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• "Work stealing" vs. "Work shrugging"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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• Divide a path into N sections using Java or PostgreSQL/PostGIS

  - by Guido

  Imagine a GPS tracking system that is following the position of several objects. The points are stored in a database (PostgreSQL + PostGIS). Each path is composed by a different number of points. That is the reason why, in order to compare a pair of paths, I need to divide every path in a set of 100 points. Do you know any PostGIS function that already implement this algorithm? I've not been able to find it. If not, I'd like to solve it using Java. In this case I'd like to know an efficient and easy to implement algorithm to divide a path into N points. The most simple example could be to divide this path into three points: position 1 : x=1, y=2 position 2 : x=1, y=3 And the result should be: position 1 : x=1, y=2 (starting point) position 2 : x=5, y=2.5 position 3 : x=9, y=3 (end point) Edit: By 'compare a pair of paths' I mean to calculate the distance between two paths. I plan to divide each path in 100 points, and sum the euclidean distance between each one of these points as the distance between the two paths.

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• How do ASP.NET MVC Routes work?

  - by Pure.Krome

  Hi folks, imagine i have the following route setup... public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", "{controller}/{action}/{id}", new { controller = "Home", action = "Index", id = "" } ); // Added custom route here! routes.MapRoute( "CatchAll", "{*catchall}," new { controller = "Error", action = "NotFound" } ); } nothing new - that's the default ASP.NET MVC1 RegisterRoutes method, with one custom route added. Now, if I goto the following url, i get a 404... http://whatever/Home/MissingActionMethod So there's no ActionMethod called MissingActionMethod in the HomeController. So, does this mean, if i goto the 1st route defined, above .. and fail to find an action .. do I then come back and try the second route? rinse-repeat? Or once i match a route, i then try and execute that route .. and if i fail (ie, find the action is missing) .. then .. bad luck? boomski? cheers!

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• using paypals html api is safe?

  - by ajsie

  im trying out paypals html api where you specify price, item_name, customer information and so on in the html: <form action="https://www.paypal.com/cgi-bin/webscr" method="post" id="payPalForm"> <input type="hidden" name="cmd" value="_cart" /> <input type="hidden" name="upload" value="1" /> <input type="hidden" name="no_note" value="1" /> <input type="hidden" name="business" value="[email protected]" /> <input type="hidden" name="currency_code" value="SEK" /> <input type="hidden" name="return" value="http://freelanceswitch.com/payment-complete/" /> <input type="hidden" name="tax_rate" value="25" /> <input type="hidden" name="item_name_1" value="Apple Macpro" /> <input type="hidden" name="item_number_1" value="01 - Product 1" /> <input type="hidden" name="amount_1" value="25000" /> <input type="hidden" name="item_name_2" value="Apple Macbook" /> <input type="hidden" name="item_number_2" value="02 - Product 2" /> <input type="hidden" name="amount_2" value="12500" /> <input type="hidden" name="item_name_3" value="Apple Macbook Air" /> <input type="hidden" name="item_number_3" value="03 - Product 3" /> <input type="hidden" name="amount_3" value="12500" /> <input type="submit" name="Submit" value="Submit" /> </form> when the user clicks submit it takes him/her to paypals payment page. but doesn't this mean that a hacker could change the order by manipulating the html code? i can´t figure out how paypal prevents this security problem.

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• Building a custom (dynamic) dataset and grid

  - by marko.ivanovski.nz

  Hi, I'm in the process of building a dynamic table in which you can add/remove rows & columns so it varies in size depending on what the user wants. Its purpose is to store properties for a product, but there can be from 1 to 10 different properties(columns) per product, and multiple instances(rows) of the product as well. Here's a screenshot of what I mean http://i40.tinypic.com/nbqkxc.jpg As you can see I need the structure to be completely up to the client which is where I'm getting stuck. I've started writing a custom DataSet that has "add column" & "add row" buttons, and have built a custom Table with Textboxes in each cell which builds from that dataset. I have no idea how to store the data on submit though, and to make it even more complex I need to store this in the database as a string which I think I can do by converting it to XML. Any help is appreciated, I think I just need a pointer in the right direction and am happy to do research from there. Thanks in advance. Marko

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• cannot override a concrete member without a third member that's overridden by both

  - by huynhjl

  What does the following error message mean? cannot override a concrete member without a third member that's overridden by both (this rule is designed to prevent ``accidental overrides''); I was trying to do stackable trait modifications. It's a little bit after the fact since I already have a hierarchy in place and I'm trying to modify the behavior without having to rewrite a lot of code. I have a base class called AbstractProcessor that defines an abstract method sort of like this: class AbstractProcessor { def onPush(i:Info): Unit } I have a couple existing traits, to implement different onPush behaviors. trait Pass1 { def onPush(i:Info): Unit = { ... } } trait Pass2 { def onPush(i:Info): Unit = { ... } } So that allows me to use new AbstractProcessor with Pass1 or new AbstractProcessor with Pass2. Now I would like to do some processing before and after the onPush call in Pass1 and Pass2 while minimizing code changes to AbstractProcessor and Pass1 and Pass2. I thought of creating a trait that does something like this: trait Custom extends AbstractProcessor { abstract override def onPush(i:Info): Unit = { // do stuff before super.onPush(i) // do stuff after } And using it with new AbstractProcessor with Pass1 with Custom and I got that error message.

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• Preferred way of application initialization

  - by lisak

  Do you guys have your own little framework for project startups ? I mean, every time one needs to do the same things at the beginning: Context initialization - ideally after arguments are processed. Sometimes without interactive user input, sometimes with input reader. Sometimes we need to load properties, sometimes not. Then we need to get a class out of context and run its method. Programming....programming until writing shell script to place everything on classpath. It's true that it differs according to the actual needs. But it seems to me, that I'm doing always almost the same, again and again from the scratch. Sometimes I realize that I'm postponing my work just because I don't want to do these annoying startups. It would be great if there was some kind of universal Main class doing reflection to specified bean, context initialization, argument parsing, interactive user input reading and have the programmer do the important things...All setup might be done via spring configuration. I think I'll have to do it by myself. I'd appreciate your ideas

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• Access 2007 file picker, replaces all rows with the same choice.

  - by SqlStruggle

  This code is from an Access 2007 project I've been struggling with. The actual mean part is the part where I should put something like "update only current form" DoCmd.RunSQL "Update Korut Set [PikkuKuva]=('" & varFile & "') ;" Could someone please help me with this?` If I use it now, it updates all the tables with the same file picked. Heres the whole code. ' This requires a reference to the Microsoft Office 11.0 Object Library. Dim fDialog As Office.FileDialog Dim varFile As Variant Dim filePath As String ' Set up the File dialog box. Set fDialog = Application.FileDialog(msoFileDialogFilePicker) With fDialog ' Allow the user to make multiple selections in the dialog box. .AllowMultiSelect = False ' Set the title of the dialog box. .Title = "Valitse Tiedosto" ' Clear out the current filters, and then add your own. .Filters.Clear .Filters.Add "All Files", "*.*" ' user picked at least one file. If the .Show method returns ' False, the user clicked Cancel. If .Show = True Then ' Loop through each file that is selected and then add it to the list box. For Each varFile In .SelectedItems DoCmd.SetWarnings True DoCmd.RunSQL "Update Korut Set [PikkuKuva]=('" & varFile & "') ;" Next Else MsgBox "You clicked Cancel in the file dialog box." End If End With

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• Refining data stored in SQLite - how to join several contacts?

  - by Krab

  Problem background Imagine this problem. You have a water molecule which is in contact with other molecules (if the contact is a hydrogen bond, there can be 4 other molecules around my water). Like in the following picture (A, B, C, D are some other atoms and dots mean the contact). A B . . O / \ H H . . C D I have the information about all the dots and I need to eliminate the water in the center and create records describing contacts of A-C, A-D, A-B, B-C, B-D, and C-D. Database structure Currently, I have the following structure in the database: Table atoms: "id" integer PRIMARY KEY, "amino" char(3) NOT NULL, (HOH for water or other value) other columns identifying the atom Table contacts: "acceptor_id" integer NOT NULL, (the atom near to my hydrogen, here C or D) "donor_id" integer NOT NULL, (here A or B) "directness" char(1) NOT NULL, (this should be D for direct and W for water-mediated) other columns about the contact, such as the distance Current solution (insufficient) Now, I'm going through all the contacts which have donor.amino = "HOH". In this sample case, this would select contacts from C and D. For each of these selected contacts, I look up contacts having the same acceptor_id as is the donor_id in the currently selected contact. From this information, I create the new contact. At the end, I delete all contacts to or from HOH. This way, I am obviously unable to create C-D and A-B contacts (the other 4 are OK). If I try a similar approach - trying to find two contacts having the same donor_id, I end up with duplicate contacts (C-D and D-C). Is there a simple way to retrieve all six contacts without duplicates? I'm dreaming about some one page long SQL query which retrievs just these six wanted rows. :-) It is preferable to conserve information about who is donor where possible, but not strictly necessary. Big thanks to all of you who read this question to this point.

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• How to exit an if clause

  - by Roman Stolper

  What sorts of methods exist for prematurely exiting an if clause? There are times when I'm writing code and want to put a break statement inside of an if clause, only to remember that those can only be used for loops. Lets take the following code as an example: if some_condition: ... if condition_a: # do something # and then exit the outer if block ... if condition_b: # do something # and then exit the outer if block # more code here I can think of one way to do this: assuming the exit cases happen within nested if statements, wrap the remaining code in a big else block. Example: if some_condition: ... if condition_a: # do something # and then exit the outer if block else: ... if condition_b: # do something # and then exit the outer if block else: # more code here The problem with this is that more exit locations mean more nesting/indented code. Alternatively, I could write my code to have the if clauses be as small as possible and not require any exits. Does anyone know of a good/better way to exit an if clause? If there are any associated else-if and else clauses, I figure that exiting would skip over them.

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• Development/runtime Licensing mechanism for a C# class library?

  - by Darryl

  I'm developing a .Net class library (a data provider) and I'm starting to think about how I would handle licensing the library to prospective purchasers. By licensing, I mean the mechanics of trying to prevent my library from being used by those who haven't purchased it, not the software license (i.e., Apache, Gnu, etc). I've never dealt with licensing, and in the past, I've always developed apps, not libraries. I don't want to make things difficult for my customers; know it is not possible to make it ironclad. Just some mechanism that gives me decent protection without making the customer jump through hoops or gnash their teeth. I think the mechanism would check for a valid license when the class is being used in development mode, and not in runtime mode (when the customer's software is released to their customers). I think libraries are typically sold per developer, but I'm not sure how that could be accomplished without making the mechanism odious for my customers; maybe that gets left to the honor system. I Googled this and found many approaches. Ideally, I'd like to do something that is generally accepted and common, the "right" way class libraries are licensed, if that exists, rather than making my customers deal with yet another license mechanism. A firm push in the right direction will be greatly appreciated!

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• JavaScript: count minimal length of characters in text, ignoring special codes inside

  - by ilnur777

  I want to ignore counting the length of characters in the text if there are special codes inside in textarea. I mean not to count the special codes characters in the text. I use special codes to define inputing smileys in the text. I want to count only the length of the text ignoring special code. Here is my approximate code I tried to write, but can't let it work: // smileys // ======= function smileys(){ var smile = new Array(); smile[0] = "[:rolleyes:]"; smile[1] = "[:D]"; smile[2] = "[:blink:]"; smile[3] = "[:unsure:]"; smile[4] = "[8)]"; smile[5] = "[:-x]"; return(smile); } // symbols length limitation // ========================= function minSymbols(field){ var get_smile = smileys(); var text = field.value; for(var i=0; i<get_smile.length; i++){ for(var j=0; j<(text.length); j++){ if(get_smile[i]==text[j]){ text = field.value.replace(get_smile[i],""); } } } if(text.length < 50){ document.getElementById("saveB").disabled=true; } else { document.getElementById("saveB").disabled=false; } } How the script should be in order to let it work? Thank you!

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• Find & Replace - using a Regex for this?

  - by Jack W-H

  Hey folks. Regexs make me cry, so, I came here for help. I'm looking for some tips on Find & Replace in Panic's Coda. I know the F&R is pretty advance but I'm just looking for the best way to do this. I'm trying to rewrite a 'template engine' (very basic) I have going on with a webapp I'm coding in PHP (CodeIgniter). Currently I'm calling my template like so: $this->load->view('subviews/template/headerview'); $this->load->view('subviews/template/menuview'); $this->load->view('subviews/template/sidebar'); $this->load->view('The-View-I-Want-To-Load'); // This is the important line $this->load->view('subviews/template/footerview'); However it's inefficient using five lines of code every time I want to load up a different page, in every different controller. So I rewrote it like this: $data['view'] = 'The-View-I-Want-To-Load'; $this->load->view('template',$data); That way if I need to make any major changes to the design it can easily be done from the template.php view file (which contains the header, menu, sidebar views etc. etc.). However I use the previous 5-lines all over the place in many different controllers and functions. So, my question is --- How can I find and replace the old template engine (5 lines of code) for the new one - substituting in the name of the view in the important, unique line for the one in $data['view]? Does that make any sense?! If not I'll try and rephrase! I mean, is there a way of doing this via a Regex or something? Or am I on completely the wrong lines here? Thanks for your help Jack

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• Simple way to embed an MP3 audio file in a (static) HTML file, starting to play at a specifc time?

  - by Marcel

  Hi all, I want to produce a simple, static HTML file, that has one or more embedded MP3 files in it. The idea is to have a simple mean of listening to specific parts of an mp3 file. On a single click on a visual element, the sound should start to play; However, not from the beginning of the file, but from a specified starting point in that file (and play to the end of the file). This should work all locally from the client's local filesystem, the HTML file and the MP3 files do not reside on a webserver. So, how to play the MP3 audio from a specific starting point? The solution I am looking for should be as simple as possible, while working on most browsers, including IE, Firefox and Safari. Note: I know the <embed> tag as described here, but this seems not to work with my target browsers. Also I have read about jPlayer and other Java-Script-based players, but since I have never coded some JavaScript, I would prefer a HTML-only solution, if possible.

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• Commit is VERY slow in my NHibernate / SQLite project

  - by Tom Bushell

  I've just started doing some real-world performance testing on my Fluent NHibernate / SQLite project, and am experiencing some serious delays when when I Commit to the database. By serious, I mean taking 20 - 30 seconds to Commit 30 K of data! This delay seems to get worse as the database grows. When the SQLite DB file is empty, commits happen almost instantly, but when it grows to 10 Meg, I see these huge delays. The database has 16 tables, averaging 10 columns each. One possible problem is that I'm storing a dozen or so IList members, but they are typically only 200 elements long. But this is a recent addition to Fluent NHibernate automapping, which stores each float in a single table row, so maybe that's a potential problem. Any suggestions on how to track this down? I suspect SQLite is the culprit, but maybe it's NHibernate? I don't have any experience with profilers, but am thinking of getting one. I'm aware of NHibernate Profiler - any recommendations for profilers that work well with SQLite? Here's the method that saves the data - it's just a SaveOrUpdate call and a Commit, if you ignore all the error handling and debug logging. public static void SaveMeasurement(object measurement) { Debug.WriteLine("\r\n---SaveMeasurement---"); // Get the application's database session var session = GetSession(); using (var transaction = session.BeginTransaction()) { try { session.SaveOrUpdate(measurement); } catch (Exception e) { throw new ApplicationException( "\r\n SaveMeasurement->SaveOrUpdate failed\r\n\r\n", e); } try { Debug.WriteLine("\r\n---Commit---"); transaction.Commit(); Debug.WriteLine("\r\n---Commit Complete---"); } catch (Exception e) { throw new ApplicationException( "\r\n SaveMeasurement->Commit failed\r\n\r\n", e); } } }

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• Access cost of dynamically created objects with dynamically allocated members

  - by user343547

  I'm building an application which will have dynamic allocated objects of type A each with a dynamically allocated member (v) similar to the below class class A { int a; int b; int* v; }; where: The memory for v will be allocated in the constructor. v will be allocated once when an object of type A is created and will never need to be resized. The size of v will vary across all instances of A. The application will potentially have a huge number of such objects and mostly need to stream a large number of these objects through the CPU but only need to perform very simple computations on the members variables. Could having v dynamically allocated could mean that an instance of A and its member v are not located together in memory? What tools and techniques can be used to test if this fragmentation is a performance bottleneck? If such fragmentation is a performance issue, are there any techniques that could allow A and v to allocated in a continuous region of memory? Or are there any techniques to aid memory access such as pre-fetching scheme? for example get an object of type A operate on the other member variables whilst pre-fetching v. If the size of v or an acceptable maximum size could be known at compile time would replacing v with a fixed sized array like int v[max_length] lead to better performance? The target platforms are standard desktop machines with x86/AMD64 processors, Windows or Linux OSes and compiled using either GCC or MSVC compilers.

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• Is a confirmation screen necessary for an order form?

  - by abeger

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

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• Space-saving character encoding for japanese?

  - by Constantin

  In my opinion a common problem: character encoding in combination with a bitmap-font. Most multi-language encodings have an huge space between different character types and even a lot of unused code points there. So if I want to use them I waste a lot of memory (not only for saving multi-byte text - i mean specially for spaces in my bitmap-font) - and VRAM is mostly really valuable... So the only reasonable thing seems to be: Using an custom mapping on my texture for i.e. UTF-8 characters (so that no space is waste). BUT: This effort seems to be same with use an own proprietary character encoding (so also own order of characters in my texture). In my specially case I got texture space for 4096 different characters and need characters to display latin languages as well as japanese (its a mess with utf-8 that only support generall cjk codepages). Had somebody ever a similiar problem (I really wonder, if not)? If theres already any approach? Edit: The same Problem is described here http://www.tonypottier.info/Unicode_And_Japanese_Kanji/ but it doesnt provide an real solution how to save these bitmapfont mappings to utf-8 space efficent. So any further help is welcome!

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• Calculating bounding box a certain distance away from a lat/long coordinate in Java

  - by Bryce Thomas

  Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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• Does using ReadDirectoryChangesW require administrator rights?

  - by Alex Jenter

  The MSDN says that using ReadDirectoryChangesW implies the calling process having the Backup and Restore priviliges. Does this mean that only process launched under administrator account will work correctly? I've tried the following code, it fails to enable the required privileges when running as a restricted user. void enablePrivileges() { enablePrivilege(SE_BACKUP_NAME); enablePrivilege(SE_RESTORE_NAME); } void enablePrivilege(LPCTSTR name) { HANDLE hToken; DWORD status; if (::OpenProcessToken(::GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &hToken)) { TOKEN_PRIVILEGES tp = { 1 }; if( ::LookupPrivilegeValue(NULL, name, &tp.Privileges[0].Luid) ) { tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; BOOL result = ::AdjustTokenPrivileges(hToken, FALSE, &tp, 0, NULL, NULL); verify (result != FALSE); status = ::GetLastError(); } ::CloseHandle(hToken); } } Am I doing something wrong? Is there any workaround for using ReadDirectoryChangesW from a non-administrator user account? It seems that the .NET's FileSystemWatcher can do this. Thanks!

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• SQL Alchemy MVC and cross controller joins

  - by Khorkrak

  When using SQL Alchemy for abstracting your data access layer and using controllers as the way to access objects from that abstraction layer, how should joins be handled? So for example, say you have an Orders controller class that manages Order objects such that it provides getOrder, saveOrder, etc methods and likewise a similar controller for User objects. First of all do you even need these controllers? Should you instead just treat SQL Alchemy as "the" thing for handling data access. Why bother with object oriented controller stuff there when you instead have a clean declarative way to obtain and persist objects without having to write SQL directly either. Well one reason could be that perhaps you may want to replace SQL Alchemy with direct SQL or Storm or whatever else. So having controller classes there to act as an intermediate layer helps limit what would need to change then. Anyway - back to the main question - so assuming you have these two controllers, now lets say you want the list of orders for a certain set of users meeting some criteria. How do you go about doing this? Generally you don't want the controllers crossing domains - the Orders controllers knows only about Orders and the User controller just about Users - they don't mess with each other. You also don't want to go fetch all the Users that match and then feed a big list of user ids to the Orders controller to go find the matching Orders. What's needed is a join. Here's where I'm stuck - that seems to mean either the controllers must cross domains or perhaps they should be done away with altogether and you simply do the join via SQL Alchemy directly and get the resulting User and / or Order objects as needed. Thoughts?

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• C# Delegate under the hood question.

  - by Ted

  Hi Guys I was doing some digging around into delegate variance after reading the following tquestion in SO. "delegate-createdelegate-and-generics-error-binding-to-target-method" (sorry not allowed to post more than one hyperlink as a newbie here!) I found a very nice bit of code from Barry kelly at https://www.blogger.com/comment.g?blogID=8184237816669520763&postID=2109708553230166434 Here it is (in a sugared-up form :-) using System; namespace ConsoleApplication4 { internal class Base { } internal class Derived : Base { } internal delegate void baseClassDelegate(Base b); internal delegate void derivedClassDelegate(Derived d); internal class App { private static void Foo1(Base b) { Console.WriteLine("Foo 1"); } private static void Foo2(Derived b) { Console.WriteLine("Foo 2"); } private static T CastDelegate<T>(Delegate src) where T : class { return (T) (object) Delegate.CreateDelegate( typeof (T), src.Target, src.Method, true); // throw on fail } private static void Main() { baseClassDelegate a = Foo1; // works fine derivedClassDelegate b = Foo2; // works fine b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though b(new Derived()); b = CastDelegate<derivedClassDelegate>(a); // the hard way, avoids indirection b(new Derived()); } } } I understand all of it except this one (what looks very simple) line. b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though Can anyone tell me: how it is possible to call invoke without passing the param required by the static function. When is going on under the hood when you assign the return value from calling invoke What does Barry mean by extra indirection (in his comment)

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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• Inside what the TexBox value is posted back? ViewState or post back data?

  - by burak ozdogan

  In one article I was reading on ViewState, I saw a sentence saying that I should not fall into a mistake to believe that the value of a TextBox is stored in ViewState; it is stored in PostBack data. From here what I understand is when I post back a web form, the input controls values are stored in HTTP Request body. Not in the Viewstate. But as far as I know ViewState values are stored in an hidden field called __VIEWSTATE anyway. Then does it mean that __VIEVSTATE value is not posted in HTTP POST Request body as a postback data? Sounds nonesense to me. In another words, basically if I say the ViewState mechanism for such scenerio works like this, am I seeing it right or skipping something: You enter a value on an empty TextBox and submit the page The value of text box is posted back inside POST HTTP Request body. Nothing inside __VIEWSTATE at this point from the TextBox On the server side, the TextBox is created with the default value on OnInit method of the page The TrackChange property of ViewState is set to true. The posted back data of TextBox is loaded. Because it is different than the TextBox defalut value(because the user entered something), the ViewState of this text box is marked as DIRTY. The new value of the textbox is written into __VIEWSTATE hidden field From now on __VIEWSTATE hiddenfeild contains the last given value of the TextBox The page is sent to the user's browser having the __VIEWSTATE hidden field. But this time containing the last value entered by user which will be ready to be rendered Thanks guys! burak ozdogan

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