Search Results

Search found 14169 results on 567 pages for 'parallel programming'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 243/567 | < Previous Page | 239 240 241 242 243 244 245 246 247 248 249 250  | Next Page >

  • Yet another question about C++ books..

    - by suicideducky
    Intro rant Hey all, so after just over a year of browsing I decided it's time to ask a question for myself, it's sadly similar to many that have been asked before. I'm 18, am studying towards a BSc in Comp SCi and have been programming 'on and off' for about 6 years now, after wrestling with C++ for a bit then stumbling upon (and reading cover to cover) "Programming: Principles and Practice Using C++" by the great man himself I feel pretty comfortable with C++, I am almost finished writing my first open source program in C++ (a mediawiki parser, http://code.google.com/p/apertium-mediawiki/). I have decided I want to really get to know the power of C++, get familiar with some of its 'darker' corners and also delve into game programming, at this point I am rather keen on the book "Essential 3D Game Programming: with C++ and OpenGL" (released 24 may '10), I would also like to get 1 or 2 other books on 'general C++' that I can read cover to cover during my spare time. At this point I am pretty open to suggestions I would like something in the intermediate/advanced zone, some books I am rather keen on include: The C++ Standard Library: A tutorial and reference, C++ Template, the complete guide, and Modern C++ Design: Generic Programming and Design Patterns Applied Thanks in advance.

    Read the article

  • Must JsUnit Cases Reside Under the Same Directory as JsUnit?

    - by chernevik
    I have installed JsUnit and a test case as follows: /home/chernevik/Programming/JavaScript/jsunit /home/chernevik/Programming/JavaScript/jsunit/testRunner.html /home/chernevik/Programming/JavaScript/jsunit/myTests/lineTestAbs.html /home/chernevik/Programming/JavaScript/lineTestAbs.html When I open the test runner in a browser as a file, and test lineTestAbs.html from the jsunit/myTests directory, it passes. When I test the same file from the JavaScript directory, the test runner times out, asking if the file exists or is a test page. Questions: Am I doing something wrong here, or is this the expected behavior? Is it possible to put test cases in a different directory structure, and if so what is the proper path reference to to JsUnitCore.js? Would JsUnit behave differently if the files were retrieved from an HTTP server? <html> <head> <title>Test Page line(m, x, b)</title> <script language="JavaScript" src="/home/chernevik/Programming/JavaScript/jsunit/app/jsUnitCore.js"></script> <script language="JavaScript"> function line(m, x, b) { return m*x + b; } function testCalculationIsValid() { assertEquals("zero intercept", 10, line(5, 2, 0)); assertEquals("zero slope", 5, line(0, 2, 5)); assertEquals("at x = 10", 25, line(2, 10, 5)); } </script> </head> <body> This pages tests line(m, x, b). </body> </html>

    Read the article

  • Where is Prolog used for traffic control systems?

    - by Masi
    The user Laurent had an interesting reply to the question [Why hasn’t logic programming caught on?]: If you look at the influence logic-programming has had in the field of -- air traffic control -- I don't think it can be said logic-programming has not caught on. A question arises: Where is prolog used for traffic control systems on the roads? Why is it used instead of languages, such as C or Python, in such environments?

    Read the article

  • Oracle pl\sql question for my homework in oracle 11G class [migrated]

    - by Bjolds
    I am new to oracle 11G programming and i have run into a tough situation with pl\sql funtions and automation. I ame unsure how to create the function for the automation of Registration system for a College registration system. Here is what i want to do. I want to automate the registrations system so that it automaticly registers students. Then I want a procedure to automate the grading system. I have included the code that i am written to make most of this assignment work which it does but unsure how to incorporate Pl\SQL automated fuctions for the registrations system, and the grading system. So Any help or Ideas I would greatly appreciate please. set Linesize 250 set pagesize 150 drop table student; drop table faculty; drop table Course; drop table Section; drop table location; DROP TABLE courseInstructor; DROP TABLE Registration; DROP TABLE grade; create table student( studentid number(10), Lastname varchar2(20), Firstname Varchar2(20), MI Char(1), address Varchar2(20), city Varchar2(20), state Char(2), zip Varchar2(10), HomePhone Varchar2(10), Workphone Varchar2(10), DOB Date, Pin VARCHAR2(10), Status Char(1)); ALTER TABLE Student Add Constraint Student_StudentID_pk Primary Key (studentID); Insert into student values (1,'xxxxxxxx','xxxxxxxxxx','x','xxxxxxxxxxxxxxx','Columbus','oh','44159','xxx-xxx-xxxx','xxx-xxx-xxxx','06-Mar-1957','1211','c'); create table faculty( FacultyID Number(10), FirstName Varchar2(20), Lastname Varchar2(20), MI Char(1), workphone Varchar2(10), CellPhone Varchar2(10), Rank Varchar2(20), Experience Varchar2(10), Status Char(1)); ALTER TABLE Faculty ADD Constraint Faculty_facultyId_PK PRIMARY KEY (FacultyID); insert into faculty values (1,'xxx','xxxxxxxxxxxx',xxx-xxx-xxxx','xxx-xxx-xxxx','professor','20','f'); create table Course( CourseId number(10), CourseNumber Varchar2(20), CourseName Varchar(20), Description Varchar(20), CreditHours Number(4), Status Char(1)); ALTER TABLE Course ADD Constraint Course_CourseID_pk PRIMARY KEY(CourseID); insert into course values (1,'cit 100','computer concepts','introduction to PCs','3.0','o'); insert into course values (2,'cit 101','Database Program','Database Programming','4.0','o'); insert into course values (3,'Math 101','Algebra I','Algebra I Concepts','5.0','o'); insert into course values (4,'cit 102a','Pc applications','Aplications 1','3.0','o'); insert into course values (5,'cit 102b','pc applications','applications 2','3.0','o'); insert into course values (6,'cit 102c','pc applications','applications 3','3.0','o'); insert into course values (7,'cit 103','computer concepts','introduction systems','3.0','c'); insert into course values (8,'cit 110','Unified language','UML design','3.0','o'); insert into course values (9,'cit 165','cobol','cobol programming','3.0','o'); insert into course values (10,'cit 167','C++ Programming 1','c++ programming','4.0','o'); insert into course values (11,'cit 231','Expert Excel','spreadsheet apps','3.0','o'); insert into course values (12,'cit 233','expert Access','database devel.','3.0','o'); insert into course values (13,'cit 169','Java Programming I','Java Programming I','3.0','o'); insert into course values (14,'cit 263','Visual Basic','Visual Basic Prog','3.0','o'); insert into course values (15,'cit 275','system analysis 2','System Analysis 2','3.0','o'); create table Section( SectionID Number(10), CourseId Number(10), SectionNumber VarChar2(10), Days Varchar2(10), StartTime Date, EndTime Date, LocationID Number(10), SeatAvailable Number(3), Status Char(1)); ALTER TABLE Section ADD Constraint Section_SectionID_PK PRIMARY KEY(SectionID); insert into section values (1,1,'18977','r','21-Sep-2011','10-Dec-2011','1','89','o'); create table Location( LocationId Number(10), Building Varchar2(20), Room Varchar2(5), Capacity Number(5), Satus Char(1)); ALTER TABLE Location ADD Constraint Location_LocationID_pk PRIMARY KEY (LocationID); insert into Location values (1,'Clevleand Hall','cl209','35','o'); insert into Location values (2,'Toledo Circle','tc211','45','o'); insert into Location values (3,'Akron Square','as154','65','o'); insert into Location values (4,'Cincy Hall','ch100','45','o'); insert into Location values (5,'Springfield Dome','SD','35','o'); insert into Location values (6,'Dayton Dorm','dd225','25','o'); insert into Location values (7,'Columbus Hall','CB354','15','o'); insert into Location values (8,'Cleveland Hall','cl204','85','o'); insert into Location values (9,'Toledo Circle','tc103','75','o'); insert into Location values (10,'Akron Square','as201','46','o'); insert into Location values (11,'Cincy Hall','ch301','73','o'); insert into Location values (12,'Dayton Dorm','dd245','57','o'); insert into Location values (13,'Springfield Dome','SD','65','o'); insert into Location values (14,'Cleveland Hall','cl241','10','o'); insert into Location values (15,'Toledo Circle','tc211','27','o'); insert into Location values (16,'Akron Square','as311','28','o'); insert into Location values (17,'Cincy Hall','ch415','73','o'); insert into Location values (18,'Toledo Circle','tc111','67','o'); insert into Location values (19,'Springfield Dome','SD','69','o'); insert into Location values (20,'Dayton Dorm','dd211','45','o'); Alter Table Student Add Constraint student_Zip_CK Check(Rtrim (Zip,'1234567890-') is null); Alter Table Student ADD Constraint Student_Status_CK Check(Status In('c','t')); Alter Table Student ADD Constraint Student_MI_CK2 Check(RTRIM(MI,'abcdefghijklmnopqrstuvwxyz')is Null); Alter Table Student Modify pin not Null; Alter table Faculty Add Constraint Faculty_Status_CK Check(Status In('f','a','i')); Alter table Faculty ADD Constraint Faculty_Rank_CK Check(Rank In ('professor','doctor','instructor','assistant','tenure')); Alter table Faculty ADD Constraint Faculty_MI_CK2 Check(RTRIM(MI,'abcdefghijklmnopqrstuvwxyz')is Null); Update Section Set Starttime = To_date('09-21-2011 6:00 PM', 'mm-dd-yyyy hh:mi pm'); Update Section Set Endtime = To_date('12-10-2011 9:50 PM', 'mm-dd-yyyy hh:mi pm'); alter table Section Add Constraint StartTime_Status_CK Check (starttime < Endtime); Alter Table Section Add Constraint Section_StartTime_ck check (StartTime < EndTime); Alter Table Section ADD Constraint Section_CourseId_FK FOREIGN KEY (CourseID) References Course(CourseId); Alter Table Section ADD Constraint Section_LocationID_FK FOREIGN KEY (LocationID) References Location (LocationId); Alter Table Section ADD Constraint Section_Days_CK Check(RTRIM(Days,'mtwrfsu')IS Null); update section set seatavailable = '99'; Alter Table Section ADD Constraint Section_SeatsAvailable_CK Check (SeatAvailable < 100); Alter Table Course Add Constraint Course_CreditHours_ck check(CreditHours < = 6.0); update location set capacity = '99'; Alter Table Location Add Constraint Location_Capacity_CK Check(Capacity < 100); Create Table Registration ( StudentID Number(10), SectionID Number(10), Constraint Registration_pk Primary key (studentId, Sectionid)); Insert into registration values (1, 2); Insert into Registration values (2, 3); Insert into registration values (3, 4); Insert into registration values (4, 5); Insert into registration values (5, 6); Insert into registration values (6, 7); Insert into registration values (7, 8); Insert into registration values (8, 9); insert into registration values (9, 10); insert into registration values (10, 11); insert into registration values (9, 12); insert into registration values (8, 13); insert into registration values (7, 14); insert into registration values (6, 15); insert into registration values (5, 17); insert into registration values (4, 18); insert into registration values (3, 19); insert into registration values (2, 20); insert into registration values (1, 21); insert into registration values (2, 22); insert into registration values (3, 23); insert into registration values (4, 24); insert into registration values (5, 25); Insert into registration values (6, 24); insert into registration values (7, 23); insert into registration values (8, 22); insert into registration values (9, 21); insert into registration values (10, 20); insert into registration values (9, 19); insert into registration values (8, 17); Create Table courseInstructor( FacultyID Number(10), SectionID Number(10), Constraint CourseInstructor_pk Primary key (FacultyId, SectionID)); insert into courseInstructor values (1, 1); insert into courseInstructor values (2, 2); insert into courseInstructor values (3, 3); insert into courseInstructor values (4, 4); insert into courseInstructor values (5, 5); insert into courseInstructor values (5, 6); insert into courseInstructor values (4, 7); insert into courseInstructor values (3, 8); insert into courseInstructor values (2, 9); insert into courseInstructor values (1, 10); insert into courseInstructor values (5, 11); insert into courseInstructor values (4, 12); insert into courseInstructor values (3, 13); insert into courseInstructor values (2, 14); insert into courseInstructor values (1, 15); Create table grade( StudentID Number(10), SectionID Number(10), Grade Varchar2(1), Constraint grade_pk Primary key (StudentID, SectionID)); CREATE OR REPLACE TRIGGER TR_CreateGrade AFTER INSERT ON Registration FOR EACH ROW BEGIN INSERT INTO grade (SectionID,StudentID,Grade) VALUES(:New.SectionID,:New.StudentID,NULL); END TR_createGrade; / CREATE OR REPLACE FORCE VIEW V_reg_student_course AS SELECT Registration.StudentID, student.LastName, student.FirstName, course.CourseName, Registration.SectionID, course.CreditHours, section.Days, TO_CHAR(StartTime, 'MM/DD/YYYY') AS StartDate, TO_CHAR(StartTime, 'HH:MI PM') AS StartTime, TO_CHAR(EndTime, 'MM/DD/YYYY') AS EndDate, TO_CHAR(EndTime, 'HH:MI PM') AS EndTime, location.Building, location.Room FROM registration, student, section, course, location WHERE registration.StudentID = student.StudentID AND registration.SectionID = section.SectionID AND section.LocationID = location.LocationID AND section.CourseID = course.CourseID; CREATE OR REPLACE FORCE VIEW V_teacher_to_course AS SELECT courseInstructor.FacultyID, faculty.FirstName, faculty.LastName, courseInstructor.SectionID, section.Days, TO_CHAR(StartTime, 'MM/DD/YYYY') AS StartDate, TO_CHAR(StartTime, 'HH:MI PM') AS StartTime, TO_CHAR(EndTime, 'MM/DD/YYYY') AS EndDate, TO_CHAR(EndTime, 'HH:MI PM') AS EndTime, location.Building, location.Room FROM courseInstructor, faculty, section, course, location WHERE courseInstructor.FacultyID = faculty.FacultyID AND courseInstructor.SectionID = section.SectionID AND section.LocationID = location.LocationID AND section.CourseID = course.CourseID; SELECT * FROM V_reg_student_course; SELECT * FROM V_teacher_to_course;

    Read the article

  • C#/.NET Little Wonders: The Concurrent Collections (1 of 3)

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In the next few weeks, we will discuss the concurrent collections and how they have changed the face of concurrent programming. This week’s post will begin with a general introduction and discuss the ConcurrentStack<T> and ConcurrentQueue<T>.  Then in the following post we’ll discuss the ConcurrentDictionary<T> and ConcurrentBag<T>.  Finally, we shall close on the third post with a discussion of the BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. A brief history of collections In the beginning was the .NET 1.0 Framework.  And out of this framework emerged the System.Collections namespace, and it was good.  It contained all the basic things a growing programming language needs like the ArrayList and Hashtable collections.  The main problem, of course, with these original collections is that they held items of type object which means you had to be disciplined enough to use them correctly or you could end up with runtime errors if you got an object of a type you weren't expecting. Then came .NET 2.0 and generics and our world changed forever!  With generics the C# language finally got an equivalent of the very powerful C++ templates.  As such, the System.Collections.Generic was born and we got type-safe versions of all are favorite collections.  The List<T> succeeded the ArrayList and the Dictionary<TKey,TValue> succeeded the Hashtable and so on.  The new versions of the library were not only safer because they checked types at compile-time, in many cases they were more performant as well.  So much so that it's Microsoft's recommendation that the System.Collections original collections only be used for backwards compatibility. So we as developers came to know and love the generic collections and took them into our hearts and embraced them.  The problem is, thread safety in both the original collections and the generic collections can be problematic, for very different reasons. Now, if you are only doing single-threaded development you may not care – after all, no locking is required.  Even if you do have multiple threads, if a collection is “load-once, read-many” you don’t need to do anything to protect that container from multi-threaded access, as illustrated below: 1: public static class OrderTypeTranslator 2: { 3: // because this dictionary is loaded once before it is ever accessed, we don't need to synchronize 4: // multi-threaded read access 5: private static readonly Dictionary<string, char> _translator = new Dictionary<string, char> 6: { 7: {"New", 'N'}, 8: {"Update", 'U'}, 9: {"Cancel", 'X'} 10: }; 11:  12: // the only public interface into the dictionary is for reading, so inherently thread-safe 13: public static char? Translate(string orderType) 14: { 15: char charValue; 16: if (_translator.TryGetValue(orderType, out charValue)) 17: { 18: return charValue; 19: } 20:  21: return null; 22: } 23: } Unfortunately, most of our computer science problems cannot get by with just single-threaded applications or with multi-threading in a load-once manner.  Looking at  today's trends, it's clear to see that computers are not so much getting faster because of faster processor speeds -- we've nearly reached the limits we can push through with today's technologies -- but more because we're adding more cores to the boxes.  With this new hardware paradigm, it is even more important to use multi-threaded applications to take full advantage of parallel processing to achieve higher application speeds. So let's look at how to use collections in a thread-safe manner. Using historical collections in a concurrent fashion The early .NET collections (System.Collections) had a Synchronized() static method that could be used to wrap the early collections to make them completely thread-safe.  This paradigm was dropped in the generic collections (System.Collections.Generic) because having a synchronized wrapper resulted in atomic locks for all operations, which could prove overkill in many multithreading situations.  Thus the paradigm shifted to having the user of the collection specify their own locking, usually with an external object: 1: public class OrderAggregator 2: { 3: private static readonly Dictionary<string, List<Order>> _orders = new Dictionary<string, List<Order>>(); 4: private static readonly _orderLock = new object(); 5:  6: public void Add(string accountNumber, Order newOrder) 7: { 8: List<Order> ordersForAccount; 9:  10: // a complex operation like this should all be protected 11: lock (_orderLock) 12: { 13: if (!_orders.TryGetValue(accountNumber, out ordersForAccount)) 14: { 15: _orders.Add(accountNumber, ordersForAccount = new List<Order>()); 16: } 17:  18: ordersForAccount.Add(newOrder); 19: } 20: } 21: } Notice how we’re performing several operations on the dictionary under one lock.  With the Synchronized() static methods of the early collections, you wouldn’t be able to specify this level of locking (a more macro-level).  So in the generic collections, it was decided that if a user needed synchronization, they could implement their own locking scheme instead so that they could provide synchronization as needed. The need for better concurrent access to collections Here’s the problem: it’s relatively easy to write a collection that locks itself down completely for access, but anything more complex than that can be difficult and error-prone to write, and much less to make it perform efficiently!  For example, what if you have a Dictionary that has frequent reads but in-frequent updates?  Do you want to lock down the entire Dictionary for every access?  This would be overkill and would prevent concurrent reads.  In such cases you could use something like a ReaderWriterLockSlim which allows for multiple readers in a lock, and then once a writer grabs the lock it blocks all further readers until the writer is done (in a nutshell).  This is all very complex stuff to consider. Fortunately, this is where the Concurrent Collections come in.  The Parallel Computing Platform team at Microsoft went through great pains to determine how to make a set of concurrent collections that would have the best performance characteristics for general case multi-threaded use. Now, as in all things involving threading, you should always make sure you evaluate all your container options based on the particular usage scenario and the degree of parallelism you wish to acheive. This article should not be taken to understand that these collections are always supperior to the generic collections. Each fills a particular need for a particular situation. Understanding what each container is optimized for is key to the success of your application whether it be single-threaded or multi-threaded. General points to consider with the concurrent collections The MSDN points out that the concurrent collections all support the ICollection interface. However, since the collections are already synchronized, the IsSynchronized property always returns false, and SyncRoot always returns null.  Thus you should not attempt to use these properties for synchronization purposes. Note that since the concurrent collections also may have different operations than the traditional data structures you may be used to.  Now you may ask why they did this, but it was done out of necessity to keep operations safe and atomic.  For example, in order to do a Pop() on a stack you have to know the stack is non-empty, but between the time you check the stack’s IsEmpty property and then do the Pop() another thread may have come in and made the stack empty!  This is why some of the traditional operations have been changed to make them safe for concurrent use. In addition, some properties and methods in the concurrent collections achieve concurrency by creating a snapshot of the collection, which means that some operations that were traditionally O(1) may now be O(n) in the concurrent models.  I’ll try to point these out as we talk about each collection so you can be aware of any potential performance impacts.  Finally, all the concurrent containers are safe for enumeration even while being modified, but some of the containers support this in different ways (snapshot vs. dirty iteration).  Once again I’ll highlight how thread-safe enumeration works for each collection. ConcurrentStack<T>: The thread-safe LIFO container The ConcurrentStack<T> is the thread-safe counterpart to the System.Collections.Generic.Stack<T>, which as you may remember is your standard last-in-first-out container.  If you think of algorithms that favor stack usage (for example, depth-first searches of graphs and trees) then you can see how using a thread-safe stack would be of benefit. The ConcurrentStack<T> achieves thread-safe access by using System.Threading.Interlocked operations.  This means that the multi-threaded access to the stack requires no traditional locking and is very, very fast! For the most part, the ConcurrentStack<T> behaves like it’s Stack<T> counterpart with a few differences: Pop() was removed in favor of TryPop() Returns true if an item existed and was popped and false if empty. PushRange() and TryPopRange() were added Allows you to push multiple items and pop multiple items atomically. Count takes a snapshot of the stack and then counts the items. This means it is a O(n) operation, if you just want to check for an empty stack, call IsEmpty instead which is O(1). ToArray() and GetEnumerator() both also take snapshots. This means that iteration over a stack will give you a static view at the time of the call and will not reflect updates. Pushing on a ConcurrentStack<T> works just like you’d expect except for the aforementioned PushRange() method that was added to allow you to push a range of items concurrently. 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: // but you can also push multiple items in one atomic operation (no interleaves) 7: stack.PushRange(new [] { "Second", "Third", "Fourth" }); For looking at the top item of the stack (without removing it) the Peek() method has been removed in favor of a TryPeek().  This is because in order to do a peek the stack must be non-empty, but between the time you check for empty and the time you execute the peek the stack contents may have changed.  Thus the TryPeek() was created to be an atomic check for empty, and then peek if not empty: 1: // to look at top item of stack without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (stack.TryPeek(out item)) 5: { 6: Console.WriteLine("Top item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Stack was empty."); 11: } Finally, to remove items from the stack, we have the TryPop() for single, and TryPopRange() for multiple items.  Just like the TryPeek(), these operations replace Pop() since we need to ensure atomically that the stack is non-empty before we pop from it: 1: // to remove items, use TryPop or TryPopRange to get multiple items atomically (no interleaves) 2: if (stack.TryPop(out item)) 3: { 4: Console.WriteLine("Popped " + item); 5: } 6:  7: // TryPopRange will only pop up to the number of spaces in the array, the actual number popped is returned. 8: var poppedItems = new string[2]; 9: int numPopped = stack.TryPopRange(poppedItems); 10:  11: foreach (var theItem in poppedItems.Take(numPopped)) 12: { 13: Console.WriteLine("Popped " + theItem); 14: } Finally, note that as stated before, GetEnumerator() and ToArray() gets a snapshot of the data at the time of the call.  That means if you are enumerating the stack you will get a snapshot of the stack at the time of the call.  This is illustrated below: 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: var results = stack.GetEnumerator(); 7:  8: // but you can also push multiple items in one atomic operation (no interleaves) 9: stack.PushRange(new [] { "Second", "Third", "Fourth" }); 10:  11: while(results.MoveNext()) 12: { 13: Console.WriteLine("Stack only has: " + results.Current); 14: } The only item that will be printed out in the above code is "First" because the snapshot was taken before the other items were added. This may sound like an issue, but it’s really for safety and is more correct.  You don’t want to enumerate a stack and have half a view of the stack before an update and half a view of the stack after an update, after all.  In addition, note that this is still thread-safe, whereas iterating through a non-concurrent collection while updating it in the old collections would cause an exception. ConcurrentQueue<T>: The thread-safe FIFO container The ConcurrentQueue<T> is the thread-safe counterpart of the System.Collections.Generic.Queue<T> class.  The concurrent queue uses an underlying list of small arrays and lock-free System.Threading.Interlocked operations on the head and tail arrays.  Once again, this allows us to do thread-safe operations without the need for heavy locks! The ConcurrentQueue<T> (like the ConcurrentStack<T>) has some departures from the non-concurrent counterpart.  Most notably: Dequeue() was removed in favor of TryDequeue(). Returns true if an item existed and was dequeued and false if empty. Count does not take a snapshot It subtracts the head and tail index to get the count.  This results overall in a O(1) complexity which is quite good.  It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. ToArray() and GetEnumerator() both take snapshots. This means that iteration over a queue will give you a static view at the time of the call and will not reflect updates. The Enqueue() method on the ConcurrentQueue<T> works much the same as the generic Queue<T>: 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5: queue.Enqueue("Second"); 6: queue.Enqueue("Third"); For front item access, the TryPeek() method must be used to attempt to see the first item if the queue.  There is no Peek() method since, as you’ll remember, we can only peek on a non-empty queue, so we must have an atomic TryPeek() that checks for empty and then returns the first item if the queue is non-empty. 1: // to look at first item in queue without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (queue.TryPeek(out item)) 5: { 6: Console.WriteLine("First item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Queue was empty."); 11: } Then, to remove items you use TryDequeue().  Once again this is for the same reason we have TryPeek() and not Peek(): 1: // to remove items, use TryDequeue. If queue is empty returns false. 2: if (queue.TryDequeue(out item)) 3: { 4: Console.WriteLine("Dequeued first item " + item); 5: } Just like the concurrent stack, the ConcurrentQueue<T> takes a snapshot when you call ToArray() or GetEnumerator() which means that subsequent updates to the queue will not be seen when you iterate over the results.  Thus once again the code below will only show the first item, since the other items were added after the snapshot. 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5:  6: var iterator = queue.GetEnumerator(); 7:  8: queue.Enqueue("Second"); 9: queue.Enqueue("Third"); 10:  11: // only shows First 12: while (iterator.MoveNext()) 13: { 14: Console.WriteLine("Dequeued item " + iterator.Current); 15: } Using collections concurrently You’ll notice in the examples above I stuck to using single-threaded examples so as to make them deterministic and the results obvious.  Of course, if we used these collections in a truly multi-threaded way the results would be less deterministic, but would still be thread-safe and with no locking on your part required! For example, say you have an order processor that takes an IEnumerable<Order> and handles each other in a multi-threaded fashion, then groups the responses together in a concurrent collection for aggregation.  This can be done easily with the TPL’s Parallel.ForEach(): 1: public static IEnumerable<OrderResult> ProcessOrders(IEnumerable<Order> orderList) 2: { 3: var proxy = new OrderProxy(); 4: var results = new ConcurrentQueue<OrderResult>(); 5:  6: // notice that we can process all these in parallel and put the results 7: // into our concurrent collection without needing any external locking! 8: Parallel.ForEach(orderList, 9: order => 10: { 11: var result = proxy.PlaceOrder(order); 12:  13: results.Enqueue(result); 14: }); 15:  16: return results; 17: } Summary Obviously, if you do not need multi-threaded safety, you don’t need to use these collections, but when you do need multi-threaded collections these are just the ticket! The plethora of features (I always think of the movie The Three Amigos when I say plethora) built into these containers and the amazing way they acheive thread-safe access in an efficient manner is wonderful to behold. Stay tuned next week where we’ll continue our discussion with the ConcurrentBag<T> and the ConcurrentDictionary<TKey,TValue>. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here.   Tweet Technorati Tags: C#,.NET,Concurrent Collections,Collections,Multi-Threading,Little Wonders,BlackRabbitCoder,James Michael Hare

    Read the article

  • The importance of Design Patterns with Javascript, NodeJs et al

    - by Lewis
    With Javascript appearing to be the ubiquitous programming language of the web over the next few years, new frameworks popping up every five minutes and event driven programming taking a lead both server and client side: Do you as a Javascript developer consider the traditional Design Patterns as important or less important than they have been with other languages / environments?. Please name the top three design patterns you, as a Javascript developer use regularly and give an example of how they have helped in your Javascript development.

    Read the article

  • prerequisites of learnig hadoop, can php developer learn hadoop without java experience [closed]

    - by Rishabh Mathur
    i am willing to learn hadoop as a Developer , but i am confused over the prerequisite of learning it.? is having a good experience in java programming very essential to learn hadoop? I have 4 years of experience in application development in LAMP. But i am not in touch with java programming as a part of my regular work.My objective to get into hadoop is to increase my knowledge in bigdata analysis as well as to get an oppurtunity in this domain. Any suggestions?

    Read the article

  • SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28

    - by pinaldave
    CXPACKET has to be most popular one of all wait stats. I have commonly seen this wait stat as one of the top 5 wait stats in most of the systems with more than one CPU. Books On-Line: Occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if contention on this wait type becomes a problem. CXPACKET Explanation: When a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. There is an organizer/coordinator thread (thread 0), which takes waits for all the threads to complete and gathers result together to present on the client’s side. The organizer thread has to wait for the all the threads to finish before it can move ahead. The Wait by this organizer thread for slow threads to complete is called CXPACKET wait. Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query. Reducing CXPACKET wait: We cannot discuss about reducing the CXPACKET wait without talking about the server workload type. OLTP: On Pure OLTP system, where the transactions are smaller and queries are not long but very quick usually, set the “Maximum Degree of Parallelism” to 1 (one). This way it makes sure that the query never goes for parallelism and does not incur more engine overhead. EXEC sys.sp_configure N'cost threshold for parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Data-warehousing / Reporting server: As queries will be running for long time, it is advised to set the “Maximum Degree of Parallelism” to 0 (zero). This way most of the queries will utilize the parallel processor, and long running queries get a boost in their performance due to multiple processors. EXEC sys.sp_configure N'cost threshold for parallelism', N'0' GO RECONFIGURE WITH OVERRIDE GO Mixed System (OLTP & OLAP): Here is the challenge. The right balance has to be found. I have taken a very simple approach. I set the “Maximum Degree of Parallelism” to 2, which means the query still uses parallelism but only on 2 CPUs. However, I keep the “Cost Threshold for Parallelism” very high. This way, not all the queries will qualify for parallelism but only the query with higher cost will go for parallelism. I have found this to work best for a system that has OLTP queries and also where the reporting server is set up. Here, I am setting ‘Cost Threshold for Parallelism’ to 25 values (which is just for illustration); you can choose any value, and you can find it out by experimenting with the system only. In the following script, I am setting the ‘Max Degree of Parallelism’ to 2, which indicates that the query that will have a higher cost (here, more than 25) will qualify for parallel query to run on 2 CPUs. This implies that regardless of the number of CPUs, the query will select any two CPUs to execute itself. EXEC sys.sp_configure N'cost threshold for parallelism', N'25' GO EXEC sys.sp_configure N'max degree of parallelism', N'2' GO RECONFIGURE WITH OVERRIDE GO Read all the post in the Wait Types and Queue series. Additionally a must read comment of Jonathan Kehayias. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest you all to read the online book for further clarification. All the discussion of Wait Stats over here is generic and it varies from system to system. It is recommended that you test this on the development server before implementing on the production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

    Read the article

  • Ruby freelancing: realistic expectations?

    - by Sophie
    Hi guys, I'm in a situation where I only need $100 to live at a place. How is this relevant to programming? Well, I would like to hear the opinions of those on this site if it is at all realistic to expect a Ruby noobie to be able to make $100 freelancing by a month from now, assuming a great deal of effort and enthusiasm o_O I'm a complete noob to programming ;d, learning Ruby before Rails. (I also asked this on StackOverflow, but want lots of answers so .<)

    Read the article

  • @CodeStock 2012 Review: Rob Gillen ( @argodev ) - Anatomy of a Buffer Overflow Attack

    Anatomy of a Buffer Overflow AttackSpeaker: Rob GillenTwitter: @argodevBlog: rob.gillenfamily.net Honestly, this talk was over my head due to my lack of knowledge of low level programming, and I think that most of the other attendees would agree. However I did get the basic concepts that we was trying to get across. Fortunately most high level programming languages handle most of the low level concerns regarding preventing buffer overflow attacks. What I got from this talk was to validate all input data from external sources.

    Read the article

  • Ubuntu for Android on the ASUS Transformer Prime

    - by sola
    I would like to use Ubuntu on my Transformer Prime in parallel with Android (not as a dual booting solution, I want to be able to switch between them instantaniously). I am aware of the traditional chrooting/VNC solution but I heard that it performs very poorly so I would like to use Ubuntu For Android (UFA) which has been announced recently by Canonical. That looks like a polished, highly integrated solution for Android devices. The Prime would be the ideal device for Ubuntu For Android since it has a powerful processor (Tegra3) capable of running a lot of processes in parallel on its 4 cores. Does anyone know if Canonical or anybody else is working on supporting UFA on the ASUS Transformer Prime? As far as I understand, the X11 driver is available for Tegra3 so, the biggest hurdle may be easily overcome.

    Read the article

  • How to Write an E-Book

    A few days ago my attention was drawn to a tweet spat between Karl Seguin and Scott Hanselman around the relaunch of ASP.NET and the title element in HTML. Tempest in a teapot of course, but worthwhile as I did some googling on Karl and found his blog at codebetter.com. From there it was a short jump to his free e-book, The Foundations of Programming. This short book is distinguished by its orientation, opinionated, its tone, mentoring and its honesty, which is refreshing. In Foundations, Karl covers what he considers the basics of programming and good design, including test driven development, dependency injection and domain driven design. Karl is opinionated, as the topics suggest, and doesnt bother to pretend that he doesnt think what hes suggesting is the better way, not just another way. He is aligned with ALT.NET, and gives an excellent overview of what that means; an overview more enlightening than the ALT.NET site. ALT.NET has its critics, but presenting a strong opinion grabbed my attention as a reader. It is a short walk from opinionated to hectoring,  but Karl held my attention without insulting me. He takes the time to explain, with examples, from the ground up, the problems that test driven development and dependency injection solve. So for dependency injection he builds it up from no DI, to a hand crafted approach, to a full fledged DI framework. This approach is more persuasive than just proscriptive and engaged me as the reader to follow along with his train of thought. Foundations is not as pedantic as I am making it sound. The final ingredient in Karls mix is honesty. He acknowledges that sometimes unit testing does cost more up front and take more time. He admits that sometimes he designs something a certain way just to be testable. He also warns that focusing too much on DI and loose coupling can lead to the poor design you are trying to avoid. These points add depth to his argument as I could tell hes speaking from experience, with some hard won lessons. I enjoyed The Foundations of Programming. When I was done with it, I was amazed how much I got a lot out of its 80 some pages. It is a rarity to come across something worthwhile that is longer then a tweet, but shorter than a tome these days. Well done Karl.   -- Relevant Links -- The now titled and newly relaunched page in question: http://www.asp.net/ The pleasantly confusing ALT.NET homepage: http://altdotnet.org/ A longer review, with details, chapter listings and all that important stuff: http://accidentaltechnologist.com/book-reviews/book-review-foundations-of-programming-by-karl-seguin/Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

    Read the article

  • Slow Chat with Industry Experts: Developing Multithreaded Applications

    Sponsored by Intel Join the experts who created The Intel Guide for Developing Multithreaded Applications for a slow chat about multithreaded application development. Bring your questions about application threading, memory management, synchronization, programming tools and more and get answers from the parallel programming experts. Post your questions here

    Read the article

  • Slow Chat with Industry Experts: Developing Multithreaded Applications

    Sponsored by Intel Join the experts who created The Intel Guide for Developing Multithreaded Applications for a slow chat about multithreaded application development. Bring your questions about application threading, memory management, synchronization, programming tools and more and get answers from the parallel programming experts. Post your questions here

    Read the article

  • Identifying languages used by particular industries

    - by user66146
    I am new to programming and I don't know the differences between the major languages. I desperately want to get into the gaming industry because I have so many stories I want to tell and so many experiences I want to create. I currently do 3D modeling/animation, so any similarities would be helpful. What steps should I take to investigate an industry (gaming) and the companies within that industry? How do I identify what programming languages they use, so I can study them?

    Read the article

  • What development terms come from the construction industry?

    - by Renesis
    When talking with colleagues about software design and development principles, I've noticed one of the most common sources for analogies is the construction industry. It would be quite useful to have a list of what programming/development terms and concepts are borrowed from construction industry? (And please provide a description or experiences regarding that topic.) [Credit to Programming concepts taken from the arts and humanities for the idea]

    Read the article

  • Learning content for MCSDs: Web Applications and Windows Store Apps using HTML5

    Recently, I started again to learn for various Microsoft certifications. First candidate on my way to MSCD: Web Applications is the Exam 70-480: Programming in HTML5 with JavaScript and CSS3. Motivation to go for a Microsoft exam I guess, this is quite personal but let me briefly describe my intentions to go that exam. First, I'm doing web development since the 1990's. Working with HTML, CSS and Javascript is happening almost daily in my workspace. And honestly, I do not only do 'pure' web development but already integrated several HTML/CSS/Javascript frontend UIs into an existing desktop application (written in Visual FoxPro) inclusive two-way communication and data exchange. Hm, might be an interesting topic for another blog article here... Second, this exam has a very interesting aspect which is listed at the bottom of the exam's details: Credit Toward Certification When you pass Exam 70-480: Programming in HTML5 with JavaScript and CSS3, you complete the requirements for the following certification(s): Programming in HTML5 with JavaScript and CSS3 Specialist Exam 70-480: Programming in HTML5 with JavaScript and CSS3: counts as credit toward the following certification(s): MCSD: Web Applications MCSD: Windows Store Apps using HTML5 So, passing one single exam will earn you specialist certification straight-forward, and opens the path to higher levels of certifications. Preparations and learning path Well, due to a newsletter from Microsoft Learning (MSL) I caught interest in picking up the circumstances and learning materials for this particular exam. As of writing this article there is a promotional / voucher code available which enables you to register for this exam for free! Simply register yourself with or log into your existing account at Prometric, choose the exam for a testing facility near to you and enter the voucher code HTMLJMP (available through 31.03.2013 or while supplies last). Hurry up, there are restrictions... As stated above, I'm already very familiar with web development and the programming flavours involved into this. But of course, it is always good to freshen up your knowledge and reflect on yourself. Microsoft is putting a lot of effort to attract any kind of developers into the 'App Development'. Whether it is for the Windows 8 Store or the Windows Phone 8 Store, doesn't really matter. They simply need more apps. This demand for skilled developers also comes with a nice side-effect: Lots and lots of material to study. During the first couple of hours, I could easily gather high quality preparation material - again for free! Following is just a small list of starting points. If you have more resources, please drop me a message in the comment section, and I'll be glad to update this article accordingly. Developing HTML5 Apps Jump Start This is an accelerated jump start video course on development of HTML5 Apps for Windows 8. There are six modules that are split into two video sessions per module. Very informative and intense course material. This is packed stuff taken from an official preparation course for exam 70-480. Developing Windows Store Apps with HTML5 Jump Start Again, an accelerated preparation video course on Windows 8 Apps. There are six modules with two video sessions each which will catapult you to your exam. This is also related to preps for exam 70-481. Programming Windows 8 Apps with HTML, CSS, and JavaScript Kraig Brockschmidt delves into the ups and downs of Windows 8 App development over 800+ pages. Great eBook to read, study, and to practice the samples - best of all, it's for free. codeSHOW() This is a Windows 8 HTML/JS project with the express goal of demonstrating simple development concepts for the Windows 8 platform. Code, code and more code... absolutely great stuff to study and practice. Microsoft Virtual Academy I already wrote about the MVA in a previous article. Well, if you haven't registered yourself yet, now is the time. The list is not complete for sure, but this might keep you busy for at least one or even two weeks to go through the material. Please don't hesitate to add more resources in the comment section. Right now, I'm already through all videos once, and digging my way through chapter 4 of Kraig's book. Additional material - Pluralsight Apart from those free online resources, I also following some courses from the excellent library of Pluralsight. They already have their own section for Windows 8 development, but of course, you get companion material about HTML5, CSS and Javascript in other sections, too. Introduction to Building Windows 8 Applications Building Windows 8 Applications with JavaScript and HTML Selling Windows 8 Apps HTML5 Fundamentals Using HTML5 and CSS3 HTML5 Advanced Topics CSS3 etc... Interesting to see that Michael Palermo provides his course material on multiple platforms. Fantastic! You might also pay a visit to his personal blog. Hm, it just came to my mind that Aaron Skonnard of Pluralsight publishes so-called '24 hours Learning Paths' based on courses available in the course library. Would be interested to see a combination for Windows 8 App development using HTML5, CSS3 and Javascript in the future. Recommended workspace environment Well, you might have guessed it but this requires Windows 8, Visual Studio 2012 Express or another flavour, and a valid Developers License. Due to an MSDN subscription I working on VS 2012 Premium with some additional tools by Telerik. Honestly, the fastest way to get you up and running for Windows 8 App development is the source code archive of codeSHOW(). It does not only give you all source code in general but contains a couple of SDKs like Bing Maps, Microsoft Advertising, Live ID, and Telerik Windows 8 controls... for free! Hint: Get the Windows Phone 8 SDK as well. Don't worry, while you are studying the material for Windows 8 you will be able to leverage from this knowledge to development for the phone platform, too. It takes roughly one to two hours to get your workspace and learning environment, at least this was my time frame due to slow internet connection and an aged spare machine. ;-) Oh, before I forget to mention it, as soon as you're done, go quickly to the Windows Store and search for ClassBrowserPlus. You might not need it ad hoc for your development using HTML5, CSS and Javascript but I think that it is a great developer's utility that enables you to view the properties, methods and events (along with help text) for all Windows 8 classes. It's always good to look behind the scenes and to explore how it is made. Idea: Start/join a learning group The way you learn new things or intensify your knowledge in a certain technology is completely up to your personal preference. Back in my days at the university, we used to meet once or twice a week in a small quiet room to exchange our progress, questions and problems we ran into. In general, I recommend to any software craftsman to lift your butt and get out to exchange with other developers. Personally, I like this approach, as it gives you new points of view and an insight into others' own experience with certain techniques and how they managed to solve tricky issues. Just keep it relaxed and not too formal after all, and you might a have a good time away from your dull office desk. Give your machine a break, too.

    Read the article

  • Low latency technologies for c++, c# and java?

    - by James
    I've been reading job descriptions and many mention 'low latency'. However, I wondered if someone could clarify what type of technologies this would refer to? One of the adverts mentioned 'ACE' which I googled to find out was some CISCO telephony technology. If you were hiring someone for a low latency role, what would you use as a checklist for ensuring they knew about low latency programming? I'm using this to learn more about low latency programming myself.

    Read the article

  • Too Few Women in IT!

    - by Yolande
    Last year, only 1% of attendees at Devoxx were women . This year, Devoxx addressed the issue in a panel entitled "Why We Should Target Women." On the panel were Kim Ross, Régina ten Bruggencate, Trisha Gee, Antonio Goncalves and Claude Falguiére. The moderator was Martijn Verburg. The discussion focused on how to attract women to programming and how to get current women programmers to be more active in the community. The panelists agreed that the IT field should not just attract more women but also men of different ethnic backgrounds. The lack of women in programming is in part a cultural issue that differs from region to region. In developed countries, very few women work as programmers whereas in Brazil and India a lot of women pursue careers in IT.  Women in developed countries perceive the field as isolating and very few young women graduate in computer science.  This perception of isolation was based in reality decades ago, but that is no longer the case today. Main ideas discussed by the panel: - Parents should encourage their daughters to play with Lego and learn programming - More organizations should target girls in high schools and young women in university to expose them to programming.  Duchess organization is planning on being more involved with young girl events and mentoring. - Women tend to be more self-critical about their skills and are intimidated by high skill requirements in job advertisements. Companies should change job advertisements to get more women to interviews. - Panelists don't recommend affirmative action because women feel favored and lose credibility. They want to be judged for their skills. - Panelists recommend acting the same way when dealing with either female or male co-workers and managers - Women need mentors (men or women) to learn to become speakers at conferences and to promote themselves better - Men should be sensitive to the fact that women are alone at work to respond to men teasing. The balance of power at work is different from a social setting. - Men also experience discrimination on the job. It is more difficult for men to take time off when their children are sick, for example. Equal valuing of parental obligations could result in equal pay for women. See also: Trisha Gee Blog - http://mechanitis.blogspot.com/ Duchess Organization - http://www.jduchess.org/

    Read the article

  • Best Books of C

    - by Patrick
    Hi, I realy want to get high skills in C programming and I know that the best and only way is hard work and lots of practice. though I found so many tutorials and books available on the net about learning the C language. I'm just looking for one or two good books in C that I can learn from and get high skills in C. Anyone knows such a great book/books for C programming pls? (sorry for replication if the question exists already in the forum) Regards!

    Read the article

  • Is an undergraduate degree in CS required?

    - by Girish
    I will complete my undergrad in Material Science this spring. I am not interested in the subject but I am very interested in Computer Science and programming and have decided to make the shift. Do you think I should first get an undergraduate degree in Computer Science or should I apply for a master's program? My programming skills are pretty decent, but I lack a lot of concrete knowledge in algorithms and data structures? Will a master's degree help me with the basics?

    Read the article

  • PPL and TPL sessions on channel9

    - by Daniel Moth
    Back in June there was an internal conference in Redmond ("Engineering Forum") aimed at Microsoft engineers, and delivered by Microsoft engineers. I was asked to put together a track on Multi-Core development, so I picked 6 parallelism experts and we created 6 awesome sessions (we won the top spot in the Top 10 :-)). Two of the speakers kept the content fairly external-friendly, so we received permission to publish their recordings publicly. Enjoy (best to download the High Quality WMV): Don McCrady - Parallelism in C++ Using the Concurrency Runtime Stephen Toub - Implementing Parallel Patterns using .NET 4 To get notified on future videos on parallelism (or to browse the archive) stay tuned on this channel9 parallel computing feed. Comments about this post welcome at the original blog.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 239 240 241 242 243 244 245 246 247 248 249 250  | Next Page >