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  • Manic Monday - More OpenWorld Solaris Sessions: Developers, Cloud, Customer Insights, Hardware Optimization

    - by Larry Wake
    We're overflowing with Monday sessions; literally more than one person can take in. Learn more about what's new in Oracle Solaris Studio, hear about the latest x86 and SPARC hardware optimizations, get some insights on cloud deployment strategies, and find out from your peers what they're doing with Oracle Solaris. If you're an OpenWorld attendee, go to to Schedule Builder to guarantee your space in any session or lab. See yesterday's blog post and the "Focus on Oracle Solaris" guide for even more sessions. Monday, October 1st: 10:45 AM - Maximizing Your SPARC T4 Oracle Solaris Application Performance(CON6382,  Marriott Marquis - Golden Gate C3) Hear how customers and commercial software partners have reached peak performance on SPARC T4 servers and engineered systems with Oracle Solaris Studio and its latest tools for analyzing, reporting, and improving runtime performance: Autoparallelizing, high-performance compilers Performance Analyzer (used to find performance hotspots) Thread Analyzer (to expose data races and deadlocks) Code Analyzer (used to discover latent memory corruption issues) 10:45 Cloud Formation: Implementing IaaS in Practice with Oracle Solaris(CON8787, Moscone South 302) Decisions, decisions--at the same time, we've got a session that covers why Oracle Solaris is the ideal OS for public or private clouds, IaaS or PaaS, with built-in features for elastic infrastructure, unrivaled security, superfast installation and deployment, nonstop availability, and crystal-clear observability. This session will include a customer study on how Oracle Solaris is used in the cloud today to implement the Oracle stack. 12:15 PM - Customer Insight: Oracle Solaris on Oracle Exadata, Oracle Exalogic, and SPARC SuperCluster(CON8760, Moscone South 270) Hear from customers what benefits they have realized from using the Oracle stack on Oracle Exadata and Oracle’s SPARC SuperCluster and from using Oracle Solaris on those engineered systems, taking advantage of built-in lightweight OS virtualization (Zones), enterprise reliability and scale, and other key features. 1:45 PM - Case Study: Mobile Tornado Uses Oracle Technology for Better RAS and TCO?(CON4281, Moscone West 2005) Mobile Tornado develops and markets instant communication platforms, replacing traditional radio networks with cellular networks. Its critical concern is uptime. Find out how they've used Oracle Solaris, Netra SPARC T4, and Oracle Solaris Cluster, including Oracle Solaris ZFS and Zones, for their Oracle Database deployments to improve reliability and drive down cost. 3:15 PM - Technical Panel: Developing High Performance Applications on Oracle Solaris(CON7196, Marriott Marquis - Golden Gate C2) Engineers from the Oracle Solaris, Oracle Database, and Oracle Tuxedo development teams, and Oracle ISV Engineering discuss how they develop high-performance enterprise applications that take advantage of Oracle's SPARC and x86 servers, with Oracle Solaris Studio and new Oracle Solaris 11 features. Topics will include developer tools, parallel frameworks, best practices, and methodologies, as well as insights and case studies on parallelizing and optimizing application performance on Oracle Solaris. Bring your best questions! 3:15 PM -  x86 Power Management with Oracle Solaris: Current State, Opportunities, and Future(CON6271, Moscone West 2012) Another option for this time slot: learn about how Intel Xeon and Oracle Solaris work together to reduce server power consumption. This presentation addresses some of the recent power management improvements in Oracle Solaris, opportunities to further improve energy efficiency, and some future directions for Oracle Solaris power management.

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  • Technologies stack to create soccer game vizualization on web page [on hold]

    - by Lambrusco
    I want to create soccer game vizualization. What technologies will be best to create such one for web page? On input I have two teams with players. I have theory about their movements, the movement of the ball on field and so on. I just want to vizualize their movements. What will be the best technology stack? I mean programming languages (C++, Ruby, Java, PHP) and vizualization ways (Flash, HTML5, JS)

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  • How do I know what hardware to buy to meet my needs?

    - by Darth Android
    While Stack Exchange does not permit shopping recommendations, it doesn't provide any general advice to consider when buying hardware. So, instead of just telling those that ask what to buy that it's not allowed, let's tell them how to figure out what they need. When looking forward to build a computer, how do I know what to buy? How do I find out if a given CPU will be enough for a certain game or application that I want to run? How do I find out if a given graphics card will be enough for a certain game or application? What is important when looking at motherboards? How much memory do I need? How do I know how much wattage I need for a power supply? What size case do I need? What relevant standards do I need to read up on and be aware of? PCI, PCIe, SATA, USB 2.0, USB 3.0, etc... What "gotchas" do I need to be on the lookout for? Please keep responses generation-agnostic to ensure they will be helpful to our future users. :)

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  • Android: bug in launchMode="singleTask"? -> activity stack not preserved

    - by Stefan Klumpp
    My main activity A has as set android:launchMode="singleTask" in the manifest. Now, whenever I start another activity from there, e.g. B and press the HOME BUTTON on the phone to return to the home screen and then again go back to my app, either via pressing the app's button or pressing the HOME BUTTONlong to show my most recent apps it doesn't preserve my activity stack and returns straight to A instead of the expected activity B. Here the two behaviors: Expected: A > B > HOME > B Actual: A > B > HOME > A (bad!) Is there a setting I'm missing or is this a bug? If the latter, is there a workaround for this until the bug is fixed? FYI: This question has already been discussed here. However, it doesn't seem that there is any real solution to this, yet.

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  • why gcc 4.x default reserve 8 bytes for stack on linux when calling a method?

    - by nikcname
    as a beginner of asm, I am checking gcc -S generated asm code to learn. why gcc 4.x default reserve 8 bytes for stack when calling a method? func18 is the empty function with no return no param no local var defined. I can't figure out why 8 bytes is reserved here (neither any forum/site mention for the reason, ppl seems take it for granted) is it for the %ebp just push? or return type?! many thx! .globl _func18 _func18: pushl %ebp movl %esp, %ebp subl $8, %esp .text

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  • why gcc 4.x default reserve 8 bytes for stack on linux when calling a method?

    - by nikcname
    as a beginner of asm, I am checking gcc -S generated asm code to learn. why gcc 4.x default reserve 8 bytes for stack when calling a method? func18 is the empty function with no return no param no local var defined. I can't figure out why 8 bytes is reserved here (neither any forum/site mention for the reason, ppl seems take it for granted) is it for the %ebp just push? or return type?! many thx! .globl _func18 _func18: pushl %ebp movl %esp, %ebp subl $8, %esp .text

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  • Stack allocation fails and heap allocation succeeds!! Is it possible??

    - by Prabhu
    Hello All, I have the following piece of snippet Class Sample { Obj_Class1 o1; Obj_Class2 o2;}; But the size of Obj_Class1 and Obj_Class2 is huge so that the compiler shows a warning "Consider moving some space to heap". I was asked to replace Obj_Class1 o1 with Obj_Class1* o1 = new Obj_Class1(); But I feel that there is no use of making this change as heap allocation will also fail if stack allocation fails. Am I correct? Or does it make sense to make this change ( other than suppressing the compiler warning ).

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  • Using C++, why can `throw` cause `terminate()`, and when are the stack variables to be freed?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Does `throw` cause stack variables (full types) to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Does `throw` cause stack variables to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • PC power supply & normal range for voltages reported in BIOS hardware monitor?

    - by Chris W. Rea
    I'm trying to diagnose whether my computer has an ample power supply. Sometimes when I play a video-intensive game, both monitors lose the video signal, even though the computer remains on and sound playing. A theory I have is: the video card isn't getting sufficient power. I can't imagine it's overheating because the machine is well-ventilated and the video card isn't hot to touch when this happens. Anyway, in my PC's BIOS there's a Hardware Monitor page, and among other voltages reported (such as CPU, DRAM, South Bridge, etc.) I can see the following values: 3.3V 3.152V 5V 4.944V 12V 11.872V Are those the voltages used by peripherals? What voltage should I be referencing if I want to know what my video card (PCI Express) is consuming? What is the normal range of values reported for those? My values above appear to be under by approximately 4.5%, 1.1%, and 1.1% respectively. Is that cause for concern? How else should I be determining if my power supply is "right-sized" for my PC and video card, or am I perhaps barking up the wrong tree?

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  • Important hardware components to avoid bottlenecks/improve speed on a laptop?

    - by joelhaus
    Looking for a powerful general use (including web development) laptop running Windows. Price points seem to be all over the place. Many less powerful machines are priced much higher than machines with better specs. How does one navigate this market? Are there any unpublished/under-publicized specs/bottlenecks you look for? Understanding that hardware improves over time, is there an efficient ratio that can be used (or something similar, like Windows Experience Index?) which will indicate how powerful a system is? Thanks in advance! P.S. Here is an example from a laptop released on September 17, 2010. Can anyone pick apart these specs? Is there missing information you would be looking for? OS: Win 7 Display: 16.4" LED backlit Processor: Intel Core i7-740QM, 6MB L3 Cache RAM: 6GB DDR3 1333MHz (8GB max.) Graphics: NVIDIA GeForce GT 425M (1 GB of dedicated DDR3) HDD: 500GB 7200RPM SATA Hard Drive Removable Disc: Blue-ray with DVD±R/RW Misc: webcam/mic/speakers/bluetooth (via Sony Vaio VPC-F137FX/B)

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  • What hardware would I need (approx) to run ESXi server?

    - by mr.b
    Hi, I am considering to purchase off-the-shelf commodity hardware in order to build server that will host virtual machines using ESXi server. Intended purpose for this server is NOT mission critical tasks. It will have to run perhaps 20-50 Windows XP/Vista/7 virtual machines (in total, but closer to 20 figure). Each guest would have to have 1-2 GB of ram, and probably two-three times more disk space than guest OS needs with clean install and all updates applied (that would be around 6-8 GB for XP, and i believe closer to 10-15 for win7). Those guests will act as a test ground for a new product that is network management software, thus guests will idle most of their time once initially loaded, but if I give them some task to complete, they should be able to perform reasonably well. Now, from what I have learned... CPU is usually not much of an issue (6 cores would do it), memory should not be lacking, but doesn't have to be sum of all guests, because of overcommitment... That leads me to IO, which is, as it seems, the bottleneck. Since I have very little experience with ESXi (and ESX, too) server, I'd like to ask: How much memory could I save by overcommitment, and how does it affect performance? Is 6-core cpu enough to run above described system? Would it be possible to run entire server off two (or even one) SSD drives (to host system virtual disks, with few additional HDDs (2-3) in RAID 0 to be used as secondary storage? I read somewhere that ESXi allows having something like "master image", essentially virtual machine that is "deployed" many times, so that disk space can be saved by having only differences stored by specific guests, instead of copying around whole virtual disks. Is this true, and how can this help me? Are there any other things I need to take into consideration when building this off-the-shelf solution? I should probably mention here that I'm fully aware of issues like SPOF regarding power supply, raid 0, etc, but since it's only a testing ground and not a production system, it's not so important for me. Thanks, B.

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  • When buying hardware, what sites do you trust for information? [closed]

    - by Matt Dawdy
    I won't ask "what laptop should I buy" since the information is likely to change very quickly. However, I am about to buy a laptop, and I honestly don't know where to begin researching this based on my needs. I am hoping that asking about specific sites that do reviews/recommendations that this will still be on topic. I read the 6 guidelines for subjective questions and believe that this question scores favorably. I'm starting a new job in a few weeks, and they want to know what specific laptop to purchase. I'd like to get the most for their money and get a machine that will not need to be replaced in a year. When looking at a site like Dell, it's hard to get a full picture of the performance of a laptop. Does it work with a docking station, and if so, what kinds of video outs are on it? Will it work well when compiling several large projects in .Net? Has anyone had any issues with the machine getting flaky when dragging it from work to home and back all the time? etc. So, if people would enter in their preferred sites they use when researching hardware, and why they prefer that site (x is great for laptop comparisons, y is great for gaming machine reviews, etc) the I hope that this can be a question with valuable answers to others than just myself.

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  • 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

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  • Is anyone else using OpenBSD as a router in the enterprise? What hardware are you running it on?

    - by Kamil Kisiel
    We have an OpenBSD router at each of our locations, currently running on generic "homebrew" PC hardware in a 4U server case. Due to reliability concerns and space considerations we're looking at upgrading them to some proper server-grade hardware with support etc. These boxes serve as the routers, gateways, and firewalls at each site. At this point we're quite familiar with OpenBSD and Pf, so hesitant at moving away from the system to something else such as dedicated Cisco hardware. I'm currently thinking of moving the systems to some HP DL-series 1U machines (model yet to be determined). I'm curious to hear if other people use a setup like this in their business, or have migrated to or away from one.

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  • (When) Does hardware, especially the CPU(s), deliver wrong results?

    - by sub
    What I'm talking about is: Is it possible that under certain circumstances the CPU "buggs" and suddenly responses 1+1=2? In which parts of the computer can that happen (HDD, RAM, Mainboard)? What could be the causes? Bad quality? Overheating? Does that even happen? When yes, how frequently? If everything is okay with the CPU (not a single fault in production, good temperature), can that still happen sometimes? What would be the results of, let's say one to three wrong computations? This is programming related as it would be nice to know if you can even rely on the hardware to return the right results.

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  • When machine code is generated from a program how does it translates to hardware level operations ??

    - by user553492
    Like if say the instruction is something like 100010101 1010101 01010101 011101010101. Now how is this translating to an actual job of deleting something from memory? Memory consists of actual physical transistors the HOLD data. What causes them to lose that data is some external signal? I want to know how that signal is generated. Like how some binary numbers change the state of a physical transistor. Is there a level beyond machine code that isn't explicitly visible to a programmer? I have heard of microcode that handle code at hardware level, even below assembly language. But still I pretty much don't understand. Thanks!

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  • Software development stack 2012

    A couple of months ago, I posted on Google+ about my evaluation period for a new software development stack in general. "Analysing existing 'jungle' of multiple applications and tools in various languages for clarification and future design decisions. Great fun and lots of headaches... #DevelopersLife" Surprisingly, there was response... ;-) - And this series of articles is initiated by this post. Thanks Olaf. The past few years... Well, after all my first choice of software development in the past was Microsoft Visual FoxPro 6.0 - 9.0 in combination with Microsoft SQL Server 2000 - 2008 and Crystal Reports 9.x - XI. Honestly, it is my main working environment due to exisiting maintenance and support plans with my customers, but also for new project requests. And... hands on, it is still my first choice for data manipulation and migration options. But the earth is spinning, and as a software craftsman one has to be flexible with the choice of tools. In parallel to my knowledge and expertise in the above mentioned tools, I already started very early to get my hands dirty with the Microsoft .NET Framework. If I remember correctly, I started back in 2002/2003 with the first version ever. But this was more out of curiousity. During the years this kind of development got more serious and demanding, and I focused myself on interop and integrational libraries and applications. Mainly, to expose exisitng features of the .NET Framework to Visual FoxPro - I even had a session about that at the German Developer's Conference in Frankfurt. Observation of recent developments With the recent hype on Javascript and HTML5, especially for Windows 8 and Windows Phone 8 development, I had several 'Deja vu' events... Back in early 2006 (roughly) I had a conversation on the future of Web and Desktop development with my former colleagues Golo Roden and Thomas Wilting about the underestimation of Javascript and its root as a prototype-based, dynamic, full-featured programming language. During this talk with them I took the Mozilla applications, namely Firefox and Thunderbird, as a reference which are mainly based on XML, CSS, Javascript and images - besides the core rendering engine. And that it is very simple to write your own extensions for the Gecko rendering engine. Looking at the Windows Vista Sidebar widgets, just underlines this kind of usage. So, yes the 'Modern UI' of Windows 8 based on HTML5, CSS3 and Javascript didn't come as any surprise to me. Just allow me to ask why did it take so long for Microsoft to come up with this step? A new set of tools Ok, coming from web development in HTML 4, CSS and Javascript prior to Visual FoxPro, I am partly going back to that combination of technologies. What is the other part of the software development stack here at IOS Indian Ocean Software Ltd? Frankly, it is easy and straight forward to describe: Microsoft Visual FoxPro 9.0 SP 2 - still going strong! Visual Studio 2012 (C# on latest .NET Framework) MonoDevelop Telerik DevCraft Suite WPF ASP.NET MVC Windows 8 Kendo UI OpenAccess ORM Reporting JustCode CODE Framework by EPS Software MonoTouch and Mono for Android Subversion and additional tools for the daily routine: Notepad++, JustCode, SQL Compare, DiffMerge, VMware, etc. Following the principles of Clean Code Developer and the Agile Manifesto Actually, nothing special about this combination but rather a solid fundament to work with and create line of business applications for customers.Honestly, I am really interested in your choice of 'weapons' for software development, and hopefully there might be some nice conversations in the comment section. Over the next coming days/weeks I'm going to describe a little bit more in detail about the reasons for my decision. Articles will be added bit by bit here as reference, too. Please bear with me... Regards, JoKi

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  • XP Mode (Windows Virtual PC for Windows 7) no longer requires hardware virtualisation - hurrah !

    - by Liam Westley
    Windows Virtual PC (aka XP Mode) When XP Mode was released, it insisted on hardware virtualisation being present on your CPU and enabled in the BIOS.  Given that Windows Virtual PC was based on an improved Virtual PC 2007, which provided hardware virtualisation as a user selectable option, I did wonder why on earth Microsoft thought this was a good idea.  Not only do many people not have a CPU with hardware virtualisation support, some manufacturers don't provide a BIOS option to enable this setting, especially on laptops - yes Sony, Toshiba and Acer, I'm looking at you. Dumb and dumber This issue became a double whammy; not only was Microsoft a bit dumb on not supporting Windows Virtual PC without hardware virtualisation, your hardware manufacturer was also dumb in not supporting the option in the BIOS. Microsoft update to Windows Virtual PC Belatedly, Microsoft has seen the problem with this hardware virtualisation requirement and has now released a new version of Windows Virtual PC that works without hardware virtualisation.  This is really good news for those with older (or limited) CPUs and rubbish BIOS firmware. You can details of how to download the new versions of XP Mode here, http://blogs.msdn.com/virtual_pc_guy/archive/2010/03/18/windows-virtual-pc-no-hardware-virtualization-update-now-available-for-download.aspx And there is also an explanation of why the hardware virtualisation requirement was in place for previous releases, http://blogs.msdn.com/virtual_pc_guy/archive/2010/03/18/windows-virtual-pc-now-without-the-need-for-hardware-virtualization.aspx

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  • No database selected error in CodeIgniter running on MAMP stack

    - by Apophenia Overload
    First off, does anyone know of a good place to get help with CodeIgniter? The official community forums are somewhat disappointing in terms of getting many responses. I have ci installed on a regular MAMP stack, and I’m working on this tutorial. However, I have only gone through the Created section, and currently I am getting a No database selected error. Model: <?php class submit_model extends Model { function submitForm($school, $district) { $data = array( 'school' => $school, 'district' => $district ); $this->db->insert('your_stats', $data); } } View: <?php $this->load->helper('form'); ?> <?php echo form_open('main'); ?> <p> <?php echo form_input('school'); ?> </p> <p> <?php echo form_input('district'); ?> </p> <p> <?php echo form_submit('submit', 'Submit'); ?> </p> <?php echo form_close(); ?> Controller: <?php class Main extends controller { function index() { // Check if form is submitted if ($this->input->post('submit')) { $school = $this->input->xss_clean($this->input->post('school')); $district = $this->input->xss_clean($this->input->post('district')); $this->load->model('submit_model'); // Add the post $this->submit_model->submitForm($school, $district); } $this->load->view('main_view'); } } database.php $db['default']['hostname'] = "localhost:8889"; $db['default']['username'] = "root"; $db['default']['password'] = "root"; $db['default']['database'] = "stats_test"; $db['default']['dbdriver'] = "mysql"; $db['default']['dbprefix'] = ""; $db['default']['pconnect'] = TRUE; $db['default']['db_debug'] = TRUE; $db['default']['cache_on'] = FALSE; $db['default']['cachedir'] = ""; $db['default']['char_set'] = "utf8"; $db['default']['dbcollat'] = "utf8_general_ci"; config.php $config['base_url'] = "http://localhost:8888/ci/"; ... $config['index_page'] = "index.php"; ... $config['uri_protocol'] = "AUTO"; So, how come it’s giving me this error message? A Database Error Occurred Error Number: 1046 No database selected INSERT INTO `your_stats` (`school`, `district`) VALUES ('TJHSST', 'FairFax') Is there any way for me to test if CodeIgniter can actually detect the mySQL databases I've created with phpMyAdmin in my MAMP stack?

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  • How can I troubleshoot flash player/hardware conflict?

    - by sparthikas
    OBJECTIVE: Have a web browser on my Ubuntu install that can play youtube and hulu videos. Also would like to understand problem so that I can fix it again if I change software. Workarounds welcome, technical understanding and solution preferable. SYMPTOMS: Flash does not run - cannot make the right-click menu appear, an empty box is where video should be, changes to black box when hovering over other links. The "The Adobe Flash plugin has crashed" message does not appear with its sad lego face. cannot activate proprietary graphics driver - causes system to reboot to a prompt. SOLUTIONS TRIED: Replaced OS (tried slackware 13.37, fedora 17, linuxmint 13 maya, gentoo, lubuntu, and even winXP. lubuntu confirmed to work, don't remember how much tweaking, if any, this required. Slack, fedora, mint, and gentoo all failed to run flash just like ubuntu) many reinstalls of flash player via different methods, including cleaning up old installs first, also tried gnash and lightspark. replaced graphics card (replaced HIS IceQ Radeon HD 4670 AGP with older GeForce 5700 LE no change in problem) flash does successfully work on winXP installation with Catalyst AGP hotfix driver applied, however I consider windows wholly unacceptable for web browsing due to lack of security. Lubuntu install also works, however I do not want to be tied down to just using Lubuntu on this computer. SYSINFO: Have latest versions of Ubuntu, Firefox, and Flash on fresh Ubuntu install. Using Gigabyte 7s748 motherboard with Athlon XP 2800+ and 3 GB of RAM with Radeon HD 4670 AGP card, also a Dell soundblaster live series sound card (due to malfunction of onboard sound on motherboard) Wired internet connection, Maxtor 6Y120L3 HDD, Sony DVD RW AW-Q170A, Dell M993s monitor. NOTES: I do not know if the graphics driver issue and the flash troubles are linked. Substitution of older graphics card having same flash troubles seems to suggest they aren't. My troubleshooting method is rather reductionist, consisting mainly of "replace things until you find out what was causing the error by process of elimination" only it seems that this must be a conflict which arises when software decides how to configure itself on my hardware. That is, I know the hardware can run Flash, and I know that on other systems the same software can too, but somehow the combination fails. Consequently I feel out of my depth. I will keep trying things off and on, but I have spent probably about 30 man-hours in the last 4 months working on this problem with no joy other than the lubuntu workaround. Any help will be appreciated, I will be checking back and posting updates. Any pertinent questions regarding me or my computer will be answered, outputs from config files can be accessed and posted (IDK which ones or what parts to post).

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  • Virtual PC and hardware-assisted virtualization (VT-x) problem

    - by Vesa Huovi
    I've installed Microsoft's Virtual PC on Windows 7, but when I try to start a virtual machine I get the following error message: '<Virtual machine name' could not be started because hardware-assisted virtualization is disabled. Please enable hardware virtualization in the BIOS settings and try again. If hardware virtualization settings is already enabled, you may have to disable Trusted Execution Technology (TXT) setting in BIOS or update the system BIOS. However, if I download and run the Hardware-Assisted Virtualization Detection Tool, it gives the following positive message: This computer is configured with hardware-assisted virtualization. This computer meets the processor requirements to run Windows Virtual PC. If this computer runs a supported edition of Windows® 7, you can install Windows Virtual PC. I've also used the MSR Walker in the third-party utility CrystalCPUID to examine MSR 0x3a on both processors on my system, and it's 0x5 (0x4 = VT enabled, 0x1 = VT lock), as expected. Does anyone have any ideas of what else to check? Thanks.

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  • hardware addressing and configurable addressing scheme

    - by Zia ur Rahman
    basically i want to ask question about configurable addressing scheme for LAN interface hardware. i have read about it from a book, some main points are given by a configurable addressing scheme provides a mechanism that a customer can use to set a physical address.The mechanism can be manual (the switches that must be set when the interface is first installed).or an electronic memory such as an EPROM that can be downloded from the computer(what does this means). Most hardware needs to be configured only once- configuration is usually done when the hardware is first installed. Question:Suppose a network administrator configures the LAN interface hardware (assigns the address) when he installs it. Now later on if he needs to change the physical address of the device can he change it? Or in this addressing scheme the hardware can only be configured once and we can not reconfigure it later on.

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