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  • What is the memoy size of a Java object array after it has been created?

    - by brenns10
    This probably doesn't even need asking, but I want to make sure I'm right on this. When you create an array of any object in Java like so: Object[] objArr = new Object[10]; The variable objArr is located in stack memory, and it points to a location in the heap where the array object is located. The size of that array in the heap is equal to a 12 byte object header + 4 (or 8, depending on the reference size) bytes * the number of entries in the array. Is this accurate? My question, then, is as follows. Since the array above is empty, does it take up 12 + 4*10 = 52 bytes of memory in the heap immediately after the execution of that line of code? Or does the JVM wait until you start putting things into the array before it instantiates it? Do the null references in the array take up space?

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  • Optimizing collision engine bottleneck

    - by Vittorio Romeo
    Foreword: I'm aware that optimizing this bottleneck is not a necessity - the engine is already very fast. I, however, for fun and educational purposes, would love to find a way to make the engine even faster. I'm creating a general-purpose C++ 2D collision detection/response engine, with an emphasis on flexibility and speed. Here's a very basic diagram of its architecture: Basically, the main class is World, which owns (manages memory) of a ResolverBase*, a SpatialBase* and a vector<Body*>. SpatialBase is a pure virtual class which deals with broad-phase collision detection. ResolverBase is a pure virtual class which deals with collision resolution. The bodies communicate to the World::SpatialBase* with SpatialInfo objects, owned by the bodies themselves. There currenly is one spatial class: Grid : SpatialBase, which is a basic fixed 2D grid. It has it's own info class, GridInfo : SpatialInfo. Here's how its architecture looks: The Grid class owns a 2D array of Cell*. The Cell class contains two collection of (not owned) Body*: a vector<Body*> which contains all the bodies that are in the cell, and a map<int, vector<Body*>> which contains all the bodies that are in the cell, divided in groups. Bodies, in fact, have a groupId int that is used for collision groups. GridInfo objects also contain non-owning pointers to the cells the body is in. As I previously said, the engine is based on groups. Body::getGroups() returns a vector<int> of all the groups the body is part of. Body::getGroupsToCheck() returns a vector<int> of all the groups the body has to check collision against. Bodies can occupy more than a single cell. GridInfo always stores non-owning pointers to the occupied cells. After the bodies move, collision detection happens. We assume that all bodies are axis-aligned bounding boxes. How broad-phase collision detection works: Part 1: spatial info update For each Body body: Top-leftmost occupied cell and bottom-rightmost occupied cells are calculated. If they differ from the previous cells, body.gridInfo.cells is cleared, and filled with all the cells the body occupies (2D for loop from the top-leftmost cell to the bottom-rightmost cell). body is now guaranteed to know what cells it occupies. For a performance boost, it stores a pointer to every map<int, vector<Body*>> of every cell it occupies where the int is a group of body->getGroupsToCheck(). These pointers get stored in gridInfo->queries, which is simply a vector<map<int, vector<Body*>>*>. body is now guaranteed to have a pointer to every vector<Body*> of bodies of groups it needs to check collision against. These pointers are stored in gridInfo->queries. Part 2: actual collision checks For each Body body: body clears and fills a vector<Body*> bodiesToCheck, which contains all the bodies it needs to check against. Duplicates are avoided (bodies can belong to more than one group) by checking if bodiesToCheck already contains the body we're trying to add. const vector<Body*>& GridInfo::getBodiesToCheck() { bodiesToCheck.clear(); for(const auto& q : queries) for(const auto& b : *q) if(!contains(bodiesToCheck, b)) bodiesToCheck.push_back(b); return bodiesToCheck; } The GridInfo::getBodiesToCheck() method IS THE BOTTLENECK. The bodiesToCheck vector must be filled for every body update because bodies could have moved meanwhile. It also needs to prevent duplicate collision checks. The contains function simply checks if the vector already contains a body with std::find. Collision is checked and resolved for every body in bodiesToCheck. That's it. So, I've been trying to optimize this broad-phase collision detection for quite a while now. Every time I try something else than the current architecture/setup, something doesn't go as planned or I make assumption about the simulation that later are proven to be false. My question is: how can I optimize the broad-phase of my collision engine maintaining the grouped bodies approach? Is there some kind of magic C++ optimization that can be applied here? Can the architecture be redesigned in order to allow for more performance? Actual implementation: SSVSCollsion Body.h, Body.cpp World.h, World.cpp Grid.h, Grid.cpp Cell.h, Cell.cpp GridInfo.h, GridInfo.cpp

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  • ensime scala errors (class scala.Array not found, object scala not found)

    - by Jeff Bowman
    I've installed ensime according to the README.md file, however, I get errors in the inferior-ensime-server buffer with the following: INFO: Fatal Error: scala.tools.nsc.MissingRequirementError: object scala not found. scala.tools.nsc.MissingRequirementError: object scala not found. at scala.tools.nsc.symtab.Definitions$definitions$.getModuleOrClass(Definitions.scala:516) at scala.tools.nsc.symtab.Definitions$definitions$.ScalaPackage(Definitions.scala:43) at scala.tools.nsc.symtab.Definitions$definitions$.ScalaPackageClass(Definitions.scala:44) at scala.tools.nsc.symtab.Definitions$definitions$.UnitClass(Definitions.scala:89) at scala.tools.nsc.symtab.Definitions$definitions$.init(Definitions.scala:786) at scala.tools.nsc.Global$Run.(Global.scala:593) at scala.tools.nsc.interactive.Global$TyperRun.(Global.scala:473) at scala.tools.nsc.interactive.Global.newTyperRun(Global.scala:535) at scala.tools.nsc.interactive.Global.reloadSources(Global.scala:289) at scala.tools.nsc.interactive.Global$$anonfun$reload$1.apply(Global.scala:300) at scala.tools.nsc.interactive.Global$$anonfun$reload$1.apply(Global.scala:300) at scala.tools.nsc.interactive.Global.respond(Global.scala:276) at scala.tools.nsc.interactive.Global.reload(Global.scala:300) at scala.tools.nsc.interactive.CompilerControl$$anon$1.apply$mcV$sp(CompilerControl.scala:81) at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:132) at scala.tools.nsc.interactive.Global$$anon$2.run(Global.scala:192) also: INFO: Fatal Error: scala.tools.nsc.MissingRequirementError: class scala.Array not found. scala.tools.nsc.MissingRequirementError: class scala.Array not found. at scala.tools.nsc.symtab.Definitions$definitions$.getModuleOrClass(Definitions.scala:516) at scala.tools.nsc.symtab.Definitions$definitions$.getClass(Definitions.scala:474) at scala.tools.nsc.symtab.Definitions$definitions$.ArrayClass(Definitions.scala:217) at scala.tools.nsc.backend.icode.TypeKinds$REFERENCE.(TypeKinds.scala:258) at scala.tools.nsc.backend.icode.GenICode$ICodePhase.(GenICode.scala:55) at scala.tools.nsc.backend.icode.GenICode.newPhase(GenICode.scala:43) at scala.tools.nsc.backend.icode.GenICode.newPhase(GenICode.scala:25) at scala.tools.nsc.Global$Run$$anonfun$4.apply(Global.scala:606) at scala.tools.nsc.Global$Run$$anonfun$4.apply(Global.scala:605) at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:62) at scala.collection.immutable.List.foreach(List.scala:46) at scala.tools.nsc.Global$Run.(Global.scala:605) at scala.tools.nsc.interactive.Global$TyperRun.(Global.scala:473) at scala.tools.nsc.interactive.Global.newTyperRun(Global.scala:535) at scala.tools.nsc.interactive.Global.reloadSources(Global.scala:289) at scala.tools.nsc.interactive.Global.typedTreeAt(Global.scala:309) at scala.tools.nsc.interactive.Global$$anonfun$getTypedTreeAt$1.apply(Global.scala:326) at scala.tools.nsc.interactive.Global$$anonfun$getTypedTreeAt$1.apply(Global.scala:326) at scala.tools.nsc.interactive.Global.respond(Global.scala:276) at scala.tools.nsc.interactive.Global.getTypedTreeAt(Global.scala:326) at scala.tools.nsc.interactive.CompilerControl$$anon$2.apply$mcV$sp(CompilerControl.scala:89) at scala.tools.nsc.interactive.Global.pollForWork(Global.scala:132) at scala.tools.nsc.interactive.Global$$anon$2.run(Global.scala:192) Also none of the type identification works for me, I get 'NA' if I get anything at all. C-c t causes emacs to lock up. I'm running: Ubuntu 10.04 (64bit version) emacs 23.1.50.1 ensime from git (as of 3 May 2010) scala is version 2.8.0.RC1 java is 1.6.0_20 (from sun) here is a copy of the log: http://dl.dropbox.com/u/5309017/ensime.log Thanks! Jeff

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  • Looping through an array and calling a function on each pass in v-basic / asp classic

    - by Sam
    How do I loop through an array and call a function on each pass? At the minute I'm trying the following... if Request.Form("authorize") <> "" then dim post_ids, ids post_ids = Request.form("authorize") ids = split(post_ids, ",") For i = LBound(ids) to UBound(ids) set updater = myFunction("comment_id=" & ids(i)) Next end if I'm getting the following error... Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another.

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  • ksh: assigning function output to an array

    - by rcarson
    Why doesn't this work??? #!/bin/ksh # array testfunc() function testfunc { typeset -A env env=( one="motherload" ) print -r $env return 0 } testfunc # returns: ( one=motherload ) typeset -A testvar # segfaults on linux, memfaults on solaris testvar=$(testfunc) # segfaults on linux, memfaults on solaris print -r $testvar I am sure this has been asked before, but I am not sure what to search on and everything I have been trying to use for keywords is not bringing me any answers that relate to my problem.

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  • Element was not expected While Deserializing an Array with XML Serialization

    - by Anthony Shaw
    OK. I'm trying to work on communicating with the Pivotal Tracker API, which only returns data in an XML format. I have the following XML that I'm trying to deserialize into my domain model. <?xml version="1.0" encoding="UTF-8"? <stories type="array" count="2" total="2" <story <id type="integer"2909137</id <project_id type="integer"68153</project_id <story_typebug</story_type <urlhttp://www.pivotaltracker.com/story/show/2909137</url <current_stateunscheduled</current_state <description</description <nameTest #2</name <requested_byAnthony Shaw</requested_by <created_at type="datetime"2010/03/23 20:05:58 EDT</created_at <updated_at type="datetime"2010/03/23 20:05:58 EDT</updated_at </story <story <id type="integer"2909135</id <project_id type="integer"68153</project_id <story_typefeature</story_type <urlhttp://www.pivotaltracker.com/story/show/2909135</url <estimate type="integer"-1</estimate <current_stateunscheduled</current_state <description</description <nameTest #1</name <requested_byAnthony Shaw</requested_by <created_at type="datetime"2010/03/23 20:05:53 EDT</created_at <updated_at type="datetime"2010/03/23 20:05:53 EDT</updated_at </story </stories My 'story' object is created as follows: public class story { public int id { get; set; } public int estimate { get; set; } public int project_id { get; set; } public string story_type { get; set; } public string url { get; set; } public string current_state { get; set; } public string description { get; set; } public string name { get; set; } public string requested_by { get; set; } public string labels { get; set; } public string lighthouse_id { get; set; } public string lighthouse_url { get; set; } public string owned_by { get; set; } public string accepted_at { get; set; } public string created_at { get; set; } public attachment[] attachments { get; set; } public note[] notes { get; set; } } When I execute my deserialization code, I receive the following exception: Exception: There is an error in XML document (2, 2). Inner Exception: <stories xmlns='' was not expected. I can deserialize the individual stories just fine, I just cannot deserialize this xml into an array of 'story' objects And my deserialization code (value is a string of the xml) var byteArray = Encoding.ASCII.GetBytes(value); var stream = new MemoryStream(byteArray); var deserializedObject = new XmlSerializer(typeof (story[])).Deserialize(stream) Does anybody have any ideas?

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  • django templates array assignment

    - by Hulk
    The following is in views: rows=query.evaluation_set.all() row_arr = [] for row in rows: row_arr.append(row.row_details) dict.update({'row_arr' : row_arr ,'col_arr' : col_arr}) return render_to_response('valuemart/show.html',context_instance=RequestContext(request,{'dict': dict})) How to extract the row_Arr array in the templates in javascript and list out all its values.row_Arr contains data of a column <script> var row_arr = '{{dict.row_arr}}'; //extract values here </script> Thanks..

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  • JSON array deserialization is crashing the Dalvik VM

    - by Sam
    I have some code grabbing a JSON array from my server and initially storing it as a string. This all works fine until I try and deserialize it using google's gson fromJson method. LogCat spits out the error: 04-08 17:46:35.163: ERROR/dalvikvm(401): Can't shrink stack: curFrame is in reserved area (0x41049000 0x410491c4) My code that causes the error is: String[] results = gson.fromJson(returnString, String[].class); Can anyone shed some light on what I am doing wrong? Cheers, Sam

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  • How Can I Use This jSON data like array

    - by mTuran
    hi, i have json data like this: {"Adobe Photoshop":"70","Adobe Premier":"71","Animasyon":"72","AutoCAD":"73","Bro\u015f\u00fcr & Bilet":"75","CorelDraw":"76","Flash":"77","Grafik Tasar\u0131m":"68","Karikat\u00fcr":"78","Kartvizit Tasar\u0131m":"79","Logo Tasar\u0131m":"80","Poster":"81","Reklam Tasar\u0131m":"74","Ses D\u00fczenleme":"82","Video D\u00fczenleme":"69","Web Tasar\u0131m":"83"} First think(Adobe Photoshop) means tag name, second thing(70) means tag id. I want to use this information in jquery like array to build checkboxes for every tag. How can i done this ? Thanks

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  • Trie VS Suffix Tree VS Suffix Array

    - by ukrania
    Hello everyone, Which one is the structure that provides best performance results? Trie, Suffix Tree or Suffix Array? There are other equivalent structures? What are good Java implementations of these structures? Thanks for your answers. Best Regards, ukrania

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  • Cocoa @sum array operator too slow - alternatives?

    - by icodestuff
    I've got a text field value bound to a key path that uses @sum. When the array controller is filtered, the text field updates properly, but extremely slowly, lagging the UI or outright beachballing after every key press (less so as the number of items in arrangedObjects decreases). There is no lag if I don't use @sum; I've narrowed it down to this. Is there a faster way to do the same thing?

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  • Sax Parser Character Array to Integer??

    - by Andy Barlow
    Hello, I am trying to get the contents of tags into variables in my java Sax parser. However, the Characters method only returns Char arrays. Is there anyway to get the Char array into an Int??? public void characters(char ch[], int start, int length) { if(this.in_total_results) { // my INT varialble would be nice here! } } Can anyone help at all? Kind regards, Andy

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  • Converting a md5 hash byte array to a string

    - by Blankman
    How can I convert the hashed result, which a byte array, to a string? byte[] bytePassword = Encoding.UTF8.GetBytes(password); using (MD5 md5 = MD5.Create()) { byte[] byteHashedPassword = md5.ComputeHash(bytePassword); } So I need to convert byteHashedPassword to a string

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  • Converting a int to a BCD byte array

    - by Lily
    I want to convert an int to a byte[2] array using BCD. The int in question will come from DateTime representing the Year and must be converted to two bytes. Is there any pre-made function that does this or can you give me a simple way of doing this? example: int year = 2010 would output: byte[2]{0x20, 0x10};

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  • hash of array in objective-c, how?

    - by Horace Ho
    How is a hash of integer array can be represented in objective-c? Here is the ruby hash as an example: hi_scores = { "John" => [1, 1000], "Mary" => [2, 8000], "Bob" => [5, 2000] } such that can be accessed by: puts hi_scores["Mary"][1] => 8000 hopefully easy to serialize too. Thanks!

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  • How would i access the properties in this object? Twitter API

    - by Tapha
    I have stores this object in an variable called results. How would i access the profile_image_url for example. Here is the return value with print_r: stdClass Object ( [results] => Array ( [0] => stdClass Object ( [profile_image_url] => http://a3.twimg.com/profile_images/685278639/twitter-logo_normal.jpg [created_at] => Mon, 10 May 2010 11:29:44 +0000 [from_user] => BarclaysWealth [metadata] => stdClass Object ( [result_type] => recent ) [to_user_id] => [text] => RT @BarclaysStock: Investment ViewPoint - We take a look at what a hung parliament could mean for the UK economy http://bit.ly/OaYh7 [id] => 13721505359 [from_user_id] => 14895786 [geo] => [iso_language_code] => en [source] => <a href="http://twitter.com/">web</a> ) [1] => stdClass Object ( [profile_image_url] => http://a1.twimg.com/profile_images/671523082/32fb0a8_normal.jpg [created_at] => Fri, 07 May 2010 21:02:10 +0000 [from_user] => InfoFocus [metadata] => stdClass Object ( [result_type] => recent ) [to_user_id] => [text] => RT @BarclaysWealth: RT @BarclaysStock: Investment ViewPoint - We take a look at what a hung parliament could mean for the UK economy http://bit.ly/OaYh7 [id] => 13569384857 [from_user_id] => 85742792 [geo] => [iso_language_code] => en [source] => <a href="http://www.hootsuite.com" rel="nofollow">HootSuite</a> ) [2] => stdClass Object ( [profile_image_url] => http://a3.twimg.com/profile_images/685278639/twitter-logo_normal.jpg [created_at] => Fri, 07 May 2010 20:59:20 +0000 [from_user] => BarclaysWealth [metadata] => stdClass Object ( [result_type] => recent ) [to_user_id] => [text] => RT @BarclaysStock: Investment ViewPoint - We take a look at what a hung parliament could mean for the UK economy http://bit.ly/OaYh7 [id] => 13569257933 [from_user_id] => 14895786 [geo] => [iso_language_code] => en [source] => <a href="http://www.hootsuite.com" rel="nofollow">HootSuite</a> ) [3] => stdClass Object ( [profile_image_url] => http://a1.twimg.com/profile_images/485934856/BD_Icon_Twitter_small_normal.gif [created_at] => Fri, 07 May 2010 16:35:56 +0000 [from_user] => BARXdirect [metadata] => stdClass Object ( [result_type] => recent ) [to_user_id] => [text] => RT @BarclaysStock: Investment ViewPoint - We take a look at what a hung parliament could mean for the UK economy http://bit.ly/OaYh7 [id] => 13557670463 [from_user_id] => 66715243 [geo] => [iso_language_code] => en [source] => <a href="http://twitter.com/">web</a> ) [4] => stdClass Object ( [profile_image_url] => http://a1.twimg.com/profile_images/431590520/BSL_icon_normal.gif [created_at] => Fri, 07 May 2010 16:35:12 +0000 [from_user] => BarclaysStock [metadata] => stdClass Object ( [result_type] => recent ) [to_user_id] => [text] => Investment ViewPoint - We take a look at what a hung parliament could mean for the UK economy http://bit.ly/OaYh7 [id] => 13557633799 [from_user_id] => 36238006 [geo] => [iso_language_code] => en [source] => <a href="http://twitter.com/">web</a> ) ) [max_id] => 13722716932 [since_id] => 0 [refresh_url] => ?since_id=13722716932&q=http%3A%2F%2Fbit.ly%2FOaYh7 [results_per_page] => 15 [page] => 1 [completed_in] => 0.026887 [query] => http%3A%2F%2Fbit.ly%2FOaYh7 )

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