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• Error in Ordinary Differential Equation representation

  - by Priya M

  UPDATE I am trying to find the Lyapunov Exponents given in link LE. I am trying to figure it out and understand it by taking the following eqs for my case. These are a set of ordinary differential equations (these are just for testing how to work with cos and sin as ODE) f(1)=ALPHA*(y-x); f(2)=x*(R-z)-y; f(3) = 10*cos(x); and x=X(1); y=X(2); cos(y)=X(3); f1 means dx/dt;f2 dy/dt and f3 in this case would be -10sinx. However,when expressing as x=X(1);y=X(2);i am unsure how to express for cos.This is just a trial example i was doing so as to know how to work with equations where we have a cos,sin etc terms as a function of another variable. When using ode45 to solve these Eqs [T,Res]=sol(3,@test_eq,@ode45,0,0.01,20,[7 2 100 ],10); it throws the following error ??? Attempted to access (2); index must be a positive integer or logical. Error in ==> Eq at 19 x=X(1); y=X(2); cos(x)=X(3); Is my representation x=X(1); y=X(2); cos(y)=X(3); alright? How to resolve the error? Thank you

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• Prime Numbers in C?

  - by Ali Azam Rana

  FIRST PROGRAM #include<stdio.h> void main() { int n,c; printf("enter a numb"); scanf("%i",n); for(c=2;c<=n;c++) { if(n%c==0) break; } if(c==n) printf("\nprime\n"); else printf("\nnot prime\n"); getchar(); } SECOND PROGRAM #include <stdio.h> int main() { printf("Enter a Number\n"); int in,loop,rem,chk; scanf("%d",&in); for (loop = 1; loop <=in; loop++) { rem = in % loop; if(rem == 0) chk = chk +1; } if (chk == 2) printf("\nPRIME NUM ENTERED\n"); else printf("\nNUM ENTERED NOT PRIME\n"); getchar(); } the 2nd program works other was the one my friend wrote the program looks fine but on checking it by stepping into we found that the if condition in first program is coming true under every input so whats the logical error here please help me found out......

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• WPF and LINQ/SQL - how and where to keep track of changes?

  - by Groky

  I have a WPF application built using the MVVM pattern: My Models come from LINQ to SQL. I use the Repository Pattern to abstract away the DataContext. My ViewModels have a reference to a Model. Setting a property on the ViewModel causes that value to be written through to the Model. As you can see, my data is stored in my Model, and changes are therefore tracked by my DataContext. However, in this question I read: The guidelines from the MSDN documentation on the DataContext class are what I would recommend following: In general, a DataContext instance is designed to last for one "unit of work" however your application defines that term. A DataContext is lightweight and is not expensive to create. A typical LINQ to SQL application creates DataContext instances at method scope or as a member of short-lived classes that represent a logical set of related database operations. How do you track your changes? In your DataContext? In your ViewModel? Elsewhere?

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• How difficult is it for an old-school programmer to pick up an FPGA kit and make something useful wi

  - by JUST MY correct OPINION

  I'm an old, old, old coder. (How old? I've used paper tape in anger.) I've programmed in a lot of languages and under a lot of paradigms (spaghetti, structured, object-oriented, functional and a smattering of logical). I'm getting bored. FPGAs look interesting to me. I have the crazy notion of resurrecting some of the ancient hardware I worked on in the days using FPGAs. I know this can be done because I've seen PDP-10 and PDP-11 implementations in FPGAs. I'd like to do the same for a few machines that are perhaps not as popular as those two, however. While I am an old, old coder, what I am not is an electronics or computer systems engineer. I'll be learning from scratch if I go down this path. My question, therefore, is two-fold: How difficult will it be for this old dinosaur to pick up and learn FPGAs to the point that interesting (not necessarily practical -- more from a hobbyist perspective) projects can be made? What should I start with learning-wise to go down this path? I know where to get FPGA kits, but I haven't found anything like "FPGAs for Complete Dinosaurs" yet anywhere out there.

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• What's the correct place to share application logic in CakePHP?

  - by Pichan

  I guess simple answer to the question would be a component. Although I agree, I feel weird having to write a component for something so specific. For example, let's say I have a table of users. When a user is created, it should form a chain reaction of events, initiating different kinds of data related to the user all around the database. I figured it would be best to avoid directly manipulating the database from different controllers and instead pack all that neatly in a method. However since some logic needs to be accesed separately, I really can't have the whole package in a single method. Instead I thought it would be logical to break it up to smaller pieces(like $userModelOrController->createNew() and $candyStorageModelOrController->createNew()) that only interact with their respective database table. Now, if the logic is put to the model, it works great until I need to use other models. Of course it's possible, but when compared to loading models in a controller, it's not that simple. It's like a Cake developer telling me "Sure, it's possible if you want to do it that way but that's not how I would do it". Then, if the logic is put to the controller, I can access other models really easy through $this->loadModel(), but that brings me back to the previously explained situation since I need to be able to continue the chain reaction indefinitely. Accessing other controllers from a controller is possible, but again there doesn't seem to be any direct way of doing so, so I'm guessing I'm still not doing it right. By using a component this problem could be solved easily, since components are available to every controller I want. But like I wrote at the beginning, it feels awkward to create a component specifically for this one task. To me, components seem more like packages of extra functionality(like the core components) and not something to share controller-specific logic. Since I'm new to this whole MVC thing, I could've completely misunderstood the concept. Once again, I would be thankful if someone pointed me to the right direction :)

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• Is this overly clever or unsafe?

  - by Liberalkid

  I was working on some code recently and decided to work on my operator overloading in c++, because I've never really implemented it before. So I overloaded the comparison operators for my matrix class using a compare function that returned 0 if LHS was less than RHS, 1 if LHS was greater than RHS and 2 if they were equal. Then I exploited the properties of logical not in c++ on integers, to get all of my compares in one line: inline bool Matrix::operator<(Matrix &RHS){ return ! (compare(*this,RHS)); } inline bool Matrix::operator>(Matrix &RHS){ return ! (compare((*this),RHS)-1); } inline bool Matrix::operator>=(Matrix &RHS){ return compare((*this),RHS); } inline bool Matrix::operator<=(Matrix &RHS){ return compare((*this),RHS)-1; } inline bool Matrix::operator!=(Matrix &RHS){ return compare((*this),RHS)-2; } inline bool Matrix::operator==(Matrix &RHS){ return !(compare((*this),RHS)-2); } Obviously I should be passing RHS as a const, I'm just probably not going to use this matrix class again and I didn't feel like writing another function that wasn't a reference to get the array index values solely for the comparator operation.

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• Enterprise integration of disparate systems

  - by Chris Latta

  We're about to embark on a fairly large integration effort to kill off a bunch of Access and Sql Server databases and get everything into one coherent enterprise system. There are also a number of other systems (accounting, CRM, payroll, MS Exchange) that hold critical data that we need to integrate (use for data validation in other systems), report on and otherwise expose. It is likely that some of these systems will change in the next few years, so we need to isolate our systems to be ready for change. Ideally we would be able to expose our forms in a consistent manner across as many of our our systems as possible without having to re-develop them for each system. We are currently targeting SharePoint (2007 and soon 2010), Office (2007 and soon 2010 - Word, Excel, PowerPoint and Outlook), Reporting Services, .Net console applications, .Net Windows applications, shell extensions, and with the possibility of exposing some functionality on mobile devices (BlackBerries currently, maybe iPhones later) and via our website. We're moving development to Visual Studio 2010 (from 2005) ahead of migrating to SharePoint 2010 and Office 2010. Given that most of our development is presently targeted to the .Net framework (mostly in C#) it seems logical to stick with this unless there is some compelling reason to switch frameworks/platform for some aspects. We're thinking of your standard Database-Data Integration layer-Business Objects Layer-Web Services (or REST) layer-Client Application plus doing our own client application with WPF (or something else?) forms that can also be exposed in the MS systems (SharePoint, Office, Windows). So, we don't want much, just everything :) Basically we need to isolate ourselves from database and systems changes, create an API that can be used throughout our systems and then make this functionality available in our client applications. I'm very keen to get pointers from anyone who has tips on how to pull this off. Should we look at the Enterprise Library as a place to start? Is REST with ASP.Net MVC2 a better solution than Web Services for a system like this? Will WPF deliver forms re-use or is there something better?

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• How do i return a template class from a template function?

  - by LoudNPossiblyRight

  It looks logical but for some reason when i uncomment the last cout line, this code does not compile. How do i return a template class? What do i have to do to this code to make it work? #include<iostream> using namespace std; template <int x> class someclass{ public: int size; int intarr[x]; someclass():size(x){} }; template<int x, int y> int somefunc(someclass<x> A, someclass<y> B){ return ( A.size > B.size ? A.size : B.size); } template<int x, int y, int z> someclass<x> anotherfunc(someclass<y> A, someclass<z> B){ return ( A.size > B.size ? A : B); } int main(){ someclass<5> A; someclass<10> B; cout << "SIZE = " << somefunc(A,B) << endl; //cout << "SIZE = " << (anotherfunc(A,B)).size << endl; //THIS DOES NOT COMPILE return 0; }

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• MouseListener fired without checking JCheckBox

  - by Morinar

  This one is pretty crazy: I've got an AppSight recording (for those not familiar, it's a recording of what they did including keyboard/mouse input + network traffic, etc) of a customer reproducing a bug. Basically, we've got a series of items listed on the screen with JCheckBox-es down the left side. We've got a MouseListener set for the JPanel that looks something like this: private MouseAdapter createMouseListener() { return new MouseAdapter(){ public void mousePressed( MouseEvent e ) { if( e.getComponent() instanceof JCheckBox ) { // Do stuff } } }; } Based on the recording, it appears very strongly that they click just above one of the checkboxes. After that, it's my belief that this listener fired and the "Do stuff" block happened. However, it did NOT check the box. The user then saw that the box was unchecked, so they clicked on it. This caused the "Do stuff" block to fire again, thus undoing what it had done the first time. This time, the box was checked. Therefore, the user thinks that the box is checked, and it looks like it is, but our client thinks that the box is unchecked as it was clicked twice. Is this possible at all? For the life of me, I can't reproduce it or see how it could be possible, but based on the recording and the data the client sent to the server, I can't see any other logical explanation. Any help, thoughts, and or ideas would be much appreciated.

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• ctrl+click or shift+click not always firing the onclick event

  - by Erik

  Hi, I recently discovered that different browsers handle the onclick event differently when the control of shift key is pressed. Same thing for following links with the middle mouse button. <a href="http://www.example.com/" onclick="alert('onclick');">go to example.com</a> Onclick browser support table Mouse Keyboard Chrome Firefox Safari Opera IE5.5 IE6 IE7 IE8 IE9 Left None yes yes yes yes yes yes yes yes yes Left Ctrl yes yes yes yes ? yes no no ? Left Shift yes yes yes yes ? yes yes yes ? Middle None yes no yes no ? N/A no no ? Can someone please fill in the question marks for me? Also; I'm wondering if the behaviour differs for each version of Chrome, Firefox, Safari and Opera. Finding a logical pattern in this behaviour would be even nicer, but I don't think there is :). Thanks a lot.

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• Not getting key value from Identity column back after inserting new row with SubSonic ActiveRecord

  - by mikedevenney

  I'm sure I'm missing the obvious answer here, but could use a hand. I'm new to SubSonic and using version 3. I've got myself to the point of being able to query and insert, but I'm stuck with how I would get the value of the identity column back after my insert. I saw another post that mentioned Linq Templates. I'm not using those (at least I don't think I am...?) TIA ... UPDATE ... So I've been debugging through my code watching how the SubSonic code works and I found where the indentity column is being ignored. I use int as the datatype for my ID columns in the database and set them as identity. Since int is a non-nullable data type in c# the logical test in the Add method (public void Add(IDataProvider provider)) that checks if there is a value in the key column by doing a (key==null) could be the issue. The code that gets the new value for the identity field is in the 'true path', since an int can't be null and I use ints as my identity column data types this test will never pass. The ID field for my object has a 0 in it that I didn't put there. I assume it's set during the initialization of the object. Am I off base here? Is the answer to change my data types in the database? Another question (more a curiosity). I noticed that some of the properties in the generated classes are declared with a ? after the datatype. I'm not familiar with this declaration construct... what gives? There are some declared as an int (non key fields) and others that are declared as int? (key fields). Does this have something to do with how they're treated at initialization? Any help is appreciated! --BUMP--

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• Should a C++ constructor do real work?

  - by Wade Williams

  I'm strugging with some advice I have in the back of my mind but for which I can't remember the reasoning. I seem to remember at some point reading some advice (can't remember the source) that C++ constructors should not do real work. Rather, they should initialize variables only. The advice when on to explain that real work should be done in some sort of init() method, to be called separately after the instance was created. The situation is I have a class that represents a hardware device. It makes logical sense to me for the constructor to call the routines that query the device in order to build up the instance variables that describe the device. In other words, once new instantiates the object, the developer receives an object which is ready to be used, no separate call to object-init() required. Is there a good reason why constructors shouldn't do real work? Obviously it could slow allocation time, but that wouldn't be any different if calling a separate method immediately after allocation. Just trying to figure out what gotchas I not currently considering that might have lead to such advice.

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• Click behaviour - Difference in IE and FF ?!

  - by OlliD

  Hey folks, i just came to the conclusion that a project i am currently working on might have a "logical" error in functionality. Currently I'am using server technology with PHP/MySQL and JQuery. Within the page there's a normal link reference with tag <a href="contentpage?page=xxx">next step</a> The pain point now seems to be the given jquery click event on the same element. The intension was to save the (current) content of the page (- form elements) via another php script using the php session command. For any reason, IE can handle the click event of Jquery right before executing the standard html command, that reloads the current page again with the new page parameter. By using FF the behaviour is different. I assume, that FF first execute the html command and afterwards execute the javascript code which handles the click event. Therefore the resultset here is wrong respectivly empty. My question now is whether you made the same experience and how you handled / wordarrounded this problem. I'd be thankful fur any of your tips or further feedback. Maybe you also have a solution on how to rethink about the current architecture. Regards, Oliver

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• Out-of-memory algorithms for addressing large arrays

  - by reve_etrange

  I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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• Sencha 2 : Sync models with hasMany associations in LocalStorage

  - by Alytrem

  After hours and hours trying to do this, I need your help. I have to models : Project and Task. A project hasMany tasks and a task belong to a project. Everyting works well if you don't use a store to save these models. I want to save both tasks and projects in two stores (TaskStore and ProjectStore). These stores use a LocalStorage proxy. I tried many things, and the most logical is : Ext.define('MyApp.model.Task', { extend: 'Ext.data.Model', config: { fields: [ { name: 'name', type: 'string' }, { dateFormat: 'd/m/Y g:i', name: 'start', type: 'date' }, { dateFormat: 'd/m/Y g:i', name: 'end', type: 'date' }, { name: 'status', type: 'string' } ], belongsTo: { model: 'MyApp.model.Project' } } }); Ext.define('MyApp.model.Project', { extend: 'Ext.data.Model', alias: 'model.Project', config: { hasMany: { associationKey: 'tasks', model: 'MyApp.model.Task', autoLoad: true, foreignKey: 'project_id', name: 'tasks', store: {storeId: "TaskStore"} }, fields: [ { name: 'name', type: 'string' }, { dateFormat: 'd/m/Y', name: 'start', type: 'date' }, { dateFormat: 'd/m/Y', name: 'end', type: 'date' } ] } }); This is my "main" : var project = Ext.create("MyApp.model.Project", {name: "mojo", start: "17/03/2011", end: "17/03/2012", status: "termine"}); var task = Ext.create("MyApp.model.Task", {name: "todo", start: "17/03/2011 10:00", end: "17/03/2012 19:00", status: "termine"}); project.tasks().add(task); Ext.getStore("ProjectStore").add(project); The project is added to the store, but task is not. Why ?!

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• How to reload a tableView i.e call the viewDidLoad method if a condition is met

  - by Kquane Ingram

  The problem is this i need a way to basically erase all the entry data a user placed into my arrays if a condition is met. Im new to Objective-C and iOS programming, but i believed the solution might be in calling the viewDidLoad method, thus it would virtually refresh the applications with the values of the array reset to default. If there is any other logical way of doing this i would appreciate the help. In short i need to refresh the arrays as they were when the application first launched and the user did not select anything. This is the part where i need it to refresh. if ([gradeRecieved objectAtIndex:i]==nil) { break; // if this condition is met the program must begin anew. Edit* I need to recall the - (void)viewDidLoad method here is more of the code. -(IBAction)button:(id)sender{ int i = 0; int sum = 0; int gradeEarned; int creditHours = 3; for ( i=0;i<8 ; i++) { if ([[points objectAtIndex:i] tag]==GradeA.intValue) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeA]; } if ([[points objectAtIndex:i]tag]==GradeB.intValue) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeB]; } if ([[points objectAtIndex:i]tag]==GradeC.intValue){ [gradeRecieved replaceObjectAtIndex:i withObject:GradeC]; } if ([gradeRecieved objectAtIndex:i]==nil) { break; // if this condition is met the program must restart. } } while ( i<[gradeRecieved count]) { if ([gradeRecieved objectAtIndex:i] == GradeA ) { [finArray replaceObjectAtIndex:i withObject:GradeA]; i++; continue; } if ([gradeRecieved objectAtIndex:i] == GradeB ) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeB]; i++; continue; } if ([gradeRecieved objectAtIndex:i] == GradeC ) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeC]; i++; continue; } }

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• How can I refactor this to work without breaking the pattern horribly?

  - by SnOrfus

  I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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• A generic C++ library that provides QtConcurrent functionality?

  - by Lucas

  QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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• Distinct or group by on some columns but not others

  - by Nazadus

  I have a view that I'm trying to filter with something similar to DISTINCT on some columns but not others. I have a view like this: Name LastName Zip Street1 HouseholdID (may not be unique because it may have multiple addresses -- think of it in the logical sense as grouping persons but not physical locations; If you lookup HouseholdID 4130, you may get two rows.. or more, because the person may have mutiple mailing locations) City State I need to pull all those columns but filter on LastName,Zip, and Street1. Here's the fun part: The filter is arbitrary -- meaning I don't care which one of the duplicates goes away. This is for a mail out type thing and the other information is not used for any other reason than than to look up a specific person if needed (I have no idea why). So.. given one of the records, you can easily figure out the removed ones. As it stands now, my Sql-Fu fails me and I'm filtering in C# which is incredibly slow and is pretty much a foreach that starts with an empty list and adds the row in if the combined last name, zip, and street aren't are not in the list. I feel like I'm missing a simple / basic part of SQL that I should be understanding.

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• content_tag_for a collection in Rails?

  - by Nick

  I have a Post model. Posts have many Comments. I want to generate a <ul> element for post.comments using content_tag_for. Ideally, it'd produce <ul id="comments_post_7" class="comments"> ... </ul> where 7 is the ID of the Post. The closest I can get uses <% content-tag-for :ul post, :comments do %> which produces <ul id="comments_post_7" class="post"> ... </ul> which is pretty close, except for the class="post". Using :class => :comments in the content_tag_for yields class="post comments", but I just want class="comments". It seems logical that I'd be able to use something like <% content_tag_for :ul post.comments do %> but, sadly, that yields <ul id="array_2181653100" class="array"> ... </ul> I've searched far and wide. I feel like I'm missing some elegant way to do this. Am I? Because, seriously, <ul id="comments_post_<%= post.id %>" class="comments"> is painful.

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• Using git (or some other VCS) at your company

  - by supercheetah

  Some friends of mine and I were talking recently about version control, and how they were using VSS at their jobs, and were probably going to be moving off of that soon. One of them said that his company will likely be going with Team Foundation Server. Eventually, the conversation did get around to talking about some of the open source VCSes out there, including git and SVN. None of us really knew about any companies that use either of these internally, although we imagined that a number of them did so for SVN, but we weren't too sure about git. I brought up Google and Android using it, but my friend figured that's only for the public facing source code, and that they may use something different for internal projects. Apparently it's more than just SCM that makes TFS so intriguing: Microsoft Sales people and support (although my friend did point out somethings to his managers that he thought might be misleading on MS' part) Integration of things beyond SCM, including project management (I'm just finding out that there are geared towards the same things for git) Again, it's Microsoft, and the transition from VSS to TFS seems logical (or does it?) I'm not much of a fan of SVN, so I didn't really bring it up much, but I am curious about whether or not git is used at your company for internal projects. Have you thought about it, and decided against it? Any reason why?

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• Error in bisection method code in Matlab

  - by Amanda Collins

  I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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• Does Socket open another thread? Does it return something?

  - by Roman

  In the client application I call new Socket(serverIP,serverPort). As a result the client application sends a request to the server application to open a socket. Does it start a new thread? I mean which of the following is true? Client application sends a request and immediately starts to execute following commands (not weighting for the answer). Client sends the request and weights for the answer. As soon as the answer is obtained, the client application continues to execute following commands. The second case seems to be more realistic and logical for me. However, I do not understand what happens if the server does not open a socket and it does not say that it does not "want" to open the second (it can happen if the server does not exist or network is broken). What will happen in this case? Will server weight forever? In general it would be nice for the client to know what is the result of its request for the socket. For example I can imagine the following situations: The socket is opened by the server. The server refuses to open a socket. So, server exists, it got the request from the client but it says "no". There is no response from the server. I know that new Socket(serverIP,serverPort) does not "return" this kind of information. But it throws exceptions. One of them is "UnkownHostException". When it is thrown? When the server is not responding for a while (for how long)? ADDED: I just found out that UnknownHostException is thrown to indicate that the IP address of a host could not be determined. So, it is unrelated with the above described situations (server is not responding, server refuses to open a socket).

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• Database schema to store AND, OR relation, association

  - by user455387

  Many thanks for your help on this. In order for an entreprise to get a call for tender it must meet certain requirements. For the first example the enterprise must have a minimal class 4, and have qualification 2 in sector 5. Minimal class is always one number. Qualification can be anything (single, or multiple using AND, OR logical operators) I have created tables in order to map each number to it's given name. Now I need to store requirements in the database. minimal class 4 Sector Qualification 5.2 minimal class 2 Sector Qualifications 3.9 and 3.10 minimal class 3 Sector Qualifications 6.1 or 6.3 minimal class 1 Sector Qualifications (3.1 and 3.2) or 5.6 class Domain < ActiveRecord::Base has_many :domain_classes has_many :domain_sectors has_many :sector_qualifications, :through => :domain_sectors end class DomainClass < ActiveRecord::Base belongs_to :domain end class DomainSector < ActiveRecord::Base belongs_to :domain has_many :sector_qualifications end class SectorQualification < ActiveRecord::Base belongs_to :domain_sector end create_table "domains", :force => true do |t| t.string "name" end create_table "domain_classes", :force => true do |t| t.integer "number" t.integer "domain_id" end create_table "domain_sectors", :force => true do |t| t.string "name" t.integer "number" t.integer "domain_id" end create_table "sector_qualifications", :force => true do |t| t.string "name" t.integer "number" t.integer "domain_sector_id" end

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• c# STILL returning wrong number of cores

  - by Justin

  Ok, so I posted in In C# GetEnvironmentVariable("NUMBER_OF_PROCESSORS") returns the wrong number asking about how to get the correct number of cores in C#. Some helpful people directed me to a couple of questions where similar questions were asked but I have already tried those solutions. My question was then closed as being the same as another question, which is true, it is, but the solution given there didn't work. So I'm opening another one hoping that someone may be able to help realising that the other solutions DID NOT work. That question was How to find the Number of CPU Cores via .NET/C#? which used WMI to try to get the correct number of cores. Well, here's the output from the code given there: Number Of Cores: 32 Number Of Logical Processors: 32 Number Of Physical Processors: 4 As per my last question, the machine is a 64 core AMD Opteron 6276 (4x16 cores) running Windows Server 2008 R2 HPC edition. Regardless of what I do Windows always seems to return 32 cores even though 64 are available. I have confirmed the machine is only using 32 and if I hardcode 64 cores, then the machine uses all of them. I'm wondering if there might be an issue with the way the AMD CPUs are detected. FYI, in case you haven't read the last question, if I type echo %NUMBER_OF_PROCESSORS" at the command line, it returns 64. It just won't do it in a programming environment. Thanks, Justin UPDATE: Outputting PROCESSOR_ARCHITECTURE returns AMD64 from the command line, but x86 from the program. The program is 32-bit running on 64-bit hardware. I was asked to compile it to 64-bit but it still shows 32 cores.

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