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• Collision point of 2 curves in a 3d-room

  - by Frank

  Hello, i am programming a small game for quite some time. We started coding a small FPS-Shooter inside of a project at school to get a bit experience using directX. I dont know why, but i couldnt stop the project and started programming at home aswell. At the moment i am trying to create some small AI. Of cause thats definatlly not easy, but thats my personal goal anyways. The topic could prolly fill multiple books hehe. I've got the walking part of my bots done so far. They walk along a scriped path. I am not working on the "aiming" of the bots. While programming that i hit on some math problem i couldnt solve yet. I hope of your input on this to help me get further. Concepts, ideas and everything else are highly appreciated. Problem: Calculate the position (D3DXVECTOR3) where the curve of the projectile (depends on gravity, speed), hit the curved of the enemys walking path (depends on speed). We assume that the enemy walks in a constant line. Known variables: float projectilSpeed = 2000 m/s //speed of the projectile per second float gravitation = 9.81 m/s^2 //of cause the gravity lol D3DXVECTOR3 targetPosition //position of the target stored in a vector (x,y,z) D3DXVECTOR3 projectilePosition //position of the projectile D3DXVECTOR3 targetSpeed //stores the change of the targets position in the last second Variabledefinition ProjectilePosition at time of collision = ProjectilePos_t TargetPosition at time of collision = TargetPos_t ProjectilePosition at time 0, now = ProjectilePos_0 TargetPosition at time 0, now = TargetPos_0 Time to impact = t Aim-angle = theta My try: Found a formular to calculate "drop" (Drop of the projectile based on the gravity) on Wikipedia: float drop = 0.5f * gravity * t * t The speed of the projectile has a horizontal and a vertical part.. Found a formular for that on wikipedia aswell: ProjectilVelocity.x = projectilSpeed * cos(theta) ProjectilVelocity.y = projectilSpeed * sin(theta) So i would assume this is true for the projectile curve: ProjectilePos_t.x = ProjectilePos_0.x + ProjectileSpeed * t ProjectilePos_t.y = ProjectilePos_0.y + ProjectileSpeed * t + 0.5f * gravity * t * t ProjectilePos_t.z = ProjectilePos_0.z + ProjectileSpeed * t The target walk with a constant speed, so we can determine his curve by this: TargetPos_t = TargetPos_0 + TargetSpeed * D3DXVECTOR3(t, t, t) Now i dont know how to continue. I have to solve it somehow to get a hold on the time to impact somehow. As a basic formular i could use: float time = distanz / projectileSpeed But that wouldnt be truly correct as it would assume a linear "Trajectory". We just find this behaivor when using a rocket. I hope i was able to explain the problem as much as possible. If there are questions left, feel free to ask me! Greets from germany, Frank

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• Trying to style the first tbody different than others without introducing another class.

  - by mwiik

  I have a table with multiple tbody's, each of which has a classed row, and I want it so that the classed row in the first tbody has style differences, but am unable to get tbody:first-child to work in any browser. Perhaps I am missing something, or maybe there is a workaround. Ideally, I would like to provide the programmers with a single tbody section they can use as a template, but will otherwise have to add a class to the first tbody, making for an extra test in the programming. The html is straightforward: <tbody class="subGroup"> <tr class="subGroupHeader"> <th colspan="8">All Grades: Special Education</th> <td class="grid" colspan="2"><!-- contains AMO line --></td> <td><!-- right 100 --></td> </tr> <tr>...</tr> <!-- several more rows of data --> </tbody> There are several tbody's per table. I want to style the th and td's within tr.subGroupHeader in the very first tbody differently than the rest. Just to illustrate, I want to add a border-top to the tr.subGroupHeader cells. The tr.subGroupHeader will be styled with a border-top, such as: table.databargraph.continued tr.subGroupHeader th, table.databargraph.continued tr.subGroupHeader td { border-top: 6px solid red; } For the first tbody, I am trying: table.databargraph.continued tbody:first-child tr.subGroupHeader th { border-top: 6px solid blue ; } However, this doesn't seem to work in any browser (I've tested in Safari, Opera, Firefox, and PrinceXML, all on my Mac) Curiously, the usually excellent Xyle Scope tool indicates that the blue border should be taking precedence, though it obviously is not. See the screenshot at http://s3.amazonaws.com/ember/kUD8DHrz06xowTBK3qpB2biPJrLWTZCP_o.png This screenshot shows (top left) the American Indian th is selected, and (bottom right), shows (via black instead of gray text for the css declaration), that, indeed, the blue border should be given precedence. Yet the border is red. I may be missing something fundamental, like pseudo-classes not working for tbodys at all... This really only needs to work in PrinceXML, and maybe Safari so I can see what I'm doing with webkit-based css tools. Note I did try a selector like tr.subGroupHeader:first-child, but such tr's apparently consider the tbody the parent (as I would suspect), thus made every border blue. Thanks...

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• Function Point Analysis -- a seriously overestimating technique?

  - by kizzx2

  I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week (I"m not even saying weekend) to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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• Windows 7 - pydoc from cmd

  - by Random_Person

  Okay, I'm having one of those moments that makes me question my ability to use a computer. This is not the sort of question I imagined asking as my first SO post, but here goes. Started on Zed's new "Learn Python the Hard Way" since I've been looking to get back into programming after a 10 year hiatus and python was always what I wanted. This book has really spoken to me. That being said, I'm having a serious issue with pydoc from the command. I've got all the directories in c:/python26 in my system path and I can execute pydoc from the command line just fine regardless of pwd - but it accepts no arguments. Doesn't matter what I type, I just get the standard pydoc output telling me the acceptable arguments. Any ideas? For what it's worth, I installed ActivePython as per Zed's suggestion. C:\Users\Chevee>pydoc file pydoc - the Python documentation tool pydoc.py <name> ... Show text documentation on something. <name> may be the name of a Python keyword, topic, function, module, or package, or a dotted reference to a class or function within a module or module in a package. If <name> contains a '\', it is used as the path to a Python source file to document. If name is 'keywords', 'topics', or 'modules', a listing of these things is displayed. pydoc.py -k <keyword> Search for a keyword in the synopsis lines of all available modules. pydoc.py -p <port> Start an HTTP server on the given port on the local machine. pydoc.py -g Pop up a graphical interface for finding and serving documentation. pydoc.py -w <name> ... Write out the HTML documentation for a module to a file in the current directory. If <name> contains a '\', it is treated as a filename; if it names a directory, documentation is written for all the contents. C:\Users\Chevee> EDIT: New information, pydoc works just fine in PowerShell. As a linux user, I have no idea why I'm trying to use cmd anyways--but I'd still love to figure out what's up with pydoc and cmd. EDIT 2: More new information. In cmd... c:\>python c:/python26/lib/pydoc.py file ...works just fine. Everything works just fine with just pydoc in PowerShell without me worrying about pwd, or extensions or paths.

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• Can i store a Queue in viewstate? only will store the first item i add to queue

  - by Mausimo

  Hey, as the question states i am trying to store a Queue in a viewstate (to track postbacks and refreshes to stop a form from resubmitting). Here is just the viewstate code: private Queue<string> p_tempQue { set { ViewState["sTemp"] = value; } get { return (Queue<string>)ViewState["sTemp"]; } } //BasePage constructor public BasePage() { //create a Queue of string //sTemp = new Queue(); this.Load += new EventHandler(this.Page_Load); this.Init += new EventHandler(this.Page_Init); } //In the 'page_Init' event we have created a simple hidden field by name 'hdnGuid' which is attached to the page on the first hit itself. protected void Page_Init(object sender, EventArgs e) { //initializing the hidden field //create a hidden field with a ID HiddenField hdnGuid = new HiddenField(); hdnGuid.ID = "hdnGuid"; //if it is the first time the page is loaded, create a new guid and assign it as the hidden field value if (!Page.IsPostBack) hdnGuid.Value = Guid.NewGuid().ToString(); //add the hidden field to the page Page.Form.Controls.Add(hdnGuid); } //In the 'page_Load' event we check if the hidden field value is same as the old value. In case the value is not same that means it's a 'postback' //and if the value is same then its 'refresh'. As per situation we set the 'httpContent.Items["Refresh"]' value. protected void Page_Load(object sender, EventArgs e) { if(p_tempQue != null) sTemp = p_tempQue; else sTemp = new Queue<string>(); //The hdnGuid will be set the first time page is loaded, else the hdnGuid //will be set after each time the form is submitted using javascript. //assign the hidden field currently on the page for manipulation HiddenField h1 = (HiddenField)(Page.Form.FindControl("hdnGuid")); //create an instance of the GuidClass GuidClass currentGuid = new GuidClass(); //set the GuidClass Guid property to the value of the hidden field currentGuid.Guid = h1.Value; //check to see if the Queue of strings contains the string which is the current Guid property of the GuidClass //if the are equal, then the page was refreshed if (sTemp.Contains<string>(currentGuid.Guid)) { //adds item as key/value pair to share data between an System.Web.IHttpModule interface and an System.Web.IHttpHandler interface during an HTTP request. System.Web.HttpContext.Current.Items.Add("IsRefresh", true); } //if they are not requal, the page is not refreshed else { //if the current Guid property in the GuidClass is not null or not an empty string //add the new Guid to the Queue if (!(currentGuid.Guid.Equals(null) || currentGuid.Guid.Equals(""))) sTemp.Enqueue(currentGuid.Guid); System.Web.HttpContext.Current.Items.Add("IsRefresh", false); } p_tempQue = sTemp; }

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• Solr Facet Search spring-data-solr

  - by sv1

  I am new to Solr and we are using Spring-data for Solr I have a question may be its too simple but I am unable to comprehend. Basically I need to search on any field but I have a "zip" field as one of the facet fields. I have a Solr repository . (Am not sure if the annotations on the Repository are correct.) public interface MyRepository extends SolrCrudRepository<MyPOJO, String> { @Query(value = "*:*") @Facet(fields={"zip"}) public FacetPage<MyPOJO> findByQueryandAnno(String searchTerm,Pageable page); } In my Service class I am trying to call this methods by Injecting MyRepository like below public class MyService { @Inject MyRepository solrRepo; @Inject SolrTemplate solrTemplate; public FacetPage<MyPOJO> tryFacets(String searchString){ //Here is where I am struggling SimpleFacetQuery query = new SimpleQuery(new SimpleStringCriteria(searchString)); query.setFacetOptions(new FacetOptions("zip")); //Not sure how to get the Pageable object. //But the repository doesnt accept without it. return solrTemplate.queryForPage(query,{Pageable Instance to be passed here}) } From my jUnit I am loading context files needed for Solr and Spring //In jUnit the test method looks like this service.tryFacets("some value"); and it fails with - method not found in the service class at the call to the repository method. *********EDIT**************** As per ChristophStrobl's advice created a copyfield called multivaluedCopyField and the searchString argument works good. But the facet still isnt working...Now my code looks like this. I get the MyPOJO object as response but the facetcount and the faceted values are missing. public interface MyRepository extends SolrCrudRepository<MyPOJO, String> { @Query(value = "*:*") @Facet(fields={"zip"}) public FacetPage<MyPOJO> findByQueryandAnno(String searchTerm,Pageable page); } My service class looks like public class MyService { @Inject MyRepository solrRepo; public FacetPage<MyPOJO> tryFacets(String searchString){ //Here is where I am struggling SimpleFacetQuery query = new SimpleQuery(new SimpleStringCriteria(searchString)).setPageRequest new PageRequest(0,5)); query.setFacetOptions(new FacetOptions("zip")); FacetPage<MyPOJO> facetedPOJO= solrRepo.findByQueryandAnno(searchString,query.getPageRequest()); return facetedPOJO; } My jUnit method call is like service.tryFacets("some value");

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• Using MySQL to generate daily sales reports with filled gaps, grouped by currency

  - by Shane O'Grady

  I'm trying to create what I think is a relatively basic report for an online store, using MySQL 5.1.45 The store can receive payment in multiple currencies. I have created some sample tables with data and am trying to generate a straightforward tabular result set grouped by date and currency so that I can graph these figures. I want to see each currency that is available per date, with a 0 in the result if there were no sales in that currency for that day. If I can get that to work I want to do the same but also grouped by product id. In the sample data I have provided there are only 3 currencies and 2 product ids, but in practice there can be any number of each. I can correctly group by date, but then when I add a grouping by currency my query does not return what I want. I based my work off this article. My reporting query, grouped only by date: SELECT calendar.datefield AS date, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date Now grouped by date and currency: SELECT calendar.datefield AS date, orders.currency_id, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date, orders.currency_id The results I am getting (grouped by date and currency): +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | NULL | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The results I want: +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | 3 | 0.00 | | 2009-08-16 | 45 | 0.00 | | 2009-08-16 | 49 | 0.00 | | 2009-08-17 | 3 | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 45 | 0.00 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The schema and data I am using in my tests: CREATE TABLE orders ( id INT PRIMARY KEY AUTO_INCREMENT, order_date DATETIME, order_id INT, product_id INT, currency_id INT, order_value DECIMAL(9,2), customer_id INT ); INSERT INTO orders (order_date, order_id, product_id, currency_id, order_value, customer_id) VALUES ('2009-08-15 10:20:20', '123', '1', '45', '12.50', '322'), ('2009-08-15 12:30:20', '124', '1', '49', '122.60', '400'), ('2009-08-15 13:41:20', '125', '1', '3', '40.97', '324'), ('2009-08-15 10:20:20', '126', '2', '45', '12.50', '345'), ('2009-08-15 13:41:20', '131', '2', '3', '40.97', '756'), ('2009-08-17 10:20:20', '3234', '1', '45', '12.50', '1322'), ('2009-08-17 10:20:20', '4642', '2', '45', '12.50', '1345'), ('2009-08-17 12:30:20', '23', '2', '49', '122.60', '3142'), ('2009-08-18 12:30:20', '2131', '1', '49', '122.60', '4700'), ('2009-08-18 13:41:20', '4568', '1', '3', '40.97', '3274'), ('2009-08-18 12:30:20', '956', '2', '49', '122.60', '3542'), ('2009-08-18 13:41:20', '443', '2', '3', '40.97', '7556'); CREATE TABLE currency ( id INT PRIMARY KEY, name VARCHAR(255) ); INSERT INTO currency (id, name) VALUES (3, 'Euro'), (45, 'US Dollar'), (49, 'CA Dollar'); CREATE TABLE calendar (datefield DATE); DELIMITER | CREATE PROCEDURE fill_calendar(start_date DATE, end_date DATE) BEGIN DECLARE crt_date DATE; SET crt_date=start_date; WHILE crt_date < end_date DO INSERT INTO calendar VALUES(crt_date); SET crt_date = ADDDATE(crt_date, INTERVAL 1 DAY); END WHILE; END | DELIMITER ; CALL fill_calendar('2008-01-01', '2011-12-31');

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• JSON.Net: deserializing polymorphic types without specifying the assembly

  - by Frank Schwieterman

  I see that using JSON.Net, I can decode polymorphic objects if a $type attribute specifies the specific type of the JSON object. In all the examples I've seen, $type includes the namespace. Is it possible to make this work including just a simple typename without the assembly? I'd be happy to specify a default assembly to the JsonSerializer if thats possible I am able to deserialize the JSON using: public class SingleAssemblyJsonTypeBinder : SerializationBinder { private readonly Assembly _assembly; private Dictionary _typesBySimpleName = new Dictionary(StringComparer.OrdinalIgnoreCase); private Dictionary _simpleNameByType = new Dictionary(); public SingleAssemblyJsonTypeBinder(Assembly assembly) { _assembly = assembly; _typesBySimpleName = new Dictionary<string, Type>(); foreach (var type in _assembly.GetTypes().Where(t => t.IsPublic)) { if (_typesBySimpleName.ContainsKey(type.Name)) throw new InvalidOperationException("Cannot user PolymorphicBinder on a namespace where multiple public types have same name."); _typesBySimpleName[type.Name] = type; _simpleNameByType[type] = type.Name; } } public override Type BindToType(string assemblyName, string typeName) { Type result; if (_typesBySimpleName.TryGetValue(typeName.Trim(), out result)) return result; return null; } public override void BindToName(Type serializedType, out string assemblyName, out string typeName) { string name; if (_simpleNameByType.TryGetValue(serializedType, out name)) { typeName = name; assemblyName = null;// _assembly.FullName; } else { typeName = null; assemblyName = null; } } } ... public static JsonSerializerSettings GetJsonSerializationSettings() { var settings = new JsonSerializerSettings(); settings.Binder = new SingleAssemblyJsonTypeBinder(typeof(MvcApplication).Assembly); settings.TypeNameHandling = TypeNameHandling.Objects; return settings; } .... var serializer = JsonSerializer.Create(settings); I haven't been able to make this work with MVC though, I'm configuring json deserialization per the code below in Application_Start, and the object is deserialized, but using the base type one. GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.Binder = new SingleAssemblyJsonTypeBinder(this.GetType().Assembly); GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.All; GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.TypeNameAssemblyFormat = FormatterAssemblyStyle.Simple;

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• Generating custom-form documents from base-form plus XML?

  - by KlaymenDK

  Hi all, this is my first stack overflow, and it's a complex one. Sorry. My task is to generate custom documents from a basic template plus some XML without having a custom form design element for each case. Here's the whole picture: We are building a Lotus Notes (client, not web) application for world-wide application access control; the scope is something like 400.000 users being able to request access to any of 1000+ applications. Each application needs its own request form -- different number of approvers, various info required, that sort of thing. We simply can't have a thousand forms in a database (one per application), and anyway their maintenance really needs to be pushed from the developers to the application owners. So instead of custom forms, we'd like to create a generic "template" form that stores a block of basic fields, but then allows application owners to define another block of fields dynamically -- "I want a mandatory plain-text field named 'Name' here, and then a date field named 'Due' here that must be later than today's date, and then ...". I hope this makes sense (if not, think of it as a generic questionnaire application). I pretty much have the structure in place for designing the dynamic fields (form builder GUI - XML-encoded data - pre-rendered DXL for injecting into a form), including mark-up for field types, value options, and rudimentary field validation instructions. My problem is generating a document with this dynamic content injected at the proper location (without needing a custom form design element for each case). Doing the dynamic content via HTML is out. The Notes client web rendering is simply way too poor, and it would be quite a challenge to implement things like field validation instructions, date selectors, and name look-ups. DXL, on the other hand, would allow us to use native Notes fields and code. As a tech demo, I've managed to implement a custom form generator that injects the pre-rendered DXL for the dynamic content into a base form; but as I said, we don't want a ton of custom form design elements. I've tried to implement a way to create a document with the "store form in document" flag set, but once I've created the document from the base form, I can't get DXL access to the stored form design, and so I can't inject my dynamic content. I know this is not something Notes was ever intended to do. Has anyone ever tried something like it (and gotten away with it)? Thanks for reading this far. With a boatload of thanks in advance, Jan Gundtofte-Bruun

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• Gradual memory leak in loop over contents of QTMovie

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases. Instruments is not detecting any memory leaks per se, but the object trace shows certain General Data blocks to be increasing in size. [Edited out reference to slowdown as it doesn't seem to be as much of a problem as I thought.] Edit: let's knock out some parts of the code inside the loop & see what we find out... Test 1 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } Here we simply loop over the whole movie, creating the filename and logging it. Memory characteristics: remains at 15MB usage for the duration. Test 2 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; [sourceMovie stepForward]; [arp release]; } Here we add back in the creation of the NSImage from the current frame. Memory characteristics: gradually increasing memory usage. RSIZE is at 60MB by frame 200; 75MB by f300. Test 3 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; NSData *imageData = [image TIFFRepresentation]; [sourceMovie stepForward]; [arp release]; } We've added back in the creation of an NSData object from the NSImage. Memory characteristics: Memory usage is again increasing: 62MB at f200; 75MB at f300. In other words, largely identical. It looks like a memory leak in the underlying system QTMovie uses to do currentFrameImage, to me.

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• Looking for an Open Source Project in need of help

  - by hvidgaard

  Hi StackOverflow! I'm a CS student on well on my way to graduate. I have had a difficult time of finding relevant student jobs (they seems to be taken merely hours after the notice gets on the board) , so instead I'm looking for an open source project in need of help. I'm aware that I should choose one that I use, but I'm not aware of any OS-project that I use that needs help. That's why I'm asking you. I don't have any deep experience, but I here are some of my biggest projects so far: BitTorrent-ish client in Python (a subset of BitTorrent) HTTP 1.1 webserver in Java Compiler from a subset of Java to run on JRE Flash-framework project to model an iPad look and feel (not to run actual iPad programs) complete with an API for programs. Complete MySQL database for a booking system, with departure and arrival times, so you could only book valid tickets (with a Java frontend). I know, Java and languages like AS3 and C# feels natural per se, Python, and have done a fair bit of hacking around in C, but I don't feel very comfortable with it. Mostly I'm afraid to make a fuckup because I have such a high degree of control. I would like to think I'm well aware of good software design practices, but in reality what I do is ask myself "would I like to use/maintain this?", and I love to refactor my code because I see optimizations. I love algorithms and to make them run in the best possible time. I don't have any preferred domain to work in, but I wouldn't mind it to be graphics or math heavy. Ideally I'm looking for a project in C++ to learn the in's and out's of it, but I'm well aware that I don't know that language very well. I would like to have a mentor-like figure until I'm confident enough to stand on my own, not one to review all my code (I'm sure someone will to start with anyway), but to ask questions about the project and language in question. I do have a wife and two children, so don't expect me to put in 10+ hours every week. In return I can work on my own, I strive to program modular and maintainable code. Know how to read an API, use Google, StackOverflow and online resources in general. If you have any questions, shoot. I'm looking forward to your suggestions.

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• Code golf - hex to (raw) binary conversion

  - by Alnitak

  In response to this question asking about hex to (raw) binary conversion, a comment suggested that it could be solved in "5-10 lines of C, or any other language." I'm sure that for (some) scripting languages that could be achieved, and would like to see how. Can we prove that comment true, for C, too? NB: this doesn't mean hex to ASCII binary - specifically the output should be a raw octet stream corresponding to the input ASCII hex. Also, the input parser should skip/ignore white space. edit (by Brian Campbell) May I propose the following rules, for consistency? Feel free to edit or delete these if you don't think these are helpful, but I think that since there has been some discussion of how certain cases should work, some clarification would be helpful. The program must read from stdin and write to stdout (we could also allow reading from and writing to files passed in on the command line, but I can't imagine that would be shorter in any language than stdin and stdout) The program must use only packages included with your base, standard language distribution. In the case of C/C++, this means their respective standard libraries, and not POSIX. The program must compile or run without any special options passed to the compiler or interpreter (so, 'gcc myprog.c' or 'python myprog.py' or 'ruby myprog.rb' are OK, while 'ruby -rscanf myprog.rb' is not allowed; requiring/importing modules counts against your character count). The program should read integer bytes represented by pairs of adjacent hexadecimal digits (upper, lower, or mixed case), optionally separated by whitespace, and write the corresponding bytes to output. Each pair of hexadecimal digits is written with most significant nibble first. The behavior of the program on invalid input (characters besides [a-fA-F \t\r\n], spaces separating the two characters in an individual byte, an odd number of hex digits in the input) is undefined; any behavior (other than actively damaging the user's computer or something) on bad input is acceptable (throwing an error, stopping output, ignoring bad characters, treating a single character as the value of one byte, are all OK) The program may write no additional bytes to output. Code is scored by fewest total bytes in the source file. (Or, if we wanted to be more true to the original challenge, the score would be based on lowest number of lines of code; I would impose an 80 character limit per line in that case, since otherwise you'd get a bunch of ties for 1 line).

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• Open Cl.I just need to convert the code to using two work items in the for loop .Currentlly it uses one

  - by user1660282

  spmv_csr_scalar_kernel(const int num_rows , const int * ptr , const int * indices , const float * data , const float * x, float * y) { int row = get_global_id(0); if(row < num_rows) { float dot = 0; int row_start = ptr[row]; int row_end = ptr[row+1]; for (int jj = row_start; jj < row_end; jj++) { dot += data[jj] * x[indices[jj]]; } y[row] += dot; } } Above is the Open Cl code for multiplying a sparse matrix in CSR format with a Column vector.It uses one global work item per for loop.Can anybody help me in using two work items in each for loop.I am new to open cl and get a lot of issues if I modify even the smallest thing.Please help me.This a part of my project.I made it this parallel but I wanna make it more parallel.Please help me if you can.plzzzz A single work item executes the for loop from row_start to row_end.I want that this row or for loop is further divided into two parts each executed by a single work item.How do I go on accomplishing that? This is what I could come up with but its returning the wrong output.plzz help __kernel void mykernel(__global int* colvector,__global int* val,__global int* result,__global int* index,__global int* rowptr,__global int* sync) { __global int vals[8]={0,0,0,0,0,0,0,0}; for(int i=0;i<4;i++) { result[i]=0; } barrier(CLK_GLOBAL_MEM_FENCE); int thread_id=get_global_id(0); int warp_id=thread_id/2; int lane=(thread_id)&1; int row=warp_id; if(row<4) { int row_start = rowptr[row]; int row_end = rowptr[row+1]; vals[thread_id]=0; for (int i = row_start+lane; i<row_end; i+=2) { vals[thread_id]+=val[i]*colvector[index[i]]; } vals[thread_id]+=vals[thread_id+1]; if(lane==0){ result[row] += vals[thread_id]; } } }

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• iPhone Image Resources, ICO vs PNG, app bundle filesize

  - by Jasarien

  My application has a collection of around 1940 icons that are used throughout. They're currently in ICO and new images provided to me come in ICO format too. I have noticed that they contain a 16x16 and 32x32 representation of each icon in one file. Each file is roughly 4KB in filesize (as reported by finder, but ls reports that they vary from being ~1000 bytes to 5000 bytes) A very small number of these icons only contain the 32x32 representation, and as a result are only around 700 bytes in size. Currently I am bundling these icons with my application and they are inflating the size of the app a bit more than I would like. Altogether, the images total just about 25.5MB. Xcode must do some kind of compression because the resulting app bundle is about 12.4MB. Compressing this further into a ZIP (as it would be when submitted to the App Store), results in a final file of 5.8MB. I'm aware that the maximum limit for over the air App Store downloads has been raised to 20MB since the introduction of the iPad (I'm not sure if that extends to iPhone apps as well as iPad apps though, if not the limit would be 10MB). My worry is that new icons are going to be added (sometimes up to 10 icons per week), and will continue to inflate the app bundle over time. What is the best way to distribute these icons with my app? Things I've tried and not had much success with: Converting the icons from ICO to PNG: I tried this in the hopes that the pngcrush utility would help out with the filesize. But it appears that it doesn't make much of a difference between a normal PNG and a crushed png (I believe it just optimises the image for display on the iPhone's GPU rather than compress it's size). Also in going from ICO to PNG actually increased the size of the icon file... Zipping the images, and then uncompressing them on first run. While this did reduce the overall image sizes, I found that the effort needed to unzip them, copy them to the documents folder and ensure that duplication doesn't happen on upgrades was too much hassle to be worth the benefit. Also, on original and 3G iPhones unzipping and copying around 25MB of images takes too long and creates a bad experience... Things I've considered but not yet tried: Instead of distributing the icons within the app bundle, host them online, and download each icon on demand (it depends on the user's data as to which icons will actually be displayed and when). Issues with this is that bandwidth costs money, and image downloads will be bandwidth intensive. However, my app currently has a small userbase of around 5,500 users (of which I estimate around 1500 to be active based on Flurry stats), and I have a huge unused bandwidth allowance with my current hosting package. So I'm open to thoughts on how to solve this tricky issue.

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• Reliable session faulting for unknown reason

  - by Scarfman007

  I am trying to achieve the following - one client-side proxy instance (kept open) accessed by multiple threads using a reliable session. What I have managed so far is to have either A) a reliable session with a client-side proxy which is created and disposed per call or B) what I aim for, but without a reliable session. When I enable reliable sessions on my binding however, the following behaviour is exhibited: Client-side Upon application startup everything appears to work fine until roughly 18 messages in to the WCF session. I firstly get the proxy.InnerChannel.Faulted event raised, then an exception is caught at the point where I am calling the method on the proxy. The exception is a System.TimeoutException, with message: "The request channel timed out while waiting for a reply after 00:00:59.9062512. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout." The inner exception has a similar message: "The request operation did not complete within the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout." With the method at the top of the inner stack trace being: System.ServiceModel.Channels.ReliableRequestSessionChannel.SyncRequest.WaitForReply(TimeSpan timeout) I then call proxy.Close followed by proxy.Abort (catching and ignoring exceptions). If I utilize the default settings (i.e. have simply <reliableSession/>), then calling proxy. Close results in another System.Timeout exception (although this time the allotted timeout is 00:00:00), however if I override the defaults as specified above no exception is thrown. Service-side Utilizing WCF tracing I get a System.ServiceModel.CommunicationException, with message: "The sequence has been terminated by the remote endpoint. The session has stopped waiting for a particular reply. Because of this the reliable session cannot continue. The reliable session was faulted." And a stack trace ending at: System.ServiceModel.AsyncResult.End[TAsyncResult](IAsyncResult result) When remotely attaching to the server I get the same message, which occurs when code execution steps over the return statement of my service in the service call which causes the error. The puzzling thing to me is that the service is stable and runs with options A) or B) as decribed at the beginning of my post, and occurs after a varying number of messages (around 18). The former fact points to there being nothing wrong with the code (indeed I have checked that no exceptions are thrown), and the latter just serves to confuse me and is why I modified the settings on the reliable session binding. I am quite stuck on this. Can anyone suggest why the reliable session would fault in such a way?

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• Smoke testing a .NET web application

  - by pdr

  I cannot believe I'm the first person to go through this thought process, so I'm wondering if anyone can help me out with it. Current situation: developers write a web site, operations deploy it. Once deployed, a developer Smoke Tests it, to make sure the deployment went smoothly. To me this feels wrong, it essentially means it takes two people to deploy an application; in our case those two people are on opposite sides of the planet and timezones come into play, causing havoc. But the fact remains that developers know what the minimum set of tests is and that may change over time (particularly for the web service portion of our app). Operations, with all due respect to them (and they would say this themselves), are button-pushers who need a set of instructions to follow. The manual solution is that we document the test cases and operations follow that document each time they deploy. That sounds painful, plus they may be deploying different versions to different environments (specifically UAT and Production) and may need a different set of instructions for each. On top of this, one of our near-future plans is to have an automated daily deploy environment, so then we'll have to instruct a computer as to how to deploy a given version of our app. I would dearly like to add to that instructions for how to smoke test the app. Now developers are better at documenting instructions for computers than they are for people, so the obvious solution seems to be to use a combination of nUnit (I know these aren't unit tests per se, but it is a built-for-purpose test runner) and either the Watin or Selenium APIs to run through the obvious browser steps and call to the web service and explain to the Operations guys how to run those unit tests. I can do that; I have mostly done it already. But wouldn't it be nice if I could make that process simpler still? At this point, the Operations guys and the computer are going to have to know which set of tests relate to which version of the app and tell the nUnit runner which base URL it should point to (say, www.example.com = v3.2 or test.example.com = v3.3). Wouldn't it be nicer if the test runner itself had a way of giving it a base URL and letting it download say a zip file, unpack it and edit a configuration file automatically before running any test fixtures it found in there? Is there an open source app that would do that? Is there a need for one? Is there a solution using something other than nUnit, maybe Fitnesse? For the record, I'm looking at .NET-based tools first because most of the developers are primarily .NET developers, but we're not married to it. If such a tool exists using other languages to write the tests, we'll happily adapt, as long as there is a test runner that works on Windows.

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• displaying the values in textbox based on AJAX fetched entries

  - by Anurag

  hello, I've a table in which addition rows can be generatred as per the user need by clicking a javascript function. Each row has a drop down list, and based on the values of this an AJAX script fetchs some values which has to be displayed in corresponding textfields of the same row.. here is the code for HTML.. <td><div align="center"> <label> <select name="gcno1" id="gcno1" onchange="fetch_gc(this)"> <option value="0">NIL</option> <option value="2">1</option> <?php while($row=mysql_fetch_array($result)) { ?> <option value="<?php echo $row[0]; ?>"><?php echo $row[0]; ?></option> <?php }?> </select> </label> </div></td> <td><div align="center"><input name="date1" id="date1" type="text" size="10" /> </div></td> and here is the AJAX which I'm writing... xmlhttp = new XMLHttpRequest(); var value=encodeURIComponent(document.getElementById('gcno1').value); var parameters="param1="+value; xmlhttp.open("POST", 'fetch_gc.php', true); xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); xmlhttp.send(parameters); xmlhttp.onreadystatechange=function(){ if(xmlhttp.readyState == 4 && xmlhttp.status == 200) { var detail=xmlhttp.responseText.split('+'); alert(detail[0]); document.getElementsByName('date1').value=String(detail[0]); alert("life " + document.getElementById('gcno1').value); } } The alert inside the AJAX shows the correct response text, detail[0] but is unable to put the value in corresponding textbox i.e. with name 'gcno1'...... Please help me with this problem...

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• how to create a system-wide independent universal counter object primarily for Database keys?

  - by andora

  I would like to create/use a system-wide independent universal 'counter object' that can be called via COM in a thread-safe manner. The counter object will be passed an ID to identify which counter to return, handle the counting, 'persist' the count (occasionally), have reasonable performance (as fast as possible) perhaps capable of 1000 counts per second or better (1mS) and be accessible cross-process/out-of-process. The current count status must be persisted between object restarts/shutdowns. The counter object is liklely to be a 'singleton' type object implemented in some form of free-threaded dictionary, containing maybe 10 counters (perhaps 50 max). The count needs to be monotonic and consistent, (ie: guaranteed unique sequential values). Each counter should have a few methods, like reset, inc, dec, set, clear, remove. As a luxury, I would like to have a variable-increment (ie: 'step by' value). To support thread-safefty, perhaps some sorm of critical-section or mutex call. It just needs to return a long/4byte signed integer. I really want something that can be called from anywhere, including VBScript, so I figure COM is my preferred solution. The primary use of this is for database keys. I am unable to use autoinc or guid type keys and have ruled out database-generated counting systems at this point. I've spent days researching this and I have really struggled to find a solution. The best I can find is a free-threaded dictionary object that can be instantiated using COM+ from Motobit - it seems to offer all the 'basics' and I guess I could create some form of wrapper for this. So, here are my questions: Does such a 'general purpose counter-object already exist? Can you direct me to it? (MS did do an IIS/ASP object called 'MSWC.Counter' but this isn't 'cross-process'/ out-of-process component and isn't thread-safe. (but if it was, it would do!) What is the best way of creating such a Component? (I'd prefer VB6 right-now, [don't ask!] but can do in VB.NET2005 if I had to). I don't have the skills/knowledge/tools to use anything else. I am desparate for a workable solution. I need specific guidance! If anybody can code something up for me I am prepared to pay for it.

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• Insane CPU usage in QT 5.0

  - by GravityScore

  I'm having trouble using the QT framework, particularly with the paintEvent of QWidget. I have a QWidget set up, and am overriding the paintEvent of it. I need to render a bunch of rectangles (grid system), 51 by 19, leading to 969 rectangles being drawn. This is done in a for loop. Then I also need to draw an image on each on of these grids. The QWidget is added to a QMainWindow, which is shown. This works nicely, but it's using up 47% of CPU per window open! And I want to allow the user to open multiple windows like this, likey having 3-4 open at a time, which puts the CPU close to 150%. Why does this happen? Here is the paintEvent contents. The JNI calls don't cause the CPU usage, commenting them out doesn't lower it, but commenting out the p.fillRect and Renderer::renderString (which draws the image) lowers the CPU to about 5%. // Background QPainter p(this); p.fillRect(0, 0, this->width(), this->height(), QBrush(QColor(0, 0, 0))); // Lines for (int y = 0; y < Global::terminalHeight; y++) { // Line and color method ID jmethodID lineid = Manager::jenv->GetMethodID(this->javaClass, "getLine", "(I)Ljava/lang/String;"); error(); jmethodID colorid = Manager::jenv->GetMethodID(this->javaClass, "getColorLine", "(I)Ljava/lang/String;"); error(); // Values jstring jl = (jstring) Manager::jenv->CallObjectMethod(this->javaObject, lineid, jint(y)); error(); jstring cjl = (jstring) Manager::jenv->CallObjectMethod(this->javaObject, colorid, jint(y)); error(); // Convert to C values const char *l = Manager::jenv->GetStringUTFChars(jl, 0); const char *cl = Manager::jenv->GetStringUTFChars(cjl, 0); QString line = QString(l); QString color = QString(cl); // Render line for (int x = 0; x < Global::terminalWidth; x++) { QColor bg = Renderer::colorForHex(color.mid(x + color.length() / 2, 1)); // Cell location on widget int cellx = x * Global::cellWidth + Global::xoffset; int celly = y * Global::cellHeight + Global::yoffset; // Background p.fillRect(cellx, celly, Global::cellWidth, Global::cellHeight, QBrush(bg)); // String // Renders the image to the grid Renderer::renderString(p, tc, text, cellx, celly); } // Release Manager::jenv->ReleaseStringUTFChars(jl, l); Manager::jenv->ReleaseStringUTFChars(cjl, cl); }

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• Switch between speakerphone and headset on Android

  - by user210504

  Hi! I wish to know if there is a way, using which we can switch between the speaker and headset dynamically in an android application. I am using this sample code, I found online for my experiments final float frequency = 440; float increment = (float)(2*Math.PI) * frequency / 44100; // angular increment for each sample float angle = 0; AndroidAudioDevice device = new AndroidAudioDevice( ); AudioManager am = (AudioManager)getSystemService(AUDIO_SERVICE); am.setMode(AudioManager.MODE_IN_CALL); float samples[] = new float[1024]; int count = 0; while( count < 10 ) { count++; for( int i = 0; i < samples.length; i++ ) { samples[i] = (float)Math.sin( angle ) ; angle += increment; } device.writeSamples( samples ); } device.stop(); am.setMode(AudioManager.MODE_NORMAL); ---- next class public class AndroidAudioDevice { AudioTrack track; short[] buffer = new short[1024]; public AndroidAudioDevice( ) { int minSize =AudioTrack.getMinBufferSize( 44100, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT ); track = new AudioTrack( AudioManager.STREAM_VOICE_CALL, 44100, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, minSize, AudioTrack.MODE_STREAM); track.play(); } public void writeSamples(float[] samples) { fillBuffer( samples ); track.write( buffer, 0, samples.length ); } private void fillBuffer( float[] samples ) { if( buffer.length < samples.length ) buffer = new short[samples.length]; for( int i = 0; i < samples.length; i++ ) buffer[i] = (short)(samples[i] * Short.MAX_VALUE);; } public void stop() { track.stop(); } } As per my understanding this should play audio on headset, because we have not enabled the speaker phone. However, the audio is playing on the speaker phone. 1 Am I doing something wrong here? 2 What would be a way to switch between internal speaker and speaker phone dynamically for same code peice Any help will be appreciated.

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• How to access a matrix in a matlab struct's field from a mex function?

  - by B. Ruschill

  I'm trying to figure out how to access a matrix that is stored in a field in a matlab structure from a mex function. That's awfully long winded... Let me explain: I have a matlab struct that was defined like the following: matrixStruct = struct('matrix', {4, 4, 4; 5, 5, 5; 6, 6 ,6}) I have a mex function in which I would like to be able to receive a pointer to the first element in the matrix (matrix[0][0], in c terms), but I've been unable to figure out how to do that. I have tried the following: /* Pointer to the first element in the matrix (supposedly)... */ double *ptr = mxGetPr(mxGetField(prhs[0], 0, "matrix"); /* Incrementing the pointer to access all values in the matrix */ for(i = 0; i < 3; i++){ printf("%f\n", *(ptr + (i * 3))); printf("%f\n", *(ptr + 1 + (i * 3))); printf("%f\n", *(ptr + 2 + (i * 3))); } What this ends up printing is the following: 4.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 I have also tried variations of the following, thinking that perhaps it was something wonky with nested function calls, but to no avail: /* Pointer to the first location of the mxArray */ mxArray *fieldValuePtr = mxGetField(prhs[0], 0, "matrix"); /* Get the double pointer to the first location in the matrix */ double *ptr = mxGetPr(fieldValuePtr); /* Same for loop code here as written above */ Does anyone have an idea as to how I can achieve what I'm trying to, or what I am potentially doing wrong? Thanks! Edit: As per yuk's comment, I tried doing similar operations on a struct that has a field called array which is a one-dimensional array of doubles. The struct containing the array is defined as follows: arrayStruct = struct('array', {4.44, 5.55, 6.66}) I tried the following on the arrayStruct from within the mex function: mptr = mxGetPr(mxGetField(prhs[0], 0, "array")); printf("%f\n", *(mptr)); printf("%f\n", *(mptr + 1)); printf("%f\n", *(mptr + 2)); ...but the output followed what was printed earlier: 4.440000 0.000000 0.000000

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• How to learn proper C++?

  - by Chris

  While reading a long series of really, really interesting threads, I've come to a realization: I don't think I really know C++. I know C, I know classes, I know inheritance, I know templates (& the STL) and I know exceptions. Not C++. To clarify, I've been writing "C++" for more than 5 years now. I know C, and I know that C and C++ share a common subset. What I've begun to realize, though, is that more times than not, I wind up treating C++ something vaguely like "C with classes," although I do practice RAII. I've never used Boost, and have only read up on TR1 and C++0x - I haven't used any of these features in practice. I don't use namespaces. I see a list of #defines, and I think - "Gracious, that's horrible! Very un-C++-like," only to go and mindlessly write class wrappers for the sake of it, and I wind up with large numbers (maybe a few per class) of static methods, and for some reason, that just doesn't seem right lately. The professional in me yells "just get the job done," the academic yells "you should write proper C++ when writing C++" and I feel like the point of balance is somewhere in between. I'd like to note that I don't want to program "pure" C++ just for the sake of it. I know several languages. I have a good feel for what "Pythonic" is. I know what clean and clear PHP is. Good C code I can read and write better than English. The issue is that I learned C by example, and picked up C++ as a "series of modifications" to C. And a lot of my early C++ work was creating class wrappers for C libraries. I feel like my own personal C-heavy background while learning C++ has sort of... clouded my acceptance of C++ in it's own right, as it's own language. Do the weathered C++ lags here have any advice for me? Good examples of clean, sharp C++ to learn from? What habits of C does my inner-C++ really need to break from? My goal here is not to go forth and trumpet "good" C++ paradigm from rooftops for the sake of it. C and C++ are two different languages, and I want to start treating them that way. How? Where to start? Thanks in advance! Cheers, -Chris

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• How can I create the XML::Simple data structure using a Perl XML SAX parser?

  - by DVK

  Summary: I am looking a fast XML parser (most likely a wrapper around some standard SAX parser) which will produce per-record data structure 100% identical to those produced by XML::Simple. Details: We have a large code infrastructure which depends on processing records one-by-one and expects the record to be a data structure in a format produced by XML::Simple since it always used XML::Simple since early Jurassic era. An example simple XML is: <root> <rec><f1>v1</f1><f2>v2</f2></rec> <rec><f1>v1b</f1><f2>v2b</f2></rec> <rec><f1>v1c</f1><f2>v2c</f2></rec> </root> And example rough code is: sub process_record { my ($obj, $record_hash) = @_; # do_stuff } my $records = XML::Simple->XMLin(@args)->{root}; foreach my $record (@$records) { $obj->process_record($record) }; As everyone knows XML::Simple is, well, simple. And more importantly, it is very slow and a memory hog—due to being a DOM parser and needing to build/store 100% of data in memory. So, it's not the best tool for parsing an XML file consisting of large amount of small records record-by-record. However, re-writing the entire code (which consist of large amount of "process_record"-like methods) to work with standard SAX parser seems like an big task not worth the resources, even at the cost of living with XML::Simple. I'm looking for an existing module which will probably be based on a SAX parser (or anything fast with small memory footprint) which can be used to produce $record hashrefs one by one based on the XML pictured above that can be passed to $obj->process_record($record) and be 100% identical to what XML::Simple's hashrefs would have been. I don't care much what the interface of the new module is; e.g whether I need to call next_record() or give it a callback coderef accepting a record.

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• How to stream semi-live audio over internet

  - by Thomas Tempelmann

  I want to write something like Skype, i.e. I have a constant audio stream on one computer and then recompress it in a format that's suitable for a latent internet connection, receive it on the other end and play it. Let's also assume that the internet connection is fairly modern and fast, i.e. DSL or alike, no slow connections over phone and such. The involved computers will also be rather modern (Dual Core Intel CPUs at 2GHz or more). I know how to handle the audio on the machines. What I don't know is how to transmit the audio in an efficient way. The challenges are: I'd like get good audio quality across the line. The stream should be received without drops. The stream may, however, be received with a little delay (a second delay is acceptable). I imagine that the transport software could first determine the average (and max) latency, then start the stream and tell the receiver to wait for that max latency before starting to play the audio. With that, if the latency doesn't get any higher, the entire stream will be playable on the other side without stutter or drops. If, due to unexpected IP latencies or blockages, the stream does get cut off, I want to be able to notice this so that I can take actions (e.g. abort the stream) and eventually start a new transmission. What are my options if I want do use ready-made software for the compression and tranmission? I have no intention to write my own audio compression engine, really. OTOH, I plan to sell the solution in a vertical market, meaning I can afford a few dollars of license fees per copy, but not $100s. I guess the simplest solution would be to just open a TCP stream, send a few packets back and forth to determine their running time (or even use UDP for that), then use the results as the guide for my max latency value, then simply fire the audio data in its raw form (uncompressed 16 bit stereo), along with a timing code over the TCP connection. The receiver reads the data and plays it with the pre-determined delay. That might just work with the type of fast connection I expect. I just wonder if there are better solutions to reach this goal, with better performance (lower latency) and less data (compressed). BTW, I first try to implement this on OS X, but might want to do it on Windows, too, if it proves successful.

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• Foreign key pointing to different tables

  - by Álvaro G. Vicario

  I'm implementing a table per subclass design I discussed in a previous question. It's a product database where products can have very different attributes depending on their type, but attributes are fixed for each type and types are not manageable at all. I have a master table that holds common attributes: product_type ============ product_type_id INT product_type_name VARCHAR E.g.: 1 'Magazine' 2 'Web site' product ======= product_id INT product_name VARCHAR product_type_id INT -> Foreign key to product_type.product_type_id valid_since DATETIME valid_to DATETIME E.g. 1 'Foo Magazine' 1 '1998-12-01' NULL 2 'Bar Weekly Review' 1 '2005-01-01' NULL 3 'E-commerce App' 2 '2009-10-15' NULL 4 'CMS' 2 '2010-02-01' NULL ... and one subtable for each product type: item_magazine ============= item_magazine_id INT title VARCHAR product_id INT -> Foreign key to product.product_id issue_number INT pages INT copies INT close_date DATETIME release_date DATETIME E.g. 1 'Foo Magazine Regular Issue' 1 89 52 150000 '2010-06-25' '2010-06-31' 2 'Foo Magazine Summer Special' 1 90 60 175000 '2010-07-25' '2010-07-31' 3 'Bar Weekly Review Regular Issue' 2 12 16 20000 '2010-06-01' '2010-06-02' item_web_site ============= item_web_site_id INT name VARCHAR product_id INT -> Foreign key to product.product_id bandwidth INT hits INT date_from DATETIME date_to DATETIME E.g. 1 'The Carpet Store' 3 10 90000 '2010-06-01' NULL 2 'Penauts R Us' 3 20 180000 '2010-08-01' NULL 3 'Springfield Cattle Fair' 4 15 150000 '2010-05-01' '2010-10-31' Now I want to add some fees that relate to one specific item. Since there are very little subtypes, it's feasible to do this: fee === fee_id INT fee_description VARCHAR item_magazine_id INT -> Foreign key to item_magazine.item_magazine_id item_web_site_id INT -> Foreign key to item_web_site.item_web_site_id net_price DECIMAL E.g.: 1 'Front cover' 2 NULL 1999.99 2 'Half page' 2 NULL 500.00 3 'Square banner' NULL 3 790.50 4 'Animation' NULL 3 2000.00 I have tight foreign keys to handle cascaded editions and I presume I can add a constraint so only one of the IDs is NOT NULL. However, my intuition suggests that it would be cleaner to get rid of the item_WHATEVER_id columns and keep a separate table: fee_to_item =========== fee_id INT -> Foreign key to fee.fee_id product_id INT -> Foreign key to product.product_id item_id INT -> ??? But I can't figure out how to create foreign keys on item_id since the source table varies depending on product_id. Should I stick to my original idea?

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