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• Apache tomcat7 + couchdb in the same host

  - by demotics2002

  I couldn't find any guide on the internet about how to make them work together. I found some couchdb tutorials but they are mostly having the web pages hosted in couchdb's own webserver. My requirement: 1. Use tomcat 7 (or other versions) - i will be using jsp for the website. It has some features that require file upload and processing of files, file generation, and etc., that will require java. It also has admin console that will require the next item, 2. ExtJS (maybe V4) - I will be needing this in the admin console page for restful access to couchdb and other ui components (sorry but I am not considering jquery at the moment because I am already familiar with . 3. Couchdb - because the client needs a dynamic structure of data. Now my question is how to make tomcat and couchdb run on the same host (and port of course)? As much as possible I would like to avoid making my pages doing cross domain js calls. Worst case I may have to create a servlet that overrides put|get|post|delete that calls couchdb (either by using a driver or httpclient).

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• How do I grant a site's applet an AllPermission privilege?

  - by nahsra

  I'd like to specify certain applets to run with java.security.AllPermission on my computer (for debugging and security testing). However, I don't want to enable all applets that I run to have this permission. So, editing my user Java policy file (which I have ensured is the correct policy file through testing), I try to put this value: grant codeBase "http://host_where_applet_lives/-" { permission java.security.AllPermission; }; This value fails when the applet tries to do something powerful (create a new Thread, in my case). However, when I put the following value: grant { permission java.security.AllPermission; }; The applet is able to perform the powerful operation. The only difference is the lack of a codeBase attribute. An answer to a similar question asked here [1] seemed to suggest (but never show or prove) that AccessController.doPrivileged() calls may be required. To me, this sounds wrong as I don't need that call when I grant the permissions to all applets (the second example I showed). Even if this is a solution, littering the applets I run with AccessController.doPrivileged() calls is not easy or necessarily possible. To top it off, my tests show that this just doesn't work anyway. But I'm happy to hear more ideas around it. [1] http://stackoverflow.com/questions/1751412/cant-get-allpermission-configured-for-intranet-applet-can-anyone-help

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• Preparing a MySQL INSERT/UPDATE statement with DEFAULT values

  - by Raveren

  Quoting MySQL INSERT manual - same goes for UPDATE: Use the keyword DEFAULT to set a column explicitly to its default value. This makes it easier to write INSERT statements that assign values to all but a few columns, because it enables you to avoid writing an incomplete VALUES list that does not include a value for each column in the table. Otherwise, you would have to write out the list of column names corresponding to each value in the VALUES list. So in short if I write INSERT INTO table1 (column1,column2) values ('value1',DEFAULT); A new row with column2 set as its default value - whatever it may be - is inserted. However if I prepare and execute a statement in PHP: $statement = $pdoObject-> prepare("INSERT INTO table1 (column1,column2) values (?,?)"); $statement->execute(array('value1','DEFAULT')); The new row will contain 'DEFAULT' as its text value - if the column is able to store text values. Now I have written an abstraction layer to PDO (I needed it) and to get around this issue am considering to introduce a const DEFAULT_VALUE = "randomstring"; So I could execute statements like this: $statement->execute(array('value1',mysql::DEFAULT_VALUE)); And then in method that does the binding I'd go through values that are sent to be bound and if some are equal to self::DEFAULT_VALUE, act accordingly. I'm pretty sure there's a better way to do this. Has someone else encountered similar situations?

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• Bison input analyzer - basic question on optional grammer and input interpretation

  - by kumar_m_kiran

  Hi All, I am very new to Flex/Bison, So it is very navie question. Pardon me if so. May look like homework question - but I need to implement project based on below concept. My question is related to two parts, Question 1 In Bison parser, How do I provide rules for optional input. Like, I need to parse the statment Example : -country='USA' -state='INDIANA' -population='100' -ratio='0.5' -comment='Census study for Indiana' Here the ratio token can be optional. Similarly, If I have many tokens optional, then How do I provide the grammer in the parser for the same? My code looks like, %start program program : TK_COUNTRY TK_IDENTIFIER TK_STATE TK_IDENTIFIER TK_POPULATION TK_IDENTIFIER ... where all the tokens are defined in the lexer. Since there are many tokens which are optional, If I use "|" then there will be many different ways of input combination possible. Question 2 There are good chance that the comment might have quotes as part of the input, so I have added a token -tag which user can provide to interpret the same, Example : -country='USA' -state='INDIANA' -population='100' -ratio='0.5' -comment='Census study for Indiana$'s population' -tag=$ Now, I need to reinterpret Indiana$'s as Indiana's since -tag=$. Please provide any input or related material for to understand these topic. Thanks for your input in advance.

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• R + Bioconductor : combining probesets in an ExpressionSet

  - by Mike Dewar

  Hi, First off, this may be the wrong Forum for this question, as it's pretty darn R+Bioconductor specific. Here's what I have: library('GEOquery') GDS = getGEO('GDS785') cd4T = GDS2eSet(GDS) cd4T <- cd4T[!fData(cd4T)$symbol == "",] Now cd4T is an ExpressionSet object which wraps a big matrix with 19794 rows (probesets) and 15 columns (samples). The final line gets rid of all probesets that do not have corresponding gene symbols. Now the trouble is that most genes in this set are assigned to more than one probeset. You can see this by doing gene_symbols = factor(fData(cd4T)$Gene.symbol) length(gene_symbols)-length(levels(gene_symbols)) [1] 6897 So only 6897 of my 19794 probesets have unique probeset - gene mappings. I'd like to somehow combine the expression levels of each probeset associated with each gene. I don't care much about the actual probe id for each probe. I'd like very much to end up with an ExpressionSet containing the merged information as all of my downstream analysis is designed to work with this class. I think I can write some code that will do this by hand, and make a new expression set from scratch. However, I'm assuming this can't be a new problem and that code exists to do it, using a statistically sound method to combine the gene expression levels. I'm guessing there's a proper name for this also but my googles aren't showing up much of use. Can anyone help?

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• Alternative Python standard library reference

  - by Ender

  I love Python; I absolutely despise its official documentation. Tutorials do not count as library references, but that appears to be what they're attempting. What I really want is the ability to find a class in the standard library and view documentation for all of its properties and methods. Actionscript, MSDN, and Java all do this just fine (although each with their odd quirks). Where is this for python? For example, I wanted to sort a list. mylist.sort(). Awesome. But what if I wanted it sorted in descending order? Official documentation is not - much - help. Or what if I wanted to specify a key function? That's also supported: mylist.sort(key=lamba item: item.customVar)- but documented...where? I understand that Python's approach to OOP may not be equivalent to Java et. al. Maybe list isn't actually a class - maybe it's just a function that returns an iterable when the tachyon beams are set to glorious and the unboxed hyper enumeration is quantized, but...I don't care. I just want to know how to sort lists. (Apologies for the angst - too much caffeine today)

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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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• Re-using aggregate level formulas in SQL - any good tactics?

  - by Cade Roux

  Imagine this case, but with a lot more component buckets and a lot more intermediates and outputs. Many of the intermediates are calculated at the detail level, but a few things are calculated at the aggregate level: DECLARE @Profitability AS TABLE ( Cust INT NOT NULL ,Category VARCHAR(10) NOT NULL ,Income DECIMAL(10, 2) NOT NULL ,Expense DECIMAL(10, 2) NOT NULL ) ; INSERT INTO @Profitability VALUES ( 1, 'Software', 100, 50 ) ; INSERT INTO @Profitability VALUES ( 2, 'Software', 100, 20 ) ; INSERT INTO @Profitability VALUES ( 3, 'Software', 100, 60 ) ; INSERT INTO @Profitability VALUES ( 4, 'Software', 500, 400 ) ; INSERT INTO @Profitability VALUES ( 5, 'Hardware', 1000, 550 ) ; INSERT INTO @Profitability VALUES ( 6, 'Hardware', 1000, 250 ) ; INSERT INTO @Profitability VALUES ( 7, 'Hardware', 1000, 700 ) ; INSERT INTO @Profitability VALUES ( 8, 'Hardware', 5000, 4500 ) ; SELECT Cust ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Cust SELECT Category ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Category SELECT Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability Notice how the same formulae have to be used at the different aggregation levels. This results in code duplication. I have thought of using UDFs (either scalar or table valued with an OUTER APPLY, since many of the final results may share intermediates which have to be calculated at the aggregate level), but in my experience the scalar and multi-statement table-valued UDFs perform very poorly. Also thought about using more dynamic SQL and applying the formulas by name, basically. Any other tricks, techniques or tactics to keeping these kinds of formulae which need to be applied at different levels in sync and/or organized?

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• Is it possible to store controls(Panel) as object, serialize it and store it as a file?

  - by ikky

  The topic says it all. Using Compact Framework C# I'm tiling (order/sequence is important) some images that i download from an url, into a Panel(each image is a PictureBox). This can be a huge process, and may take some time. Therefor i only want the user to download the images and tile them once. So the next time the user uses the Tile Application, the Panel that was created the first time is already stored in a file and is loaded from that file. So what i want is a method to store a Panel as a file. Is this possible, or do you think i should do it another way? I've tried something like this: BinaryWriter panelStorage = new BinaryWriter(new FileStream("imagePanel.panel", FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)); Byte[] bImageObject = new Byte[20000]; bImageObject = (byte[])(object)this.imagePanel; panelStorage .Write(bMapObject); panelStorage .Close(); But the casting was not very legal :P "InvalidCastException" Can anyone help me with this problem? Thank you in advance!

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• Accessing class member variables inside a BackgroundWorker's DoWork event handler, and other Backgro

  - by Justin

  Question 1 In the DoWork event handler of a BackgroundWorker, is it safe to access (for both reading and writing) member variables of the class that contains the BackgroundWorker? Is it safe to access other variables that are not declared inside the DoWork event handler itself? Obviously DoWork should not be accessing any UI objects of, say, a WinForms application, as the UI should only be updated from the UI thread. But what about accessing other (not UI-related) member variables? The reason why I ask is that I've seen the occasional comment come up while Googling saying that accessing member variables is not allowed. The only example I can find at the moment is a comment on this MSDN page, which says: Note, that the BGW can cause exceptions if it attempts to access or modify class level variables. All data must be passed to it by delegates and events. And also: NEVER. NEVER. Never try to reference variables not declared inside of DoWork. It may seem to work at times, but in reality you are just getting lucky. As far as I know, MSDN itself does not document any restrictions of this kind (although if I'm wrong, I'd appreciate a link). But comments like these do seem to pop up every now and again. (Of course if DoWork does access/modify a member variable that could be accessed/modified by the main thread at the same time, it is necessary to synchronise access to that field, eg by using a locking object. But the above quotes seem to require a blanket ban of accessing member variables, rather than just synchronising access!) Question 2 To make this into a more general question, are there any other (not documented?) restrictions that users of the BackgroundWorker should be aware of, aside from the above? Any "best practices", perhaps?

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• Application Installation error Blackberry

  - by tek3

  Hi all, I have an application of mine on AppStore. But one user is complaining that he can not install the application on his device(Curve 8900) and it's giving error "Error starting AppName $28NonTouch$29: Module 'AppName $28NonTouch$29-2' has verification errors." Now how come it is possible that other's users are able to download properly while one user is getting this error. I downloaded the application from the appstore and its working perfectly. And when this user tries to install the application through Desktop Manager he is getting error "No additional applications can be found. Your file may contain applications that already exist in the application list, are not compatible for your device, or have errors." When i tried to stimulate the issue here by installing the application through desktop manager i am able to install it properly without any error messages. Can anyone suggest me ,what might be causing this issue.?? Is there any kind of version mismatch?? My application is compiled usiong jdk 4.5. Any help in this regard will be greatly appreciated. Kindly help,Its urgent.. Thanx in advance."

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• What algorithms are suitable for this simple machine learning problem?

  - by user213060

  I have a what I think is a simple machine learning question. Here is the basic problem: I am repeatedly given a new object and a list of descriptions about the object. For example: new_object: 'bob' new_object_descriptions: ['tall','old','funny']. I then have to use some kind of machine learning to find previously handled objects that had similar descriptions, for example, past_similar_objects: ['frank','steve','joe']. Next, I have an algorithm that can directly measure whether these objects are indeed similar to bob, for example, correct_objects: ['steve','joe']. The classifier is then given this feedback training of successful matches. Then this loop repeats with a new object. a Here's the pseudo-code: Classifier=new_classifier() while True: new_object,new_object_descriptions = get_new_object_and_descriptions() past_similar_objects = Classifier.classify(new_object,new_object_descriptions) correct_objects = calc_successful_matches(new_object,past_similar_objects) Classifier.train_successful_matches(object,correct_objects) But, there are some stipulations that may limit what classifier can be used: There will be millions of objects put into this classifier so classification and training needs to scale well to millions of object types and still be fast. I believe this disqualifies something like a spam classifier that is optimal for just two types: spam or not spam. (Update: I could probably narrow this to thousands of objects instead of millions, if that is a problem.) Again, I prefer speed when millions of objects are being classified, over accuracy. What are decent, fast machine learning algorithms for this purpose?

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• LaTex: why partially showing up references?

  - by HH

  The bib.style part may be the problem. If I do not reference to references, do they show up? I have listed all errors below, the file compiles so I don't know whether they are related to partially-showing-up-references. For example, work with many authors gets only one author listed. I want to see references fully, not partially. Headers $ grep bib header.tex \usepackage{natbib} \bibliographystyle{abbrvnat} Errors $ grep -n -A 7 -B 7 Error *.log combined.log-505-! Illegal unit of measure (pt inserted). combined.log-506-<to be read again> combined.log-507- \futurelet combined.log-508-l.353 \hline combined.log-509- combined.log-510-? combined.log-511- combined.log:512:! Package caption Error: cite undefined. combined.log-513- combined.log-514-See the caption package documentation for explanation. combined.log-515-Type H <return> for immediate help. combined.log-516- ... combined.log-517- combined.log-518-l.374 ...n={CPU O(mlog(n))}, cite={topcoder:node}] combined.log-519- -- combined.log-559- [] combined.log-560- combined.log-561-) [10] combined.log-562-\openout2 = `references.aux'. combined.log-563- combined.log-564- (./references.tex combined.log-565- combined.log:566:! LaTeX Error: \include cannot be nested. combined.log-567- combined.log-568-See the LaTeX manual or LaTeX Companion for explanation. combined.log-569-Type H <return> for immediate help. combined.log-570- ... combined.log-571- combined.log-572-l.1 \include{timeUse.tex} Bibs.bib @misc{ Gundersen, author = "G. Gundersen", title = "Data Structures in Java for Matrix Computations", year = "2002" } @book{ Lennart, author = "R. Lennart", title = "Mathematics Handbook for Science and Engineering BETA", year = "2004" }

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• Using Scala structural types with abstract types

  - by Joshua Hartman

  I'm trying to define a structural type defining anything that has an "add" method (for instance, a java collection or a java map). Using this, I want to define a few higher order functions that operate on a certain collection object GenericTypes { type GenericCollection[T] = { def add(value: T): java.lang.Boolean} } import GenericTypes._ trait HigherOrderFunctions[T, CollectionType[X] <: GenericCollection[X]] { def map[V](fn: (T) => V): CollectionType[V] .... } class RichJList[T](list: List[T]) extends HigherOrderFunctions[T, java.util.List] This does not compile with the following error error: Parameter type in structural refinement may not refer to abstract type defined outside that same refinement I tried removing the parameter on GenericCollection and putting it on the method: object GenericTypes { type GenericCollection = { def add[T](value: T): java.lang.Boolean} } import GenericTypes._ trait HigherOrderFunctions[T, CollectionType[X] <: GenericCollection] class RichJList[T](list: List[T]) extends HigherOrderFunctions[T, java.util.List] but I get another error: error: type arguments [T,java.util.List] do not conform to trait HigherOrderFunctions's type parameter bounds [T,CollectionType[X] <: org.scala_tools.javautils.j2s.GenericTypes.GenericCollection] Can anyone give me some advice on how to use structural typing with abstract typed parameters in Scala? Or how to achieve what I'm looking to accomplish? Thanks so much!

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• using JQuery and Prototype in the same page

  - by Don

  Hi, Several of my pages use both JQuery and Protoype. Since I upgraded to version 1.3 of JQuery this appears to be causing problems, because both libraries define a function named '$'. JQuery provides a function noConflict() which relinquishes control of $ to other libraries that may be using it. So it seems like I need to go through all my pages that look like this: <head> <script type="text/javascript" src="/obp/js/prototype.js"></script> <script type="text/javascript" src="/obp/js/jquery.js"></script> </head> and change them to look like this: <head> <script type="text/javascript" src="/obp/js/prototype.js"></script> <script type="text/javascript" src="/obp/js/jquery.js"></script> <script type="text/javascript"> jQuery.noConflict(); var $j = jQuery; </script> </head> I should then be able to use '$' for Prototype and '$j' (or 'jQuery') for JQuery. I'm not entirely happy about duplicating these 2 lines of code in every relevant page, and expect that at some point somebody is likely to forget to add them to a new page. I'd prefer to be able to do the following Create a file jquery-noconflict.js which "includes" jquery.js and the 2 lines of code shown above Import jquery-noconflict.js (instead of jquery.js) in all my JSP/HTML pages However, I'm not sure if it's possible to include one JS file in another, in the manner I've described? Of course an alternate solution is simply to add the 2 lines of code above to jquery.js directly, but if I do that I'll need to remember to do it every time I upgrade JQuery. Thanks in advance, Don

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• Full text index requires dropping and recreating - why?

  - by Amjid Qureshi

  Hi all, So I've got a web app running on .net 3.5 connected to a SQL 2005 box. We do scheduled releases every 2 weeks. About 14 tables out of 250 are full text indexed. After not every release, but a few too many, the indexes crap out. They seem to have data in there, but when we try to search them from the front end or SQL enterprise we get timeouts/hangs. We have a script that disables the indexes, drops them, deletes the catalog and then re creates the indexes. This fixes the problem 99 times out of 100. and the one other time, we run the script again and it all works We have tried just rebuilding the fulltext index but that doesn't fix the issue. My question is why do we have to do this ? what can we do to sort the index out? Here is a bit of the script, IF EXISTS (SELECT * FROM sys.fulltext_indexes fti WHERE fti.object_id = OBJECT_ID(N'[dbo].[Address]')) ALTER FULLTEXT INDEX ON [dbo].[Address] DISABLE GO IF EXISTS (SELECT * FROM sys.fulltext_indexes fti WHERE fti.object_id = OBJECT_ID(N'[dbo].[Address]')) DROP FULLTEXT INDEX ON [dbo].[Address] GO IF EXISTS (SELECT * FROM sysfulltextcatalogs ftc WHERE ftc.name = N'DbName.FullTextCatalog') DROP FULLTEXT CATALOG [DbName.FullTextCatalog] GO -- may need this line if we get an error BACKUP LOG SMS2 WITH TRUNCATE_ONLY CREATE FULLTEXT CATALOG [DbName.FullTextCatalog] ON FILEGROUP [FullTextCatalogs] IN PATH N'F:\Data' AS DEFAULT AUTHORIZATION [dbo] CREATE FULLTEXT INDEX ON [Address](CommonPlace LANGUAGE 'ENGLISH') KEY INDEX PK_Address ON [DbName.FullTextCatalog] WITH CHANGE_TRACKING AUTO go

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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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• Problems running Ruby on Rails apps on shared hosted server

  - by Evgeny

  I have problems installing any Ruby On Rails app on my shared hosted server. Mongrel shows html as plain text for all pages. The problem occurs for any app, even if I create a test empty app and add a scaffolded view without changing anything. It appears that the Mongrel crashes when trying to put cookies to the response header. The HTTP header looks incomplete, the Content-type and other parameters are missing: curl 127.0.0.1:12002/users -I HTTP/1.1 200 OK Connection: close Date: Wed, 26 May 2010 09:46:50 GMT Content-Length: 0 Here is the output from mongrel.log Error calling Dispatcher.dispatch #<NoMethodError: You have a nil object when you didn't expect it! You might have expected an instance of ActiveRecord::Base. The error occurred while evaluating nil.[]> /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/cgi.rb:108:in `send_cookies' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/cgi.rb:136:in `out' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/mongrel/http_response.rb:65:in `start' ruby 1.8.7 rails 2.3.8 mongrel 1.1.5 Here is the link to the test page. Has anyone seen anything like this?

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• Lightweight spinlocks built from GCC atomic operations?

  - by Thomas

  I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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• Why does my DataTemplate break the WPF designer?

  - by PRINCESS FLUFF

  Why does the DataTemplate line break the WPF designer in Visual Studio 2008? The program compiles and runs properly. The DataTemplate is applied as it should. However the entire DataTemplate block of code is underlined in red, and when I simply "build" the program without running, I get the error "Type reference cannot find public type named 'Character'" How come it can't find it in the designer yet the program applies the template properly? <UserControl x:Class="WPF_Tests.Tests.TwoCollecViews.TwoViews" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:DetailsPane="clr-namespace:WPF_Tests.Tests.DetailsPane" > <UserControl.Resources> <DataTemplate DataType="{x:Type DetailsPane:Character}"> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding Path=Name}"></TextBlock> </StackPanel> </DataTemplate> </UserControl.Resources> <Grid> <ListBox ItemsSource="{Binding Path=Characters}" /> </Grid> </UserControl> EDIT: I am being told that this may be a bug in Visual Studio 2008, as it worked correctly in 2010. You can download the code here: http://www.mediafire.com/?z1myytvwm4n - The Test/TwoCollec xaml file's designer will break with this code.

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• How does MSN filter spam?

  - by Marius

  I am trying to create a newsletter for our business. The last few days have been spent testing, and one of things I have noticed is that MSN seemingly randomly filters out some of my test messages. This is super-frustrating. I like the PEAR Mail MIME-package, and have been using that. I may send one email from one of our servers, resulting in the message getting through, and in the next minute, the same message sent from our other server ends up in the junk folder. Then if I add an attachment to the email, and the same message passes though the filter from the server that was previously blocked. I think. What the ####? Is this like throwing a dice, without me having any control over what is trash, and what isn't? I have sent email from several servers, all of which are shared. But I am unsure this is the problem. The problem is that it is seemingly random how MSN filters email. Some emails get through, and some other don't for seemingly irrational reasons. I am running out of ideas, but I am not giving up. Therefore I am writing to you for HARDCORE technical info on how MSN filters spam.

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• Silverlight 4 seems like starving of memory

  - by Marco

  I have been playing a bit with Silverlight and try to port my Silverlight 3.0 application to Silverlight 4.0. My application loads different XAP files and upon a user request create an instance of a Xaml user control and adds it to the main container, in a sort of MEF approach in order I can have an extensible and pluggable application. The application is pretty huge and to keep acceptable the performances and the initial loading I have built up some helper classes to load in the background all pages and user controls that might be used later on. On Silverlight 3.0 everything was running smoothly without any problem so far. Switching to SL 4.0 I have noticed that when the process approaches to create the instances of the user controls the layout freezes unexpectedly for a minute and sometimes for more. Looking at the task manager the memory usage of IE jumps from 50MB to 400MB and sometimes up to 1.5 GB. If the process won't take that much the layout is rendered properly even though the memory usage is still extremely high. Otherwise everything crashes due to out of memory exception. Running the same application compiled in SL3, the memory used is about 200MB when all the usercontrols are loaded. Time spent to load the application in SL3 is about 10 seconds, while it takes up to 3 mins in SL4 There are no transparencies, no opacities set, no effects and animations in the layout. User controls are instantied on the fly and added or removed in the visual tree on purpose when the user switches from one screen to another. The resources are all cleaned properly when a usercontrol is removed from the visual tree to allow the GC to operate in the background. I may do something wrong but I could not figure out where exactly nail out the source of this problem. As far as I know there is no memory profiler in SL4 that can help me out to find where to look at. But again I could not be updated on new debugging tools available.

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• Application passwords and SQLite security

  - by Bryan

  I have been searching on google for information regarding application passwords and SQLite security for some time, and nothing that I have found has really answered my questions. Here is what I am trying to figure out: 1) My application is going to have an optional password activity that will be called when the application is first opened. My questions for this are a) If I store the password via android preference or SQLite database, how can I ensure security and privacy for the password, and b) how should password recovery be handled? Regarding b) from above, I have thought about requiring an email address when the password feature is enabled, and also a password hint question for use when requesting password recovery. Upon successfully answering the hint question, the password is then emailed to the email address that was submitted. I am not completely confident in the security and privacy of the email method, especially if the email is sent when the user is connected to an open, public wireless network. 2) My application will be using an SQLite database, which will be stored on the SD card if the user has one. Regardless of whether it is stored on the phone or the SD card, what options do I have for data encryption, and how does that affect the application performance? Thanks in advance for time taken to answer these questions. I think that there may be other developers struggling with the same concerns.

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• NetBeans Tips and Tricks

  - by cdmckay

  I just saw an Eclipse tips & tricks post and was wondering if anyone had any tips & tricks for my IDE of choice: NetBeans. Here's a few I know and find to be useful: Removing a package: After you remove a package in NetBeans, it sticks around as a grayed-out package in your Project view. To get rid of that, switch to Files view and delete the directory. Alt-Insert (in Windows) opens up a Generate submenu at your cursor. A nice shortcut for quickly generating getters/setters (among other things). Selecting a chunk of code, right-clicking and then clicking "Refactor Introduce Method" will have NetBeans introduce a method, complete with arguments and return value. Of course you have to make sure the chunk of code only has one return value. Sometimes when you run a build and it crashes, the Java window sticks around at the bottom. I used to just click X until Windows let me End Task, but there's a nicer way to get rid of them. Click "Run Stop Build/Run" and NetBeans will close the window for you. It'll even let you close multiple applications at once. These may seem obvious to grizzled NetBeans developers, but I thought they might be useful for NetBeans newbs like me. Anyone else have any tips/tricks to share? Here are some from the comments: NetBeans allows for code templates. You can even add yours on the Code Templates tab under the Editor settings on the Options window. Some examples: Type sout and hit the tab key as a shorcut for System.out.println("") Type psvm and hit the tab key as a shorcut for public static void main(String args[]) {} Ctrl Shift C: Comments out the selected block of code. Alt Shift F: Formats the selected block of code. Ctrl E: Deletes current line. Ctrl Shift I: Fixes your imports, handy if you've just written a piece of code that needs a lot of packages imported.

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• Database design for sharing photos site?

  - by javaLearner.java

  I am using php and mysql. If I want to do a sharing photos website, whats the best database design for upload and display photos. This is what I have in mind: domain: |_> photos |_> user Logged in user will upload photo in [http://www.domain.com/user/upload.php] The photos are stored in filesystems, and the path-to-photos stored in database. So, in my photos folder would be like: photos/userA/subfolders+photos, photos/userB/subfolders+photos, photos/userC/subfolders+photos etc Public/others people may view his photo in: [http://www.domain.com/photos/user/?photoid=123] where 123 is the photoid, from there, I will query from database to fetch the path and display the image. My questions: Whats the best database design for photo-sharing website (like flickr)? Will there be any problems if I keep creating new folder in "photos" folder. What if hundreds of thousands users registered? Whats the best practices What size of photos should I keep? Currently I only stored thumbnail (100x100) and (max) 1600x1200 px photos. What others things I should take note when developing photos-sharing website?

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