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  • What is the best way to INSERT a large dataset into a MySQL database (or any database in general)

    - by Joe
    As part of a PHP project, I have to insert a row into a MySQL database. I'm obviously used to doing this, but this required inserting into 90 columns in one query. The resulting query looks horrible and monolithic (especially inserting my PHP variables as the values): INSERT INTO mytable (column1, colum2, ..., column90) VALUES ('value1', 'value2', ..., 'value90') and I'm concerned that I'm not going about this in the right way. It also took me a long (boring) time just to type everything in and testing writing the test code will be equally tedious I fear. How do professionals go about quickly writing and testing these queries? Is there a way I can speed up the process?

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  • What is an efficient algorithm for randomly assigning a pool of objects to a parent using specific rules

    - by maple_shaft
    I need some expert answers to help me determine the most efficient algorithm in this scenario. Consider the following data structures: type B { A parent; } type A { set<B> children; integer minimumChildrenAllowed; integer maximumChildrenAllowed; } I have a situation where I need to fetch all the orphan children (there could be hundreds of thousands of these) and assign them RANDOMLY to A type parents based on the following rules. At the end of the job, there should be no orphans left At the end of the job, no object A should have less children than its predesignated minimum. At the end of the job, no object A should have more children than its predesignated maximum. If we run out of A objects then we should create a new A with default values for minimum and maximum and assign remaining orphans to these objects. The distribution of children should be as evenly distributed as possible. There may already be some children assigned to A before the job starts. I was toying with how to do this but I am afraid that I would just end up looping across the parents sorted from smallest to largest, and then grab an orphan for each parent. I was wondering if there is a more efficient way to handle this?

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  • URL Encryption vs. Encoding

    - by hozza
    At the moment non/semi sensitive information is sent from one page to another via GET on our web application. Such as user ID or page number requested etc. Sometimes slightly more sensitive information is passed such as account type, user privileges etc. We currently use base64_encode() and base64_decode() just to de-humanise the information so the end user is not concerned. Is it good practice or common place for a URL GET to be encrypted rather than simply PHP base64_encoded? Perhaps using something like, this: $encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $string, MCRYPT_MODE_CBC, md5(md5($key)))); $decrypted = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($encrypted), MCRYPT_MODE_CBC, md5(md5($key))), "\0"); Is this too much or too power hungry for something as common as the URL GET.

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  • Increasing Regex Efficiency

    - by cam
    I have about 100k Outlook mail items that have about 500-600 chars per Body. I have a list of 580 keywords that must search through each body, then append the words at the bottom. I believe I've increased the efficiency of the majority of the function, but it still takes a lot of time. Even for 100 emails it takes about 4 seconds. I run two functions for each keyword list (290 keywords each list). public List<string> Keyword_Search(HtmlNode nSearch) { var wordFound = new List<string>(); foreach (string currWord in _keywordList) { bool isMatch = Regex.IsMatch(nSearch.InnerHtml, "\\b" + @currWord + "\\b", RegexOptions.IgnoreCase); if (isMatch) { wordFound.Add(currWord); } } return wordFound; } Is there anyway I can increase the efficiency of this function? The other thing that might be slowing it down is that I use HTML Agility Pack to navigate through some nodes and pull out the body (nSearch.InnerHtml). The _keywordList is a List item, and not an array.

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  • Duplicity Full Backup Lifetime and Efficiency

    - by Tim Lytle
    I'm trying to work up a backup strategy for some clients, and am leaning towards duplicity for remote backup (already use rdiff-backup for internal/on location backups). Is it reasonable to want a full backup every so often? Since duplicity increments forward, each incremental backup is relying on the previous increment, and all are relying heavily on the last full backup. Should that become corrupt, bad things happen. A related question: Does Duplicity test the incremental backups for consistency? Assuming I do want a full backup every so often, how efficiently does duplicity create that full backup? Can/does it check file signatures and copy unchanged data from previous full backups/increments? Basically creating a new 'full' archive transferring new/changed data and merging existing unchanged data? Right now my concern is that running a full backup is needed, but the consistent large bandwidth use of full backups will make this unreasonable for some clients.

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  • MS Securily Essentials efficiency / usage, suspicious processes

    - by biggvsdiccvs
    I recently noticed that my (originally pretty fast) Windows 7 Pro laptop started getting slow and using a lot of CPU power for no apparent reason. A full scan by Microsoft Security Essentials revealed nothing. After some investigation, I found multiple instances of a strange process called urpev.exe and a couple of similar exe files sitting in subdirectories of Users//AppData/Roaming (this particular one was in a folder called Xyceowme). Description: "Mescrosift Visaal Studie 2010". Company name: "Mesrosift Corporatien". Is it a virus or something? :) Now, all of these exe files were scheduled to be started from the Task Scheduler by tasks with names like "Security Center Update - 1291373911" and similar. My user name was listed as the author of the tasks. I disabled the tasks, restarted the computer in safe mode and moved all of the exe files to quarantine for further investigation. All of this was done last night. I just scanned the files with Security Essentials again (not updated since yesterday) in the quarantine location and this time it found PWS:Win32/Zbot.gen!plock in urpev.exe (but not in the other exe files, which are most likely viruses, too). Category: Password Stealer Description: This program is dangerous and captures user passwords. Another strange process is browser.exe (not chrome.exe) by Google Inc., described as Google Chrome. I uninstalled Chrome but it's still there. It runs out of Users\\AppData\LocalLow\UIVoice\ToolMedium\browser.exe and if I move it in safe mode, it just reappears there, and multiple instances run. Needless to say, it I kill it, it just runs again. Couldn't see anything in Task Scheduler, but found a couple of references to it in the Registry Editor: HKEY_CURRENT_USER/Software/Microsoft/Internet Explorer/LowRegistry/Audio/PolicyConfig/PropertyStore/ HKEY_USERS/S-1-5-21-1685709306-872053864-2599010960-1002/Software/Microsoft/Internet Explorer/LowRegistry/Audio/PolicyConfig/PropertyStore/ Maybe it's a legit process, but seems kind of strange. For the time being, I suspended the process and killed all of the child processes when I booted up the laptop. I used Security Essentials to scan the system periodically, but obviously it's not effective at least against one virus. I had the "real-time protection" turned off. Would it help if it were turned on and how much of a nuisance would it be? I wonder if there is a better alternative to Security Essentials. Over the years I've used multiple antivirus products at home and especially at work and was not very happy with any of them. Apparently, asking for software recommendations or comparisons is taboo here, but I will mention that I installed Malware Bytes and it was able to find an quarantine a bunch of suspicious files, and at least some of which were truly infected, but when it scans the bogus security center update executables from Mesrosift Corporatien, it finds nothing wrong. Also, any thoughts on the browser.exe mystery? Neither MS Security Essentials nor Malware Bytes found anything wrong with that file. However, after I ran a Malware Bytes scan and quarantined everything it found suspicious and rebooted the laptop, the process did not run.

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  • Multitasking on iOS4 and its stated battery efficiency

    - by eml
    Apple stated that the reason multitasking didn't arrive before iOS4 is because they hadn't figured out how to do it right. Jobs stated at Apple WWDC 2010 that they now do and that they solved the problem of preserving battery performance regarding multitasking. Is iOS4's multitasking "feature" indeed more efficient regarding battery performance compared to Android? Have the Android developers managed to "do it right" too?

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  • Efficiency questions

    - by rayman
    Hi, I have to manage XML documents and Strings in my app. In terms of efficiency and memory usage, will a collection like ArrayList be much more expensive than String[]? Also, I could store the content as a regular String or XML. Is working with XML also more expensive? (When I say expensive, I am referring to the use of system resources.) If there are differences, are they significant? Thanks, Ray.

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  • Is it inefficient to access a python class member container in a loop statement?

    - by Dave
    Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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  • Improving MySQL Update Query Efficiency

    - by Russell C.
    In our database tables we keep a number of counting columns to help reduce the number of simple lookup queries. For example, in our users table we have columns for the number of reviews written, photos uploaded, friends, followers, etc. To help make sure these stay in sync we have a script that runs periodically to check and update these counting columns. The problem is that now that our database has grown significantly the queries we have been using are taking forever to run since they are totally inefficient. I would appreciate someone with more MySQL knowledge than myself to recommend how we can improve it's efficiency: update users set photos=(select count(*) from photos where photos.status="A" AND photos.user_id=users.id) where users.status="A"; If this were a select statement I would just use a join but I'm not sure if that is possible with update. Thanks in advance for your help!

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  • Improve Efficiency for This Text Processing Code

    - by johnv
    I am writing a program that counts the number of words in a text file which is already in lowercase and separated by spaces. I want to use a dictionary and only count the word IF it's within the dictionary. The problem is the dictionary is quite large (~100,000 words) and each text document has also ~50,000 words. As such, the codes that I wrote below gets very slow (takes about 15 sec to process one document on a quad i7 machine). I'm wondering if there's something wrong with my coding and if the efficiency of the program can be improved. Thanks so much for your help. Code below: public static string WordCount(string countInput) { string[] keywords = ReadDic(); /* read dictionary txt file*/ /*then reads the main text file*/ Dictionary<string, int> dict = ReadFile(countInput).Split(' ') .Select(c => c) .Where(c => keywords.Contains(c)) .GroupBy(c => c) .Select(g => new { word = g.Key, count = g.Count() }) .OrderBy(g => g.word) .ToDictionary(d => d.word, d => d.count); int s = dict.Sum(e => e.Value); string k = s.ToString(); return k; }

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  • DVD/CD burning .zip: is it more reliable, faster, longer lasting to burn a zip of files rather than the files as a folder?

    - by Rob
    Is it more reliable, faster, longer lasting to burn to CD/DVD a zip (or a few large zips) of files rather than the files as a folder? Just thinking if 1000s of small files would not be as efficiently recorded compared with one or a few large zips. Also, even after the burning program verifies the disc, I also use Beyond Compare to compare the files with those on the disc. Always binary compares as identical but I hear the drive stuttering presumably as the head is being shifted only slightly each time to seek the next file, which leads me to think that its best to make one or more zips and copy those locally to compare. Or is it that burning invidual files to the disc is not as readable which causes the head to stutter. There aren't any problems, my disc burns are reliable, just thinking more of efficiency and longevity, the discs burn and verify fast enough on my 18x DVD burner. I'm using ImgBurn mostly. Also used Nero in the past. I burn whole discs closed, finalised. Not sure which write mode but would think Disc At Once from a temporary cached image made by the burning program would be the most reliable.

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  • Improve XPath efficiency for repeated, parameterized queries

    - by Chris Allan
    Hi, I am repeatedly performing the following XPath query (though parameterized by 'keywordText') around 40,000 times: String query = SystemGlobal.YAHOO_KEYWORDSSUBNODE + "/" + SystemGlobal.YAHOO_KEYWORDNODE + "[" + SystemGlobal.YAHOO_ATTRKEYPHRASE + "='" + keywordText + "']"; CachedXPathAPI cachedXPathAPI = new CachedXPathAPI(); NodeIterator nl = cachedXPathAPI.selectNodeIterator(doc.getElementsByTagName(SystemGlobal.YAHOO_KEYWORDSROOT).item(0), query); Node n; if ((n = nl.nextNode()) != null) { keyword.setKeywordId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRKEYID).getTextContent())); keyword.setKeyPhrase(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRKEYPHRASE).getTextContent()); keyword.setStatus(mapStatus(cachedXPathAPI.selectSingleNode(n, SystemGlobal.YAHOO_ATTRSTATUS).getTextContent())); keyword.setCampaignId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, "../../" + SystemGlobal.YAHOO_ATTRCAMPAIGNID).getTextContent())); keyword.setAdGroupId(Long.parseLong(cachedXPathAPI.selectSingleNode(n, "../" + SystemGlobal.YAHOO_ATTRADGROUPID).getTextContent())); On the first run of the script, all 40,000 runs of this piece of code will have nl.nextNode() == null, and everything runs quite quickly. However, on the following runs, when nl.nextNode() != null, then things slow down a lot - this takes around an additional 40min to run (whereas the first run takes maybe 1 minute). Oh, and the doc is constructed like so: InputSource in = new InputSource(new FileInputStream(filename)); DocumentBuilderFactory dfactory = DocumentBuilderFactory.newInstance(); dfactory.setNamespaceAware(true); doc = dfactory.newDocumentBuilder().parse(in); I tried including the following lines reportEvaluator = new XPathEvaluatorImpl(reportDoc); reportResolver = reportEvaluator.createNSResolver(reportDoc); and rather creating a NodeIterator, instead creating an XPathResult: XPathResult result = (XPathResult)reportEvaluator.evaluate(query, doc.getElementsByTagName(SystemGlobal.YAHOO_KEYWORDSROOT).item(0), reportResolver, XPathResult.UNORDERED_NODE_ITERATOR_TYPE, null); however this ran even slower Is there a way in which I can speed up the running of this script? I have seen references to precompiled queries, though I haven't seen many actual details. Also, as seen in the code, I am using CachedXPathAPI, though the benefit for this case is not so great. Any help is much appreciated! Chris Allan

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  • T/SQL Efficiency and Order of Execution

    - by Kyle Rozendo
    Hi All, In regards to the order of execution of statements in SQL, is there any difference between the following performance wise? SELECT * FROM Persons WHERE UserType = 'Manager' AND LastName IN ('Hansen','Pettersen') And: SELECT * FROM Persons WHERE LastName IN ('Hansen','Pettersen') AND UserType = 'Manager' If there is any difference, is there perhaps a link etc. that you may have where one can learn more about this? Thanks a ton, Kyle

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  • F# currying efficiency?

    - by Eamon Nerbonne
    I have a function that looks as follows: let isInSet setElems normalize p = normalize p |> (Set.ofList setElems).Contains This function can be used to quickly check whether an element is semantically part of some set; for example, to check if a file path belongs to an html file: let getLowerExtension p = (Path.GetExtension p).ToLowerInvariant() let isHtmlPath = isInSet [".htm"; ".html"; ".xhtml"] getLowerExtension However, when I use a function such as the above, performance is poor since evaluation of the function body as written in "isInSet" seems to be delayed until all parameters are known - in particular, invariant bits such as (Set.ofList setElems).Contains are reevaluated each execution of isHtmlPath. How can best I maintain F#'s succint, readable nature while still getting the more efficient behavior in which the set construction is preevaluated. The above is just an example; I'm looking for a general pattern that avoids bogging me down in implementation details - where possible I'd like to avoid being distracted by details such as the implementation's execution order since that's usually not important to me and kind of undermines a major selling point of functional programming.

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  • Increase efficiency of a loop with jQuery

    - by Pez Cuckow
    I have a game coded in jQuery where bots are moved around the screen. The below code is a loop that runs every 20ms, currently if you have over 15 bots you start to notice the browser lagging (simply because of all the advanced collision detection going on). Is there any way to reduce the lag, can I make it any more efficient? P.s. sorrry for just posting a block of code, I can't see a way to make my point clear enough without! $.playground().registerCallback(function(){ //Movement Loop if(!pause) { for (var i in bots) { //bots - color, dir, x, y, z, spawned?, spawnerid, prevd var self = $('#b' + i); var current = bots[i]; if(bots[i][5]==1) { var xspeed = 0, yspeed = 0; if(current[1]==0) { yspeed = -D_SPEED; } else if(current[1]==1) { xspeed = D_SPEED; } else if(current[1]==2) { yspeed = D_SPEED; } else if(current[1]==3) { xspeed = -D_SPEED; } var x = current[2] + xspeed; var y = current[3] + yspeed; var z = current[3] + 120; if(current[2]>0&&x>PLAYGROUND_WIDTH||current[2]<0&&x<-GRID_SIZE|| current[3]>0&&y>PLAYGROUND_HEIGHT||current[3]<0&&y<-GRID_SIZE) { remove_bot(i, self); } else { if(current[7]!=current[1]) { self.setAnimation(colors[current[0]][current[1]]); bots[i][7] = current[1]; } if(self.css({"left": ""+(x)+"px", "top": ""+(y)+"px", "z-index": z})) { bots[i][2] = x; bots[i][3] = y; bots[i][4] = z; bots[i][8]++; } } } } $("#debug").html(dump(arrows)); $(".bot").each(function(){ var b_id = $(this).attr("id").substr(1); var collision = false; var c_bot = bots[b_id]; var b_x = c_bot[2]; var b_y = c_bot[3]; var b_d = c_bot[1]; $(this).collision(".arrow,#arrows").each(function(){ //Many thanks to Selim Arsever for this fix! var a_id = $(this).attr("id").substr(1); var piece = arrows[a_id]; var a_v = piece[0]; if(a_v==1) { var a_x = piece[2]; var a_y = piece[3]; var d_x = b_x-a_x; var d_y = b_y-a_y; if(d_x>=4&&d_x<=5&&d_y>=1&&d_y<=2) { //bots - color, dir, x, y, z, spawned?, spawnerid, prevd bots[b_id][7] = c_bot[1]; bots[b_id][1] = piece[1]; collision = true; } } }); if(!collision) { $(this).collision(".wall,#level").each(function(){ var w_id = $(this).attr("id").substr(1); var piece = pieces[w_id]; var w_x = piece[1]; var w_y = piece[2]; d_x = b_x-w_x; d_y = b_y-w_y; if(b_d==0&&d_x>=4&&d_x<=5&&d_y>=27&&d_y<=28) { kill_bot(b_id); collision = true; } //4 // 33 if(b_d==1&&d_x>=-12&&d_x<=-11&&d_y>=21&&d_y<=22) { kill_bot(b_id); collision = true; } //-14 // 21 if(b_d==2&&d_x>=4&&d_x<=5&&d_y>=-9&&d_y<=-8) { kill_bot(b_id); collision = true; } //4 // -9 if(b_d==3&&d_x>=22&&d_x<=23&&d_y>=20&&d_y<=21) { kill_bot(b_id); collision = true; } //22 // 21 }); } if(!collision&&c_bot[8]>GRID_MOVE) { $(this).collision(".spawn,#level").each(function(){ var s_id = $(this).attr("id").substr(1); var piece = pieces[s_id]; var s_x = piece[1]; var s_y = piece[2]; d_x = b_x-s_x; d_y = b_y-s_y; if(b_d==0&&d_x>=4&&d_x<=5&&d_y>=19&&d_y<=20) { kill_bot(b_id); collision = true; } //4 // 33 if(b_d==1&&d_x>=-14&&d_x<=-13&&d_y>=11&&d_y<=12) { kill_bot(b_id); collision = true; } //-14 // 21 if(b_d==2&&d_x>=4&&d_x<=5&&d_y>=-11&&d_y<=-10) { kill_bot(b_id); collision = true; } //4 // -9 if(b_d==3&&d_x>=22&&d_x<=23&&d_y>=11&&d_y<=12) { kill_bot(b_id); collision = true; } //22 // 21*/ }); } if(!collision) { $(this).collision(".exit,#level").each(function(){ var e_id = $(this).attr("id").substr(1); var piece = pieces[e_id]; var e_x = piece[1]; var e_y = piece[2]; d_x = b_x-e_x; d_y = b_y-e_y; if(d_x>=4&&d_x<=5&&d_y>=1&&d_y<=2) { current_bots++; bots[b_id] = false; $("#current_bots").html(current_bots); $("#b" + b_id).setAnimation(exit[2], function(node){$(node).fadeOut(200)}); } }); } if(!collision) { $(this).collision(".bot,#level").each(function(){ var bd_id = $(this).attr("id").substr(1); if(bd_id!=b_id) { var piece = bots[bd_id]; var bd_x = piece[2]; var bd_y = piece[3]; d_x = b_x-bd_x; d_y = b_y-bd_y; if(d_x>=0&&d_x<=2&&d_y>=0&&d_y<=2) { kill_bot(b_id); kill_bot(bd_id); collision = true; } } }); } }); } }, REFRESH_RATE); Many thanks,

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  • NSXMLParser Memory Allocation Efficiency for the iPhone

    - by Staros
    Hello, I've recently been playing with code for an iPhone app to parse XML. Sticking to Cocoa, I decided to go with the NSXMLParser class. The app will be responsible for parsing 10,000+ "computers", all which contain 6 other strings of information. For my test, I've verified that the XML is around 900k-1MB in size. My data model is to keep each computer in an NSDictionary hashed by a unique identifier. Each computer is also represented by a NSDictionary with the information. So at the end of the day, I end up with a NSDictionary containing 10k other NSDictionaries. The problem I'm running into isn't about leaking memory or efficient data structure storage. When my parser is done, the total amount of allocated objects only does go up by about 1MB. The problem is that while the NSXMLParser is running, my object allocation is jumping up as much as 13MB. I could understand 2 (one for the object I'm creating and one for the raw NSData) plus a little room to work, but 13 seems a bit high. I can't imaging that NSXMLParser is that inefficient. Thoughts? Code... The code to start parsing... NSXMLParser *parser = [[NSXMLParser alloc] initWithData: data]; [parser setDelegate:dictParser]; [parser parse]; output = [[dictParser returnDictionary] retain]; [parser release]; [dictParser release]; And the parser's delegate code... -(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict { if(mutableString) { [mutableString release]; mutableString = nil; } mutableString = [[NSMutableString alloc] init]; } -(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if(self.mutableString) { [self.mutableString appendString:string]; } } -(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if([elementName isEqualToString:@"size"]){ //The initial key, tells me how many computers returnDictionary = [[NSMutableDictionary alloc] initWithCapacity:[mutableString intValue]]; } if([elementName isEqualToString:hashBy]){ //The unique identifier if(mutableDictionary){ [mutableDictionary release]; mutableDictionary = nil; } mutableDictionary = [[NSMutableDictionary alloc] initWithCapacity:6]; [returnDictionary setObject:[NSDictionary dictionaryWithDictionary:mutableDictionary] forKey:[NSMutableString stringWithString:mutableString]]; } if([fields containsObject:elementName]){ //Any of the elements from a single computer that I am looking for [mutableDictionary setObject:mutableString forKey:elementName]; } } Everything initialized and released correctly. Again, I'm not getting errors or leaking. Just inefficient. Thanks for any thoughts!

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  • Efficiency of Java "Double Brace Initialization"?

    - by Jim Ferrans
    In Hidden Features of Java the top answer mentions Double Brace Initialization, with a very enticing syntax: Set<String> flavors = new HashSet<String>() {{ add("vanilla"); add("strawberry"); add("chocolate"); add("butter pecan"); }}; This idiom creates an anonymous inner class with just an instance initializer in it, which "can use any [...] methods in the containing scope". Main question: Is this as inefficient as it sounds? Should its use be limited to one-off initializations? (And of course showing off!) Second question: The new HashSet must be the "this" used in the instance initializer ... can anyone shed light on the mechanism? Third question: Is this idiom too obscure to use in production code? Summary: Very, very nice answers, thanks everyone. On question (3), people felt the syntax should be clear (though I'd recommend an occasional comment, especially if your code will pass on to developers who may not be familiar with it). On question (1), The generated code should run quickly. The extra .class files do cause jar file clutter, and slow program startup slightly (thanks to coobird for measuring that). Thilo pointed out that garbage collection can be affected, and the memory cost for the extra loaded classes may be a factor in some cases. Question (2) turned out to be most interesting to me. If I understand the answers, what's happening in DBI is that the anonymous inner class extends the class of the object being constructed by the new operator, and hence has a "this" value referencing the instance being constructed. Very neat. Overall, DBI strikes me as something of an intellectual curiousity. Coobird and others point out you can achieve the same effect with Arrays.asList, varargs methods, Google Collections, and the proposed Java 7 Collection literals. Newer JVM languages like Scala, JRuby, and Groovy also offer concise notations for list construction, and interoperate well with Java. Given that DBI clutters up the classpath, slows down class loading a bit, and makes the code a tad more obscure, I'd probably shy away from it. However, I plan to spring this on a friend who's just gotten his SCJP and loves good natured jousts about Java semantics! ;-) Thanks everyone!

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  • Efficiency of nested Loop

    - by didxga
    See the following snippet: //first nested loops for(int i=0;i<10;i++) { for(int j=1;j<1000000;j++) { //do some stuff } } //second nested loops for(int i=0;i<1000000;i++) { for(int j=1;j<10;j++) { //do some stuff } } I am wondering why the first nested loops is running slower than the second one? Regards!

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  • calloc v/s malloc and time efficiency

    - by yCalleecharan
    Hi, I've read with interest the post "c difference between malloc and calloc". I'm using malloc in my code and would like to know what difference I'll have using calloc instead. My present (pseudo)code with malloc: Scenario 1 int main() { allocate large arrays with malloc INITIALIZE ALL ARRAY ELEMENTS TO ZERO for loop //say 1000 times do something and write results to arrays end for loop FREE ARRAYS with free command } //end main If I use calloc instead of malloc, then I'll have: Scenario2 int main() { for loop //say 1000 times ALLOCATION OF ARRAYS WITH CALLOC do something and write results to arrays FREE ARRAYS with free command end for loop } //end main I have three questions: Which of the scenarios is more efficient if the arrays are very large? Which of the scenarios will be more time efficient if the arrays are very large? In both scenarios,I'm just writing to arrays in the sense that for any given iteration in the for loop, I'm writing each array sequentially from the first element to the last element. The important question: If I'm using malloc as in scenario 1, then is it necessary that I initialize the elements to zero? Say with malloc I have array z = [garbage1, garbage2, garbage 3]. For each iteration, I'm writing elements sequentially i.e. in the first iteration I get z =[some_result, garbage2, garbage3], in the second iteration I get in the first iteration I get z =[some_result, another_result, garbage3] and so on, then do I need specifically to initialize my arrays after malloc?

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  • jQuery/Javascript framework efficiency

    - by Russell
    My latest project is using a javascript framework (jQuery), along with some plugins (validation, jquery-ui, datepicker, facebox, ...) to help make a modern web application. I am now finding pages loading slower than I am used to. After some js profiling (thanks VS2010!), it seems a lot of the time is taken procesing inside the framework. Now I understand the more complex the ui tools, the more processing needs to be done. The project is not yet at a large stage and I think would be average functions. At this stage I can see it is not going to scale well. I noticed things like the 'each' command in jQuery takes quite a lot of processing time. Have others experienced some extra latency using JS frameworks? How do I minimise their effect on page performance? Are there best practices on implementation using JS frameworks? Thanks

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  • Efficiency of checking for null varbinary(max) column ?

    - by Moe Sisko
    Using SQL Server 2008. Example table : CREATE table dbo.blobtest (id int primary key not null, name nvarchar(200) not null, data varbinary(max) null) Example query : select id, name, cast((case when data is null then 0 else 1 end) as bit) as DataExists from dbo.blobtest Now, the query needs to return a "DataExists" column, that returns 0 if the blob is null, else 1. This all works fine, but I'm wondering how efficient it is. i.e. does SQL server need to read in the whole blob to its memory, or is there some optimization so that it just does enough reads to figure out if the blob is null or not ? (FWIW, the sp_tableoption "large value types out of row" option is set to OFF for this example).

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  • Increase efficiency of a loop with jQuery and GameQuery

    - by Pez Cuckow
    I have a game coded in jQuery where bots are moved around the screen. The below code is a loop that runs every 20ms, currently if you have over 15 bots you start to notice the browser lagging (simply because of all the advanced collision detection going on). Is there any way to reduce the lag, can I make it any more efficient? P.s. sorrry for just posting a block of code, I can't see a way to make my point clear enough without! $.playground().registerCallback(function(){ //Movement Loop if(!pause) { for (var i in bots) { //bots - color, dir, x, y, z, spawned?, spawnerid, prevd var self = $('#b' + i); var current = bots[i]; if(bots[i][5]==1) { var xspeed = 0, yspeed = 0; if(current[1]==0) { yspeed = -D_SPEED; } else if(current[1]==1) { xspeed = D_SPEED; } else if(current[1]==2) { yspeed = D_SPEED; } else if(current[1]==3) { xspeed = -D_SPEED; } var x = current[2] + xspeed; var y = current[3] + yspeed; var z = current[3] + 120; if(current[2]>0&&x>PLAYGROUND_WIDTH||current[2]<0&&x<-GRID_SIZE|| current[3]>0&&y>PLAYGROUND_HEIGHT||current[3]<0&&y<-GRID_SIZE) { remove_bot(i, self); } else { if(current[7]!=current[1]) { self.setAnimation(colors[current[0]][current[1]]); bots[i][7] = current[1]; } if(self.css({"left": ""+(x)+"px", "top": ""+(y)+"px", "z-index": z})) { bots[i][2] = x; bots[i][3] = y; bots[i][4] = z; bots[i][8]++; } } } } $("#debug").html(dump(arrows)); $(".bot").each(function(){ var b_id = $(this).attr("id").substr(1); var collision = false; var c_bot = bots[b_id]; var b_x = c_bot[2]; var b_y = c_bot[3]; var b_d = c_bot[1]; $(this).collision(".arrow,#arrows").each(function(){ //Many thanks to Selim Arsever for this fix! var a_id = $(this).attr("id").substr(1); var piece = arrows[a_id]; var a_v = piece[0]; if(a_v==1) { var a_x = piece[2]; var a_y = piece[3]; var d_x = b_x-a_x; var d_y = b_y-a_y; if(d_x>=4&&d_x<=5&&d_y>=1&&d_y<=2) { //bots - color, dir, x, y, z, spawned?, spawnerid, prevd bots[b_id][7] = c_bot[1]; bots[b_id][1] = piece[1]; collision = true; } } }); if(!collision) { $(this).collision(".wall,#level").each(function(){ var w_id = $(this).attr("id").substr(1); var piece = pieces[w_id]; var w_x = piece[1]; var w_y = piece[2]; d_x = b_x-w_x; d_y = b_y-w_y; if(b_d==0&&d_x>=4&&d_x<=5&&d_y>=27&&d_y<=28) { kill_bot(b_id); collision = true; } //4 // 33 if(b_d==1&&d_x>=-12&&d_x<=-11&&d_y>=21&&d_y<=22) { kill_bot(b_id); collision = true; } //-14 // 21 if(b_d==2&&d_x>=4&&d_x<=5&&d_y>=-9&&d_y<=-8) { kill_bot(b_id); collision = true; } //4 // -9 if(b_d==3&&d_x>=22&&d_x<=23&&d_y>=20&&d_y<=21) { kill_bot(b_id); collision = true; } //22 // 21 }); } if(!collision&&c_bot[8]>GRID_MOVE) { $(this).collision(".spawn,#level").each(function(){ var s_id = $(this).attr("id").substr(1); var piece = pieces[s_id]; var s_x = piece[1]; var s_y = piece[2]; d_x = b_x-s_x; d_y = b_y-s_y; if(b_d==0&&d_x>=4&&d_x<=5&&d_y>=19&&d_y<=20) { kill_bot(b_id); collision = true; } //4 // 33 if(b_d==1&&d_x>=-14&&d_x<=-13&&d_y>=11&&d_y<=12) { kill_bot(b_id); collision = true; } //-14 // 21 if(b_d==2&&d_x>=4&&d_x<=5&&d_y>=-11&&d_y<=-10) { kill_bot(b_id); collision = true; } //4 // -9 if(b_d==3&&d_x>=22&&d_x<=23&&d_y>=11&&d_y<=12) { kill_bot(b_id); collision = true; } //22 // 21*/ }); } if(!collision) { $(this).collision(".exit,#level").each(function(){ var e_id = $(this).attr("id").substr(1); var piece = pieces[e_id]; var e_x = piece[1]; var e_y = piece[2]; d_x = b_x-e_x; d_y = b_y-e_y; if(d_x>=4&&d_x<=5&&d_y>=1&&d_y<=2) { current_bots++; bots[b_id] = false; $("#current_bots").html(current_bots); $("#b" + b_id).setAnimation(exit[2], function(node){$(node).fadeOut(200)}); } }); } if(!collision) { $(this).collision(".bot,#level").each(function(){ var bd_id = $(this).attr("id").substr(1); if(bd_id!=b_id) { var piece = bots[bd_id]; var bd_x = piece[2]; var bd_y = piece[3]; d_x = b_x-bd_x; d_y = b_y-bd_y; if(d_x>=0&&d_x<=2&&d_y>=0&&d_y<=2) { kill_bot(b_id); kill_bot(bd_id); collision = true; } } }); } }); } }, REFRESH_RATE); Many thanks,

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  • Array sorting efficiency... Beginner need advice

    - by SoleSoft
    I'll start by saying I am very much a beginner programmer, this is essentially my first real project outside of using learning material. I've been making a 'Simon Says' style game (the game where you repeat the pattern generated by the computer) using C# and XNA, the actual game is complete and working fine but while creating it, I wanted to also create a 'top 10' scoreboard. The scoreboard would record player name, level (how many 'rounds' they've completed) and combo (how many buttons presses they got correct), the scoreboard would then be sorted by combo score. This led me to XML, the first time using it, and I eventually got to the point of having an XML file that recorded the top 10 scores. The XML file is managed within a scoreboard class, which is also responsible for adding new scores and sorting scores. Which gets me to the point... I'd like some feedback on the way I've gone about sorting the score list and how I could have done it better, I have no other way to gain feedback =(. I know .NET features Array.Sort() but I wasn't too sure of how to use it as it's not just a single array that needs to be sorted. When a new score needs to be entered into the scoreboard, the player name and level also have to be added. These are stored within an 'array of arrays' (10 = for 'top 10' scores) scoreboardComboData = new int[10]; // Combo scoreboardTextData = new string[2][]; scoreboardTextData[0] = new string[10]; // Name scoreboardTextData[1] = new string[10]; // Level as string The scoreboard class works as follows: - Checks to see if 'scoreboard.xml' exists, if not it creates it - Initialises above arrays and adds any player data from scoreboard.xml, from previous run - when AddScore(name, level, combo) is called the sort begins - Another method can also be called that populates the XML file with above array data The sort checks to see if the new score (combo) is less than or equal to any recorded scores within the scoreboardComboData array (if it's greater than a score, it moves onto the next element). If so, it moves all scores below the score it is less than or equal to down one element, essentially removing the last score and then places the new score within the element below the score it is less than or equal to. If the score is greater than all recorded scores, it moves all scores down one and inserts the new score within the first element. If it's the only score, it simply adds it to the first element. When a new score is added, the Name and Level data is also added to their relevant arrays, in the same way. What a tongue twister. Below is the AddScore method, I've added comments in the hope that it makes things clearer O_o. You can get the actual source file HERE. Below the method is an example of the quickest way to add a score to follow through with a debugger. public static void AddScore(string name, string level, int combo) { // If the scoreboard has not yet been filled, this adds another 'active' // array element each time a new score is added. The actual array size is // defined within PopulateScoreBoard() (set to 10 - for 'top 10' if (totalScores < scoreboardComboData.Length) totalScores++; // Does the scoreboard even need sorting? if (totalScores > 1) { for (int i = totalScores - 1; i > - 1; i--) { // Check to see if score (combo) is greater than score stored in // array if (combo > scoreboardComboData[i] && i != 0) { // If so continue to next element continue; } // Check to see if score (combo) is less or equal to element 'i' // score && that the element is not the last in the // array, if so the score does not need to be added to the scoreboard else if (combo <= scoreboardComboData[i] && i != scoreboardComboData.Length - 1) { // If the score is lower than element 'i' and greater than the last // element within the array, it needs to be added to the scoreboard. This is achieved // by moving each element under element 'i' down an element. The new score is then inserted // into the array under element 'i' for (int j = totalScores - 1; j > i; j--) { // Name and level data are moved down in their relevant arrays scoreboardTextData[0][j] = scoreboardTextData[0][j - 1]; scoreboardTextData[1][j] = scoreboardTextData[1][j - 1]; // Score (combo) data is moved down in relevant array scoreboardComboData[j] = scoreboardComboData[j - 1]; } // The new Name, level and score (combo) data is inserted into the relevant array under element 'i' scoreboardTextData[0][i + 1] = name; scoreboardTextData[1][i + 1] = level; scoreboardComboData[i + 1] = combo; break; } // If the method gets the this point, it means that the score is greater than all scores within // the array and therefore cannot be added in the above way. As it is not less than any score within // the array. else if (i == 0) { // All Names, levels and scores are moved down within their relevant arrays for (int j = totalScores - 1; j != 0; j--) { scoreboardTextData[0][j] = scoreboardTextData[0][j - 1]; scoreboardTextData[1][j] = scoreboardTextData[1][j - 1]; scoreboardComboData[j] = scoreboardComboData[j - 1]; } // The new number 1 top name, level and score, are added into the first element // within each of their relevant arrays. scoreboardTextData[0][0] = name; scoreboardTextData[1][0] = level; scoreboardComboData[0] = combo; break; } // If the methods get to this point, the combo score is not high enough // to be on the top10 score list and therefore needs to break break; } } // As totalScores < 1, the current score is the first to be added. Therefore no checks need to be made // and the Name, Level and combo data can be entered directly into the first element of their relevant // array. else { scoreboardTextData[0][0] = name; scoreboardTextData[1][0] = level; scoreboardComboData[0] = combo; } } } Example for adding score: private static void Initialize() { scoreboardDoc = new XmlDocument(); if (!File.Exists("Scoreboard.xml")) GenerateXML("Scoreboard.xml"); PopulateScoreBoard("Scoreboard.xml"); // ADD TEST SCORES HERE! AddScore("EXAMPLE", "10", 100); AddScore("EXAMPLE2", "24", 999); PopulateXML("Scoreboard.xml"); } In it's current state the source file is just used for testing, initialize is called within main and PopulateScoreBoard handles the majority of other initialising, so nothing else is needed, except to add a test score. I thank you for your time!

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