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  • Python: Does one of these examples waste more memory?

    - by orokusaki
    In a Django view function which uses manual transaction committing, I have: context = RequestContext(request, data) transaction.commit() return render_to_response('basic.html', data, context) # Returns a Django ``HttpResponse`` object which is similar to a dictionary. I think it is a better idea to do this: context = RequestContext(request, data) response = render_to_response('basic.html', data, context) transaction.commit() return response If the page isn't rendered correctly in the second version, the transaction is rolled back. This seems like the logical way of doing it albeit there won't likely be many exceptions at that point in the function when the application is in production. But... I fear that this might cost more and this will be replete through a number of functions since the application is heavy with custom transaction handling, so now is the time to figure out. If the HttpResponse instance is in memory already (at the point of render_to_response()), then what does another reference cost? When the function ends, doesn't the reference (response variable) go away so that when Django is done converting the HttpResponse into a string for output Python can immediately garbage collect it? Is there any reason I would want to use the first version (other than "It's 1 less line of code.")?

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  • While saving a PNG image using NSData writetofile saves corrupted data on the iphone disk

    - by jAmi
    I have a number of images (PNG,GIF and JPG) in my Application Resource Bundle. I want some images to be saved in my Documents Directory so i use : imgPath=[documentsDirectoryPath stringByAppendingPathComponent:@"myImage.png"]; if (![fileMgr fileExistsAtPath:imgPath]) { [[fileMgr contentsAtPath:[[NSBundle mainBundle] pathForResource:@"myImage"ofType:@"png"]] writeToFile:imgPath atomically:NO]; } This saves an Image file on my desired Path but this file has an Extra 300 bytes (of maybe junk data) in it which results in a corrupted image... Am i doing something wrong here? This works in the simulator but on the real device the image has some extra 300 bytes. Also a GIF image gets copied nicely and works but this problem occurs for PNG image.

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  • Has anybody used the WB B-tree library?

    - by Chris B
    I stumbled across the WB on-disk B-tree library: http://people.csail.mit.edu/jaffer/WB It seems like it could be useful for my purposes (swapping data to disk during very large statistical calculations that do not fit in memory), but I was wondering how stable it is. Reading the manual, it seems worringly 'researchy' - there are sections labelled [NOT IMPLEMENTED] etc. But maybe the manual is just out-of-date. So, is this library useable? Am I better off looking at Tokyo Cabinet, MemcacheDB, etc.? By the way I am working in Java.

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  • What really is the purpose of "base" keyword in c#?

    - by Pandiya Chendur
    Thus for used base class for some commom reusable methods in every page of my application... public class BaseClass:System.Web.UI.Page { public string GetRandomPasswordUsingGUID(int length) { string guidResult = System.Guid.NewGuid().ToString(); guidResult = guidResult.Replace("-", string.Empty); return guidResult.Substring(0, length); } } So if i want to use this method i would just do, public partial class forms_age_group : BaseClass { protected void Page_Load(object sender, EventArgs e) { //i would just call it like this string pass = GetRandomPasswordUsingGUID(10); } } It does what i want but there is a "Base" keyword that deals with base class in c# ... I really want to know when should use base keyword in my derived class.... Any good example...

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  • What is the best way to find a processed memory allocations in terms of C# objects

    - by Shantaram
    I have written various C# console based applications, some of them long running some not, which can over time have a large memory foot print. When looking at the windows perofrmance monitor via the task manager, the same question keeps cropping up in my mind; how do I get a break down of the number objects by type that are contributing to this footprint; and which of those are f-reachable and those which aren't and hence can be collected. On numerous occasions I've performed a code inspection to ensure that I am not unnecessarily holding on objects longer than required and disposing of objects with the using construct. I have also recently looked at employing the CG.Collect method when I have released a large number of objects (for example held in a collection which has just been cleared). However, I am not so sure that this made that much difference, so I threw that code away. I am guessing that there are tools in sysinternals suite than can help to resolve these memory type quiestions but I am not sure which and how to use them. The alternative would be to pay for a third party profiling tool such as JetBrains dotTrace; but I need to make sure that I've explored the free options first before going cap in hand to my manager.

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  • efficient android rendering

    - by llll
    I've read quite a few tutorials on game programming on android, and all of them provide basically the same solution as to drawing the game, that is having a dedicated thread spinning like this: public void run() { while(true) { if(!surfaceHolder.getSurface().isValid()) continue; Canvas canvas = surfaceHolder.lockCanvas(); drawGame(canvas); /* do actual drawing here */ surfaceHolder.unlockCanvasAndPost(canvas); } } now I'm wondering, isn't this wasteful? Suppose I've a game with very simple graphics, so that the actual time in drawGame is little; then I'm going to draw the same things on and on, stealing cpu from the other threads; a possibility could be skipping the drawing and sleeping a bit if the game state hasn't changed, which I could check by having the state update thread mantaining a suitable status flag. But maybe there are other options. For example, couldn'it be possible to synchronize with rendering, so that I don't post updates too often? Or am I missing something and that is precisely what lockCanvas does, that is it blocks and burns no cpu until proper time? Thanks in advance L.

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  • C/C++ usage of special CPU features

    - by b-gen-jack-o-neill
    Hi, I am curious, do new compilers use some extra features built into new CPUs such as MMX SSE,3DNow! and so? I mean, in original 8086 there was even no FPU, so compiler that old cannot even use it, but new compilers can, since FPU is part of every new CPU. So, does new compilers use new features of CPU? Or, it should be more right to ask, does new C/C++ standart library functions use new features? Thanks for answer.

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  • what exactly does system.totalMemory test in Actionscript 3.0?

    - by vasion
    before somebody screaming RTFM, let me clarify. does system.totalMemory test the memory used in movie which invokes it, or used by all movies running on the browser/system? I want to initiate garbage collaction for my app when it reaches a certain limit and i dont want the process to be initialized by the user watching funny cats youtube video.

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  • not null usage in mysql

    - by pradeep
    Hi, I use syntax like name varchar(20) NOT NULL in mysql..i have a big confusion over here. typically does it mean that this field is mandatory? but when i store a space in this field it accepts it.is it correct. its like while insert i say '".$_POST['name']."'. even if the name does not have any value query is executed. can any1 just clarify me on this ? is NULL and blank space same ?

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  • The best alternative for String flyweight implementation in Java

    - by Dan
    My application is multithreaded with intensive String processing. We are experiencing excessive memory consumption and profiling has demonstrated that this is due to String data. I think that memory consumption would benefit greatly from using some kind of flyweight pattern implementation or even cache (I know for sure that Strings are often duplicated, although I don't have any hard data in that regard). I have looked at Java Constant Pool and String.intern, but it seems that it can provoke some PermGen problems. What would be the best alternative for implementing application-wide, multithreaded pool of Strings in java?

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  • Usage of autorelease pools for fetch method

    - by Matthias
    Hi, I'm a little bit confused regarding the autorelease pools when programming for the iPhone. I've read a lot and the oppionions seem to me from "Do-NOT-use" to "No problem to use". My specific problem is, I would like to have a class which encapsulates the SQLite3 Access, so I have for example the following method: -(User*)fetchUserWithId:(NSInteger)userId Now, within this method a SQL query is done and a new user object is created with the data from the database and then returned. Within this DB Access class I don't need this object anymore, so I can do a release, but since the calling method needs it, I would do an autorelease, wouldn't I? So, is it okay to use autorelease here oder would it gain too much memory, if this method is called quite frequently? Some websites say, that the autorelease pool is released first at the end of the application, some say, at every event (e.g. user touches something). If I should not use autorelease, how can I make sure, that the object is released correctly? Can I do a release in the fetch method and hope, that the object is still there until the calling method can do a retain? Thanks for your help! Regards Matthias

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  • What percent of web sites use JavaScript?

    - by Claudiu
    I'm wondering just how pervasive JavaScript is. This article states that 73% of websites they tested rely on JavaScript for important functionality, but it seems to me that the number must be larger. Have any surveys been done on this topic? Maybe a better way to phrase this question is - are there any sites that don't use JavaScript? EDIT: By 'use', I don't necessarily mean "rely on for important functionality" - that was just the statistic that one article gave.

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  • in java, which is better - three arrays of booleans or 1 array of bytes?

    - by joe_shmoe
    I know the question sounds silly, but consider this: I have an array of items and a labelling algorithm. at any point the item is in one of three states. The current version holds these states in a byte array, where 0, 1 and 2 represent the three states. alternatively, I could have three arrays of boolean - one for each state. which is better (consumes less memory) depends on how jvm (sun's version) stores the arrays - is a boolean represented by 1 bit? (p.s. don't start with all that "this is not the way OO/Java works" - I know, but here performance comes in front. plus the algorithm is simple and perfectly readable even in such form). Thanks a lot

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  • Usage of atoi in the c language

    - by maddy
    I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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  • mysql stored funtion usage

    - by shikhar
    I just wrote a stored function to calculate the working days between two dates. This works select CountWeekDays('2010-03-07','2010-04-07') This doesn't work select CountWeekDays(o.order_date,o.created_date) from orders o; Any idea how to make this one work ?? function definition delimiter $$; CREATE FUNCTION CountWeekDays (sdate VARCHAR(50), edate VARCHAR(50)) RETURNS INT BEGIN DECLARE wdays, tdiff, counter, thisday smallint; DECLARE newdate DATE; SET newdate := sdate; SET wdays = 0; if DATEDIFF(edate, sdate) = 0 THEN RETURN 1; END IF; if DATEDIFF(edate, sdate) < 0 THEN RETURN 0; END IF; label1: LOOP SET thisday = DAYOFWEEK(newdate); IF thisday BETWEEN 2 AND 6 THEN SET wdays := wdays + 1; END IF; SET newdate = DATE_ADD(newdate, INTERVAL 1 DAY); IF DATEDIFF(edate, newdate) < 0 THEN LEAVE label1; END IF; END LOOP label1; RETURN wdays; END

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  • Need Google Map InfoWindow Hyperlink to Open Content in Overlay (Fusion Table Usage)

    - by McKev
    I have the following code established to render the map in my site. When the map is clicked, the info window pops up with a bunch of content including a hyperlink to open up a website with a form in it. I would like to utilize a function like fancybox to open up this link "form" in an overlay. I have read that fancybox doesn't support calling the function from within an iframe, and was wondering if there was a way to pass the link data to the DOM and trigger the fancybox (or another overlay option) in another way? Maybe a callback trick - any tips would be much appreciated! <style> #map-canvas { width:850px; height:600px; } </style> <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true"></script> <script src="http://gmaps-utility-gis.googlecode.com/svn/trunk/fusiontips/src/fusiontips.js" type="text/javascript"></script> <script type="text/javascript"> var map; var tableid = "1nDFsxuYxr54viD_fuH7fGm1QRZRdcxFKbSwwRjk"; var layer; var initialLocation; var browserSupportFlag = new Boolean(); var uscenter = new google.maps.LatLng(37.6970, -91.8096); function initialize() { map = new google.maps.Map(document.getElementById('map-canvas'), { zoom: 4, mapTypeId: google.maps.MapTypeId.ROADMAP }); layer = new google.maps.FusionTablesLayer({ query: { select: "'Geometry'", from: tableid }, map: map }); //http://gmaps-utility-gis.googlecode.com/svn/trunk/fusiontips/docs/reference.html layer.enableMapTips({ select: "'Contact Name','Contact Title','Contact Location','Contact Phone'", from: tableid, geometryColumn: 'Geometry', suppressMapTips: false, delay: 500, tolerance: 8 }); ; // Try W3C Geolocation (Preferred) if(navigator.geolocation) { browserSupportFlag = true; navigator.geolocation.getCurrentPosition(function(position) { initialLocation = new google.maps.LatLng(position.coords.latitude,position.coords.longitude); map.setCenter(initialLocation); //Custom Marker var pinColor = "A83C0A"; var pinImage = new google.maps.MarkerImage("http://chart.apis.google.com/chart?chst=d_map_pin_letter&chld=%E2%80%A2|" + pinColor, new google.maps.Size(21, 34), new google.maps.Point(0,0), new google.maps.Point(10, 34)); var pinShadow = new google.maps.MarkerImage("http://chart.apis.google.com/chart?chst=d_map_pin_shadow", new google.maps.Size(40, 37), new google.maps.Point(0, 0), new google.maps.Point(12, 35)); new google.maps.Marker({ position: initialLocation, map: map, icon: pinImage, shadow: pinShadow }); }, function() { handleNoGeolocation(browserSupportFlag); }); } // Browser doesn't support Geolocation else { browserSupportFlag = false; handleNoGeolocation(browserSupportFlag); } function handleNoGeolocation(errorFlag) { if (errorFlag == true) { //Geolocation service failed initialLocation = uscenter; } else { //Browser doesn't support geolocation initialLocation = uscenter; } map.setCenter(initialLocation); } } google.maps.event.addDomListener(window, 'load', initialize); </script>

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  • Proper QUuid usage in Qt ? (7-Zip DLL usage problems (QLibrary, QUuid GUID conversion, interfaces))

    - by whipsnap
    Hi, I'm trying to write a program that would use 7-Zip DLL for reading files from inside archive files (7z, zip etc). Here's where I'm so far: #include QtCore/QCoreApplication #include QLibrary #include QUuid #include iostream using namespace std; #include "7z910/CPP/7zip/Archive/IArchive.h" #include "7z910/CPP/7zip/IStream.h" #include "MyCom.h" // {23170F69-40C1-278A-1000-000110070000} QUuid CLSID_CFormat7z(0x23170F69, 0x40C1, 0x278A, 0x10, 0x00, 0x00, 0x01, 0x10, 0x07, 0x00, 0x00); typedef int (*CreateObjectFunc)( const GUID *clsID, const GUID *interfaceID, void **outObject); void readFileInArchive() { QLibrary myLib("7z.dll"); CreateObjectFunc myFunction = (CreateObjectFunc)myLib.resolve("CreateObject"); if (myFunction == 0) { cout outArchive; myFunction(&CLSID_CFormat7z, &IID_IOutArchive, (void **)&outArchive); } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); readFileInArchive(); return a.exec(); } Trying to build that in Qt Creator will lead to following error: cannot convert 'QUuid*' to 'const GUID*' in argument passing How should QUuid be correctly used in this context? Also, being a C++ and Qt newbie I haven't yet quite grasped templates or interfaces, so overall I'm having trouble getting through these first steps. If someone could give tips or even example code on how for example an image file could be extracted from ZIP file (to be shown in Qt GUI later on*), I would highly appreciate that. My main goal at the moment is to write a program with GUI for selecting archive files containing image files (PNG, JPG etc) and displaying those files one at a time in the GUI. A Qt based CDisplayEx in short.

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  • Is excessive DataTable usage bad?

    - by Justin R.
    I was recently asked to assist another team in building an ASP .NET website. They already have a significant amount of code written -- I was specifically asked build a few individual pages for the site. While exploring the code for the rest of the site, the amount of DataTables being constructed jumped out at me. Being a relatively new in the field, I've never worked on an application that utilizes a database as much as this site does, so I'm not sure how common this is. It seems that whenever data is queried from our database, the results are stored in a DataTable. This DataTable is then usually passed around by itself, or it's passed to a constructor. Classes that are initialized with a DataTable always assign the DataTable to a private/protected field, however only a few of these classes implement IDisposable. In fact, in the thousands of lines of code that I've browsed so far, I have yet to see the Dispose method called on a DataTable. If anything, this doesn't seem to be good OOP. Is this something that I should worry about? Or am I just paying more attention to detail than I should? Assuming you're most experienced developers than I am, how would you feel or react if someone who was just assigned to help you with your site approached you about this "problem"?

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  • Boost any usage

    - by Ockonal
    Hello, how can I insert my own class objects into ptr_map from boost. The objects are templated so I can't use some static typename in the map. So I did: ptr_map<string, any> someMap; My class inherits the boost::noncopyable. someMap.insert("Test", new MyClass()); The error is: error: no matching function for call to ‘boost::ptr_map.

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