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• c++11 atomic ordering: extended total order memory_order_seq_cst for locks

  - by itaj

  There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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• Hebbian learning

  - by Bane

  I have asked another question on Hebbian learning before, and I guess I got a good answer which I accepted, but, the problem is that I now realize that I've mistaken about Hebbian learning completely, and that I'm a bit confused. So, could you please explain how it can be useful, and what for? Because the way Wikipedia and some other pages describe it - it doesn't make sense! Why would we want to keep increasing the weight between the input and the output neuron if the fire together? What kind of problems can it be used to solve, because when I simulate it in my head, it certainly can't do the basic AND, OR, and other operations (say you initialize the weights at zero, the output neurons never fire, and the weights are never increased!)

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• Boost Filesystem Library Visual C++ Compile Error

  - by John Miller

  I'm having the following issue just trying to compile/run some of the example programs with the Boost Filesystem Library. I'm using MS-Visual C++ with Visual Studio .NET (2003). I've installed the Boost libraries, version 1.38 and 1.39 (just in case there was a version problem) using the BoostPro installers. If I just try to include /boost/filesystem/operations.hpp I receive the following error: \boost_1_38\boost\system\error_code.hpp(230) : error C2039: 'type' : is not a member of 'boost::enable_if<boost::system::is_error_condition_enum<Cond,boost::detail::enable_if_default_T>' Any help is greatly appreciated. Thank you!

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• Correct (pretty) window redraw during the creation

  - by Coder

  Does anyone know what is a correct way to redraw window during lengthy initialization operations? Say I have HWND with NULL brush, and it does some not so quick child window initialization (Window initialization is not so quick on Vista and 7, especially on netbooks, even with threaded app). With this config window stays black for half a second on slower laptops. But if I supply window color brush, it seems that there are some sort of child controls or something that draws black squares on top of it, which also seems ugly. Even though the controls are created without WS_VISIBLE initially. Oh, the window has the WS_EX_COMPOSITED style, which should do the double buffering to avoid flicker. But it still behaves ugly. Are there any other tricks I've forgotten, missed?

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• Storing And Using Microsoft User Account Credentials in SQL Server 2008 database

  - by user337501

  I'm not exactly positive how to word this for the sake of the title so please forgive me. Also I can't seem to figure out how to even google this question, so I'm hoping that I can get a lead in the right direction. Part of my software(VB.NET App) requires the ability to access/read/write a shared network folder. I have an option for the user to specify any credentials that might be needed to access said folder. I want to store these credentials given in the SQL Server database as part of the config (I have a table which contains configuration). My concern is that the password for the user account will be unencrpyted. Yet, if I encrypt the password the VB.NET App And/Or database will be unable to use the credentials for file i/o operations unless the Password is unencrypted before use. I'm fishing for suggestions on how to better handle this situation.

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• Is passing a Command object/Reader to a function a good idea?

  - by Cyril Gupta

  I've been getting some inexplicable errors (running out of connections from the connection pool) with MySql database with .Net 4 (C#). Till now all my attempts at finding a reason for this have been in vain. Now I also have a situation in which a lock on a table is not cleared for a long time even though all I have been doing is read operations from it. My code looks okay (I've put all readers and connections in using blocks). The only anomaly I have is that I've been passing MySqlCommand and MySqlDataReader objects as parameters to functions who work with them. That doesn't seem like a bad idea for me because it avoids some repetition (DRY!). But since I can't find any other explanation I have to suspect that this is causing the problem. What do you think?

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• How to limit data to users who own it without limiting admin users in CakePHP?

  - by cdburgess

  Currently I am writing an application where I have multiple users. They have data that should only be visible to them and not the other authenticated users in the system. I also have administrators who manage the system and have access to all of the information. What is the best way to limit users to their data without limiting admin users? Currently I am using a callback to limit the queries by user, but the admin will get the same limits. So I need to know a better way to do it. More importantly, the right way to do it. For example, I want the standard user to be able to see their user information only and be limited to CRUD operations on their information only. The admin, however, should be able to see ALL users and CRUD ALL user data. Any ideas?

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• Git - will the file moves be detected?

  - by Ben Aston

  I performed some modifications on a branch (A). I then decided to create a brand new branch (B) based on the state of my existing working copy and commit and push to that. There were a number of files that had been moved during my earlier refactoring, and hence were now not included in version control having been moved directly in the filesystem. By accident I did not add these files to git before committing and pushing to the new branch (B). If I now add these files and commit and push, will Git be able to detect the file move operations?

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• static, define, and const in C

  - by yCalleecharan

  Hi, I've read that static variables are used inside function when one doesn't want the variable value to change/initialize each time the function is called. But what about defining a variable static in the main program before "main" e.g. #include <stdio.h> static double m = 30000; int main(void) { value = m * 2 + 3; } Here the variable m has a constant value that won't get modified later in the main program. In the same line of thought what difference does it make to have these instead of using the static definition: const double m = 30000; or #define m 30000 //m or M and then making sure here to use double operations in the main code so as to convert m to the right data type. Thanks a lot...

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• Rollback to a specific moment with PostgreSQL

  - by mada54

  Hi, Is there a way to rollback to a specific starting point. Im looking for something like this. Start specific_point; Now after this, an other application connected with the SAME login will insert & delete datas (webservices with crud operations) for about 2 minutes doing tests. Each webservice call is declared as a transaction with Spring Ws. After that i want to rollback to the specific_point to have a clean database to a known previous state. I was thinking that ROLLBACK TO SAVEPOINT foo; was the solution but not unfortunately? Any idea ? Configuration: PostgreSQL 8.4 / windows XP Regards

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• Which database engines support IP addresses as a native type?

  - by Matt McClellan

  I'm trying to find databases with support for IP addresses as a native type (as opposed to storing as a string, or an unsigned integer, which at least one commenter has already pointed out won't work for IPv6). The primary reason I'm looking for this is ease of development. For example, sorting on a "native" IP address column would be correct (as opposed to when it's stored as a string). I would assume support for such a type would also include useful operations such as determining if an IP address is inside a specified network for use in WHERE clauses. The only one I'm aware of so far is PostgreSQL with its inet class. Does anyone have any others?

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• desktop module for existing web application

  - by maxxxee

  My client has a running web application which has been online for more than a year. Recently the client has introduced smart cards for his employees. Because of the difficulty in integrating smart card with its api on a web interface(i will post another detailed question on this later) we are planning to have desktop interface for this. There are 10-20 terminals which will use the desktop interface. 3 approaches for doing this that I have considered : Direct connection and operations on DB-Not using this because of data integrity and consistency issues. Build web service end points and use it from desktop interface Build a dll with common functions and use from both web and desktop Questions: 1. What are your opinions based on 2 and 3 approach? 2. Any other approach that I should consider? Note: I am using .Net framework, web application in asp.net

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• Fast, Vectorizable method of taking floating point number modulus of special primes?

  - by caffiend

  Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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• How to use SQL trigger to record the affected column's row number

  - by Freeman

  I want to have an 'updateinfo' table in order to record every update/insert/delete operations on another table. In oracle I've written this: CREATE TABLE updateinfo ( rnumber NUMBER(10), tablename VARCHAR2(100 BYTE), action VARCHAR2(100 BYTE), UPDATE_DATE date ) DROP TRIGGER TRI_TABLE; CREATE OR REPLACE TRIGGER TRI_TABLE AFTER DELETE OR INSERT OR UPDATE ON demo REFERENCING NEW AS NEW OLD AS OLD FOR EACH ROW BEGIN if inserting then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'insert',sysdate); elsif updating then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'update',sysdate); elsif deleting then insert into updateinfo(rnumber,tablename,action,update_date ) values(rownum,'demo', 'delete',sysdate); end if; -- EXCEPTION -- WHEN OTHERS THEN -- Consider logging the error and then re-raise -- RAISE; END TRI_TABLE; but when checking updateinfo, all rnumber column is zero. is there anyway to retrieve the correct row number?

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• Known problems with filemtime() on Windows - files getting touched arbitrarily?

  - by Pekka

  Is there a known issue leading to file modification times of cache files on Windows XP SP 3 getting arbitrarily updated, but without any actual change? Is there some service on a standard Windows XP - Backup, Sync, Versioning, Virus scanner - known to touch files? They all have a .txt extension. If there isn't, forget it. Then I'm getting something wrong in my cache routines, and I'll debug my way through. Background: I'm building a simple caching wrapper around a slow web site on a Windows server. I am comparing the filemtime() time stamp to some columns in the data base to determine whether a cached file is stale. I'm having problems using this method because the modification time of the cache files seems to get updated in between operations without me doing anything. THis results in stale files being displayed. I'm the only user on the machine. The operating system is Windows XP, the webserver a XAMPP Apache 2 with PHP 5.2

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• Very Different Execution Times of SQL Query in C# and SQL Server Management Studio

  - by Paul

  I have a simple SQL query that when run from C# takes over 30 seconds then times-out every time, whereas when run on SQL Server Management Studio successfully completes instantly. In the latter case, a query execution plan reveals nothing troubling, and the execution time is spread nicely through a few simple operations. I've run 'EXEC sp_who2' while the query is running from C#, and it is listed as taking 29,000 milliseconds of CPU time, and is not blocked by anything. I have no idea how to begin solving this. Does anyone have some insight? The query is: SELECT c.lngId, ... FROM tblCase c INNER JOIN tblCaseStatus s ON s.lngId = c.lngId INNER JOIN tblCaseStatusType t ON t.lngId = s.lngId INNER JOIN [Another Database]..tblCompany cm ON cm.lngId = cs.lngCompanyId WHERE t.lngId = 25 AND c.IsDeleted = 0 AND s.lngStatus = 1

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• How does Ruby's Enumerator object iterate externally over an internal iterator?

  - by Salman Paracha

  As per Ruby's documentation, the Enumerator object uses the each method (to enumerate) if no target method is provided to the to_enum or enum_for methods. Now, let's take the following monkey patch and its enumerator, as an example o = Object.new def o.each yield 1 yield 2 yield 3 end e = o.to_enum loop do puts e.next end Given that the Enumerator object uses the each method to answer when next is called, how do calls to the each method look like, every time next is called? Does the Enumeartor class pre-load all the contents of o.each and creates a local copy for enumeration? Or is there some sort of Ruby magic that hangs the operations at each yield statement until next is called on the enumeartor? If an internal copy is made, is it a deep copy? What about I/O objects that could be used for external enumeration? I'm using Ruby 1.9.2.

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• bitfield mask calculation macro

  - by Aidan Cully

  We have a set of C macros, here, for using the preprocessor to do bitfield operations, and we run into warnings when attempting to use these macros in visual studio. The problem can be demonstrated very easily: #define BITFIELD_WIDTHMASK(Width) \ ((Width) >= 32 ? ~0x0ul : (1ul << (Width)) - 1) unsigned long foo(void) { return BITFIELD_WIDTHMASK(32); } Compiling this with MSVC yields the warning: test.c(12) : warning C4293: '<<' : shift count negative or too big, undefined behavior This isn't a behavior problem - the << operator won't be used in this case, and that should be detected at compile time. But does anyone have any suggestions about how to rewrite the macro to avoid the warning? Or, failing that, how to redesign the macro interface for this? Thanks in advance

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• A 4-byte Unsigned Int for Sql Server 2008?

  - by Jeff Meatball Yang

  I understand there are multiple questions about this on SO, but I have yet to find a definitive answer of "yes, here's how..." So here it is again: What are the possible ways to store an unsigned integer value (32-bit value or 32-bit bitmap) into a 4-byte field in SQL Server? Here are ideas I have seen: 1) Use a -1*2^31 offset for all values Disadvantages: need to perform math on the values before reading/writing/aggregating. 2) Use 4 tinyint fields Disadvantages: need to concatenate values to perform any operations 3) Use binary(4) Disadvantages: actually uses 4 + 2 bytes of space

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• Is this bad style of programming(C#) ?

  - by m0s

  Hi, so in my program I have parts where I use try catch blocks like this try { DirectoryInfo dirInfo = new DirectoryInfo(someString); //I don't know if that directory exists //I don't know if that string is valid path string... it could be anything //Some operations here } catch(Exception iDontCareWhyItFailed) { //Didn't work? great... we will say: somethings wrong, try again/next one } Of course I probably could do checks to see if the string is valid path (regex), then I would check if directory exists, then I could catch various exceptions to see why my routine failed and give more info... But in my program it's not really necessary. Now I just really need to know if this is acceptable, and what would a pro say/think about that. Thanks a lot for attention.

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• Python CSV file processing

  - by kingwarchief

  I just got introduced to python, the first language I get to learn, and I have this question below: I have an excel based CSV file with two columns (or rows, Pythonically) that I am working on. What I need to do is to perform some operations so that I can compare the two data entries in each 'row'. To be more precise, one column has constant numbers all the way down, whereas the other column varies. So I need to count the number of times the varying column data entry values crosses the constant value on the other column. For example: Varying Column; Constant Column 24 25 26 25 crosses 27 25 26 25 25.5 25 23 25 crossed 26 25 crossed So in this case the number of times there is a cross

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• NHibernate auditing in disconnected mode

  - by Ciaran

  I'm developing an app with a Silverlight UI, transferring my domain objects over WCF and persisting them via NHibernate. I'm therefore working with NHibernate in a disconnected mode. I'm already using the NHibernate PreUpdate and PreInsert EventListeners to perform some metadata operations (updating Create/Update date, created/updated by etc) and they are working fine. I now have a requirement to perform data logging on some of my domain objects. So I will need to have an audit table that has a before-save and after-save state of certain entities. I had wanted to use the @event.Persister.OldState and @event.Persister.NewState to perform this logging, but because I am in a disconnected scenario (using different Sessions from when data is retrieved to when it is persisted), @event.Persister.OldState is null when I am saving my changes back to the database. How is anyone else doing data logging in a disconnected scenario with NHibernate?

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• Transaction within transaction

  - by user281521

  Hello, I want to know if open a transaction inside another is safe and encouraged? I have a method: def foo(): session.begin try: stuffs except Exception, e: session.rollback() raise e session.commit() and a method that calls the first one, inside a transaction: def bar(): stuffs try: foo() #<<<< there it is :) stuffs except Exception, e: session.rollback() raise e session.commit() if I get and exception on the foo method, all the operations will be rolled back? and everything else will work just fine? thanks!!

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• How do I count the number of bytes read by TextReader.ReadLine()?

  - by Steve Guidi

  I am parsing a very large file of records (one per line, each of varying length), and I'd like to keep track of the number of bytes I've read in the file so that I may recover in the event of a failure. I wrote the following: string record = myTextReader.ReadLine(); bytesRead += record.Length; ParseRecord(record); However this doesn't work since ReadLine() strips any CR/LF characters in the line. Furthermore, a line may be terminated by either CR, LF, or CRLF characters, which means I can't just add 1 to bytesRead. Is there an easy way to get the actual line length, or do I write my own ReadLine() method in terms of the granular Read() operations?

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• How to design WCF Contracts?

  - by Amitabh

  We are designing a WCF layer which can be invoked either by a Asp.Net or a WinForm application. Our Application contains too many Entities. If we design WCF Contract around these entities then we get too many Contracts e.g IPartyService, IUserService, IPaymentService etc. So, I may end up with 30-40 Contracts? Is it a good idea or should we go for one huge contracts with around 100 operations? What are the pros and cons of each approach or is there a better way.

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