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• How to manipulate *huge* amounts of data

  - by Alejandro

  Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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• automating hudson builds with ant throwing 403

  - by Christopher Dancy

  We have a hudson server which deploys builds. We have a few services which we want to be able to remotely tell hudson to deploy a certain build ... these services are using ant. So I'm trying to get it working but keeping getting a 403 response when giving a build number like so... <ac:post to="http://hostname:8080/hudson/job/test_release_indexes/build?" verbose="true" wantresponse="true"> <prop name="token" value="indexes"/> <prop name="BUILDNUMBER" value="0354"/> </ac:post> this throws the 403. I've also tried passing it props for the username and password like so ... <ac:post to="http://srulesre2:8080/hudson/job/test_dartmouth_indexes/build?" verbose="true" wantresponse="true"> <prop name="token" value="indexes"/> <prop name="BUILDNUMBER" value="0354"/> <prop name="username" value="test"/> <prop name="password" value="test"/> </ac:post> I've tried a hundred different variations on username and password ... like j_username and j_password or user and pass ... but nothing is working ... keep getting the same 403. And the username and password are valid because I can manually log in with admin privileges. Any ideas would be great

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• passing groups of properties from 1 class to another

  - by insanepaul

  I have a group of 13 properties in a class. I created a struct for these properties and passed it to another class. I need to add another 10 groups of these 13 properties. So thats 130 properties in total. What do I do? I could add all 130 properties to the struct. Will this affect performance and readability I could create a list of structs but don't know how to access an item eg. to add to the list: listRowItems.Add(new RowItems(){a=1, b=1, c=1, d=1...}); listRowItems.Add(new RowItems(){a=2, b=2, c=2, d=2...}); How do I access the second group item b? is it Could I use just a dictionary with 130 items Should I use a list of dictionaries (again I don't know how to access a particular item) Should I pass in a class of 130 properties Just for your interest the properties are css parameters used for a composite control. The control displays 13 elements in each row and there are 10 rows and each row is customisable.

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• g++ linker can't find const member function

  - by Max

  I have a Point class (with integer members x and y) that has a member function withinBounds that is declared like so: bool withinBounds(const Point&, const Point&) const; and defined like this: bool Point::withinBounds(const Point& TL, const Point& BR) const { if(x < TL.getX()) return false; if(x > BR.getX()) return false; if(y < TL.getY()) return false; if(y > BR.getY()) return false; // Success return true; } and then in another file, I call withinBounds like this: Point pos = currentPlayer->getPosition(); if(pos.withinBounds(topleft, bottomright)) { // code block } This compiles fine, but it fails to link. g++ gives me this error: /home/max/Desktop/Development/YARL/yarl/src/GameData.cpp:61: undefined reference to 'yarl::utility::Point::withinBounds(yarl::utility::Point const&, yarl::utility::Point const&)' When I make the function not const, it links fine. Anyone know the reason why? The linker error looks like it's looking for a non-const version of the function, but I don't know why it would.

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• Force a view change from a button when using UITabBarController

  - by user342197

  Hello - When using a UITabBarController, when the user enters some data on View1 and presses a button, I need to perform some calculations and present the results on View2. I have an AppDelegate, View1Controller, View2Controller, and View3Controller (View3 is a basically static view). My AppDelgate declares UITabBarController *rootController; On View1, I have the calculations being performed in an IBAction for buttonPressed; however, I can't seem to force the view to switch to View2 programmatically. I have done a lot of searching for similar problems, and think I should be doing something like "self.rootController.selectedIndex = 1"; however,when I do this from within buttonPressed on my View1Controller, I get an error "request for member rootController in something not in a structure or union". I think I'm missing something basic here... probably need do do something with my AppDelegate, but I'm banging my head against the wall. Can anyone provide some guidance in this situation...like key things I should do in View1Controller header and implementation with reference to my AppDelgate? Thank you!

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• Cascading DropDown List in MVC 4

  - by Misi

  I have a ASP.NET MVC 4 project with EF I have a table with Parteners. This table has 2 types of parteners : agents(part_type=1) and clients(part_type=2). In an Create view I have the first DropDownList that shows all my agents, a button and the second DDL that shows all my clients that correspond to the selected agent. Q1 : What button shoud I use ? , , @Html.ActionLink() ? Create.cshtml <div class="editor-field"> @Html.DropDownList("idagenti", ViewData["idagenti"] as List<SelectListItem>, String.Empty) </div> @*a button*@ <div class="editor-label"> @Html.LabelFor(model => model.id_parten, "Client") </div> <div class="editor-field"> @Html.DropDownList("id_parten", String.Empty) @Html.ValidationMessageFor(model => model.id_parten) </div> OrdersController.cs public ActionResult Create(int? id) // id is the selected agent { var agqry = db.partener.Where(p => p.part_type == 1).Where(p => p.activ == true); var cltqry = db.partener.Where(p => p.part_type == 2).Where(p => p.activ == true); List<SelectListItem> idagenti = new List<SelectListItem>(); foreach (partener ag in agqry) { idagenti.Add(new SelectListItem { Text = ag.den_parten, Value = ag.id_parten.ToString() }); } if (id != null) { cltqry = cltqry.Where(p => p.par_parten == id); } ViewData["idagenti"] = idagenti; ViewBag.id_parten = new SelectList(cltqry, "id_parten", "den_parten");// } Q: How can I pass the selected agent id from the first DDL to my controller ?

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• How to include all objects of an archive in a shared object?

  - by Didier Trosset

  When compiling our project, we create several archives (static libraries), say liby.a and libz.a that each contains an object file defining a function y_function() and z_function(). Then, these archives are joined in a shared object, say libyz.so, that is one of our main distributable target. g++ -fPIC -c -o y.o y.cpp ar cr liby.a y.o g++ -fPIC -c -o z.o z.cpp ar cr libz.a z.o g++ -shared -L. -ly -lz -o libyz.so When using this shared object into the example program, say x.c, the link fails because of an undefined references to functions y_function() and z_function(). g++ x.o -L. -lyz -o xyz It works however when I link the final executable directly with the archives (static libraries). g++ x.o -L. -ly -lz -o xyz My guess is that the object files contained in the archives are not linked into the shared library because they are not used in it. How to force inclusion? Edit: Inclusion can be forced using --whole-archive ld option. But if results in compilation errors: g++ -shared '-Wl,--whole-archive' -L. -ly -lz -o libyz.so /usr/lib/libc_nonshared.a(elf-init.oS): In function `__libc_csu_init': (.text+0x1d): undefined reference to `__init_array_end' /usr/bin/ld: /usr/lib/libc_nonshared.a(elf-init.oS): relocation R_X86_64_PC32 against undefined hidden symbol `__init_array_end' can not be used when making a shared object /usr/bin/ld: final link failed: Bad value Any idea where this comes from?

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• error with std::ostringsteam and std::string

  - by pyCthon

  Hi i want to save many different csv files from a function with a naming convention based on a different double value. I do this with a for loop and pass a string value to save each .csv file differently. Below is an example of what I'm trying to do the desired result would be 1.1_file.csv 1.2_file.csv but instead i get 1.1_file.csv 1.11.2_file.csv Here is a working sample code, what can i do to fix this #include <sstream> #include <iomanip> #include <cmath> #include <iostream> #include <vector> int main(){ std::string file = "_file.csv"; std::string s; std::ostringstream os; double x; for(int i = 0; i < 10; i++){ x = 0.1 + 0.1 *i; os << std::fixed << std::setprecision(1); os << x; s = os.str(); std::cout<<s+file<<std::endl; s.clear(); } return 0; }

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• Loading a helper elsewhere than the autoload.php?

  - by drpcken

  I inherited a project and I'm cleaning up a bit and trying to finish it. I noticed that they used (or wrote) a breadcrumb helper. It is in my helpers folder and is named breadcrumb_helper.php It has a single function to build a breadcrumb menu with links and pass it to the view breadcrumbs.php. Here's the code: function show_breadcrumbs() { $ci =& get_instance(); $ci->load->helper('inflector'); $data = ''; //build breadcrumb and store in $data $this->load->view("breadcrumbs", $data) } I was trying to figure out how this helper worked and I checked the autoload.php but there is no reference to the helper in there. In face here is my autoload: $autoload['helper'] = array('url','asset','combine','navigation','form','portfolio','cookie','default'); This show_breadcrumbs() function is used quite a bit in some of my pages so I'm confused as to how its loading if it isn't in the autoloader. It is called like this in a few of my pages: <?=show_breadcrumbs()?> What am I missing? Why isn't this in my autoload? I even did a global search and couldn't find anywhere the helper is being loaded.

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• MySQL query pulling from two tables, display in correct fields

  - by Matt Nathanson

  I'm trying to select all fields in two separate tables as long as they're sharing a common ID. //mysql query $result = mysql_query("SELECT * FROM project, links WHERE project.id = links.id and project.id = $clientID") //displaying the link if ($row['url'] != null){ echo "<div class='clientsection' id='links'>Links</div>"; echo "<a class='clientlink' id='link1' href='" . $row['url'] . "'>" . $row['name'] . "</a>"; } else { echo "<a class='clientlink' id='link1' href='" . $row['url'] . "' style='display:none;'>" . $row['name'] . "</a>"; }; As you can see, my tables are "projects", and "links" Each is sharing a common field "id" for reference. It looks as though where both links.id and project.id are equal, it outputs anything, but when there is no links.id associated with a given $clientID the container relative to the $clientID doesn't display at all. Essentially I'm using this to add links dynamically to a specific client in this CMS and if there are no links, I want the container to show up anyway. Hopefully I've expressed myself clearly, any pointers in the right direction are appreciated. Thanks!

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• Facebook new js api and cross-domain file

  - by vondip

  Hi all, I am building a simple facebook iframe application. I've decided since the code is separate from facebook none the less, I will also create a connect website as well. In my connect website I'm trying to figure out the following: I am using facebook's new api and I am calling the init function. I can't seem to figure out where I combine my cross-domain file. There's no mention of it in their documentation either. http://developers.facebook.com/docs/reference/javascript/FB.init I am referring to these lines of code: <div id="fb-root"></div> <script> window.fbAsyncInit = function() { FB.init({appId: 'your app id', status: true, cookie: true, xfbml: true}); }; (function() { var e = document.createElement('script'); e.async = true; e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js'; document.getElementById('fb-root').appendChild(e); }()); </script>

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• Image resizing - sometimes very poor quality?!

  - by eWolf

  I'm resizing some images to the screen resolution of the user; if the aspect ratio is wrong, the image should be cut. My code looks like this: protected void ConvertToBitmap(string filename) { var origImg = System.Drawing.Image.FromFile(filename); var widthDivisor = (double)origImg.Width / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width; var heightDivisor = (double)origImg.Height / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height; int newWidth, newHeight; if (widthDivisor < heightDivisor) { newWidth = (int)((double)origImg.Width / widthDivisor); newHeight = (int)((double)origImg.Height / widthDivisor); } else { newWidth = (int)((double)origImg.Width / heightDivisor); newHeight = (int)((double)origImg.Height / heightDivisor); } var newImg = origImg.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero); newImg.Save(this.GetBitmapPath(filename), System.Drawing.Imaging.ImageFormat.Bmp); } In most cases, this works fine. But for some images, the result has an extremely poor quality. It looks like the would have been resized to something very small (thumbnail size) and enlarged again.. But the resolution of the image is correct. What can I do? Example orig image: Example resized image: Note: I have a WPF application but I use the WinForms function for resizing because it's easier and because I already need a reference to System.Windows.Forms for a tray icon.

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• JUnit confusion: use 'extend Testcase' or '@Test' ?

  - by Rabarberski

  I've found the proper use (or at least the documentation) of JUnit very confusing. This question serves both as a future reference and as a real question. If I've understood correctly, there are two main approaches to create and run a JUnit test: Approach A: create a class that extends TestCase, and start test methods with the word test. When running the class as a JUnit Test (in Eclipse), all methods starting with the word test are automatically run. import junit.framework.TestCase; public class DummyTestA extends TestCase { public void testSum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Approach B: create a 'normal' class and prepend a @Test annotation to the method. Note that you do NOT have to start the method with the word test. import org.junit.*; import static org.junit.Assert.*; public class DummyTestB { @Test public void Sum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Mixing the two seems not to be a good idea, see e.g. this stackoverflow question: Now, my questions(s): What is the preferred approach, or when would you use one instead of the other? Approach B allows for testing for exceptions by extending the @Test annotation like in @Test(expected = ArithmeticException.class). But how do you test for exceptions when using approach A? When using approach A, you can group a number of test classes in a test suite. TestSuite suite = new TestSuite("All tests");<br/> suite.addTestSuite(DummyTestA.class); suite.addTestSuite(DummyTestAbis.class);` But this can't be used with approach B (since each testclass should subclass TestCase). What is the proper way to group tests for approach B?

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• PHP: Next Available Value in an Array, starting with a non-indexed value

  - by Erik Smith

  I've been stumped on this PHP issue for about a day now. Basically, we have an array of hours formatted in 24-hour format, and an arbitrary value ($hour) (also a 24-hour). The problem is, we need to take $hour, and get the next available value in the array, starting with the value that immediately proceeds $hour. The array might look something like: $goodHours = array('8,9,10,11,12,19,20,21). Then the hour value might be: $hour = 14; So, we need some way to know that 19 is the next best time. Additionally, we might also need to get the second, third, or fourth (etc) available value. The issue seems to be that because 14 isn't a value in the array, there is not index to reference that would let us increment to the next value. To make things simpler, I've taken $goodHours and repeated the values several times just so I don't have to deal with going back to the start (maybe not the best way to do it, but a quick fix). I have a feeling this is something simple I'm missing, but I would be so appreciative if anyone could shed some light. Erik

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• Google App Engine, parsedatetime and TimeZones

  - by Ron

  Hey guys, I'm working on a Google App Engine / Django app and I encountered the following problem: In my html I have an input for time. The input is free text - the user types "in 1 hour" or "tomorrow at 11am". The text is then sent to the server in AJAX, which parses it using this python library: http://code.google.com/p/parsedatetime/. Once parsed, the server returns an epoch timestamp of the time. Here is the problem - Google App Engine always runs on UTC. Therefore, lets say that the local time is now 11am and the UTC time is 2am. When I send "now" to the server it will return "2am", which is good because I want the date to be received in UTC time. When I send "in 1 hour" the server will return "3am" which is good, again. However, when I send "at noon" the server will return "12pm" because it thinks that I'm talking about noon UTC - but really I need it to return 3am, which is noon for the request sender.. I can pass on the TZ of the browser that sends the request, but that wont really help me - the parsedatetime library wont take a timezone argument (correct me if I'm wrong). Is there a walk around this? Maybe setting the environments TZ somehow? Thanks!

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• How to stop Android GPS using "Mobile data"

  - by prepbgg

  My app requests location updates with "minTime" set to 2 seconds. When "Mobile data" is switched on (in the phone's settings) and GPS is enabled the app uses "mobile data" at between 5 and 10 megabytes per hour. This is recorded in the ICS "Data usage" screen as usage by "Android OS". In an attempt to prevent this I have unticked Settings-"Location services"-"Google's location service". Does this refer to Assisted GPS, or is it something more than that? Whatever it is, it seems to make no difference to my app's internet access. As further confirmation that it is the GPS usage by my app that is causing the mobile data access I have observed that the internet data activity indicator on the status bar shows activity when and only when the GPS indicator is present. The only way to prevent this mobile data usage seems to be to switch "Mobile data" off, and GPS accuracy seems to be almost as good without the support of mobile data. However, it is obviously unsatisfactory to have to switch mobile data off. The only permissions in the Manifest are "android.permission.ACCESS_FINE_LOCATION" (and "android.permission.WRITE_EXTERNAL_STORAGE"), so the app has no explicit permission to use internet data. The LocationManager code is ` criteria.setAccuracy(Criteria.ACCURACY_FINE); criteria.setSpeedRequired(false); criteria.setAltitudeRequired(false); criteria.setBearingRequired(true); criteria.setCostAllowed(false); criteria.setPowerRequirement(Criteria.NO_REQUIREMENT); bestProvider = lm.getBestProvider(criteria, true); if (bestProvider != null) { lm.requestLocationUpdates(bestProvider, gpsMinTime, gpsMinDistance, this); ` The reference for LocationManager.getBestProvider says If no provider meets the criteria, the criteria are loosened ... Note that the requirement on monetary cost is not removed in this process. However, despite setting setCostAllowed to false the app still incurs a potential monetary cost. What else can I do to prevent the app from using mobile data?

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• Load an html table from a mysql database when an onChange event is triggered from a select tag

  - by Crew Peace

  So, here's the deal. I have an html table that I want to populate. Specificaly the first row is the one that is filled with elements from a mysql database. To be exact, the table is a questionnaire about mobile phones. The first row is the header where the cellphone names are loaded from the database. There is also a select tag that has company names as options in it. I need to trigger an onChange event on the select tag to reload the page and refill the first row with the new names of mobiles from the company that is currently selected in the dropdown list. This is what my select almost looks like: <select name="select" class="companies" onChange="reloadPageWithNewElements()"> <?php $sql = "SELECT cname FROM companies;"; $rs = mysql_query($sql); while($row = mysql_fetch_array($rs)) { echo "<option value=\"".$row['cname']."\">".$row['cname']."</option>\n "; } ?> </select> So... is there a way to refresh this page with onChange and pass the selected value to the same page again and assign it in a new php variable so i can do the query i need to fill my table? <?php //$mobileCompanies = $_GET["selectedValue"]; $sql = "SELECT mname FROM ".$mobileCompanies.";"; $rs = mysql_query($sql); while ($row = mysql_fetch_array($rs)) { echo "<td><div class=\"q1\">".$row['mname']."</div></td>"; } ?> something like this. (The reloadPageWithNewElements() and selectedValue are just an idea for now)

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• Servlet Mapping Help - Possible to Avoid Referencing Context Name?

  - by AJ

  Hi all, I am working on a Spring application and trying to get my URL mapping correct. What I would like to have work is the following: http://localhost:8080/idptest -> doesn't work But instead, I have to reference the context name in my URL in order to resolve the mapping: http://localhost:8080/<context_name>/idptest -> works How can I avoid the requirement of referencing the context name in my URL without using a rewrite/proxy engine e.g. Apache? Here is the servlet definition and mapping from my web.xml: <servlet> <servlet-name>idptest</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/conf/idptest.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>idptest</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> Here's the outline of my controller (showing annotations for request mappings): @Controller @RequestMapping("/idptest") public class MyController { @RequestMapping(method=RequestMethod.GET) public String setupForm(Model model){ MyObject someObject = new MyObject(); model.addAttribute("someObject", someObject); return "myform"; } @RequestMapping(method = RequestMethod.POST) public String processSubmit(@ModelAttribute("someObject") MyObject someObject) throws Exception { // POST logic... } } Thanks!

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• C# class design - expose variables for reading but not setting

  - by James Brauman

  I have a a polygon class which stores a list of Microsoft.Xna.Framework.Vector2 as the vertices of the polygon. Once the polygon is created, I'd like other classes to be able to read the position of the vertices, but not change them. I am currently exposing the vertices through this field: /// <summary> /// Gets the vertices stored for this polygon. /// </summary> public List<Vector2> Vertices { get { return _vertices; } } List<Vector2> _vertices; However you can change any vertex using code like: Polygon1.Vertices[0] = new Vector2(0, 0); or Polygon1.Vertices[0].X = 0; How can I limit other classes to be able to only read the properties of these vertices, and not be able to set a new one to my List? The only thing I can think of is to pass a copy to classes that request it. Note that Vector2 is a struct that is part of the XNA framework and I cannot change it. Thanks.

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• Stored Procedure: Variable passed from PHP alters second half of query string

  - by Stephanie

  Hello everyone, Basically, we have an ASP website right now that I'm converting to PHP. We're still using the MSSQL server for the DB -- it's not moving. In the ASP, now, there's an include file with a giant sql query that's being executed. This include sits on a lot of pages and this is a simple version of what happens. Pages A, B and C all use this include file to return a listing. In ASP, Page A passes through variable A to the include file - page B passes through variable B -- page C passes through variable C, and so on. The include file builds the SQL query like this: sql = "SELECT * from table_one LEFT OUTER JOIN table_two ON table_one.id = table_two.id" then adds (remember, ASP), based on the variable passed through from the parent page, Select Case sType Case "A" sql = sql & "WHERE LOWER(column_a) <> 'no' AND LTRIM(ISNULL(column_b),'') <> '' ORDER BY column_a Case "B" sql = sql & "WHERE LOWER(column_c) <> 'no' ORDER BY lastname, firstname Case "C" sql = sql & "WHERE LOWER(column_f) <> 'no' OR LOWER(column_g) <> 'no' ORDER BY column_g As you notice, every string that's added on as the second part of the sql query is different than the previous; not just one variable can be substituted out, which is what has me stumped. How do I translate this case / switch into the stored procedure, based on the varchar input that I pass to the stored procedure via PHP? This stored procedure will actually handle a query listing for about 20 pages, so it's a hefty one and this is my first major complicated one. I'm getting there, though! I'm also just more used to MySQL, too. Not that they're that different. :P Thank you very much for your help in advance. Stephanie

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• how to implement a sparse_vector class

  - by Neil G

  I am implementing a templated sparse_vector class. It's like a vector, but it only stores elements that are different from their default constructed value. So, sparse_vector would store the index-value pairs for all indices whose value is not T(). I am basing my implementation on existing sparse vectors in numeric libraries-- though mine will handle non-numeric types T as well. I looked at boost::numeric::ublas::coordinate_vector and eigen::SparseVector. Both store: size_t* indices_; // a dynamic array T* values_; // a dynamic array int size_; int capacity_; Why don't they simply use vector<pair<size_t, T>> data_; My main question is what are the pros and cons of both systems, and which is ultimately better? The vector of pairs manages size_ and capacity_ for you, and simplifies the accompanying iterator classes; it also has one memory block instead of two, so it incurs half the reallocations, and might have better locality of reference. The other solution might search more quickly since the cache lines fill up with only index data during a search. There might also be some alignment advantages if T is an 8-byte type? It seems to me that vector of pairs is the better solution, yet both containers chose the other solution. Why?

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• Get Function Pointer to function in a shared library I didn't directly load

  - by bdk

  My Linux application (A) links against a Third Party shared Library (B) which I don't have source code to. This library makes use of another third party shared library that I don't have source code to (C). I believe that (B) uses dlopen to access (C) instead of directly linking. My reasoning for this is that 'ldd' on (B) does not show (C) and objdump -X (B) shows references to dlopen/dlclose/dlsym. My requirement is that I need to in my code for (A) get a function pointer to a function foo() located in (C). Normally I'd use dlsym for this, but I need to pass it the handle returned from dlopen which I don't have since (B) does not expose this. - For the larger context: I need to modify the function in (C) such that everytime it calls its helper function bar() (also located in (C)), it also calls a function with the same signature located in (A) with the same parameters (Basically inject my code into the codepath of (C) foo()-bar(). I believe I've found a way to accomplish this using gdb, but in order to port my gdb command list, but I'm stuck on the step of getting the function pointer. I'm also open to alternatives to accomplish the same task rather than the exact problem as stated above Edit: After writing this I realized I can probably just do another dlopen on the file in my code and the symbols returned via dlsym on that handle should be the same as received via the original dlopen, If I'm reading the dlopen man page correctly. However I'm still interested in advice or assistance with the my larger context, If theres a better way to go about this

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• Passing Derived Class Instances as void* to Generic Callbacks in C++

  - by Matthew Iselin

  This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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• should the builder reset its build environment after delivering the product

  - by Sudhi

  I am implementing a builder where in the deliverable is retrieved by calling Builder::getProduct() . The director asks various parts to build Builder::buildPartA() , Builder::buildPartB() etc. in order to completely build the product. My question is, once the product is delivered by the Builder by calling Builder::getProduct(), should it reset its environment (Builder::partA = NULL;, Builder::partB = NULL;) so that it is ready to build another product? (with same or different configuration?) I ask this as I am using PHP wherein the objects are by default passed by reference (nope, I don't want to clone them, as one of their field is a Resource) . However, even if you think from a language agnostic point of view, should the Builder reset its build environment ? If your answer is 'it depends on the case' what use cases would justify reseting the environment (and other way round) ? For the sake of providing code sample here's my Builder::gerProcessor() which shows what I mean by reseting the environment /** * @see IBuilder::getProessor() */ public function getProcessor() { if($this->_processor == NULL) { throw new LogicException('Processor not yet built!'); } else { $retval = $this->_processor; $this->_product = NULL, $this->_processor = NULL; } return $retval; }

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• SQL, MVC, Entity Framework

  - by Anthony

  Hi Im using the above technologies and have ran into what I presume is a design issue I have made. I have an Artwork table in my DB and have been able to add art (I now think of these as Digital Products) to a shopping cart + CartLine table fine. The system I have that adds art to galleries and user accounts etc works fine. Now the client wants to sell T-shirts, Mugs and Pens etc, 'HardwareProducts' so I have created a 'HardwareProducts' table. Now I have two different product types in two tables. I use GUID's as the PK's in both the HardwareProducts table and Artwork table. When a customer adds an item to their cart I store the GUID in the ProductID column in the CartItems table. The issue is the database will not know which table to reference when I bring the LineItem object up through my ORM to the front end. In OOP I can see how you would have a base class of Product, and then a DigitalProduct class and HardwareProduct class drived from it, but how do you model this in SQL Server and the Entity Framework please, or is there another way?

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