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• Personal Cache vs Memcache?

  - by Kerry

  I have a personal caching class, which can be seen here ( based off WordPress' ): http://pastie.org/988427 I recently learned about memcache and it said to memcache EVERYTHING: http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html My first thought was just to keep my class with the current functions and make it use memcache instead -- is there any downside to doing this? The main difference I see is that memcache stays on with the server from page to page, while mine is for 1 page load. The problem I see arising, and this is with any system, is that they're dynamic. They change all the time. Whether its search results, visible products, etc. etc. If it's all cached, won't the create a problem? Is there a way to handle this? Obviously if something is bringing back the same results everytime it would be cached, but that's why I was doing it on a per page load basis. I'm sure there is a way to handle this, or is the cache time usually set between 5 minutes and an hour?

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• MSSQL Search Proper Names Full Text Index vs LIKE + SOUNDEX

  - by Matthew Talbert

  I have a database of names of people that has (currently) 35 million rows. I need to know what is the best method for quickly searching these names. The current system (not designed by me), simply has the first and last name columns indexed and uses "LIKE" queries with the additional option of using SOUNDEX (though I'm not sure this is actually used much). Performance has always been a problem with this system, and so currently the searches are limited to 200 results (which still takes too long to run). So, I have a few questions: Does full text index work well for proper names? If so, what is the best way to query proper names? (CONTAINS, FREETEXT, etc) Is there some other system (like Lucene.net) that would be better? Just for reference, I'm using Fluent NHibernate for data access, so methods that work will with that will be preferred. I'm using MS SQL 2008 currently.

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• C# vs C - Big performance difference

  - by John

  I'm finding massive performance differences between similar code in C anc C#. The C code is: #include <stdio.h> #include <time.h> #include <math.h> main() { int i; double root; clock_t start = clock(); for (i = 0 ; i <= 100000000; i++){ root = sqrt(i); } printf("Time elapsed: %f\n", ((double)clock() - start) / CLOCKS_PER_SEC); } And the C# (console app) is: using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { DateTime startTime = DateTime.Now; double root; for (int i = 0; i <= 100000000; i++) { root = Math.Sqrt(i); } TimeSpan runTime = DateTime.Now - startTime; Console.WriteLine("Time elapsed: " + Convert.ToString(runTime.TotalMilliseconds/1000)); } } } With the above code, the C# completes in 0.328125 seconds (release version) and the C takes 11.14 seconds to run. The c is being compiled to a windows executable using mingw. I've always been under the assumption that C/C++ were faster or at least comparable to C#.net. What exactly is causing the C to run over 30 times slower? EDIT: It does appear that the C# optimizer was removing the root as it wasn't being used. I changed the root assignment to root += and printed out the total at the end. I've also compiled the C using cl.exe with the /O2 flag set for max speed. The results are now: 3.75 seconds for the C 2.61 seconds for the C# The C is still taking longer, but this is acceptable

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• Loading an OverlayView from XIB -vs- programmatically for use with UIImagePickerController

  - by PLG

  I am currently making a camera app for iPhone and I have a strange phenomenon that I can't figure out. I would appreciate some help understanding. When recreating an overlay view for passing to UIImagePickerController, I have been successfully been able to create the view programmatically. What I haven't been able to do is create the view with/without controller in IB, load it and pass it to the overlay pointer successfully. If I do it via IB, the view is not opaque and obscures the view of the camera completely. I can not figure out why. I was thinking that the normal view pointer might be assigned when loading from XIB and therefore overwrite the camera's view, but I have an example programmatically where view and overlayView are set equal in the controller class. Perhaps the load order is overwriting a pointer? Help would be appreciated... kind regards.

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• android mobile development performance vs extensibility

  - by mixm

  im developing a game in android, and i've been thinking about subdividing many of the elements of the game (e.g. game objects) into separate classes and sub-classes. but i know that method calls to these objects will cause some overhead. would it be better to improve performance or to improve extensibility?

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• non-copyable objects and value initialization: g++ vs msvc

  - by R Samuel Klatchko

  I'm seeing some different behavior between g++ and msvc around value initializing non-copyable objects. Consider a class that is non-copyable: class noncopyable_base { public: noncopyable_base() {} private: noncopyable_base(const noncopyable_base &); noncopyable_base &operator=(const noncopyable_base &); }; class noncopyable : private noncopyable_base { public: noncopyable() : x_(0) {} noncopyable(int x) : x_(x) {} private: int x_; }; and a template that uses value initialization so that the value will get a known value even when the type is POD: template <class T> void doit() { T t = T(); ... } and trying to use those together: doit<noncopyable>(); This works fine on msvc as of VC++ 9.0 but fails on every version of g++ I tested this with (including version 4.5.0) because the copy constructor is private. Two questions: Which behavior is standards compliant? Any suggestion of how to work around this in gcc (and to be clear, changing that to T t; is not an acceptable solution as this breaks POD types). P.S. I see the same problem with boost::noncopyable.

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• VS 2008 created shortcut doesn't show up in "Send To" menu

  - by Brettski

  I have a WinForms application built using Visual Studio 2008. I added a Setup Project to the solution to create an installation MSI file. I need the setup project to create a shortcut pointing to the application's executable in the users Send To Menu. This way when someone right clicks on a file, my application will show in the Send To list and be selected. I figured out under the file system settings of the Setup project how to add a shortcut to the Users Send To Menu. The problem is, the shortcut doesn't show in the Send To menu when you right click on a file. If I manually create a shortcut to my executable the application does show in the Send To menu. I have read many suggestions on the web to required registry entries for this to work. There is a VBS file written by Ramesh Srinivasan which inserts them. On every system I have tried this on the registry values already existed, so this is not the problem. It seems more to be with the shortcut Visual Studio (or the msi anyway) is creating.

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• immutable strings vs std::string

  - by Caspin

  I've recent been reading about immutable strings, here and here as well some stuff about why D chose immutable strings. There seem to be many advantages. trivially thread safe more secure more memory efficient in most use cases. cheap substrings (tokenizing and slicing) Not to mention most new languages have immutable strings, D2.0, Java, C#, Python, Ruby, etc. Would C++ benefit from immutable strings? Is it possible to implement an immutable string class in c++ (or c++0x) that would have all of these advantages?

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• About browser applications: Native code vs Applets with certificates

  - by user341761

  Hey guys, I've been reading about the new native client support for chrome and I was wondering what are the advantages/disavantages compared to writing Java applet with a certificate? Quick note: A java applet with a security certificate can execute code on the user machine and "by-pass" the Java Security Manager. Thanks, -hbt

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• ruby send vs __send__

  - by jaydel

  I understand the concept of some_instance.send but I'm trying to figure out why you can call this both ways? The Ruby Koans imply that there is some reason beyond providing lots of different ways to do the same thing and I'm wrestling with figuring this out. Here are the two examples of usage more concretely class Foo def bar? true end end foo = Foo.new foo.send(:bar?) foo.send(:bar?) Anyone have any idea about this? thanks in advance!

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• plist vs static array

  - by morticae

  Generally, I use static arrays and dictionaries for containing lookup tables in my classes. However, with the number of classes creeping quickly into the hundreds, I'm hesitant to continue using this pattern. Even if these static collections are initialized lazily, I've essentially got a bounded memory leak going on as someone uses my app. Most of these are arrays of strings so I can convert strings into NSInteger constants that can be used with switch statements, etc. I could just recreate the array/dictionary on every call, but many of these functions are used heavily and/or in tight loops. So I'm trying to come up with a pattern that is both performant and not persistent. If I store the information in a plist, does the iphoneOS do anything intelligent about caching those when loaded? Do you have another method that might be related?

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• Entity Framework: Data Centric vs. Object Centric

  - by Eric J.

  I'm having a look at Entity Framework and everything I'm reading takes a data centric approach to explaining EF. By that I mean that the fundamental relationships of the system are first defined in the database and objects are generated that reflect those relationships. Examples Quickstart (Entity Framework) Using Entity Framework entities as business objects? The EF documentation implies that it's not necessary to start from the database layer, e.g. Developers can work with a consistent application object model that can be mapped to various storage schemas When designing a new system (simplified version), I tend to first create a class model, then generate business objects from the model, code business layer stuff that can't be generated, and then worry about persistence (or rather work with a DBA and let him worry about the most efficient persistence strategy). That object centric approach is well supported by ORM technologies such as (n)Hibernate. Is there a reasonable path to an object centric approach with EF? Will I be swimming upstream going that route? Any good starting points?

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• Load vs Get in Nhibernate

  - by Quintin Par

  The master page in my web application does authentication and loads up the user entity using a Get. After this whenever the user object is needed by the usercontrols or any other class I do a Load. Normally nhibernate is supposed to load the object from cache or return the persistent loaded object whenever Load of called. But this is not the behavior shown by my web application. NHprof always shows the sql whenever Load is called. How do I verify the correct behavior of Load? I use the S#arp architecture framework.

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• How to implement web cache: internal fragmentation VS external fragmentation

  - by Summer_More_More_Tea

  Hi there: I come up with this question when play with Firefox web cache: in which approach does the browser cache a response in limited disk space(take my configuration as an example, 50MB is the upper bound)? I think two ways can be employed. One is cache the total response object one by one, but this is inefficient and will introduce external fragmentation, thus the total cache space may not be fully used. The second is take the total space(50MB) as a consecutive file, splitting it into fixed-length slots; incoming response objects will also be treated blocks of data with the same length as the slots. We can fill slots until the whole file is run out of, then some displacement algorithm can be used to swap out the old cached objects. The latter approach will of course bing in internal fragmentation, but in my opinion is easier to implement and maintain than the first strategy. But when I enter Firefox's Cache directory, I find it (maybe) use a different method: a lot of varied-length files reside in that directory and all those files are filled with undisplayable characters. I don't but really want to know what mechanism that a commercial browser, e.g. Firefoix, employed to implement web cache. Regards.

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• MS Sql Full-text search vs. LIKE expression

  - by Marks

  Hi. I'm currently looking for a way to search a big database (500MB - 10GB or more on 10 tables) with a lot of different fields(nvarchars and bigints). Many of the fields, that should be searched are not in the same table. An example: A search for '5124 Peter' should return all items, that ... have an ID with 5124 in it, have 'Peter' in the title or description have item type id with 5124 in it created by a user named 'peter' or a user whose id has 5124 in it created by a user with '5124' or 'peter' in his street address. How should i do the search? I read that the full-text search of MS-Sql is a lot more performant than a query with the LIKE keyword and i think the syntax is more clear, but i think it cant search on bigint(id) values and i read it has performance problems with indexing and therefore slows down inserts to the DB. In my project there will be more inserting than reading, so this could be a matter. Thanks in advance, Marks

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• Composition vs Inheritance and GUI toolkits

  - by Anin Teger

  It's said that composition is preferred over inheritance. Every single open source GUI toolkit however uses inheritance for the drawn widgets (windows, labels, frames, buttons, etc). I checked Qt, wxWidgets, and GTK+. Is there an example of a GUI toolkit (written in any language) that uses composition instead of inheritance to separate the various widgets?

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• Storing Templates and Object-Oriented vs Relational Databases

  - by syrion

  I'm designing some custom blog software, and have run into a conundrum regarding database design. The software requires that there be multiple content types, each of which will require different entry forms and presentation templates. My initial instinct is to create these content types as objects, then serialize them and store them in the database as JSON or YAML, with the entry forms and templates as simple strings attached to the "contentTypes" table. This seems cumbersome, however. Are there established best practices for dealing with this design? Is this a use case where I should consider an object database? If I should be using an object database, which should I consider? I am currently working in Python and would prefer a capable Python library, but can move to Java if need be.

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• Performance question: Inverting an array of pointers in-place vs array of values

  - by Anders

  The background for asking this question is that I am solving a linearized equation system (Ax=b), where A is a matrix (typically of dimension less than 100x100) and x and b are vectors. I am using a direct method, meaning that I first invert A, then find the solution by x=A^(-1)b. This step is repated in an iterative process until convergence. The way I'm doing it now, using a matrix library (MTL4): For every iteration I copy all coeffiecients of A (values) in to the matrix object, then invert. This the easiest and safest option. Using an array of pointers instead: For my particular case, the coefficients of A happen to be updated between each iteration. These coefficients are stored in different variables (some are arrays, some are not). Would there be a potential for performance gain if I set up A as an array containing pointers to these coefficient variables, then inverting A in-place? The nice thing about the last option is that once I have set up the pointers in A before the first iteration, I would not need to copy any values between successive iterations. The values which are pointed to in A would automatically be updated between iterations. So the performance question boils down to this, as I see it: - The matrix inversion process takes roughly the same amount of time, assuming de-referencing of pointers is non-expensive. - The array of pointers does not need the extra memory for matrix A containing values. - The array of pointers option does not have to copy all NxN values of A between each iteration. - The values that are pointed to the array of pointers option are generally NOT ordered in memory. Hopefully, all values lie relatively close in memory, but *A[0][1] is generally not next to *A[0][0] etc. Any comments to this? Will the last remark affect performance negatively, thus weighing up for the positive performance effects?

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• static readonly field initializer vs static constructor initialization

  - by stackoverflowuser

  Below are 2 different ways to initialize static readonly fields. Is there a difference between the 2 approaches? If yes, when should one be preferred over the other? class A { private static readonly string connectionString = WebConfigurationManager.ConnectionStrings["SomeConnection"].ConnectionString; } class B { private static readonly string connectionString; static B() { connectionString = WebConfigurationManager.ConnectionStrings["SomeConnection"].ConnectionString; } } Thanks.

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• Rules Engine vs Expert System

  - by User1

  What is the difference between a rules engine and an expert system? Example1: Let's say that I have a program that determines the expiration date of a new driver's license. It takes inputs like visa expiration date, passport number, birthday, etc. It determines the expiration date of the driver's license from this input. It can even give an error if the input did not have enough valid identifications to allow a new driver's license. Example2: Let's say I am making an online version of the game Monopoly. I want the ability to change the rules of the game (say $400 for passing go or no one can buy properties until they land on the same property twice, etc). I have a module in the code to handle these rules. Are these both rules engines or are they expert systems? They both seem so similar. Is it just a synonym?

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• XElement vs Dcitionary

  - by user135498

  Hi All, I need advice. I have application that imports 10,000 rows containing name & address from a text file into XElements that are subsequently added to a synchronized queue. When the import is complete the app spawns worker threads that process the XElements by deenqueuing them, making a database call, inserting the database output into the request document and inserting the processed document into an output queue. When all requests have been processed the output queue is written to disk as an XML doc. I used XElements for the requests because I needed the flexibility to add fields to the request during processing. i.e. Depending on the job type the app might require that it add phone number, date of birth or email address to a request based on a name/address match against a public record database. My questions is; The XElements seems to use quite a bit of memory and I know there is a lot of parsing as the document makes its way through the processing methods. I’m considering replacing the XElements with a Dictionary object but I’m skeptical the gain will be worth the effort. In essence it will accomplish the same thing. Thoughts?

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• JTextField vs JComboBox behaviour in JTable

  - by Ash

  Okay, this is a hard one to explain but I'll try my best. I have a JTextField and a JComboBox in a JTable, whose getCellEditor method has been overriden as follows: public TableCellEditor getCellEditor( int row, int column ) { if ( column == 3 ) { // m_table is the JTable if ( m_table.getSelectedRowCount() == 1 ) { JComboBox choices = new JComboBox(); choices.setEditable( true ); choices.addItem( new String( "item 1" ) ); return new DefaultCellEditor( choices ); } return super.getCellEditor( row, column ); } Here are the behavioral differences (NOTE that from this point on, when I say JTextField or JComboBox, I mean the CELL in the JTable containing either component): When I click once on a JTextField, the cell is highlighted. Double clicking brings up the caret and I can input text. Whereas, with a JComboBox, single clicking brings up the caret to input text, as well as the combo drop down button. When I tab or use the arrow keys to navigate to a JTextField and then start typing, the characters I type automatically get entered into the cell. Whereas, when I navigate to a JComboBox the same way and then start typing, nothing happens apart from the combo drop down button appearing. None of the characters I type get entered unless I hit F2 first. So here's my question: What do I need to do have JComboBoxes behave exactly like JTextFields in the two instances described above? Please do not ask why I'm doing what I'm doing or suggest alternatives (it's the way it is and I need to do it this way) and yes, I've read the API for all components in question....the problem is, it's a swing API. Thanks in advance, Ash

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• MySQL query cache vs caching result-sets in the application layer

  - by GetFree

  I'm running a php/mysql-driven website with a lot of visits and I'm considering the possibility of caching result-sets in shared memory in order to reduce database load. However, right now MySQL's query cache is enabled and it seems to be doing a pretty good job since if I disable query caching, the use of CPU jumps to 100% immediately. Given that situation, I dont know if caching result-sets (or even the generated HTML code) locally in shared memory with PHP will result in any noticeable performace improvement. Does anyone out there have any experience on this matter? PS: Please avoid suggesting heavy-artillery solutions like memcached. Right now I'm looking for simple solutions that dont require too much time to implement, deploy and maintain.

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• long vs. short branches in version control

  - by Vincenzo

  I wonder whether anyone knows some research done with the question "What is good/bad in long/short branches in version control?" I'm specifically interested in academic researches performed in this field. My questions are: What problems (or conflicts) long branches may produce and how to deal with them How to split a big task onto smaller branches/sub-tasks How to coordinate the changes in multiple short branches, related to the same code Thanks in advance for links and suggestions!

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• lexers vs parsers

  - by Naveen

  Are lexers and parsers really that different in theory ? It seems fashionable to hate regular expressions: coding horror, another blog post. However, popular lexing based tools: pygments, geshi, or prettify, all use regular expressions. They seem to lex anything... When is lexing enough, when do you need EBNF ? Has anyone used the tokens produced by these lexers with bison or antlr parser generators?

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