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• Node.js for lua?

  - by Shahbaz

  I've been playing around with node.js (nodejs) for the past few day and it is fantastic. As far as I can tell, lua doesn't have a similar integration of libev and libio which let's one avoid almost any blocking calls and interact with the network and the filesystem in an asynchronous manner. I'm slowly porting my java implementation to nodejs, but I'm shocked that luajit is much faster than v8 JavaScript AND uses far less memory! I imagine writing my server in such an environment (very fast and responsive, very low memory usage, very expressive) will improve my project immensly. Being new to lua, I'm just not sure if such a thing exists. I'll appreciate any pointers. Thanks

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• C++ - dynamic pointer of array

  - by Eagle

  Hi to all, first i would like to say i am Newbie in C++. As part of my master thesis i am writing a program in C++ which also get as parameters the variables m and d (both integers). Were d is the power of 2 (this means 2^d elements). Parameter m define the number of possible interactions between one element and the total group (2^d elements). The number of possible interactions is computed as following: \kappa = \sum_{i=0}^m\binom{d}{i} (at present i generate vector of vectors for 2^d x \kappa, but my Prof. would like me to create different statistics to different m's. My first though was to to generate a dynamic array of m arrays of different sizes... Then i though of defining a 3-dim array with the biggest needed 2d array, but also program speed is important (e.g d = 20). i would like to ask for your advice how to define such kind of dynamic array that will also be fast. Regards

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• How to determine Scale of Line Graph based on Pixels/Height?

  - by Dexter

  I have a problem due to my terrible math abilities, that I cannot figure out how to scale a graph based on the maximum and minimum values so that the whole graph will fit onto the graph-area (400x420) without parts of it being off the screen (based on a given equation by user). Let's say I have this code, and it automatically draws squares and then the line graph based on these values. What is the formula (what do I multiply) to scale it so that it fits into the small graphing area? vector<int> m_x; vector<int> m_y; // gets automatically filled by user equation or values int HeightInPixels = 420;// Graphing area size!! int WidthInPixels = 400; int best_max_y = GetMaxOfVector(m_y); int best_min_y = GetMinOfVector(m_y); m_row = 0; m_col = 0; y_magnitude = (HeightInPixels/(best_max_y+best_min_y)); // probably won't work magnitude = (WidthInPixels/(int)m_x.size()); m_col = m_row = best_max_y; // number of vertical/horizontal lines to draw ////x_magnitude = (WidthInPixels/(int)m_x.size())/2; Doesn't work well ////y_magnitude = (HeightInPixels/(int)m_y.size())/2; Doesn't work well ready = true; // we have values, graph it Invalidate(); // uses WM_PAINT

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• Every 3rd Insert Is Slow On Ms Sql 2008

  - by Chris

  I have a function that writes 3 lines into a empty table like so: INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (1, 8, 1) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (2, 8, 4) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (3, 8, 3) For some reason only the third query takes a long time to execute - and with each insert it grows longer. Profiler Image I have tried disabling all constraints on the table - same result. I just can't figure out why the first two would run so fast - and the last one would take so long. Any help would be greatly appreciated. Here is the statistics for a query ran MSSMS: Query: ALTER TABLE [dbo].[yaf_ForumAccess] NOCHECK CONSTRAINT ALL INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (1, 9, 1) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (2, 9, 4) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (3, 9, 3) ALTER TABLE [dbo].[yaf_ForumAccess] CHECK CONSTRAINT ALL Stats: Stats

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• Delphi: How to diagnose sluggish UI?

  - by Ian Boyd

  i have a form, which you can pretend is laid out like Windows Explorer: panel on the left splitter client panel +------------+#+-----------------------+ | |#| | | |#| | | |#| | | |#| | | Left |#| Client | | |#| | | |#| | | |#| | | |#| | | |#| | +------------+#+-----------------------+ ^ | +----splitter The the left and client area panels are each rich with controls. The problem is that using the splitter is very sluggish. i would expect that a modern 2 GHz computer can re-display the form as fast as a human can push the mouse around. But that's definitely not the case, and it takes about 200-300 ms before the form is fully re-adjusted. The form has about 100 visual controls on it, no code, or custom controls. How do i go about tracing who's the cause of the sluggishness?

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• The next step & technology towards web services.

  - by webzide

  Hi, My name is Dennis and I am pretty ambitious of creating the next big thing for the web. I have ideas but now I gotta get to work to learn the tools. I am learning Javascript. I don't know if next step for me to take is PHP or some suggests RUBY on Rails. What are the pros and cons. With your experience, I wish you could hint me to the right direction. Thanks. I don't mind working hard. My goal is to create a comprehensive and secure web service platform as well as a fast and user friendly UI.

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• http streaming using java servlet

  - by Shamik

  I have a servlet based web application which produces two sets of data. One set of data in the webpage which is essential and other set which is optional. I would like to render the essential data as fast as possible and then stream the optional data. I was thinking of writing the essential data to the output stream of HttpServletRequest and then call HttpServletRequest.flushBuffer() to commit the response to the client, but do not return from the servlet code, but instead create the optional data , write that to the outputstream again and then return from servlet code. What are the things that could go wrong in this scheme ? Is this a standard practice to achieve this goal?

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• Dev efforts for different mobile platforms

  - by Juriy

  Hello guys, I'm in the middle of development of a client-server "socializing" that is supposed to run on several mobile devices. The project is pretty complex, involving networking, exchanging media, using geolocation services, and nice user UI. In terms of development efforts, technical risks and extensibility what is the best platform to start with? Taking into the account that the goal is go "live" as fast as possible with the mobile version. And second goal is to cover most users (but first is more important). iPhone (iPod iPad) Android BlackBerry Java ME, Symbian I realize that there are limitations on every platform, and there are different aspects to take into the account (for example iPhone has better developer's community then Android, J2ME runs in a terrible sandbox but covers most devices). Please share your pros and cons. I have the experience only with J2ME, unfortunately I can't evaluate other platforms.

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• What is the technological basis for Azure DocumentDB?

  - by user1703840

  Microsoft announced the availability of Azure DocumentDB as follows... A fully-managed, highly-scalable, NoSQL document database service. - Rich query over a schema-free JSON data model - Transactional execution of JavaScript logic - Scalable storage and throughput - Tunable consistency - Rapid development with familiar technologies - Blazingly fast and write optimized database service I really like the "transactional execution of JavaScript logic". Sounds like an approach similar to that of PostgreSQL NoSQL. Anyone know what is the technological basis for the Azure DocumentDB service? SQL Server?

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• Smooth table view like on iPod.app

  - by Gilo

  Hey folks ;), Im trying to redo the table view in the ipod.app. The one with 2 labels and the cover on the left. I want the same information there. I mean the cover plus all the other MPMediaItem stuff. Everything works fine. I can build the table and get all the information from the music library I need. My only problem is that my table is far away from being smooth. It lacks. When I remove the MPMediaArtworkItem from the table its super fast. So I guess its a problem with that. Is there any way to load the MPMediaProperties more faster? Whats the fastest way? THX in advance :)

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• measuring performance - using real clicks vs "ab" command

  - by shanyu

  I have a web site in closed beta, developed in Django, runs with Mysql on Debian. In the last few days, the main page has been showing a slowdown. For every ten clicks, one or two receives extremely slow response (10 secs or more), others are as fast as they used to be. When I was searching for the problem, I ran into this issue that I couldn't grasp: top command shows that when I request the main page, mysql shoots up to 90% - 100% cpu usage. I get the page just as the cpu use gets back to normal. So, I thought, it is db. Then I called ab with parameters -n 1000 -c 5, I got decent performance, about 100 pages per second, just as it was before the slowdown. I would imagine a worse performance as 10-20% of requests take 10 secs to load. Is this conflict between ab and "real" clicks normal, or am I using ab in a wrong configuration?

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• Test if element already has jQuery datepicker

  - by macca1

  I have a form with many input elements. Some are date fields with a jQuery UI datepicker alraedy attached: $("#someElement").mask("9?9/99/9999").datepicker({showOn: 'button', buttonText:'Click here to show calendar', duration: 'fast', buttonImageOnly: true, buttonImage: /images/calicon.gif' }); Then I have a key command bound to this function: function openCalendar() { var selection = document.activeElement; // { Need to test here if datepicker has already been initialized $(selection).datepicker("show"); // } } This works great for elements which already have the datepicker on them. However any other fields will throw a javascript error. I'm wondering the best way to test to see if datepicker has already been initialized on that field.

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• how to apply iddata into calculation?

  - by Sam

  I am trying to figure out how to combine the input and output data into the ARX model and then apply it into the BIC (Bayesian Information Criterion) formula. Below is the code that I am currently working on: for i=1:30; %% Set Model Order data=iddata(output,input,1); model = arx(data,[8 9 i]); yp = predict(model,data); ye = regress(data,yp{1,1}(1:4018,1)); M(i) = var(yp); BIC(i)=(N+i*(log(N)-1))/(N-i)*log(M(i)); end But it does not work. It keep on giving me an error something like below: "The syntax "Data{...}" is not supported. Use the "getexp" command to extract individual experiments from an IDDATA object." I did not understand what does that mean. Can someone explain it to me and where do I do wrong on my piece of code? Thanks in advance. Sam.

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• Fastest way to display a full calendar

  - by Aurélien Ribon

  Hello, I need to display a complete calendar (12 months, 31~ days/month) on screen. Currently, I'm using a 12-column grid, with each column filled with a "months" stackpanel. Each "month" stackpanel is filled with 31 (or less) day representations. Each day representation is composed of a DockPanel embedding three controls : a textblock to display the day letter a textblock to display the day number a textblock to display a short message Of course, performances are crushed down when I try to resize the window. Is there a useful trick to allow a fast display of many textblocks ?

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• Programming and art

  - by user353874

  Specialized software does play a major role in every business field. Games provide new realities and are proved child development tools. Communication got a new meaning. Information never traveled so fast. And programming is never referred to as an art form. Why is that? Programming is not romantic and not natural so we don't feel naturally attached to it. Basically, our emotions don't fit programming. But it's really cool and better than art. :D

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• Accelerometer gravity components

  - by Dvd

  Hi, I know this question is definitely solved somewhere many times already, please enlighten me if you know of their existence, thanks. Quick rundown: I want to compute from a 3 axis accelerometer the gravity component on each of these 3 axes. I have used 2 axes free body diagrams to work out the accelerometer's gravity component in the world X-Z, Y-Z and X-Y axes. But the solution seems slightly off, it's acceptable for extreme cases when only 1 accelerometer axis is exposed to gravity, but for a pitch and roll of both 45 degrees, the combined total magnitude is greater than gravity (obtained by Xa^2+Ya^2+Za^2=g^2; Xa, Ya and Za are accelerometer readings in its X, Y and Z axis). More detail: The device is a Nexus One, and have a magnetic field sensor for azimuth, pitch and roll in addition to the 3-axis accelerometer. In the world's axis (with Z in the same direction as gravity, and either X or Y points to the north pole, don't think this matters much?), I assumed my device has a pitch (P) on the Y-Z axis, and a roll (R) on the X-Z axis. With that I used simple trig to get: Sin(R)=Ax/Gxz Cos(R)=Az/Gxz Tan(R)=Ax/Az There is another set for pitch, P. Now I defined gravity to have 3 components in the world's axis, a Gxz that is measurable only in the X-Z axis, a Gyz for Y-Z, and a Gxy for X-Y axis. Gxz^2+Gyz^2+Gxy^2=2*G^2 the 2G is because gravity is effectively included twice in this definition. Oh and the X-Y axis produce something more exotic... I'll explain if required later. From these equations I obtained a formula for Az, and removed the tan operations because I don't know how to handle tan90 calculations (it's infinity?). So my question is, anyone know whether I did this right/wrong or able to point me to the right direction? Thanks! Dvd

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• Creating a variable-speed slideshow based on USB input on OSX.

  - by Dave A

  I have a friend who is trying to put together a geeky little contraption for a wedding, where people can view a slideshow. Neither of us use Macs, nor have programmed for one, but for various reasons it has to run on a Mac. There will be a USB ammeter hooked up to a bike dynamo. What we want is for a slideshow to be run, and advance at a speed relative to how fast someone is pedaling on a stationary bike. After much googling, it seems like we could load an iPhoto slideshow up via applescript. Is it possible to pause the slideshow and advance it with keypress commands? The applescript commands would be run via a bash script or similar that would monitor the value returned by the USB ammeter's command-line app and issue the keypress events accordingly. Is there some other app that could be likewise scripted to display photos?Hoping someone has some hints to get us started in the right direction! Thanks!

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• What things on a job listing should be avoided?

  - by Earlz

  Hello, I'm looking at trying my hand at a bit of freelancing. And looking at some of the listings, I can tell some of them are definitely, obviously wrong. "A web application mimicking youtube. Project must be completed in 2 weeks. Flat payment of $200. If you are not willing to do things this fast paced then do not apply" But some of them are more subtle and they give me a red flag inside, but I'm not sure to avoid them. What are some things in job listings to avoid for freelance programming jobs? What is the reason for avoiding that?

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• Slowness of Netbeans Platform Apps - how to mitigate?

  - by user559298

  Hi, We are developing a commerical application (pretty complex) in java using Netbeans IDE. We have 2 options in netbeans to create it- 1. Develop Java desktop app 2. Netbeans Platform app We have requirement that application startup and response times should be very very fast, should be modular etc. We did Proof of Technology by creating apps using both approaches mentioned above. We found Netbeans platform apps are very slow during startup and during screen navigation compared to pure Swing based desktop apps. We tried to implement suggestions provided at http://wiki.netbeans.org/Category:Performance:FAQ and in other blogs and forums to improve on speed of the app but were not successful. We feel for creating a complex desktop app Netbeans platform app would be better suited, but its not meeting our performance requirements (startup and response times, memory footprints, CPU usage guidelines etc). Can any one guide us on how to mitigate our problem of improving performance of Netbeans Platforms apps? Thanks in advance for your help. -bhan

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• Should XML be used server-side, and JSON client-side?

  - by Michel Carroll

  As a personal project, I'm making an AJAX chatroom application using XML as a server-side storage, and JSON for client-side processing. Here's how it works: AJAX Request gets sent to PHP using GET (chat messages/logins/logouts) PHP fetches/modifies the XML file on the server PHP encodes the XML into JSON, and sends back JSON response Javascript handles JSON information (chat messages/logins/logouts) I want to eventually make this a larger-scale chatroom application. Therefore, I want to make sure it's fast and efficient. Was this a bad design choice? In this case, is switching between XML and JSON ok, or is there a better way?

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• Finding matching submatrics inside a matrix

  - by DaveO

  I have a 100x200 2D array expressed as a numpy array consisting of black (0) and white (255) cells. It is a bitmap file. I then have 2D shapes (it's easiest to think of them as letters) that are also 2D black and white cells. I know I can naively iterate through the matrix but this is going to be a 'hot' portion of my code so speed is an concern. Is there a fast way to perform this in numpy/scipy? I looked briefly at Scipy's correlate function. I am not interested in 'fuzzy matches', only exact matches. I also looked at some academic papers but they are above my head.

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• What simple methods are there to wrap a c++ based object model with a COM interface

  - by Rich

  I have a pre-existing c++ object model which represents the business layer tier of an application. I want to be able to expose the object model to applications written in other languages i.e vbscript, VB, javascript etc. I believe the best way of doing this is to wrap the business objects with a COM layer. What fast and effective methods are there for doing this. Any advice, links to practical "How to" documentation would be very much appreciated. Because I'm starting a bounty on this , here's a few extra guidelines for potential bounty hunters :- 1)I've decided on an ATL approach 2)I'm now specifically looking for links to really good "how to and quickly" documentation on wrapping a pre-existing c++ object model to make it useable by a scripting language like javascript 3) Something with small working examples showing me what code needs to be added to what files, e.g what goes into the cpp , idl and hpp/h etc. It' must include an example I can compile test and change to get a better understanding.

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• Should I use Drupal or Kohana-type framework for a web "application"

  - by Andres

  The debate is that I need a PHP Framework/Drupal with the flexibility to add custom features to a potentially large application (web and with an api). However, with a framework, like Kohana, I see myself tackling and re-inventing the wheel with the simple stuff like account management and cms stuff. Account management and quick data collection, like fast form creation, are tedious in Kohana but appear incredible simple in Drupal. On the other hand, based on my limited Drupal experience, I doubt building rapid custom "features" and allowing users to create "groups" and to manage their own roles within those groups is something Drupal can easily accomplish. To simplify, is Drupal capable of true Web Applications; where the application is a service and provides custom results to each user? Can it provide a dashboard-like interface for users to change their settings or preferences? Can it aggregate data from particular users to provide better results/info to others? If so, please point me to some knowledge :-)

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• Most efficient way to save tile data of an isometric game

  - by Harmen

  Hello, I'm working on an isometric game for fast browsers that support <canvas>, which is great fun. To save information of each tile, I use a two-dimensional array which contains numbers representing a tile ID, like: var level = [[1, 1, 1, 2, 1, 0], [0, 1, 1, 2, 0, 1], [0, 1, 1, 2, 1, 1]]; var tiles = [ {name: 'grass', color: 'green'}, {name: 'water', color: 'blue'}, {name: 'forest', color: 'ForestGreen'} ]; So far it works great, but now I want to work with heights and slopes like in this picture: For each tile I need to save it's tile ID, height and information about which corners are turned upward. I came up with a simple idea about a bitwise representation of all four corners, like this: 1011 // top, bottom and left corner turned up My question is: what is the most efficient way to save these three values for each cell? Is it possible to save these three values as one integer?

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• Graph - strongly connected components

  - by HardCoder1986

  Hello! Is there any fast way to determine the size of the largest strongly connected component in a graph? I mean, like, the obvious approach would mean determining every SCC (could be done using two DFS calls, I suppose) and then looping through them and taking the maximum. I'm pretty sure there has to be some better approach if I only need to have the size of that component and only the largest one, but I can't think of a good solution. Any ideas? Thanks.

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