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  • Ruby and RSS2 Feed not displaying image

    - by pcasa
    Trying to create a simple RSS2 Feed that I could later pass on to FeedBurner but can't get RSS feed to display images at all. Also, from what I have read having xml.instruct! on top might cause IE to complain it's not a valid feed. Is this true? My Code looks like xml.instruct! xml.rss "version" => "2.0", "xmlns:dc" => "http://purl.org/dc/elements/1.1/" do xml.channel do xml.title "Store" xml.link url_for :only_path => false, :controller => 'products' xml.description "Store" xml.pubDate @products.first.updated_at.rfc822 if @products.any? @products.each do |product| xml.item do xml.title product.name xml.pubDate (product.updated_at.rfc822) xml.image do xml.url domain_host + product.product_image.url(:small) xml.title "Store" xml.link url_for :only_path => false, :controller => 'products' end xml.link url_for :only_path => false, :controller => 'products', :action => 'show', :id => product.permalink xml.description product.fine_print xml.guid url_for :only_path => false, :controller => 'products', :action => 'show', :id => product.permalink end end end end

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  • A simple way to put a UIImage in a UIButton

    - by Alice
    I have a UIButton in my iPhone app. I set its size to 100x100. I have an image that is 400x200 that I wish to display in the button. The button STILL needs to stay at 100x100... and I want the image to downsize to fit... but keep the correct aspect ratio. I thought that's what "Aspect Fit" was used for. Do I include my image with setImage, or setBackgroundImage? Do I set AspectFit for the button? or the image? or the background image? (I need the smaller images to INCREASE in size. While larger images should DESCREASE in size. Always keeping the button at 100x100.) I've tried countless combinations of all of the above... and I just can't seem to get everything to work at the same time: Don't change the button's size of 100x100. Don't destroy the image's aspect ratio. Always increase small images to fit the button. Always decrease large images to fit the button. Never clip any of the image edges. Never require the "put UIButtons over all your UIimages" hack. Don't require everyone to upgrade to v4.2.1 just to use new framework methods. I see so many apps, with so many fully-working image-buttons... that I can't believe I can't figure out this very simple, very common thing. Ugh.

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  • SqlCE DB occasionally freezes on one handheld, not another

    - by Michael
    I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database: Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb Type 1 will happily proceed through a large batch db operation (initiated) by the app, by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. As several points it will begin running normally and then crawl again. The app does several db op's (inserts, updates and selects, no deletes). To simplify my situation, I've built a small test app which essentially does this: command_s.CommandText = "select dvr from vr where vid = 2211250"; command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861"; while(going) { command_s.ExecuteScalar(); command_u.ExecuteNonQuery(); } and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit. What is causing this?

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  • SQL query to translate a list of numbers matched against several ranges, to a list of values

    - by Claes Mogren
    I need to convert a list of numbers that fall within certain ranges into a list of values, ordered by a priority column. The table has the following values: | YEAR | R_MIN | R_MAX | VAL | PRIO | ------------------------------------ 2010 18000 90100 52 6 2010 240000 240099 82 3 2010 250000 259999 50 5 2010 260000 260010 92 1 2010 330000 330010 73 4 2010 330011 370020 50 5 2010 380000 380050 84 2 The ranges will be different for different years. The ranges within one year will never overlap. The input will be a year and a list of numbers that might fall within one these ranges. The list of input number will be small, 1 to 10 numbers. Example of input numbers: (20000, 240004, 375000, 255000) With that input I would like to get a list ordered by the priority column, or a single value: 82 50 52 The only value I'm interested in here is 82, so UNIQUE and MAX_RESULTS=1 would do. It can easily be done with one query per number, and then sorting it in the Java code, but I would prefer to do it in a single SQL query. What SQL query, to be run in an Oracle database, would give me the desired result?

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  • Errors with redefinitions after upgrade to XCode 3.2.3

    - by CA Bearsfan
    I recently upgraded to Snow Leopard and Xcode 3.2.5 so I could test on my iPod Touch and iPhone and ran into some problems with the project I was working on. First it couldn't find a Base SDK, then my old frameworks weren't hooking up correctly. Finally after setting the Project Format to Xcode 3.1 compatible (3.2 also worked) and the Base SDK for all configurations to iOS 4.2, then setting my iOS deployment target to iOS 3.0 I was able to get the system to find a Base SDK and attempt a build. That's when the frameworks didn't want to cooperate. 4/6 I'm using displayed in red, so I re routed the path to the iPhone simulator 4.2 platform which worked perfectly. I was able to build my project, no errors or warnings and my app worked fine. I went to work last night thinking I had fixed the problem. This morning I fired up the laptop and went to build my code base and now have 1142 errors all of which have to do with code I haven't written deemed as being redefined. Suggestions? The following is just a small sample of the error list (obviously don't need to see all 1142) //Frameworks/Foundation.framework/Headers/NSZone.h:48: error: redefinition of 'NSMakeCollectable' /Frameworks/Foundation.framework/Headers/NSObject.h:65: error: duplicate interface declaration for class 'NSObject' /Frameworks/Foundation.framework/Headers/NSObject.h:67: error: redefinition of 'struct NSObject'

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  • Fast way to manually mod a number

    - by Nikolai Mushegian
    I need to be able to calculate (a^b) % c for very large values of a and b (which individually are pushing limit and which cause overflow errors when you try to calculate a^b). For small enough numbers, using the identity (a^b)%c = (a%c)^b%c works, but if c is too large this doesn't really help. I wrote a loop to do the mod operation manually, one a at a time: private static long no_Overflow_Mod(ulong num_base, ulong num_exponent, ulong mod) { long answer = 1; for (int x = 0; x < num_exponent; x++) { answer = (answer * num_base) % mod; } return answer; } but this takes a very long time. Is there any simple and fast way to do this operation without actually having to take a to the power of b AND without using time-consuming loops? If all else fails, I can make a bool array to represent a huge data type and figure out how to do this with bitwise operators, but there has to be a better way.

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  • cocoa/c++ relative path to load resources

    - by moka
    Hi, I am currently working directly with cocoa for the first time, to built a screen saver. Now I came across a problem when trying to load resources from within the .saver bundle. I basically have a small c++ wrapper class to load .exr files using freeImage. That works as long as I use absoulte paths, but thats not very useful, is it? So basically I tried everything, putting the .exr file on the level of the .saver bundle itself, inside the bundles Resources folder and so on. Then I simply tried to load the .exr like this without success particleTex = [self loadExrTexture: "ball.exr"]; I also tried making it go to the .saver bundles location like this: particleTex = [self loadExrTexture: "../../../ball.exr"]; to maybe load the .exr from that location but without success. I then came across this: NSString * path = [[NSBundle mainBundle] pathForResource:@"ball" ofType:@"exr"]; const char * pChar = [path UTF8String]; which seems to be a common way to find resources in cocoa, but for some reason its emty in my case. any ideas about that? I really tried out anything that came to my mind without success so I would be glad about some input!

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  • How can you adjust the height of a jquery UI accordian?

    - by KallDrexx
    In my UI I have an accordian setup that so far functions <div id="object_list"> <h3>Section 1</h3> <div>...content...</div> // More sections </div> The accordian works properly when it is first formed, and it seems to adjust itself well for the content inside each of the sections. However, if I then add more content into the accordian after the .accordian() call (via ajax), the inner for the section ends up overflowing. Since the accordian is being formed with almost no content, all the inner divs are extremely small, and thus the content overflows and you get accordians with scrollbars inside with almost no viewing area. I have attempted to add min-height styles to the object_list div, and the content divs to no avail. Adding the min-height to the inner divs kind of worked, but it messed up the accordian's animations, and adding it to the object_list div did absolutely nothing. How can I get a reasonable size out of the content sections even when there is not enough content to fill those sections?

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  • Hide Image Title in Slimbox

    - by Stephen
    My issue is a lot like this solved thread, except I'm using Slimbox 2: http://stackoverflow.com/questions/940994/hide-image-title-tool-tip-popup-on-mouse-rollover-or-hover When you hover over an image, the "Title" attribute pops up. I need HTML in my image title in Slimbox. So, of course, when you're hovering, the "Title" attribute shows all the HTML code. The code works perfectly when you're viewing the image in Slimbox so no problems there. I just need the Title attribute to be hidden/modified not to show this HTML code. I tried to change Q.title in slimbox.js to something else (like captionname). Then changed the HTML to call for: <a href="images/team/large.jpg" title="Joe Smith" captionname="URL" rel="lightbox-team"><img src="images/team/small.jpg" class ="headline" border="1" hspace="2" /></a> "Joe Smith" displays as the Title but when you view the image in Slimbox, captionname does not come up at all and neither does the Title. It's just blank where it should be. What do I need to modify in slimbox2.js to make this work?

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  • IntelliJ Doesn't Notice Changes in Interface

    - by yar
    [I've decided to give IntelliJ another go (to replace Eclipse), since its Groovy support is supposed to be the best. But back to Java...] I have an Interface that defines a constant public static final int CHANNEL_IN = 1; and about 20 classes in my Module that implement that interface. I've decided that this constant was a bad idea so I did what I do in Eclipse: I deleted the entire line. This should cause the Project tree to light up like a Christmas tree and all classes that implement that interface and use that constant to break. Instead, this is not happening. If I don't actually double-click on the relevant classes -- which I find using grep -- the module even builds correctly (using Build - Make Module). If I double-click on a relevant class, the error is shown both in the Project Tree and in the Editor. I am not able to replicate this behavior in small tests, but in large modules it works (incorrectly) this way. Is there some relevant setting in IntelliJ for this?

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  • Rotate using a transform, then change frame origin, and view expands??

    - by ZaBlanc
    This is quite the iPhone quandry. I am working on a library, but have narrowed down my problem to very simple code. What this code does is create a 50x50 view, applies a rotation transform of a few degrees, then shifts the frame down a few times. The result is the 50x50 view is now much larger looking. Here's the code: // a simple 50x50 view UIView *redThing = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)]; redThing.backgroundColor = [UIColor redColor]; [self.view addSubview:redThing]; // rotate a small amount (as long as it's not 90 or 180, etc.) redThing.transform = CGAffineTransformRotate(redThing.transform, 0.1234); // move the view down 2 pixels CGRect newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; // move the view down another 2 pixels newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height); redThing.frame = newFrame; So, what the heck is going on? Now, if I move the view by applying a translation transform, it works just fine. But that's not what I want to do and this should work anyway. Any ideas?

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  • SOAP web services in haskell?

    - by Dave
    I have to write a bunch of small web services. They must be defined by a WSDL and work via SOAP-RPC, in order to work with an existing workflow engine and service registry framework. I can, however, serve them on a service stack/platform of my choice. I'm presently writing them in Java, and it's not too bad. But I'm thinking my life might be easier if I was able to write these services in Haskell. Searching on Google, it looks like, once upon a time, someone else had the same idea and started a project called "HAIFA". However, it looks like HAIFA hasn't been maintained for some years, and I couldn't find any other frameworks supporting serving up services written in Haskell as SOAP web services. Does anyone know of any other frameworks that will allow me to easily write SOAP-based web services using Haskell? If not, has anyone done this manually (i.e., use XML libraries from hackage to process the incoming soap-rpc requests, and create soap-rpc compliant replies)? Was it difficult to do? Any gotchas? Was it worth the effort? Thanks in advance!

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  • Programming exercises in Java inheritance for intern

    - by Tenner
    I work for a small software development team, working primarily in Java, for a very large company. Our new intern showed up sight-unseen (not uncommon in my company). He has some C++ experience but no Java. Worse, he's never worked with inheritance in C++. Our code has a great deal of abstraction and a heavy reliance on inheritance. We need to get him up to speed as quickly as possible. Of course the rest of the team is busy, and so we can't take the time out of our day to teach a one-student 200-level CS course. Instead, I'd like to give him an actual programming project to work on which highlights how classes, interfaces, method overrides, etc. work. I've had him look at Project Euler, but most of the solutions end up being procedural, and not object-oriented programs. Do any of you have any somewhat-straightforward (and relatively quick) projects which you would give to an intern in this situation? Or, any recent (or current) students have a school project they'd be willing to share? Anyone else had this experience?

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  • git rebse onto remote updates

    - by Blake Chambers
    I work with a small team that uses git for source cod management. Recently, we have been doing topic branches to keep track of features then merging them into master locally then pushing them to a central git repository on a remote server. This works great when no changes have been made in master: I create my topic branch, commit it, merge it into master, then push. Hooray. However, if someone has pushed to origin before i do, my commits are not fast-forward. Thus a merge commit ensues. This also happens when a topic branch needs to merge with master locally to ensure my changes work with the code as of now. So, we end up with merge commits everywhere and a git log rivaling a friendship bracelet. So, rebasing is the obvious choice. What I would like is to: create topic branches holding several commits checkout master and pull (fast-forward because i haven't committed to master) rebase topic branches onto the new head of master rebase topics against master(so the topics start at masters head), bringing master up to my topic head My way of doing this currently is listed below: git checkout master git rebase master topic_1 git rebase topic_1 topic_2 git checkout master git rebase topic_2 git branch -d topic_1 topic_2 Is there a faster way to do this?

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  • Are there any libraries for parsing "number expressions" like 1,2-9,33- in Java

    - by mihi
    Hi, I don't think it is hard, just tedious to write: Some small free (as in beer) library where I can put in a String like 1,2-9,33- and it can tell me whether a given number matches that expression. Just like most programs have in their print range dialogs. Special functions for matching odd or even numbers only, or matching every number that is 2 mod 5 (or something like that) would be nice, but not needed. The only operation I have to perform on this list is whether the range contains a given (nonnegative) integer value; more operations like max/min value (if they exist) or an iterator would be nice, of course. What would be needed that it does not occupy lots of RAM if anyone enters 1-10000000 but the only number I will ever query is 12345 :-) (To implement it, I would parse a list into several (min/max/value/mod) pairs, like 1,10,0,1 for 1-10 or 11,33,1,2 for 1-33odd, or 12,62,2,10 for 12-62/10 (i. e. 12, 22, 32, ..., 62) and then check each number for all the intervals. Open intervals by using Integer.MaxValue etc. If there are no libs, any ideas to do it better/more efficient?)

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  • Castle windsor security exception

    - by Sunil
    I developed a small WCF service that uses Castle Windsor IoC container and it works fine on my PC. When I deploy it onto a Win 2008 R2 server and host the WCF service in IIS 7 it fails with the following error. I checked the server level web.config and the trust level is set to "Full". What do I need to do to get this to work. As a test I deployed the same service as it is onto a Windows 2003 server with the trust level set to "Full" and it works fine. I am unable to figure out what setting/configuration I am missing on the 2008 server that is making the service fail. Stack Trace: [SecurityException: That assembly does not allow partially trusted callers.] Castle.Windsor.WindsorContainer..ctor() +0 WMS.ServiceContractImplementation.IoC.IoCInstanceProvider..ctor(Type serviceType) in D:\WCF\WCFProofOfConcept\WMSServices \WMS.ServiceContractImplementation\IoC\IoCInstanceProvider.cs:19 WMS.ServiceContractImplementation.IoC.IoCServiceBehavior.ApplyDispatchBehav­ior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) in D:\WCF \WCFProofOfConcept\WMSServices\WMS.ServiceContractImplementation\IoC \IoCServiceBehavior.cs:24 System.ServiceModel.Description.DispatcherBuilder.InitializeServiceHost(Ser­viceDescription description, ServiceHostBase serviceHost) +377 System.ServiceModel.ServiceHostBase.InitializeRuntime() +37 System.ServiceModel.ServiceHostBase.OnBeginOpen() +27 System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout) +49 System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout) +261 System.ServiceModel.HostingManager.ActivateService(String normalizedVirtualPath) +121 System.ServiceModel.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath) +479

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  • How can I improve the performance of LinqToSql queries that use EntitySet properties?

    - by DanM
    I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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  • Problem declaring and calling internal metthods

    - by Martin
    How do I declare and use small helper functions inside my normal methods ? In on of my objective-c methods I need a function to find an item within a string -(void) Onlookjson:(id) sender{ NSString * res = getKeyValue(res, @"Birth"); } I came up with a normal C type declaration for helper function getKeyvalue like this NSString * getKeyvalue(NSString * s, NSString key){ NSString *trm = [[s substringFromIndex:2] substringToIndex:[s length]-3]; NSArray *list = [trm componentsSeparatedByString:@";"]; .... NSString res; res = [list objectAtIndex:1]; ... return res; } Input data string: { Birth = ".."; Death = "..."; ... } Anyway I get an exception "unrecognized selector sent to instance" for any of the two first lines in the helper function How do I declare helper functions that are just to be used internally and how to call them safely ? regards Martin

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  • What's the best way to transfer a large dataset over a .NET web service?

    - by Malvineous
    I've inherited a C# .NET application which talks to a web service, and the web service talks to an Oracle database. I need to add an export function to the UI, to produce an Excel spreadsheet of some of the data. I have created a web service function to run a database query, load the data into a DataTable and then return it, which works fine for a small number of rows. However there is enough data in the full run that the client application locks up for a few minutes and then returns a timeout error. Obviously this isn't the best way to retrieve such a large dataset. Before I go ahead and come up with some dodgy way of splitting the call, I'm wondering if there is already something in place that can handle this. At the moment I'm thinking of a startExport function then repeatedly calling a next50Rows function until there is no data left, but because web services are stateless this means I'm going to have to keep some sort of ID number around and deal with the associated permissions. It would mean that I don't have to load the entire data set into the web server's memory though, which is one good thing. So if anyone knows a better way to retrieve a large amount of data (in a table format) over a .NET web service, please let me know!

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  • scroll bar problems in java Layered Panes

    - by vondip
    Hi all, I've been trying to build this small java app. I find it very difficult to design UI in java, tasks that seem very simple become complicated and all these strange misbehaviors occur. In my app I've created a JLayeredPane which contains two layers. One on top on the other, They both contain scrollbars. Here's an explanation of the two layers: Layer 1: A very big image inside something similar to a scrollpane. The image is scrollable. Layer 2: A graphics2d object, this object draws an image. Once the image reaches a certain length, the layer gets a scrollpane that advances with the drawing with time. I'd like to connect both layers. I want layer two to update the scrollbar on layer 1. Meaning that once it reaches a certain length, both scrollbars will advance together. When I try doing that, the two scroll bars really do advance, but ( ! ) this strange flickering occurs. I don't understand what is the reason for the flickering. Is there any other way to implement this in a simple manner? I must have the second layer on top of the first one (drawing on top of image) since I cannot open a special post for thanking the wonderful people of this forum, I'll do it here. Thank you, you are great help. I hope this problem is solvable as well.

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  • When to drop an IT job

    - by Nippysaurus
    In my career I have had two programming jobs. Both these jobs were in a field that I am most familiar with (C# / MSSQL) but I have quit both jobs for the same reason: unmanageable code and bad (loose) company structure. There was something in common with both these jobs: small companies (in one I was the only developer). Currently I am in the following position: being given written instructions which are almost impossible to follow (somewhat of a fools errand). we are given short time constraints, but seldom asked how long work will take, and when we do it is always too long and needs to be shorter (and when it ends up taking longer than they need it to take, it's always our fault). there is no time for proper documenting, but we get blamed for not documenting (see previous point). Management is constantly screwing me around, saying I'm underperforming on a given task (which is not true, and switching me to a task which is much more confusing). So I must ask my fellow developers: how bad does a job need to be before you would consider jumping ship? And what to look out for when considering taking a job. In future I will be asking about documented procedures, release control, bug management and adoption of new technologies. EDIT: Let me add some more fuel to the fire ... I have been in my current job for just over a year, and the work I am doing almost never uses any of the knowledge I have gained from the other work I have been doing here. Everything is a giant learning curve. Because of this about 30% of my time is learning what is going on with this new product (who's owner / original developer has left the company), 30% trying to find the relevant documentation that helps the whole thing make sense, 30% actually finding where to make the change, 10% actually making the change.

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  • Out of memory while iterating through rowset

    - by Phliplip
    Hi All, I have a "small" table of 60400 rows with zipcode data. I wan't to iterate through them all, update a column value, and then save it. The following is part of my Zipcodes model which extends My_Db_Table that a totalRows function that - you guessed it.. returns the total number of rows in the table (60400 rows) public function normalizeTable() { $this->getAdapter()->setProfiler(false); $totalRows = $this->totalRows(); $rowsPerQuery = 5; for($i = 0; $i < $totalRows; $i = $i + $rowsPerQuery) { $select = $this->select()->limit($i, $rowsPerQuery); $rowset = $this->fetchAll($select); foreach ($rowset as $row) { $row->{self::$normalCityColumn} = $row->normalize($row->{self::$cityColumn}); $row->save(); } unset($rowset); } } My rowClass contains a normalize function (basicly a metaphone wrapper doing some extra magic). At first i tried a plain old $this-fetchAll(), but got a out of memory (128MB) right away. Then i tried splitting the rowset into chunks, only difference is that some rows actually gets updated. Any ideas on how i can acomplish this, or should i fallback to ye'olde mysql_query()

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  • Do ORMs normally allow circular relations? If so, how would they handle it?

    - by SeanJA
    I was hacking around trying to make a basic orm that has support for the one => one and one => many relationships. I think I succeeded somewhat, but I am curious about how to handle circular relationships. Say you had something like this: user::hasOne('car'); car::hasMany('wheels'); car::property('type'); wheel::hasOne('car'); You could then do this (theoretically): $u = new user(); echo $u->car->wheels[0]->car->wheels[1]->car->wheels[2]->car->wheels[3]->type; #=> "monster truck" Now, I am not sure why you would want to do this. It seems like it wastes a whole pile of memory and time just to get to something that could have been done in a much shorter way. In my small ORM, I now have 4 copies of the wheel class, and 4 copies of the car class in memory, which causes a problem if I update one of them and save it back to the database, the rest get out of date, and could overwrite the changes that were already made. How do other ORMs handle circular references? Do they even allow it? Do they go back up the tree and create a pointer to one of the parents? DO they let the coder shoot themselves in the foot if they are silly enough to go around in circles?

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  • Fastest inline-assembly spinlock

    - by sigvardsen
    I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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  • Document management, SCM ?

    - by tsunade
    Hello, This might not be a hard core programming question, but it's related to some of the tools used by programmers I suspect. So we're a bunch of people each with a bunch of documents and a bunch of different computers on a bunch of operating systems (well, only 2, linux and windows). The best way these documents can be stored/managed is if they were available offline (the laptop might not always be online) but also synchronized between all the machines. Having a server with extra reliable storage be a "base repository" seems like a good idea to me. Using a SCM comes to my mind and I've tried Subversion, and it seems to be a good thing that it uses a centralized repository - but: When checking out the total size of the checkout is roughly double the original size. Big files or big repositories seem to slow it down. Also I've tried rsync, which might work - but it's a bit rough when it comes to the potential conflict. Finally I've tried Unison (which is a wrapping of rsync, I think) and while it works it becomes horribly slow for the big directories we have here since it has to scan everything. So the question is - is there a SCM tool out there that is actually practial to use for a big bunch of both small and big files? If thats a NO - does anyone know other tools that do this job? Thanks for reading :)

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