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• What's wrong with debugging in Eclipse on Android?

  - by Sebastian Dwornik

  I've obviously been spoiled by Visual Studio, because although I'm just learning Android and the Eclipse environment, debugging apps in Eclipse is becoming a serious detriment to further development. For example, Eclipse will compile this divide by zero just fine: public class Lesson2Main extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate (savedInstanceState); int i = 1 / 0; TextView tv = new TextView (this); tv.setText ("Hello, Android!"); setContentView (tv); } } And then, when it executes it under the debugger, I will get a full screen of useless debug info, non of which actually points me to the specific line containing the error. The stackTrace is null within the exception ('e') info tree, and it simply states a message stating 'ArithmeticException'. (that's nice, how about you point me in the direction of where you found it!?) I've looked all over the screen and am baffled that this IDE can't get this right. Does developing with Eclipse resort everyone back to 1991 with printf() like logging at every interval then to track down bugs? Seriously. Is there a configuration or plug-in that I'm missing to help with this? I haven't tested this case with XCode, but if the iPhone dev. IDE handles this more like Visual Studio, then no wonder the Android marketplace has so few apps. I'm excited about Android, but it seems that Eclipse is getting in the way.

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• DSP - Filtering frequencies using DFT

  - by Trap

  I'm trying to implement a DFT-based 8-band equalizer for the sole purpose of learning. To prove that my DFT implementation works I fed an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. This method calculates the real and imaginary parts both N/2 + 1 samples in length. To attenuate a frequency I'm just doing: float atnFactor = 0.6; Re[k] *= atnFactor; Im[k] *= atnFactor; where 'k' is an index in the range 0 to N/2, but what I get after resynthesis is a slighty distorted signal, especially at low frequencies. The input signal sample rate is 44.1 khz and since I just want a 8-band equalizer I'm feeding the DFT 16 samples at a time so I have 8 frequency bins to play with. Can someone show me what I'm doing wrong? I tried to find info on this subject on the internet but couldn't find any. Thanks in advance.

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• Javascript for loop with variable

  - by Jascination

  I'm doing some simple javascript learning at the moment and I'm stuck on how to solve this problem. (the basic form comes from Code Academy). The task is to create 3 rabbit objects, each with a different adjective as an attribute. Then, print describeMyself() for each rabbit. Instead of repeating myself 3 times, I'd like to find a way to solve the problem with a for loop to make it more streamlined/challenging for myself. Here's what I tried: function Rabbit(adjective) { this.adjective = adjective; this.describeMyself = function() { console.log("I am a " + this.adjective + " rabbit"); }; } var rabbit1 = new Rabbit(fluffy); var rabbit2 = new Rabbit(happy); var rabbit3 = new Rabbit(sleepy); for (i=1; i<=3; i++){ ("rabbit"+i).describeMyself(); } Obviously, the ("rabbit"+i).describeMyself() is wrong. I want the loop to create "rabbit1", "rabbit2" and "rabbit3". What's the proper syntax here?

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• WPF DataBinding to standard CLR properties in code-behind

  - by nukefusion

  Hi everyone, Just learning WPF databinding and have a gap in my understanding. I've seen a few similar questions on StackOverflow, but I'm still struggling in determining what I have done wrong. I have a simple Person class with a Firstname and Surname property (standard CLR properties). I also have a standard CLR property on my Window class that exposes an instance of Person. I've then got some XAML, with two methods of binding. The first works, the second doesn't. Can anybody help me to understand why the second method fails? There's no binding error message in the Output log. <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" Title="Window1" Height="300" Width="300" DataContext="{Binding RelativeSource={RelativeSource Self}, Path=MyPerson}"> <StackPanel> <Label>My Person</Label> <WrapPanel> <Label>First Name:</Label> <Label Content="{Binding RelativeSource={RelativeSource AncestorType=Window, Mode=FindAncestor}, Path=MyPerson.FirstName}"></Label> </WrapPanel> <WrapPanel> <Label>Last Name:</Label> <Label Content="{Binding MyPerson.Surname}"></Label> </WrapPanel> </StackPanel> Edit: Ok, thanks so far. I've changed the second expression to: <Label Content="{Binding Surname}"></Label> I still can't get it to work though!

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• Properties vs. Fields: Need help grasping the uses of Properties over Fields.

  - by pghtech

  First off, I have read through a list of postings on this topic and I don't feel I have grasped properties because of what I had come to understand about encapsulation and field modifiers (private, public..ect). One of the main aspects of C# that I have come to learn is the importance of data protection within your code by the use of encapsulation. I 'thought' I understood that to be because of the ability of the use of the modifiers (private, public, internal, protected). However, after learning about properties I am sort of torn in understanding not only properties uses, but the overall importance/ability of data protection (what I understood as encapsulation) within C#. To be more specific, everything I have read when I got to properties in C# is that you should try to use them in place of fields when you can because of: 1) they allow you to change the data type when you can't when directly accessing the field directly. 2) they add a level of protection to data access However, from what I 'thought' I had come to know about the use of field modifiers did #2, it seemed to me that properties just generated additional code unless you had some reason to change the type (#1) - because you are (more or less) creating hidden methods to access fields as opposed to directly. Then there is the whole modifiers being able to be added to Properties which further complicates my understanding for the need of properties to access data. I have read a number of chapters from different writers on "properties" and none have really explained a good understanding of properties vs. fields vs. encapsulation (and good programming methods). Can someone explain: 1) why I would want to use properties instead of fields (especially when it appears I am just adding additional code 2) any tips on recognizing the use of properties and not seeing them as simply methods (with the exception of the get;set being apparent) when tracing other peoples code? 3) Any general rules of thumb when it comes to good programming methods in relation to when to use what? Thanks and sorry for the long post - I didn't want to just ask a question that has been asked 100x without explaining why I am asking it again.

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• Anything speaking against the bitnami.org Ruby/Rails/Redmine Stack?

  - by Pekka

  I am looking to set up a Redmine server on a Windows virtual machine on my local workstation. (Background in this related question.) I have zero knowledge of Ruby nor Rails, and while Redmine may be the opportunity to dip into those platforms somewhat, my first goal is to get it running as quickly and easily as possible. For that, I am eyeing the Bitnami Redmine Package. It promises point-and-click install, and a self-contained environment with everything you need. Apart from the learning factor, are there any serious limitations this method implies? Any serious cutdowns in customizability? I will be wanting to customize the template right away, for example, and install plugins. The package looks o.k. to me but before I install it, I was curious to know whether anybody would advise against it and why. Edit: The first impression is great. From 0 to a working Redmine installation in twelve minutes! Wow.

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• What does O(log n) mean exactly?

  - by Andreas Grech

  I am currently learning about Big O Notation running times and amortized times. I understand the notion of O(n) linear time, meaning that the size of the input affects the growth of the algorithm proportionally...and the same goes for, for example, quadratic time O(n2) etc..even algorithms, such as permutation generators, with O(n!) times, that grow by factorials. For example, the following function is O(n) because the algorithm grows in proportion to its input n: f(int n) { int i; for (i = 0; i < n; ++i) printf("%d", i); } Similarly, if there was a nested loop, the time would be O(n2). But what exactly is O(log n)? For example, what does it mean to say that the height of a complete binary tree is O(log n)? I do know (maybe not in great detail) what Logarithm is, in the sense that: log10 100 = 2, but I cannot understand how to identify a function with a logarithmic time.

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• Only last row in method execute (Objective-C)

  - by Emil

  First I want to apologize for my lack of knowledge in programming in general. I am in the way of learning and have discovered that this site is a huge compliment for me of doing so. I have created a program with three UITextField(thePlace,theVerb,theOutput) and two UITextView where one of the textviews(theOutput) take the text from the other textview(theTemplate) and replaces some strings with the text entered in the textfields. When I click a button it triggers the method createStory that is listed below. This works fine with one exception. The text in the output only changes the string 'number' to the text in the textfield. However if I change the order in the method to replace 'place','number','verb' only the verb is changed, not the number. Im sure this is some sort of easy fix but I can't find it. Can some of you help me with my troubleshooting? - (IBAction)createStory:(id)sender { theOutput.text=[theTemplate.text stringByReplacingOccurrencesOfString:@"<place>" withString:thePlace.text]; theOutput.text=[theTemplate.text stringByReplacingOccurrencesOfString:@"<verb>" withString:theVerb.text]; theOutput.text=[theTemplate.text stringByReplacingOccurrencesOfString:@"<number>" withString:theNumber.text]; } Many thanks // Emil

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• How do I pass a lot of parameters to views in Dango?

  - by Mark

  I'm very new to Django and I'm trying to build an application to present my data in tables and charts. Till now my learning process went very smooth, but now I'm a bit stuck. My pageview retrieves large amounts of data from a database and puts it in the context. The template then generates different html-tables. So far so good. Now I want to add different charts to the template. I manage to do this by defining <img src=".../> tags. The Matplotlib chart is generate in my chartview an returned via: response=HttpResponse(content_type='image/png') canvas.print_png(response) return response Now I have different questions: the data is retrieved twice from the database. Once in the pageview to render the tables, and again in the chartview for making the charts. What is the best way to pass the data, already in the context of the page to the chartview? I need a lot of charts, each with different datasets. I could make a chartview for each chart, but probably there is a better way. How do I pass the different dataset names to the chartview? Some charts have 20 datasets, so I don't think that passing these dataset parameters via the url (like: <imgm src="chart/dataset1/dataset2/.../dataset20/chart.png />) is the right way. Any advice?

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• How to compile ocaml to native code

  - by Indra Ginanjar

  i'm really interested learning ocaml, it fast (they said it could be compiled to native code) and it's functional. So i tried to code something easy like enabling mysql event scheduler. #load "unix.cma";; #directory "+mysql";; #load "mysql.cma";; let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; It work fine on ocaml interpreter, but when i was trying to compile it to native (i'm using ubuntu karmic), neither of these command worked ocamlopt -o mysqleventon mysqleventon.ml unix.cmxa mysql.cmxa ocamlopt -o mysqleventon mysqleventon.ml unix.cma mysql.cma i also tried ocamlc -c mysqleventon.ml unix.cma mysql.cma all of them resulting same message File "mysqleventon.ml", line 1, characters 0-1: Error: Syntax error Then i tried to remove the "# load", so the code goes like this let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; The ocamlopt resulting message File "mysqleventon.ml", line 1, characters 9-28: Error: Unbound value Mysql.quick_connect I hope someone could tell me, where did i'm doing wrong.

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• Beyond core java

  - by Paul

  Coming to the end of the first year of my CS degree, we've done some Java but just the core stuff; manipulating strings and arrays, inheritance, implementing logic etc. I visit this website daily and I see so much stuff that is beyond me; using frameworks; managing databases etc. It makes me feel like I've just learned the syntax of Java, and there is so much more to do with it. My question is though, how do I get there? I don't think I'm advanced enough to join an open source project, which seems to be suggested often (though I'd love to) and I've looked at other similar questions on here (like this one) but even then I don't think that'd work for me.. firstly, could somebody try give me some commonly used frameworks etc and how and what they are used for? Where would be a good place to start? How did you get started in using the things you do? Or perhaps you think I'm going down the wrong route. Should I learn another language, and just wait until the moment occurs where it's clear what I should be doing? I'm only in the first year of my degree, so far we've lightly covered Haskell and Java, and I've done a little HTML and CSS in my free time. I know that next year we cover python, so perhaps I should just wait till then and see if I prefer that? I feel like I also risk learning something in depth and then never using it... I suppose I'm also asking for personal experiences; was there a point where you felt you'd exceeded the basic grasp of a language (does not necessarily have to be Java related) and reach a more "advanced" level? I guess I'll put subjective tag on this, but really I just want to know how to get beyond the basic understanding of a language.

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• Class Plugins in PHP?

  - by YuriKolovsky

  i just got some more questions while learning PHP, does php implement any built in plugin system? so the plugin would be able to change the behavior of the core component. for example something like this works: include 'core.class.php'; include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; where core.class.php contains class core { public function coremethod1(){ echo 'coremethod1'; } public function coremethod2(){ echo 'coremethod2'; } } plugin1.class.php contains class plugin1 extends core { public function coremethod1(){ echo 'plugin1method1'; } } plugin2.class.php contains class plugin2 extends plugin1 { public function coremethod2(){ echo 'plugin2method2'; } } This would be ideal, if not for the problem that now the plugins are dependable on each other, and removing one of the plugins: include 'core.class.php'; //include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; breaks the whole thing... are there any proper methods to doing this? if there are not, them i might consider moving to a different langauge that supports this... thanks for any help.

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• C++ boost.asio server and client connection undersanding

  - by Edgar Buchvalov

  i started learning boost.asio and i have some problems with undersanding tcp connections. There is example from official boost site: #include <ctime> #include <iostream> #include <string> #include <boost/asio.hpp> using boost::asio::ip::tcp; std::string make_daytime_string() { using namespace std; // For time_t, time and ctime; time_t now = time(0); return ctime(&now); } int main() { try { boost::asio::io_service io_service; tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), 13)); for (;;) { tcp::socket socket(io_service); acceptor.accept(socket); std::string message = make_daytime_string(); boost::system::error_code ignored_error; boost::asio::write(socket, boost::asio::buffer(message), boost::asio::transfer_all(), ignored_error); } } catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; } there is question, why if i want to connet to this server via client i have t write: boost::asio::io_service io_service; tcp::resolver resolver(io_service); tcp::resolver::query query(host_ip, "daytime"); //why daytime? tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); tcp::resolver::iterator end; why daytime?, what it meant and where it is inicialized in server, or i just doesn't missed somefing? there is full client code : www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/tutorial/tutdaytime1.html thanks for explanation in advance

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• Handling XMLHttpRequest to call external application

  - by Ian

  I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls. The situation: The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status. The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database. In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem. What I think I want: Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available). C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding. How do I do this? Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents? Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces? Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch? Thanks for any help! I am really having trouble learning about the server side of these technologies.

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• Order in many to many relation in Django model

  - by Pietro Speroni

  I am writing a small website to store the papers I have written. The relation papers<- author is important, but the order of the name of the authors (which one is First Author, which one is second order, and so on) is also important. I am just learning Django so I don't know much. In any case so far I have done: from django.db import models class author(models.Model): Name = models.CharField(max_length=60) URLField = models.URLField(verify_exists=True, null=True, blank=True) def __unicode__(self): return self.Name class topic(models.Model): TopicName = models.CharField(max_length=60) def __unicode__(self): return self.TopicName class publication(models.Model): Title = models.CharField(max_length=100) Authors = models.ManyToManyField(author, null=True, blank=True) Content = models.TextField() Notes = models.TextField(blank=True) Abstract = models.TextField(blank=True) pub_date = models.DateField('date published') TimeInsertion = models.DateTimeField(auto_now=True) URLField = models.URLField(verify_exists=True,null=True, blank=True) Topic = models.ManyToManyField(topic, null=True, blank=True) def __unicode__(self): return self.Title This work fine in the sense that I now can define who the authors are. But I cannot order them. How should I do that? Of course I could add a series of relations: first author, second author,... but it would be ugly, and would not be flexible. Any better idea? Thanks

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• What's next for all of these Microsoft "overlapping" and "enhanced" products ?

  - by pointlesspolitics

  Recently I attended a road show, organised by MS Gold Partner company in the UK. The products discussed were: SharePoint server (2010 and 2007), Exchange server, Office Communication Server 2007, Exchange hosted services Office Live meeting, Office Communicator, System Center Configuration Manager and Operation Manager, VMware, Windows 7 etc. As Microsoft claims the enhancement in the each product against higher version, I felt that clients are not much interested in all these details. For example Office Communicator, surely they have improved a lot the product and first site all said 'WOW' great product, but nobody wish to pay money for all these extra features. Some argued, they are bogged down by all these increased number of menus. They don't need soft call feature included with mobile call. It apply for all other products as well such as MS office (next what 2 ribbons ?), windows OS and many more. Indeed there must be good features in all these products, but is it worth to spend money and time to update the older system ? Also sometimes these feature will decrease the productivity instead increase it. *So do you think what ever enhancement MS is doing in the products is only for selling purpose, not a real use ?? and I think also keep the developer busy learning the new tools and features. * I am sure some some people here will argue that some people need this sort of features. But I am not talking about NASA or MI5 guys. I am talking of usual businesses and joe public. Any ideas welcome.

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• Applying for .net jobs as a "self learner"

  - by DeanMc

  Hi All, I have recently started applying for .Net jobs. I currently work in a sales role with a large telco. I found out quite late that I like programming and as such bought my house and made commitments that mean college is not an option. What I would like to know is, is it harder to get a junior job as a self learner? I have gotten a few enquiries regarding my C.V but nothing concrete yet. I try to be involved in projects as I get the chance and tend to put up any worthwhile projects as I develop them. Some examples of my work are: A Xaml lexer and parser: http://www.xlight.mendhak.com A font obfuscation tool: http://www.silverlightforums.com/showthread.php?1516-Font-Obsfucation-Tool-ALPHA A tagger for m4a: http://projectaudiophile.codeplex.com/SourceControl/list/changesets I, of course think that these are great examples of my work but that is my opinion based on self learning. The other query is how much should I actually know? I've never used linked lists but I know that strings are immutable and I understand what that means. I am only touching on T-SQL but I understand things like how properties function in IL (as two standard methods :) ). I suppose I understand a lot of concepts but specific features need some looking up to implement as I may not know the syntax off the top of my head.

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• Should frontend and backend handled by different controllers?

  - by DR

  In my previous learning projects I always used a single controller, but know I wonder if that is good practice or even always possible. In all RESTful Rails tutorials the controllers have a show, an edit and an index view. If an authorized user is logged on, the edit view becomes available and the index view shows additional data manipulation controls, like a delete button or a link to the edit view. Now I have a Rails application which falls exactly into this pattern, but the index view is not reusable: The normal user sees a flashy index page with lots of pictures, complex layout, no Javascript requirement, ... The Admin user index has a completly different minimalistic design, jQuery table and lots of additional data, ... Now I'm not sure how to handle this case. I can think of the following: Single controller, single view: The view is split into two large blocks/partials using an if statement. Single controller, two views: index and index_admin. Two different controllers: BookController and BookAdminController None of this solutions seems perfect, but for now I'm inclined to use the 3rd option. What's the preferred way to do this?

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• How do I apply a "template" or "skeleton" of code in C# here?

  - by Scott Stafford

  In my business layer, I need many, many methods that follow the pattern: public BusinessClass PropertyName { get { if (this.m_LocallyCachedValue == null) { if (this.Record == null) { this.m_LocallyCachedValue = new BusinessClass( this.Database, this.PropertyId); } else { this.m_LocallyCachedValue = new BusinessClass( this.Database, this.Record.ForeignKeyName); } } return this.m_LocallyCachedValue; } } I am still learning C#, and I'm trying to figure out the best way to write this pattern once and add methods to each business layer class that follow this pattern with the proper types and variable names substituted. BusinessClass is a typename that must be substituted, and PropertyName, PropertyId, ForeignKeyName, and m_LocallyCachedValue are all variables that should be substituted for. Are attributes usable here? Do I need reflection? How do I write the skeleton I provided in one place and then just write a line or two containing the substitution parameters and get the pattern to propagate itself? EDIT: Modified my misleading title -- I am hoping to find a solution that doesn't involve code generation or copy/paste techniques, and rather to be able to write the skeleton of the code once in a base class in some form and have it be "instantiated" into lots of subclasses as the accessor for various properties. EDIT: Here is my solution, as suggested but left unimplemented by the chosen answerer. // I'll write many of these... public BusinessClass PropertyName { get { return GetSingleRelation(ref this.m_LocallyCachedValue, this.PropertyId, "ForeignKeyName"); } } // That all call this. public TBusinessClass GetSingleRelation<TBusinessClass>( ref TBusinessClass cachedField, int fieldId, string contextFieldName) { if (cachedField == null) { if (this.Record == null) { ConstructorInfo ci = typeof(TBusinessClass).GetConstructor( new Type[] { this.Database.GetType(), typeof(int) }); cachedField = (TBusinessClass)ci.Invoke( new object[] { this.Database, fieldId }); } else { var obj = this.Record.GetType().GetProperty(objName).GetValue( this.Record, null); ConstructorInfo ci = typeof(TBusinessClass).GetConstructor( new Type[] { this.Database.GetType(), obj.GetType()}); cachedField = (TBusinessClass)ci.Invoke( new object[] { this.Database, obj }); } } return cachedField; }

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• Parse Facebook API data using loop for getting fan page ID#s?

  - by Brandon Lee

  I've been learning how to parse json data returned from the facebook-api. I've figured out how to fetch fan pages from a specific profile id and want to parse them using a loop! Heres the code and example I have below: This is the data I get back from the facebook-api Array ( [0] => Array ( [page_id] => XXXXXX60828 ) [1] => Array ( [page_id] => XXXXXX0750 ) [2] => Array ( [page_id] => XXXXXX91225 ) [3] => Array ( [page_id] => XXXXXX1960343 ) [4] => Array ( [page_id] => XXXXXX60863 ) [5] => Array ( [page_id] => XXXXXX8582 ) ) I need to be able to put this data in a loop and extract the page_id#s out... still getting familiar with json and am having issues figuring this out? How can I get this in a loop using for each and strip out the page id#s?

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• How/when to hire new programmers, and how to integrate them?

  - by Shaul

  Hiring new programmers, especially in a small company, can often present a Catch-22 situation. We have too much work to do, so we need to hire new programmers. But we can't hire new programmers now, because they will need mentoring and several months of learning curve in your industry/product/environment before they're useful, and none of the programmers has time to be a mentor to a new programmer, because they're all completely swamped with the current work load. That may be a slightly frivolous way of describing the situation, but nevertheless, it's difficult for a small company on a tight budget to justify hiring someone who is not only going to be unproductive for a long time, but will also take away from the performance of the current programmers. How have you dealt with this kind of situation? When is the best time to hire someone? What are the best tasks to assign to a new team member so that they can learn their way around your code base and start getting their hands dirty as quickly as possible? How do you get the new guy useful without bogging your existing programmers down in too much mentoring? Any comments & suggestions you have are much appreciated!

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• Perceptron Classification and Model Training

  - by jake pinedo

  I'm having an issue with understanding how the Perceptron algorithm works and implementing it. cLabel = 0 #class label: corresponds directly with featureVectors and tweets for m in range(miters): for point in featureVectors: margin = answers[cLabel] * self.dot_product(point, w) if margin <= 0: modifier = float(lrate) * float(answers[cLabel]) modifiedPoint = point for x in modifiedPoint: if x != 0: x *= modifier newWeight = [modifiedPoint[i] + w[i] for i in range(len(w))] w = newWeight self._learnedWeight = w This is what I've implemented so far, where I have a list of class labels in answers and a learning rate (lrate) and a list of feature vectors. I run it for the numbers of iterations in miter and then get the final weight at the end. However, I'm not sure what to do with this weight. I've trained the perceptron and now I have to classify a set of tweets, but I don't know how to do that. EDIT: Specifically, what I do in my classify method is I go through and create a feature vector for the data I'm given, which isn't a problem at all, and then I take the self._learnedWeight that I get from the earlier training code and compute the dot-product of the vector and the weight. My weight and feature vectors include a bias in the 0th term of the list so I'm including that. I then check to see if the dotproduct is less than or equal to 0: if so, then I classify it as -1. Otherwise, it's 1. However, this doesn't seem to be working correctly.

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• What ORM for .NET should I use?

  - by eKek0

  I'm relatively new to .NET and have being using Linq2Sql for a almost a year, but it lacks some of the features I'm looking for now. I'm going to start a new project in which I want to use an ORM with the following characteristics: It has to be very productive, I don't want to be dealing with the access layer to save or retrieve objects from or to the database, but it should allows me to easily tweak any object before actually commit it to the database; also it should allows me to work easily with a changing database schema It should allows me to extend the objects mapped from the database, for example to add virtual attributes to them (virtual columns to a table) It has to be (at least almost) database agnostic, it should allows me to work with different databases in a transparent way It has to have not so much configuration or must be based on conventions to make it work It should allows me to work with Linq So, do you know any ORM that I could use? Thank you for your help. EDIT I know that an option is to use NHibernate. This appears as the facto standard for enterprise level applications, but also it seems that is not very productive because its deep learning curve. In other way, I have read in some other post here in SO that it doesn't integrate well with Linq. Is all of that true?

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• Boost::thread mutex issue: Try to lock, access violation

  - by user1419305

  I am currently learning how to multithread with c++, and for that im using boost::thread. I'm using it for a simple gameengine, running three threads. Two of the threads are reading and writing to the same variables, which are stored inside something i call PrimitiveObjects, basicly balls, plates, boxes etc. But i cant really get it to work, i think the problem is that the two threads are trying to access the same memorylocation at the same time, i have tried to avoid this using mutex locks, but for now im having no luck, this works some times, but if i spam it, i end up with this exception: First-chance exception at 0x00cbfef9 in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. Unhandled exception at 0x77d315de in TTTTT.exe: 0xC0000005: Access violation reading location 0xdddddded. These are the functions inside the object that im using for this, and the debugger is also blaming them for the exception. void PrimitiveObj::setPos(glm::vec3 in){ boost::mutex mDisposingMutex; boost::try_mutex::scoped_try_lock lock(mDisposingMutex); if ( lock) { position = in; boost::try_mutex::scoped_try_lock unlock(mDisposingMutex); } } glm::vec3 PrimitiveObj::getPos(){ boost::mutex myMutex; boost::try_mutex::scoped_try_lock lock(myMutex); if ( lock) { glm::vec3 curPos = position; boost::try_mutex::scoped_try_lock unlock(myMutex); return curPos; } return glm::vec3(0,0,0); } Any ideas?

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• What is optimal hardware configuration for heavy load LAMP application

  - by Piotr Kochanski

  I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

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