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  • Ruby on Rails is complaining about a method that doesn't exist that is built into Active Record. Wha

    - by grg-n-sox
    This will probably just be a simple problem and I am just blind or an idiot but I could use some help. So I am going over some basic guides in Rails, reviewing the basics and such for an upcoming exam. One of the guides included was the sort-of-standard getting started guide over at guide.rubyonrails.org. Here is the link if you need it. Also all my code is for my app is from there, so I have no problem releasing any of my code since it should be the same as shown there. I didn't do a copy paste, but I basically was typing with Vim in one half of my screen and the web page in the other half, typing what I see. http://guides.rubyonrails.org/getting_started.html So like I said, I am going along the guide when I noticed past a certain point in the tutorial, I was always getting an error on the site. To find the section of code, just hit Ctrl+f on the page (or whatever you have search/find set to) and enter "accepts_". This should immediately direct you to this chunk of code. class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end So I tried putting this in my code. It is in ~/Rails/blog/app/models/post.rb in case you are wondering. However, even after all the other code I put in past that in the guide, hoping I was just missing some line of code that would come up later in the guide. But nothing, same error every time. This is what I get. NoMethodError in PostsController#index undefined method `accepts_nested_attributes_for' for #<Class:0xb7109f98> /usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/base.rb:1833:in `method_missing' app/models/post.rb:7 app/controllers/posts_controller.rb:9:in `index' Request Parameters: None Response Headers: {"Content-Type"=>"", "cookie"=>[], "Cache-Control"=>"no-cache"} Now, I copied the above code from the guide. The two code sections I edited mentioned in the error message I will paste as is below. class PostsController < ApplicationController # GET /posts # GET /posts.xml before_filter :find_post, :only => [:show, :edit, :update, :destroy] def index @posts = Post.find(:all) # <= the line 9 referred to in error message respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } end end class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , # <= problem :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end Also here is gem local gem list. I do note that they are a bit out of date, but the default Rails install any of the school machines (an environment likely for my exam) is basically 'gem install rails --version 2.2.2' and since they are windows machines, they come with all the normal windows ruby gems that comes with the ruby installer. However, I am running this off a Debian virtual machine of mine, but trying to set it up similarly and I figured the windows ruby gems wouldn't change anything in Rails. *** LOCAL GEMS *** actionmailer (2.2.2) actionpack (2.2.2) activerecord (2.2.2) activeresource (2.2.2) activesupport (2.2.2) gem_plugin (0.2.3) hpricot (0.8.2) linecache (0.43) log4r (1.1.7) ptools (1.1.9) rack (1.1.0) rails (2.2.2) rake (0.8.7) sqlite3-ruby (1.2.3) So any ideas on what the problem is? Thanks in advanced.

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  • (static initialization order?!) problems with factory pattern

    - by smerlin
    Why does following code raise an exception (in createObjects call to map::at) alternativly the code (and its output) can be viewed here intererestingly the code works as expected if the commented lines are uncommented with both microsoft and gcc compiler (see here), this even works with initMap as ordinary static variable instead of static getter. The only reason for this i can think of is that the order of initialization of the static registerHelper_ object (factory_helper_)and the std::map object (initMap) are wrong, however i cant see how that could happen, because the map object is constructed on first usage and thats in factory_helper_ constructor, so everything should be alright shouldnt it ? I am even more suprised that those doNothing() lines fix the issue, because that call to doNothing() would happen after the critical section (which currently fails) is passed anyway. EDIT: debugging showed, that without the call to factory_helper_.doNothing(), the constructor of factory_helper_ is never called. #include <iostream> #include <string> #include <map> #define FACTORY_CLASS(classtype) \ extern const char classtype##_name_[] = #classtype; \ class classtype : FactoryBase<classtype,classtype##_name_> namespace detail_ { class registerHelperBase { public: registerHelperBase(){} protected: static std::map<std::string, void * (*)(void)>& getInitMap() { static std::map<std::string, void * (*)(void)>* initMap = 0; if(!initMap) initMap= new std::map<std::string, void * (*)(void)>(); return *initMap; } }; template<class TParent, const char* ClassName> class registerHelper_ : registerHelperBase { static registerHelper_ help_; public: //void doNothing(){} registerHelper_(){ getInitMap()[std::string(ClassName)]=&TParent::factory_init_; } }; template<class TParent, const char* ClassName> registerHelper_<TParent,ClassName> registerHelper_<TParent,ClassName>::help_; } class Factory : detail_::registerHelperBase { private: Factory(); public: static void* createObject(const std::string& objclassname) { return getInitMap().at(objclassname)(); } }; template <class TClass, const char* ClassName> class FactoryBase { private: static detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName> factory_helper_; static void* factory_init_(){ return new TClass();} public: friend class detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName>; FactoryBase(){ //factory_helper_.doNothing(); } virtual ~FactoryBase(){}; }; template <class TClass, const char* ClassName> detail_::registerHelper_<FactoryBase<TClass,ClassName>,ClassName> FactoryBase<TClass,ClassName>::factory_helper_; FACTORY_CLASS(Test) { public: Test(){} }; int main(int argc, char** argv) { try { Test* test = (Test*) Factory::createObject("Test"); } catch(const std::exception& ex) { std::cerr << "caught std::exception: "<< ex.what() << std::endl; } #ifdef _MSC_VER system("pause"); #endif return 0; }

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  • Why are there so many man-made edge cases in IT, and is there any hope for simplification / unificat

    - by Hamish Grubijan
    This question is meant to generate discussion and so it is marked as community wiki. My observation is that the field of information technology grows so rapidly and randomly, that for many it takes a lot of time to learn many intricacies of some tools that will be obsolete in just short 3 years. If you look at the questions asked on StackOverflow ... at least half of them stem from the fact that some language / tool / API / protocol was poorly designed, is backwards and has gotchas. There are so many things which distract developers from converting English into machine code; instead they spend their time configuring stuff and gluing together things that do not really fit. How many times do you pick up somebody else's project (or someone picks up yours :) ) and realize that this program does not need half of the dialogs that it has, and that the logic can be simplified a great deal? But, it had to be made and sold here before a better thing is made and sold elsewhere, and hence all this rush. I often wish that things would just slow down. I do not want Microsoft Windows to run on my car's computer, my watch, my table, my toaster oven, and my toilet seat. I'd rather have Windows that DOES NOT HAVE WINDOWS REGISTRY, I'd rather have Windows that allows two different programs to work on the same file at the same time, the way it works on Unix systems. Microsoft is just an example. I am looking forward to the day when I do not have to worry about Windows vs Unix new line break, when System32 actually means that this directory contains 32-bit binaries, and not 64-bit ones, the day when dll hell and manifest hell are no longer an issue, the day when it takes me a lot less than 3 months on a new job to learn the system. I do not mean learning the entire code base of a product (depending on the size of it, it can take a long time). I mean - remembering which build-assisting scripts are written in Perl and which version of it, and which ones are done through .bat files, when do I need to manually make every file in some directory writable before running a script, or else a critical step of a database maintenance home-grown tool will bomb, and it will take 2 days to clean that up. Makes me wonder if humans enslaved computers, or if it is the other way around. The key is that improving those things will not bring extra revenue, and hence those taking the time to fix crap like that are not "business focused". However, these imperfections irritate me immensely, particularly because my memory is limited - I can hold only a small portion of that useless knowledge of a system in my head at any given point in time. I must not be alone. Did you also happen to notice that a programmer can waste a lot of time on things that should have been a lot more straight-forward? Is there hope? Will things get better/simpler in the future, or will there be a lot more IT crap floating around? I suppose I see diversity of tools, protocols, etc. as a bad thing. Thank you for participation.

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  • Beginner questions on Java Regular Expression

    - by Robert
    Hello everyone. I began studying Java Regular Expression recently and I found some really intersting task.For example,I now need to dig out "Product Name","Product Description" and "Sellers for this product" out of the following HTML code.(I am sorry for the big chunck of code,but it is very straightforward) <td class="sr-check"> <input type="checkbox" name="cptitle" value="678560038" /></td> <td class="sr-image" style="width: 80px;"><a href="/Nikon-D300S-12-3-678560038/prices-html" class="strictRule" rel="nofollow"><img src="http://img01.static-nextag.com/image/Nikon-D300S-12-3-MP-Digital-SLR-Camera-Body-Black/0/000/006/789/461/678946110.jpg" alt="Nikon D300S 12.3 MP Digital SLR Camera Body - Black" class="imageLink strictRule" height="75" width="75" id="opILink_0" title="Nikon Digital Cameras - Nikon D300S 12.3 MP Digital SLR Camera Body - Black" /></a><div class="breaker">&nbsp;</div></td> <td class="sr-info"> <div class="sr-info"> <a id="opPNLink_0" class="underline" style="font-size:16px" href="/Nikon-D300S-12-3-678560038 /prices-html" >Nikon D300S 12.3 MP <b>Digital</b> SLR <b>Camera</b> Body - Black</a> <div class="sr-subinfo"> <div class="sr-info-description">SLR - 13.1MP, 12.3MP - 1x Optical Zoom - CompactFlash, SD/MMC Memory Card - 3in.</div> <div class="rating"> <img src="http://img01.static-nextag.com/imagefiles/stars/stars4_10px.gif" alt="4/5 stars" title="4/5 stars" /> (92 user ratings)</div> <div style="clear: both;"> <!-- nxtginc=nextag.api.ServerInclude$JSPIncludeWriter(/buyer/ATLSSI.jsp?ptid=678560038&dts=y) --> <a id="_atl_0" style="" href="http://www.nextag.com/serv/main/buyer/MyPDir.jsp?list=_transCookieList&amp;cmd=add&amp;ptitle=678560038" rel="nofollow">+ Add to Shopping List</a> &nbsp;|&nbsp; <!-- endnxtginc --> <a rel="nofollow" id="mltLink_0" class="mlt-link" href="/Digital-Cameras--zz500001z2z678560038zB2dgz5---html">See More Like This</a> </div> <div id="fsLink_0" class="featuredSeller"> <a rel="nofollow" class="featuredSeller" id="opFSLink_0_0" href="/norob/PtitleSeller.jsp?chnl=main&amp;tag=785646073amp;ctx=x%2BN%2Fs9zy56l4u8RXCzALE1jeLesDMzeK09rPQEdK3Yjx395ZzX9cMh9N5JAxjk7xPqF9hjk2ztM5IRXU5nspLubIXYaVzI%2B%2Fg7h1Qz58TzgvrWuNawV8qEIqqSmClArWMq6mpzNRuSlgg2xCXYObNnaIH00iKSUmBawDRvecwbCpAxhXgXoLEiEinTwr3EipComdzxL9UHFYTLoWUToUB5SRSsolQmEJ3mgnnvu83%2FC8W34TGpN9mJo%2BnyAeTkt4&amp;ptitle=678560038" target="_blank" >Thundercameras</a>:$1,289 &nbsp; <a rel="nofollow" class="featuredSeller" id="opFSLink_0_1" href="/norob/PtitleSeller.jsp?chnl=main&amp;tag=797076595&amp;ctx=x%2BN%2Fs9zy56l4u8RXCzALE1jeLesDMzeK09rPQEdK3Yjx395ZzX9cMh9N5JAxjk7xPqF9hjk2ztM5IRXU5nspLubIXYaVzI%2B%2Fg7h1Qz58TzgvrWuNawV8qEIqqSmClArWMq6mpzNRuSlgg2xCXYObNrcWLhL%2BhryuAGhXNhYSPE%2BpAxhXgXoLEiEinTwr3EipComdzxL9UHFYTLoWUToUB5SRSsolQmEJ3mgnnvu83%2FC8W34TGpN9mJo%2BnyAeTkt4&amp;ptitle=678560038" target="_blank" >PhotoVideoSuperStore</a>:$1,269 &nbsp; <a rel="nofollow" class="featuredSeller" id="opFSLink_0_2" href="/norob/PtitleSeller.jsp?chnl=main&amp;tag=803555293&amp;ctx=x%2BN%2Fs9zy56l4u8RXCzALE1jeLesDMzeK09rPQEdK3Yjx395ZzX9cMh9N5JAxjk7xPqF9hjk2ztM5IRXU5nspLubIXYaVzI%2B%2Fg7h1Qz58TzgvrWuNawV8qEIqqSmClArWMq6mpzNRuSlgg2xCXYObNt06qcvLJ5UQz7S3zKd4urWpAxhXgXoLEiEinTwr3EipComdzxL9UHFYTLoWUToUB5SRSsolQmEJ3mgnnvu83%2FC8W34TGpN9mJo%2BnyAeTkt4&amp;ptitle=678560038" target="_blank" >Digitalelect</a>:$1,279 &nbsp;</div> I would think of : (1) digging out the product name from <td class="sr-image >tag,and using regular expression exp ="<td><span\\s+class=\"sr-image\"[^>]*>" + ".*?</span><a href=\"" + "([^\"]+)" + "\"[^>]*>" + "([^<]+)" + "</a>.*?</td>"; (2) digging out the product info from the <div class="sr-info-description"> tag. exp = "<div class="sr-info-description"> [^>]*>" (3) digging out the Sellers' names from <div id="fsLink_0" class="featuredSeller"> tag. exp = "<div id="fslink_0" class="featuredSeller[^>]*>" + ".*?</span><a rel=\"" + "([^\"]+)" + "\"[^>]*>" + "([^<]+)" + "</a>.*?</td>"; I am just beginning learing using Java Regular Expression,I would be grateful if you could correct me if I am in the wrong track or my regular expressiona are wrong. Thanks a lot,guys.

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  • XNA: Best way to load and read a XML file?

    - by Rosarch
    I'm having difficulty doing this seemingly simple task. I want to load XML files with the same ease of loading art assets: content = new ContentManager(Services); content.RootDirectory = "Content"; Texture2d background = content.Load<Texture2D>("images\\ice"); I'm not sure how to do this. This tutorial seems helpful, but how do I get a StorageDevice instance? I do have something working now, but it feels pretty hacky: public IDictionary<string, string> Get(string typeName) { IDictionary<String, String> result = new Dictionary<String, String>(); xmlReader.Read(); // get past the XML declaration string element = null; string text = null; while (xmlReader.Read()) { switch (xmlReader.NodeType) { case XmlNodeType.Element: element = xmlReader.Name; break; case XmlNodeType.Text: text = xmlReader.Value; break; } if (text != null && element != null) { result[element] = text; text = null; element = null; } } return result; } I apply this to the following XML file: <?xml version="1.0" encoding="utf-8" ?> <zombies> <zombie> <health>100</health> <positionX>23</positionX> <positionY>12</positionY> <speed>2</speed> </zombie> </zombies> And it is able to pass this unit test: internal virtual IPersistentState CreateIPersistentState(string fullpath) { IPersistentState target = new ReadWriteXML(File.Open(fullpath, FileMode.Open)); return target; } /// <summary> ///A test for Get with one zombie. ///</summary> //[TestMethod()] public void SimpleGetTest() { string fullPath = "C:\\pathTo\\Data\\SavedZombies.xml"; IPersistentState target = CreateIPersistentState(fullPath); string typeName = "zombie"; IDictionary<string, string> expected = new Dictionary<string, string>(); expected["health"] = "100"; expected["positionX"] = "23"; expected["positionY"] = "12"; expected["speed"] = "2"; IDictionary<string, string> actual = target.Get(typeName); foreach (KeyValuePair<string, string> entry in expected) { Assert.AreEqual(entry.Value, expected[entry.Key]); } } Downsides to the current approach: file loading is done poorly, and matching keys to values seems like it's way more effort than necessary. Also, I suspect this approach would fall apart with more than one entry in the XML. I can't imagine that this is the optimal implementation.

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  • g++ symbol versioning. Set it to GCC_3.0 using version 4 of g++

    - by Ismael
    Hi all I need to implemente a Java class which uses JNI to control a fiscal printer in XUbuntu 8.10 with sun-java6-jdk installed. The structure is the following: EpsonDriver.java loads libEpson.so libEpson is linked dynamically with EpsonFiscalProtocol.so ( provided by Epson, no source available ) and pthread I use javah to generate the header file, and the code compiles. Then I put the libEpson.so in $JAVA_HOME/jre/lib/i386, and EpsonDriver.java uses an static initializar System.loadLibrary("libEpson") That part works, however, when I try to use any of the methods I get an unsatisfiedLinkError exception. Some time ago, a coworker did a version that works, and using objdump -Dslx I got the following: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x0000ccc4 memsz 0x0000ccc4 flags r-x LOAD off 0x0000d000 vaddr 0x0000d000 paddr 0x0000d000 align 2**12 filesz 0x00000250 memsz 0x00044a5c flags rw- DYNAMIC off 0x0000d014 vaddr 0x0000d014 paddr 0x0000d014 align 2**2 filesz 0x000000f0 memsz 0x000000f0 flags rw- NOTE off 0x000000d4 vaddr 0x000000d4 paddr 0x000000d4 align 2**2 filesz 0x00000024 memsz 0x00000024 flags r-- STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rw- Dynamic Section: NEEDED EpsonFiscalProtocol.so NEEDED libpthread.so.0 NEEDED libstdc++.so.6 NEEDED libm.so.6 NEEDED libc.so.6 SONAME libcom_tichile_jpos_EpsonSerialDriver.so INIT 0x00007254 FINI 0x0000ba08 GNU_HASH 0x000000f8 STRTAB 0x00001f50 SYMTAB 0x00000ae0 STRSZ 0x00002384 SYMENT 0x00000010 PLTGOT 0x0000d108 PLTRELSZ 0x00000008 PLTREL 0x00000011 JMPREL 0x0000724c REL 0x000045c4 RELSZ 0x00002c88 RELENT 0x00000008 TEXTREL 0x00000000 VERNEED 0x00004564 VERNEEDNUM 0x00000002 VERSYM 0x000042d4 RELCOUNT 0x000000ac Version References: required from libstdc++.so.6: 0x056bafd3 0x00 05 CXXABI_1.3 0x08922974 0x00 04 GLIBCXX_3.4 required from libc.so.6: 0x0b792650 0x00 03 GCC_3.0 0x0d696910 0x00 02 GLIBC_2.0 In the recently compiled file I get: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x00005300 memsz 0x00005300 flags r-x LOAD off 0x00005300 vaddr 0x00006300 paddr 0x00006300 align 2**12 filesz 0x00000274 memsz 0x00010314 flags rw- DYNAMIC off 0x00005314 vaddr 0x00006314 paddr 0x00006314 align 2**2 filesz 0x000000e0 memsz 0x000000e0 flags rw- EH_FRAME off 0x00004a00 vaddr 0x00004a00 paddr 0x00004a00 align 2**2 filesz 0x00000154 memsz 0x00000154 flags r-- Dynamic Section: NEEDED libstdc++.so.5 NEEDED libm.so.6 NEEDED libgcc_s.so.1 NEEDED libc.so.6 SONAME EpsonFiscalProtocol.so INIT 0x00001cb4 FINI 0x00004994 HASH 0x000000b4 STRTAB 0x00000da4 SYMTAB 0x000004f4 STRSZ 0x00000acf SYMENT 0x00000010 PLTGOT 0x0000640c PLTRELSZ 0x00000270 PLTREL 0x00000011 JMPREL 0x00001a44 REL 0x000019dc RELSZ 0x00000068 RELENT 0x00000008 VERNEED 0x0000198c VERNEEDNUM 0x00000002 VERSYM 0x00001874 RELCOUNT 0x00000004 Version References: required from libstdc++.so.5: 0x056bafd2 0x00 04 CXXABI_1.2 required from libc.so.6: 0x09691f73 0x00 03 GLIBC_2.1.3 0x0d696910 0x00 02 GLIBC_2.0 So I suspect the main diference is the GCC_3.0 symbol I compile libcom_tichile_EpsonSerialDriver.so with the following command ( from memory as I not at work right now ) g++ -Wl,-soname=.... -shared -I/*jni libraries*/ -o libcom_tichile_jpos_EpsonSerialDriver -lEpsonFiscalProtocol -lpthread Is there any way to tell g++ to use that symbol version? Or any idea in how to make it work? EDIT: I have another non-working version with the followin dump: Program Header: LOAD off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**12 filesz 0x0000bf68 memsz 0x0000bf68 flags r-x LOAD off 0x0000cc0c vaddr 0x0000cc0c paddr 0x0000cc0c align 2**12 filesz 0x000005e8 memsz 0x00044df0 flags rw- DYNAMIC off 0x0000cc20 vaddr 0x0000cc20 paddr 0x0000cc20 align 2**2 filesz 0x000000f8 memsz 0x000000f8 flags rw- EH_FRAME off 0x0000b310 vaddr 0x0000b310 paddr 0x0000b310 align 2**2 filesz 0x000002bc memsz 0x000002bc flags r-- STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rw- RELRO off 0x0000cc0c vaddr 0x0000cc0c paddr 0x0000cc0c align 2**0 filesz 0x000003f4 memsz 0x000003f4 flags r-- Dynamic Section: NEEDED EpsonFiscalProtocol.so NEEDED libpthread.so.0 NEEDED libstdc++.so.6 NEEDED libm.so.6 NEEDED libgcc_s.so.1 NEEDED libc.so.6 SONAME libcom_tichile_jpos_EpsonSerialDriver.so INIT 0x000055d8 FINI 0x0000a968 HASH 0x000000f4 GNU_HASH 0x00000a30 STRTAB 0x00002870 SYMTAB 0x00001410 STRSZ 0x00002339 SYMENT 0x00000010 PLTGOT 0x0000cff4 PLTRELSZ 0x00000168 PLTREL 0x00000011 JMPREL 0x00005470 REL 0x00004ea8 RELSZ 0x000005c8 RELENT 0x00000008 VERNEED 0x00004e38 VERNEEDNUM 0x00000002 VERSYM 0x00004baa RELCOUNT 0x00000001 Version References: required from libstdc++.so.6: 0x056bafd3 0x00 05 CXXABI_1.3 0x08922974 0x00 03 GLIBCXX_3.4 required from libc.so.6: 0x09691f73 0x00 06 GLIBC_2.1.3 0x0d696914 0x00 04 GLIBC_2.4 0x0d696910 0x00 02 GLIBC_2.0 Now I think the main difference is in the GCC_3.0 symbol/ABI EDIT: Luckily, a coworker found a way to talk to the printer using Java

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  • Parallel processing via multithreading in Java

    - by Robz
    There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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  • Help with infrequent segmentation fault in accessing boost::unordered_multimap or struct

    - by Sarah
    I'm having trouble debugging a segmentation fault. I'd appreciate tips on how to go about narrowing in on the problem. The error appears when an iterator tries to access an element of a struct Infection, defined as: struct Infection { public: explicit Infection( double it, double rt ) : infT( it ), recT( rt ) {} double infT; // infection start time double recT; // scheduled recovery time }; These structs are kept in a special structure, InfectionMap: typedef boost::unordered_multimap< int, Infection > InfectionMap; Every member of class Host has an InfectionMap carriage. Recovery times and associated host identifiers are kept in a priority queue. When a scheduled recovery event arises in the simulation for a particular strain s in a particular host, the program searches through carriage of that host to find the Infection whose recT matches the recovery time (double recoverTime). (For reasons that aren't worth going into, it's not as expedient for me to use recT as the key to InfectionMap; the strain s is more useful, and coinfections with the same strain are possible.) assert( carriage.size() > 0 ); pair<InfectionMap::iterator,InfectionMap::iterator> ret = carriage.equal_range( s ); InfectionMap::iterator it; for ( it = ret.first; it != ret.second; it++ ) { if ( ((*it).second).recT == recoverTime ) { // produces seg fault carriage.erase( it ); } } I get a "Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address..." on the line specified above. The recoverTime is fine, and the assert(...) in the code is not tripped. As I said, this seg fault appears 'randomly' after thousands of successful recovery events. How would you go about figuring out what's going on? I'd love ideas about what could be wrong and how I can further investigate the problem. Update I added a new assert and a check just inside the for loop: assert( carriage.size() > 0 ); assert( carriage.count( s ) > 0 ); pair<InfectionMap::iterator,InfectionMap::iterator> ret = carriage.equal_range( s ); InfectionMap::iterator it; cout << "carriage.count(" << s << ")=" << carriage.count(s) << endl; for ( it = ret.first; it != ret.second; it++ ) { cout << "(*it).first=" << (*it).first << endl; // error here if ( ((*it).second).recT == recoverTime ) { carriage.erase( it ); } } The EXC_BAD_ACCESS error now appears at the (*it).first call, again after many thousands of successful recoveries. Can anyone give me tips on how to figure out how this problem arises? I'm trying to use gdb. Frame 0 from the backtrace reads "#0 0x0000000100001d50 in Host::recover (this=0x100530d80, s=0, recoverTime=635.91148029170529) at Host.cpp:317" I'm not sure what useful information I can extract here. Update 2 I added a break; after the carriage.erase(it). This works, but I have no idea why (e.g., why it would remove the seg fault at (*it).first.

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  • How to design a C / C++ library to be usable in many client languages?

    - by Brian Schimmel
    I'm planning to code a library that should be usable by a large number of people in on a wide spectrum of platforms. What do I have to consider to design it right? To make this questions more specific, there are four "subquestions" at the end. Choice of language Considering all the known requirements and details, I concluded that a library written in C or C++ was the way to go. I think the primary usage of my library will be in programs written in C, C++ and Java SE, but I can also think of reasons to use it from Java ME, PHP, .NET, Objective C, Python, Ruby, bash scrips, etc... Maybe I cannot target all of them, but if it's possible, I'll do it. Requirements It would be to much to describe the full purpose of my library here, but there are some aspects that might be important to this question: The library itself will start out small, but definitely will grow to enormous complexity, so it is not an option to maintain several versions in parallel. Most of the complexity will be hidden inside the library, though The library will construct an object graph that is used heavily inside. Some clients of the library will only be interested in specific attributes of specific objects, while other clients must traverse the object graph in some way Clients may change the objects, and the library must be notified thereof The library may change the objects, and the client must be notified thereof, if it already has a handle to that object The library must be multi-threaded, because it will maintain network connections to several other hosts While some requests to the library may be handled synchronously, many of them will take too long and must be processed in the background, and notify the client on success (or failure) Of course, answers are welcome no matter if they address my specific requirements, or if they answer the question in a general way that matters to a wider audience! My assumptions, so far So here are some of my assumptions and conclusions, which I gathered in the past months: Internally I can use whatever I want, e.g. C++ with operator overloading, multiple inheritance, template meta programming... as long as there is a portable compiler which handles it (think of gcc / g++) But my interface has to be a clean C interface that does not involve name mangling Also, I think my interface should only consist of functions, with basic/primitive data types (and maybe pointers) passed as parameters and return values If I use pointers, I think I should only use them to pass them back to the library, not to operate directly on the referenced memory For usage in a C++ application, I might also offer an object oriented interface (Which is also prone to name mangling, so the App must either use the same compiler, or include the library in source form) Is this also true for usage in C# ? For usage in Java SE / Java EE, the Java native interface (JNI) applies. I have some basic knowledge about it, but I should definitely double check it. Not all client languages handle multithreading well, so there should be a single thread talking to the client For usage on Java ME, there is no such thing as JNI, but I might go with Nested VM For usage in Bash scripts, there must be an executable with a command line interface For the other client languages, I have no idea For most client languages, it would be nice to have kind of an adapter interface written in that language. I think there are tools to automatically generate this for Java and some others For object oriented languages, it might be possible to create an object oriented adapter which hides the fact that the interface to the library is function based - but I don't know if its worth the effort Possible subquestions is this possible with manageable effort, or is it just too much portability? are there any good books / websites about this kind of design criteria? are any of my assumptions wrong? which open source libraries are worth studying to learn from their design / interface / souce? meta: This question is rather long, do you see any way to split it into several smaller ones? (If you reply to this, do it as a comment, not as an answer)

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  • AsyncPostBackTrigger Just flashing/flicking the UpdatePanel but not updating it

    - by Pankaj
    I am trying UpdatePanel & AsyncPostBackTrigger on master pages through find control method but problem is when I click on button (UpdateButton) It just flash/flick (No Postback) the UpdatePanle but still it don't update or refresh the gridview (images) inside the updatePanel. I have placed script Manger on the master page & an AJAX Update panel in a ContentPlaceHolder in the child page. Also, in another ContentPlaceholder there is an asp button (outside of the UpdatePanel). I want to refresh/reload the AJAX UpdatePanel with this asp button. Thanks for suggestions. Child Page Code :- protected void Page_Load(object sender, EventArgs e) { ScriptManager ScriptManager1 = (ScriptManager)Master.FindControl("ScriptManager1"); ContentPlaceHolder cph = (ContentPlaceHolder)Master.FindControl("cp_Button"); Button btnRefresh = (Button)cph.FindControl("btnRefresh"); ScriptManager1.RegisterAsyncPostBackControl(btnRefresh); } protected void btnRefresh_Click(object sender, EventArgs e) { UpdatePanel1.Update(); } <%@ Page Title="" Language="C#" MasterPageFile="~/InnerMaster.master" AutoEventWireup="true" CodeFile="A.aspx.cs" Inherits="A" Async="true" %> <asp:Content ID="Content3" ContentPlaceHolderID="MainContent" Runat="Server"> <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server"> <ContentTemplate> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="id" DataSourceID="SqlDataSource1"> <Columns> <asp:TemplateField> <ItemTemplate> <asp:Image ID="img12" runat="server" Width="650px" Height="600" ToolTip="A" ImageUrl='<%# Page.ResolveUrl(string.Format("~/Cli/{0}", Eval("image"))) %>' /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> </ContentTemplate> </asp:UpdatePanel> </asp:Content> <asp:Content ID="Content4" ContentPlaceHolderID="cp_Button" Runat="Server"> <asp:Button ID ="btnRefresh" runat="server" onclick="btnRefresh_Click" Height="34" Width="110" Text="More Images" /> </asp:Content> Hi updated code :- Now on click event whole pages is refreshed. using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; namespace EProxy { public class EventProxy : Control, IPostBackEventHandler { public EventProxy() { } public void RaisePostBackEvent(string eventArgument) { } public event EventHandler<EventArgs> EventProxied; protected virtual void OnEventProxy(EventArgs e) { if (this.EventProxied != null) { this.EventProxied(this, e); } } public void ProxyEvent(EventArgs e) { OnEventProxy(e); } } } On Master Page Code (btn click):- protected void btnRefresh_Click(object sender, EventArgs e) { ContentPlaceHolder cph = (ContentPlaceHolder)this.FindControl("MainContent"); EventProxy eventProxy = (EventProxy)cph.FindControl("ProxyControl") as EventProxy; eventProxy.ProxyEvent(e); } Web Config :- <pages maintainScrollPositionOnPostBack="true" enableViewStateMac="true"> <controls> <add tagPrefix="it" namespace="EProxy" assembly="App_Code"/> </controls> </pages>

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  • Why might a System.String object not cache its hash code?

    - by Dan Tao
    A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is implementation-dependent, so the question "is GetHashCode implemented in the form of X or Y?" is not really answerable. I'm just curious about a few things: If Reflector has disassembled the DLL correctly and this is the implementation of GetHashCode (in my environment), am I correct in interpreting this code to indicate that a string object, based on this particular implementation, would not cache its hash code? Assuming the answer is yes, why would this be? It seems to me that the memory cost would be minimal (one more 32-bit integer, a drop in the pond compared to the size of the string itself) whereas the savings would be significant, especially in cases where, e.g., strings are used as keys in a hashtable-based collection like a Dictionary<string, [...]>. And since the string class is immutable, it isn't like the value returned by GetHashCode will ever even change. What could I be missing? UPDATE: In response to Andras Zoltan's closing remark: There's also the point made in Tim's answer(+1 there). If he's right, and I think he is, then there's no guarantee that a string is actually immutable after construction, therefore to cache the result would be wrong. Whoa, whoa there! This is an interesting point to make (and yes it's very true), but I really doubt that this was taken into consideration in the implementation of GetHashCode. The statement "therefore to cache the result would be wrong" implies to me that the framework's attitude regarding strings is "Well, they're supposed to be immutable, but really if developers want to get sneaky they're mutable so we'll treat them as such." This is definitely not how the framework views strings. It fully relies on their immutability in so many ways (interning of string literals, assignment of all zero-length strings to string.Empty, etc.) that, basically, if you mutate a string, you're writing code whose behavior is entirely undefined and unpredictable. I guess my point is that for the author(s) of this implementation to worry, "What if this string instance is modified between calls, even though the class as it is publicly exposed is immutable?" would be like for someone planning a casual outdoor BBQ to think to him-/herself, "What if someone brings an atomic bomb to the party?" Look, if someone brings an atom bomb, party's over.

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  • How do I code this relationship in SQLAlchemy?

    - by Martin Del Vecchio
    I am new to SQLAlchemy (and SQL, for that matter). I can't figure out how to code the idea I have in my head. I am creating a database of performance-test results. A test run consists of a test type and a number (this is class TestRun below) A test suite consists the version string of the software being tested, and one or more TestRun objects (this is class TestSuite below). A test version consists of all test suites with the given version name. Here is my code, as simple as I can make it: from sqlalchemy import * from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import relationship, backref, sessionmaker Base = declarative_base() class TestVersion (Base): __tablename__ = 'versions' id = Column (Integer, primary_key=True) version_name = Column (String) def __init__ (self, version_name): self.version_name = version_name class TestRun (Base): __tablename__ = 'runs' id = Column (Integer, primary_key=True) suite_directory = Column (String, ForeignKey ('suites.directory')) suite = relationship ('TestSuite', backref=backref ('runs', order_by=id)) test_type = Column (String) rate = Column (Integer) def __init__ (self, test_type, rate): self.test_type = test_type self.rate = rate class TestSuite (Base): __tablename__ = 'suites' directory = Column (String, primary_key=True) version_id = Column (Integer, ForeignKey ('versions.id')) version_ref = relationship ('TestVersion', backref=backref ('suites', order_by=directory)) version_name = Column (String) def __init__ (self, directory, version_name): self.directory = directory self.version_name = version_name # Create a v1.0 suite suite1 = TestSuite ('dir1', 'v1.0') suite1.runs.append (TestRun ('test1', 100)) suite1.runs.append (TestRun ('test2', 200)) # Create a another v1.0 suite suite2 = TestSuite ('dir2', 'v1.0') suite2.runs.append (TestRun ('test1', 101)) suite2.runs.append (TestRun ('test2', 201)) # Create another suite suite3 = TestSuite ('dir3', 'v2.0') suite3.runs.append (TestRun ('test1', 102)) suite3.runs.append (TestRun ('test2', 202)) # Create the in-memory database engine = create_engine ('sqlite://') Session = sessionmaker (bind=engine) session = Session() Base.metadata.create_all (engine) # Add the suites in version1 = TestVersion (suite1.version_name) version1.suites.append (suite1) session.add (suite1) version2 = TestVersion (suite2.version_name) version2.suites.append (suite2) session.add (suite2) version3 = TestVersion (suite3.version_name) version3.suites.append (suite3) session.add (suite3) session.commit() # Query the suites for suite in session.query (TestSuite).order_by (TestSuite.directory): print "\nSuite directory %s, version %s has %d test runs:" % (suite.directory, suite.version_name, len (suite.runs)) for run in suite.runs: print " Test '%s', result %d" % (run.test_type, run.rate) # Query the versions for version in session.query (TestVersion).order_by (TestVersion.version_name): print "\nVersion %s has %d test suites:" % (version.version_name, len (version.suites)) for suite in version.suites: print " Suite directory %s, version %s has %d test runs:" % (suite.directory, suite.version_name, len (suite.runs)) for run in suite.runs: print " Test '%s', result %d" % (run.test_type, run.rate) The output of this program: Suite directory dir1, version v1.0 has 2 test runs: Test 'test1', result 100 Test 'test2', result 200 Suite directory dir2, version v1.0 has 2 test runs: Test 'test1', result 101 Test 'test2', result 201 Suite directory dir3, version v2.0 has 2 test runs: Test 'test1', result 102 Test 'test2', result 202 Version v1.0 has 1 test suites: Suite directory dir1, version v1.0 has 2 test runs: Test 'test1', result 100 Test 'test2', result 200 Version v1.0 has 1 test suites: Suite directory dir2, version v1.0 has 2 test runs: Test 'test1', result 101 Test 'test2', result 201 Version v2.0 has 1 test suites: Suite directory dir3, version v2.0 has 2 test runs: Test 'test1', result 102 Test 'test2', result 202 This is not correct, since there are two TestVersion objects with the name 'v1.0'. I hacked my way around this by adding a private list of TestVersion objects, and a function to find a matching one: versions = [] def find_or_create_version (version_name): # Find existing for version in versions: if version.version_name == version_name: return (version) # Create new version = TestVersion (version_name) versions.append (version) return (version) Then I modified my code that adds the records to use it: # Add the suites in version1 = find_or_create_version (suite1.version_name) version1.suites.append (suite1) session.add (suite1) version2 = find_or_create_version (suite2.version_name) version2.suites.append (suite2) session.add (suite2) version3 = find_or_create_version (suite3.version_name) version3.suites.append (suite3) session.add (suite3) Now the output is what I want: Suite directory dir1, version v1.0 has 2 test runs: Test 'test1', result 100 Test 'test2', result 200 Suite directory dir2, version v1.0 has 2 test runs: Test 'test1', result 101 Test 'test2', result 201 Suite directory dir3, version v2.0 has 2 test runs: Test 'test1', result 102 Test 'test2', result 202 Version v1.0 has 2 test suites: Suite directory dir1, version v1.0 has 2 test runs: Test 'test1', result 100 Test 'test2', result 200 Suite directory dir2, version v1.0 has 2 test runs: Test 'test1', result 101 Test 'test2', result 201 Version v2.0 has 1 test suites: Suite directory dir3, version v2.0 has 2 test runs: Test 'test1', result 102 Test 'test2', result 202 This feels wrong to me; it doesn't feel right that I am manually keeping track of the unique version names, and manually adding the suites to the appropriate TestVersion objects. Is this code even close to being correct? And what happens when I'm not building the entire database from scratch, as in this example. If the database already exists, do I have to query the database's TestVersion table to discover the unique version names? Thanks in advance. I know this is a lot of code to wade through, and I appreciate the help.

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  • Languages and VMs: Features that are hard to optimize and why

    - by mrjoltcola
    I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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  • easiest and best way to make a server queue java

    - by houlahan
    i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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  • evaluating cost/benefits of using extension methods in C# => 3.0

    - by BillW
    Hi, In what circumstances (usage scenarios) would you choose to write an extension rather than sub-classing an object ? < full disclosure : I am not an MS employee; I do not know Mitsu Furota personally; I do know the author of the open-source Componax library mentioned here, but I have no business dealings with him whatsoever; I am not creating, or planning to create any commercial product using extensions : in sum : this post is from pure intellectal curiousity related to my trying to (continually) become aware of "best practices" I find the idea of extension methods "cool," and obviously you can do "far-out" things with them as in the many examples you can in Mitsu Furota's (MS) blog postslink text. A personal friend wrote the open-source Componax librarylink text, and there's some remarkable facilities in there; but he is in complete command of his small company with total control over code guidelines, and every line of code "passes through his hands." While this is speculation on my part : I think/guess other issues might come into play in a medium-to-large software team situation re use of Extensions. Looking at MS's guidelines at link text, you find : In general, you will probably be calling extension methods far more often than implementing your own. ... In general, we recommend that you implement extension methods sparingly and only when you have to. Whenever possible, client code that must extend an existing type should do so by creating a new type derived from the existing type. For more information, see Inheritance (C# Programming Guide). ... When the compiler encounters a method invocation, it first looks for a match in the type's instance methods. If no match is found, it will search for any extension methods that are defined for the type, and bind to the first extension method that it finds. And at Ms's link text : Extension methods present no specific security vulnerabilities. They can never be used to impersonate existing methods on a type, because all name collisions are resolved in favor of the instance or static method defined by the type itself. Extension methods cannot access any private data in the extended class. Factors that seem obvious to me would include : I assume you would not write an extension unless you expected it be used very generally and very frequently. On the other hand : couldn't you say the same thing about sub-classing ? Knowing we can compile them into a seperate dll, and add the compiled dll, and reference it, and then use the extensions : is "cool," but does that "balance out" the cost inherent in the compiler first having to check to see if instance methods are defined as described above. Or the cost, in case of a "name clash," of using the Static invocation methods to make sure your extension is invoked rather than the instance definition ? How frequent use of Extensions would affect run-time performance or memory use : I have no idea. So, I'd appreciate your thoughts, or knowing about how/when you do, or don't do, use Extensions, compared to sub-classing. thanks, Bill

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  • java.lang.OutOfMemoryError: bitmap size exceeds VM budget

    - by Angel
    Hi, I am trying to change the layout of my application from portrait to landscape and vice-versa. But if i do it frequently or more than once then at times my application crashes.. Below is the error log. Please suggest what can be done? < 01-06 09:52:27.787: ERROR/dalvikvm-heap(17473): 1550532-byte external allocation too large for this process. 01-06 09:52:27.787: ERROR/dalvikvm(17473): Out of memory: Heap Size=6471KB, Allocated=4075KB, Bitmap Size=9564KB 01-06 09:52:27.787: ERROR/(17473): VM won't let us allocate 1550532 bytes 01-06 09:52:27.798: DEBUG/skia(17473): --- decoder-decode returned false 01-06 09:52:27.798: DEBUG/AndroidRuntime(17473): Shutting down VM 01-06 09:52:27.798: WARN/dalvikvm(17473): threadid=3: thread exiting with uncaught exception (group=0x4001e390) 01-06 09:52:27.807: ERROR/AndroidRuntime(17473): Uncaught handler: thread main exiting due to uncaught exception 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): java.lang.RuntimeException: Unable to start activity ComponentInfo{}: android.view.InflateException: Binary XML file line #2: Error inflating class 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3812) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.access$2300(ActivityThread.java:126) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1936) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.os.Handler.dispatchMessage(Handler.java:99) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.os.Looper.loop(Looper.java:123) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.main(ActivityThread.java:4595) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Method.invokeNative(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Method.invoke(Method.java:521) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at dalvik.system.NativeStart.main(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: android.view.InflateException: Binary XML file line #2: Error inflating class 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createView(LayoutInflater.java:513) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:56) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:563) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:385) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:320) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:276) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:207) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.Activity.setContentView(Activity.java:1629) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at onCreate(Game.java:98) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2544) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 12 more 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: java.lang.reflect.InvocationTargetException 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.widget.LinearLayout.(LinearLayout.java:92) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Constructor.constructNative(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Constructor.newInstance(Constructor.java:446) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createView(LayoutInflater.java:500) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 22 more 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: java.lang.OutOfMemoryError: bitmap size exceeds VM budget 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:464) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:340) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:697) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.content.res.Resources.loadDrawable(Resources.java:1705) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.content.res.TypedArray.getDrawable(TypedArray.java:548) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.View.(View.java:1850) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.View.(View.java:1799) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.ViewGroup.(ViewGroup.java:296) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 26 more

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  • Efficient representation of Hierarchies in Hibernate.

    - by Alison G
    I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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  • Performance issues with jms and spring integration. What is wrong with the following configuration?

    - by user358448
    I have a jms producer, which generates many messages per second, which are sent to amq persistent queue and are consumed by single consumer, which needs to process them sequentially. But it seems that the producer is much faster than the consumer and i am having performance and memory problems. Messages are fetched very very slowly and the consuming seems to happen on intervals (the consumer "asks" for messages in polling fashion, which is strange?!) Basically everything happens with spring integration. Here is the configuration at the producer side. First stake messages come in stakesInMemoryChannel, from there, they are filtered throw the filteredStakesChannel and from there they are going into the jms queue (using executor so the sending will happen in separate thread) <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <int:channel id="stakesInMemoryChannel" /> <int:channel id="filteredStakesChannel" > <int:dispatcher task-executor="taskExecutor"/> </int:channel> <bean id="stakeFilterService" class="cayetano.games.stake.StakeFilterService"/> <int:filter input-channel="stakesInMemoryChannel" output-channel="filteredStakesChannel" throw-exception-on-rejection="false" expression="true"/> <jms:outbound-channel-adapter channel="filteredStakesChannel" destination="stakesQueue" delivery-persistent="true" explicit-qos-enabled="true" /> <task:executor id="taskExecutor" pool-size="100" /> The other application is consuming the messages like this... The messages come in stakesInputChannel from the jms stakesQueue, after that they are routed to 2 separate channels, one persists the message and the other do some other stuff, lets call it "processing". <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <jms:message-driven-channel-adapter channel="stakesInputChannel" destination="stakesQueue" acknowledge="auto" concurrent-consumers="1" max-concurrent-consumers="1" /> <int:publish-subscribe-channel id="stakesInputChannel" /> <int:channel id="persistStakesChannel" /> <int:channel id="processStakesChannel" /> <int:recipient-list-router id="customRouter" input-channel="stakesInputChannel" timeout="3000" ignore-send-failures="true" apply-sequence="true" > <int:recipient channel="persistStakesChannel"/> <int:recipient channel="processStakesChannel"/> </int:recipient-list-router> <bean id="prefetchPolicy" class="org.apache.activemq.ActiveMQPrefetchPolicy"> <property name="queuePrefetch" value="${jms.broker.prefetch.policy}" /> </bean> <bean id="connectionFactory" class="org.springframework.jms.connection.CachingConnectionFactory"> <property name="targetConnectionFactory"> <bean class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="${jms.broker.url}" /> <property name="prefetchPolicy" ref="prefetchPolicy" /> <property name="optimizeAcknowledge" value="true" /> <property name="useAsyncSend" value="true" /> </bean> </property> <property name="sessionCacheSize" value="10"/> <property name="cacheProducers" value="false"/> </bean>

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  • segmented controls mangled during initial transition animation

    - by dLux
    greetings and salutations folks, i'm relatively new to objective c & iphone programming, so bare with me if i've overlooked something obvious.. i created a simple app to play with the different transition animations, setting up a couple segmented controls and a slider.. (Flip/Curl), (left/right) | (up/down), (EaseInOut/EaseIn/EaseOut/Linear) i created a view controller class, and the super view controller switches between 2 instances of the sub class. as you can see from the following image, the first time switching to the 2nd instance, while the animation is occurring the segmented controls are mangled; i'd guess they haven't had enuff time to draw themselves completely.. http://img689.imageshack.us/img689/2320/mangledbuttonsduringtra.png they're fine once the animation is done, and any subsequent times.. if i specify cache:NO in the setAnimationTransition it helps, but there still seems to be some sort of progressive reveal for the text in the segmented controls; they still don't seem to be pre-rendered or initialized properly.. (and surely there's a way to do this while caching the view being transitioned to, since in this case the view isn't changing and should be cacheable.) i'm building my code based on a couple tutorials from a book, so i updated the didReceiveMemoryWarning to set the instanced view controllers to nil; when i invoke a memory warning in the simulator, i assume it's purging the other view, and it acts like a first transition after loading, the view being transitioned to appears just like the image above.. i guess it can't hurt to include the code (sorry if it's considered spamming), this is basically half of it, with a similar chunk following this in an else statement, for the case of the 2nd side being present, switching back to the 1st..: - (IBAction)switchViews:(id)sender { [UIView beginAnimations:@"Transition Animation" context:nil]; if (self.sideBViewController.view.superview == nil) // sideA is active, sideB is coming { if (self.sideBViewController == nil) { SideAViewController *sBController = [[SideAViewController alloc] initWithNibName:@"SideAViewController" bundle:nil]; self.sideBViewController = sBController; [sBController release]; } [UIView setAnimationDuration:sideAViewController.transitionDurationSlider.value]; if ([sideAViewController.transitionAnimation selectedSegmentIndex] == 0) { // flip: 0 == left, 1 == right if ([sideAViewController.flipDirection selectedSegmentIndex] == 0) [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES]; else [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES]; } else { // curl: 0 == up, 1 == down if ([sideAViewController.curlDirection selectedSegmentIndex] == 0) [UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES]; else [UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.view cache:YES]; } if ([sideAViewController.animationCurve selectedSegmentIndex] == 0) [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; else if ([sideAViewController.animationCurve selectedSegmentIndex] == 1) [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; else if ([sideAViewController.animationCurve selectedSegmentIndex] == 2) [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; else if ([sideAViewController.animationCurve selectedSegmentIndex] == 3) [UIView setAnimationCurve:UIViewAnimationCurveLinear]; [sideBViewController viewWillAppear:YES]; [sideAViewController viewWillDisappear:YES]; [sideAViewController.view removeFromSuperview]; [self.view insertSubview:sideBViewController.view atIndex:0]; [sideBViewController viewDidAppear:YES]; [sideAViewController viewDidDisappear:YES]; } any other tips or pointers about writing good clean code is also appreciated, i realize i still have a lot to learn.. thank u for ur time, -- d

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  • Where should I create my DbCommand instances?

    - by Domenic
    I seemingly have two choices: Make my class implement IDisposable. Create my DbCommand instances as private readonly fields, and in the constructor, add the parameters that they use. Whenever I want to write to the database, bind to these parameters (reusing the same command instances), set the Connection and Transaction properties, then call ExecuteNonQuery. In the Dispose method, call Dispose on each of these fields. Each time I want to write to the database, write using(var cmd = new DbCommand("...", connection, transaction)) around the usage of the command, and add parameters and bind to them every time as well, before calling ExecuteNonQuery. I assume I don't need a new command for each query, just a new command for each time I open the database (right?). Both of these seem somewhat inelegant and possibly incorrect. For #1, it is annoying for my users that I this class is now IDisposable just because I have used a few DbCommands (which should be an implementation detail that they don't care about). I also am somewhat suspicious that keeping a DbCommand instance around might inadvertently lock the database or something? For #2, it feels like I'm doing a lot of work (in terms of .NET objects) each time I want to write to the database, especially with the parameter-adding. It seems like I create the same object every time, which just feels like bad practice. For reference, here is my current code, using #1: using System; using System.Net; using System.Data.SQLite; public class Class1 : IDisposable { private readonly SQLiteCommand updateCookie = new SQLiteCommand("UPDATE moz_cookies SET value = @value, expiry = @expiry, isSecure = @isSecure, isHttpOnly = @isHttpOnly WHERE name = @name AND host = @host AND path = @path"); public Class1() { this.updateCookie.Parameters.AddRange(new[] { new SQLiteParameter("@name"), new SQLiteParameter("@value"), new SQLiteParameter("@host"), new SQLiteParameter("@path"), new SQLiteParameter("@expiry"), new SQLiteParameter("@isSecure"), new SQLiteParameter("@isHttpOnly") }); } private static void BindDbCommandToMozillaCookie(DbCommand command, Cookie cookie) { long expiresSeconds = (long)cookie.Expires.TotalSeconds; command.Parameters["@name"].Value = cookie.Name; command.Parameters["@value"].Value = cookie.Value; command.Parameters["@host"].Value = cookie.Domain; command.Parameters["@path"].Value = cookie.Path; command.Parameters["@expiry"].Value = expiresSeconds; command.Parameters["@isSecure"].Value = cookie.Secure; command.Parameters["@isHttpOnly"].Value = cookie.HttpOnly; } public void WriteCurrentCookiesToMozillaBasedBrowserSqlite(string databaseFilename) { using (SQLiteConnection connection = new SQLiteConnection("Data Source=" + databaseFilename)) { connection.Open(); using (SQLiteTransaction transaction = connection.BeginTransaction()) { this.updateCookie.Connection = connection; this.updateCookie.Transaction = transaction; foreach (Cookie cookie in SomeOtherClass.GetCookieArray()) { Class1.BindDbCommandToMozillaCookie(this.updateCookie, cookie); this.updateCookie.ExecuteNonQuery(); } transaction.Commit(); } } } #region IDisposable implementation protected virtual void Dispose(bool disposing) { if (!this.disposed && disposing) { this.updateCookie.Dispose(); } this.disposed = true; } public void Dispose() { this.Dispose(true); GC.SuppressFinalize(this); } ~Class1() { this.Dispose(false); } private bool disposed; #endregion }

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  • ASP.NET MVC - Form Post always redirect when I just want to bind json result to a div

    - by Saxman
    Hi all, I'm having a little problem with json result. I'm submitting a contact form, and after the submission, I just want to return some json data (indicating either a success or failed and displays a message) back to the view, without causing a redirect, but it kept redirecting me to the action, here are the codes: HTML <div id="contactForm2" class="grid_6"> <div id="contactFormContainer"> @using (Html.BeginForm(MVC.Home.ActionNames.ContactForm, MVC.Home.Name, FormMethod.Post, new { id = "contactForm" })) { <p> <input type="text" tabindex="1" size="22" value="" id="contactName" class="text_input required" name="contactName" /> <label for="contactName"> <strong class="leftSpace">Your Name (required)</strong></label></p> <p> <input type="text" tabindex="2" size="22" value="" id="contactEmail" class="text_input required" name="contactEmail" /> <label for="contactEmail"> <strong class="leftSpace">Email (required)</strong></label></p> <p> <input type="text" tabindex="2" size="22" value="" id="contactPhone" class="text_input" name="contactPhone" /> <label for="contactPhone"> <strong class="leftSpace">Phone</strong></label></p> <p> <label> <strong class="leftSpace n">Message (required)</strong></label> <textarea tabindex="4" rows="4" cols="56" id="contactMessage" class="text_area required" name="contactMessage"></textarea></p> <p> <input type="submit" value="Send" tabindex="5" id="contactSubmit" class="button submit" name="contactSubmit" /></p> } </div> <div id="contactFormStatus"> </div> </div> Controller [HttpPost] public virtual JsonResult ContactForm(FormCollection formCollection) { var name = formCollection["contactName"]; var email = formCollection["contactEmail"]; var phone = formCollection["contactPhone"]; var message = formCollection["contactMessage"]; if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(email) || string.IsNullOrEmpty(message)) { return Json(new { success = false, message = "Please complete all the required fields so that I can get back to you. Thanks." }); } // Insert contact form data here... return Json(new { success = true, message = "Your inquery has been sent. Thank you." }); } javascript $(document).ready(function () { $('#contactSubmit').live('click', function () { var form = $('#contactForm'); var formData = form.serialize(); $.post('/Home/ContactForm', formData, function (result) { var status = $('#contactFormStatus'); if (result.success) { $('#contactForm')[0].reset; } status.append(result.message); }, 'json' ); return false; }); }); I've also tried this javascript, but also got a redirect $(document).ready(function () { $('#contactSubmit').live('click', function () { var form = $('#contactForm'); var formData = form.serialize(); $.ajax({ type: 'POST', url: '/Home/ContactForm', data: formData, success: function (result) { SubmitContactResult(result); }, cache: false }); }); function SubmitContactResult(result) { var status = $('#contactFormStatus'); if (result.success) { $('#contactForm')[0].reset; } status.append(result.message); } }); Any idea what's going on with my code? Thank you very much.

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  • inserting new relationship data in core-data

    - by michael
    My app will allow users to create a personalised list of events from a large list of events. I have a table view which simply displays these events, tapping on one of them takes the user to the event details view, which has a button "add to my events". In this detailed view I own the original event object, retrieved via an NSFetchedResultsController and passed to the detailed view (via a table cell, the same as the core data recipes sample). I have no trouble retrieving/displaying information from this "event". I am then trying to add it to the list of MyEvents represented by a one to many (inverse) relationship: This code: NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; [myEvents addEventObject:event];//ERROR And this code (suggested below): //would this add to or overwrite the "list" i am attempting to maintain NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; NSMutableSet *myEvent = [myEvents mutableSetValueForKey:@"event"]; [myEvent addObject:event]; //ERROR Bot produce (at the line indicated by //ERROR): *** -[NSComparisonPredicate evaluateWithObject:]: message sent to deallocated instance Seems I may have missed something fundamental. I cant glean any more information through the use of debugging tools, with my knowledge of them. 1) Is this a valid way to compile and store an editable list like this? 2) Is there a better way? 3) What could possibly be the deallocated instance in error? -- I have now modified the Event entity to have a to-many relationship called "myEvents" which referrers to itself. I can add Events to this fine, and logging the object shows the correct memory addresses appearing for the relationship after a [event addMyEventObject:event];. The same failure happens right after this however. I am still at a loss to understand what is going wrong. This is the backtrace #0 0x01f753a7 in ___forwarding___ () #1 0x01f516c2 in __forwarding_prep_0___ () #2 0x01c5aa8f in -[NSFetchedResultsController(PrivateMethods) _preprocessUpdatedObjects:insertsInfo:deletesInfo:updatesInfo:sectionsWithDeletes:newSectionNames:treatAsRefreshes:] () #3 0x01c5d63b in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] () #4 0x0002e63a in _nsnote_callback () #5 0x01f40005 in _CFXNotificationPostNotification () #6 0x0002bef0 in -[NSNotificationCenter postNotificationName:object:userInfo:] () #7 0x01bbe17d in -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:] () #8 0x01c1d763 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _createAndPostChangeNotification:withDeletions:withUpdates:withRefreshes:] () #9 0x01ba25ea in -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] () #10 0x01bdfb3a in -[NSManagedObjectContext processPendingChanges] () #11 0x01bd0957 in _performRunLoopAction () #12 0x01f4d252 in __CFRunLoopDoObservers () #13 0x01f4c65f in CFRunLoopRunSpecific () #14 0x01f4bc48 in CFRunLoopRunInMode () #15 0x0273878d in GSEventRunModal () #16 0x02738852 in GSEventRun () #17 0x002ba003 in UIApplicationMain () solution I managed to get to the bottom of this. I was fetching the event in question using a NSFetchedResultsController with a NSPredicate which I was releasing after I had the results. Retrieving values from the entities returned was no problem, but when I tried to update any of them it gave the error above. It should not have been released. oustanding part of my question What is a good way to create this sub list from a list of existing items in terms of a core data model. I don't believe its any of the ways I tried here. I need to show/edit it in another table view. Perhaps there is a better way than a boolean property on each event entity? The relationship idea above doesn't seem to work here (even though I can now create it). Cheers.

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  • Concurrency and Calendar classes

    - by fbielejec
    I have a thread (class implementing runnable, called AnalyzeTree) organised around a hash map (ConcurrentMap slicesMap). The class goes through the data (called trees here) in the large text file and parses the geographical coordinates from it to the HashMap. The idea is to process one tree at a time and add or grow the values according to the key (which is just a Double value representing time). The relevant part of code looks like this: // grow map entry if key exists if (slicesMap.containsKey(sliceTime)) { double[] imputedLocation = imputeValue( location, parentLocation, sliceHeight, nodeHeight, parentHeight, rate, useTrueNoise, currentTreeNormalization, precisionArray); slicesMap.get(sliceTime).add( new Coordinates(imputedLocation[1], imputedLocation[0], 0.0)); // start new entry if no such key in the map } else { List<Coordinates> coords = new ArrayList<Coordinates>(); double[] imputedLocation = imputeValue( location, parentLocation, sliceHeight, nodeHeight, parentHeight, rate, useTrueNoise, currentTreeNormalization, precisionArray); coords.add(new Coordinates(imputedLocation[1], imputedLocation[0], 0.0)); slicesMap.putIfAbsent(sliceTime, coords); // slicesMap.put(sliceTime, coords); }// END: key check And the class is called like this (executor is ExecutorService executor = Executors.newFixedThreadPool(NTHREDS) ): mrsd = new SpreadDate(mrsdString); int readTrees = 1; while (treesImporter.hasTree()) { currentTree = (RootedTree) treesImporter.importNextTree(); executor.submit(new AnalyzeTree(currentTree, precisionString, coordinatesName, rateString, numberOfIntervals, treeRootHeight, timescaler, mrsd, slicesMap, useTrueNoise)); // new AnalyzeTree(currentTree, precisionString, // coordinatesName, rateString, numberOfIntervals, // treeRootHeight, timescaler, mrsd, slicesMap, // useTrueNoise).run(); readTrees++; }// END: while has trees Now this is running into troubles when executed in parallel (the commented part running sequentially is fine), I thought it might throw a ConcurrentModificationException, but apparently the problem is in mrsd (instance of SpreadDate object, which is simply a class for date related calculations). The SpreadDate class looks like this: public class SpreadDate { private Calendar cal; private SimpleDateFormat formatter; private Date stringdate; public SpreadDate(String date) throws ParseException { // if no era specified assume current era String line[] = date.split(" "); if (line.length == 1) { StringBuilder properDateStringBuilder = new StringBuilder(); date = properDateStringBuilder.append(date).append(" AD") .toString(); } formatter = new SimpleDateFormat("yyyy-MM-dd G", Locale.US); stringdate = formatter.parse(date); cal = Calendar.getInstance(); } public long plus(int days) { cal.setTime(stringdate); cal.add(Calendar.DATE, days); return cal.getTimeInMillis(); }// END: plus public long minus(int days) { cal.setTime(stringdate); cal.add(Calendar.DATE, -days); //line 39 return cal.getTimeInMillis(); }// END: minus public long getTime() { cal.setTime(stringdate); return cal.getTimeInMillis(); }// END: getDate } And the stack trace from when exception is thrown: java.lang.ArrayIndexOutOfBoundsException: 58 at sun.util.calendar.BaseCalendar.getCalendarDateFromFixedDate(BaseCalendar.java:454) at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:2098) at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:2013) at java.util.Calendar.setTimeInMillis(Calendar.java:1126) at java.util.GregorianCalendar.add(GregorianCalendar.java:1020) at utils.SpreadDate.minus(SpreadDate.java:39) at templates.AnalyzeTree.run(AnalyzeTree.java:88) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) If a move the part initializing mrsd to the AnalyzeTree class it runs without any problems - however it is not very memory efficient to initialize class each time this thread is running, hence my concerns. How can it be remedied?

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  • Two-way databinding of a custom templated control. Eval works, but not Bind.

    - by Jason
    I hate long code snippets and I'm sorry about this one, but it turns out that this asp.net stuff can't get much shorter and it's so specific that I haven't been able to generalize it without a full code listing. I just want simple two-way, declarative databinding to a single instance of an object. Not a list of objects of a type with a bunch of NotImplementedExceptions for Add, Delete, and Select, but just a single view-state persisted object. This is certainly something that can be done but I've struggled with an implementation for years. This newest, closest implementation was inspired by this article from 4-Guys-From-Rolla, http://msdn.microsoft.com/en-us/library/aa478964.aspx. Unfortunately, after implementing, I'm getting the following error and I don't know what I'm missing: System.InvalidOperationException: Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control. If I don't use Bind(), and only use Eval() functionality, it works. In that way, the error is especially confusing. Here's the simplified codeset that still produces the error: using System.ComponentModel; namespace System.Web.UI.WebControls.Special { public class SampleFormData { public string SampleString = "Sample String Data"; public int SampleInt = -1; } [ToolboxItem(false)] public class SampleSpecificFormDataContainer : WebControl, INamingContainer { SampleSpecificEntryForm entryForm; internal SampleSpecificEntryForm EntryForm { get { return entryForm; } } [Bindable(true), Category("Data")] public string SampleString { get { return entryForm.FormData.SampleString; } set { entryForm.FormData.SampleString = value; } } [Bindable(true), Category("Data")] public int SampleInt { get { return entryForm.FormData.SampleInt; } set { entryForm.FormData.SampleInt = value; } } internal SampleSpecificFormDataContainer(SampleSpecificEntryForm entryForm) { this.entryForm = entryForm; } } public class SampleSpecificEntryForm : WebControl, INamingContainer { #region Template private IBindableTemplate formTemplate = null; [Browsable(false), DefaultValue(null), TemplateContainer(typeof(SampleSpecificFormDataContainer), ComponentModel.BindingDirection.TwoWay), PersistenceMode(PersistenceMode.InnerProperty)] public virtual IBindableTemplate FormTemplate { get { return formTemplate; } set { formTemplate = value; } } #endregion #region Viewstate SampleFormData FormDataVS { get { return (ViewState["FormData"] as SampleFormData) ?? new SampleFormData(); } set { ViewState["FormData"] = value; SaveViewState(); } } #endregion public override ControlCollection Controls { get { EnsureChildControls(); return base.Controls; } } private SampleSpecificFormDataContainer formDataContainer = null; [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)] public SampleSpecificFormDataContainer FormDataContainer { get { EnsureChildControls(); return formDataContainer; } } [Bindable(true), Browsable(false)] public SampleFormData FormData { get { return FormDataVS; } set { FormDataVS = value; } } protected override void CreateChildControls() { if (!this.ChildControlsCreated) { Controls.Clear(); formDataContainer = new SampleSpecificFormDataContainer(this); Controls.Add(formDataContainer); FormTemplate.InstantiateIn(formDataContainer); this.ChildControlsCreated = true; } } public override void DataBind() { CreateChildControls(); base.DataBind(); } } } With an ASP.NET page the following: <%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="Default2.aspx.cs" Inherits="EntryFormTest._Default2" EnableEventValidation="false" %> <%@ Register Assembly="EntryForm" Namespace="System.Web.UI.WebControls.Special" TagPrefix="cc1" %> <asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent"> </asp:Content> <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"> <h2> Welcome to ASP.NET! </h2> <cc1:SampleSpecificEntryForm ID="EntryForm1" runat="server"> <FormTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("SampleString") %>'></asp:TextBox><br /> <h3>(<%# Container.SampleString %>)</h3><br /> <asp:Button ID="Button1" runat="server" Text="Button" /> </FormTemplate> </cc1:SampleSpecificEntryForm> </asp:Content> Default2.aspx.cs using System; namespace EntryFormTest { public partial class _Default2 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { EntryForm1.DataBind(); } } } Thanks for any help!

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  • OutOfMemoryError during the pdf merge

    - by Vijay
    the below code merges the pdf files and returns the combined pdf data. while this code runs, i try to combine the 100 files with each file approximately around 500kb, i get outofmemory error in the line document.close();. this code runs in the web environment, is the memory available to webspehere server is the problem? i read in an article to use freeReader method, but i cannot get how to use it my scenario. protected ByteArrayOutputStream joinPDFs(List<InputStream> pdfStreams, boolean paginate) { Document document = new Document(); ByteArrayOutputStream mergedPdfStream = new ByteArrayOutputStream(); try { //List<InputStream> pdfs = pdfStreams; List<PdfReader> readers = new ArrayList<PdfReader>(); int totalPages = 0; //Iterator<InputStream> iteratorPDFs = pdfs.iterator(); Iterator<InputStream> iteratorPDFs = pdfStreams.iterator(); // Create Readers for the pdfs. while (iteratorPDFs.hasNext()) { InputStream pdf = iteratorPDFs.next(); if (pdf == null) continue; PdfReader pdfReader = new PdfReader(pdf); readers.add(pdfReader); totalPages += pdfReader.getNumberOfPages(); } //clear this pdfStreams = null; //WeakReference ref = new WeakReference(pdfs); //ref.clear(); // Create a writer for the outputstream PdfWriter writer = PdfWriter.getInstance(document, mergedPdfStream); writer.setFullCompression(); document.open(); BaseFont bf = BaseFont.createFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED); PdfContentByte cb = writer.getDirectContent(); // Holds the PDF // data PdfImportedPage page; int currentPageNumber = 0; int pageOfCurrentReaderPDF = 0; Iterator<PdfReader> iteratorPDFReader = readers.iterator(); // Loop through the PDF files and add to the output. while (iteratorPDFReader.hasNext()) { PdfReader pdfReader = iteratorPDFReader.next(); // Create a new page in the target for each source page. while (pageOfCurrentReaderPDF < pdfReader.getNumberOfPages()) { pageOfCurrentReaderPDF++; document.setPageSize(pdfReader .getPageSizeWithRotation(pageOfCurrentReaderPDF)); document.newPage(); // pageOfCurrentReaderPDF++; currentPageNumber++; page = writer.getImportedPage(pdfReader, pageOfCurrentReaderPDF); cb.addTemplate(page, 0, 0); // Code for pagination. if (paginate) { cb.beginText(); cb.setFontAndSize(bf, 9); cb.showTextAligned(PdfContentByte.ALIGN_CENTER, "" + currentPageNumber + " of " + totalPages, 520, 5, 0); cb.endText(); } } pageOfCurrentReaderPDF = 0; System.out.println("now the size is: "+pdfReader.getFileLength()); } mergedPdfStream.flush(); document.close(); mergedPdfStream.close(); return mergedPdfStream; } catch (Exception e) { e.printStackTrace(); } finally { if (document.isOpen()) document.close(); try { if (mergedPdfStream != null) mergedPdfStream.close(); } catch (IOException ioe) { ioe.printStackTrace(); } } return mergedPdfStream; } Thanks V

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