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  • Why is the software world full of status codes?

    - by David V McKay
    Why did programmers ever start using status codes? I mean, I guess I could imagine this might be useful back in the days when a text string was an expensive resource. WAYYY back then. But even after we had megabytes of memory to work with, we continued to use them. What possible advantage could there be for obfuscating the meaning of an error message or status message behind a status code?

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  • Should we denormalize database to improve performance?

    - by Groo
    We have a requirement to store 500 measurements per second, coming from several devices. Each measurement consists of a timestamp, a quantity type, and several vector values. Right now there is 8 vector values per measurement, and we may consider this number to be constant for needs of our prototype project. We are using HNibernate. Tests are done in SQLite (disk file db, not in-memory), but production will probably be MsSQL. Our Measurement entity class is the one that holds a single measurement, and looks like this: public class Measurement { public virtual Guid Id { get; private set; } public virtual Device Device { get; private set; } public virtual Timestamp Timestamp { get; private set; } public virtual IList<VectorValue> Vectors { get; private set; } } Vector values are stored in a separate table, so that each of them references its parent measurement through a foreign key. We have done a couple of things to ensure that generated SQL is (reasonably) efficient: we are using Guid.Comb for generating IDs, we are flushing around 500 items in a single transaction, ADO.Net batch size is set to 100 (I think SQLIte does not support batch updates? But it might be useful later). The problem Right now we can insert 150-200 measurements per second (which is not fast enough, although this is SQLite we are talking about). Looking at the generated SQL, we can see that in a single transaction we insert (as expected): 1 timestamp 1 measurement 8 vector values which means that we are actually doing 10x more single table inserts: 1500-2000 per second. If we placed everything (all 8 vector values and the timestamp) into the measurement table (adding 9 dedicated columns), it seems that we could increase our insert speed up to 10 times. Switching to SQL server will improve performance, but we would like to know if there might be a way to avoid unnecessary performance costs related to the way database is organized right now. [Edit] With in-memory SQLite I get around 350 items/sec (3500 single table inserts), which I believe is about as good as it gets with NHibernate (taking this post for reference: http://ayende.com/Blog/archive/2009/08/22/nhibernate-perf-tricks.aspx). But I might as well switch to SQL server and stop assuming things, right? I will update my post as soon as I test it.

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  • OLTP Sql Server RAID configuration with 10 disks, allocation Unit and disk stripe size

    - by Chris Wood
    On a new db server I only have 10 disks to play with, The usage is about a booking every 3-5 seconds, so not high volume, I know compromises have to be made, but my initial thoughts are - DISK 1 & 2 - RAID 1 - OS DISKS 3,4,5,6 - RAID 10 - Data, Indexes & TempDB DISKS 7,8,9,10 - RAID 10 - Logs & Backup Full backups will take place when there is virtually no traffic on the website so not bothered about the contention with the logs. disk 3-10 - 8kb NTFS unit allocation size disk 3-10 - 64kb Disk Stripe size does this seems to be sensible, any other considerations I have omitted ? thanks

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  • Java Garbage Collection

    - by pietervn
    I was wondering about the garbage collection that takes place in Java. Is it really able to handle all objects that aren't used and free up the most possible memory? I also want to know how does the Java garbage collection compare to another language like lets say C#? And then, how does the automatic garbage collection measure up against manual collection from a language like C?

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  • how to create partition on windows CE device

    - by mack369
    Is there any tool to create a new partition on windows CE device? Device has a NAND flash memory and initially there were two partitions. Using Storage manager in Control Panel I was able to delete one partition but when I want to create it again, I get an error message: "Unable to create partition".

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  • Built in Analyzer in Xcode 3.1.4

    - by Mustafa
    Hi all, I wonder if the built in Analyzer in Xcode 3.1.4 makes it redundant to use LLVM/Clang Static Analyzer separately? Please refer to the original article here: Finding memory leaks with the LLVM/Clang Static Analyzer Thanks.

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  • C programming getting back into it - the red pill

    - by JavaRocky
    Can someone provide recommended reading, website resources or best practices to follow when programming with C. I am a proficient software developer with strong skills in Java and PHP. Is there standard libraries these days which people use? Like what spring is to java? And standard design patterns for managing memory or even standard libraries for that fact? I want to write solid, maintainable C programs. GO THE RED PILL! :P

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  • Search and replace global modifier

    - by mrucci
    Is there any reason why non-global/first-occurrence substitution is the default in many text editing programs (vim, sed, perl, etc.)? I am talking about the /g flag of search and replace commands like: :s/pan/focaccia/g # in vim sed 's/sfortuna/fortuna/g' # with sed that will substitute every occurrence of the search pattern with the replacement string. After (not too) many years of vim and sed usage I still did not find any use case for non-global substitutions. Is there some valid historical reason? Or it is because it is? Thanks.

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  • What would be the best .NET 2.0 type to represent .NET 3.5 HashSet<T>?

    - by Will Marcouiller
    I'm writing myself a class library to manage Active Directory. I have an interface: Public Interface ISourceAnnuaire(Of T as {IGroupe, ITop, IUniteOrganisation, IUtilisateur}) Readonly Property Changements As Dictionary(Of T, HashSet(Of String)) End Interface This Changements property is used to save in memory the changes that occur on a particular element that is part of the source. However, I am stuck with .NET Framework 2.0. What would be the closest .NET 2.0 for HashSet(Of String)?

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  • SQL Server cluster performance baseline

    - by Dwight T
    Currently I'm tasked with getting a good performance baseline on a SQL 2005 cluster. The main db on the server is for Sharepoint, but I would like to add other dbs on the cluster. I do have access to Quest's Performance Analysis tool to help. What are key factors to look at to see if the cluster can handle additional dbs? Do you look at different performance indicators for a cluster vs a stand alone sql server? One db will be a low usage transactional db and a read only db that is used for sales data. Thanks Dwight

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  • Filtering Attributes with Weka

    - by hrzafer
    Hi eveyone! I have a simple question about filtering attributes in WEKA. Let's say I have 500 attributes 30 classes and 100 samples for each class which equals 3000 rows and 500 columns. This causes time and memory problems a you can guess. How do I filter attributes that occur only once or twice (or n times) in 3000 rows. And is it a good idea? Thank you

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  • How do access a secure website within a sharepoint webpart?

    - by Bill
    How do access a secure website within a sharepoint webpart? The following code works fine as a console application but if you run it in a webpart, you will get a access violation WebRequest request = WebRequest.Create("https://somesecuresite.com"); WebResponse firstResponse = null; try { firstResponse = request.GetResponse(); } catch (WebException ex) { writer.WriteLine("Error: " + ex.ToString()); return; } if you access a non secure site, it also works. Any ideas? Error: System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. --- System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at System.Net.UnsafeNclNativeMethods.NativePKI.CertVerifyCertificateChainPolicy(IntPtr policy, SafeFreeCertChain chainContext, ChainPolicyParameter& cpp, ChainPolicyStatus& ps) at System.Net.PolicyWrapper.VerifyChainPolicy(SafeFreeCertChain chainContext, ChainPolicyParameter& cpp) at System.Net.Security.SecureChannel.VerifyRemoteCertificate(RemoteCertValidationCallback remoteCertValidationCallback) at System.Net.Security.SslState.CompleteHandshake() at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult) at System.Net.TlsStream.CallProcessAuthentication(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result) at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size) at System.Net.PooledStream.Write(Byte[] buffer, Int32 offset, Int32 size) at System.Net.ConnectStream.WriteHeaders(Boolean async) --- End of inner exception stack trace --- at System.Net.HttpWebRequest.GetResponse()

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  • Reccomendation for tuning 100's of Sql Databases

    - by wayne
    Hi, I'm running several sql servers, each running a few hundred multi gig databases for customers. They are all setup homogeneously as far as the schemas are concerned, however customer usages of the data differ quite alot from database to database. What would be the best way to auto-index / profile / tune this large amount of databases? As there are atleast 600 or more catalogs i cant have someone manually profile, and index as required by each databases usage patterns. I'm currently running SQL 2005 but will be moving to 2008, so solutions that work with either are fine!

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  • reducing Windows 7 size

    - by Sejanus
    My Windows 7 uses around 16 GB while Windows XP only around 4 GB hard disk space. Seems weird. I use Windows only for gaming so I dont need a lot of stuff they have to offer. What is the best way to reduce Windows 7 size? What can I delete / uninstall and how? Also I'd like reduce RAM and processor usage as much as possible (as long as it doesnt hurt game performance)... turn off all that fancy stuff and so on. What can I turn off and how? Thanks in advance!

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  • Char* vs std::string

    - by Lockyer
    Is there any advantage to using char*'s instead of std::string? I know char*'s are usually defined on the stack, so we know exactly how much memory we'll use, is this actually a good argument for their use? Or is std::string better in every way?

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  • Performance tuning of a Hibernate+Spring+MySQL project operation that stores images uploaded by user

    - by Umar
    Hi I am working on a web project that is Spring+Hibernate+MySQL based. I am stuck at a point where I have to store images uploaded by a user into the database. Although I have written some code that works well for now, but I believe that things will mess up when the project would go live. Here's my domain class that carries the image bytes: @Entity public class Picture implements java.io.Serializable{ long id; byte[] data; ... // getters and setters } And here's my controller that saves the file on submit: public class PictureUploadFormController extends AbstractBaseFormController{ ... protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception{ MutlipartFile file; // getting MultipartFile from the command object ... // beginning hibernate transaction ... Picture p=new Picture(); p.setData(file.getBytes()); pictureDAO.makePersistent(p); // this method simply calls getSession().saveOrUpdate(p) // committing hiernate transaction ... } ... } Obviously a bad piece of code. Is there anyway I could use InputStream or Blob to save the data, instead of first loading all the bytes from the user into the memory and then pushing them into the database? I did some research on hibernate's support for Blob, and found this in Hibernate In Action book: java.sql.Blob and java.sql.Clob are the most efficient way to handle large objects in Java. Unfortunately, an instance of Blob or Clob is only useable until the JDBC transaction completes. So if your persistent class defines a property of java.sql.Clob or java.sql.Blob (not a good idea anyway), you’ll be restricted in how instances of the class may be used. In particular, you won’t be able to use instances of that class as detached objects. Furthermore, many JDBC drivers don’t feature working support for java.sql.Blob and java.sql.Clob. Therefore, it makes more sense to map large objects using the binary or text mapping type, assuming retrieval of the entire large object into memory isn’t a performance killer. Note you can find up-to-date design patterns and tips for large object usage on the Hibernate website, with tricks for particular platforms. Now apparently the Blob cannot be used, as it is not a good idea anyway, what else could be used to improve the performance? I couldn't find any up-to-date design pattern or any useful information on Hibernate website. So any help/recommendations from stackoverflowers will be much appreciated. Thanks

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  • Change install path to /usr/bin instead of /usr/local/bin

    - by user1678788
    A simple question, but I have no concrete documentation to confirm my answer. When installing software with the make install command under a unix machine, the default path is going over to /usr/local/bin. I would like to update a package system-wide under /usr/bin. How (and where) do I change the command under make or make install to /usr/bin? Also - Can the package remain on /usr/local/bin but the systemwide usage of Python (the update being installed) be changed to /usr/local/bin from /usr/bin to avoid modifying the original installed version ?

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  • Summary of the last decade of garbage collection?

    - by Ben Karel
    I've been reading through the Jones & Lin book on garbage collection, which was published in 1996. Obviously, the computing world has changed dramatically since then: multicore, out-of-order chips with large caches, and even larger main memory in desktops. The world has also more-or-less settled on the x86 and ARM microarchitectures for most consumer-facing systems. How has the field of garbage collection changed since the seminal book was published?

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  • BigInteger.pow(BigInteger) ?

    - by PeterW
    I'm playing with numbers in Java, and want to see how big a number I can make. It is my understanding that BigInteger can hold a number of infinite size, so long as my computer has enough Memory to hold such a number, correct? My problem is that BigInteger.pow accepts only an int, not another BigInteger, which means I can only use a number up to 2,147,483,647 as the exponent. Is it possible to use the BigInteger class as such? BigInteger.pow(BigInteger) Thanks.

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  • organizing images by resolution with batch files

    - by Anthony
    Doing some digging I'm trying to figure out a command line solution for organizing very large archives of images based on their resolution into folders, 1920x1080, 1600x1200, 1600x900, etc. I've come across a few post on Superuser mentioning something called ImageMagick, is that the best method to the madness I'm trying to accomplish? I've never used any command line functions/applets/tools other then those that come from Microsoft. I'm rather new to command line usage but ive been enjoying the hell out of it using Powershell, xcopy and robocopy. I am slowly trying to push myself further into the Linux world with Ubuntu running on one of my physical machines as well as a virtual machine so that's an option as well.

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  • AMD FX 8350 potentially overheating

    - by rhughes
    I am worried that my CPU is overheating when running at maximum capacity. I have not overclocked the machine. The machine often powers down after a couple of minutes of max CPU usage. I get the following events in the Event Log after the crash: Log Name: System Source: Microsoft-Windows-Kernel-Power Date: 11/10/2013 12:05:40 Event ID: 41 Task Category: (63) Level: Critical Keywords: (2) User: SYSTEM Computer: home-pc Description: The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly. What can I do to confirm this or further narrow down this issue? Due to the sudden nature of the crash, no MEMORY.DMP is created I believe. I am happy to post any extra information that is needed.

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  • Why do my download speeds drastically vary during a download?

    - by J. Anthony Carter
    I watch the download speed rise and fall like waves in a storm. At night, during low bandwidth usage I have achieve speeds as high as 3.23 M/sec but the watch them decline to 250 K/sec. and then climb back up. Over and over. During the day my best is around 1.67 M/sec with lows into the 65 K/sec. On top of this, why does a download need to slow down when approaching the end of the download? It's not like a multi-hundred ton train needing to decrease speed as it approaches the station.

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  • Suggestions for a SOHO/Home Asterisk system

    - by James
    I would like to buy a small embedded system that runs Linux and Asterisk. I would like two FXS ports ( to plug analogue phones into ) and one FXO port ( to plug in to my real line to allow access to the POTS ). I would like it to have a USB port to hold storage for voicemail. I really want it for home use so I would like it to be under £150 ( say $250 ), given that you can buy ADSL routers for around this much can any of them be made to run Linux and Asterisk? I don't want a PC as the power usage would be too high. I am looking for something like this ASDL router but open and able to run Asterisk or another open PBX. At worst I would like a box which had one FXO and two FXS and just made them completely available over IP to a full Asterisk system on a low power Atom system.

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  • Saving child collections with NHibernate

    - by Ben
    Hi, I am in the process or learning NHibernate so bare with me. I have an Order class and a Transaction class. Order has a one to many association with transaction. The transaction table in my database has a not null constraint on the OrderId foreign key. Order class: public class Order { public virtual Guid Id { get; set; } public virtual DateTime CreatedOn { get; set; } public virtual decimal Total { get; set; } public virtual ICollection<Transaction> Transactions { get; set; } public Order() { Transactions = new HashSet<Transaction>(); } } Order Mapping: <class name="Order" table="Orders"> <cache usage="read-write"/> <id name="Id"> <generator class="guid"/> </id> <property name="CreatedOn" type="datetime"/> <property name="Total" type="decimal"/> <set name="Transactions" table="Transactions" lazy="false" inverse="true"> <key column="OrderId"/> <one-to-many class="Transaction"/> </set> Transaction Class: public class Transaction { public virtual Guid Id { get; set; } public virtual DateTime ExecutedOn { get; set; } public virtual bool Success { get; set; } public virtual Order Order { get; set; } } Transaction Mapping: <class name="Transaction" table="Transactions"> <cache usage="read-write"/> <id name="Id" column="Id" type="Guid"> <generator class="guid"/> </id> <property name="ExecutedOn" type="datetime"/> <property name="Success" type="bool"/> <many-to-one name="Order" class="Order" column="OrderId" not-null="true"/> Really I don't want a bidirectional association. There is no need for my transaction objects to reference their order object directly (I just need to access the transactions of an order). However, I had to add this so that Order.Transactions is persisted to the database: Repository: public void Update(Order entity) { using (ISession session = NHibernateHelper.OpenSession()) { using (ITransaction transaction = session.BeginTransaction()) { session.Update(entity); foreach (var tx in entity.Transactions) { tx.Order = entity; session.SaveOrUpdate(tx); } transaction.Commit(); } } } My problem is that this will then issue an update for every transaction on the order collection (regardless of whether it has changed or not). What I was trying to get around was having to explicitly save the transaction before saving the order and instead just add the transactions to the order and then save the order: public void Can_add_transaction_to_existing_order() { var orderRepo = new OrderRepository(); var order = orderRepo.GetById(new Guid("aa3b5d04-c5c8-4ad9-9b3e-9ce73e488a9f")); Transaction tx = new Transaction(); tx.ExecutedOn = DateTime.Now; tx.Success = true; order.Transactions.Add(tx); orderRepo.Update(order); } Although I have found quite a few articles covering the set up of a one-to-many association, most of these discuss retrieving of data and not persisting back. Many thanks, Ben

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