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• Identifying which pattern fits better.

  - by Daniel Grillo

  I'm developing a software to program a device. I have some commands like Reset, Read_Version, Read_memory, Write_memory, Erase_memory. Reset and Read_Version are fixed. They don't need parameters. Read_memory and Erase_memory need the same parameters that are Length and Address. Write_memory needs Lenght, Address and Data. For each command, I have the same steps in sequence, that are something like this sendCommand, waitForResponse, treatResponse. I'm having difficulty to identify which pattern should I use. Factory, Template Method, Strategy or other pattern. Edit I'll try to explain better taking in count the given comments and answers. I've already done this software and now I'm trying to refactoring it. I'm trying to use patterns, even if it is not necessary because I'm taking advantage of this little software to learn about some patterns. Despite I think that one (or more) pattern fits here and it could improve my code. When I want to read version of the software of my device, I don't have to assembly the command with parameters. It is fixed. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To read a portion of the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len and Address. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To write a portion in the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len, Address and Data. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. I think that I could use Template Method because I have almost the same algorithm for all. But the problem is some commands are fixes, others have 2 or 3 parameters. I think that parameters should be passed on the constructor of the class. But each class will have a constructor overriding the abstract class constructor. Is this a problem for the template method? Should I use other pattern?

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• Learning by doing (and programming by trial and error)

  - by AlexBottoni

  How do you learn a new platform/toolkit while producing working code and keeping your codebase clean? When I know what I can do with the underlying platform and toolkit, I usually do this: I create a new branch (with GIT, in my case) I write a few unit tests (with JUnit, for example) I write my code until it passes my tests So far, so good. The problem is that very often I do not know what I can do with the toolkit because it is brand new to me. I work as a consulant so I cannot have my preferred language/platform/toolkit. I have to cope with whatever the customer uses for the task at hand. Most often, I have to deal (often in a hurry) with a large toolkit that I know very little so I'm forced to "learn by doing" (actually, programming by "trial and error") and this makes me anxious. Please note that, at some point in the learning process, usually I already have: read one or more five-stars books followed one or more web tutorials (writing working code a line at a time) created a couple of small experimental projects with my IDE (IntelliJ IDEA, at the moment. I use Eclipse, Netbeans and others, as well.) Despite all my efforts, at this point usually I can just have a coarse understanding of the platform/toolkit I have to use. I cannot yet grasp each and every detail. This means that each and every new feature that involves some data preparation and some non-trivial algorithm is a pain to implement and requires a lot of trial-and-error. Unfortunately, working by trial-and-error is neither safe nor easy. Actually, this is the phase that makes me most anxious: experimenting with a new toolkit while producing working code and keeping my codebase clean. Usually, at this stage I cannot use the Eclipse Scrapbook because the code I have to write is already too large and complex for this small tool. In the same way, I cannot use any more an indipendent small project for my experiments because I need to try the new code in place. I can just write my code in place and rely on GIT for a safe bail-out. This makes me anxious because this kind of intertwined, half-ripe code can rapidly become incredibly hard to manage. How do you face this phase of the development process? How do you learn-by-doing without making a mess of your codebase? Any tips&tricks, best practice or something like that?

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• New Oracle BI Applications released

  - by THE

  Oracle has just released two new Applications for Oracle Business Intelligence Analytics with the Normal 0 21 false false false DE 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";} 7.9.6.x Extension Pack: Normal 0 21 false false false DE 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";} · Oracle Manufacturing Analytics, part of the Oracle BI Applications product family, helps discrete and process manufacturing organizations optimize their supply networks by integrating data from across the enterprise value chain, thereby enabling executives, operations managers, cost accountants and production supervisors to make informed and actionable decisions related to manufacturing execution. Normal 0 21 false false false DE 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";} · Oracle Enterprise Asset Management Analytics, part of the Oracle BI Applications product family, offers complete and enhanced visibility to enterprise-wide maintenance information. Pre-built reports covering Maintenance History, Maintenance Cost Analysis and Maintenance Work Orders, provide Maintenance Managers information to maximize performance, identify potential issues much in advance, and address them before they escalate into serious problems.  More Information about the existing Business Intelligence Analytics Applications can be found on this page: http://www.oracle.com/us/solutions/ent-performance-bi/bi-applications-066544.html If you are not familiar with Oracle Manufacturing or Oracle Enterprise Asset Management, these PDFs might get you started: http://www.oracle.com/us/products/applications/060289.pdf http://www.oracle.com/us/products/applications/057127.pdf

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• Collision detection doesn't work for automated elements in XNA 4.0

  - by NDraskovic

  I have a really weird problem. I made a 3D simulator of an "assembly line" as a part of a college project. Among other things it needs to be able to detect when a box object passes in front of sensor. I tried to solve this by making a model of a laser and checking if the box collides with it. I had some problems with BoundingSpheres of models meshes so I simply create a BoundingSphere and place it in the same place as the model. I organized them into a list of BoundingSpheres called "spheres" and for each model I create one BoundingSphere. All models except the box are static, so the box object has its own BoundingSphere (not a member of the "spheres" list). I also implemented a picking algorithm that I use to start the movement. This is the code that checks for collision: if (spheres.Count != 0) { for (int i = 1; i < spheres.Count; i++) { if (spheres[i].Intersects(PickingRay) != null && Microsoft.Xna.Framework.Input.ButtonState.Pressed == Mouse.GetState().LeftButton) { start = true; break; } if (BoxSphere.Intersects(spheres[i]) && start) { MoveBox(0, false);//The MoveBox function receives the direction (0) and a bool value that dictates whether the box should move or not (false means stop) start = false; break; } if (start /*&& Microsoft.Xna.Framework.Input.ButtonState.Pressed == Mouse.GetState().LeftButton*/ && !BoxSphere.Intersects(spheres[i])) { MoveBox(0, true); break; } } The problem is this: When I use the mouse to move the box (the commented part in the third if condition) the collision works fine (I have another part of code that I removed to simplify my question - it calculates the "address" of the box, and by that number I know that the collision is correct). But when I comment it (like in this example) the box just passes trough the lasers and does not detect the collision (the idea is that the box stops at each laser and the user passes it forth by clicking on the appropriate "switch"). Can you see the problem? Please help, and if you need more informations I will try to give them. Thanks

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• Designing Snake AI

  - by Ronald

  I'm new to this gamedev stackechange but have used the math and cs sites before. So, I'm in a competition to create AI for a snake that will compete with 3 other snakes in 5 minute rounds where the rules are much like the traditional Nokia snake game except that there are 4 snakes, the board is 50x50 and there are a number of small obstacles on the field. Like the Nokia game, your snake grows when you get to the fruit and if you crash into yourself, another snake or the wall you die. The game runs with a 50ms delay between moves and the server sends the new game state every 50ms which the code must analyze and what not and output the next move. The winner is the snake who had the longest length at any point in the game. Tie breakers are decided by kills. So far what I have done is implemented an A* graph search from each snake to determine if my snake is the closest to the apple and if it is, it goes for the apple. Otherwise, I made a neat little algorithm to determine the emptiest area of the board, which my snake goes for, to anticipate the next apple. Other than this I have some small survivability checks to ensure my snake isn't walking into a trap that it can't get out and if it does get stuck, I have something to give it a better chance of getting out. ... Anyway, I've tested my snake on a test server and it does quite well. Generally, my strategy of only going for the apple when its a sure thing and finding space when its not makes it grow faster than any other snakes (some snakes do a similar thing but often just go to the middle or a corner) sometimes it wins these trial games but is more often than not beaten by the same snake who seems to have the edge on survivability(my snake grows quicker but then dies somehow and this other snake just plods slowly along and wins on consistency. So I was wondering about any ideas anyone has to try and improve my snake. Or maybe ideas at a new approach to take. My functions and classes are good so changes that might seem drastic shouldn't be too bad. I encourage all ideas. Any thoughts ??

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• Profiling Startup Of VS2012 &ndash; JustTrace Profiler

  - by Alois Kraus

  JustTrace is made by Telerik which is mainly known for its collection of UI controls. The current version (2012.3.1127.0) does include a performance and memory profiler which does cost 614€ and is currently with a special offer for 306€ on sale. It does include one year of free upgrades. The uneven € numbers are calculated from the 799€ and 50% dicsount price. The UI is already in Metro style and simple to use. Multi process, attach, method recording filter are not supported. It looks like JustTrace is like Ants a Just My Code profiler. For stuff where you do not have the pdbs or you want to dig deeper into the BCL code you will not get far. After getting the profile data you get in the All Methods grid a plain list with hit count and own time. The method list for all methods is also suspiciously short which is a clear sign that you will not get far during the analysis of foreign code. But at least there is also a memory profiler included. For this I have to choose in the first window for Profiling Type “Memory Profiler” to check the memory consumption of VS.  There are some interesting number to see but I do really miss from YourKit the thread stack window. How am I supposed to get a clue when much memory is allocated and the CPU consumption is high in which places I should look? The Snapshot summary gives a rough overview which is ok for a first impression. Next is Assemblies? This gives you a list of all loaded assemblies. Not terribly useful.   The By Type view gives you exactly what it is supposed to do. You have to keep in mind that this list is filtered by the types you did check in the Assemblies list. The By Type instance list does only show types from assemblies which do not originate from Microsoft. By default mscorlib and System are not checked. That is the reason why for the first time my By Type window looked like The idea behind this feature is to show only your instances because you are ultimately responsible for the overall memory consumption. I am not sure if I do like this feature because by default it does hide too much. I do want to see at least how many strings and arrays are allocated. A simple namespace filter would also do it in my opinion. Now you can examine all string instances and look who in the object graph does keep a reference on them. That is nice but YourKit has the big plus that you can also look into the string contents.  I am also not sure how in the graph cycles are visualized and what will happen if you have thousands of objects referencing you. That's pretty much it about JustTrace. It can help the average developer to pinpoint performance and memory issues by just looking at his own code and instances. Showing them more will not help them because the sheer amount of information will overwhelm them. And you need to have a pretty good understanding how the GC and the CLR does work. When you have a performance issue at a customer machine it is sometimes very helpful to be able a bring a profiler onto the machine (no pdbs, …) and to get a full snapshot of all processes which are in the problematic use case involved. For these more advanced use cased JustTrace is certainly the wrong tool. Next: SpeedTrace

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• Best way to determine surface normal for a group of pixels?

  - by Paul Renton

  One of my current endeavors is creating a 2D destructible terrain engine for iOS Cocos2D (See https://github.com/crebstar/PWNDestructibleTerrain ). It is in an infant stages no doubt, but I have made significant progress since starting a couple weeks ago. However, I have run into a bit of a performance road block with calculating surface normals. Note: For my destructible terrain engine, an alpha of 0 is considered to not be solid ground. The method posted below works just great given small rectangles, such as n < 30. Anything above 30 causes a dip in the frame rate. If you approach 100x100 then you might as well read a book while the sprite attempts to traverse the terrain. At the moment this is the best I can come up with for altering the angle on a sprite as it roams across terrain (to get the angle for a sprite's orientation just take dot product of 100 * normal * (1,0) vector). -(CGPoint)getAverageSurfaceNormalAt:(CGPoint)pt withRect:(CGRect)area { float avgX = 0; float avgY = 0; ccColor4B color = ccc4(0, 0, 0, 0); CGPoint normal; float len; for (int w = area.size.width; w >= -area.size.width; w--) { for (int h = area.size.height; h >= -area.size.height; h--) { CGPoint pixPt = ccp(w + pt.x, h + pt.y); if ([self pixelAt:pixPt colorCache:&color]) { if (color.a != 0) { avgX -= w; avgY -= h; } // end inner if } // end outer if } // end inner for } // end outer for len = sqrtf(avgX * avgX + avgY * avgY); if (len == 0) { normal = ccp(avgX, avgY); } else { normal = ccp(avgX/len, avgY/len); } // end if return normal; } // end get My problem is I have sprites that require larger rectangles in order for their movement to look realistic. I considered doing a cache of all surface normals, but this lead to issues of knowing when to recalculate the surface normals and these calculations also being quite expensive (also how large should the blocks be?). Another smaller issue is I don't know how to properly treat the case when length is = 0. So I am stuck... Any advice from the community would be greatly appreciated! Is my method the best possible one? Or should I rethink the algorithm? I am new to game development and always looking to learn new tips and tricks.

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• Crystal Ball Live Webcast: Expert insight from EpiX Analytics

  - by Melissa Centurio Lopes

  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:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; 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-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} 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:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; 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-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Register today for the November 2nd live Crystal Ball webcast- Expert insight from EpiX Analytics: Techniques for Improved Risk Management and Decision-Making Join our speaker Dr Huybert Groenendaal, PhD, MSc, MBA, EpiX Analytics LLC and learn how to realize the full value of decision-making techniques, and: • Gain insight into risks and uncertainties • Account for risk in quantitative analysis and decision making • Generate a range of possible outcomes and the probabilities they will occur for any choice of action • Learn best practice for the use of Crystal Ball to support decision making in your own environment • Learn how to avoid common mistakes when using Monte Carlo simulations • Maximize your existing investment in spreadsheet technology Register now for this November 2nd live webcast and don't miss this opportunity to learn how you can model, predict and forecast with better results. For more information view the evite.

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• How to deal with fellow programmer who likes to delegate task with lack any support from boss [closed]

  - by Rudy

  I have a problem with my fellow programmer. We are currently working together in a small project that need to be shipped every 2 weeks. She has a tendency to ask for help for every issues that she is facing. Whether it's a compile error, algorithm problem or even sync/merge issue that caused by herself. She does not even bother to check Google or try to find out by herself. I can be asked to help her for 5-10 times a day. Everyday her husband keeps calling (4-6 times a day), and most of the code that has been delivered by her are actually incorrect. Today she framed me for sending the wrong delivery product. She went home after lunch on the delivery day without telling PM and other team member on that day and her code she commited does not work at all. It's not even tested. I have no choice to roll back her code and cleaning her code just for sake to able to run the product. I have warned her about her defective codes for almost 3 iterations. She said when she was not around I should be able to test her module for her. I snapped and yelled that I am not her slave and directly reported to my boss. However, my boss is not a person that can manage and care about software quality. What is the most important thing to my boss is delivery of product, whether it tested or not. He can even asked us to deliver something that not even tested by QA to the client, on the next day. Most of our suggestion is not followed by him. He even asked me to apologize to her because I snapped. I am tired of the whole situation. This kind of thing keeps repeated. I do have saving to be able to survive for 6 months and the idea of resigning is keep haunting. There is nothing else that can be learned in my current job and I had been in a better environment than this. What should I do with the situation?

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• How to avoid oscillation by async event based systems?

  - by inf3rno

  Imagine a system where there are data sources which need to be kept in sync. A simple example is model - view data binding by MVC. Now I intend to describe these kind of systems with data sources and hubs. Data sources are publishing and subscribing for events and hubs are relaying events to data sources. By handling an event a data source will change it state described in the event. By publishing an event the data source puts its current state to the event, so other data sources can use that information to change their state accordingly. The only problem with this system, that events can be reflected from the hub or from the other data sources, and that can put the system into an infinite oscillation (by async or infinite loop by sync). For example A -- data source B -- data source H -- hub A -> H -> A -- reflection from the hub A -> H -> B -> H -> A -- reflection from another data source By sync it is relatively easy to solve this issue. You can compare the current state with the event, and if they are equal, you don't change the state and raise the same event again. By async I could not find a solution yet. The state comparison does not work by async event handling because there is eventual consistency, and new events can be published in an inconsistent state causing the same oscillation. For example: A(*->x) -> H -> B(y->x) -- can go parallel with B(*->y) -> H -> A(x->y) -- so first A changes to x state while B changes to y state -- then B changes to x state while A changes to y state -- and so on for eternity... What do you think is there an algorithm to solve this problem? If there is a solution, is it possible to extend it to prevent oscillation caused by multiple hubs, multiple different events, etc... ? update: I don't think I can make this work without a lot of effort. I think this problem is just the same as we have by syncing multiple databases in a distributed system. So I think what I really need is constraints if I want to prevent this problem in an automatic way. What constraints do you suggest?

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• 2D collision resolving

  - by Philippe Paré

  I've just worked out an AABB collision algorithm for my 2D game and I was very satisfied until I found out it only works properly with movements of 1 in X and 1 in Y... here it is: public bool Intersects(Rectanglef rectangle) { return this.Left < rectangle.Right && this.Right > rectangle.Left && this.Top < rectangle.Bottom && this.Bottom > rectangle.Top; } public bool IntersectsAny(params Rectanglef[] rectangles) { for (int i = 0; i < rectangles.Length; i++) { if (this.Left < rectangles[i].Right && this.Right > rectangles[i].Left && this.Top < rectangles[i].Bottom && this.Bottom > rectangles[i].Top) return true; } return false; } and here is how I use it in the update function of my player : public void Update(GameTime gameTime) { Rectanglef nextPosX = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); Rectanglef nextPosY; if (Input.Key(Key.Left)) nextPosX.X--; if (Input.Key(Key.Right)) nextPosX.X++; bool xFree = !nextPosX.IntersectsAny(Boxes.ToArray()); if (xFree) nextPosY = new Rectanglef(nextPosX.X, nextPosX.Y, nextPosX.Width, nextPosX.Height); else nextPosY = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); if (Input.Key(Key.Up)) nextPosY.Y--; if (Input.Key(Key.Down)) nextPosY.Y++; bool yFree = !nextPosY.IntersectsAny(Boxes.ToArray()); if (yFree) AABB = nextPosY; else if (xFree) AABB = nextPosX; } What I'm having trouble with, is a system where I can give float values to my movement and make it so there's a smooth acceleration. Do I have to retrieve the collision rectangle (the rectangle created by the other two colliding)? or should I do some sort of vector and go along this axis until I reach the collision? Thanks a lot!

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• Challenges in Corporate Reporting - New Independent Research

  - by ndwyouell

  Earlier this year, Oracle and Accenture sponsored a global study on trends in financial close and reporting. We surveyed 1,123 finance professionals in large organizations in 12 countries around the world during February and March. Financial Consolidation and Reporting is the most mature aspect of Enterprise Performance Management with mainstream solutions having been around for over 30 years. But of course over this time there have been many changes and very significant increases in regulation. So just what is the current state is Financial Consolidation and Reporting in our major corporations across the world? We commissioned this independent research to find out. Highlights of the result are: •          Seeking change: Businesses recognize they need to invest in financial reporting to address the challenges they currently face. 47 percent of companies have made substantial investments over the last year to the financial close, filing, and reporting processes. •          Ineffective investments: Despite these investments, spreadsheets (72 percent) and e-mails (68 percent) are still being used daily to track and manage reporting, suggesting that new investments are falling short of expectations. •          Increased costs and uncertainty: The situation is so opaque that managers across the finance function are unable to fully understand the financial impact or cost implications of reporting, with 60 percent of respondents admitting they did not know the total cost of managing and publicizing their financial results. •          Persistent challenges: 68 percent of respondents admitted that they have inadequate visibility into reporting processes, while 84 percent of finance managers surveyed said they find it difficult to control the quality of financial data across the entire reporting process. •          Decreased effectiveness: 71 percent of finance managers feel their effectiveness is limited in some way by data-analysis–related issues, while 39 percent of C-level or VP-level respondents say their effectiveness is impaired by limited visibility. •          Missed deadlines: Due to late changes to the chart of accounts, 15 percent of global businesses have missed statutory filings, putting their companies at risk of financial penalties and potentially impacting share value. The report makes it clear that investments made to date by these large organizations around the world have been uneven across the close, reporting, and filing processes, which has led to the challenges these organizations currently face in the overall process. Regardless of whether companies are using a variety of solutions or a single solution, the report shows they continue to witness increased costs, ineffectual data management, and missed reporting, which—in extreme circumstances—can impact a company’s corporate image and share value. The good news is that businesses realize that these problems persist and 86 percent of companies are likely to make a significant investment during the next five years to address these issues. While they should invest, it is critical that they direct investments correctly to address the key issues this research identified: •          Improving data integrity •          Optimizing processes •          Integrating the extended financial close process By addressing these issues and with clear guidance on how to implement the correct business processes, infrastructure, and software solutions, finance teams will find that their reporting processes are much more effective, cost-efficient, and aligned with their performance expectations. To get a copy of the full report: http://www.oracle.com/webapps/dialogue/ns/dlgwelcome.jsp?p_ext=Y&p_dlg_id=11747758&src=7300117&Act=92 To replay a webcast discussing the findings: http://www.cfo.com/webcast.cfm?webcast=14639438&pcode=ORA061912_ORA

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• Multi-threaded JOGL Problem

  - by moeabdol

  I'm writing a simple OpenGL application in Java that implements the Monte Carlo method for estimating the value of PI. The method is pretty easy. Simply, you draw a circle inside a unit square and then plot random points over the scene. Now, for each point that is inside the circle you increment the counter for in points. After determining for all the random points wither they are inside the circle or not you divide the number of in points over the total number of points you have plotted all multiplied by 4 to get an estimation of PI. It goes something like this PI = (inPoints / totalPoints) * 4. This is because mathematically the ratio of a circle's area to a square's area is PI/4, so when we multiply it by 4 we get PI. My problem doesn't lie in the algorithm itself; however, I'm having problems trying to plot the points as they are being generated instead of just plotting everything at once when the program finishes executing. I want to give the application a sense of real-time display where the user would see the points as they are being plotted. I'm a beginner at OpenGL and I'm pretty sure there is a multi-threading feature built into it. Non the less, I tried to manually create my own thread. Each worker thread plots one point at a time. Following is the psudo-code: /* this part of the code exists in display() method in MyCanvas.java which extends GLCanvas and implements GLEventListener */ // main loop for(int i = 0; i < number_of_points; i++){ RandomGenerator random = new RandomGenerator(); float x = random.nextFloat(); float y = random.nextFloat(); Thread pointThread = new Thread(new PointThread(x, y)); } gl.glFlush(); /* this part of the code exists in run() method in PointThread.java which implements Runnable */ void run(){ try{ gl.glPushMatrix(); gl.glBegin(GL2.GL_POINTS); if(pointIsIn) gl.glColor3f(1.0f, 0.0f, 0.0f); // red point else gl.glColor3f(0.0f, 0.0f, 1.0f); // blue point gl.glVertex3f(x, y, 0.0f); // coordinates gl.glEnd(); gl.glPopMatrix(); }catch(Exception e){ } } I'm not sure if my approach to solving this issue is correct. I hope you guys can help me out. Thanks.

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• How to implement a multi-part snake with smooth movement? [closed]

  - by Jamie

  Sorry that i couldnt answer on my previous post but it got closed. I couldnt answer because i had to prepair for my finals. As there were problems with understanding of what im trying to achieve, im going to describe a little bit more in depth. Im creating a game in which you steer a snake. I assume everybody knows how that works. But in my case the snake isnt just propagating in an array element by element. Imagine a 2Dgrid on which the snake moves. Its 10x10 tiles. Lets say one tile is 4x4 meters. The snakes head spawns in the middle of the (3,2) tile (beginning with (0,0)), so its position is (4*3+2,4*2+2)(the 2's are so that the snake is in the middle of the 4x4 tile). And heres where the fun begins. when the snake moves, it doesnt jump to next tile. Instead it moves a fraction of the way there. So lets say the snake is heading to tile (4,2). After it moved once, its position is (4*3+2+0.1,4*2+2), where 0.1 is the fraction of the way it moved. This is done to achieve smooth movement. So now im adding the rest of the body. The rest is supposed to move along the exact same path as the head did. I implemented it so that each part of the body has its own position and direction. Then i apply this algorithm: 1.Move each part in its direction. 2.If a part is in the middle of the tile(which implies all of them are), change each parts direction to the direction of the part proceeding it. As i said before i could make this work, but i cant stop thinking that im overlooking a much easier and cleaner solution. So this is my question. Is there any easier/better/faster way to do this?

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• Threads slowing down application and not working properly

  - by Belgin

  I'm making a software renderer which does per-polygon rasterization using a floating point digital differential analyzer algorithm. My idea was to create two threads for rasterization and have them work like so: one thread draws each even scanline in a polygon and the other thread draws each odd scanline, and they both start working at the same time, but the main application waits for both of them to finish and then pauses them before continuing with other computations. As this is the first time I'm making a threaded application, I'm not sure if the following method for thread synchronization is correct: First of all, I use two global variables to control the two threads, if a global variable is set to 1, that means the thread can start working, otherwise it must not work. This is checked by the thread running an infinite loop and if it detects that the global variable has changed its value, it does its job and then sets the variable back to 0 again. The main program also uses an empty while to check when both variables become 0 after setting them to 1. Second, each thread is assigned a global structure which contains information about the triangle that is about to be rasterized. The structures are filled in by the main program before setting the global variables to 1. My dilemma is that, while this process works under some conditions, it slows down the program considerably, and also it fails to run properly when compiled for Release in Visual Studio, or when compiled with any sort of -O optimization with gcc (i.e. nothing on screen, even SEGFAULTs). The program isn't much faster by default without threads, which you can see for yourself by commenting out the #define THREADS directive, but if I apply optimizations, it becomes much faster (especially with gcc -Ofast -march=native). N.B. It might not compile with gcc because of fscanf_s calls, but you can replace those with the usual fscanf, if you wish to use gcc. Because there is a lot of code, too much for here or pastebin, I created a git repository where you can view it. My questions are: Why does adding these two threads slow down my application? Why doesn't it work when compiling for Release or with optimizations? Can I speed up the application with threads? If so, how? Thanks in advance.

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• Wi-Fi triangulation using android smartphone

  - by user1887020

  How to make application for wifi triangulation using android platform? This project will be implemented inside the building. No GPS needed. Just using wifi only and doing triangulation to get the current position of the user inside the building. I got minimum 3 access point to implement it. But how to start code in android and integrate triangulation inside android coding? I got the algorithm to do it.. but is there any chance that I can get it done? Because this project is actually want to replace the floor directory board into a smartphone floor directory so that user can find their way to their room for example to the lab. public class Triangulation { public Triangulation() { int dist_1, dist_2, dist_3; //variable for the distances int x1, x2, x3; //coordinates of x int y1, y2, y3; //coordinates of y int final_dist1, final_dist2; //final distance after calc dist_1 = 1; dist_2 = 2; dist_3 = 3; x1 = 5; //test inputs x2 = 2; x3 = 4; y1 = 2; y2 = 2; y3 = 5; final_dist1 = ((dist_1 * dist_1) - (dist_2 * dist_2) – (x1 * x1) + (x2 * x2) - (y1 * y1) + (y2 * y2)) / 2; final_dist2 = ((dist_2 * dist_2) - (dist_3 * dist_3) – (x2 * x2) + (x3 * x3) - (y2 * y2) + (y3 * y3)) / 2; initial_a1 = x1 - x2; initial_a2 = x2 - x3; initial_b1 = y1 - y2; initial_b2 = y2 - y3; //-----------------------STEP 1-------------------------------------- int a1 = initial_a1 / initial_a1; int a2 = initial_a2 / initial_a1; int b1 = initial_b1 / initial_a1; int b2 = initial_b2 / initial_a1; final_dist1 /= initial_a1; final_dist2 /= initial_a1; //-----------------------STEP 2-------------------------------------- a2 = a2 -a2; final_dist2 = -(initial_a2) * final_dist1 + final_dist2; //-----------------------STEP 3-------------------------------------- a2 /= b2; final_dist2 = final_dist2 / b2; b2 /= b2; //-------------------------STEP 4----------------------------------- b1 = b1 - b1; final_dist1 = -(initial_b1) * final_dist2 + final_dist1; } }

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• Configuring default gateway returned by dhcp server

  - by comp1mp

  Hello, I have a machine which connects via ethernet to a private LAN, and wireless to a network which provides internet connectivity. The private LAN uses a wireless router to perform DHCP. The problem is that the wireless and NIC adapters have different default gateways. The default gateway for the private LAN has a lower adapter metric, and is thus chosen by the routing algorithm. I am thus unable to browse the internet when connected to both adapters. The following link has a solution for manually setting the adapter metric to a high number. http://superuser.com/questions/77822/how-to-tell-windows-7-to-ignore-a-default-gateway I was hoping to find a different solution. Does any one know of a router that allows you to configure its DHCP server to return an empty default gateway? I cannot find such an option for my linksys wrt300n. Configuring a static ip address with no default gateway does work, however I would like to use DHCP if possible. Does anyone know of a different way to specify a default gateway for a windows 7 machine with multiple network adapters without mucking with the adapter metric? Thanks, Matthew

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• Unexpected behaviour when dynamically add node in HAproxy server

  - by Anand Soni

  I wanted to use HAProxy for my web app for load balancing purpose. I am trying to add a new rabbitmq node dynamically in HAProxy server using command : haproxy -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid). I am doing tcp connection mode with leastconn balance algorithm in load balancing. What is expected is when there is 3 connection in one rabbitmq, I add a new rabbit server in HAProxy server. so the next connection would pass to 2nd rabbitmq server which is not happening in my case. It distributes the connection in haphazardly manner. Here is my config file: defaults log global mode http option httplog option dontlognull retries 3 option redispatch maxconn 2000 contimeout 5000 clitimeout 5000 srvtimeout 5000 listen rabbitmq 0.0.0.0:5672 mode tcp stats enable balance leastconn option tcplog server rabbit01 xx.xx.xx.xx:5672 check server rabbit02 xx.xx.xx.xx:5672 check listen tomcatq 0.0.0.0:80 mode http stats enable balance roundrobin stats refresh 10s stats refresh 10s stats uri /lb?stats stats auth admin:admin option httplog What is the problem causing this behavior? Any suggestion will appreciated.

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• big speed difference on a network link with and without VPN tunnel

  - by xirtyllo

  Scenario: We have a network link between two offices. The link is provided by a third party company through a VLAN on their network, but to us it is totally transparent -as if we had a simple ethernet cable going from one location to the other-. We have one router at each side of the link, with 3 VPN tunnels in between the two. The test: When I test the speed of the network link with the routers in place, with one laptop directly connected to the router on each side, I consistently get ~30/35Mbps. But if I take out the routers and I test the link connecting the laptops directly to the ethernet cable at each side, I consistently get ~85/88Mbps. It's quite a big performance hit, and I would tend to think that the VPN tunnels are responsible for the slow down. Is it normal that this configuration (two routers with three VPN tunnels between them) takes away so much bandwidth? More info: The encryption algorithm used for the VPN tunnels is AES128. The routers model is Zyxel USG200 and Zyxel USG1000, and their CPU, memory, and storage use is well within normal limits. The nominal bandwidth of the network link is 100Mbps. The network link in question is supplied by a third party company (the building in between our two offices). Basically it passes through their network as a VLAN, but the VLAN is completely transparent to us (e.g. no configuration required on our side, just like one single cable from end to end). Unfortunately (or maybe fortunately) I cannot directly test different routers configurations as I'm not the person in charge of it.

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• Validating signature trust with gpg?

  - by larsks

  We would like to use gpg signatures to verify some aspects of our system configuration management tools. Additionally, we would like to use a "trust" model where individual sysadmin keys are signed with a master signing key, and then our systems trust that master key (and use the "web of trust" to validate signatures by our sysadmins). This gives us a lot of flexibility, such as the ability to easily revoke the trust on a key when someone leaves, but we've run into a problem. While the gpg command will tell you if a key is untrusted, it doesn't appear to return an exit code indicating this fact. For example: # gpg -v < foo.asc Version: GnuPG v1.4.11 (GNU/Linux) gpg: armor header: gpg: original file name='' this is a test gpg: Signature made Fri 22 Jul 2011 11:34:02 AM EDT using RSA key ID ABCD00B0 gpg: using PGP trust model gpg: Good signature from "Testing Key <[email protected]>" gpg: WARNING: This key is not certified with a trusted signature! gpg: There is no indication that the signature belongs to the owner. Primary key fingerprint: ABCD 1234 0527 9D0C 3C4A CAFE BABE DEAD BEEF 00B0 gpg: binary signature, digest algorithm SHA1 The part we care about is this: gpg: WARNING: This key is not certified with a trusted signature! gpg: There is no indication that the signature belongs to the owner. The exit code returned by gpg in this case is 0, despite the trust failure: # echo $? 0 How do we get gpg to fail in the event that something is signed with an untrusted signature? I've seen some suggestions that the gpgv command will return a proper exit code, but unfortunately gpgv doesn't know how to fetch keys from keyservers. I guess we can parse the status output (using --status-fd) from gpg, but is there a better way?

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• Server cost for smartphone app with web service

  - by FrankieA

  Hello, I am working on a smartphone application that will require a backend web service - but I have absolutely clueless to how much it will cost. Web Service will handle: - login of users - cataloging of our user base - holding minimal profile information for users (the only binary data is a display picture which will be < 20k each) - performing some very minor calculation/algorithm before return results - All the above will be communicated to server from a smartphone (iPhone/BlackBerry/Android) Bandwidth Requirements: - We want to handle up to 10k users throughout the day. - I predict 10k * 50 HTTP requests a day = 500,000 requests a day * 30 = 15 million requests a month Space Requirements: - Data will be in SQL database. - I predict 1MB/user * 10k = 10GB + overhead. In other words - space is not a big issue. Software Requirements: (unless someone knows an alternative) - Windows Server 2008 + IIS - MSFT SQL Server Note: This is 100% new to me, so please hit me with all you got. Do I need Windows Server or are there alternative? Is it better to get multiple cheap servers to distribute load? Will Amazon S3 work for me? How about Windows Azure? Thank you!!

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• Troubleshooting iptables and configuring it to drop the priority of long-term connections

  - by intuited

  I'm somewhat familiar with the general concepts of iptables, and would like to learn it in more detail. I'm hoping that my learning experience can also be useful. The situation: I'm running dd-wrt on my router. Despite its purported QoS skills, I'm still seeing connection latency shoot up hugely whenever there's an ongoing http connection, eg some large download. Under such conditions, it can take 10 seconds or more to load a basic webpage; sometimes the connections are dropped entirely. I've tried adjusting the parameters, dropping the allotted bandwidth for up and download to well under my limit, but nothing seems to work. dd-wrt is configured to use HTB as the QoS algorithm; HFSC, although presented as an option, seems to cause the router to crash, and is rumoured to not actually work on any linux system. I'd like to be able to troubleshoot this issue and hopefully improve the settings that dd-wrt is using, but I'm finding the learning curve a bit overwhelming. For starters I am not sure what HTB actually specifies: is this a set of iptables commands, or do some of those commands specify how HTB is to be used? I would like it to prioritize based on protocol the way that it already supposed to, and in addition I'd like to have it drop the priority of connections which have a high total byte count, say over 400KB. Also tips on utilities that can be run under dd-wrt to get more info on what's going on in there are appreciated. I've tried to get iftop to work but there were issues running curses. I'm leaning towards replacing dd-wrt with openwrt; comments on this strategy are also welcome. I suspect that I would be well advised to get a second router as a standin before trying that. It may be worth noting that my total bandwidth is pretty limited (256Kbit/s).

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• Dynamically updating DNS records with NSUPDATE fails

  - by Thuy

  I've got my own nameserver ns3.epnddns.com and domain epnddns.com I wanted to try and update the records dynamiclly from home using nsupdate but when I run nsupdate -k Kwww.epnddns.com.+157+17183.key i get the following errors Kwww.epnddns.com.+157+17183.key:1: unknown option 'www.epnddns.com.' Kwww.epnddns.com.+157+17183.key:2: unexpected token near end of the file Kwww.epnddns.com.+157+17183.{private,key}: unexpected token Not sure why I get these errors, I'll post my complete setup. Generated keys on my home pc, using dnssec-keygen -a HMAC-MD5 -b 128 -n HOST www.epnddns.com. created /var/named/ and put the keys there and chmod them to 600. transfered the keys to my nameserver ns3.epnddns.com, created /var/named/ ,put the keys there and chmod them to 600 made dnskey.conf in /var/named and added key www.epnddns.com. { algorithm hmac-md5; secret "my secret from they keys=="; }; chmod to 600 then in /etc/bind/named.conf.local include "/var/named/dnskeys.conf"; zone "epnddns.com" { type master; file "/etc/bind/zones/epnddns.com.zone"; allow-transfer { myhomeip; }; //its my home ip so not in the same network allow-update { key www.epnddns.com.; }; }; I restarted bind without any error messages so it seems to be working on the nameserver at least. But on my homepc when i try and run the nsupdate i get those error messages. Thanks in advance for any help or insightful advice.

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• Why is a FLAC encoded from a decoded MP3 bigger than the MP3?

  - by Ryan Thompson

  To be more precise than in the title, suppose I have a MP3 file that is 320 kbps. If I decompress it, then logically, all the data except for roughly 320 kilobits out of each second of audio should be redundant data, able to be compressed away. So, when I encode the decompressed file to FLAC, or any other lossless codec, why is it so much larger? On a related note, is it theoretically possible to losslessly recover the source mp3 audio from a decompressed wav? (I know the mp3 itself is lossy. I'm asking if it's possible to re-encode without any further loss.) EDIT: Let me clarify the related question, and the rationale behind it. Suppose I have a wav that was decompressed from an MP3 file (and assume I don't have the mp3 itself for some reason). If I don't want to lose any more quality, I can re-encode it with FLAC or any other lossless encoder and get a larger file just to maintain the same quality. Or, I can re-encode it to mp3 again and get the same size as the original but lose more data. Obviously, neither of these cases is ideal. I can either have the original size or the original quality, but not both (I mean the quality of the original mp3, not the original lossless source). My question is: Can we get both? Is it theoretically possible to recover the lossy compressed data from the lossy decompressed data, without losing even more? If it is possible, I could imagine a lossless compression algorithm that compresses the audio with FLAC. Then it also scans the audio for any signs of previous lossy compression, and if detected, recompresses it losslessly to the original lossy file. Then it keeps whichever file is smaller.

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• Why do I get a DegradedArray event with mdadm

  - by azera

  Hello Just so we're clear on what's happening: I bought 4 new sata 2 drives, with the intent of using them in a raid5 all drive are fully recognised by both my bios and my linux box (gentoo) I created a raid5 array, fiddled a bit with it to understand how it works, how to monitor ect At some point, this triggered a degradedarray event, even though the array is brand new. I tried to stopping the array and recreating a new array with the same drive but the new array starts degraded too. here is what I used to create it mdadm --create -l5 -n4 /dev/md/md0-r5 /dev/sdb /dev/sdd /dev/sde /dev/sdf here are the output from my /proc/mdstat and mdadm --detail --scan **mdstat** Personalities : [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md127 : active raid5 sdf[4] sde[2] sdd[1] sdb[0] 4395415488 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_] [>....................] recovery = 2.8% (41689732/1465138496) finish=890.3min speed=26645K/sec unused devices: <none> **detail** ARRAY /dev/md/md0-r5 metadata=0.90 spares=1 UUID=453e2833:81f22a74:64188b84:66721085 As such I have a couple questions: does a raid5 array always start in degraded mode at first ? why does sdf have the number 4 between bracket instead of 3, why does it see a spare disk and why is the 4th drive marked with _ instead of U ? (bad configuration ?) How can I recreate the array from scratch, do i have to format each drive on its own before recreating it ? Thanks for any help, I'm not sure about what I should do at the moment

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