entitied by blogger, but it works fine): <script type='text/javascript'> var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-XXXXXXX-X#39;]); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); </script> Now I wanted to track a link on the addthis.com follow widget. So there is a link of the type below to which following instructions from here I added the onclick event. <a addthis:url='http://feeds.feedburner.com/myfeedburnerlurl' onClick="_gaq.push(['_trackEvent', 'Subscription Clicks', 'RSS']);" class='addthis_button_rss_follow'/> I clicked on it a couple of times, left it for over a day now, but nothing shows up in google analytics events. It just says zero events. Here's a screenshot of the events page on GA: Could anybody help me? Am I doing anything wrong?

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64kb limit on the size of MSMQ Multicast Messages

- by John Breakwell

When Windows 2003 came out, Microsoft introduced the ability to broadcast messages to any machines that were listening back. All you had to do was send out a message on a particular port and IP address and any client that had set up a Multicast queue with matching port and IP address would get a copy. Since its introduction, there have been a couple of security vulnerabilities that needed to be removed: Microsoft Security Bulletin MS06-052 Vulnerability in Pragmatic General Multicast (PGM) Could Allow Remote Code Execution (919007) Microsoft Security Bulletin MS08-036 Vulnerabilities in Pragmatic General Multicast (PGM) could allow denial of service (950762) The second of these, MS08-036, was resolved through an undocumented change in functionality. Basically, a limit of 64kb was put on the maximum size of a message that could be broadcast using the Multicast method. Obviously this has caused a few problems for any existing MSMQ Multicast applications that expected to be able to send larger messages. A hotfix has been developed to resolve this problem. 961605 FIX: Multicast messages larger than 64 kilobytes (KB) are not delivered as expected by using Message Queuing 3.0 after security update MS08-036 is installed A registry change is required: Open the registry with Regedit Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RMCAST\Parameters\ Create a DWord called MaxpacketSize Set the value to the desired number of bytes. You can set it to a value between zero and 4MB. If you specify anything above 4MB, it will default to 64K. A reboot is needed after adding this value.

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The last word on C++ AMP...

- by Daniel Moth

Well, not the last word, but the last blog post I plan to do here on that topic. Over the last 12 months, I have published 45 blog posts related to C++ AMP on the Parallel Programming in Native Code, and the rest of the team has published even more. Occasionally I'll link to some of them from my own blog here, but today I decided to stop doing that - so if you relied on my personal blog pointing you to C++ AMP content, it is time you subscribed to the msdn blog. I will continue to blog about other topics here of course, so stay tuned. So, for the last time, I encourage you to read the latest two blog posts I published on the team blog bringing together essential reading material on C++ AMP Learn C++ AMP - a collection of links to take you from zero to hero. Present on C++ AMP - a walkthrough on how to give a presentation including slides. Got questions on C++ AMP? Hit the msdn forum! Comments about this post by Daniel Moth welcome at the original blog.

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I'm doing 90% maintenance and 10% development, is this normal?

- by TiredProgrammer

I have just recently started my career as a web developer for a medium sized company. As soon as I started I got the task of expanding an existing application (badly coded, developed by multiple programmers over the years, handles the same tasks in different ways, zero structure) So after I had successfully extended this application with the requested functionality, they gave me the task to fully maintain the application. This was of course not a problem, or so I thought. But then I got to hear I wasn't allowed to improve the existing code and to only focus on bug fixes when a bug gets reported. From then on I have had 3 more projects just like the above, that I now also have to maintain. And I got 4 projects where I was allowed to create the application from scratch, and I have to maintain those as well. At this moment I'm slightly beginning to get crazy from the daily mails of users (read managers) for each application I have to maintain. They expect me to handle these mails directly while also working on 2 other new projects (and there are already 5 more projects lined up after those). The sad thing is I have yet to receive a bug report on anything that I have coded myself, for that I have only received the occasional lets do things 180 degrees different change requests. Anyway, is this normal? In my opinion I'm doing the work equivalent of a whole team of developers. Was I an idiot when I initially expected things to be different? I guess this post has turned into a big rant, but please tell me that this is not the same for every developer. P.S. My salary is almost equal if not lower then that of a cashier at a supermarket.

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Visually and audibly unambiguous subset of the Latin alphabet?

- by elliot42

Imagine you give someone a card with the code "5SBDO0" on it. In some fonts, the letter "S" is difficult to visually distinguish from the number five, (as with number zero and letter "O"). Reading the code out loud, it might be difficult to distinguish "B" from "D", necessitating saying "B as in boy," "D as in dog," or using a "phonetic alphabet" instead. What's the biggest subset of letters and numbers that will, in most cases, both look unambiguous visually and sound unambiguous when read aloud? Background: We want to generate a short string that can encode as many values as possible while still being easy to communicate. Imagine you have a 6-character string, "123456". In base 10 this can encode 10^6 values. In hex "1B23DF" you can encode 16^6 values in the same number of characters, but this can sound ambiguous when read aloud. ("B" vs. "D") Likewise for any string of N characters, you get (size of alphabet)^N values. The string is limited to a length of about six characters, due to wanting to fit easily within the capacity of human working memory capacity. Thus to find the max number of values we can encode, we need to find that largest unambiguous set of letters/numbers. There's no reason we can't consider the letters G-Z, and some common punctuation, but I don't want to have to go manually pairwise compare "does G sound like A?", "does G sound like B?", "does G sound like C" myself. As we know this would be O(n^2) linguistic work to do =)...

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Simple algorithm for a sudoku solver java

- by user142050

just a quick note first, I originally asked this question on stack overflow but was refered here instead. I've been stuck on this thing for a while, I just can't wrap my head around it. For a homework, I have to produce an algorithm for a sudoku solver that can check what number goes in a blank square in a row, in a column and in a block. It's a regular 9x9 sudoku and I'm assuming that the grid is already printed so I have to produce the part where it solves it. I've read a ton of stuff on the subject I just get stuck expressing it. I want the solver to do the following: If the value is smaller than 9, increase it by 1 If the value is 9, set it to zero and go back 1 If the value is invalid, increase by 1 I've already read about backtracking and such but I'm in the early stage of the class so I'd like to keep it as simple as possible. I'm more capable of writing in pseudo code but not so much with the algorithm itself and it's the algorithm that is needed for this exercise. Thanks in advance for your help guys.

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Unsure about TRIM enabled on my SSD

- by user84750

I have a SSD OCZ Vertex4 installed on my laptop. I'm running Ubuntu 12.04 LTS. I have enable TRIM by adding "discard" to my fstab file. (also added option noatime). I rebooted my Ubuntu and followed These instructions here to test TRIM. The end results of my tempfile was all ffff's, when it should have read all zero's, which is telling me TRIM is not really working or enabled correctly. Did I miss something? Also, will it be a problem if only my /home directory is encrypted. AND if you ask why I have swap on my SSD, it's because I let Ubuntu set up my partition. When I have my SSD, I just wanted to install Ubuntu as fast as possible. =) I've done testing to see at which point it will start to use swap and it took a lot of applications open to finally use swap. I currently have 4 GB of memory. I might shrink this to like 512 MB or 1 GB the most. Here's some info about my file system setup. sudo hdparm -I /dev/sda1 | grep "TRIM supported" Data Set Management TRIM supported (limit 16 blocks) sudo fdisk -l /dev/sda Device Boot Start End Blocks Id System /dev/sda1 * 2048 242016255 121007104 83 Linux /dev/sda2 242018302 250068991 4025345 5 Extended /dev/sda5 242018304 250068991 4025344 82 Linux swap / Solaris ls /dev/mapper control cryptswap1

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Creating a 2D perspective in 3D game

- by Accatyyc

I'm new to XNA and 3D game development in general. I'm creating a puzzle game kind of similar to tetris, built with blocks. I decided to build the game in 3D since I can do some cool animations and transitions when using 3D blocks with physics etc. However, I really do want the game to look "2D". My blocks are made up of 3D models, but I don't want that to be visible when they're not animating. I have followed some XNA tutorials and set up my scene like this: this.view = Matrix.CreateLookAt(cameraPosition, Vector3.Zero, Vector3.Up); this.aspectRatio = graphics.GraphicsDevice.Viewport.AspectRatio; this.projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f); ... and it gives me a very 3D-ish look. For example, the blocks in the center of the screen looks exactly how I want them, but closer to the edges of the screen I can see the rotation and sides of them. My guess is that I'm not after a perspective field of view, but any help on which field of view/settings to use to get a "flat" look when the blocks aren't rotated would be great!

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Extreme Portability: OpenJDK 7 and GlassFish 3.1.1 on Power Mac G5!

- by MarkH

Occasionally you hear someone grumble about platform support for some portion or combination of the Java product "stack". As you're about to see, this really is not as much of a problem as you might think. Our friend John Yeary was able to pull off a pretty slick feat with his vintage Power Mac G5. In his words: Using a build script sent to me by Kurt Miller, build recommendations from Kelly O'Hair, and the great work of the BSD Port team... I created a new build of OpenJDK 7 for my PPC based system using the Zero VM. The results are fantastic. I can run GlassFish 3.1.1 along with all my enterprise applications. I recently had the opportunity to pick up an old G5 for little money and passed on it. What would I do with it? At the time, I didn't think it would be more than a space-consuming novelty. Turns out...I could have had some fun and a useful piece of hardware at the same time. Maybe it's time to go bargain-hunting again. For more information about repurposing classic Apple hardware and learning a few JDK-related tricks in the process, visit John's site for the full article, available here. All the best,Mark

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BPI On Demand achieves both Oracle Fusion CRM Cloud Service 2013 Specialisation and Reseller status!

- by Richard Lefebvre

Oracle is delighted to share with you that BPI OnDemand has achieved the Oracle Fusion CRM Cloud Service 2013 Specialization and is the EMEA first ever Oracle Sales Cloud reseller ! One of Oracle's most active CRM SaaS partners across EMEA, BPI OnDemand operates out of the UK with subsidiaries in Spain and South Africa that will also benefit locally from the specialization and reseller status. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} BPI OnDemand distinguishes itself from other Oracle Sales Cloud integrators with 2 unique implementation options: 1) Rapid Advantage Fixed Scope for as low as £20,000 or their famous 2) Zero upfront cost Fully Managed Cloud CRM Service which has no equivalent in Europe. BPI OnDemand has already 2 Oracle Sales Cloud live customers and is engaging in many other opportunities including large corporate accounts. Meet BPI OnDemand here or on LinkedIn or on Twitter

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WCF REST Error Handler

- by Elton Stoneman

I’ve put up on GitHub a sample WCF error handler for REST services, which returns proper HTTP status codes in response to service errors. The code is very simple – a ServiceBehavior implementation which can be specified in config to tag the RestErrorHandler to a service. Any uncaught exceptions will be routed to the error handler, which sets the HTTP status code and description in the response, based on the type of exception. The sample defines a ClientException which can be thrown in code to indicate a problem with the client’s request, and the response will be a status 400 with a friendly error message: throw new ClientException("Invalid userId. Must be provided as a positive integer"); - responds: Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/lastLogin?userId=xyz Error Status Code: 400, Description: Invalid userId. Must be provided as a positive integer Any other uncaught exceptions are hidden from the client. The full details are logged with a GUID to identify the error, and the response to the client is a status 500 with a generic message giving them the GUID to follow up on: var iUserId = 0; var dbz = 1 / iUserId; - logs the divide-by-zero error and responds: Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/dbz Error Status Code: 500, Description: Something has gone wrong. Please contact our support team with helpdesk ID: C9C5A968-4AEA-48C7-B90A-DEC986F80DA5 The sample demonstrates two techniques for building the response. For client exceptions, a friendly HTML response is sent in the body as well as the status code and description. Personally I prefer not to do that – it doesn’t make sense to get a 400 error and find text/html when you’re expecting application/json, but it’s easy to do if that’s the functionality you want. The other option is to send an empty response, which the sample does with server exceptions. The obvious extension is to have multiple exceptions representing all the status codes you want to provide, then your code is as simple as throwing the relevant exception – UnauthorizedException, ForbiddenExeption, NotImplementedException etc – anywhere in the stack, and it will be handled nicely.

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SPARC SuperCluster: new Software Enhancements announced on December 4

- by Giuseppe Facchetti

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} December 4, 2012: Oracle Unveils Cloud and Consolidation Capabilities for Oracle SPARC SuperCluster The latest SPARC SuperCluster update offers layered, zero-overhead virtualization for Mission-Critical applications. Oracle today announced new software enhancements to the Oracle SPARC SuperCluster engineered system which enable customers to consolidate any combination of mission-critical enterprise databases, middleware and applications on a single system and rapidly deploy secure, self-service cloud services. For all the details, click here.

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Errors in ~/.xsession-errors

- by Kuberan Naganathan

I'm getting errors in ~/.xession-errors. I'm running ubuntu 12.04 Many apps fail to run without mention of problems in the .xsession-errors file. I looked around and tried to resolve issues myself but failed so far. I have to say it's possible that the issue is related to me mounting /home on another partition. (I say possibly because stuff worked ok for a while.) Fortunately my .xsession-errors file is small enough to post here. Thanks in advance for the help: gnome-keyring-daemon: insufficient process capabilities, unsecure memory might get used gnome-keyring-daemon: insufficient process capabilities, unsecure memory might get used gnome-keyring-daemon: insufficient process capabilities, unsecure memory might get used gnome-keyring-daemon: insufficient process capabilities, unsecure memory might get used Backend : gconf Integration : true Profile : unity Adding plugins Initializing core options...done (gnome-settings-daemon:2547): color-plugin-WARNING **: failed to get edid: unable to get EDID for output (gnome-settings-daemon:2547): color-plugin-WARNING **: unable to get EDID for xrandr-default: unable to get EDID for output (gnome-settings-daemon:2547): color-plugin-WARNING **: failed to reset xrandr-default gamma tables: gamma size is zero Initializing composite options...done Initializing opengl options...done Initializing decor options...done ** Message: applet now removed from the notification area Initializing vpswitch options...done Initializing snap options...done Initializing mousepoll options...done Initializing resize options...done Initializing place options...done Initializing move options...done Initializing wall options...done Initializing grid options...done I/O warning : failed to load external entity "/home/kuberan/.compiz/session/10754cf696d335e98e13471376531156900000024960034" Initializing session options...done Initializing gnomecompat options...done Initializing animation options...done Initializing fade options...done Initializing unitymtgrabhandles options...done Initializing workarounds options...done Initializing scale options...done compiz (expo) - Warn: failed to bind image to texture Initializing expo options...done Initializing ezoom options...done ** Message: using fallback from indicator to GtkStatusIcon (compiz:2560): GConf-CRITICAL **: gconf_client_add_dir: assertion `gconf_valid_key (dirname, NULL)' failed Initializing unityshell options...done Setting Update "main_menu_key" Setting Update "run_key" Setting Update "icon_size" ** Message: moving back from GtkStatusIcon to indicator

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Isometric Camera trouble - can't rotate or move correctly

- by Deukalion

I'm trying to create a 3D editor, but I've been having some trouble with the Camera and understanding each component. I've created 2 camera that works OK, but now I'm trying to implement an Isometric Camera in XNA without success on the rotation and movement of the camera. All I get working is Zoom. (Cube with x=3f, y=3f, z=1f in center) And this is the constructor for my IsometricCamera (inherits from ICamera, with methods for Rotation, Movement and Zoom, and Properties for World/View/Projection matrices) public IsometricCamera3D(GraphicsDevice device, float startClip = -1000f, float endClip = 1000f) { matrix_projection = Matrix.CreateOrthographic(device.Viewport.Width, device.Viewport.Height, startClip, endClip); rotation = Vector3.Zero; matrix_view = Matrix.CreateScale(zoom) * Matrix.CreateRotationY(MathHelper.ToRadians(45 + 180)) * Matrix.CreateRotationX(MathHelper.ToRadians(30)) * Matrix.CreateRotationZ(MathHelper.ToRadians(120)) * Matrix.CreateTranslation(rotation.X, rotation.Y, rotation.Z); } Problem is when I rotate it, all that happens is that the Cube gets more or less shiny and nothing happens. What is wrong and how should I create my View matrix to move it / rotate it correctly? Rotate, Move and Zoom looks like: MethodName(Vector3 rotation/movement), Zoom(float value); and just increases the value, then calls an update to recreate the View Matrix according to the code in the constructor. Currently, in my editor I use MiddleButton + Mouse Movement to rotate the camera, but it's not working as the other camera. But in my default camera I use World Matrix to move, but I guess that's not the best way to go which is why I'm trying this.

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snapping an angle to the closest cardinal direction

- by Josh E

I'm developing a 2D sprite-based game, and I'm finding that I'm having trouble with making the sprites rotate correctly. In a nutshell, I've got spritesheets for each of 5 directions (the other 3 come from just flipping the sprite horizontally), and I need to clamp the velocity/rotation of the sprite to one of those directions. My sprite class has a pre-computed list of radians corresponding to the cardinal directions like this: protected readonly List<float> CardinalDirections = new List<float> { MathHelper.PiOver4, MathHelper.PiOver2, MathHelper.PiOver2 + MathHelper.PiOver4, MathHelper.Pi, -MathHelper.PiOver4, -MathHelper.PiOver2, -MathHelper.PiOver2 + -MathHelper.PiOver4, -MathHelper.Pi, }; Here's the positional update code: if (velocity == Vector2.Zero) return; var rot = ((float)Math.Atan2(velocity.Y, velocity.X)); TurretRotation = SnapPositionToGrid(rot); var snappedX = (float)Math.Cos(TurretRotation); var snappedY = (float)Math.Sin(TurretRotation); var rotVector = new Vector2(snappedX, snappedY); velocity *= rotVector; //...snip private float SnapPositionToGrid(float rotationToSnap) { if (rotationToSnap == 0) return 0.0f; var targetRotation = CardinalDirections.First(x => (x - rotationToSnap >= -0.01 && x - rotationToSnap <= 0.01)); return (float)Math.Round(targetRotation, 3); } What am I doing wrong here? I know that the SnapPositionToGrid method is far from what it needs to be - the .First(..) call is on purpose so that it throws on no match, but I have no idea how I would go about accomplishing this, and unfortunately, Google hasn't helped too much either. Am I thinking about this the wrong way, or is the answer staring at me in the face?

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How do I draw a 2d plane and rotate camara (To be a board) in a 3d XNA game?

- by Mech0z

I am trying to create a simple board game, but the 3d part of this is really killing me. From what I can gather I have created a plane, but it never moves even though I turn the camara, but that partially makes sense as I only turn the camara with a 3d model, but in my head that makes 0 sense, in my head if I turn the camara it should affect ALL my models? But with this code the camara only "cares" about the 3d cylinder, the plane is just completely still private void OnDraw(object sender, GameTimerEventArgs e) { SharedGraphicsDeviceManager.Current.GraphicsDevice.Clear(Color.CornflowerBlue); foreach (ModelMesh mesh in cylinderModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { //effect.World = Matrix.CreateRotationX((float)e.TotalTime.TotalSeconds * 2); effect.View = Matrix.CreateLookAt(cameraPosition, Vector3.Zero, Vector3.Up); effect.Projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f); effect.EnableDefaultLighting(); } mesh.Draw(); } //cameraPosition.Z -= 5.0f; _effect.World = Matrix.CreateRotationZ((MathHelper.ToRadians(((float)e.TotalTime.Milliseconds / 2) % 360))); foreach (EffectPass pass in _effect.CurrentTechnique.Passes) { pass.Apply(); SharedGraphicsDeviceManager.Current.GraphicsDevice.DrawUserPrimitives(PrimitiveType.TriangleStrip, _vertices, 0, 1, VertexPositionColor.VertexDeclaration); } } Is there a way to get the camara to affect all models?

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Performance impact of Zones.

- by nospam(at)example.com (Joerg Moellenkamp)

I was really astonished when i saw this question. Because this question was a old acquaintance from years ago, that i didn't heard for a long time. However there was it again. The question: "What's the overhead of Zones?". Sun was and Oracle is not saying "zero". We saying saying minimal. However during all the performance analysis gigs on customer systems i made since the introduction of Zones i failed to measure any overhead caused by zones. What i saw however, was additional load intoduced by processes that wouldn't be there when you would use only one zone Like additional monitoring daemons, like additional daemons having a controlling or supervising job for the application that resulted in slighly longer runtimes of processes, because such additional daemons wanted some cycles on the CPU as well. So i ask when someone wants to tell me that he measured a slight slowdown, if he or she has really measured the impact of the virtualization layer or of a side effect described above. It seems to be a little bit hard to believe, that a virtualisation technology has no overhead, however keep in mind that there is no hypervisor and just one kernel running that looks and behaves like many operating system instances to apps and users. While this imposes some limits to the technology (because there is just one kernel running you can't have zones with different kernels versions running ... obvious even to the cursory observer), but that is key to it's lightweightness and thus to the low overhead. Continue reading "Performance impact of Zones."

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What is the recommended way to empty a SSD?

- by Lekensteyn

I've just received my new SSD since the old one died. This Intel 320 SSD supports TRIM. For testing purposes, my dealer put malware, err, Windows on it. I want to get rid of it and install Kubuntu on it. It does not have to be a "secure wipe", I just need the empty the disk in the mosy healthy way. I believe that dd if=/dev/zero of=/dev/sda just fills the blocks with zeroes and thereby taking another write (correct me if I'm wrong). I've seen the answer How to enable TRIM, but it looks like it's suited for clearing empty blocks, not wiping the disk. hdparm seems to be the program to do it, but I'm not sure if it clears the disk OR cleans empty blocks. From its manual page: --trim-sector-ranges For Solid State Drives (SSDs). EXCEPTIONALLY DANGEROUS. DO NOT USE THIS OPTION!! Tells the drive firmware to discard unneeded data sectors, destroying any data that may have been present within them. This makes those sectors available for immediate use by the firmware's garbage collection mechanism, to improve scheduling for wear-leveling of the flash media. This option expects one or more sector range pairs immediately after the option: an LBA starting address, a colon, and a sector count, with no intervening spaces. EXCEPTIONALLY DANGEROUS. DO NOT USE THIS OPTION!! E.g. hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz How can I make all blocks appear as empty using TRIM?

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Using a random string to authenticate HMAC?

- by mrwooster

I am designing a simple webservice and want to use HMAC for authentication to the service. For the purpose of this question we have: a web service at example.com a secret key shared between a user and the server [K] a consumer ID which is known to the user and the server (but is not necessarily secret) [D] a message which we wish to send to the server [M] The standard HMAC implementation would involve using the secret key [K] and the message [M] to create the hash [H], but I am running into issues with this. The message [M] can be quite long and tends to be read from a file. I have found its very difficult to produce a correct hash consistently across multiple operating systems and programming languages because of hidden characters which make it into various file formats. This is of course bad implementation on the client side (100%), but I would like this webservice to be easily accessible and not have trouble with different file formats. I was thinking of an alternative, which would allow the use a short (5-10 char) random string [R] rather than the message for autentication, e.g. H = HMAC(K,R) The user then passes the random string to the server and the server checks the HMAC server side (using random string + shared secret). As far as I can see, this produces the following issues: There is no message integrity - this is ok message integrity is not important for this service A user could re-use the hash with a different message - I can see 2 ways around this Combine the random string with a timestamp so the hash is only valid for a set period of time Only allow each random string to be used once Since the client is in control of the random string, it is easier to look for collisions I should point out that the principle reason for authentication is to implement rate limiting on the API service. There is zero need for message integrity, and its not a big deal if someone can forge a single request (but it is if they can forge a very large number very quickly). I know that the correct answer is to make sure the message [M] is the same on all platforms/languages before hashing it. But, taking that out of the equation, is the above proposal an acceptable 2nd best?

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Google penalty recovery

- by sajeev

I have a site, which is a spiritual site and has nothing to do with commercial or business thing. It was in the first page with the keyword RADHANATH SWAMI. Then suddenly, in sep'13, the site went out from google search. When I checked my WebmasterTools, I saw that there were 40,000 backlinks from a site named http://freeguestbooks.net. But manual action section in WebmasterToolssaid "No Manual webspam actions found" and till date, it shows the same. Then I contacted the webmaster of freeguestbooks.net and requested him to remove the 40K odd backlinks and he very kindly removed it. The WebmasterTools now shows 21,777 backlinks from this site. But since 2 months, the decrease rate of these backlinks is very slow, almost zero. Again, I had contacted the webmaster of freeguestbooks.net and he confirmed that there are no backlinks pointing to his site. I am also told that my anchor text is over-optimised... Total backlinks to my site as per WebmasterTools is only 24,937 out of which 21,777 are the links from freeguestbooks.net as shown in WebmasterTools. Could an expert suggest a way out to get back into google.... Sajeev, India

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How do I produce "enjoyably" random, as opposed to pseudo-random?

- by Hilton Campbell

I'm making a game which presents a number of different kinds of puzzles in sequence. I choose each puzzle with a pseudorandom number. For each puzzle, there are a number of variations. I choose the variation with another pseudorandom number. And so on. The thing is, while this produces near-true randomness, this isn't what the player really wants. The player typically wants what they perceive to be and identify as random, but only if it doesn't tend to repeat puzzles. So, not really random. Just unpredictable. Giving it some thought, I can imagine hacky ways of doing it. For example, temporarily eliminating the most recent N choices from the set of possibilities when selecting a new choice. Or assigning every choice an equal probability, reducing a choice's probability to zero on selection, and then increasing all probabilities slowly with each selection. I assume there's an established way of doing this, but I just don't know the terminology so I can't find it. Anyone know? Or has anyone solved this in a pleasing way?

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My application had a WindowsIdentity crisis

- by Brian Donahue

The project I have been working on this week to test computer environments needs to do various actions as a user other than the one running the application. For instance, it looks up an installed Windows Service, finds out who the startup user is, and tries to connect to a database as that Windows user. Later on, it will need to access a file in the context of the currently logged-in user. With ASP .NET, this is super-easy: just go into Web.Config and set up the "identity impersonate" node, which can either impersonate a named user or the one who had logged into the website if authentication was enabled. With Windows applications, this is not so straightforward. There may be something I am overlooking, but the limitation seems to be that you can only change the security context on the current thread: any threads spawned by the impersonated thread also inherit the impersonated credentials. Impersonation is easy enough to do, once you figure out how. Here is my code for impersonating a user on the current thread: using System; using System.ComponentModel; using System.Runtime.InteropServices; using System.Security.Principal; public class ImpersonateUser { IntPtr userHandle; [DllImport("advapi32.dll", SetLastError = true)] static extern bool LogonUser( string lpszUsername, string lpszDomain, string lpszPassword, LogonType dwLogonType, LogonProvider dwLogonProvider, out IntPtr phToken ); [DllImport("kernel32.dll", SetLastError = true)] static extern bool CloseHandle(IntPtr hHandle); enum LogonType : int { Interactive = 2, Network = 3, Batch = 4, Service = 5, NetworkCleartext = 8, NewCredentials = 9, } enum LogonProvider : int { Default = 0, } public static WindowsImpersonationContext Impersonate(string user, string domain, string password) { IntPtr userHandle = IntPtr.Zero; bool loggedOn = LogonUser( user, domain, password, LogonType.Interactive, LogonProvider.Default, out userHandle); if (!loggedOn) throw new Win32Exception(Marshal.GetLastWin32Error()); WindowsIdentity identity = new WindowsIdentity(userHandle); WindowsPrincipal principal = new WindowsPrincipal(identity); System.Threading.Thread.CurrentPrincipal = principal; return identity.Impersonate(); } } /* Call impersonation */ ImpersonateUser.Impersonate("UserName","DomainName","Password"); /* When you want to go back to the original user */ WindowsIdentity.Impersonate(IntPtr.Zero); When you want to stop impersonating, you can call Impersonate() again with a null pointer. This will allow you to simulate a variety of different Windows users from the same applicaiton.

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How do I make my character slide down high-angled slopes?

- by keinabel

I am currently working on my character's movement in Unity3D. I managed to make him move relatively to the mouse cursor. I set a slope limit of 45°, which does not allow the character to walk up the mountains with higher degrees. But he can still jump them up. How do I manage to make him slide down again when he jumped at places with too high slope? Thanks in advance. edit: Code snippet of my basic movement. using UnityEngine; using System.Collections; public class BasicMovement : MonoBehaviour { private float speed; private float jumpSpeed; private float gravity; private float slopeLimit; private Vector3 moveDirection = Vector3.zero; void Start() { PlayerSettings settings = GetComponent<PlayerSettings>(); speed = settings.GetSpeed(); jumpSpeed = settings.GetJumpSpeed(); gravity = settings.GetGravity(); slopeLimit = settings.GetSlopeLimit(); } void Update() { CharacterController controller = GetComponent<CharacterController>(); controller.slopeLimit = slopeLimit; if (controller.isGrounded) { moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")); moveDirection = transform.TransformDirection(moveDirection); moveDirection *= speed; if (Input.GetButton("Jump")) { moveDirection.y = jumpSpeed; } } moveDirection.y -= gravity * Time.deltaTime; controller.Move(moveDirection * Time.deltaTime); } }

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XNA 3D coordinates seem off

- by Peteyslatts

I'm going through a book, and the example it gave me seems like is should work, but when I try and implement it, it falls short. My Camera class takes three vectors in to generate View and Projection matrices. I'm giving it a position vector of (0,0,5), a target vector of Vector.Zero and a top vector (which way is up) of Vector.Up. My Three vertices are placed at (0,1,0), (-1,-1,0), (1,-1,0). It seems like it should work because the vertices are centered around the origin, and thats where I'm telling the camera to look but when I run the game, the only way to get the camera to see the vertices is to set its position to (0,0,-5) and even then the triangle is skewed. Not sure what's wrong here. Any suggestions would be helpful. Just to make sure I've given you guys everything (I don't think these are important as the problem seems to be related to the coordinates, not the ability of the game to draw them): I'm using a VertexBuffer and a BasicEffect. My render code is as follows: effect.World = Matrix.Identity; effect.View = camera.view; effect.Projection = camera.projection; effect.VertexColorEnabled = true; foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawUserPrimitives<VertexPositionColor> (PrimitiveType.TriangleStrip, verts, 0, 1); }

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