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• Thrift,.NET,Cassandra - Is this is right combination?

  - by Vadi

  I've been evaluating technology stack for developing a social network based application. Below are the stack I think could well suitable for this application type of application: GUI -- ASP.NET MVC, Flash (Flex) Business Services -- Thrift based services One of the advantage of using Thrift is to solve scaling problems that will come in future when the user base increases rapidly. All the business logic can be exposed as a services using REST,JSON etc., This also allows us to go with C++ or Erlang based services when situation demands. Database -- mySQL, CasSandara mySQL can be used for storing the data which needs to be persisted. Cassandara will be used for storing global identifiers to the persisted data. Since Cassandara is also very good at scaling by introducing more nodes this will leverage Thrift based services as well. And also there is native support between Cassandara and Thrift Cache Server -- Memcached Any requests from Business Services will only talk to Memcached if any non-dirty data is required, otherwise there will be some background jobs that will invalidate the cache from database. The question is: Is the Thrift which is open-sourced one is production-ready? Is it the right stack for services layer to choose when the application (GUI) is primarily gets developed in ASP.NET and DB is mysql? Is there any other caveats that anyone here experienced? One of the main objective behind this stack is to easily scale up with more nodes and also this helps us to use Linux boxes, it will reduce our cost significantly Thoughts please ..

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• sitemesh vs jsp-config (<include-prelude>)

  - by Nrj

  Please help clarifying : In web.xml I have the following <jsp-config> <jsp-property-group> <url-pattern>*.jsp</url-pattern> <el-ignored>false</el-ignored> <page-encoding>utf-8</page-encoding> <include-prelude>/jstlTaglibs.jspf</include-prelude> </jsp-property-group> </jsp-config> Also in decorators.xml I have <decorator name="footer" page="footer.jsp"> <pattern>*.action</pattern> </decorator> which is used via sitemesh.xml. The footer.jsp which says ... <decorator:body /> <@include .. "footer.jsp"/> So what I gather is, both of the codes above in a sense inject some jspf. Please help highlighting the differences and benefits of both the approaches. Also which one is more used across industry ?

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• Looking for a good world map generation algorithm

  - by FalconNL

  I'm working on a Civilization-like game and I'm looking for a good algorithm for generating Earth-like world maps. I've experimented with a few alternatives, but haven't hit on a real winner yet. One option is to generate a heightmap using perlin noise and add water at a level so that about 30% of the world is land. While perlin noise (or similar fractal-based techniques) are frequently used for terrain and is reasonably realistic, it doesn't offer much in the way of control over the number, size and position of the resulting continents, which I'd like to have from a gameplay perspective. See http://farm3.static.flickr.com/2792/4462870263_ff26c40365_o.jpg for an example (sorry, can't post pictures yet). A second option is to start with a randomly positioned one-tile seed (I'm working on a grid of tiles), determine the desired size for the continent and each turn add a tile that is horizontally or vertically adjacent to the existing continent until you've reached the desired size. Repeat for the other continents. This technique is part of the algorithm used in Civilization 4. The problem is that after placing the first few continents, it's possible to pick a starting location that's surrounded by other continents, and thus won't fit the new one. Also, it has a tendency to spawn continents too close together, resulting in something that looks more like a river than continents. See http://farm5.static.flickr.com/4069/4462870383_46e86b155c_o.jpg for an example. Does anyone happen to know a good algorithm for generating realistic continents on a grid-based map while keeping control over their number and relative sizes?

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• Visual Studio 2008 Preprocessor wierdness

  - by Canacourse

  We have set-up a simple versioning system for our builds to ensure the built files always indicate whether they are Beta Debug or Beta Release builds I moved the file version info to to myapp.rc2 and created version.h // version.h // _DEBUG is defined by VS #define _BETA #ifdef _BETA #define FILE_DESC1 _T("BETA ") #else #define FILE_DESC1 // blank on purpose #endif #ifdef _DEBUG #define FILE_DESC2 _T("Debug Version ") #else #define FILE_DESC2 _T("Release Version ") // this is greyed out in the ide when building #endif #define FILE_DESC FILE_DESC1 FILE_DESC2 // myapp.rc2 include "version.h" #ifndef _T #define _T(x) x #endif VS_VERSION_INFO VERSIONINFO FILEVERSION PROD_VER_MJR,PROD_VER_MIN,PROD_VER_UPD,JOBUILDER_BUILD PRODUCTVERSION PROD_VER_MJR,PROD_VER_MIN FILEFLAGSMASK 0x3fL #ifdef _DEBUG FILEFLAGS 0x1L #else FILEFLAGS 0x0L #endif FILEOS 0x4L FILETYPE 0x1L FILESUBTYPE 0x0L BEGIN BLOCK "StringFileInfo" BEGIN BLOCK "040904e4" BEGIN VALUE "CompanyName", COMPANY_NAME VALUE "FileDescription", FILE_DESC VALUE "FileVersion", JOBBUI_VERSION VALUE "InternalName", "MyApp.exe" VALUE "LegalCopyright", COPYRIGHT VALUE "OriginalFilename", "MyApp.exe" VALUE "ProductName", PRODUCT_NAME VALUE "ProductVersion", PRODUCT_VERSION VALUE "Comments", COMMENTS END END BLOCK "VarFileInfo" BEGIN VALUE "Translation", 0x409, 1252 END END However when the exe is built in the debug output directory the file description always incorrectly says "BETA Release Version" instead of "BETA Debug Version" Yet the IDE indicates that "#define FILE_DESC2 _T("Debug Version ")" would be used. Why might this be? I have used these files on another project and they work correctly. Thank You...

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• Source-to-source compiler framework wanted

  - by cheungcc_2000

  Dear all, I used to use OpenC++ (http://opencxx.sourceforge.net/opencxx/html/overview.html) to perform code generation like: Source: class MyKeyword A { public: void myMethod(inarg double x, inarg const std::vector<int>& y, outarg double& z); }; Generated: class A { public: void myMethod(const string& x, double& y); // generated method below: void _myMehtod(const string& serializedInput, string& serializedOutput) { double x; std::vector<int> y; // deserialized x and y from serializedInput double z; myMethod(x, y, z); } }; This kind of code generation directly matches the use case in the tutorial of OpenC++ (http://www.csg.is.titech.ac.jp/~chiba/opencxx/tutorial.pdf) by writing a meta-level program for handling "MyKeyword", "inarg" and "outarg" and performing the code generation. However, OpenC++ is sort of out-of-date and inactive now, and my code generator can only work on g++ 3.2 and it triggers error on parsing header files of g++ of higher version. I have looked at VivaCore, but it does not provide the infra-structure for compiling meta-level program. I'm also looking at LLVM, but I cannot find documentation that tutor me on working out my source-to-source compilation usage. I'm also aware of the ROSE compiler framework, but I'm not sure whether it suits my usage, and whether its proprietary C++ front-end binary can be used in a commercial product, and whether a Windows version is available. Any comments and pointers to specific tutorial/paper/documentation are much appreciated.

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• QPrinter, QPrintDialog giving errors not encountered in code examples

  - by karunesh

  In the imageviewer example, QPainter and QPrintDialog objects are defined and used as following: #ifndef QT_NO_PRINTER QPrinter printer; #endif and QPrintDialog dialog(&printer, this); A QPainter object is then initialized with QPrinter (printer). When I tried to use the same code in my function, it looks like: void imageviewer::print() { ... #ifdef QT_NO_PRINTER QPrinter printer(this); //ERROR 1 QPrintDialog dialog(&printer, this);//ERROR 2 and 3 if (dialog.exec()) //ERROR 4 { //do the painting } #endif } The errors are: 1. variable 'QPrinter printer' has initializer but incomplete type 2. 'QPrintDialog' was not declared in this scope 3. Expected ';' before 'dialog' 4. 'dialog' was not declared in this scope What I am notable to understand is why are these errors arising when I am using them in my code, but not in the example. As a friend pointed out, I made sure that I used the right #include files and made sure that 'printer' and 'dialog' were not touched anywhere else in the example.

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• Scrapy issue with iTunes' AppStore

  - by Eric

  I am using Scrapy to fetch some data from iTunes' AppStore database. I start with this list of apps: http://itunes.apple.com/us/genre/mobile-software-applications/id36?mt=8 In the following code I have used the simplest regex which targets all apps in the US store. from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor from scrapy.contrib.spiders import CrawlSpider, Rule class AppStoreSpider(CrawlSpider): domain_name = 'itunes.apple.com' start_urls = ['http://itunes.apple.com/us/genre/mobile-software-applications/id6015?mt=8'] rules = ( Rule(SgmlLinkExtractor(allow='itunes\.apple\.com/us/app'), 'parse_app', follow=True, ), ) def parse_app(self, response): .... SPIDER = AppStoreSpider() When I run it I receive the following: [itunes.apple.com] DEBUG: Crawled (200) <GET http://itunes.apple.com/us/genre/mobile-software-applications/id6015?mt=8> (referer: None) [itunes.apple.com] DEBUG: Filtered offsite request to 'itunes.apple.com': <GET http://itunes.apple.com/us/app/bloomberg/id281941097?mt=8> As you can see, when it starts crawling the first page it says: "Filtered offsite request to 'itunes.apple.com'". and then the spider stops.. it also returns this message: [ScrapyHTTPPageGetter,client] /usr/lib/python2.5/cookielib.py:1577: exceptions.UserWarning: cookielib bug! Traceback (most recent call last): File "/usr/lib/python2.5/cookielib.py", line 1575, in make_cookies parse_ns_headers(ns_hdrs), request) File "/usr/lib/python2.5/cookielib.py", line 1532, in _cookies_from_attrs_set cookie = self._cookie_from_cookie_tuple(tup, request) File "/usr/lib/python2.5/cookielib.py", line 1451, in _cookie_from_cookie_tuple if version is not None: version = int(version) ValueError: invalid literal for int() with base 10: '"1"' I have used the same script for other website and I didn't have this problem. Any suggestion?

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• Problem trying to install PyCurl on Mac Snow Leopard

  - by Ldn

  Hi, My app needs to use PyCurl, so i tried to install it on my Mac but i found a lot of problems and error :( Requirement: First of all i've to say that the version of Python working on my Mac is 32 bit based, because i need to use WxPython, that needs 32 bit Python. For doing this i used: defaults write com.apple.versioner.python Prefer-32-Bit -bool yes To install PyCurl i used: sudo env ARCHFLAGS="-arch x86_64" easy_install setuptools pycurl And the terminal returned: Best match: setuptools 0.6c11 Processing setuptools-0.6c11-py2.6.egg setuptools 0.6c11 is already the active version in easy-install.pth Installing easy_install script to /usr/local/bin Installing easy_install-2.6 script to /usr/local/bin Using /Library/Python/2.6/site-packages/setuptools-0.6c11-py2.6.egg Processing dependencies for setuptools Finished processing dependencies for setuptools Searching for pycurl Best match: pycurl 7.16.2.1 Processing pycurl-7.16.2.1-py2.6-macosx-10.6-universal.egg pycurl 7.16.2.1 is already the active version in easy-install.pth Using /Library/Python/2.6/site-packages/pycurl-7.16.2.1-py2.6-macosx-10.6-universal.egg Processing dependencies for pycurl Finished processing dependencies for pycurl so i thought that pycurl was correctly installed and working. But... But when i started my app, python return me an error: python /Users/lorenzodenobili/Desktop/Python/AGGIORNATORE_PY/Dropbox/wxPython/test.py Traceback (most recent call last): File "/Users/lorenzodenobili/Desktop/Python/AGGIORNATORE_PY/Dropbox/wxPython/test.py", line 20, in <module> import pycurl File "build/bdist.macosx-10.6-universal/egg/pycurl.py", line 7, in <module> File "build/bdist.macosx-10.6-universal/egg/pycurl.py", line 6, in __bootstrap__ ImportError: dlopen(/Users/lorenzodenobili/.python-eggs/pycurl-7.16.2.1-py2.6-macosx-10.6-universal.egg-tmp/pycurl.so, 2): no suitable image found. Did find: /Users/lorenzodenobili/.python-eggs/pycurl-7.16.2.1-py2.6-macosx-10.6-universal.egg-tmp/pycurl.so: mach-o, but wrong architecture Yep, there is something quite big that goes wrong. I really don't have any idea on how to solve this error, so i really need your help! thank you so much!!

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• ASP.NET MVC - using model property as form, how can I post to action?

  - by Ryan Peters

  Consider the following model: public class BandProfileModel { public BandModel Band { get; set; } public IEnumerable<Relationship> Requests { get; set; } } and the following form: <% using (Html.BeginForm()) { %> <%: Html.EditorFor(m => m.Band) %> <input type="submit" value="Save Band" /> <% } %> which posts to the following action: public ActionResult EditPost(BandProfileModel m, string band) { // stuff is done here, but m is null? return View(m); } Basically, I only have one property on my model that is used in the form. The other property in BandProfleModel is just used in the UI for other data. I'm trying to update just the Band property, but for each post, the argument "m" is always null (specifically, the .Band property is null). It's posting just fine to the action, so it isn't a problem with my route. Just the data is null. The ID and name attributes of the fields are BAND_whatever and Band.whatever (whatever being a property of Band), so it seems like it would work... What am I doing wrong? How can I use just one property as part of a form, post back, and have values populated via the model binder for my BandProfileModel property in the action? Thanks.

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• Multiple CodeSnippet in an XML .snippet file

  - by Frinavale

  I'm attempting to supplement the help features for my code by providing other developers with code snippets. These produce skeletons of code which demonstrate how to use/call my classes or methods. I've created a .snippet file and have placed it in the "%Visual Studio Folder%\Code Snippets\Visual Basic\My Snippets" folder. I've used the Code Snippets Manager and ensured that it included this folder so that I can access the snippets. Everything works well when I have 1 CodeSnippet tag within the root CodeSnippets tag.... When I add more than one CodeSnippet tag to the file (each with their own title, and their own code example) I'm experiencing something strange. The first CodeSnippet I've added contains code for adding something to my system, the second contains code for editing something in my system, and the third deleting something from the system. When I use the code snippet by right clicking and selecting "Insert Code Snippet", only the first code snippet in the file shows up as an option. When I select it, the code in the first CodeSnippet is inserted....but so is the code within the other CodeSnippet tags. Do you have to have a separate XML .snippet file for each code snippet you want to make available? After reading through MSDN about creating Code Snippets I was under the impression that this could all be done within one file. It seems that I'm not understanding something very basic here and would love to find the answer but apparently Code Snippets are under used so finding the answer has proven to be a little trickier than I first thought it would be. Thanks, -Frinny

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• Django queryset not returning the same values as the generated sql

  - by HRCerqueira

  Hello guys, I have the following queryset: subscribers = User.objects.values('email', 'username').filter( Q(subscription_settings__new_question='i') | Q(subscription_settings__new_question_watched_tags='i', marked_tags__id__in=question.tags.values('id'), tag_selections__reason='good') ).exclude(id=question.author.id) The problem is that when I evaluate the query I get only the values that are filtered by the first Q object (even if I reverse the order of the objects). So lets say that I was expecting the user A, B, C and D, where A and B are filtered by the first Q object and C and D by the second. But the queryset only returns A and B. I used the django debug toolbar to see the query that was actually being executed (and then I used a direct print statement like "print subscriber.query.as_sql()" just to be sure) and then evaluated the query directly using psql (I'm using postgres by the way), and I get the results I expect. Here's the query btw: SELECT "auth_user"."email", "auth_user"."username" FROM "auth_user" LEFT OUTER JOIN "forum_markedtag" ON ("auth_user"."id" = "forum_markedtag"."user_id") INNER JOIN "forum_defaultsubscriptionsetting" ON ("auth_user"."id" = "forum_defaultsubscriptionsetting"."user_id") WHERE ((("forum_markedtag"."reason" = E'good' AND "forum_defaultsubscriptionsetting"."new_question_watched_tags" = E'i' AND "forum_markedtag"."tag_id" IN (SELECT U0."id" FROM "tag" U0 INNER JOIN "question_tags" U1 ON (U0."id" = U1."tag_id") WHERE U1."question_id" = 64 )) OR "forum_defaultsubscriptionsetting"."new_question" = E'i' ) AND NOT ("auth_user"."id" = 10 )) Thanks in advance EDIT: I tried to break the queryset into two, one that uses the first Q object as the filter and another one with the second Q object, and although the second queryset produces the correct sql that returns the correct values when evaluated directly, it still doesn't return nothing when evaluated as a django queryset. heres the alternative code: subscribers = User.objects.values('email', 'username').filter( subscription_settings__new_question='i').exclude(id=question.author.id) subscribers2 = User.objects.values('email', 'username').filter( subscription_settings__new_question_watched_tags='i', marked_tags__id__in=question.tags.values('id'), tag_selections__reason='good').exclude(id=question.author.id)

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• Perl unpack in list context

  - by drewk

  A common 'Perlism' is generating a list as something to loop over in this form: for($str=~/./g) { print "the next character from \"$str\"=$_\n"; } In this case the global match regex returns a list that is one character in turn from the string $str, and assigns that value to $_ Instead of a regex, split can be used in the same way or 'a'..'z', map, etc. I am investigating unpack to generate a field by field interpretation of a string. I have always found unpack to be less straightforward to the way my brain works, and I have never really dug that deeply into it. As a simple case, I want to generate a list that is one character in each element from a string using unpack (yes -- I know I can do it with split(//,$str) and /./g but I really want to see if unpack can be used this way...) Obviously, I can use a field list for unpack that is unpack("A1" x length($str), $str) but is there some other way that kinda looks like globbing? ie, can I call unpack(some_format,$str) either in list context or in a loop such that unpack will return the next group of character in the format group until $str is exausted? I have read The Perl 5.12 Pack pod and the Perl 5.12 pack tutorial and the Perkmonks tutorial Here is the sample code: #!/usr/bin/perl use warnings; use strict; my $str=join('',('a'..'z', 'A'..'Z')); #the alphabet... $str=~s/(.{1,3})/$1 /g; #...in groups of three print "str=$str\n\n"; for ($str=~/./g) { print "regex: = $_\n"; } for(split(//,$str)) { print "split: \$_=$_\n"; } for(unpack("A1" x length($str), $str)) { print "unpack: \$_=$_\n"; }

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• Uploadify: Passing a form's ID as a parameter with scriptData

  - by Matt

  I need the ability to have multiple upload inputs on one page (potentially hundreds) using Uploadify. The upload PHP file will be renaming the uploaded file based on the ID of the input button used to submit it, so it will need that ID. Since I will be having hundreds of upload buttons on one page, I wanted to create a universal instantiation, so I did this using the class of the forms rather than the ID of the forms. However, when one of the inputs is clicked, I would like to pass the ID of that input as scriptData to the PHP. This is not working; PHP says 'formId' is undefined. Is there a good way get the ID attribute of the form input being used, and passing it to the upload PHP? Or is there a completely different and better method of accomplishing this? Thank you in advance!! <script type="text/javascript"> $(document).ready(function() { $('.uploady').uploadify({ 'uploader' : '/uploadify/uploadify.swf', 'script' : '/uploadify/uploadify.php', 'cancelImg' : '/uploadify/cancel.png', 'folder' : '/uploadify', 'auto' : true, // LINE IN QUESTION 'scriptData' : {'formId':$(this).attr('id')} }); }); </script> </head> The inputs look like this: <input id="file_upload1" class="uploady" name="file_upload" type="file" /> <input id="file_upload2" class="uploady" name="file_upload" type="file" /> <input id="file_upload3" class="uploady" name="file_upload" type="file" />

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• Outlook Interop Send Message from Account

  - by Reiste

  Okay, the specs have changed on this one somewhat. Maybe someone can help me with this new problem. Manually, what the user is doing is opening an new message in Outlook (2007 now) which has the "From..." field exposed. They open this up, select a certain account from the Global Address List, and send the message on behalf of that account. Is this possible to do? I can get the AddressEntry from the Global address list like so: AddressList list = null; foreach (AddressList addressList in _outlookApp.Session.AddressLists) { if (addressList.Name.ToLower().Equals("global address list")) { list = addressList; break; } } if (list != null) { AddressEntry entry = null; foreach (AddressEntry addressEntry in list.AddressEntries) { if (addressEntry.Name.ToLower().Equals("outgoing mail account")) { entry = addressEntry; break; } } } But I'm not sure I can make an Account type from the Address Entry. It seems to happen manually, when they select the address to send from. How do I mirror this in the Interop? Thanks! (My Original Question): I developed a small C# program to send email using the Outlook 2007 interop. The client required that the mail not be send using the default account - they had a secondary account they needed used. No problem - I used the Microsoft.Office.Interop.Outlook.Account class to access the availabled accounts, and choose the correct one. Now, it turns out they need this to work in Outlook 2003. Of course, the Account class doesn't exist in the Outlook interop 11.0. How can I achieve the same thing with Outlook 2003? Thanks in advance.

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• String assembly by StringBuilder vs StringWriter and PrintWriter

  - by CPerkins

  I recently encountered an idiom I haven't seen before: string assembly by StringWriter and PrintWriter. I mean, I know how to use them, but I've always used StringBuilder. Is there a concrete reason for preferring one over the other? The StringBuilder method seems much more natural to me, but is it just style? I've looked at several questions here (including this one which comes closest: http://stackoverflow.com/questions/602279/stringwriter-or-stringbuilder ), but none in which the answers actually address the question of whether there's a reason to prefer one over the other for simple string assembly. This is the idiom I've seen and used many many times: string assembly by StringBuilder: public static String newline = System.getProperty("line.separator"); public String viaStringBuilder () { StringBuilder builder = new StringBuilder(); builder.append("first thing" + newline); builder.append("second thing" + newline); // ... several things builder.append("last thing" + newline); return builder.toString(); } And this is the new idiom: string assembly by StringWriter and PrintWriter: public String viaWriters() { StringWriter stringWriter = new StringWriter(); PrintWriter printWriter = new PrintWriter(stringWriter); printWriter.println("first thing"); printWriter.println("second thing"); // ... several things printWriter.println("last thing"); printWriter.flush(); printWriter.close(); return stringWriter.toString(); }

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• Updating CoreData xcdatamodel file troubles - attribute type change

  - by San

  I noticed several questions related to this topic go unanswered. Is this such a gray area that nobody really understands it? Here is my problem: I am a midway in the development of my app and the app has never been used ouside of my iphone simulator.One of the attributes in my core data structure requires a type change.Since my app has never been used outside of my iPhone Simulator, I first deleted the sqlite file. Doubling the effort of this step, I also went into iPhone Simulator menu and selected "Reset Content and Settings...". Than, I edited the xcdatamodel file and changed the type of my attribute. I saved the file and exited. Without any other changes, I compiled. I expected it to fail because of my type change. It did not! After this, I assigned a value with new type to my attribute and it fails to compile?! Is there something else that I need to do for the change to take an effect? I would really, really appreciate an answer to my question. Thank you!

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• How to remove old indexed URLs from Google?

  - by Gok Demir

  I used Cs-cart for a site. Default installation SEO is not suitable for Turkish accented characters such as "ö" which maps to automatically "ae". Then I modified the php code and now it substitutes "ö" with "o" and "s"-"s" etc. Also I changed a category name to a better one. My problem is, google indexed both previous versions and new versions. Previous wrong urls gives 404 error. I used sitemap addon and send it to google and sitemap does not include wrong urls. However these old urls are still indexed on google. What can I do to remove them. For example http://www.google.com.tr/search?q=%C3%A7ak%C4%B1l+ta%C5%9Flar%C4%B1ndan+babil+site:eeski.com&hl=tr&client=firefox-a&hs=Z31&rls=com.ubuntu:en-US:official&filter=0 gives two top results old wrong url leads to 404: http://www.eeski.com/kitap-dergi/bilim-ve-teknik/cakl-talarndan-babil-kulesine-rakamlarn-evrensel-tarihi-ii.html right current url: http://www.eeski.com/kitap/bilim-ve-teknik/cakil-taslarindan-babil-kulesine-rakamlarin-evrensel-tarihi-ii.html What could I make google only index current urls stated on sitemap?

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• C# using namespace directive in nested namespaces

  - by MoSlo

  Right, I've usually used 'using' directives as follows using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AwesomeLib { //awesome award winning class declarations making use of Linq } i've recently seen examples of such as using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AwesomeLib { //awesome award winning class declarations making use of Linq namespace DataLibrary { using System.Data; //Data access layers and whatnot } } Granted, i understand that i can put USING inside of my namespace declaration. Such a thing makes sense to me if your namespaces are in the same root (they organized). System; namespace 1 {} namespace 2 { System.data; } But what of nested namespaces? Personally, I would leave all USING declarations at the top where you can find them easily. Instead, it looks like they're being spread all over the source file. Is there benefit to the USING directives being used this way in nested namespaces? Such as memory management or the JIT compiler?

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• How to get decent MySQL driver perfomance in Ruby

  - by Zombies

  I notice that I am getting very poor performance for either or both inserts and queries. The queries themselves are basic and can execute with no delay directly from mysql. The ruby script that I wrote is only 1 thread, so only 1 connection is being used, and never closed unless the script is terminated. Pretty basic, I am just trying to insert a lot of rows. There is a look-up or two to get a surrogate key, or to check for duplicates, but the complexity is just O(n). Also, it isn't like there are millions of records, so again the queries themselves take no time to run. I am using: Ruby 1.9.1 Gem/driver:ruby-mysql 2.9.2 MySQL 5.1.37-1ubuntu5.1 ^ all 32 bit versions on a 32bit ubuntu distro I am getting about 1-2 inserts per second, pretty slow. I know a lot of people will suggest to change drivers, but that means I have some refactoring and resting to do. So I would really appreciate any help, but please if you do recomend that at least say why you do (eg: if you have used ruby-mysql x.x.x before and found another mysql driver to be better).ruby-mysql 2.9.2 What I would like to know: How can I improve performance with ruby-mysql 2.9.2 If and only if I cannot do this with ruby-mysql 2.9.2, what should I do?

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• Why are floating point values so prolific?

  - by Kibbee

  So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster with floating point numbers, however, I can think of only a few cases that they actually the right data type would be using. If you sat back and think about every time you used a floating point value, how many times did you say, well, some error would be ok, as long as the result was a few microseconds faster. It really makes me think because Jeff was talking about NP completeness, and how heuristics give an answer that is kind of right. And well, computers shouldn't do that. They should give you the answer that is correct. Yet we see floating point values used in many applications where they are completely not valid. What really bugs me, isn't that floating point exists, but that in many languages, there isn't even a viable alternative, non-floating point, decimal value. A lot of programmers when doing financial applications have to fall back to storing the number of cents in an integer field. Which brings with it all kinds of other problems. Why do floats continue to be so prolific, even though they can't represent the real answer, and we expect computers to be accurate? [EDIT] Just to clarify, I was talking about Base 2 floating points, and not base 10 floating points. .Net offers the Decimal data type, which is a base 10 floating point value which offers a much better representation of the numbers we deal with on a daily basis in most computer programs. I find it hard to believe that even modern languages like Java don't support base 10 floating point values, unless you want to move into the realm of things like BigDecimal, which isn't really the right answer either in a lot of situations.

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• Hidden features of Perl?

  - by Adam Bellaire

  What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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• Books and resources for Java Performance tuning - when working with databases, huge lists

  - by Arvind

  Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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• Perl XML SAX parser emulating XML::Simple record for record

  - by DVK

  Short Q summary: I am looking a fast XML parser (most likely a wrapper around some standard SAX parser) which will produce per-record data structure 100% identical to those produced by XML::Simple. Details: We have a large code infrastructure which depends on processing records one-by-one and expects the record to be a data structure in a format produced by XML::Simple since it always used XML::Simple since early Jurassic era. An example simple XML is: <root> <rec><f1>v1</f1><f2>v2</f2></rec> <rec><f1>v1b</f1><f2>v2b</f2></rec> <rec><f1>v1c</f1><f2>v2c</f2></rec> </root> And example rough code is: sub process_record { my ($obj, $record_hash) = @_; # do_stuff } my $records = XML::Simple->XMLin(@args)->{root}; foreach my $record (@$records) { $obj->process_record($record) }; As everyone knows XML::Simple is, well, simple. And more importantly, it is very slow and a memory hog - due to being a DOM parser and needing to build/store 100% of data in memory. So, it's not the best tool for parsing an XML file consisting of large amount of small records record-by-record. However, re-writing the entire code (which consist of large amount of "process_record"-like methods) to work with standard SAX parser seems like an big task not worth the resources, even at the cost of living with XML::Simple. What I'm looking for is an existing module which will probably be based on a SAX parser (or anything fast with small memory footprint) which can be used to produce $record hashrefs one by one based on the XML pictured above that can be passed to $obj->process_record($record) and be 100% identical to what XML::Simple's hashrefs would have been. I don't care much what the interface of the new module is - e.g whether I need to call next_record() or give it a callback coderef accepting a record.

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• Looking for a lock-free RT-safe single-reader single-writer structure

  - by moala

  Hi, I'm looking for a lock-free design conforming to these requisites: a single writer writes into a structure and a single reader reads from this structure (this structure exists already and is safe for simultaneous read/write) but at some time, the structure needs to be changed by the writer, which then initialises, switches and writes into a new structure (of the same type but with new content) and at the next time the reader reads, it switches to this new structure (if the writer multiply switches to a new lock-free structure, the reader discards these structures, ignoring their data). The structures must be reused, i.e. no heap memory allocation/free is allowed during write/read/switch operation, for RT purposes. I have currently implemented a ringbuffer containing multiple instances of these structures; but this implementation suffers from the fact that when the writer has used all the structures present in the ringbuffer, there is no more place to change from structure... But the rest of the ringbuffer contains some data which don't have to be read by the reader but can't be re-used by the writer. As a consequence, the ringbuffer does not fit this purpose. Any idea (name or pseudo-implementation) of a lock-free design? Thanks for having considered this problem.

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• Why is setting HTML5's CanvasPixelArray values ridiculously slow and how can I do it faster?

  - by Nixuz

  I am trying to do some dynamic visual effects using the HTML 5 canvas' pixel manipulation, but I am running into a problem where setting pixels in the CanvasPixelArray is ridiculously slow. For example if I have code like: imageData = ctx.getImageData(0, 0, 500, 500); for (var i = 0; i < imageData.length; i += 4){ imageData.data[i] = buffer[i]; imageData.data[i + 1] = buffer[i + 1]; imageData.data[i + 2] = buffer[i + 2]; } ctx.putImageData(imageData, 0, 0); Profiling with Chrome reveals, it runs 44% slower than the following code where CanvasPixelArray is not used. tempArray = new Array(500 * 500 * 4); imageData = ctx.getImageData(0, 0, 500, 500); for (var i = 0; i < imageData.length; i += 4){ tempArray[i] = buffer[i]; tempArray[i + 1] = buffer[i + 1]; tempArray[i + 2] = buffer[i + 2]; } ctx.putImageData(imageData, 0, 0); My guess is that the reason for this slowdown is due to the conversion between the Javascript doubles and the internal unsigned 8bit integers, used by the CanvasPixelArray. Is this guess correct? Is there anyway to reduce the time spent setting values in the CanvasPixelArray?

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