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Packing for JavaOne

- by Tori Wieldt

While you are packing for JavaOne, here are some things to remember to bring:1) A Jacket!While October is considered the summer in San Francisco, the heat only lasts a day or two. The fog can roll in any day, and it can be chilly (and maybe even rain).2) Your Oracle LoginMake sure your have your Oracle.com account log in details with you when you arrive onsite in San Francisco. This is the username and password you used/created for your JavaOne 2012 registration. You'll need these to check in and get your badge as well as to gain access to My Account and Schedule Builder onsite at the event. 3) Walking ShoesYou'll want comfortable and practical shoes as this city requires lots of walking and has lots of hills.4) Thumb DrivesWhen sharing cool code, nothing beats sneaker-net. That said, practice safe computing. 5) Consider Downloading a Ride-Sharing Service AppSideCar, Lyft, Uber and RelayRides are taking SF by storm, and are popular alternative to yellow taxis. These are unregulated ride-sharing services, so ride at your own risk. Hipster Tips for SF 1) Don't call it Frisco.2) If you wear shorts, don't complain about how cold it is.3) Bright colored clothes are for tourists. Locals wear black. 4) The most fun ice-cream flavors in town are at Humphry-Slocombe. Check out "secret breakfast."5) The Mission is hip.6) Don't expect there to be a Starbuck's or anything besides a great view at the other side of the Golden Gate bridge.7) SF has seasons, they are just more subtle.

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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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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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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 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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Show and Tell: What work are you the most proud of? [closed]

- by dannywartnaby

Hey, In the spirit of building community, and because it's always cool to see great work being pushed out and created by people, anyone up for a little show and tell? The rules are really simple, and this is supposed to be a bit of fun, so; post a link to a single piece of work (anything you've produced, designed or developed (or helped developed)) and write a little paragraph or two on what it is, what you like about it, the technology you used and perhaps one thing that you learnt from the project. It could be a website, framework, open source project, game, mobile application... etc. So, allow me to start. I'm personally very proud of a tiny iPhone application I designed and developed. It's only available to UK AppStore users, and I only have a small userbase, but, I like it. The application is called Sushi Total: http://knowledgeisporridge.com/sushitotal.html It's written in Objective-C. It's a very simply application that allows you to total up your bill at Yo Sushi restaurants by tapping coloured plates. If I learnt anything from making this application it's this: I believe software should be simple and uncluttered, and that producing an application with one feature is absolutely fine as long as it works really well. So, who's next?

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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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Do you feel bad when you have to learn new things?

- by tactoth

New thing is not always cool. I see many people say they are very bored by doing the similar things day after day. For me it's the opposite - I'm always learning something new. During the last one and a harf year, nearly every two months I need to do lots of researches on a totally new topic: RTMP, MP4, SIP, VNC, Smooth streaming, ..., I have to read lots of specifications, download tones of open source projects to understand concepts, and turn them into my runnable code. And it was so bad! My brain has never been very sure and very familiar with anything, and when it's close to be sure and familiar, it'll have to switch to next thing. I kind of envy people who build upper level applications because they can be very focusing, and their knowledge set includes most things their job requires. Everything is quite measurable, direct and straightforward. Have you ever had the similar feeling? I'm thinking of asking my boss to assign me some other piece of work so that I work like moving forward on a broad road instead of figuring out a way in the dark, I think it'll be more relaxing, any suggestion?

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Uralelektrostroy Improves Turnaround Times for Engineering and Construction Projects by Approximately 50% with Better Project Data Management

- by Melissa Centurio Lopes

LLC Uralelektrostroy was established in 1998, to meet the growing demand for reliable energy supply, which included the deployment and operation of a modern power grid system for Russia’s booming economy and industrial sector. To rise to the challenge, the country required a company with a strong reputation and the ability to strategically operate energy production and distribution facilities. As a renowned energy expert, Uralelektrostroy successfully embarked on the mission—focusing on the design, construction, and operation of power grids, transmission lines, and generation facilities. Today, Uralelektrostroy leads the Russian utilities industry with operations across the country, particularly in the Ural, Western Siberia, and Moscow regions. Challenges: Track work progress through all engineering project development stages with ease—from planning and start-up operations, to onsite construction and quality assurance—to enhance visibility into complex projects, such as power grid and power-transmission-line construction Implement and execute engineering projects faster—for example, designing and building power generation and distribution facilities—by better monitoring numerous local subcontractors Improve alignment of project schedules with project owners’ requirements—awarding federal and regional authorities—to avoid incurring fines for missing deadlines Solutions: Used Oracle’s Primavera P6 Enterprise Project Portfolio Management 8.1 to streamline communication with customers and subcontractors through better data management and harmonized reporting, reducing construction project implementation and turnaround times by approximately 50%, on average Enabled fast generation of work-in-progress reports that track project schedules, budgets, materials, and staffing—from approval and material procurement, to construction and delivery Reduced the number of construction sites by nearly 30% (from 35 to 25) by identifying unprofitable sites—streamlining operations at the company’s construction site network and increasing profitability Improved project visibility by enabling managers to efficiently track project status, ensuring on-time reporting and punctual project deliveries to federal customers to reduce delay penalties to zero “Oracle’s Primavera P6 Enterprise Project Portfolio Management 8.1 drastically changed the way we run our business. We’ve reduced the number of redundant assets, streamlined project implementation and execution, and improved collaboration with our customers and contractors. Overall, the Oracle deployment helped to increase our profitability.” – Roman Aleksandrovich Naumenko, Head of Information Technology, LLC Uralelektrostroy Read the complete customer snapshot here.

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Computer Science graduate. Master or full-time job? [closed]

- by Alex

Possible Duplicate: Is a Master's worth it? I have just gotten my Bachelor's Degree in Computer Science and I have to make choice. Whether to continue with my full-time job I just got or put the job slightly in the background and concentrate on getting a Master's degree. I am currently working as an embedded C developer in a small company. The cool thing is that, because the team is quite small, my engineering ideas really play a part in the final product. Not to mention that I get to work on very different areas of embedded programming: device drivers and development of a Real Time OS. I am very enthusiastic about my job and what I do. On the other hand, in my country there isn't really a master's degree that focuses on embedded development so my gain from getting this degree will mainly in the field of general computer science knowledge. That being said, is it worth giving up all my spare time which I now use to study different areas of embedded devices and work mainly to get a degree rather than pure knowledge and experience in the field I want to work in?

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Getting into the details of game engine programming

- by Darkslash

I am interested in learning game programming, but I really have an interest in the lower level engineering in games. I have OpenGL experience, and I am really interested in learning more about implementing AI, Physics, etc. I have a computer science degree, so I really like getting into technical stuff. Many times when I ask about this sort of thing, I get a lot of "Use an engine", "Use Unity3d", "Why waste your time writing code that already exists", etc, etc. My idea was to use simpler libraries such as SFML or XNA so that I could learn how to implement the more complex systems. The thing is, although I do want to write games, I want to learn things that using something like Unity simply doesn't teach you. My goal is not to make a current generation quality 3D game to sell, I just want to make some cool smaller games and learn all I can about the programming side of game development. Is this something that people just do not do anymore? It seems like everywhere I turn people are using Unity or UDK or GameMaker. I fully understand why you would use a tool like these, but I cant see how they would suit my purposes. So where does someone like myself turn? Am I trying to learn something that people just do not bother doing anymore? Is the innovation in this area gone and just all about gameplay now? I'm sorry if this question seems silly, but I am genuinely interested in knowing more about this and meeting more people who are interested in this sort of thing.

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Downclock CPU reaching critical temperature

- by Draga

I have an HP tx1250 laptop. It always had serious overheating problems and although usually it runs fine I'm now running a continuous test for my dissertation, this brings the CPU temp close to the critical and from time to time the computer shutdown for reaching it (checked the log). I use to have the same problem on Win XP but I noticed Win Vista and 7 downclock the CPU when is necessary to cool it down so I was thinking if the same is possible on Ubuntu 12. The only program I've found that may do the job is computer temp ( http://computertemp.berlios.de/ ) but it doesn't seems to work under Ubuntu 12. The inside of the laptop is fairly clean, the thermal paste is quite recent, I'm keeping it lifted from the desk and judjung by the sound of the fan that's running fine as well. The pc in now running between 78 and 91 degrees C but about once a day it shut down for reaching 95. I need the results of the test it's running pretty soon so it's important that it runs non-stop. I've though to set the maximum clock of the CPU to slightly less the maximum but then these tests I'm running would take much more time. Thanks! PS: first and last HP laptop for me.

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How do I stop video tearing? (Nvidia prop driver, non-compositing window manager)

- by Chan-Ho Suh

I have that problem which seemingly afflicts many using the proprietary Nvidia driver: Video tearing: fine horizontal lines (usually near the top of my display) when there is a lot of panning or action in the video. (Note: switching back to the default nouveau driver is not an option, as its seemingly nonexistent power-management drains my battery several times faster) I've tried Totem, Parole, and VLC, and tearing occurs with all of them. The best result has been to use X11 output in VLC, but there is still tearing with relatively moderate action. Hardware: MacBook Air 3,2 -- which has an Nvidia GeForce 320M. There are two common fixes for tearing with Nvidia prop drivers: Turn off compositing, since Nvidia proprietary drivers don't usually play nice with compositing window managers on Linux (Compiz is an exception I'm aware of). But I use an extremely lightweight window manager (Awesome window manager) which is not even capable of compositing (or any cool effects). I also have this problem in Xfce, where I have compositing disabled. Enabling sync to VBlank. To enable this, I set the option in nvidia-settings and then autostart it as nvidia-settings -l with my other autostart programs. This seems to work, because when I run glxgears, I get: $ glxgears Running synchronized to the vertical refresh. The framerate should be approximately the same as the monitor refresh rate. 303 frames in 5.0 seconds = 60.500 FPS 300 frames in 5.0 seconds = 59.992 FPS And when I check the refresh rate using nvidia-settings: $ nvidia-settings -q RefreshRate Attribute 'RefreshRate' (wampum:0.0; display device: DFP-2): 60.00 Hz. All this suggests sync to VBlank is enabled. As I understand it, this is precisely designed to stop tearing, and a lot of people's problem is even getting something like glxgears to output the correct info. I don't understand why it's not working for me. xorg.conf: http://paste.ubuntu.com/992056/ Example of observed tearing::

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How do I reconstruct depth in deferred rendering using an orthographic projection?

- by Jeremie

I've been trying to get my world space position of my pixel but I4m missing something. I'm using a orthographic view for a 2.5d game. My depth is linear and this is my code. float3 lightPos = lightPosition; float2 texCoord = PostProjToScreen(PSIn.lightPosition)+halfPixel; float depth = tex2D(depthMap, texCoord); float4 position; position.x = texCoord.x *2-1; position.y = (1-texCoord.y)*2-1; position.z = depth.r; position.w = 1; position = mul(position, inViewProjection); //position.xyz/=position.w; // I comment it but even without it it doesn't work float4 normal = (tex2D(normalMap, texCoord)-.5f) * 2; normal = normalize(normal); float3 lightDirection = normalize(lightPos-position); float att = saturate(1.0f - length(lightDirection) /attenuation); float lightning = saturate (dot(normal, lightDirection)); lightning*= brightness; return float4(lightColor* lightning*att, 1); I'm using a sphere but it's not working the way I want. I reproject the texture properly onto the sphere but the light coordinates in the pixel shader seems to be stuck at zero even if when I move the light volume update properly.

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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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Where we should put validation for domain model

- by adisembiring

I still looking best practice for domain model validation. Is that good to put the validation in constructor of domain model ? my domain model validation example as follows: public class Order { private readonly List<OrderLine> _lineItems; public virtual Customer Customer { get; private set; } public virtual DateTime OrderDate { get; private set; } public virtual decimal OrderTotal { get; private set; } public Order (Customer customer) { if (customer == null) throw new ArgumentException("Customer name must be defined"); Customer = customer; OrderDate = DateTime.Now; _lineItems = new List<LineItem>(); } public void AddOderLine //.... public IEnumerable<OrderLine> AddOderLine { get {return _lineItems;} } } public class OrderLine { public virtual Order Order { get; set; } public virtual Product Product { get; set; } public virtual int Quantity { get; set; } public virtual decimal UnitPrice { get; set; } public OrderLine(Order order, int quantity, Product product) { if (order == null) throw new ArgumentException("Order name must be defined"); if (quantity <= 0) throw new ArgumentException("Quantity must be greater than zero"); if (product == null) throw new ArgumentException("Product name must be defined"); Order = order; Quantity = quantity; Product = product; } } Thanks for all of your suggestion.

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Is IDirectInput8::FindDevice totally broken on Windows 7?

- by Noora

I'm developing on Windows 7, and using DirectInput8 for my input needs. I'm tracking gamepad additions and removals (that is, GUID_DEVINTERFACE_HID devices) using the DBT_DEVICEARRIVAL and DBT_DEVICEREMOVECOMPLETE messages, which works fine. However, what I've come to find out is that no matter what I do, passing the received values from DBT_DEVICEARRIVAL to IDirectInput8's FindDevice method, it will always fail to identify the device, returning DIERR_DEVICENOTREG. DirectInput still clearly knows about the device, because I can enumerate and create it just fine. I've tried with three different gamepads, and the error persists, so it's not about that either. I also tried passing some alternative interface GUIDs for the RegisterDeviceNotification call, didn't help. So, has anyone else faced the same problem, and have you found a usable workaround? I'm afraid I'll soon have to stoop down to re-enumerating all devices when something is added or removed, but I'll first give this question one last shot here. EDIT: For the record, I've also tried pretty much every single HID API & SetupAPI function for alternative ways of figuring out the needed GUIDs, with zero success. So if you're facing the same problem as me, don't bother with that route. I'm pretty sure those GUIDs are made up by DirectInput itself somehow. Short of reverse engineering dinput8.dll, I'm truly out of ideas now.

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What does the ".align" x86 Assembler directive do exactly? [migrated]

- by Sinister Clock

I will list exactly what I do not understand, and show you the parts I can not understand as well. First off, The .Align Directive .align integer, pad. The .align directive causes the next data generated to be aligned modulo integer bytes 1.~ ? : What is implied with "causes the next data generated to be aligned modulo integer bytes?" I can surmise that the next data generated is a memory-to-register transfer, no? Modulo would imply the remainder of a division. I do not understand "to be aligned modulo integer bytes"....... What would be a remainder of a simple data declaration, and how would the next data generated being aligned by a remainder be useful? If the next data is aligned modulo, that is saying the next generated data, whatever that means exactly, is the remainder of an integer? That makes absolutely no sense. What specifically would the .align, say, .align 8 directive issued in x86 for a data byte compiled from a C char, i.e., char CHARACTER = 0; be for? Or specifically coded directly with that directive, not preliminary Assembly code after compiling C? I have debugged in Assembly and noticed that any C/C++ data declarations, like chars, ints, floats, etc. will insert the directive .align 8 to each of them, and add other directives like .bss, .zero, .globl, .text, .Letext0, .Ltext0. What are all of these directives for, or at least my main asking? I have learned a lot of the main x86 Assembly instructions, but never was introduced or pointed at all of these strange directives. How do they affect the opcodes, and are all of them necessary?

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why does array initialization in function other than main is temporary? [on hold]

- by shafeeq

This is the code in which i initialize array "turn[20]" in main as well as in function "checkCollisionOrFood()",the four values turn[0],turn[1],turn[2],turn[3] are initialized to zero in main function,rest are being intialized in "checkCollisionOrFood()".This is where fault starts.when i initialize turn[4]=0 in "checkCollisionOrFood()" and then access it anywhere,it remains 0 in any function,but! when i initialize next turn[] i.e turn[5],the value of turn[4] gets depleted .i.e turn[4] have garbage value.turn[20] is global variable,its index"head" is also global.I'm stuck.Plz help me get out of it.Ishall be highly obliged for this act of kindness.This is my excerpt of code unsigned short checkCollisionOrFood(){ head=(head+1)%20; if(turn[head-1]==0){ turn[head]=0; /this is where turn[] is iniliazized and if i access turn[head] here i.e just after iniliazition then it gives correct value but if i access its previous value means turn[head-1]then it gives garbage value/ rowHead=(rowHead+1)%8; if(!(address[colHead]&(1<<rowHead)))return 1; else if((address[colHead]&(1<<rowHead))&& (!((colHead==foody)&&(rowHead==foodx))))gameOver(); else return 0; } if(turn[head-1]==1){ turn[head]=1; colHead=(colHead+1)%8; if(!(address[colHead]&(1<<rowHead)))return 1; else if((address[colHead]&(1<<rowHead))&& (!((colHead==foody)&&(rowHead==foodx))))gameOver(); else return 0; } } void main(void) { turn[0]=0;turn[1]=0;turn[2]=0;turn[3]=0; /these values of turn[] are not changed irrespective of where they are accessed./ while (1) { if(checkCollisionOrFood()) { PORTB=(address[colHead] |=1<<rowHead); turnOffTail(); blink(); } else { PORTB=address[colHead]; createFood(); blink(); } } } Plz help me.

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Collision Detection Problems

- by MrPlosion

So I'm making a 2D tile based game but I can't quite get the collisions working properly. I've taken the code from the Platformer Sample and implemented it into my game as seen below. One problem I'm having is when I'm on the ground for some strange reason I can't move to the left. Now I'm pretty sure this problem is from the HandleCollisions() method because when I stop running it I can smoothly move around with no problems. Another problem I'm having is when I'm close to a tile the character jitters very strangely. I will try to post a video if necessary. Here is the HandleCollisions() method: Thanks. void HandleCollisions() { Rectangle bounds = BoundingRectangle; int topTile = (int)Math.Floor((float)bounds.Top / World.PixelTileSize); int bottomTile = (int)Math.Ceiling((float)bounds.Bottom / World.PixelTileSize) - 1; int leftTile = (int)Math.Floor((float)bounds.Left / World.PixelTileSize); int rightTile = (int)Math.Ceiling((float)bounds.Right / World.PixelTileSize) - 1; isOnGround = false; for(int x = leftTile; x <= rightTile; x++) { for(int y = topTile; y <= bottomTile; y++) { if(world.Map[y, x].Collidable == true) { Rectangle tileBounds = new Rectangle(x * World.PixelTileSize, y * World.PixelTileSize, World.PixelTileSize, World.PixelTileSize); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if(depth != Vector2.Zero) { if(Math.Abs(depth.Y) < Math.Abs(depth.X)) { isOnGround = true; position = new Vector2(position.X, position.Y + depth.Y); } else { position = new Vector2(position.X + depth.X, position.Y); } bounds = BoundingRectangle; } } } }

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Process that needs a volume starting before volume mounts

- by user36126

The destination for incoming CrashPlan backups on my server (11.04) is /media/SeagateBig (SeagateBig is the volume name of my 2TB USB drive). When the server boots, two things happen: 1) SeagateBig auto-mounts and 2) CrashPlan starts. The problem is, that often these two things don't happen in that order. Then I get: Crashplan starts looks for /media/SeagateBig doesn't find it instead of waiting for it, CREATES IT Now it's backing up onto my / filesystem. NOT COOL. Meanwhile, when SeagateBig finally gets around to mounting, it finds that /media/SeagateBig already exists, shrugs, and creates /media/SeagateBig_ as its mount point. What I need is a way for the order to be enforced - where SeagateBig mounts and then and only then the CrashPlan service is started. Unless I learn that CrashPlan can be told to wait for its destination directory, never to create it... which I am also investigating. But the CrashPlanEngine script is installed by the product so I am loath to modify it, as I know I could by having it loop until df greps successfully for "SeagateBig".

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Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

- by Prog

In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the entities (i.e. where the entities 'act': update their positions, invoke AI, etc) is in a different class, in the method updateEntities(List<Entity> entities). Also called from the gameloop, after the collision detection. When there's a collision between two entities, usually something needs to be done. For example, zero the velocity of both entities in the collision, or kill one of the entities. It would be easy to have this code in the CollisionDetector class. E.g. in psuedocode: for(Entity entityA in entities){ for(Entity entityB in entities){ if(collision(entityA, entityB)){ if(entityA instanceof Robot && entityB instanceof Robot){ entityA.setVelocity(0,0); entityB.setVelocity(0,0); } if(entityA instanceof Missile || entityB instanceof Missile){ entityA.die(); entityB.die(); } } } } However, I'm not sure if updating the state of entities in response to collision should be the job of CollisionDetector. Maybe it should be the job of EntityUpdater, which runs after the collision detection in the gameloop. Is it okay to have the code responding to collisions in the collision detection system? Or should the collision detection class only detect collisions, report them to some other class and have that class affect the state of the entities?

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RequireJS: JavaScript for the Enterprise

- by Geertjan

I made a small introduction to RequireJS via some of the many cool new RequireJS features in NetBeans IDE. I believe RequireJS, and the modularity and encapsulation and loading solutions that it brings, provides the tools needed for creating large JavaScript applications, i.e., enterprise JavaScript applications. &amp;lt;span id=&amp;quot;XinhaEditingPostion&amp;quot;&amp;gt;&amp;lt;/span&amp;gt; (Sorry for the wobbly sound in the above.) An interesting comment by my colleague John Brock on the above: One other advantage that RequireJS brings, is called lazy loading of resources. In your first example, everyone one of those .js files is loaded when the first file is loaded in the browser. By using the require() call in your modules, your application will only load the javascript modules when they are actually needed. It makes for faster startup in large applications. You could show this by showing the libraries that are loaded in the Network Monitor window. So I did as suggested: Click the screenshot to enlarge it and notice how the Network Monitor is helpful in the context of RequireJS troubleshooting.

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How are certain analytics metrics (time on site, etc.) usually distributed?

- by a barking spider

I'm not sure if I've come to the right place to ask this question, but I'm gathering some information for a research project. We're trying to design an experiment that'll heavily involve web analytics, and I'm trying to figure out some sensible values of mean +/- standard deviation for the following visitor-level (i.e., visitor 1 spends 2 minutes on site, visitor 2 spends 1 minute -- mean 1.5 +/- 0.71...) metrics: time spent on site page views If time allowed, we would put up the sites and gather the information ourselves, but we have a grant deadline coming up. I realize that even though these the distributions of these quantities are probably going to be heavily skewed towards zero, we'll need some reasonable figures or estimates of these figures in order to do sample size calculations, etc. Anyway, I'm not sure where else I'd turn, and I certainly have had a difficult time finding these values in the prior literature. If someone could direct me to a paper with the right information, or if you have these figures on hand (perhaps taken directly from your logs!) -- that would be amazing, and I'd love to hear from you. Thanks in advance, and even though I'm not allowed to reveal too much, rest assured that this info'll be applied towards a good cause :)

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why are transaction monitors on decline? or are they?

- by mrkafk

http://www.itjobswatch.co.uk/jobs/uk/cics.do http://www.itjobswatch.co.uk/jobs/uk/tuxedo.do Look at the demand for programmers (% of job ads that the keyword appears), first graph under the table. It seems like demand for CICS, Tuxedo has fallen from 2.5%/1% respectively to almost zero. To me, it seems bizarre: now we have more networked and internet enabled machines than ever before. And most of them are talking to some kind of database. So it would seem that use of products whose developers spent last 20-30 years working on distributing and coordinating and optimizing transactions should be on the rise. And it appears they're not. I can see a few causes but can't tell whether they are true: we forgot that concurrency and distribution are really hard, and redoing it all by ourselves, in Java, badly. Erlang killed them all. Projects nowadays have changed character, like most business software has already been built and we're all doing internet services, using stuff like Node.js, Erlang, Haskell. (I've used RabbitMQ which is written in Erlang, "but it was small specialized side project" kind of thing). BigData is the emphasis now and BigData doesn't need transactions very much (?). None of those explanations seem particularly convincing to me, which is why I'm looking for better one. Anyone?

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