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  • Rails Book Suggestions [closed]

    - by Solomon081
    Possible Duplicate: Is there a canonical book on Ruby on Rails? I'm looking to learn Ruby on Rails. I already have a small background in Ruby and don't really need a book that covers both, as I ordered the Pickaxe Book a couple days ago. I recently read some of Beginning Ruby on Rails-Steven Holzner, but abandoned that after seeing multiple statements on SO about how terrible the code in it was, and also the fact that it used Rails 1...Just wondering, what is the best book for an ABSOLUTE BEGINNER in Rails?

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  • Learning Erlang vs learning node.js

    - by Noli
    I see a lot of crap online about how Erlang kicks node.js' ass in just about every conceivable category. So I'd like to learn Erlang, and give it a shot, but here's the problem. I'm finding that I have a much harder time picking up Erlang than I did picking up node.js. With node.js, I could pick a relatively complex project, and in a day I had something working. With Erlang, I'm running into barriers, and not going nearly as quickly. So.. for those with more experience, is Erlang complicated to learn, or am I just missing something? Node.js might not be perfect, but I seem to be able to get things done with it.

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  • REST and redirecting the response

    - by Duane Gran
    I'm developing a RESTful service. Here is a map of the current feature set: POST /api/document/file.jpg (creates the resource) GET /api/document/file.jpg (retrieves the resource) DELETE /api/document/file.jpg (removes the resource) So far, it does everything you might expect. I have a particular use case where I need to set up the browser to send a POST request using the multipart/form-data encoding for the document upload but when it is completed I want to redirect them back to the form. I know how to do a redirect, but I'm not certain about how the client and server should negotiate this behavior. Two approaches I'm considering: On the server check for the multipart/form-data encoding and, if present, redirect to the referrer when the request is complete. Add a service URI of /api/document/file.jpg/redirect to redirect to the referrer when the request is complete. I looked into setting an X header (X-myapp-redirect) but you can't tell the browser which headers to use like this. I manage the code for both the client and the server side so I'm flexible on solutions here. Is there a best practice to follow here?

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  • GRE subject Computer science

    - by Maddy.Shik
    How do I prepare for the GRE Computer Science subject test? Are there any standard text books I should follow? Agree that its under graduation level and one doesn't need to dig to deep for it. I have done my computer engineering from a college who ranks in top 20 in India. So may be my curriculum has not been that good as compared to international students. Since now i want to get admission in to world renowned university's Ph. D. program. I want to enhance my basic skills up to a level to beat other international students in competition. I want to know good book references which are recommended by professors in international school like CMU, MIT, Standford etc. Like for Algorithms Coreman is considered very good. Good books builds concepts from very basic so that one doesn't need to mug up even a basic concepts. Coreman is just too good with good blend of Mathematics and programming concepts. Definitely Test paper are must but that can be practiced once one has read text books thoroughly. Besides its been 2 years i passed out from college so its is essential for me to revise all concepts from text books. Please tell me standard text books for each subject like Computer Architecture, Database Design, Operating Systems, Discrete Maths etc.

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  • Refactoring a Single Rails Model with large methods & long join queries trying to do everything

    - by Kelseydh
    I have a working Ruby on Rails Model that I suspect is inefficient, hard to maintain, and full of unnecessary SQL join queries. I want to optimize and refactor this Model (Quiz.rb) to comply with Rails best practices, but I'm not sure how I should do it. The Rails app is a game that has Missions with many Stages. Users complete Stages by answering Questions that have correct or incorrect Answers. When a User tries to complete a stage by answering questions, the User gets a Quiz entry with many Attempts. Each Attempt records an Answer submitted for that Question within the Stage. A user completes a stage or mission by getting every Attempt correct, and their progress is tracked by adding a new entry to the UserMission & UserStage join tables. All of these features work, but unfortunately the Quiz.rb Model has been twisted to handle almost all of it exclusively. The callbacks began at 'Quiz.rb', and because I wasn't sure how to leave the Quiz Model during a multi-model update, I resorted to using Rails Console to have the @quiz instance variable via self.some_method do all the heavy lifting to retrieve every data value for the game's business logic; resulting in large extended join queries that "dance" all around the Database schema. The Quiz.rb Model that Smells: class Quiz < ActiveRecord::Base belongs_to :user has_many :attempts, dependent: :destroy before_save :check_answer before_save :update_user_mission_and_stage accepts_nested_attributes_for :attempts, :reject_if => lambda { |a| a[:answer_id].blank? }, :allow_destroy => true #Checks every answer within each quiz, adding +1 for each correct answer #within a stage quiz, and -1 for each incorrect answer def check_answer stage_score = 0 self.attempts.each do |attempt| if attempt.answer.correct? == true stage_score += 1 elsif attempt.answer.correct == false stage_score - 1 end end stage_score end def winner return true end def update_user_mission_and_stage ####### #Step 1: Checks if UserMission exists, finds or creates one. #if no UserMission for the current mission exists, creates a new UserMission if self.user_has_mission? == false @user_mission = UserMission.new(user_id: self.user.id, mission_id: self.current_stage.mission_id, available: true) @user_mission.save else @user_mission = self.find_user_mission end ####### #Step 2: Checks if current UserStage exists, stops if true to prevent duplicate entry if self.user_has_stage? @user_mission.save return true else ####### ##Step 3: if step 2 returns false: ##Initiates UserStage creation instructions #checks for winner (winner actions need to be defined) if they complete last stage of last mission for a given orientation if self.passed? && self.is_last_stage? && self.is_last_mission? create_user_stage_and_update_user_mission self.winner #NOTE: The rest are the same, but specify conditions that are available to add badges or other actions upon those conditions occurring: ##if user completes first stage of a mission elsif self.passed? && self.is_first_stage? && self.is_first_mission? create_user_stage_and_update_user_mission #creates user badge for finishing first stage of first mission self.user.add_badge(5) self.user.activity_logs.create(description: "granted first-stage badge", type_event: "badge", value: "first-stage") #If user completes last stage of a given mission, creates a new UserMission elsif self.passed? && self.is_last_stage? && self.is_first_mission? create_user_stage_and_update_user_mission #creates user badge for finishing first mission self.user.add_badge(6) self.user.activity_logs.create(description: "granted first-mission badge", type_event: "badge", value: "first-mission") elsif self.passed? create_user_stage_and_update_user_mission else self.passed? == false return true end end end #Creates a new UserStage record in the database for a successful Quiz question passing def create_user_stage_and_update_user_mission @nu_stage = @user_mission.user_stages.new(user_id: self.user.id, stage_id: self.current_stage.id) @nu_stage.save @user_mission.save self.user.add_points(50) end #Boolean that defines passing a stage as answering every question in that stage correct def passed? self.check_answer >= self.number_of_questions end #Returns the number of questions asked for that stage's quiz def number_of_questions self.attempts.first.answer.question.stage.questions.count end #Returns the current_stage for the Quiz, routing through 1st attempt in that Quiz def current_stage self.attempts.first.answer.question.stage end #Gives back the position of the stage relative to its mission. def stage_position self.attempts.first.answer.question.stage.position end #will find the user_mission for the current user and stage if it exists def find_user_mission self.user.user_missions.find_by_mission_id(self.current_stage.mission_id) end #Returns true if quiz was for the last stage within that mission #helpful for triggering actions related to a user completing a mission def is_last_stage? self.stage_position == self.current_stage.mission.stages.last.position end #Returns true if quiz was for the first stage within that mission #helpful for triggering actions related to a user completing a mission def is_first_stage? self.stage_position == self.current_stage.mission.stages_ordered.first.position end #Returns true if current user has a UserMission for the current stage def user_has_mission? self.user.missions.ids.include?(self.current_stage.mission.id) end #Returns true if current user has a UserStage for the current stage def user_has_stage? self.user.stages.include?(self.current_stage) end #Returns true if current user is on the last mission based on position within a given orientation def is_first_mission? self.user.missions.first.orientation.missions.by_position.first.position == self.current_stage.mission.position end #Returns true if current user is on the first stage & mission of a given orientation def is_last_mission? self.user.missions.first.orientation.missions.by_position.last.position == self.current_stage.mission.position end end My Question Currently my Rails server takes roughly 500ms to 1 sec to process single @quiz.save action. I am confident that the slowness here is due to sloppy code, not bad Database ERD design. What does a better solution look like? And specifically: Should I use join queries to retrieve values like I did here, or is it better to instantiate new objects within the model instead? Or am I missing a better solution? How should update_user_mission_and_stage be refactored to follow best practices? Relevant Code for Reference: quizzes_controller.rb w/ Controller Route Initiating Callback: class QuizzesController < ApplicationController before_action :find_stage_and_mission before_action :find_orientation before_action :find_question def show end def create @user = current_user @quiz = current_user.quizzes.new(quiz_params) if @quiz.save if @quiz.passed? if @mission.next_mission.nil? && @stage.next_stage.nil? redirect_to root_path, notice: "Congratulations, you have finished the last mission!" elsif @stage.next_stage.nil? redirect_to [@mission.next_mission, @mission.first_stage], notice: "Correct! Time for Mission #{@mission.next_mission.position}", info: "Starting next mission" else redirect_to [@mission, @stage.next_stage], notice: "Answer Correct! You passed the stage!" end else redirect_to [@mission, @stage], alert: "You didn't get every question right, please try again." end else redirect_to [@mission, @stage], alert: "Sorry. We were unable to save your answer. Please contact the admministrator." end @questions = @stage.questions.all end private def find_stage_and_mission @stage = Stage.find(params[:stage_id]) @mission = @stage.mission end def find_question @question = @stage.questions.find_by_id params[:id] end def quiz_params params.require(:quiz).permit(:user_id, :attempt_id, {attempts_attributes: [:id, :quiz_id, :answer_id]}) end def find_orientation @orientation = @mission.orientation @missions = @orientation.missions.by_position end end Overview of Relevant ERD Database Relationships: Mission - Stage - Question - Answer - Attempt <- Quiz <- User Mission - UserMission <- User Stage - UserStage <- User Other Models: Mission.rb class Mission < ActiveRecord::Base belongs_to :orientation has_many :stages has_many :user_missions, dependent: :destroy has_many :users, through: :user_missions #SCOPES scope :by_position, -> {order(position: :asc)} def stages_ordered stages.order(:position) end def next_mission self.orientation.missions.find_by_position(self.position.next) end def first_stage next_mission.stages_ordered.first end end Stage.rb: class Stage < ActiveRecord::Base belongs_to :mission has_many :questions, dependent: :destroy has_many :user_stages, dependent: :destroy has_many :users, through: :user_stages accepts_nested_attributes_for :questions, reject_if: :all_blank, allow_destroy: true def next_stage self.mission.stages.find_by_position(self.position.next) end end Question.rb class Question < ActiveRecord::Base belongs_to :stage has_many :answers, dependent: :destroy accepts_nested_attributes_for :answers, :reject_if => lambda { |a| a[:body].blank? }, :allow_destroy => true end Answer.rb: class Answer < ActiveRecord::Base belongs_to :question has_many :attempts, dependent: :destroy end Attempt.rb: class Attempt < ActiveRecord::Base belongs_to :answer belongs_to :quiz end User.rb: class User < ActiveRecord::Base belongs_to :school has_many :activity_logs has_many :user_missions, dependent: :destroy has_many :missions, through: :user_missions has_many :user_stages, dependent: :destroy has_many :stages, through: :user_stages has_many :orientations, through: :school has_many :quizzes, dependent: :destroy has_many :attempts, through: :quizzes def latest_stage_position self.user_missions.last.user_stages.last.stage.position end end UserMission.rb class UserMission < ActiveRecord::Base belongs_to :user belongs_to :mission has_many :user_stages, dependent: :destroy end UserStage.rb class UserStage < ActiveRecord::Base belongs_to :user belongs_to :stage belongs_to :user_mission end

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  • C# books for the experienced programmer

    - by Michael Dmitry Azarkevich
    So I've been programming in C# for 3 years now (been programming in various languages for 3 years before that as well) and most of the stuff I learned I pieced together on the internet. The thing is, I want to understand C# more formally and in depth and so would like to get some books on the subjects. Any books you'd recommend? Also, I've heard good things about "C# 4.0 in a Nutshell", "Pro C# 2010 and the .NET 4 Platform" and "CLR via C#". What do you think of these? (The people at stackoverflow told me to take it here. Please, Please tell me I'm in the right place this time)

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  • RMS java web framework

    - by Kamil Tomšík
    We're currently reconsidering technologies and frameworks to get more agile with "simple" RMS CRUD-based projects. In short, short-living things like this Right now we have custom extension on top of SmartGWT but after some time it has proven not to be enough flexible. I also personally dislike that java-js compilation process and the whole GWT codebase. Not only its ugly designed, it also makes certain low-level js things very complicated if not completely impossible. So what I'm looking for is: closest to web as possible, like JSF or possibly Tapestry, it is very important to be able get "low" and weave framework if necessary. Happens more often than we thought. datagrid capable - Ext.js & PrimeFaces looks pretty good, Vaadin does too. db-schema generators (optional, no matter in which way) If it were only on me, I'd probably stick to Ext.js + custom rest-based java solution, possibly generated from database schema (not sure about concrete tooling yet) I only does have experience with vanilla Ext.js, vanilla GWT and JSF 2.0 / Seam, so it kinda hard for me to judge or even propose other frameworks. What would be your proposition? What are the problems you've faced, what was your solution and how hard do you think it was to deal with them in "big picture"?

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  • How to include an apache library with my opensource code?

    - by OscarRyz
    I have this opensource code with MIT license that uses an Apache 2.0 licensed library. I want to include this in my project, so it can be built right away. In the point 4 of that license explains how to redistribute it: excerpt: 4 . Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions: You must give any other recipients of the Work or Derivative Works a copy of this License; and You must cause any modified files to carry prominent notices stating that You changed the files; and You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding those notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License. You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License. I'm not creating a derivative work ( I plan to provide it as it is ). I don't have a NOTICE file, just my my own LICENSE.txt file. Question: Where should I put something along the lines: "This project uses Xyz library distributed under Apache2.0 ..."? What's recommented? Should I provide the apache license file too? Or would be enough if I just say "Find the license online here...http://www.apache.org/licenses/LICENSE-2.0.html" I hope someone who has done this in the past may shed some light on the matter.

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  • What's the better user experience: Waiting once at startup for a long time or waiting frequently for a short time?

    - by Roflcoptr
    I'm currently design an application that involves a lot of calculation. Now I have generally two possibilities which I have both tested: 1) During startup of the application I calculated only the most important values and these values that consume a lot of time. So the user has to wait approximately 15 seconds during startup. But on the other hand a lot of user interactions require recalculation so that the user often has to wait 2-3 seconds after clicking somewhere until the application has calculated and loaded all values 2) I load everything during startup. This takes from 90 to 120 seconds... This is quite a long time, but the big advantage is that all the user interactions are executed immediately. So what would you generally consider the better approach? Loading all time-consuming operations during startup or when needed?

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  • Best way for a technical manager to stay up to date on technology

    - by JoelFan
    My manager asked for a list of technical blogs he should follow to stay current on technology. His problem is he keeps hearing terms that he hasn't heard of (i.e. NoSql, sharding, agure, sevice bus, etc.) and he would prefer to at least have a fighting chance of knowing something about them without having to be reactive and looking them up. Also I think he wants to have a big picture of all the emerging technologies and where they fit in together instead of just learning about each thing in isolation. He asked about blogs but I'm thinking print magazines may also help. What should I answer him?

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  • Architecture guidelines for a "single page web-app"

    - by Matt Roberts
    I'm going to start a side project to build a "single page" web application. The application needs to be real-time, sending updates to the clients as changes happen. Are there any good resources for best-practice approaches wrt the architecture for these kinds of applications. The best resource I've found so far is the trello architecture article here: http://blog.fogcreek.com/the-trello-tech-stack/ To me, this architecture, although very sexy, is probably over-engineered for my specific needs - although I do have similar requirements. I'm wondering if I need to bother with a sub/pub at the server side, could I not just push updates from the server when something happens (e.g. when the client sends an update to the server, write the update to the db, and then send an update to the clients). Tech-wise, I'm probably looking to build this out in Node.JS or maybe Ruby, although the architecture guidelines should to some extent apply to any underlying server technologies.

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  • How often to authenticate iOS app in web service

    - by jeraldov
    I am trying to build an iOS app that connects to a PHP+MySQL web service. My question is how often should I check for user's authentication to get data from the web service. My app requires a login at start up, but I am wondering if how often should I check if he can still validly get data from the web service. Should I check for his username and password each time the user views a table view that get its data from the web service?

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  • Documentation often ommits to specify which flavour of regular expression to use, so is there a default flavour that we should all be familiar with?

    - by JW01
    Often I come across documentation that says "use a regular expression here" I have to spend quite some time digging around trying to work out which regular expression format they are expecting. As far as I can tell, there are many types of regular expression. But, at my last place of work I was made to feel stupid when I suggested adding some text to our User Documentation to specify the type of regular expression to be used. When someone says "a regular expression" what is the regular expression syntax most people expect and where is it documented? Update: I was prompted to single-out some examples - but no disrespect to these great projects: eregi docs page is not particularly helpful in explaining expected syntax. Nor can I easily work out the syntax expected here if i just land on the page from a search. No explicit mention of the regular expression pattern expected by PatternExpectation() on the SimpleTest page. etc. etc. here is a highly voted SO answer that seems to assume there is only one flavour of regular expressions.

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  • Cross-Platform Google Chrome App Installer

    - by Volomike
    I have fallen in love with the Google Chrome App way of making an "app" (and extensions as well). What kind of installer would you recommend (free and/or cheap is preferred) that is cross-platform (Mac, Windows 2000+, Linux (Ubuntu, Debian, Suse, Redhat, or derivatives)) and lets me deploy Google Chrome Apps on workstations? It would need to let me deploy Google Chrome, or update Google Chrome to a particular version, as necessary, in order for my app to work.

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  • Developing Web Portal

    - by Ya Basha
    I'm php, Ruby on Rails and HTML5 developer I need some advises and suggestions for a web portal project that I will build from scratch. This is my first time to build a web portal, Which developing scripting language you prefer and why? and how I should start planing my project as it will contains many modules. I'm excited to start building this project and I want to build it in the right way with planing, if you know some web resources that help me decide and plan my project please give them to me. Best Regards,

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  • Why there is perception that VB.NET is good for small to medium size application and not for enterprise class project?

    - by Gens
    I love VB.NET very much. Coding VB.NET with Visual Studio is just like typing messages. Smooth, fast and simple. Any error will be notified instantly. The OO capability of VB.NET is good enough. But often in any .Net languages discussion, there is perception that VB.NET is good for small to medium size application and not for large scale project? Why there is such perception? Or am I missing anything regarding to VB.NET?

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  • How to store Role Based Access rights in web application?

    - by JonH
    Currently working on a web based CRM type system that deals with various Modules such as Companies, Contacts, Projects, Sub Projects, etc. A typical CRM type system (asp.net web form, C#, SQL Server backend). We plan to implement role based security so that basically a user can have one or more roles. Roles would be broken down by first the module type such as: -Company -Contact And then by the actions for that module for instance each module would end up with a table such as this: Role1 Example: Module Create Edit Delete View Company Yes Owner Only No Yes Contact Yes Yes Yes Yes In the above case Role1 has two module types (Company, and Contact). For company, the person assigned to this role can create companies, can view companies, can only edit records he/she created and cannot delete. For this same role for the module contact this user can create contacts, edit contacts, delete contacts, and view contacts (full rights basically). I am wondering is it best upon coming into the system to session the user's role with something like a: List<Role> roles; Where the Role class would have some sort of List<Module> modules; (can contain Company, Contact, etc.).? Something to the effect of: class Role{ string name; string desc; List<Module> modules; } And the module action class would have a set of actions (Create, Edit, Delete, etc.) for each module: class ModuleActions{ List<Action> actions; } And the action has a value of whether the user can perform the right: class Action{ string right; } Just a rough idea, I know the action could be an enum and the ModuleAction can probably be eliminated with a List<x, y>. My main question is what would be the best way to store this information in this type of application: Should I store it in the User Session state (I have a session class where I manage things related to the user). I generally load this during the initial loading of the application (global.asax). I can simply tack onto this session. Or should this be loaded at the page load event of each module (page load of company etc..). I eventually need to be able to hide / unhide various buttons / divs based on the user's role and that is what got me thinking to load this via session. Any examples or points would be great.

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  • Is it legal and ethical to reverse engineer software to port it to another system?

    - by Igor Zinov'yev
    I love gaming, I love games that allow modding and I love linux. But the fact that most games right now are targeted for windows (consoles aside), most mods and modding tools are also targeted for windows. There is a certain modder called Boris Vorontsov that makes a famous visual overhaul mod series called ENB. What he does (or I think he does) is he enhances or changes the behavior of classes defined in the d3d9.dll library. Needless to say it almost never works under wine. Recently I have asked him if he would ever release his version of the library under some open license, and he said "no". Now that I think of it, even if he did release his code, he would have surely faced some legal problems. Now there is my question. Is it legal and ethical to reverse engineer his version of the library to adapt the wine's open source version of d3d9.dll to be able to run his mods?

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  • Should each app have its own database, or should small apps be merged into one?

    - by King
    We have a bunch of small to medium sized apps, each of which has its own database (MSSQL Server). There was a suggestion that we consoldate the 'related' databases into a smaller set amount of larger databases. They don't particularly share a lot of data, they would just be under a similar business group. For example, using a 'Finance' DB to hold the tables and procedures for finance apps. Would it be appropriate to use a different schema for each app? E.g. App1.SomeTable App1.SomeOtherTable AppTwo.SomeTable What are the pros and cons of this approach? What should I watch out for? Thanks

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  • How to store generated eigen faces for future face recognition?

    - by user3237134
    My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong? 2.Instead of running the training set everytime how eigen faces generated are stored so that stored eigen faces are used for future face recoginition for a new input image.So it reduces wastage of time.

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  • single for-loop runtime explanation problem

    - by owwyess
    I am analyzing some running times of different for-loops, and as I'm getting more knowledge, I'm curious to understand this problem which I have still yet to find out. I have this exercise called "How many stars are printed": for (int i = N; i > 1; i = i/2) System.out.println("*"); The answers to pick from is A: ~log N B: ~N C: ~N log N D: ~0.5N^2 So the answer should be A and I agree to that, but on the other side.. Let's say N = 500 what would Log N then be? It would be 2.7. So what if we say that N=500 on our exercise above? That would most definitely print more han 2.7 stars? How is that related? Because it makes sense to say that if the for-loop looked like this: for (int i = 0; i < N; i++) it would print N stars. I hope to find an explanation for this here, maybe I'm interpreting all these things wrong and thinking about it in a bad way. Thanks in advance.

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  • Keeping an enum and a table in sync

    - by MPelletier
    I'm making a program that will post data to a database, and I've run into a pattern that I'm sure is familiar: A short table of most-likely (very strongly likely) fixed values that serve as an enum. So suppose the following table called Status: Status Id Description -------------- 0 Unprocessed 1 Pending 2 Processed 3 Error In my program I need to determine a status Id for another table, or possibly update a record with a new status Id. I could hardcode the status Id's in an enum and hope no one ever changes the database. Or I could pre-fetch the values based on the description (thus hardcoding that instead). What would be the correct approach to keep these two, enum and table, synced?

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  • How to Properly Make use of Codeigniter's HMVC

    - by Branden Stilgar Sueper
    I have been having problems wrapping my brain around how to properly utilize the modular extension for Codeigniter. From what I understand, modules should be entirely independent of one another so I can work on one module and not have to worry about what module my teammate is working on. I am building a frontend and a backend to my site, and am having confusion about how I should structure my applications. The first part of my question is should I use the app root controllers to run modules, or should users go directly to the modules by urls? IE: in my welcome.php public function index() { $this->data['blog'] = Modules::run( 'blog' ); $this->data['main'] = Modules::run( 'random_image' ); $this->load->view('v_template', $this->data); } public function calendar() { $this->data['blog'] = Modules::run( 'blog' ); $this->data['main'] = Modules::run( 'calendar' ); $this->load->view('v_template', $this->data); } My second part of the question is should I create separate front/back end module folders -config -controllers welcome.php -admin admin.php -core -helpers -hooks -language -libraries -models -modules-back -dashboard -logged_in -login -register -upload_images -delete_images -modules-front -blog -calendar -random_image -search -views v_template.php -admin av_template.php Any help would be greatly appreciated.

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  • How do I let customers run arbitrary code as securely as possible?

    - by Tyler
    I'd like to offer a service where customers can write arbitrary java code, send it to me, and I'll run it for them on Amazon EC2. My question is: how can I do this without exposing one customer's data to another customer? Right now I'm thinking that each customer can be sandboxed as their own OS-level user with restricted permissions. Is that good enough? I understand that this is a tricky issue, but it seems to be one that many people, such as the designers of multi-user OS's and Amazon themselves are solving, so I am optimistic that there might be a good approach.

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  • What are some arguments AGAINST using EntityFramework?

    - by Rachel
    The application I am currently building has been using Stored procedures and hand-crafted class models to represent database objects. Some people have suggested using Entity Framework and I am considering switching to that since I am not that far into the project. My problem is, I feel the people arguing for EF are only telling me the good side of things, not the bad side :) My main concerns are: We want Client-Side validation using DataAnnotations, and it sounds like I have to create the client-side models anyways so I am not sure that EF would save that much coding time We would like to keep the classes as small as possible when going over the network, and I have read that using EF often includes extra data that is not needed We have a complex database layer which crosses multiple databases, and I am not sure EF can handle this. We have one Common database with things like Users, StatusCodes, Types, etc and multiple instances of our main databases for different instances of the application. SELECT queries can and will query across all instances of the databases, however users can only modify objects that are in the database they are currently working on. They can switch databases without reloading the application. Object modes are very complex and there are often quite a few joins involved Arguments for EF are: Concurrency. I wouldn't have to code in checks to see if the record was updated before each save Code Generation. EF can generate partial class models and POCOs for me, however I am not positive this would really save me that much time since I think we would still need to create the client-side models for validation and some custom parsing methods. Speed of development since we wouldn't need to create the CRUD stored procedures for every database object Our current architecture consists of a WPF Service which handles database calls via parameterized Stored Procedures, POCO objects that go to/from the WCF service and the WPF client, and the WPF client itself which transforms POCOs into class Models for the purpose of Validation and DataBinding.

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