Search Results

Search found 9744 results on 390 pages for 'k means'.

Page 282/390 | < Previous Page | 278 279 280 281 282 283 284 285 286 287 288 289  | Next Page >

• Is a confirmation screen necessary for an order form?

  - by abeger

  In a discussion about how to streamline an order form on our site, the idea of eliminating the confirmation screen. So, instead of filling out the form, clicking "Submit", seeing a summary on a confirmation screen and clicking "Confirm", the user would simply fill out the form, hit "Submit", and the order's done. The theory is that fewer clicks and fewer screens means less time to order and therefore the ordering experience is easier. The opposing opinion says that without the confirmation screen, user error increases and people just end up canceling/changing orders after the fact. I'm looking for more input from the SO community. Have you ever done this? How has it worked out, compared to a traditional confirmation screen setup? Are there examples of a true "one click and done" setup on the web (does Amazon's 1-click have a confirmation screen? I've never been courageous enough to try it)? EDIT: Just to clarify, when I say "confirmation screen", I mean a second step where the customer reviews the order before placing it. Even if we did do away with it, the user would still receive a message saying "your order has been placed".

  Read the article

• Saving a record in Authlogic table

  - by denniss

  I am using authlogic to do my authentication. The current model that serves as the authentication model is the user model. I want to add a "belongs to" relationship to user which means that I need a foreign key in the user table. Say the foreign key is called car_id in the user's model. However, for some reason, when I do u = User.find(1) u.car_id = 1 u.save! I get ActiveRecord::RecordInvalid: Validation failed: Password can't be blank My guess is that this has something to do with authlogic. I do not have validation on password on the user's model. This is the migration for the user's table. def self.up create_table :users do |t| t.string :email t.string :first_name t.string :last_name t.string :crypted_password t.string :password_salt t.string :persistence_token t.string :single_access_token t.string :perishable_token t.integer :login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.integer :failed_login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.datetime :last_request_at # optional, see Authlogic::Session::MagicColumns t.datetime :current_login_at # optional, see Authlogic::Session::MagicColumns t.datetime :last_login_at # optional, see Authlogic::Session::MagicColumns t.string :current_login_ip # optional, see Authlogic::Session::MagicColumns t.string :last_login_ip # optional, see Authlogic::Session::MagicColumns t.timestamps end end And later I added the car_id column to it. def self.up add_column :users, :user_id, :integer end Is there anyway for me to turn off this validation?

  Read the article

• jquery ui tabs problem

  - by Eagletrophy

  hi good people, been a while I have had my hands full with a cold but I came back to a problem we never found an answer to, it the homepage of a site I am workin and I said that my tabs would just scatter on a resolution less than mine or around it but not quite. I am on a 1280x800 screen and it displays no problem but as soon as I drop to 1024x768 or 1280x1024 or anything like that this is what it looks like. I wanted to post the code but it means posting alot of HTML and I don't think that will be healthy. hopefully the screenshot will. some one said a while back that my tabs were too big so i reduced them and still. here is the screen shot though: HERE IS THE CSS THAT POWERS THE ADVERTS. THE CSS FOR THE REST OF THE SITE IS JUST A NORMAL JQUERY UI BASE. #adverts{ padding:0px; width:400px; height:109px; float: right; margin-top: auto; margin-left:320px; /* margin-right: auto; */ } enter code here

  Read the article

• Question about the Cloneable interface and the exception that should be thrown

  - by Nazgulled

  Hi, The Java documentation says: A class implements the Cloneable interface to indicate to the Object.clone() method that it is legal for that method to make a field-for-field copy of instances of that class. Invoking Object's clone method on an instance that does not implement the Cloneable interface results in the exception CloneNotSupportedException being thrown. By convention, classes that implement this interface should override Object.clone (which is protected) with a public method. See Object.clone() for details on overriding this method. Note that this interface does not contain the clone method. Therefore, it is not possible to clone an object merely by virtue of the fact that it implements this interface. Even if the clone method is invoked reflectively, there is no guarantee that it will succeed. And I have this UserProfile class: public class UserProfile implements Cloneable { private String name; private int ssn; private String address; public UserProfile(String name, int ssn, String address) { this.name = name; this.ssn = ssn; this.address = address; } public UserProfile(UserProfile user) { this.name = user.getName(); this.ssn = user.getSSN(); this.address = user.getAddress(); } // get methods here... @Override public UserProfile clone() { return new UserProfile(this); } } And for testing porpuses, I do this in main(): UserProfile up1 = new UserProfile("User", 123, "Street"); UserProfile up2 = up1.clone(); So far, no problems compiling/running. Now, per my understanding of the documentation, removing implements Cloneable from the UserProfile class should throw an exception in up1.clone() call, but it doesn't. I've read around here that the Cloneable interface is broken but I don't really know what that means. Am I missing something?

  Read the article

• UIImage imageNamed not autoreleasing correctly

  - by MrHen

  For some reason, the retain/release behavior in the following code has me completely baffled. selectedImage = [UIImage imageNamed:@"icon_72.png"]; [selectedImage release]; This should break but does not. Why? I thought imageNamed autoreleased itself which means the release here is redundant and should break when the autorelease occurs. Here are snippets relevant to selectedImage from the .h and .m files: @property (nonatomic, readonly) UIImage *selectedImage; @synthesize delegate, selectedImage, spacerBottom, currentIndex; Other notes, this does break: selectedImage = [UIImage imageNamed:@"icon_72.png"]; [selectedImage release]; [selectedImage release]; //objc[55541]: FREED(id): message release sent to freed object=0x59245b0 //Program received signal: “EXC_BAD_INSTRUCTION”. As does this: selectedImage = [UIImage imageNamed:@"icon_72.png"]; [selectedImage release]; [selectedImage autorelease]; //objc[55403]: FREED(id): message autorelease sent to freed object=0x59b54c0 //Program received signal: “EXC_BAD_INSTRUCTION”. And so does the following: selectedImage = [UIImage imageNamed:@"icon_72.png"]; [selectedImage autorelease]; [selectedImage release]; //objc[55264]: FREED(id): message release sent to freed object=0x592c9a0 //Program received signal: “EXC_BAD_INSTRUCTION”. And so does this: selectedImage = [UIImage imageNamed:@"icon_72.png"]; [selectedImage autorelease]; [selectedImage autorelease]; //objc[55635]: FREED(id): message release sent to freed object=0x5b305d0 //Program received signal: “EXC_BAD_INSTRUCTION”.

  Read the article

• Emailing smtp with Python error

  - by jakecar

  I can't figure out why this isn't working. I'm trying to send an email from my school email address with this code I got online. The same code works for sending from my GMail address. Does anyone know what this error means? The error occurs after waiting for about one and a half minutes. import smtplib FROMADDR = "FROM_EMAIL" LOGIN = "USERNAME" PASSWORD = "PASSWORD" TOADDRS = ["TO_EMAIL"] SUBJECT = "Test" msg = ("From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n" % (FROMADDR, ", ".join(TOADDRS), SUBJECT) ) msg += "some text\r\n" server = smtplib.SMTP('OUTGOING_SMTP', 587) server.set_debuglevel(1) server.ehlo() server.starttls() server.login(LOGIN, PASSWORD) server.sendmail(FROMADDR, TOADDRS, msg) server.quit() And here's the error I get: Traceback (most recent call last): File "emailer.py", line 13, in server = smtplib.SMTP('OUTGOING_SMTP', 587) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 239, in init (code, msg) = self.connect(host, port) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 295, in connect self.sock = self._get_socket(host, port, self.timeout) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/smtplib.py", line 273, in _get_socket return socket.create_connection((port, host), timeout) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 514, in create_connection raise error, msg socket.error: [Errno 60] Operation timed out

  Read the article

• Calculating File size before download

  - by sagar

  Ok ! Coming to the point directly. What I want to do is explained as follows. I have an url of MP3 file. ( for example Sound File ) Now, When user starts application. Download should start & for that I have implemented following methods. -(void)viewDidLoad { [super viewDidLoad]; NSURL *url=[NSURL URLWithString:@"http://xyz.pqr.com/abc.mp3"]; NSURLRequest *req=[NSURLRequest requestWithURL:url cachePolicy:NSURLCacheStorageNotAllowed timeoutInterval:120]; NSURLConnection *con=[[NSURLConnection alloc] initWithRequest:req delegate:self startImmediately:YES]; if(con){ myWebData=[[NSMutableData data] retain]; } else { // [MainHandler performSelector:@selector(targetSelector:) withObject:nil]; } } -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{ NSLog(@"%@",@"connection established"); [myWebData setLength: 0]; } -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { NSLog(@"%@",@"connection receiving data"); [myWebData appendData:data]; } -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { NSLog(@"%@",@"connection failed"); [connection release]; // [AlertViewHandler showAlertWithErrorMessage:@"Sorry, there is no network connection. Please check your network and try again."]; // [self parserDidEndDocument:nil]; } -(void)connectionDidFinishLoading:(NSURLConnection *)connection { [connection release]; } Now, Above methods work perfectly for downloading. But missing points are as follows. I can not get the exact size which is going to be downloaded. ( means I want to know what is the size of file - which is going to be download )

  Read the article

• Web-based game in Python + Django and client browser polling

  - by ty

  I am creating a text-based game that implements a basic model in which multiple (10+) players interact with data and one moderator watches them and sets certain environmental statistics that affect gameplay. Recently I have begun to familiarize myself with Django. It seems to me that it would be an excellent tool for creating a game quickly, particularly because the nature of my game depends largely on sets of data (which lends itself quite well to a database). I am wondering how to "push" changes made by the game moderator to the players (for example, the moderator can decide to display an image to all players). The game is turn-based, not real-time, but certain messages need to be pushed out in roughly real-time. My thoughts: I could have each player's browser poll a status periodically (say, every 30 seconds) to see if there is a message from a moderator. But this forces a lag and means different players might receive it at different times. And reducing this interval to <10 seems like a bad idea for the server. Is there a better way to inform clients of changes? Would you suggest something other than using a web framework like Django? Thanks!

  Read the article

• Problem with GWT behind a reverse proxy - either nginx or apache

  - by Don Branson

  I'm having this problem with GWT when it's behind a reverse proxy. The backend app is deployed within a context - let's call it /context. The GWT app works fine when I hit it directly: http://host:8080/context/ I can configure a reverse proxy in front it it. Here's my nginx example: upstream backend { server 127.0.0.1:8080; } ... location / { proxy_pass http://backend/context/; } But, when I run through the reverse proxy, GWT gets confused, saying: 2009-10-04 14:05:41.140:/:WARN: Login: ERROR: The serialization policy file '/C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.140:/:WARN: Login: WARNING: Failed to get the SerializationPolicy 'C7F5ECA5E3C10B453290DE47D3BE0F0E' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. 2009-10-04 14:05:41.292:/:WARN: StoryService: ERROR: The serialization policy file '/0445C2D48AEF2FB8CB70C4D4A7849D88.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.292:/:WARN: StoryService: WARNING: Failed to get the SerializationPolicy '0445C2D48AEF2FB8CB70C4D4A7849D88' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. In other words, GWT isn't getting the word that it needs to prepend /context/ hen look for C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc, but only when the request comes throught proxy. A workaround is to add the context to the url for the web site: location /context/ { proxy_pass http://backend/context/; } but that means the context is now part of the url that the user sees, and that's ugly. Anybody know how to make GWT happy in this case? Software versions: GWT - 1.7.0 (same problem with 1.7.1) Jetty - 6.1.21 (but the same problem existed under tomcat) nginx - 0.7.62 (same problem under apache 2.x) I've looked at the traffic between the proxy and the backend using DonsProxy, but there's nothing noteworthy there.

  Read the article

• Can't seem to load a webview from xml, why?

  - by Bilthon

  Well, I'm trying to follow the tutorial from http://rapidandroid.org/wiki/Graphing. But I found a problem just in the first part of it. I'll describe the problem here, I just cannot understand how this could be wrong, it's pretty simple stuff. What am I doing wrong here? First I created a xml file called statistics.xml, in it among other things I put this code: <WebView android:id="@+id/webview" android:layout_height="fill_parent" android:layout_width="fill_parent"/> Now in the activity that is supposed to display this webview I'm doing this: public class DisplayStatistics extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); WebView wv = (WebView) findViewById(R.id.webview); The problem arises here, as I seem to be getting null for wv whenever I test for it. Which means of course that findViewById(R.id.webview) couldn't find the view. But again, what am I doing wrong?? Of course I know I could also instantiate the webview directly from code without the need to specify it from the xml, but I was just wondering what was wrong about this way of doing it. Just in case I also added the following line in my android manifest file: <uses-permission android:name="android.permission.INTERNET" /> I'm not really sure if it's necessary for displaying the webview (I think not) but I just put it there to see if that was the problem, and it turned out it isn't. Thanks Nelson

  Read the article

• Winforms, databinding, Listbox and textbox

  - by Snake

  Hi dear friends, I have a ListBox (MyListBox) on my screen, and a Textbox (MyTextBox). The ListBox is filled with a List(Of T), which are all custom items. Now I try to do this: The ListBox' datasource is the List(Of T). Now when an Item changes I want the textbox to be updated to a particular property of the selected item in my ListBox. In code this means: Me.MyListBox.DisplayMember = "SelectionName" Me.MyListBox.ValueMember = "Id" MyTextbox.DataBindings.Add(New Binding("Text", Me._listOfItems, "SelectedItem.Comment", True, DataSourceUpdateMode.OnPropertyChanged)) Me.MyListBox.DataSource = Me._listOfItems this does not work. But when I bind to SelectedValue instead of SelectedItem it works perfectly. The _listOfItems is declared as this: Dim _listOfItems As List(Of MyItem) = New List(Of MyItem)() Where MyItem is this: public class MyItem { public string SelectionName { get; set; } public int Id { get; set; } public string Comment { get; set; } } I tried overriding the ToString() in MyItem so that it would use that. But that doesn't work either. Anybody care to give it a try? Thanks! -Snakiej

  Read the article

• How can I randomly iterate through a large Range?

  - by void

  I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: class Array def shuffle ret = dup j = length i = 0 while j > 1 r = i + rand(j) ret[i], ret[r] = ret[r], ret[i] i += 1 j -= 1 end ret end end (0..9).to_a.shuffle.each{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle is used to efficiently provide random ordering. My problem is that shuffle needs to operate on an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. Imagine replacing (0..9) with (0..99**99). This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do? [Edit1]: Why do I want to do this? I'm trying to exhaust the search space of a hash algorithm for a N-length input string looking for partial collisions. Each number I generate is equivalent to a unique input string, entropy and all. Basically, I'm "counting" using a custom alphabet. [Edit2]: This means that f(x) in the above examples is a method that generates a hash and compares it to a constant, target hash for partial collisions. I do not need to store the value of x after I call f(x) so memory should remain constant over time. [Edit3/4/5/6]: Further clarification/fixes.

  Read the article

• EDIT Control Showing Squares Instead Of Returns

  - by Nathan Campos

  I'm playing a little bit with PocketC by doing a simple text editor. But with this code to read and to display the contents of the file on the EDIT control: int filehandle; int file_len; string file_mode; initComponents() { createctrl("EDIT", "test", 2, 1, 0, 24, 70, 25, TEXTBOX); wndshow(TEXTBOX, SW_SHOW); guigetfocus(); } main() { filehandle = fileopen(OpenFileDlg("Plain Text Files (*.txt)|*.txt; All Files (*.*)|*.*"), 0, FILE_READWRITE); file_len = filegetlen(filehandle); if(filehandle == -1) { MessageBox("File Could Not Be Found!", "Error", 3, 1); } initComponents(); editset(TEXTBOX, fileread(filehandle, file_len)); } It's all ok, but my test file, now have returns: Hello, World! PocketC Test Of My Editor Then when I open this file on the editor, instead of returns, I just see two squares(that means that it's a unknown character for that control), but if I change the control to a STATIC, it does he returns ok, but I can't edit the text if I use a STATIC. Then I want to know what I need to do to do the returns instead of showing those squares.

  Read the article

• Can a destructor be recursive?

  - by Cubbi

  Is this program well-defined, and if not, why exactly? #include <iostream> #include <new> struct X { int cnt; X (int i) : cnt(i) {} ~X() { std::cout << "destructor called, cnt=" << cnt << std::endl; if ( cnt-- > 0 ) this->X::~X(); // explicit recursive call to dtor } }; int main() { char* buf = new char[sizeof(X)]; X* p = new(buf) X(7); p->X::~X(); // explicit call to dtor delete[] buf; } My reasoning: although invoking a destructor twice is undefined behavior, per 12.4/14, what it says exactly is this: the behavior is undefined if the destructor is invoked for an object whose lifetime has ended Which does not seem to prohibit recursive calls. While the destructor for an object is executing, the object's lifetime has not yet ended, thus it's not UB to invoke the destructor again. On the other hand, 12.4/6 says: After executing the body [...] a destructor for class X calls the destructors for X's direct members, the destructors for X's direct base classes [...] which means that after the return from a recursive invocation of a destructor, all member and base class destructors will have been called, and calling them again when returning to the previous level of recursion would be UB. Therefore, a class with no base and only POD members can have a recursive destructor without UB. Am I right?

  Read the article

• Windows Task Scheduler: IAction.QueryInterface() returns an error I cannot find a definition for

  - by Sascha

  Hello I am attempting to schedule a task (to open an .exe at a specific time) using C++ win32. But at one specific point I am getting an error, I have searched & searched to try & find the definition of this error but I cannot find it? Do you know what this error means: Hexadecimal: 80004003 Decimal: 2147500035 I wont post the whole function because its rather long (unless you may need it to determine the error context?). The code I am using (that causes the error) is the following: // QI for the executable task pointer. hr = action -> QueryInterface( IID_IExecAction, (void**) execAction ); action -> Release(); if( FAILED(hr) ) { printf("QueryInterface call failed for IExecAction: %x %X %u \n", hr, hr, hr ); rootFolder -> Release(); task -> Release(); CoUninitialize(); return false; } The output is: QueryInterface call failed for IExecAction: 80004003 80004003 2147500035

  Read the article

• Invalid argument in sendfile() with two regular files

  - by Daniel Hershcovich

  I'm trying to test the sendfile() system call under Linux 2.6.32 to zero-copy data between two regular files. As far as I understand, it should work: ever since 2.6.22, sendfile() has been implemented using splice(), and both the input file and the output file can be either regular files or sockets. The following is the content of sendfile_test.c: #include <sys/sendfile.h> #include <fcntl.h> #include <stdio.h> int main(int argc, char **argv) { int result; int in_file; int out_file; in_file = open(argv[1], O_RDONLY); out_file = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644); result = sendfile(out_file, in_file, NULL, 1); if (result == -1) perror("sendfile"); close(in_file); close(out_file); return 0; } And when I'm running the following commands: $ gcc sendfile_test.c $ ./a.out infile The output is sendfile: Bad file descriptor Which means that the system call resulted in errno = -EINVAL, I think. What am I doing wrong?

  Read the article

• How to identify HTML elements (in javascript) in a browser agnostic fashion

  - by gatapia

  Hi All, I need to identify all html elements on a page in a browser agnostic fashion. What I am basically doing is using mouse events to record clicks on the page. I need to record which element was clicked. So I add a mouse down listener to the document.body element. And on mouse down I get the element under the mouse. Lets say its a div. I then use the index of that div inside the document.getElementsByTagName('*') nodelist and the nodeName ('div') to identify that div. A sample element id would be div45 which means its a div and its the 45th element in the '*' nodelist. This is all fine and good until I use IE which gives me different indexes. So div45 in FireFox may be div47 in IE. Anyone have any ideas? I just need the id of all elements on the page to be the same in any browser, perhaps indexing is not good enough but I really don't have any more ideas. Thanks Guido

  Read the article

• Silverlight MVVM binding seems not to work

  - by Savvas Sopiadis

  Hi everybody! Building my first SL MVVM application (Silverlight4 RC) and have some issues i don't understand. Having a WPF background i don't know what is going on here: ViewModel has several properties, in which one is called SelectedRecord. This is a get only property and is defined like this: public Culture SelectedRecord { get { return culturesView.View.CurrentItem as Culture; } } As you can see it is gets the current value of a CollectionViewSource (called culturesView). So if i select a Culture, the SelectedRecord (gets a value directly from within the CollectionViewSource) as expected. (Actually there is a datagrid control bound to the CollectionViewSource, hence it is possible to change the selected item) OK. Now to the View . There are several views which access this ViewModel and in particular there is one which shows the values of the aforementioned property SelectedRecord (let's call it the EditView). To show this EditView there is a button (which has its Command property bound to an ICommand in the ViewModel) which functions (the first time) as expected. This means: 1st try : i select a record, switch to EditView, outcome: selected record values are shown (as expected!!). 2nd try: switch back to datagrid, select another record, switch to EditView, outcome: the values of the previous shown record are shown again!!! WHY?? First i thought that the SelectedRecord has not the correct value set, but i was mistaken: it HAS the correct value! So it should be shown!? What am i missing? In WPF this would work!! Thanks in advance

  Read the article

• GUI for generating XML

  - by Kenston

  Hello. Does anybody know of GUIs for generating XMLs? This means the user will not be presented with an IDE with support for XML for him to type XML codes. This would be helpful for non-technical people using the system. I know this sounds easy, given many libraries that can help in generating XMLs. The issue here is that the schema is really that flexible rather than being straightforward like representing books in a library with their properties. Imagine HTML, where we can create font tags inside a body, a table, a div, or nested even within itself. The solution is a WYSIWYG application that allows user to generate html codes (XML). However, that is good for XML applied in webpages since they involve visual aspect and design. My application of XML would focus on representing some conceptual and computational definitions, much like sql-like syntax, but more than that. I'm actually after the approach or previous works done or tried, although having a library/working framework for that would be better. Btw, I'm using Java for this project. Currently, I'm just thinking of presenting element tags where user will be able to drag and drop them and nest them with each other. And perhaps, assist them through a forms in inputing values for XML attributes. I'm still hoping if there are better ideas from the community. Thank you.

  Read the article

• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

  Read the article

• When optimizing database queries, what exactly is the relationship between number of queries and siz

  - by williamjones

  To optimize application speed, everyone always advises to minimize the number of queries an application makes to the database, consolidating them into fewer queries that retrieve more wherever possible. However, this also always comes with the caution that data transferred is still data transferred, and just because you are making fewer queries doesn't make the data transferred free. I'm in a situation where I can over-include on the query in order to cut down the number of queries, and simply remove the unwanted data in the application code. Is there any type of a rule of thumb on how much of a cost there is to each query, to know when to optimize number of queries versus size of queries? I've tried to Google for objective performance analysis data, but surprisingly haven't been able to find anything like that. Clearly this relationship will change for factors such as when the database grows in size, making this somewhat individualized, but surely this is not so individualized that a broad sense of the landscape can't be drawn out? I'm looking for general answers, but for what it's worth, I'm running an application on Heroku.com, which means Ruby on Rails with a Postgres database.

  Read the article

• Localization: How to allow the user to define custom resources without compiling?

  - by gehho

  In our application, we have a collection of data items, each with a DisplayedName property. This property should be localized, i.e. it should be displayed in the language selected by the user. Therefore, another property, DisplayedNameResourceKey, specifies which resource should be returned by the DisplayedName property. In simplified code this means something like this: public string DisplayedName { get { return MyResources.ResourceManager.GetObject(this.DisplayedNameResourceKey); } } public string DisplayedNameResourceKey { get; set; } Now, the problem is: The user should be able to edit these items including the DisplayedName, or more precisely the DisplayedNameResourceKey. And not only this, but the user should also be able to somehow define new resources which he can then reference. That is, he can either choose from a predefined set of resources (some commonly used names), or define a custom resource which then needs to be localized by the user as well. However, the user cannot add custom resources to MyResources at runtime and without compiling. Therefore, another approach is needed. It does not have to be an extremely user-friendly way (e.g. UI is not required) because this will typically be done by our service engineers. I was thinking about using a txt or csv file containing pairs of resource keys and the corresponding translations. A separate file would exist for every language at a predefined location. But I am not really satisfied with that idea because it involves a lot of work to resolve the resources. Does anyone know a good approach for such a situation?

  Read the article

• db:migrate creates sequences but doesn't alter table?

  - by RewbieNewbie

  Hello, I have a migration that creates a postres sequence for auto incrementing a primary identifier, and then executes a statement for altering the column and specifying the default value: execute 'CREATE SEQUENCE "ServiceAvailability_ID_seq";' execute <<-SQL ALTER TABLE "ServiceAvailability" ALTER COLUMN "ID" set DEFAULT NEXTVAL('ServiceAvailability_ID_seq'); SQL If I run db:migrate everything seems to work, in that no errors are returned, however, if I run the rails application I get: Mnull value in column "ID" violates not-null constraint I have discovered by executing the sql statement in the migration manually, that this error is because the alter statement isn't working, or isn't being executed. If I manually execute the following statement: CREATE SEQUENCE "ServiceAvailability_ID_seq; I get: error : ERROR: relation "serviceavailability_id_seq" already exists Which means the migration successfully created the sequence! However, if I manually run: ALTER TABLE "ServiceProvider" ALTER COLUMN "ID" set DEFAULT NEXTVAL('ServiceProvider_ID_seq'); SQL It runs successfully and creates the default NEXTVAL. So the question is, why is the migration file creating the sequence with the first execute statement, but not altering the table in the second execute? (Remembering, no errors are output on running db:migrate) Thank you and apologies for tl:dr

  Read the article

• Messaging pattern question

  - by Al Bundy

  Process A is calculating values for objects a1, a2, a3 etc. and is sending results to the middleware queue (RabbitMQ). Consumers read the queue and process these results further. Periodically process A has to send a snapshot of these values, so consumers could do some other calculations. Values for these objects might change independently. The queue might look like this a1, a1, a2, a1, a2, a2, a3... Consumers process each item in the queue. The snapshot has to contain all objects and consumers will process this message for all objects in one go. So the requirement is to have a queue like this: a1, a1, a3, a2, a2, [snapshot, a1, a2, a3], a3, a1 ... The problem is that these items are of different types: one type for objects like a1, a2 and other for a snapshot. This means that they should be processed in a diferent queues, but in that case there is a race condition: consumers might process objects before processing a snapshot. Is there any pattern to solve this (quite common) problem? We are using RabbitMQ for message queueing.

  Read the article

• JSESSIONID collision between two servers on same ip but different ports

  - by Steve Armstrong

  I've got a situation where I have two different webapps running on a single server, using different ports. They're both running Java's Jetty servlet container, so they both use a cookie parameter named JSESSIONID to track the session id. These two webapps are fighting over the session id. Open a Firefox tab, and go to WebApp1 WebApp1's HTTP response has a set-cookie header with JSESSIONID=1 Firefox now has a Cookie header with JSESSIONID=1 in all it's HTTP requests to WebApp1 Open a second Firefox tab, and go to WebApp2 The HTTP reqeust to WebApp2 also has a Cookie header with JSESSIONID=1, but in the doGet, when I call req.getSession(false); I get null. And if I call req.getSession(true) I get a new Session object, but then the HTTP response from WebApp2 has a set-cookie header with JSESSIONID=20 Now, WebApp2 has a working Session, but WebApp1's session is gone. Going to WebApp1 will give me a new session, blowing away WebApp2's session. Continue forever So the Sessions are thrashing between each web app. I'd really like for the req.getSession(false) to return a valid session if there's already a JSESSIONID cookie defined. One option is to basically reimplement the Session framework with a HashMap and cookies called WEBAPP1SESSIONID and WEBAPP2SESSIONID, but that sucks, and means I'll have to hack the new Session stuff into ActionServlet and a few other places. This must be a problem others have encountered. Is Jetty's HttpServletRequest.getSession(boolean) just crappy?

  Read the article

< Previous Page | 278 279 280 281 282 283 284 285 286 287 288 289  | Next Page >