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• Cross Platform C library for GUI Apps?

  - by Moshe

  Free of charge, simple to learn/use, Cross Platform C library for GUI Apps? Am I looking for Qt? Bonus question: Can I develop with the said library/toolkit on Mac then recompile on PC/Linux? Super Bonus Question: Link to tutorial and/or download of said library. (RE)EDIT: The truth is that I'm in the process of catching up on the C family (coming from web development - XHTML/PHP/MySQL) to learn iPhone development. I do understand that C is not C++ or ObjectiveC but I want to keep the learning curve as simple as possible. Not to get too off topic, but I am also on the lookout for good starter books and websites. I've found this so far. I'm trying to kill many birds with one stone here. I don understand that there are platform specific extensions, but I will try to avoid those for porting purposes The idea is that I want to write the code on one machine and just compile thrice. (Mac/Win/Linux) If Objective C will compile on Windows and Linux as well as OS X then that's good. If I must use C++, that's also fine. EDIT: Link to QT Please...

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• Generated images fail to load in browser

  - by notJim

  I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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• Submit a form and get a JSON response with jQuery

  - by Leopd

  I expect this is easy, but I'm not finding a simple explanation anywhere of how to do this. I have a standard HTML form like this: <form name="new_post" action="process_form.json" method=POST> <label>Title:</label> <input id="post_title" name="post.title" type="text" /><br/> <label>Name:</label><br/> <input id="post_name" name="post.name" type="text" /><br/> <label>Content:</label><br/> <textarea cols="40" id="post_content" name="post.content" rows="20"></textarea> <input id="new_post_submit" type="submit" value="Create" /> </form> I'd like to have javascript (using jQuery) submit the form to the form's action (process_form.json), and receive a JSON response from the server. Then I'll have a javascript function that runs in response to the JSON response, like function form_success(json) { alert('Your form submission worked'); // process json response } How do I wire up the form submit button to call my form_success method when done? Also it should override the browser's own navigation, since I don't want to leave the page. Or should I move the button out of the form to do that?

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• Codeigniter only loads the default controller

  - by fh47331

  I am very new to CodeIgniter, but have been programming PHP for ages. I'm writing some software at the moment and using CI for the first time with it. The default controller is set to the first controller I want to action call 'login' (the controller is login.php, the view is login.php. When the form is submitted it calls the 'authenticate' controller. This executes fine, process the login data correctly and then does a redirect command (without any output to the screen prior) to the next page in this case 'newspage'. The problem is that the redirect, never reaches 'newspage' but the default controller runs again. It doesn't matter what I put ... ht tp://domain.name/anything ... (yes im using .htaccess to remove the index.php) the anything never gets called, just the default controller. I have left the standard 'welcome.php' controller and 'welcome_message.php' in the folders and even putting ht tp://domain.name/welcome all I get is the login screen! (Obviously there shouldn't be a space between the http - thats just done so it does not show as a hyperlink!) Can anyone tell me what i've done wrong!

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• How should I manage/declare dependencies between open source C# projects?

  - by munificent

  I've got a game (a roguelike to be specific) in C# that I'm in the process of cleaning up to open source. One step I'd like to take is splitting it into three distinct pieces: A simple package of utility classes, things like 2D arrays, vectors, etc. A terminal UI package that gives you a curses-like display. It depends on 1. The actual game, which uses 1 and 2. Right now, these are all separate projects in the same solution, but I'd kind of like to make them completely separate projects (in the "open source project" sense, not the "visual studio project" use of the term) with their own names and repos. I think, at the very least, #1 is generally useful even if you aren't building game, and I don't want someone to have to build an entire game just to get some handy functions. What I'm not sure about is how to handle the dependencies if I split up the solution. If someone decides they want to sync the game, how should I ensure they also get 1 and 2? Include the built dependent .dlls in the games repo? Just document, "you need these other projects and they must be in a path relative to the game like this". Just leave it all one giant solution and a single repo. Something I'm not thinking of?

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• Cross Thread problem C#

  - by Frederik Witte

  Hello people - I got this code (lg_log is a listbox, and i want it to log the start_server.bat) Here is the code i got: public void bt_play_Click(object sender, EventArgs e) { lg_log.Items.Add("Starting Mineme server .."); string directory = Directory.GetCurrentDirectory(); var info = new ProcessStartInfo(directory + @"\start_base.bat") {UseShellExecute = false, RedirectStandardOutput = true, CreateNoWindow = true, WorkingDirectory = directory + @"\Servers\Base"}; var proc = new Process { StartInfo = info, EnableRaisingEvents = true }; proc.OutputDataReceived += (obj, args) => { if (args.Data != null) { lg_log.Items.Add(args.Data); } }; proc.Start(); proc.BeginOutputReadLine(); lg_log.Items.Add("Server is now running!"); proc.WaitForExit(); } When i run this, i'll get an error .. Anybody can help me? I'll rate the answer up! :D Edit: The error i get is this: System.InvalidOperationException Hope it helps :) The error comes at the lg_log.Items.Add(args.Data); code line

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• Best practices for encrytping continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (on waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• Visual Studio 2012 won't start

  - by David Aleu

  I installed VS2012 Premium from our MSDN subscription and it was working fine the first couple of days but then I installed a few extensions I can't now start VS2012 and it gives the error: Faulting application name: devenv.exe, version: 11.0.50727.1, time stamp: 0x5011ecaa Faulting module name: ntdll.dll, version: 6.1.7601.17725, time stamp: 0x4ec49b8f Exception code: 0xc0000374 Fault offset: 0x000ce6c3 Faulting process id: 0xee8 Faulting application start time: 0x01cd89bb777fc1dd Faulting application path: C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\devenv.exe Faulting module path: C:\Windows\SysWOW64\ntdll.dll I'm running it on Windows 7 64 bit. I've tried to repair, uninstall and install again and nothing. I tried to restore to a previous restore system point but nothing. The extensions I installed I can remember: VS10x Code Map VSCommands Visual SVN Nuget manager (all the above my colleagues have it too and it works fine for them) and: Web Essentials Visual Studio Color Theme Editor SlowCheetah Mobile Ready HTML5 Questions are: Anyone else has had this problem? Is there a way I can uninstall extensions from a command line or software? (I removed the extensions folder but that doesn't do anything) Can I repair the "C:\Windows\SysWOW64\ntdll.dll"? Is it really a problem with this dll? I haven't been able to find any similar issue in other versions and because VS2012 is new doesn't seem to be much information either.

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• What are the benefits and risks of moving to a Model Driven Architecture approach?

  - by Tone

  I work for a company with about 350 employees and we are in the process of growing. Our current codebase is not structured very well and we are looking both at how to improve it immediately (by organizing objects into namespaces, separating concerns, etc.) and moving to a model driven architecture approach, where we model and design everything first with uml, then generate code from that model. We have been looking heavily at Sparx Systems Enterprise Architect (EA) (which is UML 2.0 capable) and we are also considering the tools in VS 2010. I know there are other tools out there (Rational XDE being one) but I really do not think we can spend $1500+ per license at this point. I'm not looking for answers on which tool is better than another but more for experiences moving from a cowboy coding environment (that is, little planning and design, just jump in and start coding) to a model driven architecture. Looking back was it helpful to your organization? What are the pain points? What are the risks? What are the benefits?

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• Wicket application + Apache + mod_jk - AJP queues are filling up!

  - by nojyarg

  Dear community, We are having a Wicket-based Java application deployed in a production server cluster using Apache (2.2.3) with mod_jk (1.2.30) as load balancing component w/ sticky session and Jboss 5 as application container for the Java application. We are inconsistently seeing an issue in our production environment where our AJP queues between Apache and Jboss as shown in the JMX console fill up with requests to the point where the application server is no longer taking on any new requests. When looking at all involved system components (overall traffic, load db, process list db, load of all clustered application server nodes) nothing points towards a capacity issue which would explain why the calls are being stalled in the AJP queue. Instead all systems appear sufficiently idle. So far, our only remedy to this issue is to restart the appservers and the load balancer which only occasionally clears the AJP queues. We are trying to figure out why the queues are filling up to the point that no calls get returned to the end user although the system is not under a high load. Has anyone else experienced similar problems? Are there any other system metrics we should monitor that could explain the queuing behavior? Is this potentially a mod_jk issue? If so, is it advisable to swap mod_jk with mod_cluster to resolve the issue? Any advice is highly appreciated. If I can provide additional information for the sake of troubleshooting I would be more than willing to do so. /Ben

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• Drupal view filter to show only one of a certain item

  - by Joel

  I'm fairly new to Drupal, and am using Node Import to take a TSV file and turn it into nodes. I'm hitting a problem, though, with automating updates to the nodes. Again, I'd like to take a Tab Separated Values text file, and load it into my site via Node Import (or whatever else anyone might suggest) and then only show updated Nodes. Here's a specific example: I have a Node with the following info: StoreId Name Address Phone Contact 01 Name1 Address1 Phone1 Contact1 02 Name2 Address2 Phone2 Contact2 etc. The info pulls into the nodes just fine (Thank you Node Import!), but we also want to process updates to the nodes. So far I have two ideas... figure out how to delete duplicate (previous) instances of the same StoreID, or just save the node with the duplicate StoreID (and new other info) and just display the most current version. In Views, I can get it to show the nodes and everything, but I can't figure out how to only display the most recent version of each StoreID. A view of views would work, but I can't seem to get that to work, either. Any ideas or other approaches I could take? Thanks in advance for the help!

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• .NET Remoting: Getting underlying socket?

  - by Alan

  Hi, I'm writing a light remoting app to assist in debugging a problem with remoting communication. This app mimics much of what a larger application does: Periodically sends a heartbeat to another peer application, and periodically verifies that a heartbeat has been received within some time threshold. What we're seeing is in our big application, the heartbeats seem to get dropped. One peer will go for long periods of time without seeing heartbeats from another peer, until the peer that is "dead" is restarted. The big application is responsive in all other ways. We believe it has something to do with the network setup. We were able to repro the problem locally, and fixed it by making some configuration changes to our test environment. To help our customer diagnose the issue, the mini-remoting app needs to log as much information as possible. So, is there a way to get the underlying socket for the remoting connection? I'm aware that I could write a custom sink for this, but I'd like to keep the actual remoting process as close to what is implemented in the big app as possible. Also as an aside, any ideas why the big-app might be "dropping" heartbeats?

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• In SQL Server what is most efficient way to compare records to other records for duplicates with in

  - by Glenn

  We have an SQL Server that gets daily imports of data files from clients. This data is interrelated and we are always scrubbing it and having to look for suspect duplicate records between these files. Finding and tagging suspect records can get pretty complicated. We use logic that requires some field values to be the same, allows some field values to differ, and allows a range to be specified for how different certain field values can be. The only way we've found to do it is by using a cursor based process, and it places a heavy burden on the database. So I wanted to ask if there's a more efficient way to do this. I've heard it said that there's almost always a more efficient way to replace cursors with clever JOINS. But I have to admit I'm having a lot of trouble with this one. For a concrete example suppose we have 1 table, an "orders" table, with the following 6 fields. order_id, customer_id product_id, quantity, sale_date, price We want to look through the records to find suspect duplicates on the following example criteria. These get increasingly harder. 1. Records that have the same product_id, sale_date, and quantity but different customer_id's should be marked as suspect duplicates for review. 2. Records that have the same customer_id, product_id, quantity and have sale_dates within five days of each other should be marked as suspect duplicates for review 3. Records that have the same customer_id, product_id, but different quantities within 20 units, and sales dates within five days of each other should be considered suspect. Is it possible to satisfy each one of these criteria with a single SQL Query that uses JOINS? Is this the most efficient way to do this?

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• How can I debug PEAR auth?

  - by croceldon

  I have a directory on my site that I've implemented PEAR's Auth to run my authentication. It is working great. However, I've tried to make a copy of my site (it's going to be translated to a different language), and on this new site, the Auth process doesn't seem to be working correctly. I can login properly, but every time I try to go to a different page in the same directory, and use Auth to authorize, it forces me to login again. Here's my logic: $auth_options = array( 'dsn' => mysql://user:password@server/db', 'table' => 'users', 'usernamecol' => 'username', 'passwordcol' => 'password', 'db_fields' => '*' ); $auth = new Auth("DB", $auth_options, "login_function"); $auth->setFailedLoginCallback('bad_login'); $auth->start(); if (!$auth->checkAuth()) { die('cannot succeed in checkAuth') exit; } else { include("nocache.php"); } This is part of a file that's included in every php page I that I desire to require authentication. I can login properly once, but whenever I then try to go to a different page that requires authentication, it makes me login again (and I see the 'cannot succeed' die message at the bottom of the page). Again, this solution works fine on my original site, I copied all the files, and only changed the db server/password - it still doesn't work. And I'm using the same webhost for both. What am I doing wrong here? Or how can I debug this further?

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• Parallel processing from a command queue on Linux (bash, python, ruby... whatever)

  - by mlambie

  I have a list/queue of 200 commands that I need to run in a shell on a Linux server. I only want to have a maximum of 10 processes running (from the queue) at once. Some processes will take a few seconds to complete, other processes will take much longer. When a process finishes I want the next command to be "popped" from the queue and executed. Does anyone have code to solve this problem? Further elaboration: There's 200 pieces of work that need to be done, in a queue of some sort. I want to have at most 10 pieces of work going on at once. When a thread finishes a piece of work it should ask the queue for the next piece of work. If there's no more work in the queue, the thread should die. When all the threads have died it means all the work has been done. The actual problem I'm trying to solve is using imapsync to synchronize 200 mailboxes from an old mail server to a new mail server. Some users have large mailboxes and take a long time tto sync, others have very small mailboxes and sync quickly.

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• Threadpool design question

  - by ZeroVector

  I have a design question. I want some feedback to know if a ThreadPool is appropriate for the client program I am writing. I am having a client running as a service processing database records. Each of these records contains connection information to external FTP sites [basically it is a queue of files to transfer]. A lot of them are to the same host, just moving different files. Therefore, I am grouping them together by host. I want to be able to create a new thread per host. I really don't care when the transfers finish, they just need to do all the work (or try to do) they were assigned, and then terminate once they are finished, cleaning up all resources they used in the process. I anticipate no more than 10-25 connections to be established. Once the transfer queue is empty, the program will simply wait until there are records in the queue again. Is the ThreadPool a good candidate for this or should I use a different approach? Edit: For the most part, this is the only significant custom application running on the server.

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• How to handle window closed in the middle of a long running operation gracefully?

  - by Marek

  We have the following method called directly from the UI thread: void DoLengthyProcessing() { DoStuff(); var items = DoMoreStuff(); //do even more stuff - 200 lines of code trimmed this.someControl.PrepareForBigThing(); //someControl is a big user control //additional 100 lines of code that access this.someControl this.someControl.Finish(items); } Many of the called methods call Application.DoEvents() (and they do so many times) (do not ask me why, this is black magic written by black magic programmers and it can not be changed because everyone is scared what the impact would be) and there is also an operation running on a background thread involved in the processing. As a result, the window is not fully nonresponsive and can be closed manually during the processing. The Dispose method of the form "releases" the someControl variable by setting it to null. As a result, in case the user closes the window during the lengthy process, a null reference exception is thrown. How to handle this gracefully without just catching and logging the exception caused by disposal? Assigning the someControl instance to a temporary variable in the beginning of the method - but the control contains many subcontrols with similar disposal scheme - sets them to null and this causes null reference exceptions in other place put if (this.IsDisposed) return; calls before every access of the someControl variable. - making the already nasty long method even longer and unreadable. in Closing event, just indicate that we should close and only hide the window. Dispose it at the end of the lengthy operation. This is not very viable because there are many other methods involved (think 20K LOC for a single control) that would need to handle this mechanism as well. How to most effectively handle window disposal (by user action) in the middle of this kind of processing?

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• css absolute positioning hidden scrollbars ... with a twist

  - by ScottE

  I'm working on a website that targets 1024 X 768 as the minimum resolution. So, we're at about 970px wide. Design came back with an interesting layout that has a centered site with a banner that actually exceeds this width (1288px to be exact) that will look good for users with greater resolution, but look fine at 1024. So, to prevent scrollbars from showing up for those at 1024 I positioned the banner absolutely and used overflow-x: hidden on the body. This works just fine across our target browsers. Now, the client has come back and asked for scrollbars to be present for users on 800 X 600 (yes, this is not the target) so they can see a critical login button. How can this be accommodated for those 2% of their users without making radical changes? All I can think of is to detect their screen width and remove the overflow-x:hidden. You have to love when requirements change late in the build process! Edit - here's what I have that seems simple enough to me - any caveats here? if (screen.width === 800) { $("body").css("overflow-x", "visible"); }

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• CREATE VIEW called multiple times not creating all views

  - by theninepoundhammer

  Noticing strange behavior in SQL 2005, both Express and Enterprise Edition: In my code I need to loop through a series of values (about five in a row), and for each value, I need to insert the value into a table and dynamically create a new view using that value as part of the where clause and the name of the view. The code runs pretty quickly, but what I'm noticing is that all the values are inserted into the table correctly but only the LAST view is being created. Every time. For example, if the values I'm using are X1, X2, X3, X4, and X5, I'll run the process, open up Mgmt Studio, and see five rows in the table with the correct five values, but only one view named MyView_x5 that has the correct WHERE clause. At first, I had this loop in an SSIS package as part of a larger data flow. When I started noticing this behavior, I created a stored proc that would create the CREATE VIEW statement dynamically after the insert and called EXECUTE to create the view. Same result. Finally, I created some C# code using the Enterprise Library DAAB, and did the insert and CREATE VIEW statements from my DLL. Same result every time. Most recently, I turned on Profiler while running against the Enterprise Edition and was able to verify that the Batch Started and Batch Completed events were being fired off for each instance of the view. However, like I said, only the last view is actually being created. Does anyone have any idea why this might be happening? Or any suggestions about what else to check or profile? I've profiled for error messages, exceptions, etc. but don't see any in my trace file. My express edition is 9.00.1399.06. Not sure about the Enterprise edition but think it is SP2.

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• Tips for submitting a library to Boost?

  - by AraK

  Hi everyone, Summer is coming, and a group of friends and I are getting ready for it :) We decided to build a compile-time Arbitrary precision Unsigned Integers. We would like to provide a set of integers algorithms(functions) with the library. We have seen a number of requests for such a library(SoC2010, C++0x Standard Library wishlist). Also, a regular run-time bigint is requested usually with that, but we don't want to go into the hassle of memory management. The idea came to me from a library called TTMath, unfortunately this library works only on specific platforms because Assembly was used extensively in the library. We would like to write a standard library, depending on the C++ standard library and Boost. Also, we would like to use the available C++0x facilities in current compilers like user-defined literals and others. This would technically make the library non-standard for a while, but we think that it is a matter of time the new standards will be official. Your hints on the whole process including design, implementation, documentation, maintainable of the library are more than welcom. We are a group of students and fresh graduates who are looking for something interesting in the summer, but we see that Boost is full of gurus and we don't want to forget something too obvious. We are communicating on-line, so there is no shared white-boards :( Thanks,

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• How to call stored procedure by hibernate?

  - by user367097

  Hi I have an oracle stored procedure GET_VENDOR_STATUS_COUNT(DOCUMENT_ID IN NUMBER , NOT_INVITED OUT NUMBER,INVITE_WITHDRAWN OUT NUMBER,... rest all parameters are OUT parameters. In hbm file I have written - <sql-query name="getVendorStatus" callable="true"> <return-scalar column="NOT_INVITED" type="string"/> <return-scalar column="INVITE_WITHDRAWN" type="string"/> <return-scalar column="INVITED" type="string"/> <return-scalar column="DISQUALIFIED" type="string"/> <return-scalar column="RESPONSE_AWAITED" type="string"/> <return-scalar column="RESPONSE_IN_PROGRESS" type="string"/> <return-scalar column="RESPONSE_RECEIVED" type="string"/> { call GET_VENDOR_STATUS_COUNT(:DOCUMENT_ID , :NOT_INVITED ,:INVITE_WITHDRAWN ,:INVITED ,:DISQUALIFIED ,:RESPONSE_AWAITED ,:RESPONSE_IN_PROGRESS ,:RESPONSE_RECEIVED ) } </sql-query> In java I have written - session.getNamedQuery("getVendorStatus").setParameter("DOCUMENT_ID", "DOCUMENT_ID").setParameter("NOT_INVITED", "NOT_INVITED") ... continue till all the parametes . I am getting the sql exception 18:29:33,056 WARN [JDBCExceptionReporter] SQL Error: 1006, SQLState: 72000 18:29:33,056 ERROR [JDBCExceptionReporter] ORA-01006: bind variable does not exist Please let me know what is the exact process of calling a stored procedure from hibernate. I do not want to use JDBC callable statement.

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• Bizzare results when running two Visual Studio Express C++ 2008 solutions

  - by Jamie Keeling

  This is a follow on from my previous question although this is about something else. I've been having a problem where for some reason my message that I pass from one process to another only displays the first letter, in this case "M". My application based on a MSDN sample so to make sure I hadn't missed something I create a seperate solution, added the MSDN sample (Without any changes for my needs) and unsuprisingly it works fine. Now for the weird bit, when I run the MSDN sample running (As in debugging) and have my own application running, the text prints out fine without any problems. The second I run my on it's own without the original MSDN sample being open it fails to work and only shows an "M". I've looked in the debugger and don't seem to notice anything suspicious (It's a slightly dated picture, I've fixed the data type inconsistency). Can anyone provide a solution as to this? I've never encountered anything like this before. To look at my source code it's easier to just look at the link I posted at the top of the question, there's no point in me posting it twice. Thank you for any help.

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• Best way to run multiple queries per second on database, performance wise?

  - by Michael Joell

  I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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• Vectorize matrix operation in R

  - by Fernando

  I have a R x C matrix filled to the k-th row and empty below this row. What i need to do is to fill the remaining rows. In order to do this, i have a function that takes 2 entire rows as arguments, do some calculations and output 2 fresh rows (these outputs will fill the matrix). I have a list of all 'pairs' of rows to be processed, but my for loop is not helping performance: # M is the matrix # nrow(M) and k are even, so nLeft is even M = matrix(1:48, ncol = 3) # half to fill k = nrow(M)/2 # simulate empty rows to be filled M[-(1:k), ] = 0 cat('before fill') print(M) # number of empty rows to fill nLeft = nrow(M) - k nextRow = k + 1 # list of rows to process (could be any order of non-empty rows) idxList = matrix(1:k, ncol = 2) for ( i in 1 : (nLeft / 2)) { row1 = M[idxList[i, 1],] row2 = M[idxList[i, 2],] # the two columns in 'results' will become 2 rows in M # fake result, return 2*row1 and 3*row2 results = matrix(c(2*row1, 3*row2), ncol = 2) # fill the matrix M[nextRow, ] = results[, 1] nextRow = nextRow + 1 M[nextRow, ] = results[, 2] nextRow = nextRow + 1 } cat('after fill') print(M) I tried to vectorize this, but failed... appreciate any help on improving this code, thanks!

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• F# How to tokenise user input: separating numbers, units, words?

  - by David White

  I am fairly new to F#, but have spent the last few weeks reading reference materials. I wish to process a user-supplied input string, identifying and separating the constituent elements. For example, for this input: XYZ Hotel: 6 nights at 220EUR / night plus 17.5% tax the output should resemble something like a list of tuples: [ ("XYZ", Word); ("Hotel:", Word); ("6", Number); ("nights", Word); ("at", Operator); ("220", Number); ("EUR", CurrencyCode); ("/", Operator); ("night", Word); ("plus", Operator); ("17.5", Number); ("%", PerCent); ("tax", Word) ] Since I'm dealing with user input, it could be anything. Thus, expecting users to comply with a grammar is out of the question. I want to identify the numbers (could be integers, floats, negative...), the units of measure (optional, but could include SI or Imperial physical units, currency codes, counts such as "night/s" in my example), mathematical operators (as math symbols or as words including "at" "per", "of", "discount", etc), and all other words. I have the impression that I should use active pattern matching -- is that correct? -- but I'm not exactly sure how to start. Any pointers to appropriate reference material or similar examples would be great.

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