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• Matrix multiplication using pairs

  - by sc_ray

  Hi, I am looking into alternate ways to do a Matrix Multiplication. Instead of storing my matrix as a two-dimensional array, I am using a vector such as vector<pair<pair<int,int >,int > > to store my matrix. The pair within my pair (pair) stores my indices (i,j) and the other int stores the value for the given (i,j) pair. I thought I might have some luck implementing my sparse array this way. The problem is when I try to multiply this matrix with itself. If this was a 2-d array implementation, I would have multiplied the matrix as follows: for(i=0; i<row1; i++) { for(j=0; j<col1; j++) { C[i][j] = 0; for(k=0; k<col2; k++) C[i][j] += A[i][j] * A[j][k]; } } Can somebody point out a way to achieve the same result using my vector of 'pair of pairs'? Thanks

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• Updating a Database from DataBound Controls

  - by Avatar_Squadron

  Hi. I'm currently creating a WinForm in VB.NET bound to an access database. Basically what i have are two forms: one is a search form used to search the database, and the other is a details form. You run a search on the searchForm and it returns a list of Primary Keys and a few other identifying values. You then double click on the entry you want to view, and it loads the details form. The Details form has a collection of databound controls to display the data: mostly text boxes and checkboxs. The way i've set it up is i used the UI to build the form and then set the DataBindings Property of each control to "TblPropertiesBindingSource - " where value name is one of the values in the table (such as PropertyID or HasWoodFloor). Then, when you double click an entry in the searchform, I handle the event by parsing the Primary Key (PropertyID) out of the selected row and then storing this to the details form: Note: Detail is the details form that is opened to display the info Private Sub propView_CellDoubleClick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles propView.CellDoubleClick Dim detail As frmPropertiesDetail = New frmPropertiesDetail detail.id = propView.Rows(e.RowIndex).Cells(0).Value detail.Show() End Sub Then, upon loading the details form, it set's the filter on the BindSource as such: TblPropertiesBindingSource.Filter() = "PropertyID=" & id This works great so far. All the controls on the details form will display the correct info. The problem is updating changes. Scenario: If i have the user load the details for say, property 10001, it will show a description in a textBox named descriptionBox which is identical to the value of the description value of for that entry in the database. I want the user to then be able to change the text of the text box (which they can currently do) and click the save button (saveBut) and have the form update all the values in the controls to the database. Theorectically, it should do this as the controls are DataBound, thus i can avoid writing code that tells each entry in the database row to take the value of the aligned control. I've tried calleding PropertiesTableAdapter.Update(PropertiesBindingSource.DataSource), but that doesnt seem to do it.

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• How do interpreters written in C and C++ bind identifiers to C(++) functions

  - by sub

  I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do interpreters written in C/C++ solve this problem? How can I solve this for my own experimental toy interpreter written in C++?

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• What prevents a user from adding controls to an ASP.NET page client side?

  - by Curtis White

  This goes back to my other question which I thought was sufficiently answers but upon reflect am not sure that it was (sorry). Backgrounder: I am generating a form dynamically. I am pulling from the database the controls. I must associate each control with a database ID which is not the user's session id. I do this currently by storing my ID in the ID for the web control with some other stuff to make it unique/clear what I am doing. On the post back, I iterate through all the controls on my web page checking for my special identifier, ie, MyGeneratedTextBox_ID_Unique. This process enables for 2 important steps, identifying the control was one I generated and also getting the ID for this input field. And, all of this works but I'm still concerned about the security of it. I do not see a security issue with showing the actual database ID's in this case, although agree it is not desirable. However, I am concerned of the following possibilities: If a user could add a nefarious control to my collection and use that for a SQL injection attack. More academic, but if a user could somehow store data for fields they do not have access too by changing the id's. I agree this is a "hack" of a way to do it. But my question is, is it a security risk and is there an 'easy' way to do it in a less hack way? I assume that only the controls that are created/instantiated on the page are added to the controls list.. thus all controls must be created server side and thus the security issue is address but just wanted to validate. Thanks again. PS: I could see adding a property for each control and encrypting the viewstate would be a little more secure.

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• How to store and locate multiple interface types within a Delphi TInterfaceList

  - by Brian Frost

  Hi, I'm storing small interfaces from a range of objects into a single TInterfaceList 'store' with the intention of offering list of specific interface types to the end user, so each interface will expose a 'GetName' function but all other methods are unique to that interface type. For example here are two interfaces: IBase = interface //---------------------------------------- function GetName : string; //---------------------------------------- end; IMeasureTemperature = interface(IBase) //------------------------------------ function MeasureTemperature : double; //---------------------------------------- end; IMeasureHumidity = interface(IBase) //---------------------------------------- function MeasureHumidity: double; //---------------------------------------- end; I put several of these interfaces into a single TInterfaceList and then I'd like to scan the list for a specific interface type (e.g. 'IMeasureTemperature') building another list of pointers to the objects exporting those interfaces. I wish to make no assumptions about the locations of those objects, some may export more than one type of interface. I know I could do this with a class hierarchy using something like: If FList[I] is TMeasureTemperature then .. but I'd like to do something simliar with an interface type, Is this possible?

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• Where can I view rountrip information in my ASP.NET application?

  - by ajax81

  Hi All, I'm playing around with storing application settings in my database, but I think I may have created a situation where superfluous roundtrips are being made. Is there an easy way to view roundtrips made to an MS Access (I know, I know) backend? I guess while I'm here, I should ask for advice on the best way to handle this project. I'm building an app that generates links based on file names (files are numbered ints, 0-5000). The files are stored on network shares, arranged by name, and the paths change frequently as files are bulk transfered to create space, etc. Example: Files 1000 - 2000 go to /path/1000s Files 2001 - 3000 go to /path/2000s Files 3001 - 4000 go to /path/3000s etc I'm sure by now you can see where I'm going with this. Ultimately, I'm trying to avoid making a roundtrip to get the paths for every single file as they are displayed in a gridview. I'm open to the notion that I've gone about this all wrong and that my idea might be rubbish. I've toyed around with the notion of just creating a flat file, but if I do that, do I still run into the problem of having that file opened and closed for every file displayed in a gridview?

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• How do C and C++ interpreters bind identifiers to functions

  - by sub

  I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do C/C++ interpreters solve this problem? How can I solve this for my own experimental toy interpreter?

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• SQL left join with multiple rows into one row

  - by beardedd

  Basically, I have two tables, Table A contains the actual items that I care to get out, and Table B is used for language translations. So, for example, Table A contains the actual content. Anytime text is used within the table, instead of storing actual varchar values, ids are stored that relate back to text stored in Table B. This allows me to by adding a languageID column to Table B, have multiple translations for the same row in the database. Example: Table A Title (int) Description (int) Other Data.... Table B TextID (int) - This is the column whose value is stored in other tables LanguageID (int) Text (varchar) My question is more a call for suggestions on how to best handle this. Ideally I want a query that I can use to select from the table, and get the text as opposed to the ids of the text out of the table. Currently when I have two text items in the table this is what I do: SELECT C.ID, C.Title, D.Text AS Description FROM (SELECT A.ID, A.Description, B.Text AS Title FROM TableA A, TranslationsTable B WHERE A.Title = B.TextID AND B.LanguaugeID = 1) C LEFT JOIN TranslationsTable D ON C.Description = D.TextID AND D.LanguaugeID = 1 This query gives me the row from Table A I am looking for (using where statements in the inner select statement) with the actual text based on the language ID used instead of the text ids. This works fine when I am only using one or two text items that need to be translated, but adding a third item or more, it starts to get really messy - essentially another left join on top of the example. Any suggestions on a better query, or at least a good way to handle 3 or more text items in a single row?

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• Apache crashes, probably because of this piece of php code. Can you have a look?

  - by Munim

  I am working on the development of a web based application on codeigniter. I wrote this function to get the timezone data for any city or address. function gettimezone($address) { $_url = 'http://api.local.yahoo.com/MapsService/V1/geocode'; $_url .= sprintf('?appid=%s&location=%s',"phpclasses",rawurlencode($address)); $_result = false; if($_result = file_get_contents($_url)) { preg_match('!<Latitude>(.*)</Latitude><Longitude>(.*)</Longitude>!U', $_result, $_match); $lng = $_match[2]; $lat = $_match[1]; $url = "http://ws.geonames.org/timezone?lat={$lat}&lng={$lng}"; $timedata = file_get_contents($url); $sxml = simplexml_load_string($timedata); return $sxml->timezone; } else return false; } I am working on Windows 7 and xampp 1.7 (php 5.2.8). Is there any possible scenario where this piece of code would crash Apache? The application runs fine almost everytime, but I think running this piece of code when there is no internet connectivity or very poor internet connectivity (thereby no access to either of the webservices I have used) brings down the server. Something like this happened a few times and I think it was due to loss of internet connectivity but I am not sure what exactly is going on. [ By the way, feel free to use this piece of code. Makes 2 web service calls so don't use to too often in your application. Consider storing the results in a database.]

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• C++ Virtual Methods for Class-Specific Attributes or External Structure

  - by acanaday

  I have a set of classes which are all derived from a common base class. I want to use these classes polymorphically. The interface defines a set of getter methods whose return values are constant across a given derived class, but vary from one derived class to another. e.g.: enum AVal { A_VAL_ONE, A_VAL_TWO, A_VAL_THREE }; enum BVal { B_VAL_ONE, B_VAL_TWO, B_VAL_THREE }; class Base { //... virtual AVal getAVal() const = 0; virtual BVal getBVal() const = 0; //... }; class One : public Base { //... AVal getAVal() const { return A_VAL_ONE }; BVal getBVal() const { return B_VAL_ONE }; //... }; class Two : public Base { //... AVal getAVal() const { return A_VAL_TWO }; BVal getBVal() const { return B_VAL_TWO }; //... }; etc. Is this a common way of doing things? If performance is an important consideration, would I be better off pulling the attributes out into an external structure, e.g.: struct Vals { AVal a_val; VBal b_val; }; storing a Vals* in each instance, and rewriting Base as follows? class Base { //... public: AVal getAVal() const { return _vals->a_val; }; BVal getBVal() const { return _vals->b_val; }; //... private: Vals* _vals; }; Is the extra dereference essentially the same as the vtable lookup? What is the established idiom for this type of situation? Are both of these solutions dumb? Any insights are greatly appreciated

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• gcc compilations (sometimes) result in cpu underload

  - by confusedCoder

  I have a larger C++ program which starts out by reading thousands of small text files into memory and storing data in stl containers. This takes about a minute. Periodically, a compilation will exhibit behavior where that initial part of the program will run at about 22-23% CPU load. Once that step is over, it goes back to ~100% CPU. It is more likely to happen with O2 flag turned on but not consistently. It happens even less often with the -p flag which makes it almost impossible to profile. I did capture it once but the gprof output wasn't helpful - everything runs with the same relative speed just at low cpu usage. I am quite certain that this has nothing to do with multiple cores. I do have a quad-core cpu, and most of the code is multi-threaded, but I tested this issue running a single thread. Also, when I run the problematic step in multiple threads, each thread only runs at ~20% CPU. I apologize ahead of time for the vagueness of the question but I have run out of ideas as to how to troubleshoot it further, so any hints might be helpful. UPDATE: Just to make sure it's clear, the problematic part of the code does sometimes (~30-40% of the compilations) run at 100% CPU, so it's hard to buy the (otherwise reasonable) argument that I/O is the bottleneck

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• Pass a variable from the source file to an included file in PHP

  - by Alpha1

  For my website I want to store the general format of the site in a single PHP file in a single location, and each of the different pages content in the local location of the page. I then want to pass the title and content address to the included file via a variable. However I can't get the included format file to read the variables storing the title and content data. AKA, the called file for the individual page would be: <?php $title = 'Some Title'; $source_file = 'content.php'; readfile('http:...../format.php'); ?> The format file would be: <html> ... <title> <?php echo $title; ?> </title> ... <?php include($source_file); ?> ... I recall reading somewhere I need to include something to get the variables at the start of the format file, however I can't remember what it is or find where I found that information.

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• Cached data accessed by reference?

  - by arthurdent510

  I am running into an odd problem, and this is the only thing I can think of. I'm storing a list in cache, and I am randomly losing items from my list as users use the site. I have a class that is called that either goes to cache and returns the list from there, or if the cache is over a certain time frame old, it goes to the database and refreshes the cache. So when I pull the data from cache, this is what it looks like.... results = (List<Software>)cache["software"]; And then I return results and do some processing, filter for security, and eventually it winds up on the screen. For each Software record, there can be multiple resources attached to it, and based on how the security goes they may see some, all, or none of the records. So in the security check it will remove some of those resources from the software record. So my question is.... when I return my results list, is it a reference directly to the cache object? So when I remove a resource from the software object, it is really removing from cache as well? If that is the case, is there any way to not return it as a reference? Thanks!

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• can JockerSoft.Media read/get video file from remote location?

  - by Lynx

  here is the code for JockerSoft.Media // Path of the video and frame storing path string _videopath = "http://www.test.com/Video/test.avi"; //"C:\\test.avi"; string _imagepath = "C:\\test.jpg" Bitmap bmp = FrameGrabber.GetFrameFromVideo(_videopath, 0.1d); bmp.Save(_imagepath, System.Drawing.Imaging.ImageFormat.Gif); // Save directly frame on specified location FrameGrabber.SaveFrameFromVideo(_videopath, 0.1d, _imagepath); it work perfectly is the video file is from my own computer, but when i try to get video file from remote location it not getting the frame. well, all the example is for windwos form app and i trying to use this for web-application. is there maybe an additional coding that enable me to use jockersoft to grab a video frame from remote location? here is the error that i got: Attempted to access an unloaded appdomain. (Exception from HRESULT: 0x80131014) Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.AppDomainUnloadedException: Attempted to access an unloaded appdomain. (Exception from HRESULT: 0x80131014) New Learner, please guide me..

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• Keeping user data persistent after validates_presence_of

  - by mathee

  I'm designing a question-and-answer Ruby on Rails application. After a user logs in, you can see a list of questions posed by other users. I have a link next to each of the questions to /answers/new?question_id=someNumber. That links to a page that displays the question (to remind the "answerer") above a standard form for submitting your answer. In order to display the question, I call @question = Question.find_by_id(params[:question_id]) and reference @question in the Haml view file: Question details %h2 #{h @question.title} #{h @question.description} %br/ %br/ %h1 Your answer - form_for(@answer) do |f| = f.error_messages %p = f.label :description, "Enter your response here" %br = f.text_area :description = f.hidden_field "question", :value => @question.id %p = f.submit 'Answer' The problem is that if I check validates_presence_of :description in Answer.rb, then I lose question_id if the user did not input anything into the description field when the page reloads, so I can't re-display the question for which the user is answering. How should I fix this? Is there a better way of storing the question the user is trying to answer so that I can display it above the form for entering a new answer (and perhaps in other views in the future)? If you need to see more code, please let me know.

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• Inner or Outer left Join

  - by user1557856

  I'm having difficulty modifying a script for this situation and wondering if someone maybe able to help: I have an address table and a phone table both sharing the same column called id_number. So id_number = 2 on both tables refers to the same entity. Address and phone information used to be stored in one table (the address table) but it is now split into address and phone tables since we moved to Oracle 11g. There is a 3rd table called both_ids. This table also has an id_number column in addition to an other_ids column storing SSN and some other ids. Before the table was split into address and phone tables, I had this script: (Written in Sybase) INSERT INTO sometable_3 ( SELECT a.id_number, a.other_id, NVL(a1.addr_type_code,0) home_addr_type_code, NVL(a1.addr_status_code,0) home_addr_status_code, NVL(a1.addr_pref_ind,0) home_addr_pref_ind, NVL(a1.street1,0) home_street1, NVL(a1.street2,0) home_street2, NVL(a1.street3,0) home_street3, NVL(a1.city,0) home_city, NVL(a1.state_code,0) home_state_code, NVL(a1.zipcode,0) home_zipcode, NVL(a1.zip_suffix,0) home_zip_suffix, NVL(a1.telephone_status_code,0) home_phone_status, NVL(a1.area_code,0) home_area_code, NVL(a1.telephone_number,0) home_phone_number, NVL(a1.extension,0) home_phone_extension, NVL(a1.date_modified,'') home_date_modified FROM both_ids a, address a1 WHERE a.id_number = a1.id_number(+) AND a1.addr_type_code = 'H'); Now that we moved to Oracle 11g, the address and phone information are split. How can I modify the above script to generate the same result in Oracle 11g? Do I have to first do INNER JOIN between address and phone tables and then do a LEFT OUTER JOIN to both_ids? I tried the following and it did not work: Insert Into.. select ... FROM a1. address INNER JOIN t.Phone ON a1.id_number = t.id_number LEFT OUTER JOIN both_ids a ON a.id_number = a1.id_number WHERE a1.adrr_type_code = 'H'

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• PDF search on the iPhone

  - by pt2ph8

  After two days trying to read annotations from a PDF using Quartz, I've managed to do it and posted my code. Now I'd like to do the same for another frequently asked question: searching PDF documents with Quartz. Same situation as before, this question has been asked many times with almost no practical answers. So I need some pointers first, as I still haven't implemented this myself. What I tried: I tried using CGPDFScannerScan handling the TJ and Tj operators - returns the right text on some PDF, whereas on other documents it returns mostly random letters. Maybe it's related to text encoding? Someone pointed out that text blocks (marked by BT/ET operators) should be handled instead, but I still haven't managed to do so. Anyone managed to extract text from any PDF? After that, searching should be easy by storing all the text in a NSMutableString and using rangeOfString (if there's a better way please let me know). But then how to highlight the result? I know there are a few operators to find the glyph sizes, so I could calculate the resulting rect based on those values, but I've been reading the spec for hours... it's a bloated mess and I'm going insane. Anyone with a practical explanation? Thanks.

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• Confusion in MIPS code

  - by Haya Hallian

  While going through the MIPS code I got some confusion. Code is shown as follows .data key: .ascii "key: " # "key: \n" char: .asciiz " \n" .text .globl main main: jal getchar la $a0, char # $a0 contains address of char variable (" \n") sb $v0, ($a0) # replace " " in char with v0, which is read_character (X) la $a0, key # now a0 will contain, address of "key: " "X\n" What I dont understand is that how load address instruction works. First a0 contained address of char variable. In next line we are storing value of v0 in that location. there is no offset with ($a0), is that assumed to be 0 like in 0($a0)? Why only the " " empty space is replaced with v0, and why not the "\n" get replaced? or It may also have been the case that both the empty space and \n character get replced by v0. Secondly when we load the address of key in a0, the previous address should be overwritten. a0 should have contained the address of key only, but from comment it seems that the two strings are concatenated. How does that happen.

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• How to use Node.js to build pages that are a mix between static and dynamic content?

  - by edt

  All pages on my 5 page site should be output using a Node.js server. Most of the page content is static. At the bottom of each page, there is a bit of dynamic content. My node.js code currently looks like: var http = require('http'); http.createServer(function (request, response) { console.log('request starting...'); response.writeHead(200, { 'Content-Type': 'text/html' }); var html = '<!DOCTYPE html><html><head><title>My Title</title></head><body>'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some more static content'; html += 'Some dynamic content'; html += '</body></html>'; response.end(html, 'utf-8'); }).listen(38316); I'm sure there are numerous things wrong about this example. Please enlighten me! For example: How can I add static content to the page without storing it in a string as a variable value with += numerous times? What is the best practices way to build a small site in Node.js where all pages are a mix between static and dynamic content?

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• Fast find object by string property

  - by Andrew Kalashnikov

  Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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• C# SQL Data Adapter Fill on existing typed Dataset

  - by René

  I have an option to choose between local based data storing (xml file) or SQL Server based. I already created a long time ago a typed dataset for my application to save data local in the xml file. Now, I have a bool that changes between Server based version and local version. If true my application get the data from the SQL Server. I'm not sure but It seems that Sql Adapter's Fill Method can't fill the Data in my existing schema SqlCommand cmd = new SqlCommand("Select * FROM dbo.Categories WHERE CatUserId = 1", _connection); cmd.CommandType = CommandType.Text; _sqlAdapter = new SqlDataAdapter(cmd); _sqlAdapter.TableMappings.Add("Categories", "dbo.Categories"); _sqlAdapter.Fill(Program.Dataset); This should fill my data from dbo.Categories to Categories (in my local, typed dataset). but it doesn't. It creates a new table with the name "Table". It looks like it can't handle the existing schema. I can't figure it out. Where is the problem? btw. of course the database request I do isn't very useful that way. It's just a simplified version for testing...

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• Deterministic floating point and .NET

  - by code2code

  How can I guarantee that floating point calculations in a .NET application (say in C#) always produce the same bit-exact result? Especially when using different versions of .NET and running on different platforms (x86 vs x86_64). Inaccuracies of floating point operations do not matter. In Java I'd use strictfp. In C/C++ and other low level languages this problem is essentially solved by accessing the FPU / SSE control registers but that's probably not possible in .NET. Even with control of the FPU control register the JIT of .NET will generate different code on different platforms. Something like HotSpot would be even worse in this case... Why do I need it? I'm thinking about writing a real-time strategy (RTS) game which heavily depends on fast floating point math together with a lock stepped simulation. Essentially I will only transmit user input across the network. This also applies to other games which implement replays by storing the user input. Not an option are: decimals (too slow) fixed point values (too slow and cumbersome when using sqrt, sin, cos, tan, atan...) update state across the network like an FPS: Sending position information for hundreds or a few thousand units is not an option Any ideas?

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• How to translate the fields of a database model?

  - by Tõnis M

  I have some tables/models in a web app that will have multilingual content. For example a university, with it's description in a default language(english) and the user wants he can see the same information in another language( if the object has it's fields translated). If there were only a few languages then I would just add fields like name_en and name_de and so on, but the number of languages isn't fixed, so that' would create a mess. I could also just create a new object with the translated data but then foreign keys wouldn't work, and only some of the fields can be translated so that would create duplicate data. Storing the translations in a file and using gettext or something similar is also not an option since the objects fields can be translated by the website user, not only developers/admins. What would be the best way to design/architect such a database? Searching from the translated data should also be not too complex - as it should not require creating complex joins which would make the queries slower I'm using PostgreSQL and Ruby of Rails but I'm not looking for a technical solution but for a general idea how to design it.

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• Suitable data structures for saving files in localStorage (HTML5) ?

  - by WmasterJ

  It is nice when there isn't a DB to maintain and users to authenticate. My professor has asked me to convert a recent research project of his that uses Bespin and calculates errors made by users in a code editor as part of his research. The goal is to convert from MySQL to using HTML5 localStorage completely. Doesn't seem so hard to do, even though digging in his code might take some time. Question: I need to store files and state (last placement of cursor and active file). I have already done so by implementing the recommendations in another stackoverflow thread. But would like your input considering how to structure the content to use. My current solution Hashmap like solution with javascript objects: files = {}; // later, saving files[fileName] = data; And then storing in localStorage using some recommendations localStorage.setObject("files", files); // Note that setObject(key, data) does not exist but is added // using Storage.prototype.setObject = function() {... Currently I'm also considering using some type of numeric id. So that names can be changed without any hassle renaming the key in the hashmap. What is your opinion on the way it is solved and would you do it any differently?

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• Having to insert a record, then update the same record warrants 1:1 relationship design?

  - by dianovich

  Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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