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• Arguments? Path filing wrong? [on hold]

  - by user3034947

  I'm working through the Java SE 7 programming activity and I'm having trouble sort of understanding how arguments work. Here's the code: public class CopyFileTree implements FileVisitor<Path> { private Path source; private Path target; public CopyFileTree(Path source, Path target) { this.source = source; this.target = target; } @Override public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) { // Your code goes here Path newdir = target.resolve(source.relativize(dir)); try { Files.copy(dir, newdir); } catch (FileAlreadyExistsException x) { // ignore } catch (IOException x) { System.err.format("Unable to create: %s: %s%n", newdir, x); return SKIP_SUBTREE; } return CONTINUE; } @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs ) { // Your code goes here Path newdir = target.resolve(source.relativize(file)); try { Files.copy(file, newdir, REPLACE_EXISTING); } catch (IOException x) { System.err.format("Unable to copy: %s: %s%n", source, x); } return CONTINUE; } @Override public FileVisitResult postVisitDirectory(Path dir, IOException exc ) { return CONTINUE; } @Override public FileVisitResult visitFileFailed(Path file, IOException exc ) { if (exc instanceof FileSystemLoopException) { System.err.println("cycle detected: " + file); } else { System.err.format("Unable to copy: %s: %s%n", file, exc); } return CONTINUE; } } It says to test this I need to enter arguments in properties of the project which I did? Can someone clarity what I'm doing wrong?

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• Separate update and render

  - by NSAddict

  I'm programming a simple Snake in Java. I'm a complete newbie when it comes to Java and Game Developing, so please bear with me ;) Until now, I have been using a UI thread, as well as a update-thread. The update thread just set the position, set the GameObjects, and so on. I didn't think much of concurrency, but now I've come to a problem. I wanted to modify the ArrayList<GameObject>, but it throws a java.util.ConcurrentModificationException. With a little research I found out that this happens because the two threads are trying to access the variables at the same time. But I didn't really find a way to prevent this. I thought about copying the array and swapping them out when the rendering is finished, but I would have to deep-copy them, which isn't really the best solution in my opinion. It probably eats up more CPU resources than a single-threaded game. Are there any other ways to prevent this? Thanks a lot for your help!

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• Working hours for a newbie

  - by martani_net

  This is not a very related software / hardware question, but it's too related to the Tech world. I started a work 3 months before, and I am about to finish this week, and my boss asked me to do a planning of what I've done so far, I think this is totally ok, but he is asking for what I did each day with the hours I spent in these days. This is a sample of what I sent him M T W T F week 29/06 to 03/07 compréhension et analyse du problématique * * architecture de l'application * * * which translates to first task, I spent Monday + Tuesday on, and the last W, T, and Friday. What he is asking for, is what I've done in each day, with the timing I spent on (obviously, I don't think I remember, and because for a programmer, there are no sequence tasks, I mean I change code in a class, then change it in another to fit with the new one and so far) So my question is: is what he asking normal? and if so how can I detail the planning for the 3 months. [update] I used the email account we use to test our software with the extern servers, and I got a good view of what I was doing in every day :), a generic view but it helped too much (PS: The boss doesn't know anything about programming, for him, it's like writing lines and get results back nothing more )

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• What is the most effective approach to learn an unfamiliar complex program? [closed]

  - by bdroc

  Possible Duplicate: How do you dive into large code bases? I have quite a bit of experience with different programming languages and writing small and functional programs for a variety of purposes. My coding skills aren't what I have a problem with. In fact, I've written a decent web application from scratch for my startup. However, I have trouble jumping into unfamiliar applications. What's the most effective way to approach learning a new program's structure and/or architecture so that I can start attacking the code effectively? Are there useful tools for their respective languages (Python and Java are my two primary languages)? Should I be starting with just looking at function names or documentation? How do you veterans approach this problem? I find this has to be with minimal help from coworkers or contributors who are already familiar with the application and have better things to do than help me. I'd love to practice this skill in an open source project so any suggestions for starting points (maybe mildly complex) would be great too!

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• Why most people change from being a contractor to full time at my companies, but not the other way around?

  - by ????

  I have seen most people changed from being a contractor to being a full time employee, but not the other way around. And that happened in startups that had maybe 20% chance of IPO or being acquired, and another that had maybe a 50% chance. As far as I know, the rate (even for a 3 year experience graphics designer, or a programmer), can be $75 to $80 an hour. While a programmer with 15 years of experience may get $120,000 per year. So, the programmer with 15 years of programming experience earns $10,000 per month. At the same time, the programmer with 3 year of experience or the graphics designer will get $14,000 per month ($80 x 22 days x 8 hours). I know I have to buy my own insurance, but I can't imagine buying those for $4,000 each month... maybe $200, $300 at most. I probably need to pay Social Security (FICA) both way (myself and as self-employed = $210 x 2), but still, each month there will be extra $3,000 of income. So is the above calculation correct? But most often, I do see contractors wanting or becoming full time, but not full time employees becoming a contractor. Does somebody know what the reason is?

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• I failed FizzBuzz, would you hire me? [closed]

  - by ja_programmer

  I'm a developer with a CS degree and have work experience doing development in a number of languages for almost 3 years. Today had an interview (2nd interview) with a panel of people. Overall it went quite well, I prepared for most of the questions and felt ready for anything. At the end of the interview, they gave me ONE programming question...a problem like FizzBuzz (without the print the number part). I believe I made too many mistakes and thus have "failed" it. Is all hope lost for me? Here is my code: void FizzBuzz() { for(int i = 0; i <= 100; i++) { bool isThree = i % 3; bool isFive = i % 5; if (isThree) { print "Fizz\n"; } else if(isFive) { print "Buzz\n"; } else { print "FizzBuzz\n"; } } } As you can see I messed up the bools which should have the syntax i % 3 == 0; If I'm remembering the question right I also put an else instead of an elseif with isThree && isFive. I was quite stressed, but that's no excuse for missing a simple problem. So the question is, if my work history and personality fit with the job and this is the only code you've seen, would you hire me?

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• ???????????! Java EE 6???????????????/???????!!????UFJ????????????????????????Java EE 6??????JavaOne Tokyo 2012?????|WebLogic Channel|??????

  - by ???02

  ??UFJ?????????????????????????IT??????? ?????????UFJ?????????/????????2007?7????????????JavaEE5?????????Java EE??????????????????????2012?4???????JavaOne Tokyo 2012??????????Java EE 6?????????????????????????Java EE 6???????????????????????????????????????????Java EE 6???????"??????????????"???????????????????????????????????(???)Java EE 6?????????·?????????????????UFJ??????????????? IT??????? ????????　???????????????????Java EE????????????????????J2EE 1.4??????????????????????????????(EoD:Ease of Development)?????????????????????2006??????Java EE 5?????????·??????????????????????EoD????????????????Java EE 5????????????????????????????Java Servlet?JavaServer Faces(JSF)?????????????API?EoD????????????Dependency Injection(DI???????)?Aspect Oriented Programming(AOP???????????????)???????????????RESTful Web?????API????????????????　????????????????2009?12?????????????Java EE 6??????Java EE 6???????????????·??????????????????????????????????????????????????·??????????????????????????????????????????????????????Java EE 6????????????????????????Java EE??????Java EE 6????????????　Java EE 6????1?????????????????????????????????????Java EE 6???JSF??????1.2??2.0??????????????JSF 1.2?????????????????????????????????????????????????????????????????????????????????JSF 2.0??????????????????????????????????(???)????????Ajax??????????????????????????????????????????????????????JSF????????????????UI?????????????????(?????)?????HTML???JSF???????????HTML?JSF????????????(?)???????????????JSF 2.0????????????　???EJB??????3.0??3.1??????????EJB 3.1???????EoD???????????????????????????????????????Singleton??????????Session Bean????????????Java Persistence API(JPA)??????1.0??2.0????????????????????(?????)??????????????　???????Java EE 6???????API???/???????????????Java EE 6?????"?????"???????Contexts and Dependency Injection(CDI) 1.0?????????JSF?EJB?JPA???????????DI?????????????????????Java EE 5???DI????????Java EE?????????????????????????????CDI??????????JavaBeans????DI???????????????????CDI??????????????????·?????????????1???????????????(???????)?????????????????????????????????·???????　??????????API?????1??????????Java API for RESTful Web Services(JAX-RS) 1.1?????????????????Java?RESTful Web????????????API?????????2???????1???SOAP????Web??????????????????????????????????????????????????1???Web??????????JavaScript????·???·???????????????????JAX-RS???　????????????????????Java EE 6?????????????????????????EoD???????:???????JSF?????????????????????????:?????????API?????????????????????????????????????API?Java EE????????????????????????????????EJB?????EAR???????????WAR??????????????????????????????:JNDI????????????(?????)????????????Java EE 6??????????????????????!　?????????????·???????????????????????????Java EE 6??????????Java EE 5????????????????????????????????????????????Web?????????????????????Model/View/Controller(MVC)???????????????????????????(1)HTML?JSF???????????(JSF 2.0???)(2)????UI????????????????(JSF 2.0???)(3)JavaScript+JAX-RS?????????MVC????(1)HTML?JSF???????????(JSF 2.0???)(2)????UI????????????????(JSF 2.0???)(3)JavaScript+JAX-RS?????　??????(3)JavaScript+JAX-RS???????????????????????????????????·??????????·???????????????????????????????????????????????????????????(???)??????　???????????3?????(3????)??????????????????3?????????????????????????????????????????????????????????????????????????????/????????????????????????????????????????????????????????·???????????????????????????????????????　??????????????3??????????????????????????????????????????????????????????????????????????????????????????Java EE 6???CDI????????????·???(JSF?EJB?JPA)??????????????????????EJB??????WAR?????????????????????????????????????????????????????????????????????????????????????????????????? Java EE 6??????????????　???????????????????????????????(?????·???????)???????Java EE 6???????????????????????????????????????????????·?????????????????????????Java EE 6???????????????????????API????????????????????????????????????·????????Java EE 6???????　????Java EE 6????????????????????????????????Java EE 6???????????????????????Java EE 6??????????????????????????????????????????????Java EE 6???????????????????????????

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• Xcode/iPhone Development 6 months in - Annoyances

  - by clearbrian

  Hi I've been iPhone programming for 6 months and come from a PC/Java/Eclipse background and still have a few annoyances with Xcode/iPhone programming I wonder are there any shortcuts to. Is there any way to prevent multiple windows opening all the time in XCode? a) When you click on the Errors/Warnings in the bottom right of the status bar build errors are shown in separate window. Any way to get these to show in the main editor? b) Anyway to get debugger to appear in main editor. I have a big screen iMac and it's still window hell on Macs. When you come from Alt-Tab the Mac is a nightmare. 2) Anyway to get a toolbar item on the main editor to: a) Open Console (I know CMD-thingy-R) b) Open Break points (you have to open Debugger first then breakpoints) I know there's keyboard shortcuts but I have only left hand free others on the trackball so any keys on right hand side of keyboard are too far. I know you can add Finder toolbar scripts (just wondering if anyway to extend Xcode). Are there utilities to extend Xcode? Scripts/Automator/Any Services I can setup to help. Can you automate Xcode like you can with Windows/ActiveX/VBA 3) Limit lookups using CMD + double click. If I double click on a variable to find its definition using CMD + double click it shows every occurrence of all variables with that name. (annoying it you name all you maps mapView) Anyway to get it to limit to the current class or at least order so current class is first. 4) Find doesn't seem to loop backwards if result all above cursor position I'm in a class and I hit CMD + F for find. Find box appears. I enter some text hit return. It says I have x matches but only back arrow is highlight in Find But when I hit < it does nothing. I need to scroll to the top and redo the search. If the text is both forwards and backwards then both < are highlighted and it works. is this a bug or a 'feature' Missing Eclipse features I have been looking at the User Script menu but was wondering how powerful they are? 5) any scripts around to generate source from members such as description: @property @synthesize if I add a new member, run a script will generate @property/@syntesize and release in dealloc 7) any good sites for scripts? SCM Im having problems with SCM and Folders on HD under project Classes directory. You get a library e.g. JSON. It usually comes as a folder. You copy it to the /Classes for your project. /Classes/JSON I create a Group for the Library in Xcode under Classes group. Classes JSON I drag the files from the folder into xcode into the JSON Group. I add them to the SCM and icon changes from ? to A but if I try and commit them it say folder /JSON is not under SCM. Can you drag a folder into Xcode so that it AND its files get included in SCM? Anyway to stop Xcode Help from being on top all the time. I keep feeling like punching it and telling it to get out of the way! :) I dont mind it open just not in the way once I've finished. Yes I know I can Ctrl-W Sites: the main site I use to learn Obj-C are : stackoverflow.com Google code Search - tonnes of full apps on here http://www.iphonedevsdk.com/forum/iphone-sdk-development/ Apple Developers Forums (anyway to get RSS feed to these or is that blasphemy :) ) Safari - 100s of IT book though prob too many to keep up :) any others? Any site that gives simple examples for Obj-C/ UIKit The docs just show the methods but actual examples (Google code search has helped a lot here)

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• How to write a Mork File Format file in Java?

  - by Sumit Ghosh

  Iam working on a project which involves writing a Mork File (Mork is a database format used by Mozilla to store url history and other information.) It has been replaced by an enhanced version of SQLite in latest Mozilla 3.0. Now I have the code for parsing a Mork File , but Iam struggling a bit with this part of the the file. <(A9=3)(81=)([email protected])(80=0)(85=2)(86=4ac18267)(83=1) (87=Mark)(88=Colbath)(89=Mark Colbath)([email protected])(8B [email protected])(8C=512-282-2509)(8D=+504-9907-1342)(8E=512-282-2510) (8F=512-282-2511)(90=512-282-2512)(91=Two Blocks Past Oxen Team)(92 =Villa Alicia)(93=Siguatepeque)(94=Comayagua)(95=NA)(96=Honduras) (97=9309 Heatherwood Dr)(98=Apartment 1)(99=Austin)(9A=TX)(9B=78748) (9C=USA)(9D=Programmer)(9E=Programming)(9F=MPC Solutions)(A0 =rentaprogrammer)(A1=http://www.mpcsol.com)(A2 =http://www.jesuslovesthelittlechildren.org)(A3=Hannah)(A4=John) (A5=Faith)(A6=Timothy)(A7=Some notes go here.)(A8 [email protected])> {1:^80 {(k^C0:c)(s=9)} [1:^82(^BF=3)] [1(^83=)(^84=)(^85=)(^86=)(^87=)(^88=)(^89^82)(^8A^82)(^8B=)(^8C=) (^8D=)(^8E=0)(^8F=2)(^90=0)(^91=)(^92=)(^93=)(^94=)(^95=)(^96=) (^97=)(^98=)(^99=)(^9A=)(^9B=)(^9C=)(^9D=)(^9E=)(^9F=)(^A0=)(^A1=) (^A2=)(^A3=)(^A4=)(^A5=)(^A6=)(^A7=)(^A8=)(^A9=)(^AA=)(^AB=)(^AC=) (^AD=)(^AE=)(^AF=)(^B0=)(^B1=)(^B2=)(^B3=)(^B4=)(^B5=)(^B6=)(^B7=) (^B8=)(^B9=)(^BA=)(^BB=)(^BC^86)(^BD=1)] [2(^83^87)(^84^88)(^85=)(^86=)(^87^89)(^88=)(^89^8A)(^8A^8A)(^8B^8B) (^8C=)(^8D=)(^8E=2)(^8F=0)(^90=1)(^91^8C)(^92^8D)(^93^8E)(^94^8F) (^95^90)(^96=)(^97=)(^98=)(^99=)(^9A=)(^9B^91)(^9C^92)(^9D^93)(^9E^94) (^9F=NA)(^A0^96)(^A1^97)(^A2^98)(^A3^99)(^A4=TX)(^A5^9B)(^A6^9C) (^A7^9D)(^A8^9E)(^A9^9F)(^AA^A0)(^AB=)(^AC=)(^AD=)(^AE=)(^AF=)(^B0=) (^B1=)(^B2^A1)(^B3^A2)(^B4=)(^B5=)(^B6=)(^B7^A3)(^B8^A4)(^B9^A5) (^BA^A6)(^BB^A7)(^BC=0)(^BD=2)] [3(^83=)(^84=)(^85=)(^86=)(^87=)(^88=)(^89^A8)(^8A^A8)(^8B=)(^8C=) (^8D=)(^8E=0)(^8F=0)(^90=0)(^91=)(^92=)(^93=)(^94=)(^95=)(^96=) (^97=)(^98=)(^99=)(^9A=)(^9B=)(^9C=)(^9D=)(^9E=)(^9F=)(^A0=)(^A1=) (^A2=)(^A3=)(^A4=)(^A5=)(^A6=)(^A7=)(^A8=)(^A9=)(^AA=)(^AB=)(^AC=) (^AD=)(^AE=)(^AF=)(^B0=)(^B1=)(^B2=)(^B3=)(^B4=)(^B5=)(^B6=)(^B7=) (^B8=)(^B9=)(^BA=)(^BB=)(^BC=0)(^BD=3)]} Can someone tell me how this part of the Mork file relates to the data given below? run: NickName=,LastModifiedDate=4ac18267,FaxNumberType=,BirthMonth=,LastName=,HomePhone=,WorkCountry=,HomePhoneType=,PreferMailFormat=0,CellularNumber=,FamilyName=,[email protected],AnniversaryMonth=,HomeCity=,WorkState=,HomeCountry=,PhoneticFirstName=,PhoneticLastName=,HomeState=,WorkAddress=,WebPage1=,WebPage2=,HomeAddress2=,WorkZipCode=,_AimScreenName=,AnniversaryYear=,WorkPhoneType=,Notes=,WorkAddress2=,WorkPhone=,Custom3=,Custom4=,Custom1=,Custom2=,PagerNumber=,AnniversaryDay=,WorkCity=,AllowRemoteContent=0,CellularNumberType=,FaxNumber=,PopularityIndex=2,FirstName=,SpouseName=,CardType=,Department=,Company=,HomeAddress=,BirthDay=,SecondEmail=,RecordKey=1,DisplayName=,DefaultEmail=,DefaultAddress=,BirthYear=,Category=,PagerNumberType=,[email protected],JobTitle=,HomeZipCode=, NickName=,LastModifiedDate=0,FaxNumberType=,BirthMonth=,LastName=Colbath,HomePhone=+504-9907-1342,WorkCountry=USA,HomePhoneType=,PreferMailFormat=2,CellularNumber=512-282-2512,FamilyName=,[email protected],AnniversaryMonth=,HomeCity=Siguatepeque,WorkState=TX,HomeCountry=Honduras,PhoneticFirstName=,PhoneticLastName=,HomeState=Comayagua,WorkAddress=9309 HeatherwoodDr,WebPage1=http://www.mpcsol.com,WebPage2=http://www.jesuslovesthelittlechildren.org,HomeAddress2=VillaAlicia,WorkZipCode=78748,_AimScreenName=rentaprogrammer,AnniversaryYear=,WorkPhoneType=,Notes=Some notes go here.,WorkAddress2=Apartment 1,WorkPhone=512-282-2509,Custom3=Faith,Custom4=Timothy,Custom1=Hannah,Custom2=John,PagerNumber=512-282-2511,AnniversaryDay=,WorkCity=Austin,AllowRemoteContent=1,CellularNumberType=,FaxNumber=512-282-2510,PopularityIndex=0,FirstName=Mark,SpouseName=,CardType=,Department=Programming,Company=MPC Solutions,HomeAddress=Two Blocks Past Oxen Team,BirthDay=,[email protected],RecordKey=2,DisplayName=Mark Colbath,DefaultEmail=,DefaultAddress=,BirthYear=,Category=,PagerNumberType=,[email protected],JobTitle=Programmer,HomeZipCode=NA, NickName=,LastModifiedDate=0,FaxNumberType=,BirthMonth=,LastName=,HomePhone=,WorkCountry=,HomePhoneType=,PreferMailFormat=0,CellularNumber=,FamilyName=,[email protected],AnniversaryMonth=,HomeCity=,WorkState=,HomeCountry=,PhoneticFirstName=,PhoneticLastName=,HomeState=,WorkAddress=,WebPage1=,WebPage2=,HomeAddress2=,WorkZipCode=,_AimScreenName=,AnniversaryYear=,WorkPhoneType=,Notes=,WorkAddress2=,WorkPhone=,Custom3=,Custom4=,Custom1=,Custom2=,PagerNumber=,AnniversaryDay=,WorkCity=,AllowRemoteContent=0,CellularNumberType=,FaxNumber=,PopularityIndex=0,FirstName=,SpouseName=,CardType=,Department=,Company=,HomeAddress=,BirthDay=,SecondEmail=,RecordKey=3,DisplayName=,DefaultEmail=,DefaultAddress=,BirthYear=,Category=,PagerNumberType=,[email protected],JobTitle=,HomeZipCode=, I have been breaking my head for almost 2 days now, please someone who is part of the mozilla team can help, it would be really appreciated.

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• What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

  - by Tom Ritter

  I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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• python: what are efficient techniques to deal with deeply nested data in a flexible manner?

  - by AlexandreS

  My question is not about a specific code snippet but more general, so please bear with me: How should I organize the data I'm analyzing, and which tools should I use to manage it? I'm using python and numpy to analyse data. Because the python documentation indicates that dictionaries are very optimized in python, and also due to the fact that the data itself is very structured, I stored it in a deeply nested dictionary. Here is a skeleton of the dictionary: the position in the hierarchy defines the nature of the element, and each new line defines the contents of a key in the precedent level: [AS091209M02] [AS091209M01] [AS090901M06] ... [100113] [100211] [100128] [100121] [R16] [R17] [R03] [R15] [R05] [R04] [R07] ... [1263399103] ... [ImageSize] [FilePath] [Trials] [Depth] [Frames] [Responses] ... [N01] [N04] ... [Sequential] [Randomized] [Ch1] [Ch2] Edit: To explain a bit better my data set: [individual] ex: [AS091209M02] [imaging session (date string)] ex: [100113] [Region imaged] ex: [R16] [timestamp of file] ex [1263399103] [properties of file] ex: [Responses] [regions of interest in image ] ex [N01] [format of data] ex [Sequential] [channel of acquisition: this key indexes an array of values] ex [Ch1] The type of operations I perform is for instance to compute properties of the arrays (listed under Ch1, Ch2), pick up arrays to make a new collection, for instance analyze responses of N01 from region 16 (R16) of a given individual at different time points, etc. This structure works well for me and is very fast, as promised. I can analyze the full data set pretty quickly (and the dictionary is far too small to fill up my computer's ram : half a gig). My problem comes from the cumbersome manner in which I need to program the operations of the dictionary. I often have stretches of code that go like this: for mk in dic.keys(): for rgk in dic[mk].keys(): for nk in dic[mk][rgk].keys(): for ik in dic[mk][rgk][nk].keys(): for ek in dic[mk][rgk][nk][ik].keys(): #do something which is ugly, cumbersome, non reusable, and brittle (need to recode it for any variant of the dictionary). I tried using recursive functions, but apart from the simplest applications, I ran into some very nasty bugs and bizarre behaviors that caused a big waste of time (it does not help that I don't manage to debug with pdb in ipython when I'm dealing with deeply nested recursive functions). In the end the only recursive function I use regularly is the following: def dicExplorer(dic, depth = -1, stp = 0): '''prints the hierarchy of a dictionary. if depth not specified, will explore all the dictionary ''' if depth - stp == 0: return try : list_keys = dic.keys() except AttributeError: return stp += 1 for key in list_keys: else: print '+%s> [\'%s\']' %(stp * '---', key) dicExplorer(dic[key], depth, stp) I know I'm doing this wrong, because my code is long, noodly and non-reusable. I need to either use better techniques to flexibly manipulate the dictionaries, or to put the data in some database format (sqlite?). My problem is that since I'm (badly) self-taught in regards to programming, I lack practical experience and background knowledge to appreciate the options available. I'm ready to learn new tools (SQL, object oriented programming), whatever it takes to get the job done, but I am reluctant to invest my time and efforts into something that will be a dead end for my needs. So what are your suggestions to tackle this issue, and be able to code my tools in a more brief, flexible and re-usable manner?

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• Error in python - don't understand

  - by Jasper

  Hi, I'm creating a game, and am quite new to Python generally. I created a function 'descriptionGenerator()' which generates a description for characters and objects either randomly or using variables passed to it. It seemed to be working, but every now and then it wouldn't work correctly. So i placed it in a loop, and it never seems to be able to complete the loop without one of the iterations having this problem. The code is as follows: #+------------------------------------------+ #| Name: bitsandpieces.py | #| A module for the 'Europa I' game | #| created for the Game Making Competition | #| | #| Date Created/Modified: | #| 3/4/10 | 3/4/10 | #+------------------------------------------+ # Import the required modules # Import system modules: import time import random # Import 3rd party modules: # Import game modules: # Define the 'descriptionGenerator()' function def descriptionGenerator(descriptionVariables): descriptionVariableSize = len(descriptionVariables) if descriptionVariables[0] == 'char': # If there is only one variable ('char'), create a random description if descriptionVariableSize == 1: # Define choices for descriptionVariables to be generated from gender_choices = ['male', 'female'] hair_choices = ['black', 'red', 'blonde', 'grey', 'brown', 'blue'] hair_choices2 = ['long', 'short', 'cropped', 'curly'] size_choices = ['tubby', 'thin', 'fat', 'almost twig-like'] demeanour_choices = ['glowering', 'bright', 'smiling', 'sombre', 'intelligent'] impression_choices = ['likeable', 'unlikeable', 'dangerous', 'annoying', 'afraid'] # Define description variables gender = random.choice(gender_choices) height = str(float('0.' + str(random.randint(1, 9))) + float(random.randint(1, 2))) if float(height) > 1.8: height_string = 'tall' if float(height) > 2: height_string = 'very tall' elif float(height) < 1.8 and float(height) > 1.5: height_string = 'average' elif float(height) < 1.5: height_string = 'short' if float(height) < 1.3: height_string = 'very short' hair = random.choice(hair_choices2) + ' ' + random.choice(hair_choices) size = random.choice(size_choices) demeanour = random.choice(demeanour_choices) impression = random.choice(impression_choices) # Collect description variables in list 'randomDescriptionVariables' randomDescriptionVariables = ['char', gender, height, height_string, hair, size, demeanour, impression] # Generate description using the 'descriptionGenerator' function descriptionGenerator(randomDescriptionVariables) # Generate the description of a character using the variables passed to the function elif descriptionVariableSize == 8: if descriptionVariables[1] == 'male': if descriptionVariables[7] != 'afraid': print """A %s man, about %s m tall. He has %s hair and is %s. He is %s and you get the impression that he is %s.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[7] == 'afraid': print """A %s man, about %s m tall. He has %s hair and is %s. He is %s.\nYou feel that you should be %s of him.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[1] == 'female': if descriptionVariables[7] != 'afraid': print """A %s woman, about %s m tall. She has %s hair and is %s. She is %s and you get the impression that she is %s.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) elif descriptionVariables[7] == 'afraid': print """A %s woman, about %s m tall. She has %s hair and is %s. She is %s.\nYou feel that you should be %s of her.""" %(descriptionVariables[3], descriptionVariables[2], descriptionVariables[4], descriptionVariables[5], descriptionVariables[6], descriptionVariables[7]) else: pass elif descriptionVariables[0] == 'obj': # Insert code here 2 deal with object stuff pass print print myDescriptionVariables = ['char'] i = 0 while i < 30: print print print descriptionGenerator(myDescriptionVariables) i = i + 1 time.sleep(10) When it fails to properly execute it says this: Traceback (most recent call last): File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/Code/Code 2.0/bitsandpieces.py", line 79, in <module> descriptionGenerator(myDescriptionVariables) File "/Users/Jasper/Development/Programming/MyProjects/Game Making Challenge/Europa I/Code/Code 2.0/bitsandpieces.py", line 50, in descriptionGenerator randomDescriptionVariables = ['char', gender, height, height_string, hair, size, demeanour, impression] UnboundLocalError: local variable 'height_string' referenced before assignment Thanks for any help with this

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• Analyzing bitmaps produced by NSAffineTransform and CILineOverlay filters

  - by Adam

  I am trying to manipulate an image using a chain of CIFilters, and then examine each byte of the resulting image (bitmap). Long term, I do not need to display the resulting image (bitmap) -- I just need to "analyze" it in memory. But near-term I am displaying it on screen, to help with debugging. I have some "bitmap examination" code that works as expected when examining the NSImage (bitmap representation) I use as my input (loaded from a JPG file into an NSImage). And it SOMETIMES works as expected when I use it on the outputBitmap produced by the code below. More specifically, when I use an NSAffineTransform filter to create outputBitmap, then outputBitmap contains the data I would expect. But if I use a CILineOverlay filter to create the outputBitmap, none of the bytes in the bitmap have any data in them. I believe both of these filters are working as expected, because when I display their results on screen (via outputImageView), they look "correct." Yet when I examine the outputBitmaps, the one created from the CILineOverlay filter is "empty" while the one created from NSAffineTransfer contains data. Furthermore, if I chain the two filters together, the final resulting bitmap only seems to contain data if I run the AffineTransform last. Seems very strange, to me??? My understanding (from reading the CI programming guide) is that the CIImage should be considered an "image recipe" rather than an actual image, because the image isn't actually created until the image is "drawn." Given that, it would make sense that the CIimage bitmap doesn't have data -- but I don't understand why it has data after I run the NSAffineTransform but doesn't have data after running the CILineOverlay transform? Basically, I am trying to determine if creating the NSCIImageRep (ir in the code below) from the CIImage (myResult) is equivalent to "drawing" the CIImage -- in other words if that should force the bitmap to be populated? If someone knows the answer to this please let me know -- it will save me a few hours of trial and error experimenting! Finally, if the answer is "you must draw to a graphics context" ... then I have another question: would I need to do something along the lines of what is described in the Quartz 2D Programming Guide: Graphics Contexts, listing 2-7 and 2-8: drawing to a bitmap graphics context? That is the path down which I am about to head ... but it seems like a lot of code just to force the bitmap data to be dumped into an array where I can get at it. So if there is an easier or better way please let me know. I just want to take the data (that should be) in myResult and put it into a bitmap array where I can access it at the byte level. And since I already have code that works with an NSBitmapImageRep, unless doing it that way is a bad idea for some reason that is not readily apparent to me, then I would prefer to "convert" myResult into an NSBitmapImageRep. CIImage * myResult = [transform valueForKey:@"outputImage"]; NSImage *outputImage; NSCIImageRep *ir = [NSCIImageRep alloc]; ir = [NSCIImageRep imageRepWithCIImage:myResult]; outputImage = [[[NSImage alloc] initWithSize: NSMakeSize(inputImage.size.width, inputImage.size.height)] autorelease]; [outputImage addRepresentation:ir]; [outputImageView setImage: outputImage]; NSBitmapImageRep *outputBitmap = [[NSBitmapImageRep alloc] initWithCIImage: myResult]; Thanks, Adam

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• Where do I start ?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be learning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• bubble sort on array of c structures not sorting properly

  - by xmpirate

  I have the following program for books record and I want to sort the records on name of book. the code isn't showing any error but it's not sorting all the records. #include "stdio.h" #include "string.h" #define SIZE 5 struct books{ //define struct char name[100],author[100]; int year,copies; }; struct books book1[SIZE],book2[SIZE],*pointer; //define struct vars void sort(struct books *,int); //define sort func main() { int i; char c; for(i=0;i<SIZE;i++) //scanning values { gets(book1[i].name); gets(book1[i].author); scanf("%d%d",&book1[i].year,&book1[i].copies); while((c = getchar()) != '\n' && c != EOF); } pointer=book1; sort(pointer,SIZE); //sort call i=0; //printing values while(i<SIZE) { printf("##########################################################################\n"); printf("Book: %s\nAuthor: %s\nYear of Publication: %d\nNo of Copies: %d\n",book1[i].name,book1[i].author,book1[i].year,book1[i].copies); printf("##########################################################################\n"); i++; } } void sort(struct books *pointer,int n) { int i,j,sorted=0; struct books temp; for(i=0;(i<n-1)&&(sorted==0);i++) //bubble sort on the book name { sorted=1; for(j=0;j<n-i-1;j++) { if(strcmp((*pointer).name,(*(pointer+1)).name)>0) { //copy to temp val strcpy(temp.name,(*pointer).name); strcpy(temp.author,(*pointer).author); temp.year=(*pointer).year; temp.copies=(*pointer).copies; //copy next val strcpy((*pointer).name,(*(pointer+1)).name); strcpy((*pointer).author,(*(pointer+1)).author); (*pointer).year=(*(pointer+1)).year; (*pointer).copies=(*(pointer+1)).copies; //copy back temp val strcpy((*(pointer+1)).name,temp.name); strcpy((*(pointer+1)).author,temp.author); (*(pointer+1)).year=temp.year; (*(pointer+1)).copies=temp.copies; sorted=0; } *pointer++; } } } My Imput The C Programming Language X Y Z 1934 56 Inferno Dan Brown 1993 453 harry Potter and the soccers stone J K Rowling 2012 150 Ruby On Rails jim aurther nil 2004 130 Learn Python Easy Way gmaps4rails 1967 100 And the output ########################################################################## Book: Inferno Author: Dan Brown Year of Publication: 1993 No of Copies: 453 ########################################################################## ########################################################################## Book: The C Programming Language Author: X Y Z Year of Publication: 1934 No of Copies: 56 ########################################################################## ########################################################################## Book: Ruby On Rails Author: jim aurther nil Year of Publication: 2004 No of Copies: 130 ########################################################################## ########################################################################## Book: Learn Python Easy Way Author: gmaps4rails Year of Publication: 1967 No of Copies: 100 ########################################################################## ########################################################################## Book: Author: Year of Publication: 0 No of Copies: 0 ########################################################################## We can see the above sorting is wrong? What I'm I doing wrong?

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• How do I learn algorithms?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• Separation of presentation and business logic in PHP

  - by Markus Ossi

  I am programming my first real PHP website and am wondering how to make my code more readable to myself. The reference book I am using is PHP and MySQL Web Development 4th ed. The aforementioned book gives three approaches to separating logic and content: include files function or class API template system I haven't chosen any of these yet, as wrapping my brains around these concepts is taking some time. However, my code has become some hybrid of the first two as I am just copy-pasting away here and modifying as I go. On presentation side, all of my pages have these common elements: header, top navigation, sidebar navigation, content, right sidebar and footer. The function-based examples in the book suggest that I could have these display functions that handle all the presentation example. So, my page code will be like this: display_header(); display_navigation(); display_content(); display_footer(); However, I don't like this because the examples in the book have these print statements with HTML and PHP mixed up like this: echo "<tr bgcolor=\"".$color."\"><td><a href=\"".$url."\">" ... I would rather like to have HTML with some PHP in the middle, not the other way round. I am thinking of making my pages so that at the beginning of my page, I will fetch all the data from database and put it in arrays. I will also get the data for variables. If there are any errors in any of these processes, I will put them into error strings. Then, at the HTML code, I will loop through these arrays using foreach and display the content. In some cases, there will be some variables that will be shown. If there is an error variable that is set, I will display that at the proper position. (As a side note: The thing I do not understand is that in most example code, if some database query or whatnot gives an error, there is always: else echo 'Error'; This baffles me, because when the example code gives an error, it is sometimes echoed out even before the HTML has started...) For people who have used ASP.NET, I have gotten somewhat used to the code-behind files and lblError and I am trying to do something similar here. The thing I haven't figured out is how could I do this "do logic first, then presentation" thing so that I would not have to replicate for example the navigation logic and navigation presentation in all of the pages. Should I do some include files or could I use functions here but a little bit differently? Are there any good articles where these "styles" of separating presentation and logic are explained a little bit more thoroughly. The book I have only has one paragraph about this stuff. What I am thinking is that I am talking about some concepts or ways of doing PHP programming here, but I just don't know the terms for them yet. I know this isn't a straight forward question, I just need some help in organizing my thoughts.

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• about getadrrinfo() C++?

  - by Isavel

  I'm reading this book called beej's guide to network programming and there's a part in the book were it provide a sample code which illustrate the use of getaddrinfo(); the book state that the code below "will print the IP addresses for whatever host you specify on the command line" - beej's guide to network programming. now I'm curious and want to try it out and run the code, but I guess the code was develop in UNIX environment and I'm using visual studio 2012 windows 7 OS, and most of the headers was not supported so I did a bit of research and find out that I need to include the winsock.h and ws2_32.lib for windows, for it to get working, fortunately everything compiled no errors, but when I run it using the debugger and put in 'www.google.com' as command argument I was disappointed that it did not print any ipaddress, the output that I got from the console is "getaddrinfo: E" what does the letter E mean? Do I need to configure something out of the debugger? Interestingly I left the command argument blank and the output changed to "usage: showip hostname" Any help would be appreciated. #ifdef _WIN32 #endif #include <sys/types.h> #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> using namespace std; #include <stdio.h> #include <string.h> #include <sys/types.h> #include <winsock.h> #pragma comment(lib, "ws2_32.lib") int main(int argc, char *argv[]) { struct addrinfo hints, *res, *p; int status; char ipstr[INET6_ADDRSTRLEN]; if (argc != 2) { fprintf(stderr,"usage: showip hostname\n"); system("PAUSE"); return 1; } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version hints.ai_socktype = SOCK_STREAM; if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); system("PAUSE"); return 2; } printf("IP addresses for %s:\n\n", argv[1]); for(p = res;p != NULL; p = p->ai_next) { void *addr; char *ipver; // get the pointer to the address itself, // different fields in IPv4 and IPv6: if (p->ai_family == AF_INET) { // IPv4 struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr; addr = &(ipv4->sin_addr); ipver = "IPv4"; } else { // IPv6 struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr; addr = &(ipv6->sin6_addr); ipver = "IPv6"; } // convert the IP to a string and print it: inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr); printf(" %s: %s\n", ipver, ipstr); } freeaddrinfo(res); // free the linked list system("PAUSE"); return 0; }

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• New MySQL Cluster 7.3 Previews: Foreign Keys, NoSQL Node.js API and Auto-Tuned Clusters

  - by Mat Keep

  At this weeks MySQL Connect conference, Oracle previewed an exciting new wave of developments for MySQL Cluster, further extending its simplicity and flexibility by expanding the range of use-cases, adding new NoSQL options, and automating configuration. What’s new: Development Release 1: MySQL Cluster 7.3 with Foreign Keys Early Access “Labs” Preview: MySQL Cluster NoSQL API for Node.js Early Access “Labs” Preview: MySQL Cluster GUI-Based Auto-Installer In this blog, I'll introduce you to the features being previewed. Review the blogs listed below for more detail on each of the specific features discussed. Save the date!: A live webinar is scheduled for Thursday 25th October at 0900 Pacific Time / 1600UTC where we will discuss each of these enhancements in more detail. Registration will be open soon and published to the MySQL webinars page MySQL Cluster 7.3: Development Release 1 The first MySQL Cluster 7.3 Development Milestone Release (DMR) previews Foreign Keys, bringing powerful new functionality to MySQL Cluster while eliminating development complexity. Foreign Key support has been one of the most requested enhancements to MySQL Cluster – enabling users to simplify their data models and application logic – while extending the range of use-cases for both custom projects requiring referential integrity and packaged applications, such as eCommerce, CRM, CMS, etc. Implementation The Foreign Key functionality is implemented directly within the MySQL Cluster data nodes, allowing any client API accessing the cluster to benefit from them – whether they are SQL or one of the NoSQL interfaces (Memcached, C++, Java, JPA, HTTP/REST or the new Node.js API - discussed later.) The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL In addition, the MySQL Cluster implementation supports the online adding and dropping of Foreign Keys, ensuring the Cluster continues to serve both read and write requests during the operation.  This represents a further enhancement to MySQL Cluster's support for on0line schema changes, ie adding and dropping indexes, adding columns, etc.  Read this blog for a demonstration of using Foreign Keys with MySQL Cluster.  Getting Started with MySQL Cluster 7.3 DMR1: Users can download either the source or binary and evaluate the MySQL Cluster 7.3 DMR with Foreign Keys now! (Select the Development Release tab). MySQL Cluster NoSQL API for Node.js Node.js is hot! In a little over 3 years, it has become one of the most popular environments for developing next generation web, cloud, mobile and social applications. Bringing JavaScript from the browser to the server, the design goal of Node.js is to build new real-time applications supporting millions of client connections, serviced by a single CPU core. Making it simple to further extend the flexibility and power of Node.js to the database layer, we are previewing the Node.js Javascript API for MySQL Cluster as an Early Access release, available for download now from http://labs.mysql.com/. Select the following build: MySQL-Cluster-NoSQL-Connector-for-Node-js Alternatively, you can clone the project at the MySQL GitHub page.  Implemented as a module for the V8 engine, the new API provides Node.js with a native, asynchronous JavaScript interface that can be used to both query and receive results sets directly from MySQL Cluster, without transformations to SQL. Figure 1: MySQL Cluster NoSQL API for Node.js enables end-to-end JavaScript development Rather than just presenting a simple interface to the database, the Node.js module integrates the MySQL Cluster native API library directly within the web application itself, enabling developers to seamlessly couple their high performance, distributed applications with a high performance, distributed, persistence layer delivering 99.999% availability. The new Node.js API joins a rich array of NoSQL interfaces available for MySQL Cluster. Whichever API is chosen for an application, SQL and NoSQL can be used concurrently across the same data set, providing the ultimate in developer flexibility.  Get started with MySQL Cluster NoSQL API for Node.js tutorial MySQL Cluster GUI-Based Auto-Installer Compatible with both MySQL Cluster 7.2 and 7.3, the Auto-Installer makes it simple for DevOps teams to quickly configure and provision highly optimized MySQL Cluster deployments – whether on-premise or in the cloud. Implemented with a standard HTML GUI and Python-based web server back-end, the Auto-Installer intelligently configures MySQL Cluster based on application requirements and auto-discovered hardware resources Figure 2: Automated Tuning and Configuration of MySQL Cluster Developed by the same engineering team responsible for the MySQL Cluster database, the installer provides standardized configurations that make it simple, quick and easy to build stable and high performance clustered environments. The auto-installer is previewed as an Early Access release, available for download now from http://labs.mysql.com/, by selecting the MySQL-Cluster-Auto-Installer build. You can read more about getting started with the MySQL Cluster auto-installer here. Watch the YouTube video for a demonstration of using the MySQL Cluster auto-installer Getting Started with MySQL Cluster If you are new to MySQL Cluster, the Getting Started guide will walk you through installing an evaluation cluster on a singe host (these guides reflect MySQL Cluster 7.2, but apply equally well to 7.3 and the Early Access previews). Or use the new MySQL Cluster Auto-Installer! Download the Guide to Scaling Web Databases with MySQL Cluster (to learn more about its architecture, design and ideal use-cases). Post any questions to the MySQL Cluster forum where our Engineering team and the MySQL Cluster community will attempt to assist you. Post any bugs you find to the MySQL bug tracking system (select MySQL Cluster from the Category drop-down menu) And if you have any feedback, please post them to the Comments section here or in the blogs referenced in this article. Summary MySQL Cluster 7.2 is the GA, production-ready release of MySQL Cluster. The first Development Release of MySQL Cluster 7.3 and the Early Access previews give you the opportunity to preview and evaluate future developments in the MySQL Cluster database, and we are very excited to be able to share that with you. Let us know how you get along with MySQL Cluster 7.3, and other features that you want to see in future releases, by using the comments of this blog.

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• Goodby jQuery Templates, Hello JsRender

  - by SGWellens

  A funny thing happened on my way to the jQuery website, I blinked and a feature was dropped: jQuery Templates have been discontinued. The new pretender to the throne is JsRender. jQuery Templates looked pretty useful when they first came out. Several articles were written about them but I stayed away because being on the bleeding edge of technology is not a productive place to be. I wanted to wait until it stabilized…in retrospect, it was a serendipitous decision. This time however, I threw all caution to the wind and took a close look at JSRender. Why? Maybe I'm having a midlife crisis; I'll go motorcycle shopping tomorrow. Caveat, here is a message from the site: Warning: JsRender is not yet Beta, and there may be frequent changes to APIs and features in the coming period. Fair enough, we've been warned. The first thing we need is some data to render. Below is some JSON formatted data. Typically this will come from an asynchronous call to a web service. For simplicity, I hard coded a variable:     var Golfers = [         { ID: "1", "Name": "Bobby Jones", "Birthday": "1902-03-17" },         { ID: "2", "Name": "Sam Snead", "Birthday": "1912-05-27" },         { ID: "3", "Name": "Tiger Woods", "Birthday": "1975-12-30" }         ]; We also need some templates, I created two. Note: The script blocks have the id property set. They are needed so JsRender can locate them.     <script id="GolferTemplate1" type="text/html">         {{=ID}}: <b>{{=Name}}</b> <i>{{=Birthday}}</i> <br />     </script>       <script id="GolferTemplate2" type="text/html">         <tr>             <td>{{=ID}}</td>             <td><b>{{=Name}}</b></td>             <td><i>{{=Birthday}}</i> </td>         </tr>     </script> Including the correct JavaScript files is trivial:     <script src="Scripts/jquery-1.7.js" type="text/javascript"></script>     <script src="Scripts/jsrender.js" type="text/javascript"></script> Of course we need some place to render the output:     <div id="GolferDiv"></div><br />     <table id="GolferTable"></table> The code is also trivial:     function Test()     {         $("#GolferDiv").html($("#GolferTemplate1").render(Golfers));         $("#GolferTable").html($("#GolferTemplate2").render(Golfers));           // you can inspect the rendered html if there are poblems.         // var html = $("#GolferTemplate2").render(Golfers);     } And here's what it looks like with some random CSS formatting that I had laying around.    Not bad, I hope JsRender lasts longer than jQuery Templates. One final warning, a lot of jQuery code is ugly, butt-ugly. If you do look inside the jQuery files, you may want to cover your keyboard with some plastic in case you get vertigo and blow chunks. I hope someone finds this useful. Steve Wellens CodeProject

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• CQRS - Benefits

  - by Dylan Smith

  Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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• MySQL Connect Only 10 Days Away - Focus on InnoDB Sessions

  - by Bertrand Matthelié

  Time flies and MySQL Connect is only 10 days away! You can check out the full program here as well as in the September edition of the MySQL newsletter. Mat recently blogged about the MySQL Cluster sessions you’ll have the opportunity to attend, and below are those focused on InnoDB. Remember you can plan your schedule with Schedule Builder. Saturday, 1.00 pm, Room Golden Gate 3: 10 Things You Should Know About InnoDB—Calvin Sun, Oracle InnoDB is the default storage engine for Oracle’s MySQL as of MySQL Release 5.5. It provides the standard ACID-compliant transactions, row-level locking, multiversion concurrency control, and referential integrity. InnoDB also implements several innovative technologies to improve its performance and reliability. This presentation gives a brief history of InnoDB; its main features; and some recent enhancements for better performance, scalability, and availability. Saturday, 5.30 pm, Room Golden Gate 4: Demystified MySQL/InnoDB Performance Tuning—Dimitri Kravtchuk, Oracle This session covers performance tuning with MySQL and the InnoDB storage engine for MySQL and explains the main improvements made in MySQL Release 5.5 and Release 5.6. Which setting for which workload? Which value will be better for my system? How can I avoid potential bottlenecks from the beginning? Do I need a purge thread? Is it true that InnoDB doesn't need thread concurrency anymore? These and many other questions are asked by DBAs and developers. Things are changing quickly and constantly, and there is no “silver bullet.” But understanding the configuration setting’s impact is already a huge step in performance improvement. Bring your ideas and problems to share them with others—the discussion is open, just moderated by a speaker. Sunday, 10.15 am, Room Golden Gate 4: Better Availability with InnoDB Online Operations—Calvin Sun, Oracle Many top Web properties rely on Oracle’s MySQL as a critical piece of infrastructure for serving millions of users. Database availability has become increasingly important. One way to enhance availability is to give users full access to the database during data definition language (DDL) operations. The online DDL operations in recent MySQL releases offer users the flexibility to perform schema changes while having full access to the database—that is, with minimal delay of operations on a table and without rebuilding the entire table. These enhancements provide better responsiveness and availability in busy production environments. This session covers these improvements in the InnoDB storage engine for MySQL for online DDL operations such as add index, drop foreign key, and rename column. Sunday, 11.45 am, Room Golden Gate 7: Developing High-Throughput Services with NoSQL APIs to InnoDB and MySQL Cluster—Andrew Morgan and John Duncan, Oracle Ever-increasing performance demands of Web-based services have generated significant interest in providing NoSQL access methods to MySQL (MySQL Cluster and the InnoDB storage engine of MySQL), enabling users to maintain all the advantages of their existing relational databases while providing blazing-fast performance for simple queries. Get the best of both worlds: persistence; consistency; rich SQL queries; high availability; scalability; and simple, flexible APIs and schemas for agile development. This session describes the memcached connectors and examines some use cases for how MySQL and memcached fit together in application architectures. It does the same for the newest MySQL Cluster native connector, an easy-to-use, fully asynchronous connector for Node.js. Sunday, 1.15 pm, Room Golden Gate 4: InnoDB Performance Tuning—Inaam Rana, Oracle The InnoDB storage engine has always been highly efficient and includes many unique architectural elements to ensure high performance and scalability. In MySQL 5.5 and MySQL 5.6, InnoDB includes many new features that take better advantage of recent advances in operating systems and hardware platforms than previous releases did. This session describes unique InnoDB architectural elements for performance, new features, and how to tune InnoDB to achieve better performance. Sunday, 4.15 pm, Room Golden Gate 3: InnoDB Compression for OLTP—Nizameddin Ordulu, Facebook and Inaam Rana, Oracle Data compression is an important capability of the InnoDB storage engine for Oracle’s MySQL. Compressed tables reduce the size of the database on disk, resulting in fewer reads and writes and better throughput by reducing the I/O workload. Facebook pushes the limit of InnoDB compression and has made several enhancements to InnoDB, making this technology ready for online transaction processing (OLTP). In this session, you will learn the fundamentals of InnoDB compression. You will also learn the enhancements the Facebook team has made to improve InnoDB compression, such as reducing compression failures, not logging compressed page images, and allowing changes of compression level. Not registered yet? You can still save US$ 300 over the on-site fee – Register Now!

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• Timeout Considerations for Solicit Response – Part 2

  - by Michael Stephenson

  To follow up a previous article about timeouts and how they can affect your application I have extended the sample we were using to include WCF. I will execute some test scenarios and discuss the results. The sample We begin by consuming exactly the same web service which is sitting on a remote server. This time I have created a .net 3.5 application which will consume the web service using the basichttp binding. To show you the configuration for the consumption of this web service please refer to the below diagram. You can see like before we also have the connectionManagement element in the configuration file. I have added a WCF service reference (also using the asynchronous proxy methods) and have the below code sample in the application which will asynchronously make the web service calls and handle the responses on a call back method invoked by a delegate. If you have read the previous article you will notice that the code is almost the same.   Sample 1 – WCF with Default Timeouts In this test I set about recreating the same scenario as previous where we would run the test but this time using WCF as the messaging component. For the first test I would use the default configuration settings which WCF had setup when we added a reference to the web service. The timeout values for this test are: closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"   The Test We simulated 21 calls to the web service Test Results The client-side trace is as follows:   The server-side trace is as follows: Some observations on the results are as follows: The timeouts happened quicker than in the previous tests because some calls were timing out before they attempted to connect to the server The first few calls that timed out did actually connect to the server and did execute successfully on the server   Test 2 – Increase Open Connection Timeout & Send Timeout In this test I wanted to increase both the send and open timeout values to try and give everything a chance to go through. The timeout values for this test are: closeTimeout="00:01:00" openTimeout="00:10:00" receiveTimeout="00:10:00" sendTimeout="00:10:00"   The Test We simulated 21 calls to the web service   Test Results The client side trace for this test was   The server-side trace for this test was: Some observations on this test are: This test proved if the timeouts are high enough everything will just go through   Test 3 – Increase just the Send Timeout In this test we wanted to increase just the send timeout. The timeout values for this test are: closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:10:00"   The Test We simulated 21 calls to the web service   Test Results The below is the client side trace The below is the server side trace Some observations on this test are: In this test from both the client and server perspective everything ran through fine The open connection timeout did not seem to have any effect   Test 4 – Increase Just the Open Connection Timeout In this test I wanted to validate the change to the open connection setting by increasing just this on its own. The timeout values for this test are: closeTimeout="00:01:00" openTimeout="00:10:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"   The Test We simulated 21 calls to the web service Test Results The client side trace was The server side trace was Some observations on this test are: In this test you can see that the open connection which relates to opening the channel timeout increase was not the thing which stopped the calls timing out It's the send of data which is timing out On the server you can see that the successful few calls were fine but there were also a few calls which hit the server but timed out on the client You can see that not all calls hit the server which was one of the problems with the WSE and ASMX options   Test 5 – Smaller Increase in Send Timeout In this test I wanted to make a smaller increase to the send timeout than previous just to prove that it was the key setting which was controlling what was timing out. The timeout values for this test are: openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:02:30"   The Test We simulated 21 calls to the web service Test Results The client side trace was   The server side trace was Some observations on this test are: You can see that most of the calls got through fine On the client you can see that call 20 timed out but still hit the server and executed fine.   Summary At this point between the two articles we have quite a lot of scenarios showing the different way the timeout setting have played into our original performance issue, and now we can see how WCF could offer an improved way to handle the problem. To summarise the differences in the timeout properties for the three technology stacks: ASMX The timeout value only applies to the execution time of your request on the server. The timeout does not consider how long your code might be waiting client side to get a connection. WSE The timeout value includes both the time to obtain a connection and also the time to execute the request. A timeout will not be thrown as an error until an attempt to connect to the server is made. This means a 40 second timeout setting may not throw the error until 60 seconds when the connection to the server is made. If the connection to the server is made you should be aware that your message will be processed and you should design for this. WCF The WCF send timeout is the setting most equivalent to the settings we were looking at previously. Like WSE this setting the counter includes the time to get a connection as well as the time to execute on a server. Unlike WSE and ASMX an error will be thrown as soon as the send timeout from making your call from user code has elapsed regardless of whether we are waiting for a connection or have an open connection to the server. This may to a user appear to have better latency in getting an error response compared to WSE or ASMX.

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• The illusion of Competence

  - by tony_lombardo

  Working as a contractor opened my eyes to the developer food chain.  Even though I had similar experiences earlier in my career, the challenges seemed much more vivid this time through.  I thought I’d share a couple of experiences with you, and the lessons that can be taken from them. Lesson 1: Beware of the “funnel” guy.  The funnel guy is the one who wants you to funnel all thoughts, ideas and code changes through him.  He may say it’s because he wants to avoid conflicts in source control, but the real reason is likely that he wants to hide your contributions.  Here’s an example.  When I finally got access to the code on one of my projects, I was told by the developer that I had to funnel all of my changes through him.  There were 4 of us coding on the project, but only 2 of us working on the UI.  The other 2 were working on a separate application, but part of the overall project.  So I figured, I’ll check it into SVN, he reviews and accepts then merges in.  Not even close.  I didn’t even have checkin rights to SVN, I had to email my changes to the developer so he could check those changes in.  Lesson 2: If you point out flaws in code to someone supposedly ‘higher’ than you in the developer chain, they’re going to get defensive.  My first task on this project was to review the code, familiarize myself with it.  So of course, that’s what I did.  And in familiarizing myself with it, I saw so many bad practices and code smells that I immediately started coming up with solutions to fix it.  Of course, when I reviewed these changes with the developer (guy who originally wrote the code), he smiled and nodded and said, we can’t make those changes now, it’s too destabilizing.  I recommended we create a new branch and start working on refactoring, but branching was a new concept for this guy and he was worried we would somehow break SVN. How about some concrete examples? I started out by recommending we remove NUnit dependency and tests from the application project, and create a separate Unit testing project.  This was met with a little bit of resistance because - “How do I access the private methods?”  As it turned out there weren’t really any private methods that weren’t exposed by public methods, so I quickly calmed this fear. Win 1 Loss 0 Next, I recommended that all of the File IO access be wrapped in Using clauses, or at least properly wrapped in try catch finally.  This recommendation was accepted.. but never implemented. Win 2  Loss 1 Next recommendation was to refactor the command pattern implementation.  The command pattern was implemented, but it wasn’t really necessary for the application.  More over, the fact that we had 100 different command classes, each with it’s own specific command parameters class, made maintenance a huge hassle.  The same code repeated over and over and over.  This recommendation was declined, the code was too fragile and this change would destabilize it.  I couldn’t disagree, though it was the commands themselves in many cases that were fragile. Win 2 Loss 2 Next recommendation was to aid performance (and responsiveness) of the application by using asynchronous service calls.  This on was accepted. Win 2 Loss 3 If you’re paying any attention, you’re wondering why the async service calls was scored as a loss.. Let me explain.  The service call was made using the async pattern.  Followed by a thread.sleep  <facepalm>. Now it’s easy to be harsh on this kind of code, especially if you’re an experienced developer.  But I understood how most of this happened.  One junior guy, working as hard as he can to build his first real world application, with little or no guidance from anyone else.  He had his pattern book and theory of programming to help him, but no real world experience.  He didn’t know how difficult it would be to trace the crashes to the coding issues above, but he will one day.  The part that amazed me was the management position that “this guy should be a team lead, because he’s worked so hard”.  I’m all for rewarding hard work, but when you reward someone by promoting them past the point of their competence, you’re setting yourself and them up for failure.  And that’s lesson 3.  Just because you’ve got a hard worker, doesn’t mean he should be leading a development project.  If you’re a junior guy busting your ass, keep at it.  I encourage you to try new things, but most importantly to learn from your mistakes.  And correct your mistakes.  And if someone else looks at your code and shows you a laundry list of things that should be done differently, don’t take it personally – they’re really trying to help you.  And if you’re a senior guy, working with a junior guy, it’s your duty to point out the flaws in the code.  Even if it does make you the bad guy.  And while I’ve used “guy” above, I mean both men and women.  And in some cases mutant dinosaurs. 

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• Thread.Interrupt Is Evil

  - by Alois Kraus

  Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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