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• Database and logic layer for ASP.NET MVC application

  - by Ismail

  I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern as it allows to apply filter in logic layer rather than in data access layer. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right? So questions basically are - Is MySQL to Linq possible? If yes where can I get more details on it? Pros and cons of using EntityFramework with MySQL? Will it be easy to access data using EntityFramework with MySQL? Will I be able to implement repository patter which allows applying filter in logic layer rather than data access layer (when I use EntityFramework with MySQL) Does it fetches hell lot of data from database and then apply filter on it? If it sounds too many questions from my side in that case, if you can just let me know what you will do (with a considerable reason) in this situation as an experienced person in this area, that should answer my question.

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• VB.NET switching from ADO.NET to LINQ

  - by Cj Anderson

  I'm VERY new to Linq. I have an application I wrote that is in VB.NET 2.0. Works great, but I'd like to switch this application to Linq. I use ADO.NET to load XML into a datatable. The XML file has about 90,000 records in it. I then use the Datatable.Select to perform searches against that Datatable. The search control is a free form textbox. So if the user types in terms it searches instantly. Any further terms that are typed in continue to restrict the results. So you can type in Bob, or type in Bob Barker. Or type in Bob Barker Price is Right. The more criteria typed in the more narrowed your result. I bind the results to a gridview. Moving forward what all do I need to do? From a high level, I assume I need to: 1) Go to Project Properties -- Advanced Compiler Settings and change the Target framework to 3.5 from 2.0. 2) Add the reference to System.XML.Linq, Add the Imports statement to the classes. So I'm not sure what the best approach is going forward after that. I assume I use XDocument.Load, then my search subroutine runs against the XDocument. Do I just do the standard Linq query for this sort of repeated search? Like so: var people = from phonebook in doc.Root.Elements("phonebook") where phonebook.Element("userid") = "whatever" select phonebook; Any tips on how to best implement?

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• Sharing storage between servers

  - by El Yobo

  I have a PHP based web application which is currently only using one webserver but will shortly be scaling up to another. In most regards this is pretty straightforward, but the application also stores a lot of files on the filesystem. It seems that there are many approaches to sharing the files between the two servers, from the very simple to the reasonably complex. These are the options that I'm aware of Simple network storage NFS SMB/CIFS Clustered filesystems Lustre GFS/GFS2 GlusterFS Hadoop DFS MogileFS What I want is for a file uploaded via one webserver be immediately available if accessed through the other. The data is extremely important and absolutely cannot be lost, so whatever is implemented needs to a) never lose data and b) have very high availability (as good as, or better, than a local filesystem). It seems like the clustered filesystems will also provide faster data access than local storage (for large files) but that isn't of vita importance at the moment. What would you recommend? Do you have any suggestions to add or anything specifically to look out for with the above options? Any suggestions on how to manage backup of data on the clustered filesystems?

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• call addsubview again causes slowdown

  - by Tom

  hi guys, i am writing a little music-game for the iphone. I am almost done, this is the only issue which keeps me from rolling it out. any help to solve this is much appreciated. this is what i do: at my appDelegate I add my menu-view-screen to the window. the menu-view-screen acts as a container and controls which view gets presented to the user. means, on the menu-view-screen I got 4 buttons (new game, options, faq, highscore). when the user clicks on a button something as this happens: if (self.gameViewController == nil) { GameViewController *viewController = [[GameViewController alloc] initWithNibName:@"GameViewController" bundle:nil]; self.gameViewController = viewController; [viewController release]; } [self.view addSubview:self.gameViewController.view]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleSwitchViewNotificationFromGameView:) name:@"SwitchView" object:gameViewController]; when the user returns to the menu, this piece of code gets executed: [[NSNotificationCenter defaultCenter] removeObserver:self]; [self.gameViewController viewWillDisappear:YES]; [self.gameViewController.view removeFromSuperview]; this works fine for all screens but not for the gamescreen(well this is the only one with heaps of user-interaction) means the responsiveness of the iphone(when playing tones) gets really slow. The performance is fine when I display the gameview for the first time. it starts getting slower as soon as I add it to the menu-views-container-subviews again (addsubview) (basically open up a new game) any ideas what causes(or to get around) this? thanks heaps Best regards Tom

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• SQL Server becomes slow after restart

  - by Tobi DM

  We use SQL Server 2005 on an Windwos Server 2008. Ther Server has 48 GB RAM. SQL Server is configured to use 40 GB RAM. There is only one database hosted (About 70 GB). The only app beside SQL Server is our App-Server which connects the clients to the database. Now we encounter the following problem: After a restart of the server our the performance is great. The server grabs the 40 GB RAM wich it is allowed to and then runs fast as hell. But after about 4 weeks the system becomes slower and slower. The execution of statements (seen in the profiler) is raising slowly. But I cannot see that there is something going wrong on the server. CPU usage is at about 20% I/O also seems to be no Problem The process monitor does also not show that there are strange apps or something like that. Eventlog does also have no interessting messages No open transactions or blockings to see We tried already the following things without effect: Droped the cache by using the statements DBCC FreeProcCache DBCC FREESYSTEMCACHE('ALL') DBCC DropCleanbuffers Restarted the Appserver we are using. Restart the sql server service But nothing did help exept restarting the whole server. Any ideas?

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• Redirect uploaded files to another server, using nginx

  - by Serg ikS

  I am creating a web service of scheduled posts to some soc. network.Need help dealing with file uploads under high traffic. Process overview: User uploads files to SomeServer (not mine). SomeServer then responds with a JSON string. My web app should store that JSON response. Opt. 1 — Save, cURL POST, delete tmp The stupid way I made it work: User uploads files to MyWebApp; MyWebApp cURL's the file further to SomeServer, getting the response. Opt.2 — JS magic The smart way it could be perfect: User uploads the file directly to SomeServer, from within an iFrame; MyWebApp gets the response through JavaScript. But this is(?) impossible due to the 'Same Origin Policy', isn't it? Opt. 3 — nginx proxying? The better way for a production server: User uploads files to MyWebApp; nginx intercepts the file uploads and sends them directly to the SomeServer; JSON response is also intercepted by nginx and processed by MyWebApp. Does this make any sense, and what would be the nginx config for, say, /fileupload Location to proxy it to SomeServer ?

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• ISO/IEC Website and Charging for C and C++ Standards

  - by Michael Aaron Safyan

  The ISO C Standard (ISO/IEC 9899) and the ISO C++ Standard (ISO/IEC 14882) are not published online; instead, one must purchase the PDF for each of those standards. I am wondering what the rationale is behind this... is it not detrimental to both the C and C++ programming languages that the authoritative specification for these languages is not made freely available and searchable online? Doesn't this encourage the use of possibly inaccurate, non-authoritative sources for information regarding these standards? While I understand that much time and effort has gone into developing the C and C++ standards, I am still somewhat puzzled by the choice to charge for the specification. The OpenGroup Base Specification, for example, is available for free online; they make money buy charging for certification. Does anyone know why the ISO standards committees don't make their revenue in certifying standards compliance, instead of charging for these documents? Also, does anyone know if the ISO standards committee's atrociously looking website is intentionally made to look that way? It's as if they don't want people visiting and buying the spec. One last thing... the C and C++ standards are generally described as "open standards"... while I realize that this means that anyone is permitted to implement the standard, should that definition of "open" be revised? Charging for the standard rather than making it openly available seems contrary to the spirit of openness. P.S. I do have a copy of the ISO/IEC 9899:1999 and ISO/IEC 14882:2003, so please no remarks about being cheap or anything... although if you are tempted to say such things, you might want to consider the high school, undergraduate, and graduate students who might not have all that much extra cash. Also, you might want to consider the fact that the ISO website is really sketchy and they don't even tell you the cost until you proceed to the checkout... doesn't really encourage one to go and get a copy, now does it?

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• (x86) Assembler Optimization

  - by Pindatjuh

  I'm building a compiler/assembler/linker in Java for the x86-32 (IA32) processor targeting Windows. High-level concepts of a "language" (in essential a Java API for creating executables) are translated into opcodes, which then are wrapped and outputted to a file. The translation process has several phases, one is the translation between languages: the highest-level code is translated into the medium-level code which is then translated into the lowest-level code (probably more than 3 levels). My problem is the following; if I have higher-level code (X and Y) translated to lower-level code (x, y, U and V), then an example of such a translation is, in pseudo-code: x + U(f) // generated by X + V(f) + y // generated by Y (An easy example) where V is the opposite of U (compare with a stack push as U and a pop as V). This needs to be 'optimized' into: x + y (essentially removing the "useless" code) My idea was to use regular expressions. For the above case, it'll be a regular expression looking like this: x:(U(x)+V(x)):null, meaning for all x find U(x) followed by V(x) and replace by null. Imagine more complex regular expressions, for more complex optimizations. This should work on all levels. What do you suggest? What would be a good approach to optimize in these situations?

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• Toggling between instances of NiftyPlayer on a page - won't stop playing when hidden on IE

  - by Ashley

  Hi, i've got a page with links to MP3s, when the link is clicked I use javascript to show a small Flash player (NiftyPlayer) under the link. When a different link is clicked, the old player is hidden and the new player is revealed. The player auto-starts when the element is shown, and auto-stops when hidden - in Firefox. In IE it will only auto-start and NOT auto-stop. This is what I would like to solve. This is an example HTML with link and player <a href="Beat The Radar - Misunderstood What You Said.mp3" onclick="toggle_visibility('player662431');return false;" class="mp3caption">Misunderstood What You Said</a> <div id="player662431" class="playerhide"><embed src="http://www.xxx.com/shop/flash/player.swf?file=/mp3/Beat The Radar - Misunderstood What You Said.mp3&as=1" quality="high" bgcolor="#000000" width="161" height="13" name="niftyPlayer662431" align="" type="application/x-shockwave-flash" swLiveConnect="true" pluginspage="http://www.macromedia.com/go/getflashplayer"></embed> Here is the javascript (i've got jquery installed to let me hide all the open players on this page apart from the new one) function toggle_visibility(id) { $('.playerhide').hide(); var e = document.getElementById(id); e.style.display = 'block'; } I think what I need to do is start the player manually with javascript (rather than using the autostart as=1 function in the URL string) There is some javascript that comes with NiftyPlayer to allow this EG niftyplayer('niftyPlayer1').play() there is also a stop method. I need some help with javascript - how do I add this call to play into my toggle_visibility function (it has the same unique ID number added to the name of the player as the ID of the div that's being shown, but I don't know how to pull this ID number out of one thing and put it in another) I also would like to be able to do niftyplayer('niftyPlayer1').stop() to stop the audio of the previously running player. Is it possible to store the current ID number somewhere and call it back when needed? Thanks for the help, i'm a PHP programmer who needs some support with Javascript - I know what I want to achieve, just don't know the commands to do it! Thanks

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• How do the size standard libraries compare for different languages

  - by Roman A. Taycher

  Someone was recently raving about how great jQuery was and how it made javascript into a pleasure and also how the whole source code was so small(and one file). I looked it up on www.ohloh.net/ and it said it was about 30,000 lines of javascript, when I tired curl piped to wc it said about 5000 lines(strange discrepancy that, maybe test suites, ect?). I thought well it isn't that strange since javascript from what I've heard has a lot of fun dynamic tricks, so you can probably get away with a small library. But then I thought what about other high level languages, the ones with large standard libraries and wondered how big the standard are for python/ruby/haskell/pharo(smalltalk)/*ml/ect. (libraries not vm stuff to the degree its possible to separate it) Anybody know? Any details (comment/blank/code lines , test code lines, lines in language vs lines in ffi/byte-code) are appreciated! edit: ps. since it started this me asking about jQuery as a bonus if you could please list the size of mega frameworks, a megaframewok provides so much that people using an x megaframework in language y might sometimes refer to programming in xy or even x rather then in y (ie. : qt, jQuery, etc.).

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• OpenGL equivalent of GDI's HatchBrush or PatternBrush?

  - by Ptah- Opener of the Mouth

  I have a VB6 application (please don't laugh) which does a lot of drawing via BitBlt and the standard VB6 drawing functions. I am running up against performance issues (yes, I do the regular tricks like drawing to memory). So, I decided to investigate other ways of drawing, and have come upon OpenGL. I've been doing some experimenting, and it seems straightforward to do most of what I want; the application mostly only uses very simple drawing -- relatively large 2D rectangles of solid colors and such -- but I haven't been able to find an equivalent to something like a HatchBrush or PatternBrush. More specifically, I want to be able to specify a small monochrome pixel pattern, choose a color, and whenever I draw a polygon (or whatever), instead of it being solid, have it automatically tiled with that pattern, not translated or rotated or skewed or stretched, with the "on" bits of the pattern showing up in the specified color, and the "off" bits of the pattern left displaying whatever had been drawn under the area that I am now drawing on. Obviously I could do all the calculations myself. That is, instead of drawing as a polygon which will somehow automatically be tiled for me, I could calculate all of the lines or pixels or whatever that actually need to be drawn, then draw them as lines or pixels or whatever. But is there an easier way? Like in GDI, where you just say "draw this polygon using this brush"? I am guessing that "textures" might be able to accomplish what I want, but it's not clear to me (I'm totally new to this and the documentation I've found is not entirely obvious); it seems like textures might skew or translate or stretch the pattern, based upon the vertices of the polygon? Whereas I want the pattern tiled. Is there a way to do this, or something like it, other than brute force calculation of exactly the pixels/lines/whatever that need to be drawn? Thanks in advance for any help.

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• Download Current WSJ.com Prime Rate

  - by Registered User

  I need to automatically download the current Wall Street Journal Prime Rate and load the data into my database. What is the best method for downloading this data automatically? I have come up with three possible solutions for doing this: Scrape a HTML web page from WSJ. Parse a RSS news feed from WSJ. Use some API that I haven't found from WSJ. Regarding solution 1, although I don't like solution 1 since it could easily break, it's the only one that I have worked out from end to end. It appears I can scrape this page with a WebRequest / WebResponse and read the text in this code: <tr> <td style="text-align:left" class="colhead">&nbsp;</td> <td class="colhead">Latest</td> <td class="colhead">Wk ago</td> <td class="colhead">High</td> <td class="colhead">Low</td> </tr> <tr> <td class="text">U.S.</td> <td style="font-weight:bold;" class="num">3.25</td> <td class="num">3.25</td> <td class="num">3.25</td> <td class="num" style="border-right:0px">3.25</td> </tr> Regarding solution 2, although I can implement a RSS reader solution, I don't see a way to reliably anticipate verbiage for changes in the Prime Rate. Therefore, I don't think this is as safe or reliable a way to get the data as solution 1. Regarding solution 3, I haven't found any published API's for checking money rates like the Prime Rate. If anyone knows of a web service or other API for checking money rates, then please let me know.

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• Ultra-Portable Laptop or Tablet PC for Development and Sketching

  - by Nelson LaQuet

  I am a software developer that primarily writes in PHP, [X]HTML, CSS, Javascript, C# and C++. I use Eclipse for web development, Visual Studio 2008 for C++ and C# work, TortoiseSVN, Subversion server for local repositories, SQL Server Express, Apache and MYSQL. I also use Office 2007 for word processing and spreadsheets and use Vista Ultimate 64 as my primary operating system. The only other things I do on my laptop are watch movies, surf the internet and listen to music. I currently have a Acer Aspire 5100 (1.4 GHz AMD Turion X2, 2 GB of RAM and a 15.4" screen). This thing does not cut it in performance or portability, and in addition, my DVD drive failed. And before anybody posts about vista: I have had XP Professional 32 on it for the last two years, and recently upgraded to Vista 64. It is actually faster (with areo disabled) then XP; so it is not the OS that is causing the laptop to be slow. I usually sketch a lot, for explaining things, developing user interfaces and software architecture. Because of my requirements, I was thinking about a Lenovo X61 Tablet PC. It outperforms my current laptop, is significantly more portable, and... is a tablet. My question is: do any other software developers use this (or other tablets) for programming? Does it help to be able to sketch on the computer itself? And is it capable of being a good development machine? Will it handle the above software listed? If not, what is the best ultra-portable laptop that is good for programming? Or are ultra-portable laptops even good for programming? I could manage with my 15.4" screen, but am spoiled by my two 19" at my home desktop and my job's workstation.

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• passing groups of properties from 1 class to another

  - by insanepaul

  I have a group of 13 properties in a class. I created a struct for these properties and passed it to another class. I need to add another 10 groups of these 13 properties. So thats 130 properties in total. What do I do? I could add all 130 properties to the struct. Will this affect performance and readability I could create a list of structs but don't know how to access an item eg. to add to the list: listRowItems.Add(new RowItems(){a=1, b=1, c=1, d=1...}); listRowItems.Add(new RowItems(){a=2, b=2, c=2, d=2...}); How do I access the second group item b? is it Could I use just a dictionary with 130 items Should I use a list of dictionaries (again I don't know how to access a particular item) Should I pass in a class of 130 properties Just for your interest the properties are css parameters used for a composite control. The control displays 13 elements in each row and there are 10 rows and each row is customisable.

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• How to perform a binary search on IList<T>?

  - by Daniel Brückner

  Simple question - given an IList<T> how do you perform a binary search without writing the method yourself and without copying the data to a type with build-in binary search support. My current status is the following. List<T>.BinarySearch() is not a member of IList<T> There is no equivalent of the ArrayList.Adapter() method for List<T> IList<T> does not inherit from IList, hence using ArrayList.Adapter() is not possible I tend to believe that is not possible with build-in methods, but I cannot believe that such a basic method is missing from the BCL/FCL. If it is not possible, who can give the shortest, fastest, smartest, or most beatiful binary search implementation for IList<T>? UPDATE We all know that a list must be sorted before using binary search, hence you can assume that it is. But I assume (but did not verify) it is the same problem with sort - how do you sort IList<T>? CONCLUSION There seems to be no build-in binary search for IList<T>. One can use First() and OrderBy() LINQ methods to search and sort, but it will likly have a performance hit. Implementing it yourself (as an extension method) seems the best you can do.

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• What is the the relation between programming and mathematics?

  - by Math Grad

  Programmers seem to think that their work is quite mathematical. I understand this when you try to optimize something in performance, find the most efficient alogithm, etc.. But it patently seems false when you look at a billing application for a shop, or a systems software riddled with I/O calls. So what is it exactly? Is computation and associated programming really mathematical? Here I have in mind particularly the words of the philosopher Schopenhauer in mind: That arithmetic is the basest of all mental activities is proved by the fact that it is the only one that can be accomplished by means of a machine. Take, for instance, the reckoning machines that are so commonly used in England at the present time, and solely for the sake of convenience. But all analysis finitorum et infinitorum is fundamentally based on calculation. Therefore we may gauge the “profound sense of the mathematician,” of whom Lichtenberg has made fun, in that he says: “These so-called professors of mathematics have taken advantage of the ingenuousness of other people, have attained the credit of possessing profound sense, which strongly resembles the theologians’ profound sense of their own holiness.” I lifted the above quote from here. It seems that programmers are doing precisely the sort of mechanized base mental activity the grand old man is contemptuous about. So what exactly is the deal? Is programming really the "good" kind of mathematics, or just the baser type, or altogether something else just meant for business not to be confused with a pure discipline?

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• Netlogo: error when putting variable in table, only constants allowe??

  - by Chantal

  Hello, Currently I am working on a Netlogo program where I need to use nodes and links for vehicle routing problem. (links are called streets in the program) Here I have some practical problems of how to input variable linkspeed in a table with another node. Constants like 200 etc are fine. Online I found some examples where variables are used, but I do not know why I keep getting the following error: Expected a constant. (or why netlogo expects a constant) Here is the relevant piece of code: extensions [table] streets-own [linkspeed linktoll] nodes-own [netw] ;; In another piece of code linkspeed is assigned successfully to the links to cheapcalc ;; start conditions set costs very high 300000 ;; state 3 unsearched state 2 searching state 1 searched (for later purposes) ask nodes [ set i 0 set j count nodes set netw table:make while [i < j][ table:put netw (i) [3000000 3] set i (i + 1)]] set i 0 let k 0 ask node 35 ;; here i use node 35 as an example. ;; node 35 is connected to node 34, 36, 20 and 50 [table:put netw (35) [0 1] ;; node need to search costs to travel to itself ;; putting constants is ok. while [i < j] [ask my-links [ask both-ends [if (who != 35) [set color blue ;; set temp ([linkspeed] of street 35 who) ;; here my real goal is to put this in stat of i. but i is easier than linkspeed. table:put netw (who) [ i 2 ] ] ] ] set i (i + 1)] ] ;; next node for later, no it is just repetition of the same. end I hope somebody knows what is going on... Kind regards, Chantal

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• gcc, strict-aliasing, and horror stories

  - by Joseph Quinsey

  In http://stackoverflow.com/questions/2906365/gcc-strict-aliasing-and-casting-through-a-union I asked whether anyone had encountered problems with union punning through pointers. So far, the answer seems to be No. This question is broader: do you have any horror stories about gcc and strict-aliasing? Background: Quoting from AndreyT's answer in http://stackoverflow.com/questions/2771023/c99-strict-aliasing-rules-in-c-gcc/2771041#2771041: "Strict aliasing rules are rooted in parts of the standard that were present in C and C++ since the beginning of [standardized] times. The clause that prohibits accessing object of one type through a lvalue of another type is present in C89/90 (6.3) as well as in C++98 (3.10/15). ... It is just that not all compilers wanted (or dared) to enforce it or rely on it." Well, gcc is now daring to do so, with its -fstrict-aliasing switch. And this has caused some problems. See, for example, the excellent article http://davmac.wordpress.com/2009/10/ about a Mysql bug, and the equally excellent discussion in http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html. Some other less-relevant links: http://stackoverflow.com/questions/1225741/performance-impact-of-fno-strict-aliasing http://stackoverflow.com/questions/754929/strict-aliasing http://stackoverflow.com/questions/262379/when-is-char-safe-for-strict-pointer-aliasing http://stackoverflow.com/questions/725138/how-to-detect-strict-aliasing-at-compile-time So to repeat, do you have a horror story of your own? Problems not indicated by -Wstrict-aliasing would, of course, be preferred. And other C compilers are also welcome.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• Interface for reading variable length files with header and footer.

  - by John S

  I could use some hints or tips for a decent interface for reading file of special characteristics. The files in question has a header (~120 bytes), a body (1 byte - 3gb) and a footer (4 bytes). The header contains information about the body and the footer is only a simple CRC32-value of the body. I use Java so my idea was to extend the "InputStream" class and add a constructor such as "public MyInStream( InputStream in)" where I immediately read the header and the direct the overridden read()'s the body. Problem is, I can't give the user of the class the CRC32-value until the whole body has been read. Because the file can be 3gb large, putting it all in memory is a be an idea. Reading it all in to a temporary file is going to be a performance hit if there are many small files. I don't know how large the file is because the InputStream doesn't have to be a file, it could be a socket. Looking at it again, maybe extending InputStream is a bad idea. Thank you for reading the confused thoughts of a tired programmer. :)

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• Ajax heavy JS apps using excessive amounts of memory over time.

  - by Shane Reustle

  I seem to have some pretty large memory leaks in an app that I am working on. The app itself is not very complex. Every 15 seconds, the page requests approx 40kb of JSON from the server, and draws a table on the page using it. It is cheaper to draw the table over because the data is usually always new. I am attaching a few events to the table, approx 5 per line, 30 lines in the table. I used jQuery's .html() method to put the new html into the container and overwrite the existing. I do this specifically so that jQuery's special cleanup functions go in and attempt to detach all events on the elements in the element that it is overwriting. I then also delete the large variables of html once they are sent to the DOM using delete my_var. I have checked for circular references and attached events that are never cleared a few times, but never REALLY dug into it. I was wondering if someone could give me a few pointers on how to optimize a very heavy app like this. I just picked up "High Performance Javascript" by Nicholas Zakas, but didn't have much time to get into it yet. To give an idea on how much memory this is using, after 4~ hours, it is using about 420,000k on chrome, and much more on Firefox or IE. Thanks!

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• lost session after redirect_to

  - by PeterWong

  I encountered a strange performance in my current project, which is about session. The strange part is it was normal in Safari but failed in other browsers (includes chrome, firefox and opera). There is a registration form for input of part of the key information (email, password, etc) and is submitted to an action called "create" This is the basic code of create action: @account = Account.new(params[:account]) if @account.save ApplicationController.current_account = @account session[:current_account] = ApplicationController.current_account session[:account] = ApplicationController.current_account.id email = @account.email Mailer.deliver_account_confirmation(email) flash[:type] = "success" flash[:notice] = "Successfully Created Account" redirect_to :controller => "accounts", :action => "create_step_2" else flash[:type] = "error" flash[:title] = "Oops, something wasn't right." flash[:notice] = "Mistakes are marked below in red. Please fix them and resubmit the form. Thanks." render :action => "new" end Also I created a before_filter in the application controller, which has the following code: ApplicationController.current_account = Account.find_by_id(session[:current_account].id) unless session[:current_account].blank? For Safari, there is no any problem. But for the other browsers, the session[:current_account] does not exist and so produced the following error message: RuntimeError in AccountsController#create_step_2 Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id Please could anyone help me?

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• Creating Mobile Cross-Platform Scripting Solution

  - by Aplomb

  I am having the dream to design a Mobile cross-platform scripting solution to achieve Developer only need to code once by scripting language(it's possible be Javascript or others need further investigation), then the solution will be able to generate the installation files for multiple mobile platforms like J2me, Android, Symbian, BlackBerry, Palm, Windows Mobile/Phone, iPhone, etc. Using the scripting language, developer can code with unified platform API. And other extension frameworks under scripting language, like, 1. 2D UI framework Most probably using for Mobile Applications, the UI style will compete with native UI framework and no longer every application in particular platform looks similar. 2. 3D UI framework Provide the platforms who has 3D capability can represent their Mobile Application with more fashion 3D style which will be much more abstractive. 3. Variable game engine Developers can can use it for easily and high-quality build games. 4. etc This Mobile solution is providing three points, 1. Cross-Platform 2. Scripting 3. Middleware So guys, what do you think about this idea, is it good for Developers? is it profitable? where is the better direction for this idea?

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• Returning large collections from WCF Serivce

  - by Nate Bross

  I'm trying to determine the best approach for building a WCF Service, and the area I'm struggling with most is returning lists of objects. The built-in maxMessageSize of 64k seems pretty high, and I really don't want to bump it up (quick googling finds 100s of places bumping the maxMessageSize up to multi-gigabyte range which seems foolish). But, when I'm returning a collection of objects (~150 items) I am exceeding the default 64k. I'm almost to the point of returning my own class which inherits IEnumerable and has properties for hasNext, hasPrevious and PageSize so that I can implement paging on the client side -- this seems like alot of code. The other option is to jackup the maxMessageSize and hope for the best, but that feels wrong. All other aspects of my service are working great, its just returning large collectiosn where I'm having issues. For background, there are two types of consumers of this service, UI applications which will be primarly web and/or wpf applications, and data processing applications, .NET console apps, and maybe some other non-UI apps. For the UI applications, I would like to keep them responsive and keep the messageSize low, on the console apps it doesn't matter as much as they are just pulling data down to do processing and push it back up to the service.

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• Collapsing data frame by selecing one row per group

  - by jkebinger

  I'm trying to collapse a data frame by removing all but one row from each group of rows with identical values in a particular column. In other words, the first row from each group. For example, I'd like to convert this > d = data.frame(x=c(1,1,2,4),y=c(10,11,12,13),z=c(20,19,18,17)) > d x y z 1 1 10 20 2 1 11 19 3 2 12 18 4 4 13 17 Into this: x y z 1 1 11 19 2 2 12 18 3 4 13 17 I'm using aggregate to do this currently, but the performance is unacceptable with more data: > d.ordered = d[order(-d$y),] > aggregate(d.ordered,by=list(key=d.ordered$x),FUN=function(x){x[1]}) I've tried split/unsplit with the same function argument as here, but unsplit complains about duplicate row numbers. Is rle a possibility? Is there an R idiom to convert rle's length vector into the indices of the rows that start each run, which I can then use to pluck those rows out of the data frame?

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