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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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  • Malloc inside another function (ANSI C)

    - by Casper
    Hi I'll go straight to it. I'm working on an assignment, where I suddenly ran into trouble. I have to allocate a struct from within another function, obviously using pointers. I've been staring at this problem for hours and tried in a million different ways to solve it. This is some sample code (very simplified): ... some_struct s; printf("Before: %d\n", &s"); allocate(&s); printf("After: %d\n", &s"); ... /* The allocation function */ int allocate(some_struct *arg) { arg = malloc(sizeof(some_struct)); printf("In function: %d\n", &arg"); return 0; } This does give me the same address before and after the allocate-call: Before: -1079752900 In function: -1079752928 After: -1079752900 I know it's probably because it makes a copy in the function, but I don't know how to actually work on the pointer I gave as argument. I tried defining some_struct *s instead of some_struct s, but no luck. I tried with: int allocate(some_struct **arg) which works just fine (the allocate-function needs to be changed as well), BUT according to the assignment I may NOT change the declaration, and it HAS to be *arg.. And it would be most correct if I just have to declare some_struct s.. Not some_struct *s. I hope I make sense and some of you out there can help me :P Thanks in advice

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  • Creating a Facebook session for getting page info

    - by Marty Haught
    I am trying to get info on a page that my user is admin for. This user has granted my fb_connect app offline access. I have saved the session_key that allows offline access (it has the user's id in it). I am able to publish to this fan page with this session key. But when I try to access the page's info I get an SessionExpired error. This doesn't make sense. Look at the code and output below: p is is a 'profile' object that holds the three pieces of relevant fb data (user_id, session_key and page id) fb_session = Facebooker::Session.create = # fb_session.secure_with!(p.fb_session_key, p.fb_user_id, 0) = nil fb_session.user.has_permission?("offline_access") = true fb_session.user.has_permission?("publish_stream") = true fb_session.user.has_permission?("read_stream") = true pages = fb_session.fql_query("select fan_count from page where page_id = #{p.fb_page_id}") Facebooker::Session::SessionExpired: Session key invalid or no longer valid ... pages = fb_session.pages(:fields = {:page_ids = p.fb_page_id}) Facebooker::Session::SessionExpired: Session key invalid or no longer valid ... pages = Facebooker::Session.create.fql_query("select fan_count from page where page_id = #{p.fb_page_id}") = [#] Perhaps I'm not creating the session right or maybe offline access doesn't give me access to the user's page even though I have permissions to push to it. As you can see when I just use an anon session I'm able to get the fan count, which I'm guessing is publicly available. Does anyone have an idea on this?

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  • Get current PHP executable from within script?

    - by benizi
    I want to run a PHP cli program from within PHP cli. On some machines where this will run, both php4 and php5 are installed. If I run the outer program as php5 outer.php I want the inner script to be run with the same php version. In Perl, I would use $^X to get the perl executable. It appears there's no such variable in PHP? Right now, I'm using $_SERVER['_'], because bash (and zsh) set the environment variable $_ to the last-run program. But, I'd rather not rely on a shell-specific idiom. UPDATE: Version differences are but one problem. If PHP isn't in PATH, for example, or isn't the first version found in PATH, the suggestions to find the version information won't help. Additionally, csh and variants appear to not set the $_ environment variable for their processes, so the workaround isn't applicable there. UPDATE 2: I was using $_SERVER['_'], until I discovered that it doesn't do the right thing under xargs (which makes sense... zsh sets it to the command it ran, which is xargs, not php5, and xargs doesn't change the variable). Falling back to using: $version = explode('.', phpversion()); $phpcli = "php{$version[0]}";

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  • How to scan convert right edges and slopes less than one?

    - by Zachary
    I'm writing a program which will use scan conversion on triangles to fill in the pixels contained within the triangle. One thing that has me confused is how to determine the x increment for the right edge of the triangle, or for slopes less than or equal to one. Here is the code I have to handle left edges with a slope greater than one (obtained from Computer Graphics: Principles and Practice second edition): for(y=ymin;y<=ymax;y++) { edge.increment+=edge.numerator; if(edge.increment>edge.denominator) { edge.x++; edge.increment -= edge.denominator; } } The numerator is set from (xMax-xMin), and the denominator is set from (yMax-yMin)...which makes sense as it represents the slope of the line. As you move up the scan lines (represented by the y values). X is incremented by 1/(denomniator/numerator) ...which results in x having a whole part and a fractional part. If the fractional part is greater than one, then the x value has to be incremented by 1 (as shown in edge.incrementedge.denominator). This works fine for any left handed lines with a slope greater than one, but I'm having trouble generalizing it for any edge, and google-ing has proved fruitless. Does anyone know the algorithm for that?

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  • Beyond the @Produces annotation, how does Jersey (JAX-RS) know to treat a POJO as a specific mime ty

    - by hal10001
    I see a lot of examples for Jersey that look something like this: public class ItemResource { @GET @Path("/items") @Produces({"text/xml", "application/json"}) public List<Item> getItems() { List<Item> items = new ArrayList<Item>(); Item item = new Item(); item.setItemName("My Item Name!"); items.add(item); return items; } } But then I have trouble dissecting Item, and how Jersey knows how to translate an Item to either XML or JSON. I've seen very basic examples that just return a String of constructed HTML or XML, which makes more sense to me, but I'm missing the next step. I looked at the samples, and one of them stood out (the json-from-jaxb sample), since the object was marked with these types of annotations: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "", propOrder = { "flight" }) @XmlRootElement(name = "flights") I'm looking for tutorials that cover this "translation" step-by-step, or an explanation here of how to translate a POJO to output as a specific mime type. Thanks!

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  • Hadoop Map/Reduce - simple use example to do the following...

    - by alexeypro
    I have MySQL database, where I store the following BLOB (which contains JSON object) and ID (for this JSON object). JSON object contains a lot of different information. Say, "city:Los Angeles" and "state:California". There are about 500k of such records for now, but they are growing. And each JSON object is quite big. My goal is to do searches (real-time) in MySQL database. Say, I want to search for all JSON objects which have "state" to "California" and "city" to "San Francisco". I want to utilize Hadoop for the task. My idea is that there will be "job", which takes chunks of, say, 100 records (rows) from MySQL, verifies them according to the given search criteria, returns those (ID's) which qualify. Pros/cons? I understand that one might think that I should utilize simple SQL power for that, but the thing is that JSON object structure is pretty "heavy", if I put it as SQL schemas, there will be at least 3-5 tables joins, which (I tried, really) creates quite a headache, and building all the right indexes eats RAM faster than I one can think. ;-) And even then, every SQL query has to be analyzed to be utilizing the indexes, otherwise with full scan it literally is a pain. And with such structure we have the only way "up" is just with vertical scaling. But I am not sure it's the best option for me, as I see how JSON objects will grow (the data structure), and I see that the number of them will grow too. :-) Help? Can somebody point me to simple examples of how this can be done? Does it make sense at all? Am I missing something important? Thank you.

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  • C# naming convention for enum and matching property

    - by Serge - appTranslator
    Hi All, I often find myself implementing a class maintaining some kind of own status property as an enum: I have a Status enum and ONE Status property of Status type. How should I solve this name conflict? public class Car { public enum Status { Off, Starting, Moving }; Status status = Status.Off; public Status Status // <===== Won't compile ===== { get { return status; } set { status = value; DoSomething(); } } } If the Status enum were common to different types, I'd put it outside the class and the problem would be solved. But Status applies to Car only hence it doesn't make sense to declare the enum outside the class. What naming convention do you use in this case? NB: This question was partially debated in comments of an answer of this question. Since it wasn't the main question, it didn't get much visibility. EDIT: Filip Ekberg suggests an IMO excellent workaround for the specific case of 'Status'. Yet I'd be interesting to read about solutions where the name of the enum/property is different, as in Michael Prewecki's answer. EDIT2 (May 2010): My favorite solution is to pluralize the enum type name, as suggested by Chris S. According to MS guidelines, this should be used for flag enums only. But I've come to like it more and more. I now use it for regular enums as well.

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  • Find all cycles in graph, redux

    - by Shadow
    Hi, I know there are a quite some answers existing on this question. However, I found none of them really bringing it to the point. Some argue that a cycle is (almost) the same as a strongly connected components (s. http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) , so one could use algorithms designed for that goal. Some argue that finding a cycle can be done via DFS and checking for back-edges (s. boost graph documentation on file dependencies). I now would like to have some suggestions on whether all cycles in a graph can be detected via DFS and checking for back-edges? My opinion is that it indeed could work that way as DFS-VISIT (s. pseudocode of DFS) freshly enters each node that was not yet visited. In that sense, each vertex exhibits a potential start of a cycle. Additionally, as DFS visits each edge once, each edge leading to the starting point of a cycle is also covered. Thus, by using DFS and back-edge checking it should indeed be possible to detect all cycles in a graph. Note that, if cycles with different numbers of participant nodes exist (e.g. triangles, rectangles etc.), additional work has to be done to discriminate the acutal "shape" of each cycle.

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  • Listing directories in Linux from C

    - by nunos
    I am trying to simulate linux command ls using linux api from c. Looking at the code it does make sense, but when I run it I get "stat error: No such file or directory". I have checked that opendir is working ok. I think the problem is in stat, which is returning -1 even though I think it should return 0. What am I missing? Thanks for your help. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <dirent.h> #include <sys/stat.h> #include <errno.h> int main(int argc, char *argv[]) { DIR *dirp; struct dirent *direntp; struct stat stat_buf; char *str; if (argc != 2) { fprintf( stderr, "Usage: %s dir_name\n", argv[0]); exit(1); } if ((dirp = opendir( argv[1])) == NULL) { perror(argv[1]); exit(2); } while ((direntp = readdir( dirp)) != NULL) { if (stat(direntp->d_name, &stat_buf)==-1) { perror("stat ERROR"); exit(3); } if (S_ISREG(stat_buf.st_mode)) str = "regular"; else if (S_ISDIR(stat_buf.st_mode)) str = "directory"; else str = "other"; printf("%-25s - %s\n", direntp->d_name, str); } closedir(dirp); exit(0); }

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  • passive view and display logic

    - by genesys
    Hi! In MVC and MVP and similar patterns there's often the approach of the "passive view" which is as stupid as possible. This should facilitate unit testing and create a clearer separation of view and model. I know that those patterns come in very different flavours and especially the understanding of MVP seems to differ from article to article. Therefore my question is not "how do i implement this pattern correctly". I want to improve view and model separation and go for better testability of the application. Therefore i'd like to go for a passive view. But my question is, where would you put logic that is clearly only view related? like a textviewer should scroll the text when the scrollbar is moved. would you put the logic for this into the Presenter? Let's say the textviewer has some extended functionality. like setting markings on textpassages. The logic for this makes clearly sense to be put into the Presenter. However, if it is mixed with all the 'direct' logic of the view (like scrolling the text) the Presenter could become very big, which is also not really a nice design. So my question is where to put display related logic of a passive view and what functionallity to mix in the Presenter. Thanks!

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  • Email as a view.

    - by Hal
    I've been in some discussion recently about where email (notifications, etc...) should be sent in an ASP.NET MVC application. My nemesis grin argues that it only makes sense that the email should be sent from the controller. I argue that an email is simply an alternate or augmented view through a different channel. Much like I would download a file as the payload of an ActionResult, the email is simply delivered through a different protocol. I've worked an extension method that allows me to do the following: <% Html.RenderEmail(model.FromAddress, model.ToAddress, model.Subject); %> which I actually include within my the view that is displayed on the screen. The beauty is that, based on convention, if I call RenderEmail from a parent view named MyView.ascx, I attempt to render the contents of a view named MyViewEmail.ascx, unless it is not found, in which case I simply email a copy of parent view. It certainly does make it testable (I still have an ISMTPService injected for testing), I wondered if anyone had any thoughts on whether or not this breaks from good practice. In use it has been extremely handy when we needed to easily send an email or modify the contents of the emailed results vs the browser rendered results. Thanks, Hal

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  • Java: attributes order in .jsp getting inversed

    - by NoozNooz42
    Every single time I've read about the meta tags, the attribute where in this order for the description: <meta name="description" content="..." /> First name, then content. It's also like that in the Google Webmaster documentation. Basically, it's like that everywhere. Now in a .jsp (in XML notation) I've got the following: <meta name="description" content="${metadesc}"/> So it's name first, then content. Yet on the generated webpage, I get this: <meta content="...(200 chars or so here making it a very long line)..." name="description"/> Somehow the attributes have been inversed. Because the content follows the official W3C and Google recommendations, the content is a bit less than 200 characters long, which makes it a major pain to "visually verify" that the name attribute is correctly there (I've got to scroll). Anyway... Why are these attribute not appearing in the order defined in the .jsp? Can I force them to appear in the same order as I wrote them in my .jsp? I realize the resulting tag may be valid... But I can also imagine a lot of very creative ways to have valid tags which users would be very upset about. Does this make any sense to inverse these attributes? EDIT wow, just wow... If I invert the attributes in my .jsp (that is, writing them in the "wrong" order), then they appear as I want them to appear in the generated web page. (Tomcat 6.0.26 btw)

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

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

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  • Why is MySQL with InnoDB doing a table scan when key exists and choosing to examine 70 times more ro

    - by andysk
    Hello, I'm troubleshooting a query performance problem. Here's an expected query plan from explain: mysql> explain select * from table1 where tdcol between '2010-04-13:00:00' and '2010-04-14 03:16'; +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ | 1 | SIMPLE | table1 | range | tdcol | tdcol | 8 | NULL | 5437848 | Using where | +----+-------------+--------------------+-------+---------------+--------------+---------+------+---------+-------------+ 1 row in set (0.00 sec) That makes sense, since the index named tdcol (KEY tdcol (tdcol)) is used, and about 5M rows should be selected from this query. However, if I query for just one more minute of data, we get this query plan: mysql> explain select * from table1 where tdcol between '2010-04-13 00:00' and '2010-04-14 03:17'; +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ | 1 | SIMPLE | table1 | ALL | tdcol | NULL | NULL | NULL | 381601300 | Using where | +----+-------------+--------------------+------+---------------+------+---------+------+-----------+-------------+ 1 row in set (0.00 sec) The optimizer believes that the scan will be better, but it's over 70x more rows to examine, so I have a hard time believing that the table scan is better. Also, the 'USE KEY tdcol' syntax does not change the query plan. Thanks in advance for any help, and I'm more than happy to provide more info/answer questions.

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  • QPainter declared inside a run function creates artifact.

    - by yan bellavance
    I am rendering a QPixmap inside of a QThread. the code to paint is inside a function. If I declare the painter inside the drawChart function everything seems ok but if I declare the painter inside the run function the image is wrong in the sense that at the edge of a black and white area, the pixels at the interface are overlapped to give a grey. Does anyone know why this is so? Could it be because of the nature of the run function itself? //This is ok void RenderThread::run() { QImage image(resultSize, QImage::Format_RGB32); drawChart(&image); emit renderedImage(image, scaleFactor); } drawChart(&image){ QPainter painter(image); painter.doStuff()(; ... } //This gives a image that seems to have artifacts void RenderThread::run() { QImage image(resultSize, QImage::Format_RGB32); QPainter painter(image); drawChart(painter); emit renderedImage(image, scaleFactor); } drawChart(&painter){ painter.doStuff()(; ... }

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  • Facebook XFBML Like Button incompatible with FeatureLoader script?

    - by retailevolved
    Facebook gurus, I have been implementing the Facebook Like button for a number of clients lately. To enable the Like Button, the following script has to be run: <div id="fb-root"></div> <script> window.fbAsyncInit = function() { FB.init({appId: '<?php echo Mage::helper("evlike")->getLikeConfig("ev_facebook_app_id") ?>', 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> It seems that this is incompatible with the following include: <script src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US" type="text/javascript"></script> It would make sense as I believe that the FeatureLoader performs an initialization. Is this official now? I would ask in official Facebook forums but I get an error every time I attempt to do so...

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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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  • Test Views in ASP.NET MVC2 (ala RSpec)

    - by Dmitriy Nagirnyak
    Hi, I am really missing heavily the ability to test Views independently of controllers. The way RSpec does it. What I want to do is to perform assertions on the rendered view (where no controller is involved!). In order to do so I should provide required Model, ViewData and maybe some details from HttpContextBase (when will we get rid of HttpContext!). So far I have not found anything that allows doing it. Also it might heavily depend on the ViewEngine being used. List of things that views might contain are: Partial views (may be nested deeply). Master pages (or similar in other view engines). Html helpers generating links and other elements. Generally almost anything in a range of common sense :) . Also please note that I am not talking about client-side testing and thus Selenium is just not related to it at all. It is just plain .NET testing. So are there any options to actually do the testing of views? Thanks, Dmitriy.

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  • C function changes behaviour depending on whether it has a call to printf in it

    - by Daniel
    I have a function that processes some data and finds the threshold that classifies the data with the lowest error. It looks like this: void find_threshold(FeatureVal* fvals, sampledata* data, unsigned int num_samples, double* thresh, double* err, int* pol) { //code to calculate minThresh, minErr, minPol omitted printf("minThresh: %f, minErr: %f, minPol: %d\n", minThresh, minErr, minPol); *thresh = minThresh; *err = minErr; *pol = minPol; } Then in my test file I have this: void test_find_threshold() { //code to set up test data omitted find_threshold(fvals, sdata, 6, &thresh, &err, &pol); printf("Expected 5 got %f\n", thresh); assert(eq(thresh, 5.0)); printf("Expected 1 got %d\n", pol); assert(pol == 1); printf("Expected 0 got %f\n", err); assert(eq(err, 0.0)); } This runs and the test passes with the following output: minThresh: 5.000000, minErr: 0.000000, minPol: 1 Expected 5 got 5.000000 Expected 1 got 1 Expected 0 got 0.000000 However if I remove the call to printf() from find_threshold, suddenly the test fails! Commenting out the asserts so that I can see what gets returned, the output is: Expected 5 got -15.000000 Expected 1 got -1 Expected 0 got 0.333333 I cannot make any sense of this whatsoever.

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  • How do I get LongVarchar out param from SPROC in ADO.NET 2.0 with SQLAnywhere 10?

    - by todthomson
    Hi All, I have sproc 'up_selfassessform_view' which has the following parameters: in ai_eqidentkey SYSKEY in ai_acidentkey SYSKEY out as_eqcomments TEXT_STRING out as_acexplanation TEXT_STRING  -  which are domain objects - SYSKEY is 'integer' and TEXT_STRING is 'long varchar'. I can call the sproc fine from iSQL using the following code: create variable @eqcomments TEXT_STRING; create variable @acexamples TEXT_STRING; call up_selfassessform_view (75000146, 3, @eqcomments, @acexamples); select @eqcomments, @acexamples;  - which returns the correct values from the DB (so I know the SPROC is good). I have configured the out param in ADO.NET like so (which has worked up until now for 'integer', 'timestamp', 'varchar(255)', etc): SAParameter as_acexplanation = cmd.CreateParameter(); as_acexplanation.Direction = ParameterDirection.Output; as_acexplanation.ParameterName = "as_acexplanation"; as_acexplanation.SADbType = SADbType.LongVarchar; cmd.Parameters.Add(as_acexplanation); When I run the following code: SADataReader reader = cmd.ExecuteReader(); I receive the following error: Parameter[2]: the Size property has an invalid size of 0. Which (I suppose) makes sense... But the thing is, I don't know the size of the field (it's just "long varchar" it doesn't have a predetermined length - unlike varchar(XXX)). Anyhow, just for fun, I add the following: as_acexplanation.Size = 1000; and the above error goes away, but now when I call: as_acexplanation.Value i get back a string of length = 1000 which is just '\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0...' (\0 repeated 1000 times). So I'm really really stuck... Any help one this one would be much appreciated. Cheers! ;) Tod T.

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  • Updating nullability of columns in SQL 2008

    - by Shaul
    I have a very wide table, containing lots and lots of bit fields. These bit fields were originally set up as nullable. Now we've just made a decision that it doesn't make sense to have them nullable; the value is either Yes or No, default No. In other words, the schema should change from: create table MyTable( ID bigint not null, Name varchar(100) not null, BitField1 bit null, BitField2 bit null, ... BitFieldN bit null ) to create table MyTable( ID bigint not null, Name varchar(100) not null, BitField1 bit not null, BitField2 bit not null, ... BitFieldN bit not null ) alter table MyTable add constraint DF_BitField1 default 0 for BitField1 alter table MyTable add constraint DF_BitField2 default 0 for BitField2 alter table MyTable add constraint DF_BitField3 default 0 for BitField3 So I've just gone in through the SQL Management Studio, updating all these fields to non-nullable, default value 0. And guess what - when I try to update it, SQL Mgmt studio internally recreates the table and then tries to reinsert all the data into the new table... including the null values! Which of course generates an error, because it's explicitly trying to insert a null value into a non-nullable column. Aaargh! Obviously I could run N update statements of the form: update MyTable set BitField1 = 0 where BitField1 is null update MyTable set BitField2 = 0 where BitField2 is null but as I said before, there are n fields out there, and what's more, this change has to propagate out to several identical databases. Very painful to implement manually. Is there any way to make the table modification just ignore the null values and allow the default rule to kick in when you attempt to insert a null value?

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  • Strange problem with vectors.

    - by Catalin Dumitru
    I have a really strange problem with stl vectors in which the wrong destructor is called for the right object when I call the erase method if that makes any sense. My code looks something like this: for(vector<Category>::iterator iter = this->children.begin(); iter != this->children.end(); iter++) { if((*iter).item == item) { this->children.erase(iter); return; } ------------------------- } It's just a simple function that finds the element in the vector which has some item to be searched, and removes said element from the vector. My problem is than when the erase function is called, and thus the object which the iterator is pointing at is being destroyed, the wrong destructor is being called. More specific the destructor of the last element in the vector is being called, and not of the actual object being removed. Thus the memory is being removed from the wrong object, which will still be an element in the vector, and the actual object which is removed from the vector, still has all of it's memory intact. The costructor of the object looks like this: Category::Category(const Category &from) { this->name = from.name; for(vector<Category>::const_iterator iter = from.children.begin(); iter != from.children.end(); iter++) this->children.push_back((*iter)); this->item = new QTreeWidgetItem; } And the destructor Category::~Category() { this->children.clear(); if(this->item != NULL) { QTreeWidgetItem* parent = this->item->parent(); if(parent != NULL) parent->removeChild(this->item); delete this->item; } }

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  • What is ADO.NET?

    - by ChrisC
    I've written a few Access db's and used some light VBA, and had an OO class. Now I'm undertaking to write a C# db app. I've got VS and System.Data.SQLite installed and connected, and have entered my tables and columns, but that's where I'm stuck. I'm trying to find what info and tutorials I need to look for, but there are a lot of terms I don't understand and I don't know if or exactly how they apply to my project. I've read definitions for these terms (Wikipedia and elsewhere), but the definitions don't make sense to me because I don't know what they are or how they fit together or which ones are optional or not optional for my project. Some of the terms on the System.Data.SQLite website (I wanted to use System.Data.SQLite for my db). I figured my first step in my project would be to get the db and queries set up and tested. Please tell me if there are other pieces of this part of the puzzle I will need to know about, too. If I can figure out what's what, I can start looking for the tutorials I need. (btw, I know I don't want to use an ORM because my app is so simple, and because I want to keep from biting off too much too soon.) Thank you very much. SQLite.NET ADO.NET ADO.NET provider ADO.NET 2.0 Provider for SQLite SQLite Entity Framework SQLite Entity Framework provider

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  • jQuery : add css class to menu item based on browser scroller position

    - by antosha
    Hi, I have a menu: <ul class="menu-bottom"> <li id="m1" class="active"><a id="1" href="#"><span>Link 1</span></a></li> <li id="m2"><a id="2" href="#"><span>Link 2</span></a></li> <li id="m3"><a id="3" href="#"><span>Link 3</span></a></li> </ul> I want that depending of browser's scroller position, the "active" class goes the correct < li element. This is how I see it : if ($(document).height() == 500) { $('#m1').parent().addClass('active'). siblings().removeClass('active'); } if ($(document).height() == 1000) { $('#m2').parent().addClass('active'). siblings().removeClass('active'); } if ($(document).height() == 1500) { $('#m2').parent().addClass('active'). siblings().removeClass('active'); } I am not very familiar with jQuery Dimensions properties so this code doesn't make much sense, but I hope you get the idea. If someone could tell me how to make this work, it would be really cool. Thanks :)

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