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• Question about server usage, big community platform [closed]

  - by Json

  Possible Duplicate: How do you do Load Testing and Capacity Planning for Web Sites I’m working on a community platform writen in PHP, MySQL. I have some questions about the server usage maybe someone can help me out. The community is based on JQuery with many ajax requests to update content. It makes 5 - 10 AJAX(Json, GET, POST) requests every 5 seconds, the requests fetch user data like user notifications and messages by doing mySQL queries. I wonder how a server will handle this when there are for more than 5000 users online. Then it will be 50.000 requests every 5 seconds, what kind of server you need to handle this? Or maybe even more, when there are 15.000 users online, 150.000 requests every 5 seconds. My webserver have the following specs. Xeon Quad 2048MB 5000GB traffic Will it be good enough, and for how many users? Anyone can help me out or know where to find such information, like make a calculation?

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• Point in polygon OR point on polygon using LINQ

  - by wageoghe

  As noted in an earlier question, How to Zip enumerable with itself, I am working on some math algorithms based on lists of points. I am currently working on point in polygon. I have the code for how to do that and have found several good references here on SO, such as this link Hit test. So, I can figure out whether or not a point is in a polygon. As part of determining that, I want to determine if the point is actually on the polygon. This I can also do. If I can do all of that, what is my question you might ask? Can I do it efficiently using LINQ? I can already do something like the following (assuming a Pairwise extension method as described in my earlier question as well as in links to which my question/answers links, and assuming a Position type that has X and Y members). I have not tested much, so the lambda might not be 100% correct. Also, it does not take very small differences into account. public static PointInPolygonLocation PointInPolygon(IEnumerable<Position> pts, Position pt) { int numIntersections = pts.Pairwise( (p1, p2) => { if (p1.Y != p2.Y) { if ((p1.Y >= pt.Y && p2.Y < pt.Y) || (p1.Y < pt.Y && p2.Y >= pt.Y)) { if (p1.X < p1.X && p2.X < pt.X) { return 1; } if (p1.X < pt.X || p2.X < pt.X) { if (((pt.Y - p1.Y) * ((p1.X - p2.X) / (p1.Y - p2.Y)) * p1.X) < pt.X) { return 1; } } } } return 0; }).Sum(); if (numIntersections % 2 == 0) { return PointInPolygonLocation.Outside; } else { return PointInPolygonLocation.Inside; } } This function, PointInPolygon, takes the input Position, pt, iterates over the input sequence of position values, and uses the Jordan Curve method to determine how many times a ray extended from pt to the left intersects the polygon. The lambda expression will yield, into the "zipped" list, 1 for every segment that is crossed, and 0 for the rest. The sum of these values determines if pt is inside or outside of the polygon (odd == inside, even == outside). So far, so good. Now, for any consecutive pairs of position values in the sequence (i.e. in any execution of the lambda), we can also determine if pt is ON the segment p1, p2. If that is the case, we can stop the calculation because we have our answer. Ultimately, my question is this: Can I perform this calculation (maybe using Aggregate?) such that we will only iterate over the sequence no more than 1 time AND can we stop the iteration if we encounter a segment that pt is ON? In other words, if pt is ON the very first segment, there is no need to examine the rest of the segments because we have the answer. It might very well be that this operation (particularly the requirement/desire to possibly stop the iteration early) does not really lend itself well to the LINQ approach. It just occurred to me that maybe the lambda expression could yield a tuple, the intersection value (1 or 0 or maybe true or false) and the "on" value (true or false). Maybe then I could use TakeWhile(anontype.PointOnPolygon == false). If I Sum the tuples and if ON == 1, then the point is ON the polygon. Otherwise, the oddness or evenness of the sum of the other part of the tuple tells if the point is inside or outside.

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• Incremental PCA

  - by smichak

  Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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• C# slowdown while creating a bitmap - calculating distances from a large List of places for each pixel

  - by user576849

  I'm creating a graphic of the glow of lights above a geographic location based upon Walkers Law: Skyglow=0.01*Population*DistanceFromCenter^-2.5 I have a CSV file of places with 66,000 records using 5 fields (id,name,population,latitude,longitude), parsed on the FormLoad event and stored it in: List<string[]> placeDataList Then I set up nested loops to fill in a bitmap using SetPixel. For each pixel on the bitmap, which represents a coordinate on a map (latitude and longitude), the program loops through placeDataList – calculating the distance from that coordinate (pixel) to each place record. The distance (along with population) is used in a calculation to find how much cumulative sky glow is contributed to the coordinate from each place record. So, for every pixel, 66,000 distance calculations must be made. The problem is, this is predictably EXTREMELY slow – on the order of one line of pixels per 30 seconds or so on a 320 pixel wide image. This is unrelated to SetPixel, which I know is also slow, because the speed is similarly slow when adding the distance calculation results to an array. I don’t actually need to test all 66,000 records for every pixel, only the records within 150 miles (i.e. no skyglow is contributed to a coordinate from a small town 3000 miles away). But to find which records are within 150 miles of my coordinate I would still need to loop through all the records for each pixel. I can't use a smaller number of records because all 66,000 places contribute to skyglow for SOME coordinate in my map as it loops. This seems like a Catch-22, so I know there must be a better method out there. Like I mentioned, the slowdown is related to how many calculations I’m making per pixel, not anything to do with the bitmap. Any suggestions? private void fillPixels(int width) { Color pixelColor; int pixel_w = width; int pixel_h = (int)Math.Floor((width * 0.424088664)); Bitmap bmp = new Bitmap(pixel_w, pixel_h); for (int i = 0; i < pixel_h; i++) for (int j = 0; j < pixel_w; j++) { pixelColor = getPixelColor(i, j); bmp.SetPixel(j, i, pixelColor); } bmp.Save("Nightfall", System.Drawing.Imaging.ImageFormat.Jpeg); pictureBox1.Image = bmp; MessageBox.Show("Done"); } private Color getPixelColor(int height, int width) { int c; double glow,d,cityLat,cityLon,cityPop; double testLat, testLon; int size_h = (int)Math.Floor((size_w * 0.424088664)); ; testLat = (height * (24.443136 / size_h)) + 24.548874; testLon = (width * (57.636853 / size_w)) -124.640767; glow = 0; for (int i = 0; i < placeDataList.Count; i++) { cityPop=Convert.ToDouble(placeDataList[i][2]); cityLat=Convert.ToDouble(placeDataList[i][3]); cityLon=Convert.ToDouble(placeDataList[i][4]); d = distance(testLat, testLon, cityLat, cityLon,"M"); if(d<150) glow = glow+(0.01 * cityPop * Math.Pow(d, -2.5)); } if (glow >= 1) glow=1; c = (int)Math.Ceiling(glow * 255); return Color.FromArgb(c, c, c); }

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• Can I execute a "variable statements" within a function and without defines.

  - by René Nyffenegger

  I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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• Physics in my game confused after restructuring the Game loop

  - by Julian Assange

  Hello! I'm on my way with making a game in Java. Now I have some trouble with an interpolation based game loop in my calculations. Before I used that system the calculation of a falling object was like this: Delta based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(float timeDeltaSeconds, Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity * timeDeltaSeconds); parentObject.yVelocity -= SPEED_OF_GRAVITY * timeDeltaSeconds; ...... What you see here is that I used that delta value from previous frame to the current frame to calculate the physics. Now I switched and implement a interpolation based system and I actually left the current system where I used delta to calculate my physics. However, with the interpolation system the delta time is removed - but now are my calculations screwed up and I've tried the whole day to solve this: Interpolation based system private static final float SPEED_OF_GRAVITY = 500.0f; @Override public void update(Object parentObject) { parentObject.y = parentObject.y + (parentObject.yVelocity); parentObject.yVelocity -= SPEED_OF_GRAVITY; ...... I'm totally clueless - how should this be solved? The rendering part is solved with a simple prediction method. With the delta system I could see my object be smoothly rendered to the screen, but with this interpolation/prediction method the object just appear sticky for one second and then it's gone. The core of this game loop is actually from here deWiTTERS Game Loop, where I trying to implement the last solution he describes. Shortly - my physics are in a mess and this need to be solved. Any ideas? Thanks in advance!

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• Mean filter in MATLAB without loops or signal processing toolbox

  - by Doresoom

  I need to implement a mean filter on a data set, but I don't have access to the signal processing toolbox. Is there a way to do this without using a for loop? Here's the code I've got working: x=0:.1:10*pi; noise=0.5*(rand(1,length(x))-0.5); y=sin(x)+noise; %generate noisy signal a=10; %specify moving window size my=zeros(1,length(y)-a); for n=a/2+1:length(y)-a/2 my(n-a/2)=mean(y(n-a/2:n+a/2)); %calculate mean for each window end mx=x(a/2+1:end-a/2); %truncate x array to match plot(x,y) hold on plot(mx,my,'r')

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• Android drawCircle's are not always 360 degrees

  - by user329999

  When I call drawCircle (ex. canvas.drawCircle(x, y, r, mPaint);) and I use Paint Style STROKE to initialize param #4 mPaint, the result doesn't quite make a full 360 degree (2*PI radian) circle in all cases. Sometimes you get a full circle (as I would expect) and sometimes only an arc. Does someone have an idea what would cause this to happen? I don't know what cases work and which don't (yet). I've noticed the ones that don't work seem to be the larger circles I'm drawing (100.0 radius). Could be size related. I am using floating point for x, y and r. I could try rounding to the nearest int when in the drawing code.

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• CodePlex Daily Summary for Wednesday, February 23, 2011

  CodePlex Daily Summary for Wednesday, February 23, 2011Popular ReleasesSQL Server CLR Function for Address Correction and Geocoding: Release 2.1: Adds support for the User Key argument in Process function calls.ClosedXML - The easy way to OpenXML: ClosedXML 0.45.2: New on this release: 1) Added data validation. See Data Validation 2) Deleting or clearing cells deletes the hyperlinks too. New on v0.45.1 1) Fixed issues 6237, 6240 New on v0.45.2 1) Fixed issues 6257, 6266 New Examples Data ValidationCrystalbyte Equinox (LINQ to IMAP): Equinox Alpha Release v0.3.0.0: Fixed bugsFixed issue introduced in last release; No connection could be established since the client did not read the welcome message during the initial connection attempt. Contact names are now being properly parsed into the envelope Introduced featuresImplemented SMTP support, the client is contained inside the Crystalbyte.Equinox.Smtp.dll which was added to the current release.OMEGA CMS: OMEGA CMA - Alpha 0.2: A few fixes for OMEGA Framework (DLL) A few tweeks for OMEGA CMSJSLint for Visual Studio 2010: 1.2.4: Bug Fix release.Coding4Fun Tools: Coding4Fun.Phone.Toolkit v1.2: New control, Toast Prompt! Removed progress bar since Silverlight Toolkit Feb 2010 has it.Umbraco CMS: Umbraco 4.7: Service release fixing 31 issues. A full changelog will be available with the final stable release of 4.7 Important when upgradingUpgrade as if it was a patch release (update /bin, /umbraco and /umbraco_client). For general upgrade information follow the guide found at http://our.umbraco.org/wiki/install-and-setup/upgrading-an-umbraco-installation 4.7 requires the .NET 4.0 framework Web.Config changes Update the web web.config to include the 4 changes found in (they're clearly marked in...HubbleDotNet - Open source full-text search engine: V1.1.0.0: Add Sqlite3 DBAdapter Add App Report when Query Cache is Collecting. Improve the performance of index through Synchronize. Add top 0 feature so that we can only get count of the result. Improve the score calculating algorithm of match. Let the score of the record that match all items large then others. Add MySql DBAdapter Improve performance for multi-fields sort . Using hash table to access the Payload data. The version before used bin search. Using heap sort instead of qui...Silverlight????[???]: silverlight????[???]2.0: ???????，?????，????????silverlight????。DBSourceTools: DBSourceTools_1.3.0.0: Release 1.3.0.0 Changed editors from FireEdit to ICSharpCode.TextEditor. Complete re-vamp of Intellisense ( further testing needed). Hightlight Field and Table Names in sql scripts. Added field dropdown on all tables and views in DBExplorer. Added data option for viewing data in Tables. Fixed comment / uncomment bug as reported by tareq. Included Synonyms in scripting engine ( nickt_ch ).IronPython: 2.7 Release Candidate 1: We are pleased to announce the first Release Candidate for IronPython 2.7. This release contains over two dozen bugs fixed in preparation for 2.7 Final. See the release notes for 60193 for details and what has already been fixed in the earlier 2.7 prereleases. - IronPython TeamCaliburn Micro: A Micro-Framework for WPF, Silverlight and WP7: Caliburn.Micro 1.0 RC: This is the official Release Candicate for Caliburn.Micro 1.0. The download contains the binaries, samples and VS templates. VS Templates The templates included are designed for situations where the Caliburn.Micro source needs to be embedded within a single project solution. This was targeted at government and other organizations that expressed specific requirements around using an open source project like this. NuGet This release does not have a corresponding NuGet package. The NuGet pack...Caliburn: A Client Framework for WPF and Silverlight: Caliburn 2.0 RC: This is the official Release Candidate for Caliburn 2.0. It contains all binaries, samples and generated code docs.Chiave File Encryption: Chiave 0.9: Application for file encryption and decryption using 512 Bit rijndael encyrption algorithm with simple to use UI. Its written in C# and compiled in .Net version 3.5. It incorporates features of Windows 7 like Jumplists, Taskbar progress and Aero Glass. Feedbacks are Welcome!....Rawr: Rawr 4.0.20 Beta: Rawr is now web-based. The link to use Rawr4 is: http://elitistjerks.com/rawr.phpThis is the Cataclysm Beta Release. More details can be found at the following link http://rawr.codeplex.com/Thread/View.aspx?ThreadId=237262 As of the 4.0.16 release, you can now also begin using the new Downloadable WPF version of Rawr!This is a pre-alpha release of the WPF version, there are likely to be a lot of issues. If you have a problem, please follow the Posting Guidelines and put it into the Issue Trac...PowerGUI Visual Studio Extension: PowerGUI VSX 1.3.2: New FeaturesPowerGUI Console Tool Window PowerShell Project Type PowerGUI 2.4 SupportMiniTwitter: 1.66: MiniTwitter 1.66 ???? ?? ?????????? 2 ??????????????????? User Streams ?????????Windows Phone 7 Isolated Storage Explorer: WP7 Isolated Storage Explorer v1.0 Beta: Current release features:WPF desktop explorer client Visual Studio integrated tool window explorer client (Visual Studio 2010 Professional and above) Supported operations: Refresh (isolated storage information), Add Folder, Add Existing Item, Download File, Delete Folder, Delete File Explorer supports operations running on multiple remote applications at the same time Explorer detects application disconnect (1-2 second delay) Explorer confirms operation completed status Explorer d...Image.Viewer: 2011: First version of 2011Silverlight Toolkit: Silverlight for Windows Phone Toolkit - Feb 2011: Silverlight for Windows Phone Toolkit OverviewSilverlight for Windows Phone Toolkit offers developers additional controls for Windows Phone application development, designed to match the rich user experience of the Windows Phone 7. Suggestions? Features? Questions? Ask questions in the Create.msdn.com forum. Add bugs or feature requests to the Issue Tracker. Help us shape the Silverlight Toolkit with your feedback! Please clearly indicate that the work items and issues are for the phone t...New Projects.Net Dating & Social Software Suite: A free, open source dating and social software suite. Dot Net Dating Suite uses the latest features in .Net combined with experienced developers efforts. This allows us to deliver professional public SEO websites with the support of an enterprise enabled administration suite.AllegroSharp: Biblioteka zapewniajaca obsluge serwisu aukcyjnego Allegro.pl w oparciu o udostepniona publicznie usluge Allegro Web API.asdfasdfasdf: asdfasdfasdfauto: auto siteAWS Monitor: A web app utilizing the Amazon Web Services API with a focus on browsing through and analyzing data graphically, mostly from CloudWatch - the API providing metrics about the usage of all the Amazon Web Services such as EC2 (Cloud Computing) and ELB (Elastic Load Balancing).Calculation of FEM using DirectX Libraries: Calculation of FEM using DirectX LibrariesCART: System CART (Creative Application to Remedy Traffics) poprawi przepustowosc infrastruktury drogowej i plynnosci ruchu pojazdów w aglomeracjach miejskich. Chaining Assertion for MSTest: Chaining Assertion for MSTest. Simpleness Assert Extension Method on Object. This provides only one .cs file.CodeFirst Membership Provider: Custom Membership Provider based on SimpleMembershipProvider using Entity Framework Code-First, intended for use in ASP.NET MVC 3. Thanks to ASP.NET Web Pages team for building a simple membership provider :PFourSquareSharp: Simple OAuth2 Implementation of FourSquare API in .NETHelix Engine: The Helix Engine is an Isometric Rendering Engine for SilverlightLighthouse - Versatile Unit Test Runner for Silverlight: Lighthouse provides you with set of simple but powerful tools to run Silverlight Unit Tests from Command Line, Windows Test Runner Application and from Resharper plugin for Visual Studio.MISCE: Designs for a Minimal Instruction Set Computer for Education along with a simulator/compiler written in Excel. A computer "from first principles" that utilises a minimal instruction set and can be built for demonstration purposes as part of a technology or computing course. Oh My Log: Oh My Log inventorises eventlog files from Windows Servers in a network. Clean and simple sysadmin tool. OSIS Interop Tests: These are the tests created for use by the OSIS working group (http://osis.idcommons.net) to test interoperability features of user-centric solutions during interop events.Program Options: Parse command line optionsSearchable Property Updater for Microsoft Dynamics CRM 2011: Searchable Property Updater makes it easier for Microsoft Dynamics CRM 2011 customizers to bulk change the "Active for advanced find" property of entities attributesSilverlight Bolo: silverlight bolo cloneSimulacia a vizualizacia vlasov: simulacia a vizualizacia vlasov pomocou GPUSmartkernel: Smartkernel:Framework,Example,Platform,Tool,AppSusuCMS: SusuCMSSwimlanes for Scrum: Swimlanes Taskboard for Scrum Team Projects with TFS setup using SfTS (Scrum for Team System) V3 templateteamdoer: These are the actual source codes that power teamdoer.com - a simple collaborative task/project management software apptiencd: Tiencd projectVG Current Item Display Web Part: VG Current Item Display Web Part allows to display current SharePoint item metadata. For example if you put it on to the Web Part page or list item form it will display the custom view of the current item properties. Output is easily customized with XSLT file.Virtual Interactive Shopper: Addin for SeeMe Rehabilitation System. More information about the SeeMe system can be found at http://www.brontesprocessing.com/health/SeeMeVisual Studio Strategy Manager: Provide a way to create code generation strategies and to manage them in Visual Studio 2010. Strategies can interact with Visual Studio events like document events (saved, closed, opened), building event or DSL Tools events (model element created, deleted, modified..).VMarket: <project name>VMarket</project name> <programming language>asp.net</programming language> <project description> VMarket is virtual market systems which allow users to act as seller or buyer and manage their property online </project description>webclerk: webclerk's project based on microsoft techWebTest: Just Test!Work efficiency (WE) ????????: Work efficiency ???????? ????： ???? ????zrift: nothing here, move along

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• Using Taylor Polynomials Programmatically in Maple

  - by kzh

  I am trying to use a Taylor polynomial programmatically in Maple, but the following does not seem to work... T[6]:=taylor(sin(x),x=Pi/4,6);convert(T[6], polynom, x); f:=proc(x) convert(T[6], polynom, x); end proc; f(1); All of the following also do not work: f:=convert(T[6], polynom); f:=convert(T[6], polynom, x); f:=x->convert(T[6], polynom); f:=x->convert(T[6], polynom, x);. Is there a way of doing this without copying and pasting the output of convert into the definition of f?

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• create a wav file from multiple wav files in delphi

  - by Bayu

  i' ve a problem in doing my final project... i'm having trouble with how to save multiple wav files into 1 wav file.. let's take an example: i have 3 wav files which are the syllables of the word "hospital" : "hos.wav", "pi.wav", and "tal.wav" (sorry if i'm wrong in determining the syllables of the words).. each of those syllable wav files contains utterances of the syllables of the word "hospital" respectively.. my task is to merge those files so that the word hospital could be reproduced from those files. and then to save the merged file to be a new wav file, let say "hospital.wav"..I've done my first task, but not with my second task... does anyone can help me? thx b4..

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• Optimize SUMMARIZE with ADDCOLUMNS in Dax #ssas #tabular #dax #powerpivot

  - by Marco Russo (SQLBI)

  If you started using DAX as a query language, you might have encountered some performance issues by using SUMMARIZE. The problem is related to the calculation you put in the SUMMARIZE, by adding what are called extension columns, which compute their value within a filter context defined by the rows considered in the group that the SUMMARIZE uses to produce each row in the output. Most of the time, for simple table expressions used in the first parameter of SUMMARIZE, you can optimize performance by removing the extended columns from the SUMMARIZE and adding them by using an ADDCOLUMNS function. In practice, instead of writing SUMMARIZE( <table>, <group_by_column>, <column_name>, <expression> ) you can write: ADDCOLUMNS(     SUMMARIZE( <table>, <group by column> ),     <column_name>, CALCULATE( <expression> ) ) The performance difference might be huge (orders of magnitude) but this optimization might produce a different semantic and in these cases it should not be used. A longer discussion of this topic is included in my Best Practices Using SUMMARIZE and ADDCOLUMNS article on SQLBI, which also include several details about the DAX syntax with extended columns. For example, did you know that you can create an extended column in SUMMARIZE and ADDCOLUMNS with the same name of existing measures? It is *not* a good thing to do, and by reading the article you will discover why. Enjoy DAX!

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• Looking for calculator source code, BSD-licensed

  - by Horace Ho

  I have an urgent project which need many functions of a calculator (plus a few in-house business rule formulas). As I won't have time to re-invent the wheel so I am looking for source code directly. Requirements: BSD licensed (GPL won't help) in c/c++ programming language 32-bit CPU minimum dependency on platform API/data structure best with both RPN and prefix notation supported emulator/simulator code also acceptable (if not impossible to add custom formula) with following functions (from wikipedia) Scientific notation for calculating large numbers floating point arithmetic logarithmic functions, using both base 10 and base e trigonometry functions (some including hyperbolic trigonometry) exponents and roots beyond the square root quick access to constants such as pi and e plus hexadecimal, binary, and octal calculations, including basic Boolean math fractions optional statistics and probability calculations complex numbers programmability equation solving

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• Don’t miss the Oracle Webcast: Enabling Effective Decision Making with “One Source of the Truth” at BB&T

  - by Rob Reynolds

  Webcast Date:  September 17th, 2012  -  9 a.m. PT / 12 p.m. ET  BB&T Corporation (NYSE: BBT) is one of the largest financial services holding companies in the United States. One of their IT goals is to provide “one source of truth” to enable more effective decision making at the corporate and local level. By using Oracle’s Hyperion Enterprise Planning Suite and Oracle Essbase, BB&T streamlined their planning and financial reporting processes. Large volumes of data were consolidated into a single reporting solution giving stakeholders more timely and accurate information. By providing a central and automated collaboration tool, BB&T is able to prepare more accurate financial forecasts, rapidly consolidate large amounts of data, and make more informed decisions. Join us on September 17th for a live webcast to hear BB&T’s journey to achieve “One Source of Truth” and learn how Oracle’s Hyperion Planning Suite and Oracle’s Essbase allows you to: Adopt best practices like rolling forecasts and driver-based planning Reduce the time and effort dedicated to the annual budget process Reduce the time and effort dedicated to the annual budget process Remove forecasting uncertainty with predictive modeling capabilities Rapidly analyze shifting market conditions with a powerful calculation engine Prioritize resources effectively with complete visibility into all potential risks Link strategy and execution with integrated strategic, financial and operational planning Register here.

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• 45° Slopes in a Tile based 2D platformer

  - by xNidhogg

  I want to have simple 45° slopes in my tile based platformer, however I just cant seem to get the algorithm down. Please take a look at the code and video, maybe I'm missing the obvious? //collisionRectangle is the collision rectangle of the player with //origin at the top left and width and height //wantedPosition is the new position the player will be set to. //this is determined elsewhere by checking the bottom center point of the players rect if(_leftSlope || _rightSlope) { //Test bottom center point var calculationPoint = new Vector2(collisionRectangle.Center.X, collisionRectangle.Bottom); //Get the collision rectangle of the tile, origin is top-left Rectangle cellRect = _tileMap.CellWorldRectangle( _tileMap.GetCellByPixel(calculationPoint)); //Calculate the new Y coordinate depending on if its a left or right slope //CellSize = 8 float newY = _leftSlope ? (calculationPoint.X % CellSize) + cellRect.Y : (-1 * (calculationPoint.X % CellSize) - CellSize) + cellRect.Y; //reset variables so we dont jump in here next frame _leftSlope = false; _rightSlope = false; //now change the players Y according to the difference of our calculation wantedPosition.Y += newY - calculationPoint.Y; } Video of what it looks like: http://youtu.be/EKOWgD2muoc

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• Why i can not load a simple pixel shader effect (. fx) file in xna?

  - by Mehdi Bugnard

  I just want to load a simple *.fx file into my project to make a (pixel shader) effect. But whenever I try to compile my project, I get the following error in visual studio Error List: Errors compiling .. ID3DXEffectCompiler: There were no techniques ID3DXEffectCompiler: Compilation failed I already searched on google and found many people with the same problem. And I realized that it was a problem of encoding. With the return lines unrecognized '\ n' . I tried to copy and paste to notepad and save as with ASCII or UTF8 encoding. But the result is always the same. Do you have an idea please ? Thanks a looot :-) Here is my [.fx] file : sampler BaseTexture : register(s0); sampler MaskTexture : register(s1) { addressU = Clamp; addressV = Clamp; }; //All of these variables are pixel values //Feel free to replace with float2 variables float MaskLocationX; float MaskLocationY; float MaskWidth; float MaskHeight; float BaseTextureLocationX; //This is where your texture is to be drawn float BaseTextureLocationY; //texCoord is different, it is the current pixel float BaseTextureWidth; float BaseTextureHeight; float4 main(float2 texCoord : TEXCOORD0) : COLOR0 { //We need to calculate where in terms of percentage to sample from the MaskTexture float maskPixelX = texCoord.x * BaseTextureWidth + BaseTextureLocationX; float maskPixelY = texCoord.y * BaseTextureHeight + BaseTextureLocationY; float2 maskCoord = float2((maskPixelX - MaskLocationX) / MaskWidth, (maskPixelY - MaskLocationY) / MaskHeight); float4 bitMask = tex2D(MaskTexture, maskCoord); float4 tex = tex2D(BaseTexture, texCoord); //It is a good idea to avoid conditional statements in a pixel shader if you can use math instead. return tex * (bitMask.a); //Alternate calculation to invert the mask, you could make this a parameter too if you wanted //return tex * (1.0 - bitMask.a); }

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• An Overview of Batch Processing in Java EE 7

  - by Janice J. Heiss

  Up on otn/java is a new article by Oracle senior software engineer Mahesh Kannan, titled “An Overview of Batch Processing in Java EE 7.0,” which explains the new batch processing capabilities provided by JSR 352 in Java EE 7. Kannan explains that “Batch processing is used in many industries for tasks ranging from payroll processing; statement generation; end-of-day jobs such as interest calculation and ETL (extract, load, and transform) in a data warehouse; and many more. Typically, batch processing is bulk-oriented, non-interactive, and long running—and might be data- or computation-intensive. Batch jobs can be run on schedule or initiated on demand. Also, since batch jobs are typically long-running jobs, check-pointing and restarting are common features found in batch jobs.” JSR 352 defines the programming model for batch applications plus a runtime to run and manage batch jobs. The article covers feature highlights, selected APIs, the structure of Job Scheduling Language, and explains some of the key functions of JSR 352 using a simple payroll processing application. The article also describes how developers can run batch applications using GlassFish Server Open Source Edition 4.0. Kannan summarizes the article as follows: “In this article, we saw how to write, package, and run simple batch applications that use chunk-style steps. We also saw how the checkpoint feature of the batch runtime allows for the easy restart of failed batch jobs. Yet, we have barely scratched the surface of JSR 352. With the full set of Java EE components and features at your disposal, including servlets, EJB beans, CDI beans, EJB automatic timers, and so on, feature-rich batch applications can be written fairly easily.” Check out the article here.

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• Selling Android apps from Latvia? or should I just put banners?

  - by Roger Travis

  I am in Latvia ( which is not supported to sell apps at android market ), so I am thinking about the best way of monetizing my app. So far I've come up with such options: somehow imitate that I am from a supported country, get a bank account there, etc. use PayPal for in-app purchases. The player get, say, first 10 levels for free, but then is asked to pay 0.99$ for the rest of the game. downsides: player might not feel comfortable entering his paypal details into an app. also android market might not really like that. making the app free and get money from advertising... let's do some calculation here, say, I get 1m free downloads, each user during his playtime would see 10 banners, therefor 10m / 1000 * 0.3 = gives roughly 33k$ ( if we use adMob with their 0.3$ per 1000 impressions ). On the other hand, if we use paypal in app purchase, we need a 3% or more conversion rate to beat this... hmm... What do you think about all this? Thanks! edit: from what I just read all over the net, it looks like advertisers will change their eCPM price a lot without you understanding why... while using in-app paypal purchase you can at least somehow monitor the cashflow.

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• Problems running Java SWT application. Is this something to do with 64 vs 32-bit libraries?

  - by ?????

  I'm getting started with SWT Exception in thread "main" java.lang.UnsatisfiedLinkError: no swt-cocoa-3557 or swt-cocoa in swt.library.path, java.library.path or the jar file at org.eclipse.swt.internal.Library.loadLibrary(Unknown Source) at org.eclipse.swt.internal.Library.loadLibrary(Unknown Source) at org.eclipse.swt.internal.C.<clinit>(Unknown Source) at org.eclipse.swt.internal.cocoa.NSThread.isMainThread(Unknown Source) at org.eclipse.swt.graphics.Device.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.getDefault(Unknown Source) at com.astrobetty.getotagdesktop.MainUIWindow.main(MainUIWindow.java:110) I've carefully followed the directions here http://www.eclipse.org/swt/eclipse.php I can see libswt-awt-cocoa-3557.jnilib, libswt-cocoa-3557.jnilib, libswt-pi-cocoa-3557.jnilib clearly listed under "Referenced Libraries" in my Eclipse package explorer. Presumably, that should make them available on the classpath when I select the java module that contains "main" and do a "run as" application. What's the problem? I suspect it may be related to 64-bit vs 32-bit VMs....

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• AABB Sweeping, algorithm to solve "stacking box" problem

  - by Ivo Wetzel

  I'm currently working on a simple AABB collision system and after some fiddling the sweeping of a single box vs. another and the calculation of the response velocity needed to push them apart works flawlessly. Now on to the new problem, imagine I'm having a stack of boxes which are falling towards a ground box which isn't moving: Each of these boxes has a vertical velocity for the "gravity" value, let's say this velocity is 5. Now, the result is that they all fall into each other: The reason is obvious, since all the boxes have a downward velocity of 5, this results in no collisions when calculating the relative velocity between the boxes during sweeping. Note: The red ground box here is static (always 0 velocity, can utilize spatial partitioning ), and all dynamic static collisions are resolved first, thus the fact that the boxes stop correctly at this ground box. So, this seems to be simply an issue with the order the boxes are sweept against each other. I imagine that sorting the boxes based on their x and y velocities and then sweeping these groups correctly against each other may resolve this issues. So, I'm looking for algorithms / examples on how to implement such a system. The code can be found here: https://github.com/BonsaiDen/aabb The two files which are of interest are [box/Dynamic.lua][3] and [box/Manager.lua][4]. The project is using Love2D in case you want to run it.

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• ORAchk 2.2.5 – New Tool Features & New Health Checks for the Oracle Stack

  - by SamanthaF-Oracle

  ORAchk version 2.2.5 is now available for download, new features in 2.2.5: Running checks for multiple databases in parallel Ability to schedule multiple automated runs via ORAchk daemon New "scratch area" for ORAchk temporary files moved from /tmp to a configurable $HOME directory location System health score calculation now ignores skipped checks Checks the health of pluggable databases using OS authentication New report section to report top 10 time consuming checks to be used for optimizing runtime in the future More readable report output for clusterwide checks Includes over 50 new Health Checks for the Oracle Stack Provides a single dashboard to view collections across your entire enterprise using the Collection Manager, now pre-bundled Expands coverage of pre and post upgrade checks to include standalone databases, with new profile options to run only these checks Expands to additional product areas in E-Business Suite of Workflow & Oracle Purchasing and in Enterprise Manager Cloud Control ORAchk has replaced the popular RACcheck tool, extending the coverage based on prioritization of top issues reported by users, to proactively scan for known problems within the area of: Oracle Database Standalone Database Grid Infrastructure & RAC Maximum Availability Architecture (MAA) Validation Upgrade Readiness Validation Golden Gate Enterprise Manager Cloud Control Repository E-Business Suite Oracle Payables (R12 only) Oracle Workflow Oracle Purchasing (R12 only) Oracle Sun Systems Oracle Solaris ORAchk features: Proactively scans for the most impactful problems across the various layers of your stack Streamlines how to investigate and analyze which known issues present a risk to you Executes lightweight checks in your environment, providing immediate results with no configuration data sent to Oracle Local reporting capability showing specific problems and their resolutions Ability to configure email notifications when problems are detected Provides a single dashboard to view collections across your entire enterprise using the Collection Manager ORAchk will expand in the future with high impact checks in existing and additional product areas. If you have particular checks or product areas you would like to see covered, please post suggestions in the ORAchk subspace in My Oracle Support Community. For more details about ORAchk see Document 1268927.2

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• [Strange problem] ASP.NET MVC 2.0 RTM cannot work with VWD 2008 Express on a new Windows 7 Pro

  - by silent

  The MVC 2.0 RTM works great on my old Vista machine with VWD 2008 Express, but I just bought a new computer with Windows 7 Pro, installed VWD 2008 Express SP1 and MVC 2.0 RTM by using Web PI 2.0. but after installation, I found the VWD doesn't have any MVC options, that means I can't either create new MVC projects or compile existing MVC projects. Why? What other steps I need to do to make it work? I'm sure the MVC has been installed properly since my MVC site on the new computer works well (so the IIS side has no problem), just the VWD can't 'realize' that the MVC framework is already installed... (tried to uninstall and install many times, but won't work)

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• DIVIDE vs division operator in #dax

  - by Marco Russo (SQLBI)

  Alberto Ferrari wrote an interesting article about DIVIDE performance in DAX. This new function has been introduced in SQL Server Analysis Services 2012 SP1, so it is available also in Excel 2013 (which still doesn’t have other features/fixes introduced by following Cumulative Updates…). The idea that instead of writing: IF ( Sales[Quantity] <> 0, Sales[Amount] / Sales[Quantity], BLANK () ) you can write: DIVIDE ( Sales[Amount], Sales[Quantity] ) There is a third optional argument in DIVIDE that defines the result in case the denominator (second argument) is zero, and by default its value is BLANK, so I omitted the third argument in my example. Using DIVIDE is very important, especially when you use a measure in MDX (for example in an Excel PivotTable) because it raise the chance that the non empty evaluation for the result is evaluated in bulk mode instead of cell-by-cell. However, from a DAX point of view, you might find it’s better to use the standard division operator removing the IF statement. I suggest you to read Alberto’s article, because you will find that an expression applying a filter using FILTER is faster than using CALCULATE, which is against any rule of thumb you might have read until now! Again, this is not always true, and depends on many conditions – trying to simplify, we might say that for a simple calculation, the query plan generated by FILTER could be more efficient – but, as usual, it depends, and 90% of the times using FILTER instead of CALCULATE produces slower performance. Do not take anything for granted, and always check the query plan when performance are your first issue!

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• Traffic estimation for a multiplayer flash game

  - by Steve Addington

  hey, i want to know if my rough traffic estimations are right, it would be for a pretty simple realtime flashgame in the style of haxball (but not as a soccer game) heres a video of it http://www.youtube.com/watch?v=z_xBdFg1RcI So here comes my estimation, i dont know if they are realistic! i hope someone can help me. consider the packet attached as a typical one sent every 200ms, its 148bytes + 64 bytes of header will make around a 200bytes packet. The server will receive 200bytes x 6 players x 5 times a sec=6000bytes/s=5.85Kbytes/s=46.9kbit/s plus he has to send all back to the players, so at this point are 94Kbit/s.The server received all the information, perform the definitive calculation and send the new position to all players, in a bigger packet of around 900bytes that have to be delivered to the others 6, which makes 900bytes x 6 players x 5 times a sec=27000bytes/s=26Kbytes/s=210kbit/s. overall that would be 26kbyte per second. thats like 130mb traffic per hour for a 6player room. but somehow i think the numbers are too high? that would be really much traffic for such a simple game. did i calculate something wrong?

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• How to convert from K&R C to ANSI C?

  - by Vadakkumpadath

  I am trying to execute following code which is the 1988 entry of Obfuscated C Code Contest. #define _ -F<00||--F-OO--; int F=00,OO=00;main(){F_OO();printf("%1.3f\n",4.*-F/OO/OO);}F_OO() { _-_-_-_ _-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_ _-_-_-_ } From entry description, this code is calculating pi by looking at its own area. I successfully compiled it without changing the code. But when I executed, it is giving me a value 0.25, what I am expecting is 3.14. Code description says it is in K&R C and it doesn't work correctly in ANSI C without some change. I think I have to do those modification to execute it properly. I don't have any previous experience with K&R C. So can someone help me to change above code to ANSI C or point to the problems if any. I am using Microsoft Visual Studio 2008 to execute this.

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