explain - Page 233 - Developer IT

How can I store this kind of graph in neo4j for fast traversal?

- by James

This is a graph whose nodes exist in many connected components at once because a node's relationships are a collection of edge groups such that only one edge per edge group can be present at once. I need to be able to find all of the connected components that a node exists in. What would be the best way to store this graph in neo4j to quickly find all of the connected components that a node exists in? Is there a way to use the built in traversals to do this? Also: is there a name for this kind of graph? I'd appreciate any help/ideas. Update: Sorry for not being clear. All nodes are of the same type. Nodes have a variable number of edge groups. Exactly one edge from each edge group needs to be chosen for a particular connected component. I'm going to try to explain through example: Node x1 is related to: (x2 or x3 or x4) AND (x5 or x6) AND (x7) Node x2 is related to: (x8) AND (x9 or x10) So x1's first edge group is (x2, x3, x4), its second edge group is (x5, x6), and its third edge group is (x7). So here are a few connected components that x1 exists in: CC1: x1 is related to: x2, x5, x7 x2 is related to: x8 x9 CC2: x1 is related to: x2, x6, x7 x2 is related to: x8, x9 CC3: x1 is related to: x3, x5, x7 CC4: x1 is related to: x3, x6, x7 etc. I'm grateful for your help in this.

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MySQL - What is wrong with this query or my database? Terrible performance.

- by Moss

SELECT * from `employees` a LEFT JOIN (SELECT phone1 p1, count(*) c, FROM `employees` GROUP BY phone1) b ON a.phone1 = b.p1; I'm not sure if it is this query in particular that has the problem. I have been getting terrible performance in general with this database. The table in question has 120,000 rows. I have tried this particular query remotely and locally with the MyISAM and InnoDB engines, with different types of joins, and with and without an index on phone1. I can get this to complete in about 4 minutes on a 10,000 row table successfully but performance drops exponentially with larger tables. Remotely it will lose connection to the server and locally it brings my system to its knees and seems to go on forever. This query is only a smaller step I was trying to do when a larger query couldn't complete. Maybe I should explain the whole scenario. I have one big flat ugly table that lists a bunch of people and their contact info and the info of the companies they work for. I'm trying to normalize the database and intelligently determine which phone numbers apply to individual people and which apply to an office location. My reasoning is that if a phone number occurs multiple times and the number of occurrence equals the number of times that the street address it is attached to occurs then it must be an office number. So the first step is to count each phone number grouping by phone number. Normally if you just use COUNT()...GROUP BY it will only list the first record it finds in that group so I figured I have to join the full table to the count table where the phone number matches. This does work but as I said I can't successfully complete it on any table much larger than 10,000 rows. This seems pathetic and this doesn't seem like a crazy query to do. Is there a better way to achieve what I want or do I have to break my large table into 12 pieces or is there something wrong with the table or db?

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Call to a member function get_segment() error

- by hogofwar

I'm having this problem with this piece of PHP code: class Core { public function start() { require("funk/funks/libraries/uri.php"); $this->uri = new uri(); require("funk/core/loader.php"); $this->load = new loader(); if($this->uri->get_segment(1) != "" and file_exists("funk/pages/".$uri->get_segment(1).".php")){ Only a snippet of the code The best way I can explain it is that it is a class calling upon another class (uri.php) and i am getting the error: Fatal error: Call to a member function get_segment() on a non-object in /home/eeeee/public_html/private/funkyphp/funk/core/core.php on line 11 (the if($this-uri-get_segment(1) part) I'm having this problem a lot and it is really bugging me. the library code is: <?php class uri { private $server_path_info = ''; private $segment = array(); private $segments = 0; public function __construct() { $segment_temp = array(); $this->server_path_info = preg_replace("/\?/", "", $_SERVER["PATH_INFO"]); $segment_temp = explode("/", $this->server_path_info); foreach ($segment_temp as $key => $seg) { if (!preg_match("/([a-zA-Z0-9\.\_\-]+)/", $seg) || empty($seg)) unset($segment_temp[$key]); } foreach ($segment_temp as $k => $value) { $this->segment[] = $value; } unset($segment_temp); $this->segments = count($this->segment); } public function segment_exists($id = 0) { $id = (int)$id; if (isset($this->segment[$id])) return true; else return false; } public function get_segment($id = 0) { $id--; $id = (int)$id; if ($this->segment_exists($id) === true) return $this->segment[$id]; else return false; } } ?>

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Can I create an application using SlimDX relying on the DirectX DLLs already bundled with Vista/Win7

- by norheim.se

I'm working on a .NET application that requires the use of accelerated graphics, currently DirectX 9.0c. The software is quite graphics intensive and must, in addition, be launchable from a CD or by ClickOnce without the user requiring administrator's permissions. I currently use SlimDX, which works great featurewise, but the users are getting rather annoyed by having to install the DirectX redistributable. Especially since this does require elevated permissions. It is rather hard to explain to them why the version of DirectX already bundled with their OS is not sufficient. After all - DirectX 9.0c has been around since 2004, and I'm not using any new fancy features. The ability to deliver an application that "just works" in Vista or Windows 7, without any particular additional prerequisites would be a huge advantage. Therefore: Is there any way I can build an application using DirectX 9.0c based on SlimDX, that relies only on the libraries provided in the standard Windows Vista/Win7 installation? That is - without requiring the additional DirectX redistributable to be installed? If not - is there any other managed (and preferably not abandoned) DirectX wrapper that can serve this purpose? Thanks in advance!

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IE8: weird border around HTML button element

- by s427

I have a button element with a custom background (image+color) and no borders except for a 2px border-bottom (and a bunch of other properties --code below) which renders quite differently in Firefox and in IE8. The problem is, this is a work for a company that uses IE8 as their only browser, so it's important that the button renders well in IE8. Here's a visual comparison between the two: My question here is not about the padding difference (I'm looking into that), but about the weird border that is visible on IE8 in addition to the regular border (border-bottom). Can anyone explain to me where it comes from and how to get rid of it? Thanks in advance. Here is the HTML code: <button class="btn" id="c_edit"> <span>Annuler</span> </button> And here is the CSS: .btn { display: inline-block; margin: 0 0 7px 5px; padding: 0; color: #ddd; font-size: 14px; font-family: FrutigerLTStd55Roman, sans-serif; text-decoration: none; border: none; border-bottom: 2px solid #222; background-color: #999; background-image: url('img/btn_bg.gif'); background-position: 0 bottom; background-repeat: repeat-x; cursor: pointer; transition: all .5s ease-out; } .btn span { display: inline-block; margin: 0; padding: 8px 10px 6px 40px; background-color: transparent; background-position: 4px 0; background-repeat: no-repeat; }

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Multiple exports with MEF does some really heinous stuff -- why, and why is it allowed?

- by Dave

I have an interesting situation where I need to do something like this: [Export[typeof(ICandy1)] [Export[typeof(ICandy2)] public class Candy : ICandy2 { ... } where public interface ICandy1 { ... } public interface ICandy2 : ICandy1 { ... } I couldn't find any posts anywhere regarding using multiple [Export] attributes, so I figured, what the hell, might as well try it. At first glance, it actually seemed to work. I have a couple of methods that call into both interfaces of a Candy instance, and it was fine. However, as I started to test the app, I saw that the behavior wasn't right, and when looking at the Output window, I saw that I was getting tons of COMExceptions. I couldn't track down where they were all coming from, but they always occurred when a worker thread was sleeping. I figured that it had to be from the main thread, then, but didn't know how to debug this at all. Nothing should have been going on in the GUI, and I disabled my DispatchTimers just in case -- same thing. Even more strange than the COMExceptions was the really, really erratic behavior when stepping through code. About 30% of the time, when I single stepped, it would pop out of the method, or it would single step over two lines of code! Totally weird stuff that I am not used to seeing. The only thing that changed between working and non-working code was the introduction of MEF through my plugin loading code. So as a test, I changed my plugin assembly to only export one interface, and I hardcoded everything in the app that relied on the other (now not-implemented) interface. And now the COMExceptions are gone, and the weird debugging behavior is gone. Is this something people here have seen before? If MEF is not expected to allow a class to Export multiple interfaces, then shouldn't a CompositionException get raised when composing the parts? Can anyone explain why MEF would cause these weird problems???

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Constructor on type: "Namespace.type" not found.

- by Nick

Hello, I am using Castle.Windsor as an IOC. So I am trying to resolve a service type in the constructor of an HTTPHandler. I keep receiving this error, "Constructor on type: "Namespace.type" not found." My configuration has the following entries for service type: IDocumentDirectory <component id="restricted.content.directory" service="org.healthwise.foundations.services.content.IDocumentDirectory, org.healthwise.foundations.services" type="org.healthwise.foundations.services.content.RestrictedLocalizationDocumentDirectory, org.healthwise.foundations.services"> <parameters> <contentDirectory>${content.directory}</contentDirectory> <localizations> <array> <item>en-us</item> <item>es-us</item> </array> </localizations> </parameters> </component> <component id="content.directory" service="org.healthwise.foundations.services.content.IDocumentDirectory, org.healthwise.foundations.services" type="org.healthwise.foundations.services.web.client.WebServiceDocumentDirectory, org.healthwise.foundations.services.web.client"> <parameters> <webServiceURL>#{contentDirectoryWebsiteUrl}</webServiceURL> </parameters> </component> In my new handler the constructor looks like this: public HeartBeatHttpHandler(IDocumentDirectory contentDirectory) { _contentDirectory = contentDirectory; } I have never recieved this error using Castle.Windsor. Can someone explain? Thanks!

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Eliminate full table scan due to BETWEEN (and GROUP BY)

- by Dave Jarvis

Description According to the explain command, there is a range that is causing a query to perform a full table scan (160k rows). How do I keep the range condition and reduce the scanning? I expect the culprit to be: Y.YEAR BETWEEN 1900 AND 2009 AND Code Here is the code that has the range condition (the STATION_DISTRICT is likely superfluous). SELECT COUNT(1) as MEASUREMENTS, AVG(D.AMOUNT) as AMOUNT, Y.YEAR as YEAR, MAKEDATE(Y.YEAR,1) as AMOUNT_DATE FROM CITY C, STATION S, STATION_DISTRICT SD, YEAR_REF Y FORCE INDEX(YEAR_IDX), MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 10663 AND -- Find all the stations within a specific unit radius ... -- 6371.009 * SQRT( POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) + (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) * POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= 50 AND -- Get the station district identification for the matching station. -- S.STATION_DISTRICT_ID = SD.ID AND -- Gather all known years for that station ... -- Y.STATION_DISTRICT_ID = SD.ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '003' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR Update The SQL is performing a full table scan, which results in MySQL performing a "copy to tmp table", as shown here: +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ | 1 | SIMPLE | C | const | PRIMARY | PRIMARY | 4 | const | 1 | | | 1 | SIMPLE | Y | range | YEAR_IDX | YEAR_IDX | 4 | NULL | 160422 | Using where | | 1 | SIMPLE | SD | eq_ref | PRIMARY | PRIMARY | 4 | climate.Y.STATION_DISTRICT_ID | 1 | Using index | | 1 | SIMPLE | S | eq_ref | PRIMARY | PRIMARY | 4 | climate.SD.ID | 1 | Using where | | 1 | SIMPLE | M | ref | PRIMARY,YEAR_REF_IDX,CATEGORY_IDX | YEAR_REF_IDX | 8 | climate.Y.ID | 54 | Using where | | 1 | SIMPLE | D | ref | INDEX | INDEX | 8 | climate.M.ID | 11 | Using where | +----+-------------+-------+--------+-----------------------------------+--------------+---------+-------------------------------+--------+-------------+ Related http://dev.mysql.com/doc/refman/5.0/en/how-to-avoid-table-scan.html http://dev.mysql.com/doc/refman/5.0/en/where-optimizations.html http://stackoverflow.com/questions/557425/optimize-sql-that-uses-between-clause Thank you!

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Currently using View, Should I use a hard table instead?

- by 1001010101

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Loading views dynamically

- by Dan

Case 1: I have created View-based sample application and tried execute below code. When I press on "Job List" button it should load another view having "Back Btn" on it. In test function, if I use [self.navigationController pushViewController:jbc animated:YES]; nothing gets loaded, but if I use [self presentModalViewController:jbc animated:YES]; it loads another view haveing "Back Btn" on it. Case 2: I did create another Navigation Based Applicaton and used [self.navigationController pushViewController:jbc animated:YES]; it worked as I wanted. Can someone please explain why it was not working in Case 1. Does it has something to do with type of project that is selected? @interface MWViewController : UIViewController { } -(void) test; @end @interface JobViewCtrl : UIViewController { } @end @implementation MWViewController (void)viewDidLoad { UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn.frame = CGRectMake(80, 170, 150, 35); [btn setTitle:@"Job List!" forState:UIControlStateNormal]; [btn addTarget:self action:@selector(test) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:btn]; [super viewDidLoad]; } -(void) test { JobViewCtrl* jbc = [[JobViewCtrl alloc] init]; [self.navigationController pushViewController:jbc animated:YES]; //[self presentModalViewController:jbc animated:YES]; [jbc release]; } (void)dealloc { [super dealloc]; } @end @implementation JobViewCtrl -(void) loadView { self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; self.view.backgroundColor = [UIColor grayColor]; UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn.frame = CGRectMake(80, 170, 150, 35); [btn setTitle:@"Back Btn!" forState:UIControlStateNormal]; [self.view addSubview:btn]; } @end

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Hide All But First Matching Element

- by Batfan

I am using jquery to sort through multiple paragraphs. Currently I have it set to show only paragraphs that start with a current letter. But now, I would like to consolidate further. If the text between the paragraph tags has multiple instances, I would like all but the first hidden. This is what I have so far but, it is not working. var letter = '<?php echo(strlen($_GET['letter']) == 1) ? $_GET['letter'] : ''; ?>' function finish(){ jQuery('p').each(function(){ if(jQuery(this).text().substr(0,1).toUpperCase() == letter){ jQuery(this).addClass('current-series'); jQuery(this).html(letter + '<span class="hidden">'+jQuery(this).text().slice(1)+ '</span>'); } else{ jQuery(this).hide();} }) } Update: Sorry guys, I know this is kind of hard to explain. Here's a basic example: The selected letter is B The values returned are: Ball Ball Ball Boy Brain Bat Bat Each of these values is in a paragraph tag. Is there a way to consolidate to this? Ball Boy Brain Bat

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which one of these is an example of coercion

- by user1890210

I have been pondering a multiple choice question on coercion. One of the 4 examples a,b,c or d is an example of coercion. I narrowed it down to A or B. But I am having a problem choosing between the two. Cane someone please explain why one is coercion and one isn't. A) string s="tomat"; char c='o'; s=s+c; I thought A could be correct because we have two different types, character and string, being added. Meaning that c is promoted to string, hence coercion. B) double x=1.0; double y=2.0; int i=(int)(x+y); I also thought B was the correct answer because the double (x+y) is being turned into a int to be placed in i. But I thought this could be wrong because its being done actively through use of (int) rather than passively such as "int i = x + y" I'll list the other two options, even though I believe that neither one is the correct answer C) char A=0x20; A = A << 1 | 0x01; cout << A << endl; D) double x=1.0; double y=x+1; return 0; I'm not just looking for an answer, but an explanation. I have read tons of things on coercion and A and B both look like the right answer. So why is one correct and the other not.

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Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

- by Lambert

The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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ASP.Net MVC TDD using Moq

- by Nicholas Murray

I am trying to learn TDD/BDD using NUnit and Moq. The design that I have been following passes a DataService class to my controller to provide access to repositories. I would like to Mock the DataService class to allow testing of the controllers. There are lots of examples of mocking a repository passed to the controller but I can't work out how to mock a DataService class in this scenerio. Could someone please explain how to implement this? Here's a sample of the relevant code: [Test] public void Can_View_A_Single_Page_Of_Lists() { var dataService = new Mock<DataService>(); var controller = new ListsController(dataService); ... } namespace Services { public class DataService { private readonly IKeyedRepository<int, FavList> FavListRepository; private readonly IUnitOfWork unitOfWork; public FavListService FavLists { get; private set; } public DataService(IKeyedRepository<int, FavList> FavListRepository, IUnitOfWork unitOfWork) { this.FavListRepository = FavListRepository; this.unitOfWork = unitOfWork; FavLists = new FavListService(FavListRepository); } public void Commit() { unitOfWork.Commit(); } } } namespace MyListsWebsite.Controllers { public class ListsController : Controller { private readonly DataService dataService; public ListsController(DataService dataService) { this.dataService = dataService; } public ActionResult Index() { var myLists = dataService.FavLists.All().ToList(); return View(myLists); } } }

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Can someone recommend a good tutorial on MySQL indexes, specifically when used in an order by clause

- by Philip Brocoum

I could try to post and explain the exact query I'm trying to run, but I'm going by the old adage of, "give a man a fish and he'll eat for a day, teach a man to fish and he'll eat for the rest of his life." SQL optimization seems to be very query-specific, and even if you could solve this one particular query for me, I'm going to have to write many more queries in the future, and I'd like to be educated on how indexes work in general. Still, here's a quick description of my current problem. I have a query that joins three tables and runs in 0.2 seconds flat. Awesome. I add an "order by" clause and it runs in 4 minutes and 30 seconds. Sucky. I denormalize one table so there is one fewer join, add indexes everywhere, and now the query runs in... 20 minutes. What the hell? Finally, I don't use a join at all, but rather a subquery with "where id in (...) order by" and now it runs in 1.5 seconds. Pretty decent. What in God's name is going on? I feel like if I actually understood what indexes were doing I could write some really good SQL. Anybody know some good tutorials? Thanks!

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Deleting elements from stl set while iterating through it does not invalidate the iterators.

- by pedromanoel

I need to go through a set and remove elements that meet a predefined criteria. This is the test code I wrote: #include <set> #include <algorithm> void printElement(int value) { std::cout << value << " "; } int main() { int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; std::set<int> numbers(initNum, initNum + 10); // print '0 1 2 3 4 5 6 7 8 9' std::for_each(numbers.begin(), numbers.end(), printElement); std::set<int>::iterator it = numbers.begin(); // iterate through the set and erase all even numbers for (; it != numbers.end(); ++it) { int n = *it; if (n % 2 == 0) { // wouldn't invalidate the iterator? numbers.erase(it); } } // print '1 3 5 7 9' std::for_each(numbers.begin(), numbers.end(), printElement); return 0; } At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can't explain why. My question: Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way. Thanks!

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Application Code Redesign to reduce no. of Database Hits from Performance Perspective

- by Rachel

Scenario I want to parse a large CSV file and inserts data into the database, csv file has approximately 100K rows of data. Currently I am using fgetcsv to parse through the file row by row and insert data into Database and so right now I am hitting database for each line of data present in csv file so currently database hit count is 100K which is not good from performance point of view. Current Code: public function initiateInserts() { //Open Large CSV File(min 100K rows) for parsing. $this->fin = fopen($file,'r') or die('Cannot open file'); //Parsing Large CSV file to get data and initiate insertion into schema. while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $query = "INSERT INTO dt_table (id, code, connectid, connectcode) VALUES (:id, :code, :connectid, :connectcode)"; $stmt = $this->prepare($query); // Then, for each line : bind the parameters $stmt->bindValue(':id', $data[0], PDO::PARAM_INT); $stmt->bindValue(':code', $data[1], PDO::PARAM_INT); $stmt->bindValue(':connectid', $data[2], PDO::PARAM_INT); $stmt->bindValue(':connectcode', $data[3], PDO::PARAM_INT); // Execute the statement $stmt->execute(); $this->checkForErrors($stmt); } } I am looking for a way wherein instead of hitting Database for every row of data, I can prepare the query and than hit it once and populate Database with the inserts. Any Suggestions !!! Note: This is the exact sample code that I am using but CSV file has more no. of field and not only id, code, connectid and connectcode but I wanted to make sure that I am able to explain the logic and so have used this sample code here. Thanks !!!

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Javascript, IE, Strings, and Performance problems

- by Infinity

Hey guys, So we have this product, and it's really slow in IE. We've already applied a lot of the practices advised by the IE guys themselves (like this, and this), and try to sacrifice clean code for performance in the critical parts like DOM manipulation. However, as you can see in this IE profiler screenshot.. Just "String" is the biggest offender. Almost 750ms of exclusive time. Does this mean IE is spending 750ms just instantiating Strings? I also read this stuff on the Opera dev blog: A build script can remove whitespace, comments, replace strings with Array lookups (to avoid MSIE creating a string object for every single instance of a string — even in conditions) But no more info regarding this. Anyone can clarify? It seems like IE has to create a full String instance every time you have " " in your code, which could explain this, but I don't know what the array lookup optimization would look like. BTW- we don't really do much of string concatenation anywhere in the code. The library we use is MooTools 1.2.4 Any suggestions will be appreciated! Thx

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emacs: How to intelligently handle buffer-modified when setting text properties?

- by Cheeso

The documentation on Text Properties says: Since text properties are considered part of the contents of the buffer (or string), and can affect how a buffer looks on the screen, any change in buffer text properties marks the buffer as modified. First, I don't understand that policy. Can anyone explain? The text props are not actually saved in the file, when the buffer is saved. So why mark the buffer as modified? For me, buffer-modified indicates "some changes have not yet been saved." but understanding the policy is just for my own amusement. More importantly, is there an already-established way that, in code, I can change syntax text properties on the text in a buffer, while keeping the buffer-modified flag set to whatever it was, prior to those changes? I'm thinking of something like save-excursion. It would be pretty easy to write, but this seems like a common case and I'd like to use the standard function, if possible. For more on the scenario - I have a mode that does a full text scan and sets syntax-tabe properties on the text. After opening a buffer, the scan runs, but it results in a buffer with buffer-modified set to t . As always, thanks.

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java - question about thread abortion and deadlock - volatile keyword

- by Tiyoal

Hello all, I am having some troubles to understand how I have to stop a running thread. I'll try to explain it by example. Assume the following class: public class MyThread extends Thread { protected volatile boolean running = true; public void run() { while (running) { synchronized (someObject) { while (someObject.someCondition() == false && running) { try { someObject.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } // do something useful with someObject } } } public void halt() { running = false; interrupt(); } } Assume the thread is running and the following statement is evaluated to true: while (someObject.someCondition() == false && running) Then, another thread calls MyThread.halt(). Eventhough this function sets 'running' to false (which is a volatile boolean) and interrupts the thread, the following statement is still executed: someObject.wait(); We have a deadlock. The thread will never be halted. Then I came up with this, but I am not sure if it is correct: public class MyThread extends Thread { protected volatile boolean running = true; public void run() { while (running) { synchronized (someObject) { while (someObject.someCondition() == false && running) { try { someObject.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } // do something useful with someObject } } } public void halt() { running = false; synchronized(someObject) { interrupt(); } } } Is this correct? Is this the most common way to do this? This seems like an obvious question, but I fail to come up with a solution. Thanks a lot for your help.

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What's the correct way to pass parameters from VBScript to COM interface implemented in C#?

- by nopopem

I'm trying to expose a fairly simple C# class to COM which should be usable from VBScript (among others). Some objects need to be created via COM calls and will be used in furter calls later on. The definition of the exposed classes and interfaces looks like this: namespace Test { [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IComInterface { IFoo CreateFoo(); void UseFoo(int x, IFoo f); } [ClassInterface(ClassInterfaceType.None)] public sealed class CComInterface : IComInterface { public CComInterface() {} public IFoo CreateFoo() { return new Foo(); } public void UseFoo(int x, IFoo f) { f.Bar(); } } [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IFoo { void Bar(); } [ClassInterface(ClassInterfaceType.None)] public class Foo : IFoo { internal Foo() {} public void Bar() {} } } The simplest thinkable COM client in VBScript does this: Dim ci Set ci = WScript.CreateObject("Test.CComInterface") Dim foo Set foo = ci.CreateFoo foo.Bar ci.UseFoo 0, foo While the call to Bar succeeds, calling UseFoo fails with "Error 5: invalid procedure call or invalid argument" The generated IDL seems ok to me: dispinterface IComInterface { properties: methods: [id(0x60020003)] IFoo* CreateFoo(); [id(0x60020004)] void UseFoo( [in] long x, [in] IFoo* f); }; The vbs call succeeds when I wrap the second parameter in parentheses like this: ci.UseFoo 0, (foo) As far as I understand (I'm no VBScript expert however) this forces the reference to foo to be passed by value, i.e. a copy of the reference is being made. How can I change the interface so that it can be called with the foo reference directly? Since this will be a public interface used by customers I don't like the idea of having to explain why all the objects created need to be passed back in an extra pair of parentheses...

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Simple POSIX threads question

- by Andy

Hi, I have this POSIX thread: void subthread(void) { while(!quit_thread) { // do something ... // don't waste cpu cycles if(!quit_thread) usleep(500); } // free resources ... // tell main thread we're done quit_thread = FALSE; } Now I want to terminate subthread() from my main thread. I've tried the following: quit_thread = TRUE; // wait until subthread() has cleaned its resources while(quit_thread); But it does not work! The while() clause does never exit although my subthread clearly sets quit_thread to FALSE after having freed its resources! If I modify my shutdown code like this: quit_thread = TRUE; // wait until subthread() has cleaned its resources while(quit_thread) usleep(10); Then everything is working fine! Could someone explain to me why the first solution does not work and why the version with usleep(10) suddenly works? I know that this is not a pretty solution. I could use semaphores/signals for this but I'd like to learn something about multithreading, so I'd like to know why my first solution doesn't work. Thanks!

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Android import project errors

- by Jsmith102

Hey everyone, I'm a beginner, so I'll try my best to explain this problem succinctly. Basically, a friend of mine and I were playing around with the Android SDK, editing a simple RSS reader. We could launch it in the emulator and even install it on our real devices. Fast forward a few days, I'm trying to import the exact same code that was working a few days earlier into Eclipse on my laptop. I tried both importing and new project from existing source. Both return these new errors that we never had originally. I got an error that involved the auto generated "R" file, but I have solved this. Now, I'm getting 3 errors that I have never had before - The method onClick(View) of type new View.OnClickListener(){} must override a superclass method - displayed twice ( 2 different lines) The method onTabChanged(String) of type new TabHost.OnTabChangeListener(){} must override a superclass method My question is this - What would cause the these discrepancies between importing/running on my friends computer and mine? Also, we are both using the latest version of Java/Eclipse Thanks in advance for any insight.

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JSF h:outputStylesheet doesn't work everywhere

- by s3rius

I'm currently learning Icefaces, now I'm trying to integrate a css file via h:OutputStylesheet into my code. I have a main page and a second page. Using outputStylesheet in my main page works well (and then I can also access the css in the second page, which I guess is intended). But when I try to integrate it in my second page it doesn't work at all. The code for both pages is basically identical. main page: <h:head></h:head> <h:body>  <h:outputStylesheet library="css" name="style.css" />  <div class="red">This is red color in main page</div> </h:body> second page: <h:head></h:head> <h:body>  <h:outputStylesheet library="css" name="style.css" />  <div class="red">This is red color in second page</div> </h:body> I've made sure that I have h:body and h:head tags in both files. There's nothing more in the html pages except the standard doctype and xml version declarations. I've tried packing everything into h:forms, but that doesn't change anything. Can anyone explain to me what's going on?

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C++ STL Map vs Vector speed

- by sub

In the interpreter for my experimental programming language I have a symbol table. Each symbol consists of a name and a value (the value can be e.g.: of type string, int, function, etc.). At first I represented the table with a vector and iterated through the symbols checking if the given symbol name fitted. Then I though using a map, in my case map<string,symbol>, would be better than iterating through the vector all the time but: It's a bit hard to explain this part but I'll try. If a variable is retrieved the first time in a program in my language, of course its position in the symbol table has to be found (using vector now). If I would iterate through the vector every time the line gets executed (think of a loop), it would be terribly slow (as it currently is, nearly as slow as microsoft's batch). So I could use a map to retrieve the variable: SymbolTable[ myVar.Name ] But think of the following: If the variable, still using vector, is found the first time, I can store its exact integer position in the vector with it. That means: The next time it is needed, my interpreter knows that it has been "cached" and doesn't search the symbol table for it but does something like SymbolTable.at( myVar.CachedPosition ). Now my (rather hard?) question: Should I use a vector for the symbol table together with caching the position of the variable in the vector? Should I rather use a map? Why? How fast is the [] operator? Should I use something completely different?

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