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• Need advice or pointers on Release Management Strategies

  - by Murray

  I look after an internal web based (Java, JSP, Mediasurface, etc.) system that is in constant use (24/5). Users raise tickets for enhancements, bug fixes and other business changes. These issues are signed off individually and assigned to one of three or four developers. Once the issue is complete it is built and the code only committed to SVN. The changed files (templates, html, classes, jsp) are then copied to a dev server and committed to a different repository from where they are checked out to the UAT server for testing. (this often requires the Tomcat service to be restarted and occasionally the Mediasurface service as well). The users then test and either reject or approve the release. If approved the edited files are checked out to the Live server and the same process as with UAT undertaken. If rejected the developer makes the relevant changes and starts the release process again. This is all done manually without much control. Where different developers are working on similar files, changes sometimes get overwritten by builds done on out of sync code in other cases changes in UAT are moved to live in error as they are mixed up in files associated with a signed off release. I would like to move this to a more controlled and automated process where all source code and output files are held in SVN and releases to Dev, UAT and Live managed by a CI system (We have TeamCity in house for our .NET applications). My question is on how to manage the releases of multiple changes where some will be signed off and moved on and others rejected and returned to the developer. The changes may be on overlapping files and simply merging each release in to a Release Branch means that the rejected changes would have to be backed out of the branch. Is there a way to manage this using SVN and CI or will I simply have to live with the current system.

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• What are common anti-patterns when using VBA

  - by Ahmad

  I have being coding a lot in VBA lately (maintenance and new code), specifically with regards to Excel automation etc. = macros. Typically most of this has revolved around copy/paste, send some emails, import some files etc. but eventually just ends up as a Big ball of mud As a person who values clean code, I find it very difficult to produce 'decent' code when using VBA. I think that in most cases, this is a direct result of the macro-recorder. Very helpful to get you started, but most times, there are one too many lines of code that achieve the end result. Edit: The code from the macro-recorder is used as a base to get started, but is not used in its entirety in the end result I have already created a common addin that has my commonly used subroutines and some utility classes in an early attempt to enforce some DRYness - so this I think is a step in the right direction. But I feel as if it's a constant square peg, round hole situation. The wiki has an extensive list of common anti-patterns and what scared me the most was how many I have implemented in one way or another. The question Now considering, that my mindset is OO design, what some common anti-patterns and the possible solutions when designing a solution (think of this - how would designing a solution using Excel and VBA be different from say a .net/java/php/.../ etc solution) ; and when doing common tasks like copying data, emailing, data importing, file operations... etc An anti-pattern as defined by Wikipedia is: In software engineering, an anti-pattern (or antipattern) is a pattern that may be commonly used but is ineffective and/or counterproductive in practice

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• How to override ATTR_DEFAULT_IDENTIFIER_OPTIONS in Models in Doctrine?

  - by user309083

  Here someone explained that setting a 'primary' attribute for any row in your Model will override Doctrine_Manager's ATTR_DEFAULT_IDENTIFIER_OPTIONS attribute: http://stackoverflow.com/questions/2040675/how-do-you-override-a-constant-in-doctrines-models This works, however if you have a many to many relation whereby the intermediate table is created, even if you have set both columns in the intermediate to primary an error still results when Doctrine tries to place an index on the nonexistant 'id' column upon table creation. Here's my code: //Bootstrap // set the default primary key to be named 'id', integer, 4 bytes Doctrine_Manager::getInstance()->setAttribute( Doctrine_Core::ATTR_DEFAULT_IDENTIFIER_OPTIONS, array('name' => 'id', 'type' => 'integer', 'length' => 4)); //User Model class User extends Doctrine_Record { public function setTableDefinition() { $this->setTableName('users'); } public function setUp() { $this->hasMany('Role as roles', array( 'local' => 'id', 'foreign' => 'user_id', 'refClass' => 'UserRole', 'onDelete' => 'CASCADE' )); } } //Role Model class Role extends Doctrine_Record { public function setTableDefinition() { $this->setTableName('roles'); } public function setUp() { $this->hasMany('User as users', array( 'local' => 'id', 'foreign' => 'role_id', 'refClass' => 'UserRole' )); } } //UserRole Model class UserRole extends Doctrine_Record { public function setTableDefinition() { $this->setTableName('roles_users'); $this->hasColumn('user_id', 'integer', 4, array('primary'=>true)); $this->hasColumn('role_id', 'integer', 4, array('primary'=>true)); } } Resulting error: SQLSTATE[42000]: Syntax error or access violation: 1072 Key column 'id' doesn't exist in table. Failing Query: "CREATE TABLE roles_users (user_id INT UNSIGNED NOT NULL, role_id INT UNSIGNED NOT NULL, INDEX id_idx (id), PRIMARY KEY(user_id, role_id)) ENGINE = INNODB". Failing Query: CREATE TABLE roles_users (user_id INT UNSIGNED NOT NULL, role_id INT UNSIGNED NOT NULL, INDEX id_idx (id), PRIMARY KEY(user_id, role_id)) ENGINE = INNODB I'm creating my tables using Doctrine::createTablesFromModels();

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• How to use Sprockets Rails plugin on Heroku?

  - by Kevin

  Hi, I just deployed my Rails app to Heroku, but the Javascripts that were using Sprockets plugin don't work. I understood that, because my Heroku app is read-only, Sprockets won't work. I've found this sprockets_on_heroku plugin that should do the work, but I don't really get how to use it : I added config.gem sprockets in config/environment.rb I added sprockets in my .gems file I pushed these on Heroku and Sprockets was successfully installed I locally ran script/plugin install git://github.com/jeffrydegrande/sprockets_on_heroku.git and the plugin was successfully installed Nothing changed on Heroku, so I tried to install the plugin on Heroku with heroku plugins:install git://github.com/jeffrydegrande/sprockets_on_heroku.git, which returned sprockets_on_heroku installedbut then, a heroku restartor a heroku pluginscommand would return this: ~/.heroku/plugins/sprockets_on_heroku/init.rb:1: uninitialized constant ActionController (NameError) from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/../lib/heroku/plugin.rb:25:in `load' from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/../lib/heroku/plugin.rb:25:in `load!' from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/../lib/heroku/plugin.rb:22:in `each' from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/../lib/heroku/plugin.rb:22:in `load!' from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/../lib/heroku/command.rb:14:in `run' from /opt/local/lib/ruby/gems/1.8/gems/heroku-1.8.3/bin/heroku:14 from /opt/local/bin/heroku:19:in `load' from /opt/local/bin/heroku:19 What should I do? Kevin

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• Ruby through RVM fails

  - by TheLQ

  In constant battle to install Ruby 1.9.2 on an RPM system (OS is based off of CentOS), I'm trying again with RVM. So once I install it, I then try to use it: [root@quackwall ~]# rvm use 1.9.2 Using /usr/local/rvm/gems/ruby-1.9.2-p136 [root@quackwall ~]# ruby bash: ruby: command not found [root@quackwall ~]# which ruby /usr/bin/which: no ruby in (/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin) Now that's interesting; rvm info says something completely different: [root@quackwall bin]# rvm info ruby-1.9.2-p136: system: uname: "Linux quackwall.highwow.lan 2.6.18-194.8.1.v5 #1 SMP Thu Jul 15 01:14:04 EDT 2010 i686 i686 i386 GNU/Linux" bash: "/bin/bash => GNU bash, version 3.2.25(1)-release (i686-redhat-linux-gnu)" zsh: " => not installed" rvm: version: "rvm 1.2.2 by Wayne E. Seguin ([email protected]) [http://rvm.beginrescueend.com/]" ruby: interpreter: "ruby" version: "1.9.2p136" date: "2010-12-25" platform: "i686-linux" patchlevel: "2010-12-25 revision 30365" full_version: "ruby 1.9.2p136 (2010-12-25 revision 30365) [i686-linux]" homes: gem: "/usr/local/rvm/gems/ruby-1.9.2-p136" ruby: "/usr/local/rvm/rubies/ruby-1.9.2-p136" binaries: ruby: "/usr/local/rvm/rubies/ruby-1.9.2-p136/bin/ruby" irb: "/usr/local/rvm/rubies/ruby-1.9.2-p136/bin/irb" gem: "/usr/local/rvm/rubies/ruby-1.9.2-p136/bin/gem" rake: "/usr/local/rvm/gems/ruby-1.9.2-p136/bin/rake" environment: PATH: "/usr/local/rvm/gems/ruby-1.9.2-p136/bin:/usr/local/rvm/gems/ruby-1.9.2-p136@global/bin:/usr/local/rvm/rubies/ruby-1.9.2-p136/bin:bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin:/usr/local/rvm/bin" GEM_HOME: "/usr/local/rvm/gems/ruby-1.9.2-p136" GEM_PATH: "/usr/local/rvm/gems/ruby-1.9.2-p136:/usr/local/rvm/gems/ruby-1.9.2-p136@global" MY_RUBY_HOME: "/usr/local/rvm/rubies/ruby-1.9.2-p136" IRBRC: "/usr/local/rvm/rubies/ruby-1.9.2-p136/.irbrc" RUBYOPT: "" gemset: "" So I have RVM that says one thing and bash which says another. Any suggestions on how to get this working?

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• Need some help for the issues that caused because of secret key in rails application

  - by sam

  I have a weird problem. I have a rails application. When I am trying to run the ruby script/about command, it is displaying the details when the secret key in config/initializers/session_store.rb was removed or commented. When I place the secret key in the file and if i runs the ruby script/about command it is throwing error as c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependenc es.rb:443:in `load_missing_constant': uninitialized constant ActionController ( ameError) from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_supp rt/dependencies.rb:80:in `const_missing' from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_supp rt/dependencies.rb:92:in `const_missing' from D:/chat/config/initializers/session_store.rb:13 from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `g m_original_require' from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `r quire' from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_supp rt/dependencies.rb:156:in `require' from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_supp rt/dependencies.rb:521:in `new_constants_in' from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_supp rt/dependencies.rb:156:in `require' ... 7 levels... from c:/ruby/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/commands/about.rb:1 from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `g m_original_require' from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `r quire' from script/about:3 In config/initializers/session_store.rb file the error is shown for the below code. ActionController::Base.session = { :key => '_chat_session', :secret => '0fb230c7ae72f9a0cb2417b0ad75db3b48cabf327eeedb0557ae07ecf894f34f55e2dfb9ce6c49f05959ceac9812a7193de04690a931fcf757973195a84cd2d2' } Could anyone please help me. Thanks in-advance, sam

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• Android HttpClient and HTTPS

  - by user309769

  Hi all, I'm new to implementing HTTPS connections in Android. Essentially, I'm trying to connect to a server using the org.apache.http.client.HttpClient. I believe, at some point, I'll need to access the application's keystore in order to authorize my client with a private key. But, for the moment, I'm just trying to connect and see what happens; I keep getting an HTTP/1.1 400 Bad Request error. I can't seem to make heads or tails of this despite many examples (none of them seem to work for me). My code looks like this (the BODY constant is XmlRPC): private void connect() throws IOException, URISyntaxException{ HttpPost post = new HttpPost(new URI(PROD_URL)); HttpClient client = new DefaultHttpClient(); post.setEntity(new StringEntity(BODY)); HttpResponse result = client.execute(post); Log.d("MainActivity", result.getStatusLine().toString()); } So, pretty simple. Let me know if anyone out there has any advice. Thanks!

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• Variable number of two-dimensional arrays into one big array

  - by qlb

  I have a variable number of two-dimensional arrays. The first dimension is variable, the second dimension is constant. i.e.: Object[][] array0 = { {"tim", "sanchez", 34, 175.5, "bla", "blub", "[email protected]"}, {"alice", "smith", 42, 160.0, "la", "bub", "[email protected]"}, ... }; Object[][] array1 = { {"john", "sdfs", 34, 15.5, "a", "bl", "[email protected]"}, {"joe", "smith", 42, 16.0, "a", "bub", "[email protected]"}, ... }; ... Object[][] arrayi = ... I'm generating these arrays with a for-loop: for (int i = 0; i < filter.length; i++) { MyClass c = new MyClass(filter[i]); //data = c.getData(); } Where "filter" is another array which is filled with information that tells "MyClass" how to fill the arrays. "getData()" gives back one of the i number of arrays. Now I just need to have everything in one big two dimensional array. i.e.: Object[][] arrayComplete = { {"tim", "sanchez", 34, 175.5, "bla", "blub", "[email protected]"}, {"alice", "smith", 42, 160.0, "la", "bub", "[email protected]"}, ... {"john", "sdfs", 34, 15.5, "a", "bl", "[email protected]"}, {"joe", "smith", 42, 16.0, "a", "bub", "[email protected]"}, ... ... }; In the end, I need a 2D array to feed my Swing TableModel. Any idea on how to accomplish this? It's blowing my mind right now.

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• Hidden features of Perl?

  - by Adam Bellaire

  What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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• How to upgrade the project build in visual studio 2005 to visual studio 2008?

  - by Shailesh Jaiswal

  I have one OPC ( OLE for Process control ) server project which is developed into visual studio 2005. I want to run it in visual studio 2008. The coding for the OPC server project is done in VC++. I want to connect my OPC client to this OPC server. When I was opened the OPC server project which was build into visual studio 2005 into visual studio 2008 first time it was asking for conversion wizard. I gone through that wizard & successfully finished that wizard. But when I build ( by right clicking on the project & choosing build solution ) it is giving lots of error near about 64 errors. Most of the errors are like - fetal error C1083:Can not open type library file:'msxml4.dll':No such file or directory, fetal error LINK1181:can not open input file 'rpcndr.lib' , error C2051:case expression not constant. only these 3 types of errors in am getting. All these 3 errors are repeated in Error list & becoming bunch of 64 errors. Please provide me the solution for the above issue. Can you provide me any suusgestion or link or any way through whcih I can resolve the above issue?

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• Regression Testing and Deployment Strategy

  - by user279516

  I'd like some advice on a deployment strategy. If a development team creates an extensive framework, and many (20-30) applications consume it, and the business would like application updates at least every 30 days, what is the best deployment strategy? The reason I ask is that there seems to be a lot of waste (and risk) in using an agile approach of deploying changes monthly, if 90% of the applications don't change. What I mean by this is that the framework can change during the month, and so can a few applications. Because the framework changed, all applications should be regression-tested. If, say, 10 of the applications don't change at all during the year, then those 10 applications are regression-tested EVERY MONTH, when they didn't have any feature changes or hot fixes. They had to be tested simply because the business is rolling updates every month. And the risk that is involved... if a mission-critical application is deployed, that takes a few weeks, and multiple departments, to test, is it realistic to expect to have to constantly regression-test this application? One option is to make any framework updates backward-compatible. While this would mean that applications don't need to change their code, they would still need to be tested because the underlying framework changed. And the risk involved is great; a constantly changing framework (and deploying this framework) means the mission-critical app can never just enjoy the same code base for a long time. These applications share the same database, hence the need for the constant testing. I'm aware of TDD and automated tests, but that doesn't exist at the moment. Any advice?

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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• Problem running RoR app in production environment

  - by normalocity

  Have an app that has "listings" - think classified ads - and each listing has a list of tags. The following code fails when I run the app in production mode, but works fine under development mode uninitialized constant ActiveRecord::Acts::Taggable::InstanceMethods::TagList Extracted source (around line #45): 42: 43: <span class="listingIndexTags"> 44: Location: [location] | Tags: 45: <% tag_list = listing.tag_list %> 46: <% if tag_list != nil %> 47: <% for tag in tag_list %> 48: <%= link_to tag.to_s, { :action => "filter_on", The command line I'm using to start my mongrel instance in this test case: ruby script/server mongrel -e development Defaults to port 3000. I can access other views in the app that DON'T call "listing.tag_list". ".tag_list" is provided by "acts_as_taggable_on_steroids", which I'm using in this app. It is installed as a gem. Maybe my environment files are wonky? Here's my development.rb file config.cache_classes = false config.whiny_nils = true config.action_controller.consider_all_requests_local = true config.action_view.debug_rjs = true config.action_controller.perform_caching = false config.action_mailer.raise_delivery_errors = true config.action_mailer.delivery_method = :smtp config.action_mailer.smtp_settings = { ...took these settings out for this post... } And my production.rb file... config.cache_classes = true config.threadsafe! config.action_controller.consider_all_requests_local = false config.action_controller.perform_caching = true config.cache_store = :mem_cache_store config.action_mailer.raise_delivery_errors = false config.action_mailer.delivery_method = :smtp config.action_mailer.smtp_settings = { ...took these settings out for this post... }

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• How to know about MySQL 'refused connections'

  - by celalo

  Hello, I am using MONyog to montitor my two mysql servers. I get alert emails from MONyog when something goes wrong. There is an error I could not find out why. It says: Connection History: Percentage of refused connections) - 66.67% the percentage is not important, this is just about having refused connections. I get this email every half an hour. So this is like a constant situation. This must be my mistake, because I just set up those servers and there is no chance somebody else could be interfering the servers. MONyog advices me: Try to isolate users/applications that are using an incorrect password or trying to connect from unauthorized hosts. A client will be disallowed to connect if it takes more than connect_timeout seconds to connect. Set the value of log_warnings system variable to 2. This will force the MySQL server to log further information about the error. I added log_warnings=2 to my.cnf and I enabled logging like this: [mysqld_safe] . . log_warnings=2 log-error = /var/log/mysql/error.log . . . . [mysqld_safe] . log-error=/var/log/mysqld.log . . I cannot see any warnings at /var/log/mysql/error.log I can see some warnings at /var/log/mysqld.log but they are about something else. In sum, my question is how can I detect refused connections? Please let me know if any more info is required. Thanks in advance.

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• Bitwise Interval Arithmetic

  - by KennyTM

  I've recently read an interesting thread on the D newsgroup, which basically asks, Given two signed integers a ∈ [amin, amax], b ∈ [bmin, bmax], what is the tightest interval of a | b? I'm think if interval arithmetics can be applied on general bitwise operators (assuming infinite bits). The bitwise-NOT and shifts are trivial since they just corresponds to -1 − x and 2n x. But bitwise-AND/OR are a lot trickier, due to the mix of bitwise and arithmetic properties. Is there a polynomial-time algorithm to compute the intervals of bitwise-AND/OR? Note: Assume all bitwise operations run in linear time (of number of bits), and test/set a bit is constant time. The brute-force algorithm runs in exponential time. Because ~(a | b) = ~a & ~b and a ^ b = (a | b) & ~(a & b), solving the bitwise-AND and -NOT problem implies bitwise-OR and -XOR are done. Although the content of that thread suggests min{a | b} = max(amin, bmin), it is not the tightest bound. Just consider [2, 3] | [8, 9] = [10, 11].)

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• What is the difference between AF_INET and PF_INET constants?

  - by Denilson Sá

  Looking at examples about socket programming, we can see that some people use AF_INET while others use PF_INET. In addition, sometimes both of them are used at the same example. The question is: Is there any difference between them? Which one should we use? If you can answer that, another question would be... Why there are these two similar (but equal) constants? What I've discovered, so far: The socket manpage In (Unix) socket programming, we have the socket() function that receives the following parameters: int socket(int domain, int type, int protocol); The manpage says: The domain argument specifies a communication domain; this selects the protocol family which will be used for communication. These families are defined in <sys/socket.h>. And the manpage cites AF_INET as well as some other AF_ constants for the domain parameter. Also, at the NOTES section of the same manpage, we can read: The manifest constants used under 4.x BSD for protocol families are PF_UNIX, PF_INET, etc., while AF_UNIX etc. are used for address families. However, already the BSD man page promises: "The protocol family generally is the same as the address family", and subsequent standards use AF_* everywhere. The C headers The sys/socket.h does not actually define those constants, but instead includes bits/socket.h. This file defines around 38 AF_ constants and 38 PF_ constants like this: #define PF_INET 2 /* IP protocol family. */ #define AF_INET PF_INET Python The Python socket module is very similar to the C API. However, there are many AF_ constants but only one PF_ constant (PF_PACKET). Thus, in Python we have no choice but use AF_INET. I think this decision to include only the AF_ constants follows one of the guiding principles: "There should be one-- and preferably only one --obvious way to do it." (The Zen of Python)

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• MySQL Connector for .NET - Is it REALLY mature?

  - by effkay

  After spending a miserable month with MySQL/.NET/EntityFramework, my findings: Support for Entity Framework is VERY primitive, please use it for student-subjects type of database. Kindly do not consider it using for serious development as they ARE STILL unable to sort out VERY BASIC things like: it DOES NOT support unsigned stuff it DOES NOT support unsigned columns as FK; if you try, it gives you a beautiful exception; "The specified value is not an instance of a valid constant type\r\nParameter name: value" [http://bugs.mysql.com/bug.php?id=44801] blob cannot store more then few KB; cannot compare null object with a column with a LEGAL null value [http://bugs.mysql.com/bug.php?id=49936] they are unable to write VERY PRIMITIVE check to return date as null if value in column is 0000-00-00 00:00:00 if you use Visual Studio; sorry; mysql/sun guys hate Microsoft, they will NOT LET you import more then two or three tables (for Micky Mouse type of tables, they allow five; but thats it) - if you try, it will throw TIME OUT error on your face ... unless you are smart enough to change the connection time in connection string Anyone who would like to add in above list? WISH I would have seen a list like this before I selected MySQL :(

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• Secure hash and salt for PHP passwords

  - by luiscubal

  It is currently said that MD5 is partially unsafe. Taking this into consideration, I'd like to know which mechanism to use for password protection. Is “double hashing” a password less secure than just hashing it once? Suggests that hashing multiple times may be a good idea. How to implement password protection for individual files? Suggests using salt. I'm using PHP. I want a safe and fast password encryption system. Hashing a password a million times may be safer, but also slower. How to achieve a good balance between speed and safety? Also, I'd prefer the result to have a constant number of characters. The hashing mechanism must be available in PHP It must be safe It can use salt (in this case, are all salts equally good? Is there any way to generate good salts?) Also, should I store two fields in the database(one using MD5 and another one using SHA, for example)? Would it make it safer or unsafer? In case I wasn't clear enough, I want to know which hashing function(s) to use and how to pick a good salt in order to have a safe and fast password protection mechanism. EDIT: The website shouldn't contain anything too sensitive, but still I want it to be secure. EDIT2: Thank you all for your replies, I'm using hash("sha256",$salt.":".$password.":".$id) Questions that didn't help: What's the difference between SHA and MD5 in PHP Simple Password Encryption Secure methods of storing keys, passwords for asp.net How would you implement salted passwords in Tomcat 5.5

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• shortest digest of a string

  - by meta

  [Description] Given a string of char type, find a shortest digest, which is defined as: a shortest sub-string which contains all the characters in the original string. [Example] A = "aaabedacd" B = "bedac" is the answer. [My solution] Define an integer table with 256 elements, which is used to record the occurring times for each kind of character in the current sub-string. Scan the whole string, statistic the total kinds of character in the given string by using the above table. Use two pointers, start, end, which are initially pointing to the start and (start + 1) of the given string. The current kinds of character is 1. Expand sub-string[start, end) at the end until it contains all kinds of character. Update the shortest digest if possible. Contract sub-string[start, end] at the start by one character each time, try to restore its digest property if necessary by step 4. The time cost is O(n), and the extra space cost is constant. Any better solution without extra space?

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• Stack and Hash joint

  - by Alexandru

  I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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• Two strange efficiency problems in Mathematica

  - by Jess Riedel

  FIRST PROBLEM I have timed how long it takes to compute the following statements (where V[x] is a time-intensive function call): Alice = Table[V[i],{i,1,300},{1000}]; Bob = Table[Table[V[i],{i,1,300}],{1000}]^tr; Chris_pre = Table[V[i],{i,1,300}]; Chris = Table[Chris_pre,{1000}]^tr; Alice, Bob, and Chris are identical matricies computed 3 slightly different ways. I find that Chris is computed 1000 times faster than Alice and Bob. It is not surprising that Alice is computed 1000 times slower because, naively, the function V must be called 1000 more times than when Chris is computed. But it is very surprising that Bob is so slow, since he is computed identically to Chris except that Chris stores the intermediate step Chris_pre. Why does Bob evaluate so slowly? SECOND PROBLEM Suppose I want to compile a function in Mathematica of the form f(x)=x+y where "y" is a constant fixed at compile time (but which I prefer not to directly replace in the code with its numerical because I want to be able to easily change it). If y's actual value is y=7.3, and I define f1=Compile[{x},x+y] f2=Compile[{x},x+7.3] then f1 runs 50% slower than f2. How do I make Mathematica replace "y" with "7.3" when f1 is compiled, so that f1 runs as fast as f2? Many thanks!

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• Collision detection of huge number of circles

  - by Tomek Tarczynski

  What is the best way to check collision of huge number of circles? It's very easy to detect collision between two circles, but if we check every combination then it is O(n^2) which definitely not an optimal solution. We can assume that circle object has following properties: -Coordinates -Radius -Velocity -Direction Velocity is constant, but direction can change. I've come up with two solutions, but maybe there are some better solutions. Solution 1 Divide whole space into overlapping squares and check for collision only with circles that are in the same square. Squares needs to overlap so there won't be a problem when circle moves from one square to another. Solution 2 At the beginning distances between every pair of circles need to be calculated. If the distance is small then these pair is stored in some list, and we need to check for collision in every update. If the distance is big then we store after which update there can be a collision (it can be calculated because we know the distance and velocitites). It needs to be stored in some kind of priority queue. After previously calculated number of updates distance needs to be checked again and then we do the same procedure - put it on the list or again in the priority queue.

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• Bubble Breaker Game Solver better than greedy?

  - by Gregory

  For a mental exercise I decided to try and solve the bubble breaker game found on many cell phones as well as an example here:Bubble Break Game The random (N,M,C) board consists N rows x M columns with C colors The goal is to get the highest score by picking the sequence of bubble groups that ultimately leads to the highest score A bubble group is 2 or more bubbles of the same color that are adjacent to each other in either x or y direction. Diagonals do not count When a group is picked, the bubbles disappear, any holes are filled with bubbles from above first, ie shift down, then any holes are filled by shifting right A bubble group score = n * (n - 1) where n is the number of bubbles in the bubble group The first algorithm is a simple exhaustive recursive algorithm which explores going through the board row by row and column by column picking bubble groups. Once the bubble group is picked, we create a new board and try to solve that board, recursively descending down Some of the ideas I am using include normalized memoization. Once a board is solved we store the board and the best score in a memoization table. I create a prototype in python which shows a (2,15,5) board takes 8859 boards to solve in about 3 seconds. A (3,15,5) board takes 12,384,726 boards in 50 minutes on a server. The solver rate is ~3k-4k boards/sec and gradually decreases as the memoization search takes longer. Memoization table grows to 5,692,482 boards, and hits 6,713,566 times. What other approaches could yield high scores besides the exhaustive search? I don't seen any obvious way to divide and conquer. But trending towards larger and larger bubbles groups seems to be one approach Thanks to David Locke for posting the paper link which talks above a window solver which uses a constant-depth lookahead heuristic.

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• Why is WMDC/ActiveSync so flaky?

  - by Ira Rainey

  I'm developing a Windows Mobile app using the .NET Compact Framework 3.5 and VS2008, and for debugging using the Device Emulator V3, on Win7, and seem to have constant problems with Windows Mobile Device Centre (6.1) connecting. Using the Emulator Manager (9.0.21022.8) I cradle the device using DMA in WMDC. The problem is it's so flaky at actually connecting that it's becoming a pain. I find that when I turn my computer on, before I can get it to connect I have to open up WMDC, disable Connect over DMA, close WMDC down, reopen it again, and then it might cradle. Often I have to do this twice before it will cradle. Once it's cradled it's generally fine, but nothing seems consistent in getting it to connect. Connecting with physical devices is often better, although not always. If I plug a PDA into a USB socket other than the one it was originally plugged into then it won't connect at all. Often the best/most reliable connection method seems to be over Bluetooth, but that's quite slow. Anybody got any tips or advice?

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• testing devise with shoulda and machinist

  - by mattherick

  hello! I´d like to test my app with shoulda and machinist. I use the devise authentification gem. I get following error: $ ruby unit/page_test.rb c:/Ruby/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be rem oved on or after August 2010. Use #requirement c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:443:in load_missing_constant': uninitialized constant Admins (N ameError) from c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:80:inconst_missing' from c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:92:in const_missing' from c:/Users/Mattherick/Desktop/heimspiel/heimspiel_app/app/controllers/admins_controller.rb:1 from c:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:ingem_original_require' from c:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in require' from c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:158:inrequire' from c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:265:in require_or_load' from c:/Ruby/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:224:independ_on' ... 12 levels... from ./unit/../test_helper.rb:2 from c:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from c:/Ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire' from unit/page_test.rb:1 Somebody an idea what´s wrong? If I don´t use devise my tests are okay. And my second question: Does somebdoy has a good tutorial for increasing different roles in the devise gem? If I generate my own views and add a few attributes to my devise-model, they won´t be save in the database. I read the docu at github, but don´t really checked it. mattherick

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