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  • Error when pushing to Heroku - ...appear in group - Ruby on Rails

    - by bgadoci
    I am trying to deploy my first rails app to Heroku and seem to be having a problem. After git push heroku master, and heroku rake db:migrate I get an error saying: SELECT posts.*, count(*) as vote_total FROM "posts" INNER JOIN "votes" ON votes.post_id = posts.id GROUP BY votes.post_id ORDER BY created_at DESC LIMIT 5 OFFSET 0): I have included the full error below and also included the PostControll#index as it seems that is where I am doing the grouping. Lastly I included my routes.rb file. I am new to ruby, rails, and heroku so sorry for simple/obvious questions. Processing PostsController#index (for 99.7.50.140 at 2010-04-21 12:50:47) [GET] ActiveRecord::StatementInvalid (PGError: ERROR: column "posts.id" must appear in the GROUP BY clause or be used in an aggregate function : SELECT posts.*, count(*) as vote_total FROM "posts" INNER JOIN "votes" ON votes.post_id = posts.id GROUP BY votes.post_id ORDER BY created_at DESC LIMIT 5 OFFSET 0): vendor/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:82:in `send' vendor/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:82:in `paginate' vendor/gems/will_paginate-2.3.12/lib/will_paginate/collection.rb:87:in `create' vendor/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:76:in `paginate' app/controllers/posts_controller.rb:28:in `index' /home/heroku_rack/lib/static_assets.rb:9:in `call' /home/heroku_rack/lib/last_access.rb:25:in `call' /home/heroku_rack/lib/date_header.rb:14:in `call' thin (1.0.1) lib/thin/connection.rb:80:in `pre_process' thin (1.0.1) lib/thin/connection.rb:78:in `catch' thin (1.0.1) lib/thin/connection.rb:78:in `pre_process' thin (1.0.1) lib/thin/connection.rb:57:in `process' thin (1.0.1) lib/thin/connection.rb:42:in `receive_data' eventmachine (0.12.6) lib/eventmachine.rb:240:in `run_machine' eventmachine (0.12.6) lib/eventmachine.rb:240:in `run' thin (1.0.1) lib/thin/backends/base.rb:57:in `start' thin (1.0.1) lib/thin/server.rb:150:in `start' thin (1.0.1) lib/thin/controllers/controller.rb:80:in `start' thin (1.0.1) lib/thin/runner.rb:173:in `send' thin (1.0.1) lib/thin/runner.rb:173:in `run_command' thin (1.0.1) lib/thin/runner.rb:139:in `run!' thin (1.0.1) bin/thin:6 /usr/local/bin/thin:20:in `load' /usr/local/bin/thin:20 PostsController def index @tag_counts = Tag.count(:group => :tag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @ugtag_counts = Ugtag.count(:group => :ugctag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @vote_counts = Vote.count(:group => :post_title, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes unless(params[:tag_name] || "").empty? conditions = ["tags.tag_name = ? ", params[:tag_name]] joins = [:tags, :votes] end @posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id", :order => "created_at DESC", :page => params[:page], :per_page => 5) @popular_posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id", :order => "vote_total DESC", :page => params[:page], :per_page => 3) respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } format.json { render :json => @posts } format.atom end end routes.rb ActionController::Routing::Routes.draw do |map| map.resources :ugtags map.resources :wysihat_files map.resources :users map.resources :votes map.resources :votes, :belongs_to => :user map.resources :tags, :belongs_to => :user map.resources :ugtags, :belongs_to => :user map.resources :posts, :collection => {:auto_complete_for_tag_tag_name => :get } map.resources :posts, :sessions map.resources :posts, :has_many => :comments map.resources :posts, :has_many => :tags map.resources :posts, :has_many => :ugtags map.resources :posts, :has_many => :votes map.resources :posts, :belongs_to => :user map.resources :tags, :collection => {:auto_complete_for_tag_tag_name => :get } map.resources :ugtags, :collection => {:auto_complete_for_ugtag_ugctag_name => :get } map.login 'login', :controller => 'sessions', :action => 'new' map.logout 'logout', :controller => 'sessions', :action => 'destroy' map.root :controller => "posts" map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format' end UPDATE TO SHOW MODEL AND MIGRATION FOR POST class Post < ActiveRecord::Base has_attached_file :photo validates_presence_of :body, :title has_many :comments, :dependent => :destroy has_many :tags, :dependent => :destroy has_many :ugtags, :dependent => :destroy has_many :votes, :dependent => :destroy belongs_to :user after_create :self_vote def self_vote # I am assuming you have a user_id field in `posts` and `votes` table. self.votes.create(:user => self.user) end cattr_reader :per_page @@per_page = 10 end migrations for post class CreatePosts < ActiveRecord::Migration def self.up create_table :posts do |t| t.string :title t.text :body t.timestamps end end def self.down drop_table :posts end end _ class AddUserIdToPost < ActiveRecord::Migration def self.up add_column :posts, :user_id, :string end def self.down remove_column :posts, :user_id end end

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  • Unable to access value of nested array element

    - by John Conde
    I'm having an issue getting the value of a nested array element. Here's what I've got: print_r($environment); // Outputs Array ( [0] => Array ( ['parameter'] => Vibration ['conditions'] => 204 ['method'] => D ) [1] => Array ( ['parameter'] => Immersion ['conditions'] => 104 ['method'] => B ) [2] => Array ( ['parameter'] => Shock ['conditions'] => 213 ['method'] => I ) [3] => Array ( ['parameter'] => Humidity ['conditions'] => 106 ['method'] => - ) ) print_r($environment[0]); // Outputs Array ( ['parameter'] => Vibration ['conditions'] => 204 ['method'] => D ) echo $environment[0]['parameter']; // Nothing Maybe I've been looking at this for too long. Any ideas would be greatly appreciated.

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  • select SUM in Cake

    - by SpawnCxy
    When I tried using follow code to get the sum of the column named Serviceinfo.services $conditions = array('fields'=>array('SUM(Serviceinfo.services) as servicecount'),'conditions'=>array('time_id BETWEEN ? AND ?'=>array($startid,$endtid))); $services = $this->Serviceinfo->find('all',$conditions); I had to fetch the sum data with services[0][0]['servicecount'] which seems a little weird.And What I expect is services['Serviceinfo']['servicecount'],or more simple one.Then how can I fix this?Thanks in advance!

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  • cakephp paginate multiple habtm

    - by izmanromli
    hi guys, i have multiple habtm like these : // User model var $hasMany = array('Post'); // Post model var $hasAndBelongsToMany = array('Category', 'Tag'); // Category model var $hasAndBelongsToMany = array('Post'); // Tag model var $hasAndBelongsToMany = array('Post'); I tried to fetch all post along with its user and tags (within a certain category), somehow if i fetch tags, the result was wrong. $this->paginate = array ( 'Post' => array ( 'limit' => 2, 'fields' => array( 'Post.title', 'Post.content', 'Post.slug', 'Post.created', 'Tag.name', 'User.username', 'User.created', 'User.post_count', 'User.avatar_file_name'), 'joins' => array ( array( 'table' => 'categories_posts', 'alias' => 'CategoriesPost', 'type' => 'inner', 'conditions'=> array('CategoriesPost.post_id = Post.id') ), // FETCH USER array( 'table' => 'users', 'alias' => 'User', 'type' => 'inner', 'conditions'=> array('Post.user_id = User.id') ), // FETCH TAGS array( 'table' => 'posts_tags', 'alias' => 'PostsTag', 'type' => 'inner', 'conditions'=> array('PostsTag.post_id = Post.id') ), array( 'table' => 'tags', 'alias' => 'Tag', 'type' => 'inner', 'conditions'=> array('Tag.id = PostsTag.tag_id') ), array( 'table' => 'categories', 'alias' => 'Category', 'type' => 'inner', 'conditions'=> array('Category.id = CategoriesPost.category_id', 'Category.slug' => $slug) ) ) ) ); $posts = $this->paginate(); could anyone gimme a solution since i'm a newbie? many thanks...

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  • UI Design, incase of numerous situations

    - by The King
    Hi... I'm creating a web form, where in there are around 12-15 Input Fields... You can have a look at the screen and The request is such that depending on the data the user selects in the Gridview and the DropDown list, the appropriate Textboxes and CheckBoxes needs to be displayed. Some times the conditions are very direct, like when the DDL value is "ABC", get only paid amount from the user. Sometime they are so complex like... IF DDL is "DEF" and Selected GPMS value is between 1000-2000, calculate the values of allowed, paid etc (using some formula) and the focus should be directed to Page No Field, leaving the other fields open incase user wants to edit... There are around 10-15 conditions like this. As this was done through agile, conditions were being added as and when, and wherever it feels appropriate (DDL on change Event, GridView on selecting change event etc... etc..) After completion, now I see the code has become a big chuck, is growing unmanageably... Now, I'm planning to clear this... From you experience, what you think is the best way to handle this. There is a possibility to add more conditions like this in future... Please let me know, incase you need more information. I'm currently developing this app in C# .Net WindowsForms Edit: Currently there are only three items (The Datagrid, the DDL, the OverrideAmt CheckBox) that change the way other fields behave... Almost all of the conditions will fall between the two situations I mentioned... Mostly they belong to "Enabling/Disabling".. "Setting of Values"... and "Changing Focus" or any combination of these.

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  • NOAA web service for current weather

    - by Brian
    I want to get the current weather conditions from the NOAA. I know they have a SOAP web service that can be used to get weather forecasts and XML files for current weather conditions for each of their weather stations. I could just use the XML file for the weather station nearest to where I want, but there doesn't seem to be an easy way to search for the proper xml file by zipcode. Is there a simple way to get current weather conditions by zipcode from the NOAA?

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  • Do I really need bindParam?

    - by sandelius
    Hi there! I'm trying to do a little PDO CRUD to learn some PDO. I have a question about bindParam. Here's my update method right now: public static function update($conditions = array(), $data = array(), $table = '') { self::instance(); // Late static bindings (PHP 5.3) $table = ($table === '') ? self::table() : $table; // Check which data array we want to use $values = (empty($data)) ? self::$_fields : $data; $sql = "UPDATE $table SET "; foreach ($values as $f => $v) { $sql .= "$f = ?, "; } // let's build the conditions self::build_conditions($conditions); // fix our WHERE, AND, OR, LIKE conditions $extra = self::$condition_string; // querystring $sql = rtrim($sql, ', ') . $extra; // let's merge the arrays into on $v_val = array_values($values); $c_val = array_values($conditions); $array = array_merge($v_val, self::$condition_array); $stmt = self::$db->prepare($sql); return $stmt->execute($array); } in my "self::$condition_array" I get all the right values from the ?. SO the query looks like this: UPDATE table SET this = ?, another = ? WHERE title = ? AND time = ? as you can see I dont use bindParams instead I pass the right values in the right order ($array) directly into the execute($array) method. This works like a charm BUT is it safe not use use bindParam here? If not then how can I do it? Thanks from Sweden Tobias

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  • Adding a computed column to an ActiveRecord query

    - by bmwbzz
    Hi, I am running a query using a scope and some conditions. Something like this: conditions[:offset] = (options[:page].to_i - 1) * PAGE_SIZE unless options[:page].blank? conditions[:limit] = options[:limit] ||= PAGE_SIZE scope = Promo.enabled.active results = scope.all conditions I'd like to add a computed column to the query (at the point when I'm now calling scope.all). Something like this: (ACOS(least(1,COS(0.71106459055501)*COS(-1.2915436464758)*COS(RADIANS(addresses.lat))*COS(RADIANS(addresses.lng))+ COS(0.71106459055501)*SIN(-1.2915436464758)*COS(RADIANS(addresses.lat))*SIN(RADIANS(addresses.lng))+ SIN(0.71106459055501)*SIN(RADIANS(addresses.lat))))*3963.19) as accurate_distance Is there a way to do that without just using find_by_sql and rewriting the whole existing query? Thanks!

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  • Do I really ned bindParam?

    - by sandelius
    Hi there! I'm trying to do a little PDO CRUD to learn some PDO. I have a question about bindParam. Here's my update method right now: public static function update($conditions = array(), $data = array(), $table = '') { self::instance(); // Late static bindings (PHP 5.3) $table = ($table === '') ? self::table() : $table; // Check which data array we want to use $values = (empty($data)) ? self::$_fields : $data; $sql = "UPDATE $table SET "; foreach ($values as $f => $v) { $sql .= "$f = ?, "; } // let's build the conditions self::build_conditions($conditions); // fix our WHERE, AND, OR, LIKE conditions $extra = self::$condition_string; // querystring $sql = rtrim($sql, ', ') . $extra; // let's merge the arrays into on $v_val = array_values($values); $c_val = array_values($conditions); $array = array_merge($v_val, self::$condition_array); $stmt = self::$db->prepare($sql); return $stmt->execute($array); } in my "self::$condition_array" I get all the right values from the ?. SO the query looks like this: UPDATE table SET this = ?, another = ? WHERE title = ? AND time = ? as you can see I dont use bindParams instead I pass the right values in the right order ($array) directly into the execute($array) method. This works like a charm BUT is it safe not use use bindParam here? If not then how can I do it? Thanks from Sweden Tobias

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  • What is the best way to do scoped finds based on access control rules in Rails?

    - by Rafael Szuminski
    Hi I need to find an elegant solution to scoped finds based on access control rules. Essentially I have the following setup: Users Customers AccessControl - Defines which user has access to another users data Users need to be able to access not just their own customers but also shared customers of other users. Obviously something like a simple association will not work: has_many :customers and neither will this: has_many :customers, :conditions => 'user_id in (1,2,3,4,5)' because the association uses with_scope and the added condition is an AND condition not an OR condition. I also tried overriding the find and method_missing methods with the association extension like this: has_many :customers do def find(*args) #get the user_id and retrieve access conditions based on the id #do a find based on the access conditions and passed args end def method_missing(*args) #get the user_id and retrieve access conditions based on the id #do a find based on the access conditions and passed args end end but the issue is that I don't have access to the user object / parent object inside the extension methods and it just does not work as planned. I also tried default_scope but as posted here before you can't pass a block to a default scope. Anyhow, I know that data segmentation and data access controls have been done before using rails and am wondering if somebody found an elegant way to do it. UPDATE: The AccessControl table has the following layout user_id shared_user_id The customer table has this structure: id account_id user_id first_name last_name Assuming the the following data would be in the AccessControl table: 1 1 1 3 1 4 2 2 2 13 and so on... And the account_id for user 1 is 13 I need to be able to retrieve customers that can be best described with the following sql statement: select * from customers where (account_id = 13 and user_id = null) or (user_id in (1,3,4))

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  • In an If-Else Statement for a method return, should an Else be explicitly stated if it can instead b

    - by ccomet
    I have a method that checks certain things and returns a Boolean based on those checks. It involves a single branching If section that checks about 5 conditions in sequence. If any of those conditions return true, then the method will return true;. If none of the conditions return true, then the method will return false;. Since the code after the If section will only run if none of the conditions are true, then that code is logically identical to including an actual Else statement. So is it a better idea to actually write in the Else statement for this kind of situation?

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  • Rails SQL injection?

    - by yuval
    In Rails, when I want to find by a user given value and avoid SQL injection (escape apostrophes and the like) I can do something like this: Post.all(:conditions => ['title = ?', params[:title]]) I know that an unsafe way of doing this (possible SQL injection) is this: Post.all(:conditions => "title = #{params[:title]}") My question is, does the following method prevent SQL injection or not? Post.all(:conditions => {:title => params[:title]})

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  • finding elements in python association lists efficiently

    - by user248237
    I have a set of lists that look like this: conditions = [ ["condition1", ["sample1", "sample2", "sample3"]], ["condition2", ["sample4", "sample5", "sample6"], ...] how can I do the following things efficiently and elegantly in Python? Find all the elements in a certain condition? e.g. get all the samples in condition2. Right now I can do: for cond in conditions: cond_name, samples = cond if cond_name == requested_cond: return samples but that's clunky. Find the ordered union of a list of conditions? E.g. ordered_union(["condition1", "condition2"], conditions) should return: ["sample1", "sample2", "sample3", "sample4", "sample5", "sample6"] How can I do this efficiently in Python? There are probably clever one liners?

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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  • Good practices - database programming, unit testing

    - by Piotr Rodak
    Jason Brimhal wrote today on his blog that new book, Defensive Database Programming , written by Alex Kuznetsov ( blog ) is coming to bookstores. Alex writes about various techniques that make your code safer to run. SQL injection is not the only one vulnerability the code may be exposed to. Some other include inconsistent search patterns, unsupported character sets, locale settings, issues that may occur during high concurrency conditions, logic that breaks when certain conditions are not met. The...(read more)

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  • Understanding and Benefiting from Code Contracts in .NET 4.0

    One of the fundamental programming challenges is managing state. Chances are you have written dozens and dozens of methods that at the beginning check that certain conditions are met, and that another set of conditions is met when the method returns. With Code Contracts in .NET 4.0, you can make things considerably easier. Read on to learn how.

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  • How do I use IIS7 rewrite to redirect requests for (HTTP or HTTPS):// (www or no-www) .domainaliases.ext to HTTPS://maindomain.ext

    - by costax
    I have multiple domain names assigned to the same site and I want all possible access combinations redirected to one domain. In other words whether the visitor uses http://domainalias.ext or http://www.domainalias.ext or https://www.domainalias3.ext or https://domainalias4.ext or any other combination, including http://maindomain.ext, http://www.maindomain.ext, and https://www.maindomain.ext they are all redirected to https://maindomain.ext I currently use the following code to partially achieve my objectives: <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <rewrite> <rules> <rule name="CanonicalHostNameRule" stopProcessing="true"> <match url="(.*)" /> <conditions> <add input="{HTTP_HOST}" pattern="^MAINDOMAIN\.EXT$" negate="true" /> </conditions> <action type="Redirect" redirectType="Permanent" url="https://MAINDOMAIN.EXT/{R:1}" /> </rule> <rule name="HTTP2HTTPS" stopProcessing="true"> <match url="(.*)" /> <conditions> <add input="{HTTPS}" pattern="off" ignoreCase="true" /> </conditions> <action type="Redirect" redirectType="Permanent" url="https://MAINDOMAIN.EXT/{R:1}" /> </rule> </rules> </rewrite> </system.webServer> </configuration> ...but it fails to work in all instances. It does not redirect to https://maindomain.ext when user inputs https://(www.)domainalias.ext So my question is, are there any programmers here familiar with IIS7 ReWrite that can help me modify my existing code to cover all possibilities and reroute all my domain aliases, loaded by themselves or using www in front, in HTTP or HTTPS mode, to my main domain in HTTPS format??? The logic would be: if entire URL does NOT start with https://maindomain.ext then REDIRECT to https://maindomain.ext/(plus_whatever_else_that_followed). Thank you very much for your attention and any help would be appreciated. NOTE TO MODS: If my question is not in the correct format, please edit or advise. Thanks in advance.

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  • historical weather data APIs

    - by AJ.
    I am building a web application where I need to display whole year's month wise weather conditions. So that users get an idea of what the weather conditions are like and plan their trips accordingly. I am using WunderGround's History feature but it does not give this data for smaller towns and destinations, even some very popular tourist destinations. Are there any alternatives which could provide me the same information.

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  • Is a 1:* write:read thread system safe?

    - by Di-0xide
    Theoretically, thread-safe code should fix race conditions. Race conditions, as I understand it, occur because two threads attempt to write to the same location at the same time. However, what about a threading model in which a single thread is designed to write to a location, and several slave/worker threads simply read from the location? Assuming the value/timing at which they read the data isn't relevant/doesn't hinder the worker thread's outcome, wouldn't this be considered 'thread safe', or am I missing something in my logic?

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  • How to hide subfolder when using Web.config for subdomains?

    - by mc-kay
    I have FTP access to my ASP.NET Websapce (IIS 7) and I route subdomains with a Web.config in the web root folder. She looks like this: <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <rewrite> <rules> <rule name="route www and emtpy requests" stopProcessing="true"> <match url=".*" /> <conditions logicalGrouping="MatchAll" trackAllCaptures="false"> <add input="{HTTP_HOST}" pattern="^(www.)?example.com" /> <add input="{PATH_INFO}" pattern="^/www/" negate="true" /> </conditions> <action type="Rewrite" url="\www\{R:0}" /> </rule> <rule name="route to blog" stopProcessing="true"> <match url=".*" /> <conditions logicalGrouping="MatchAll" trackAllCaptures="false"> <add input="{HTTP_HOST}" pattern="^blog.example.com$" /> <add input="{PATH_INFO}" pattern="^/blog/" negate="true" /> </conditions> <action type="Rewrite" url="\blog\{R:0}" /> </rule> </rules> </rewrite> </system.webServer> </configuration> As you can see i have two folders in my root directory: "www" and "blog". When i now enter "blog.example.com" everythink is working fine, but when i click a link i will go to "blog.example.com/blog" What can I do to prevent this behavior ?

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  • Remove directory from URL IIS 7.5

    - by xalx
    I've tried to find a solution to this and found some guides out there but none seem to work. I have the following URL - http://www.mysite.com/aboutus.html However there are some other sites which link to my old hosted site and point to http://www.mysite.com/nw/aboutus.html. My issue here is trying to remove the 'nw' directory from the URL's. I have setup the following URL Rewrite in IIS but it does not seem to do anything, <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <rewrite> <rules> <rule name="Redirect all to root folder" enabled="true" stopProcessing="true"> <match url="^nw$|^/nw/(.*)$" /> <conditions> </conditions> <action type="Redirect" url="nw/{R:1}" /> </rule> <rule name="RewriteToFile"> <match url="^(?!nw/)(.*)" /> <conditions> <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" /> <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" /> </conditions> <action type="Rewrite" url="/{R:1}" /> </rule> </rules> </rewrite> </system.webServer> </configuration> Any insight would be appreciated.

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  • current_user and Comments on Posts - Create another association or loop posts? - Ruby on Rails

    - by bgadoci
    I have created a blog application using Ruby on Rails and have just added an authentication piece and it is working nicely. I am now trying to go back through my application to adjust the code such that it only shows information that is associated with a certain user. Currently, Users has_many :posts and Posts has_many :comments. When a post is created I am successfully inserting the user_id into the post table. Additionally I am successfully only displaying the posts that belong to a certain user upon their login in the /views/posts/index.html.erb view. My problem is with the comments. For instance on the home page, when logged in, a user will see only posts that they have written, but comments from all users on all posts. Which is not what I want and need some direction in correcting. I want only to display the comments written on all of the logged in users posts. Do I need to create associations such that comments also belong to user? Or is there a way to adjust my code to simply loop through post to display this data. I have put the code for the PostsController, CommentsController, and /posts/index.html.erb below and also my view code but will post more if needed. class PostsController < ApplicationController before_filter :authenticate auto_complete_for :tag, :tag_name auto_complete_for :ugtag, :ugctag_name def index @tag_counts = Tag.count(:group => :tag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @ugtag_counts = Ugtag.count(:group => :ugctag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @vote_counts = Vote.count(:group => :post_title, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes unless(params[:tag_name] || "").empty? conditions = ["tags.tag_name = ? ", params[:tag_name]] joins = [:tags, :votes] end @posts= current_user.posts.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id, posts.id ", :order => "created_at DESC", :page => params[:page], :per_page => 5) @popular_posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id, posts.id", :order => "vote_total DESC", :page => params[:page], :per_page => 3) respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } format.json { render :json => @posts } format.atom end end def show @post = Post.find(params[:id]) respond_to do |format| format.html # show.html.erb format.xml { render :xml => @post } end end def new @post = Post.new respond_to do |format| format.html # new.html.erb format.xml { render :xml => @post } end end def edit @post = Post.find(params[:id]) end def create @post = current_user.posts.create(params[:post]) respond_to do |format| if @post.save flash[:notice] = 'Post was successfully created.' format.html { redirect_to(@post) } format.xml { render :xml => @post, :status => :created, :location => @post } else format.html { render :action => "new" } format.xml { render :xml => @post.errors, :status => :unprocessable_entity } end end end def update @post = Post.find(params[:id]) respond_to do |format| if @post.update_attributes(params[:post]) flash[:notice] = 'Post was successfully updated.' format.html { redirect_to(@post) } format.xml { head :ok } else format.html { render :action => "edit" } format.xml { render :xml => @post.errors, :status => :unprocessable_entity } end end end def destroy @post = Post.find(params[:id]) @post.destroy respond_to do |format| format.html { redirect_to(posts_url) } format.xml { head :ok } end end end CommentsController class CommentsController < ApplicationController before_filter :authenticate, :except => [:show, :create] def index @comments = Comment.find(:all, :include => :post, :order => "created_at DESC").paginate :page => params[:page], :per_page => 5 respond_to do |format| format.html # index.html.erb format.xml { render :xml => @comments } format.json { render :json => @comments } format.atom end end def show @comment = Comment.find(params[:id]) respond_to do |format| format.html # show.html.erb format.xml { render :xml => @comment } end end # GET /posts/new # GET /posts/new.xml # GET /posts/1/edit def edit @comment = Comment.find(params[:id]) end def update @comment = Comment.find(params[:id]) respond_to do |format| if @comment.update_attributes(params[:comment]) flash[:notice] = 'Comment was successfully updated.' format.html { redirect_to(@comment) } format.xml { head :ok } else format.html { render :action => "edit" } format.xml { render :xml => @comment.errors, :status => :unprocessable_entity } end end end def create @post = Post.find(params[:post_id]) @comment = @post.comments.build(params[:comment]) respond_to do |format| if @comment.save flash[:notice] = "Thanks for adding this comment" format.html { redirect_to @post } format.js else flash[:notice] = "Make sure you include your name and a valid email address" format.html { redirect_to @post } end end end def destroy @comment = Comment.find(params[:id]) @comment.destroy respond_to do |format| format.html { redirect_to Post.find(params[:post_id]) } format.js end end end View Code for Comments <% Comment.find(:all, :order => 'created_at DESC', :limit => 3).each do |comment| -%> <div id="side-bar-comments"> <p> <div class="small"><%=h comment.name %> commented on:</div> <div class="dark-grey"><%= link_to h(comment.post.title), comment.post %><br/></div> <i><%=h truncate(comment.body, :length => 100) %></i><br/> <div class="small"><i> <%= time_ago_in_words(comment.created_at) %> ago</i></div> </p> </div> <% end -%>

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  • Weblogic 10.0: SAMLSignedObject.verify() failed to validate signature value

    - by joshea
    I've been having this problem for a while and it's driving me nuts. I'm trying to create a client (in C# .NET 2.0) that will use SAML 1.1 to sign on to a WebLogic 10.0 server (i.e., a Single Sign-On scenario, using browser/post profile). The client is on a WinXP machine and the WebLogic server is on a RHEL 5 box. I based my client largely on code in the example here: http://www.codeproject.com/KB/aspnet/DotNetSamlPost.aspx (the source has a section for SAML 1.1). I set up WebLogic based on instructions for SAML Destination Site from here:http://www.oracle.com/technology/pub/articles/dev2arch/2006/12/sso-with-saml4.html I created a certificate using makecert that came with VS 2005. makecert -r -pe -n "CN=whatever" -b 01/01/2010 -e 01/01/2011 -sky exchange whatever.cer -sv whatever.pvk pvk2pfx.exe -pvk whatever.pvk -spc whatever.cer -pfx whatever.pfx Then I installed the .pfx to my personal certificate directory, and installed the .cer into the WebLogic SAML Identity Asserter V2. I read on another site that formatting the response to be readable (ie, adding whitespace) to the response after signing would cause this problem, so I tried various combinations of turning on/off .Indent XMLWriterSettings and turning on/off .PreserveWhiteSpace when loading the XML document, and none of it made any difference. I've printed the SignatureValue both before the message is is encoded/sent and after it arrives/gets decoded, and they are the same. So, to be clear: the Response appears to be formed, encoded, sent, and decoded fine (I see the full Response in the WebLogic logs). WebLogic finds the certificate I want it to use, verifies that a key was supplied, gets the signed info, and then fails to validate the signature. Code: public string createResponse(Dictionary<string, string> attributes){ ResponseType response = new ResponseType(); // Create Response response.ResponseID = "_" + Guid.NewGuid().ToString(); response.MajorVersion = "1"; response.MinorVersion = "1"; response.IssueInstant = System.DateTime.UtcNow; response.Recipient = "http://theWLServer/samlacs/acs"; StatusType status = new StatusType(); status.StatusCode = new StatusCodeType(); status.StatusCode.Value = new XmlQualifiedName("Success", "urn:oasis:names:tc:SAML:1.0:protocol"); response.Status = status; // Create Assertion AssertionType assertionType = CreateSaml11Assertion(attributes); response.Assertion = new AssertionType[] {assertionType}; //Serialize XmlSerializerNamespaces ns = new XmlSerializerNamespaces(); ns.Add("samlp", "urn:oasis:names:tc:SAML:1.0:protocol"); ns.Add("saml", "urn:oasis:names:tc:SAML:1.0:assertion"); XmlSerializer responseSerializer = new XmlSerializer(response.GetType()); StringWriter stringWriter = new StringWriter(); XmlWriterSettings settings = new XmlWriterSettings(); settings.OmitXmlDeclaration = true; settings.Indent = false;//I've tried both ways, for the fun of it settings.Encoding = Encoding.UTF8; XmlWriter responseWriter = XmlTextWriter.Create(stringWriter, settings); responseSerializer.Serialize(responseWriter, response, ns); responseWriter.Close(); string samlString = stringWriter.ToString(); stringWriter.Close(); // Sign the document XmlDocument doc = new XmlDocument(); doc.PreserveWhiteSpace = true; //also tried this both ways to no avail doc.LoadXml(samlString); X509Certificate2 cert = null; X509Store store = new X509Store(StoreName.My, StoreLocation.CurrentUser); store.Open(OpenFlags.ReadOnly); X509Certificate2Collection coll = store.Certificates.Find(X509FindType.FindBySubjectDistinguishedName, "distName", true); if (coll.Count < 1) { throw new ArgumentException("Unable to locate certificate"); } cert = coll[0]; store.Close(); //this special SignDoc just overrides a function in SignedXml so //it knows to look for ResponseID rather than ID XmlElement signature = SamlHelper.SignDoc( doc, cert, "ResponseID", response.ResponseID); doc.DocumentElement.InsertBefore(signature, doc.DocumentElement.ChildNodes[0]); // Base64Encode and URL Encode byte[] base64EncodedBytes = Encoding.UTF8.GetBytes(doc.OuterXml); string returnValue = System.Convert.ToBase64String( base64EncodedBytes); return returnValue; } private AssertionType CreateSaml11Assertion(Dictionary<string, string> attributes){ AssertionType assertion = new AssertionType(); assertion.AssertionID = "_" + Guid.NewGuid().ToString(); assertion.Issuer = "madeUpValue"; assertion.MajorVersion = "1"; assertion.MinorVersion = "1"; assertion.IssueInstant = System.DateTime.UtcNow; //Not before, not after conditions ConditionsType conditions = new ConditionsType(); conditions.NotBefore = DateTime.UtcNow; conditions.NotBeforeSpecified = true; conditions.NotOnOrAfter = DateTime.UtcNow.AddMinutes(10); conditions.NotOnOrAfterSpecified = true; //Name Identifier to be used in Saml Subject NameIdentifierType nameIdentifier = new NameIdentifierType(); nameIdentifier.NameQualifier = domain.Trim(); nameIdentifier.Value = subject.Trim(); SubjectConfirmationType subjectConfirmation = new SubjectConfirmationType(); subjectConfirmation.ConfirmationMethod = new string[] { "urn:oasis:names:tc:SAML:1.0:cm:bearer" }; // // Create some SAML subject. SubjectType samlSubject = new SubjectType(); AttributeStatementType attrStatement = new AttributeStatementType(); AuthenticationStatementType authStatement = new AuthenticationStatementType(); authStatement.AuthenticationMethod = "urn:oasis:names:tc:SAML:1.0:am:password"; authStatement.AuthenticationInstant = System.DateTime.UtcNow; samlSubject.Items = new object[] { nameIdentifier, subjectConfirmation}; attrStatement.Subject = samlSubject; authStatement.Subject = samlSubject; IPHostEntry ipEntry = Dns.GetHostEntry(System.Environment.MachineName); SubjectLocalityType subjectLocality = new SubjectLocalityType(); subjectLocality.IPAddress = ipEntry.AddressList[0].ToString(); authStatement.SubjectLocality = subjectLocality; attrStatement.Attribute = new AttributeType[attributes.Count]; int i=0; // Create SAML attributes. foreach (KeyValuePair<string, string> attribute in attributes) { AttributeType attr = new AttributeType(); attr.AttributeName = attribute.Key; attr.AttributeNamespace= domain; attr.AttributeValue = new object[] {attribute.Value}; attrStatement.Attribute[i] = attr; i++; } assertion.Conditions = conditions; assertion.Items = new StatementAbstractType[] {authStatement, attrStatement}; return assertion; } private static XmlElement SignDoc(XmlDocument doc, X509Certificate2 cert2, string referenceId, string referenceValue) { // Use our own implementation of SignedXml SamlSignedXml sig = new SamlSignedXml(doc, referenceId); // Add the key to the SignedXml xmlDocument. sig.SigningKey = cert2.PrivateKey; // Create a reference to be signed. Reference reference = new Reference(); reference.Uri= String.Empty; reference.Uri = "#" + referenceValue; // Add an enveloped transformation to the reference. XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform(); reference.AddTransform(env); // Add the reference to the SignedXml object. sig.AddReference(reference); // Add an RSAKeyValue KeyInfo (optional; helps recipient find key to validate). KeyInfo keyInfo = new KeyInfo(); keyInfo.AddClause(new KeyInfoX509Data(cert2)); sig.KeyInfo = keyInfo; // Compute the signature. sig.ComputeSignature(); // Get the XML representation of the signature and save // it to an XmlElement object. XmlElement xmlDigitalSignature = sig.GetXml(); return xmlDigitalSignature; } To open the page in my client app, string postData = String.Format("SAMLResponse={0}&APID=ap_00001&TARGET={1}", System.Web.HttpUtility.UrlEncode(builder.buildResponse("http://theWLServer/samlacs/acs",attributes)), "http://desiredURL"); webBrowser.Navigate("http://theWLServer/samlacs/acs", "_self", Encoding.UTF8.GetBytes(postData), "Content-Type: application/x-www-form-urlencoded");

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  • How to change Matlab program for solving equation with finite element method?

    - by DSblizzard
    I don't know is this question more related to mathematics or programming and I'm absolute newbie in Matlab. Program FEM_50 applies the finite element method to Laplace's equation -Uxx(x, y) - Uyy(x, y) = F(x, y) in Omega. How to change it to apply FEM to equation -Uxx(x, y) - Uyy(x, y) + U(x, y) = F(x, y)? At this page: http://sc.fsu.edu/~burkardt/m_src/fem_50/fem_50.html additional code files in case you need them. function fem_50 ( ) %% FEM_50 applies the finite element method to Laplace's equation. % % Discussion: % % FEM_50 is a set of MATLAB routines to apply the finite % element method to solving Laplace's equation in an arbitrary % region, using about 50 lines of MATLAB code. % % FEM_50 is partly a demonstration, to show how little it % takes to implement the finite element method (at least using % every possible MATLAB shortcut.) The user supplies datafiles % that specify the geometry of the region and its arrangement % into triangular and quadrilateral elements, and the location % and type of the boundary conditions, which can be any mixture % of Neumann and Dirichlet. % % The unknown state variable U(x,y) is assumed to satisfy % Laplace's equation: % -Uxx(x,y) - Uyy(x,y) = F(x,y) in Omega % with Dirichlet boundary conditions % U(x,y) = U_D(x,y) on Gamma_D % and Neumann boundary conditions on the outward normal derivative: % Un(x,y) = G(x,y) on Gamma_N % If Gamma designates the boundary of the region Omega, % then we presume that % Gamma = Gamma_D + Gamma_N % but the user is free to determine which boundary conditions to % apply. Note, however, that the problem will generally be singular % unless at least one Dirichlet boundary condition is specified. % % The code uses piecewise linear basis functions for triangular elements, % and piecewise isoparametric bilinear basis functions for quadrilateral % elements. % % The user is required to supply a number of data files and MATLAB % functions that specify the location of nodes, the grouping of nodes % into elements, the location and value of boundary conditions, and % the right hand side function in Laplace's equation. Note that the % fact that the geometry is completely up to the user means that % just about any two dimensional region can be handled, with arbitrary % shape, including holes and islands. % clear % % Read the nodal coordinate data file. % load coordinates.dat; % % Read the triangular element data file. % load elements3.dat; % % Read the quadrilateral element data file. % load elements4.dat; % % Read the Neumann boundary condition data file. % I THINK the purpose of the EVAL command is to create an empty NEUMANN array % if no Neumann file is found. % eval ( 'load neumann.dat;', 'neumann=[];' ); % % Read the Dirichlet boundary condition data file. % load dirichlet.dat; A = sparse ( size(coordinates,1), size(coordinates,1) ); b = sparse ( size(coordinates,1), 1 ); % % Assembly. % for j = 1 : size(elements3,1) A(elements3(j,:),elements3(j,:)) = A(elements3(j,:),elements3(j,:)) ... + stima3(coordinates(elements3(j,:),:)); end for j = 1 : size(elements4,1) A(elements4(j,:),elements4(j,:)) = A(elements4(j,:),elements4(j,:)) ... + stima4(coordinates(elements4(j,:),:)); end % % Volume Forces. % for j = 1 : size(elements3,1) b(elements3(j,:)) = b(elements3(j,:)) ... + det( [1,1,1; coordinates(elements3(j,:),:)'] ) * ... f(sum(coordinates(elements3(j,:),:))/3)/6; end for j = 1 : size(elements4,1) b(elements4(j,:)) = b(elements4(j,:)) ... + det([1,1,1; coordinates(elements4(j,1:3),:)'] ) * ... f(sum(coordinates(elements4(j,:),:))/4)/4; end % % Neumann conditions. % if ( ~isempty(neumann) ) for j = 1 : size(neumann,1) b(neumann(j,:)) = b(neumann(j,:)) + ... norm(coordinates(neumann(j,1),:) - coordinates(neumann(j,2),:)) * ... g(sum(coordinates(neumann(j,:),:))/2)/2; end end % % Determine which nodes are associated with Dirichlet conditions. % Assign the corresponding entries of U, and adjust the right hand side. % u = sparse ( size(coordinates,1), 1 ); BoundNodes = unique ( dirichlet ); u(BoundNodes) = u_d ( coordinates(BoundNodes,:) ); b = b - A * u; % % Compute the solution by solving A * U = B for the remaining unknown values of U. % FreeNodes = setdiff ( 1:size(coordinates,1), BoundNodes ); u(FreeNodes) = A(FreeNodes,FreeNodes) \ b(FreeNodes); % % Graphic representation. % show ( elements3, elements4, coordinates, full ( u ) ); return end

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  • Is it possible to cause artificial network packet loss or latency?

    - by nbolton
    I'm trying to reproduce some issues on a deployed application where the MSSQL server and client are running in two separate machines. I think there may be network issues between the two machines, so I'd like to try and reproduce these conditions on two Hyper-V virtual machines (on the same virtual server). Of course, the network for these virtual machines is "local" so it's actually far from the conditions in a live environment. Is there a program I can run on either virtual machine which will degrade the network performance? Or maybe any other work arounds? For example, one way to reproduce the conditions may be to run the VMs on separate Hyper-V servers in geographically dispersed locations (so the SQL traffic goes over VPN or something) -- but this is a little long winded I think. There must be a simpler way.

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