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• dynamically horizontal scalable key value store

  - by Zubair

  Hi, Is there a key value store that will give me the following: Allow me to simply add and remove nodes and will redstribute the data automatically Allow me to remove nodes and still have 2 extra data nodes to provide redundancy Allow me to store text or images up to 1GB in size Can store small size data up to 100TB of data Fast (so will allow queries to be performed on top of it) Make all this transparent to the client Works on Ubuntu/FreeBSD or Mac Free or open source I basically want something I can use a "single", and not have to worry about having memcached, a db, and several storage components so yes, I do want a database "silver bullet" you could say. Thanks Zubair Answers so far: MogileFS on top of BackBlaze - As far as I can see this is just a filesystem, and after some research it only seems to be appropriate for large image files Tokyo Tyrant - Needs lightcloud. This doesn't auto scale as you add new nodes. I did look into this and it seems it is very fast for queries which fit onto a single node though Riak - This is one I am looking into myself, but I don't have any results yet Amazon S3 - Is anyone using this as their sole persistance layer in production? From what I have seen it seems to be used for storage of images as complex queries are too expensive @shaman suggested Cassandra - definitely one I am looking into So far it seems that there is no database or key value store that fulfills the criteria I mentioned, not even after offering a bounty of 100 points did the question get answered!

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• How to use SQLAlchemy to dump an SQL file from query expressions to bulk-insert into a DBMS?

  - by Mahmoud Abdelkader

  Please bear with me as I explain the problem, how I tried to solve it, and my question on how to improve it is at the end. I have a 100,000 line csv file from an offline batch job and I needed to insert it into the database as its proper models. Ordinarily, if this is a fairly straight-forward load, this can be trivially loaded by just munging the CSV file to fit a schema, but I had to do some external processing that requires querying and it's just much more convenient to use SQLAlchemy to generate the data I want. The data I want here is 3 models that represent 3 pre-exiting tables in the database and each subsequent model depends on the previous model. For example: Model C --> Foreign Key --> Model B --> Foreign Key --> Model A So, the models must be inserted in the order A, B, and C. I came up with a producer/consumer approach: - instantiate a multiprocessing.Process which contains a threadpool of 50 persister threads that have a threadlocal connection to a database - read a line from the file using the csv DictReader - enqueue the dictionary to the process, where each thread creates the appropriate models by querying the right values and each thread persists the models in the appropriate order This was faster than a non-threaded read/persist but it is way slower than bulk-loading a file into the database. The job finished persisting after about 45 minutes. For fun, I decided to write it in SQL statements, it took 5 minutes. Writing the SQL statements took me a couple of hours, though. So my question is, could I have used a faster method to insert rows using SQLAlchemy? As I understand it, SQLAlchemy is not designed for bulk insert operations, so this is less than ideal. This follows to my question, is there a way to generate the SQL statements using SQLAlchemy, throw them in a file, and then just use a bulk-load into the database? I know about str(model_object) but it does not show the interpolated values. I would appreciate any guidance for how to do this faster. Thanks!

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• Are there any radix/patricia/critbit trees for Python?

  - by Andrew Dalke

  I have about 10,000 words used as a set of inverted indices to about 500,000 documents. Both are normalized so the index is a mapping of integers (word id) to a set of integers (ids of documents which contain the word). My prototype uses Python's set as the obvious data type. When I do a search for a document I find the list of N search words and their corresponding N sets. I want to return the set of documents in the intersection of those N sets. Python's "intersect" method is implemented as a pairwise reduction. I think I can do better with a parallel search of sorted sets, so long as the library offers a fast way to get the next entry after i. I've been looking for something like that for some time. Years ago I wrote PyJudy but I no longer maintain it and I know how much work it would take to get it to a stage where I'm comfortable with it again. I would rather use someone else's well-tested code, and I would like one which supports fast serialization/deserialization. I can't find any, or at least not any with Python bindings. There is avltree which does what I want, but since even the pair-wise set merge take longer than I want, I suspect I want to have all my operations done in C/C++. Do you know of any radix/patricia/critbit tree libraries written as C/C++ extensions for Python? Failing that, what is the most appropriate library which I should wrap? The Judy Array site hasn't been updated in 6 years, with 1.0.5 released in May 2007. (Although it does build cleanly so perhaps It Just Works.)

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• UIView coordinate transforms on rotation during keyboard appearance

  - by SG

  iPad app; I'm trying to resize my view when the keyboard appears. It amounts to calling this code at appropriate times: CGRect adjustedFrame = self.frame; adjustedFrame.size.height -= keyboardFrame.size.height; [self setFrame:adjustedFrame]; Using this technique for a view contained in a uisplitview-based app works in all 4 orientations, but I've since discovered that a vanilla uiview-based app does not work. What happens is that apparently the uisplitview is smart enough to convert the coordinates of its subviews (their frame) such that the origin is in the "viewer's top left" regardless of the orientation. However, a uiview is not able to correctly report these coordinates. Though the origin is reported as (0,0) in all orientations, the view's effective origin is always as if the ipad were upright. What is weird about this is that the view correctly rotates and draws, but it always originates in the literal device top left. How can I get the view to correctly make its origin the "top left" to the viewer, not the device's fixed top left? What am I missing? Please, for something so trivial I've spent about 6 hours on this already with every brute force technique and research angle I could think of. This is the original source which doesn't work in this case: http://stackoverflow.com/questions/1951826/move-up-uitoolbar

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• To have an Integer pointing to 3 ordered lists in Java

  - by Masi

  Which datastructure would you use in the place of X to have efficient merges, sorts and additions as described below? #1 Possible solution: one HashMap to X -datastructure Having a HashMap pointing from fileID to some datastructure linking word, wordCount and wordID may be a good solution. However, I have not found a way to implement it. I am not allowed to use Postgres or any similar tool to keep my data neutralized. I want to have efficient merges, sorts and additions according to fileID, wordID or wordCount for the type below. I have the type Words which has th field fileID that points to a list of words and to relating pieces of information: The Type class Words =================================== fileID: int [list of words] : ArrayList [list of wordCounts] : ArrayList [list of wordIDs] : ArrayList Example of the data in fileID word wordCount wordID instance1 of words 1 He 123 1111 1 llo 321 2 instance2 of words 2 Van 213 666 2 cou 777 932 Example of needed merge fileID wordID fileID wordID 1 2 1 3 wordID=2 2 2 ========> 1 2 2 3 2 2 I cannot see any usage of set-operations such as intersections here because order is needed. Having about three HashMaps makes sorting difficult: from word to wordID in a given fileID from wordID to fileID from wordID to wordCount in a given fileID

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• Specify which xml file to load when link is clicked

  - by Jason

  Good morning, I would like it so when a link is clicked on the homepage it would load a particular xml file into the next page (the page is called category-list.apsx). This category list page uses the Repeater Control method to display the xml details on the page. I used the example shown here: http://www.w3schools.com/aspnet/aspnet_repeater.asp So at the moment the repeater script looks like: <script runat="server"> sub Page_Load if Not Page.IsPostBack then dim mycategories=New DataSet mycategories.ReadXml(MapPath("categories.xml")) categories.DataSource=mycategories categories.DataBind() end if end sub </script> After doing some research I did find someone with the same problem and the solution was to insert #tags as part of the link on the homepage (i.e. category-list.apsx#company1results) and then some script on the list page to pick up the correct xml file: <script type="text/javascript"> var old_onload = window.onload; // Play it safe by respecting onload handlers set by other scripts. window.onload=function() { var categories = document.location.href.substring(document.location.href.indexOf("#")+1); loadXMLDoc('XML/'+categories+'.xml'); old_onload(); } </script> This was from the following link: http://www.hotscripts.com/forums/javascript/45641-solved-specify-xml-file-load-when-click-link.html How can I get these two scripts to connect with each other? Thank you for your time

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• Error while compiling Hello world program for CUDA

  - by footy

  I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA: #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ __global__ void kernel(void) { } /* MAIN PROGRAM BEGINS */ int main(void) { /* Dg = 1; Db = 1; Ns = 0; S = 0 */ kernel<<<1,1>>>(); /* PRINT 'HELLO, WORLD!' TO THE SCREEN */ printf("\n Hello, World!\n\n"); /* INDICATE THE TERMINATION OF THE PROGRAM */ return 0; } /* MAIN PROGRAM ENDS */ The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main': /home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil': /usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1': /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary' /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)': /usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch' collect2: ld returned 1 exit status I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)

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• System.Dynamic bug?

  - by ControlFlow

  While I playing with the C# 4.0 dynamic, I found strange things happening with the code like this: using System.Dynamic; sealed class Foo : DynamicObject { public override bool TryInvoke( InvokeBinder binder, object[] args, out object result) { result = new object(); return true; } static void Main() { dynamic foo = new Foo(); var t1 = foo(0); var t2 = foo(0); var t3 = foo(0); var t4 = foo(0); var t5 = foo(0); } } Ok, it works but... take a look at IntelliTrace window: So every invokation (and other operations too on dynamic object) causes throwing and catching strange exceptions twice! I understand, that sometimes exceptions mechanism may be used for optimizations, for example first call to dynamic may be performed to some stub delegate, that simply throws exception - this may be like a signal to dynamic binder to resolve an correct member and re-point delegate. Next call to the same delegate will be performed without any checks. But... behavior of the code above looks very strange. Maybe throwing and catching exceptions twice per any operation on DynamicObject - is a bug?

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• kick off a map reduce job from my java/mysql webapp

  - by Brian

  Hi guys, I need a bit of archecture advice. I have a java based webapp, with a JPA based ORM backed onto a mysql relational database. Now, as part of the application I have a batch job that compares thousands of database records with each other. This job has become too time consuming and needs to be parallelized. I'm looking at using mapreduce and hadoop in order to do this. However, I'm not too sure about how to integrate this into my current architecture. I think the easiest initial solution is to find a way to push data from mysql into hadoop jobs. I have done some initial research on this and found the following relevant information and possibilities: 1) https://issues.apache.org/jira/browse/HADOOP-2536 this gives an interesting overview of some inbuilt JDBC support 2) This article http://architects.dzone.com/articles/tools-moving-sql-database describes some third party tools to move data from mysql to hadoop. To be honest I'm just starting out with learning about hbase and hadoop but I really don't know how to integrate this into my webapp. Any advice is greatly appreciated. cheers, Brian

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• FlashBuilder 4 and Zend Framework error

  - by sig

  I am trying to use adobe flash builder 4 with a php service. I had it set up an older macbook running leopard, but just tried to set it up on my new laptop running snow leopard. I did all the same steps.. set the Flex Server to be PHP, set the web root and url. Then I go to Data-Connect To PHP and point it to a php file I have in my web root. It says it needs to install Zend, and claims it does so successfully, but then when I try to continue, I get an error. I don't understand.. this same setup works on my older laptop. (Yes, I checked the amf.production was false) Unable to retrieve operations and entities from the file Make sure that Zend Framework is installed correctly and the parameter "amf.production" is not set to true in the amf_config.ini file located in the project output folder. false), true);$default_config-merge(new Zend_Config_Ini($configfile, 'zendamf'));$default_config-setReadOnly();$amf = $default_config-amf;// Store configuration in the registryZend_Registry::set("amf-config", $amf);// Initialize AMF Server$server = new Zend_Amf_Server();$server-setProduction($amf-production);if(isset($amf-directories)) { $dirs = $amf-directories-toArray(); foreach($dirs as $dir) { // get the first character of the path. // If it does not start with slash then it implies that the path is relative to webroot. Else it will be treated as absolute path $length = strlen($dir); $firstChar = $dir; if($length = 1) $firstChar = $dir[0]; if($firstChar != "/"){ // if the directory is ./ path then we add the webroot only. if($dir == "./"){ $server-addDirectory($webroot); }else{ $tempPath = $webroot . "/" . $dir; $server-addDirectory($tempPath); } }else{ $server-addDirectory($dir); } }}// Initialize introspector for non-productionif(!$amf-production) { $server-setClass('Zend_Amf_Adobe_Introspector', '', array("config" = $default_config, "server" = $server)); $server-setClass('Zend_Amf_Adobe_DbInspector', '', array("config" = $default_config, "server" = $server));}// Handle requestecho $server-handle();

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• Rest WebService error handling.

  - by Pratik

  Hi there, I am using RestWebservice for few basic operations , like creating/searching. The request xml looks something like this <customer> <name/> ..... </customer> For a successful operation I return the same customer XML with extra fields populated in it(eg. systemId etc which we blank in the request) . with Response.Status=2000 For an unsuccessful operation i return something like this with different error codes . e.g Response.Status = 422(Unprocessable entity) Response.Status= 500(Internal Server Error) and few others.. <errors> <error> An exception occurred while creating the customer</error> <error> blah argument is not valid.</error> </errors> Now i am not sure , whether this is the correct way of sending the errors to the client. Maybe it should be present in the header of the response. I will really appreciate any help. Thanks!

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• ASP.NET 2.0 RijndaelManaged encryption algorithm vs. FIPS

  - by R Rush

  I'm running into an issue with an ASP.NET 2.0 application. Our network folks just upped our security, and now I get the floowing error whenever I try to access the app: "This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms." I've done a little research, and it sounds like ASP.NET uses the RijndaelManaged AES encryption algorithm to encrypt the ViewState of pages... and RijndaelManaged is on the list of algorithms that aren't FIPS compliant. We're certainly not explicitly calling any encryption algorithm... much less anything on the non-compliant list. This ViewState business makes sense to me, I guess. The thing I can't muddle out, though, is what to do about it. I've found a KB article that suggests using a web.config setting to specify a different algorithm... but either that didn't stick, or that algorithm isn't up to snuff, either. So: 1) Is the RijndaelManaged / ViewState thing actually the problem? Or am I barking up the wrong tree? 2) How to I specify what algorithm to use instead of RijndaelManaged? I've got a list of algorithms that are and aren't compliant; I'm just not sure where to plug that information in. Thanks! Richard

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• Instantiate type variable in Haskell

  - by danportin

  EDIT: Solved. I was unware that enabling a language extension in the source file did not enable the language extension in GHCi. The solution was to :set FlexibleContexts in GHCi. I recently discovered that type declarations in classes and instances in Haskell are Horn clauses. So I encoded the arithmetic operations from The Art of Prolog, Chapter 3, into Haskell. For instance: fac(0,s(0)). fac(s(N),F) :- fac(N,X), mult(s(N),X,F). class Fac x y | x -> y instance Fac Z (S Z) instance (Fac n x, Mult (S n) x f) => Fac (S n) f pow(s(X),0,0) :- nat(X). pow(0,s(X),s(0)) :- nat(X). pow(s(N),X,Y) :- pow(N,X,Z), mult(Z,X,Y). class Pow x y z | x y -> z instance (N n) => Pow (S n) Z Z instance (N n) => Pow Z (S n) (S Z) instance (Pow n x z, Mult z x y) => Pow (S n) x y In Prolog, values are insantiated for (logic) variable in a proof. However, I don't understand how to instantiate type variables in Haskell. That is, I don't understand what the Haskell equivalent of a Prolog query ?-f(X1,X2,...,Xn) is. I assume that :t undefined :: (f x1 x2 ... xn) => xi would cause Haskell to instantiate xi, but this gives a Non type-variable argument in the constraint error, even with FlexibleContexts enabled.

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• using Autofac in a multi-layered architecture

  - by Kamyar

  I'm fairly new to the DI/IoC concept and would like to use Autofac in a 3-layered ASP.NET Webforms application. UI layer: An ASP.NET webforms website. BLL: Business logic layer which calls the repositories on DAL. DAL: .EDMX file (Entity Model) and ObjectContext with Repository classes which abstract the CRUD operations for each entity. Entities: The POCO Entities. Persistence Ignorant. Generated by Microsoft's ADO.Net POCO Entity Generator. I have asked a more general question here. Basically, I'd like to create an obejctcontext per HttpContext in my DAL. But i don't want to add a reference to DAL in UI or access to HttpContext in DAL directly. I guess this is where IoC tools come to play. The answer to my previous question is a very good example of using Windsor Castle. I'd like to use Autofac as my IoC tool and Don't know how to achieve this. (How to access DAL in application_start to register the component while I don't want to reference it in my UI, what are the proper references to be able to use DAL component in BLL with Autofac, Should I register BLL as a component with Autofac too) Sorry folks for not providing an explicit question and requesting a kind of working example, But I'm very unfamiliar to the whole IoC concept and I don't think I can achieve it to use in my current time-limited project.

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• Sweave/R - Automatically generating an appendix that contains all the model summaries/plots/data pro

  - by John Horton

  I like the idea of making research available at multiple levels of detail i.e., abstract for the casually curious, full text for the more interested, and finally the data and code for those working in the same area/trying to reproduce your results. In between the actual text and the data/code level, I'd like to insert another layer. Namely, I'd like to create a kind of automatically generated appendix that contains the full regression output, diagnostic plots, exploratory graphs data profiles etc. from the analysis, regardless of whether those plots/regressions etc. made it into the final paper. One idea I had was to write a script that would examine the .Rnw file and automatically: Profile all data sets that are loaded (sort of like the Hmisc(?) package) Summarize all regressions - i.e., run summary(model) for all models Present all plots (regardless of whether they made it in the final version) The idea is to make this kind of a low-effort, push-button sort of thing as opposed to a formal appendix written like the rest of a paper. What I'm looking for is some ideas on how to do this in R in a relatively simple way. My hunch is that there is some way of going through the namespace, figuring out what something is and then dumping into a PDF. Thoughts? Does something like this already exist?

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• Bash and regex problem : check for tokens entered into a Coke vending machine

  - by Michael Mao

  Hi all: Here is a "challenge question" I've got from Linux system programming lecture. Any of the following strings will give you a Coke if you kick: L = { aaaa, aab, aba, baa, bb, aaaa"a", aaaa"b", aab"a", … ab"b"a, ba"b"a, ab"bbbbbb"a, ... } The letters shown in wrapped double quotes indicate coins that would have fallen through (but those strings are still part of the language in this example). Exercise (a bit hard) show this is the language of a regular expression And this is what I've got so far : #!/usr/bin/bash echo "A bottle of Coke costs you 40 cents" echo -e "Please enter tokens (a = 10 cents, b = 20 cents) in a sequence like 'abba' :\c" read tokens #if [ $tokens = aaaa ]||[ $tokens = aab ]||[ $tokens = bb ] #then # echo "Good! now a coke is yours!" #else echo "Thanks for your money, byebye!" if [[ $token =~ 'aaaa|aab|bb' ]] then echo "Good! now a coke is yours!" else echo "Thanks for your money, byebye!" fi Sadly it doesn't work... always outputs "Thanks for your money, byebye!" I believe something is wrong with syntax... We didn't provided with any good reference book and the only instruction from the professor was to consult "anything you find useful online" and "research the problem yourself" :( I know how could I do it in any programming language such as Java, but get it done with bash script + regex seems not "a bit hard" but in fact "too hard" for anyone with little knowledge on something advanced as "lookahead"(is this the terminology ?) I don't know if there is a way to express the following concept in the language of regex: Valid entry would consist of exactly one of the three components : aaaa, aab and bb, regardless of order, followed by an arbitrary sequence of a or b's So this is what is should be like : (a{4}Ua{2}bUb{2})(aUb)* where the content in first braces is order irrelevant. Thanks a lot in advance for any hints and/or tips :)

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• Getting parameters values blank and null when using custom wsdl in axis2

  - by Narendra

  Hi All, I am using axis2 for my web services creation. I want to user my own wsdl file instead of using generated wsdl file. When I am placing my own wsdl file in META-INF directory and deploying my web services they are deploying successfully. But the problem is when i try to test these web service using soapui it throwing null pointer exception. For example I am invoking following operations in soap ui. public String testWebService(String a, String b) { LogHelper.info("Value of a is:"+a); LogHelper.info("Value of b is :"+b); String c=a.trim()+b.Trim(); return "suceess" } output in console: value of a is: value of b is:null 19:58:47,781 ERROR [RPCMessageReceiver] Exception occurred while trying to invoke service method testWebService java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.axis2.rpc.receivers.RPCUtil.invokeServiceClass(RPCUtil.java:194) at org.apache.axis2.rpc.receivers.RPCMessageReceiver.invokeBusinessLogic(RPCMessageReceiver.java:102) at org.apache.axis2.receivers.AbstractInOutMessageReceiver.invokeBusinessLogic(AbstractInOutMessageReceiver.java:40) at org.apache.axis2.receivers.AbstractMessageReceiver.receive(AbstractMessageReceiver.java:114) at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:173) at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:173) at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:142) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:190) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92) at o...................................................... SO What i understand is i am getting value for a is black and value of b is null. Can any one give me any suggestions please. Thanks, Narendra

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• How do I implement repository pattern and unit of work when dealing with multiple data stores?

  - by Jason

  I have a unique situation where I am building a DDD based system that needs to access both Active Directory and a SQL database as persistence. Initially this wasnt a problem because our design was setup where we had a unit of work that looked like this: public interface IUnitOfWork { void BeginTransaction() void Commit() } and our repositories looked like this: public interface IRepository<T> { T GetByID() void Save(T entity) void Delete(T entity) } In this setup our load and save would handle the mapping between both data stores because we wrote it ourselves. The unit of work would handle transactions and would contain the Linq To SQL data context that the repositories would use for persistence. The active directory part was handled by a domain service implemented in infrastructure and consumed by the repositories in each Save() method. Save() was responsible with interacting with the data context to do all the database operations. Now we are trying to adapt it to entity framework and take advantage of POCO. Ideally we would not need the Save() method because the domain objects are being tracked by the object context and we would just need to add a Save() method on the unit of work to have the object context save the changes, and a way to register new objects with the context. The new proposed design looks more like this: public interface IUnitOfWork { void BeginTransaction() void Save() void Commit() } public interface IRepository<T> { T GetByID() void Add(T entity) void Delete(T entity) } This solves the data access problem with entity framework, but does not solve the problem with our active directory integration. Before, it was in the Save() method on the repository, but now it has no home. The unit of work knows nothing other than the entity framework data context. Where should this logic go? I argue this design only works if you only have one data store using entity framework. Any ideas how to best approach this issue? Where should I put this logic?

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• Non-Mainstream Languages, Bad for your resume?

  - by Joe

  Hi folks, I got my BS in Computer Science about seven years ago. I spent two years in neuroscience research and the next three providing what amounts to tech support. But I love computer programming - and I have since written, as a freelancer, non-trivial commercial code in Haskell, Smalltalk, and Objective-C. I used these languages because I find them rewarding, they make me a better programmer and thus, I thought, more attractive to companies. However the polar opposite has occured and I am now unhireable. The freelance market has bottomed out and I am looking for regular employment. But I am being repeatedly turned down, even for entry-level positions, because I don't specifically fit the requirements - eg. Java programmer with 2+ years with JUnit, JavaMail, Servlets etc. And none of the hiring managers, let alone the recruiters, have heard of either Haskell or Smalltalk and more disturbing is their thinly veiled contempt for my background. My question is , how should I market myself to these positions? Is anyone here in a similar position? What should I be doing different professionally? More broadly is this contempt for non-mainstream experience occurring everywhere or just my town? And if there are any hiring managers reading this, I'd love to hear your side. Please be brutally honest. thanks, joe

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• Building an extension framework for a Rails app

  - by obvio171

  I'm starting research on what I'd need in order to build a user-level plugin system (like Wordpress plugins) for a Rails app, so I'd appreciate some general pointers/advice. By user-level plugin I mean a package a user can extract into a folder and have it show up on an admin interface, allowing them to add some extra configuration and then activate it. What is the best way to go about doing this? Is there any other opensource project that does this already? What does Rails itself already offer for programmer-level plugins that could be leveraged? Any Rails plugins that could help me with this? A plugin would have to be able to: run its own migrations (with this? it's undocumented) have access to my models (plugins already do) have entry points for adding content to views (can be done with content_for and yield) replace entire views or partials (how?) provide its own admin and user-facing views (how?) create its own routes (or maybe just announce its presence and let me create the routes for it, to avoid plugins stepping on each other's toes) Anything else I'm missing? Also, is there a way to limit which tables/actions the plugin has access to concerning migrations and models, and also limit their access to routes (maybe letting them include, but not remove routes)? P.S.: I'll try to keep this updated, compiling stuff I figure out and relevant answers so as to have a sort of guide for others.

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• Looking for Recommendations on Version Control System with Intuitive (.NET) API?

  - by John L.

  I'm working on a project which generates (composite) Microsoft Word documents which are comprised of one or more child documents. There are tens of thousands of permutations of the composite documents. Far too many for users to easily manage. Users will need to view/edit the child documents through the app which hides all of the nasty implementation details. A requirement of the system is that the child documents must be version controlled. That is what has been tripping me up. I've been torn between using an off-the-shelf solution or rolling my own. At a minimum, the system needs to support get latest, get specific version, add new, rename and possibly delete. I’ve whiteboarded it enough to realize it won’t be a trivial task to create my own. As far as commercial systems I have VSS and TFS at my disposal. I've played with the TFS API some, but it isn’t as intuitive or well documented as I had hoped. I'm not averse to an open source solution (e.g. SVN), but I have less familiarity with them. Which approach or tool would you recommend? Why? Do you have any links to API documentation you would recommend? Environment: C#, VS2008, SQL Server 2005/2008, low volume (a few hundred operations per day)

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• Better ways to implement a modulo operation (algorithm question)

  - by ryxxui

  I've been trying to implement a modular exponentiator recently. I'm writing the code in VHDL, but I'm looking for advice of a more algorithmic nature. The main component of the modular exponentiator is a modular multiplier which I also have to implement myself. I haven't had any problems with the multiplication algorithm- it's just adding and shifting and I've done a good job of figuring out what all of my variables mean so that I can multiply in a pretty reasonable amount of time. The problem that I'm having is with implementing the modulus operation in the multiplier. I know that performing repeated subtractions will work, but it will also be slow. I found out that I could shift the modulus to effectively subtract large multiples of the modulus but I think there might still be better ways to do this. The algorithm that I'm using works something like this (weird pseudocode follows): result,modulus : integer (n bits) (previously defined) shiftcount : integer (initialized to zero) while( (modulus<result) and (modulus(n-1) != 1) ){ modulus = modulus << 1 shiftcount++ } for(i=shiftcount;i>=0;i++){ if(modulus<result){result = result-modulus} if(i!=0){modulus = modulus << 1} } So...is this a good algorithm, or at least a good place to start? Wikipedia doesn't really discuss algorithms for implementing the modulo operation, and whenever I try to search elsewhere I find really interesting but incredibly complicated (and often unrelated) research papers and publications. If there's an obvious way to implement this that I'm not seeing, I'd really appreciate some feedback.

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• How to best show progress info when using ADO.NET?

  - by Yadyn

  I want to show the user detailed progress information when performing potentially lengthy database operations. Specifically, when inserting/updating data that may be on the order of hundreds of KB or MB. Currently, I'm using in-memory DataTables and DataRows which are then synced with the database via TableAdapter.Update calls. This works fine and dandy, but the single call leaves little opportunity to glean any kind of progress info to show to the user. I have no idea how much data is passing through the network to the remote DB or its progress. Basically, all I know is when Update returns and it is assumed complete (barring any errors or exceptions). But this means all I can show is 0% and then a pause and then 100%. I can count the number of rows, even going so far to cound how many are actually Modified or Added, and I could even maybe calculate per DataRow its estimated size based on the datatype of each column, using sizeof for value types like int and checking length for things like strings or byte arrays. With that, I could probably determine, before updating, an estimated total transfer size, but I'm still stuck without any progress info once Update is called on the TableAdapter. Am I stuck just using an indeterminate progress bar or mouse waiting cursor? Would I need to radically change our data access layer to be able to hook into this kind of information? Even if I can't get it down to the precise KB transferred (like a web browser file download progress bar), could I at least know when each DataRow/DataTable finishes or something? How do you best show this kind of progress info using ADO.NET?

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• What's the largest (most complex) PHP algorithm ever implemented in a single monolithic PHP script?

  - by Alex R

  I'm working on a tool which converts PHP code to Scala. As one of the finishing touches, I'm in need of a really good (er, somewhat biased) benchmark. By dumb luck my first benchmark attempt was with some code which uses bcmath extensively, which unfortunately is 1000x slower in Java, making the Scala code 22x slower overall than the original PHP. So I'm looking for some meaningful PHP benchmark with the following characteristics: The source needs to be in a single file. I need it to be simple to setup - no databases, hard-to-find input files, etc. Simple text input and output preferred. It should not use features that are slow in Java (BigInteger, trigonometric functions, etc). It should not use exoteric or dynamic PHP functions (e.g. no "eval" or "variable vars"). It should not over-rely on built-in libraries, e.g. MD5, crypt, etc. It should not be I/O bound. A CPU-bound memory-hungry algorithm is preferred. Basically, intensive OO operations, integer and string manipulation, recursion, etc would be great. Thanks

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• Defining Light Coordinates

  - by Zachary

  I took a Computer Graphics exam a couple of days ago which had extra credit question like the following: A light can be defined in one of two ways. It can be defined in world coordinates, e.g. a street light, or in the viewer (eye coordinates), e.g., a head-lamp worn by a miner. In either case the viewpoint can freely change. Describe how the light should be transformed different in these two cases. Since I won't get to see the results of this until after spring break, I thought I would ask here. It seems like the analogies being used are misleading - could you not define a light source that is located at the viewers eye in world coordinates just as well as you could in eye coordinates? I've been doing some research on how OpenGL handles light, and it seems as though it always uses eye coordinates - the ModelView matrix would be applied to any light in world coordinates. In that case the answer may just be that you would have to transform light defined in world coordinates into eye coordinates using something like the ModelView matrix, while light defined in eye coordinates would only need to be transformed by the projection matrix. Then again I could be totally under thinking (or over thinking this). Another thought I had is that it determines which way you render shadows, but that has more to do with the location of the light and its type (point, directional, emission, etc) than what coordinates it is represented in. Any ideas?

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