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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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  • 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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  • 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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  • 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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  • How can user change the jre parameter values after the exe is generated in Launch4j?

    - by Wing C. Chen
    Is it possible to change the jre parameter values after the exe file is generated through Launch4j? The ideal scenario is like this: The default parameter values are applied when the program is started. However, when the user wants to change some jre parameter values, he goes to a .ini file, MyProgram.ini for example, changes the values there, and the new values will be applied next time the program is started. I think eclipse uses the same way for its memory and some other parameter settings.

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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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  • 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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  • 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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  • 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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  • T-SQL query with date range

    - by Moo
    Hi, I have a fairly weird 'bug' with a simple query, and I vaguely remember reading the reason for it somewhere a long time ago but would love someone to refresh my memory. The table is a basic ID, Datetime table. The query is: select ID, Datetime from Table where Datetime <= '2010-03-31 23:59:59' The problem is that the query results include results where the Datetime is '2010-04-01 00:00:00'. The next day. Which it shouldn't. Anyone? Cheers Moo

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  • Subclassing NSObject, can it cause problems?

    - by Sheehan Alam
    I have a very basic data class that is subclassed from NSObject. I declare a few strings, make sure they have properties (nonatomic, copy), and synthesize them. The only method I implemented was dealloc() which releases my strings. Can any memory problems arise from just this? Are there any other methods I need to implement?

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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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  • 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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  • How can Nagios handle non-threshold based plugins?

    - by FliesLikeABrick
    I am writing a Nagios plugin to monitor trends of a certain storage resource utilization (e.g. gradual increases are fine, but an instantaneous/sudden increase or decrease in resource usage may indicate a problem). For what it's worth, it is reviewing the last N entries in an RRD file generated by a custom cacti data source/templates. What is the "right" way to handle Nagios notification config/implementation for this? The problem is that it the plugin would exit as warning/critical for one polling period, but in the next it would be fine (or 3 polling periods later, if I look at 3 polling periods worth of data). I guess the question is: should I just write it in such a way that it will alert for X polling periods, or should I find a way to write it such that manual intervention is required for it to clear (such as logging into the monitoring server or hitting a URL to run a script that submits a passive result)? Your input is appreciated, and if you have any tips for how to implement the latter I'm open to them (I can think of a few ways to possibly implement it)

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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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  • 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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  • Caching Reverse-Proxy ISP Host for a Low-Bandwidth Server

    - by Casey
    I am building a webcam w/ HTTP server that will be running from a low-bandwith connection. The content on the site will be changing every 5 to 10 minutes. Instead of serving files directly from this connection, are there hosting companies that can act as a reverse proxy for my site? Therefore, if nobody is using the site, the local internet connection remains idle. And if I receive 1000 hits all at the same time, only one HTTP GET is required, and the hosting company (on a fat pipe) continues serving the other 999 requests? This doesn't sound like a very common usage model, but I feel like this would be the optimal solution to my situation.

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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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  • 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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  • 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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  • Why is my mdadm raid-1 recovery so slow?

    - by dimmer
    On a system I'm running Ubuntu 10.04. My raid-1 restore started out fast but quickly became ridiculously slow (at this rate the restore will take 150 days!): dimmer@paimon:~$ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdc1[2] sdb1[1] 1953513408 blocks [2/1] [_U] [====>................] recovery = 24.4% (477497344/1953513408) finish=217368.0min speed=113K/sec unused devices: <none> Eventhough I have set the kernel variables to reasonably quick values: dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_min 1000000 dimmer@paimon:~$ cat /proc/sys/dev/raid/speed_limit_max 100000000 I am using 2 2.0TB Western Digital Hard Disks, WDC WD20EARS-00M and WDC WD20EARS-00J. I believe they have been partitioned such that their sectors are aligned. dimmer@paimon:/sys$ sudo parted /dev/sdb GNU Parted 2.2 Using /dev/sdb Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00M (scsi) Disk /dev/sdb: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 (parted) unit s (parted) p Number Start End Size File system Name Flags 1 2048s 3907028991s 3907026944s ext4 (parted) q dimmer@paimon:/sys$ sudo parted /dev/sdc GNU Parted 2.2 Using /dev/sdc Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) p Model: ATA WDC WD20EARS-00J (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/4096B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 2000GB 2000GB ext4 I am beginning to think that I have a hardware problem, otherwise I can't imagine why the mdadm restore should be so slow. I have done a benchmark on /dev/sdc using Ubuntu's disk utility GUI app, and the results looked normal so I know that sdc has the capability to write faster than this. I also had the same problem on a similar WD drive that I RMAd because of bad sectors. I suppose it's possible they sent me a replacement with bad sectors too, although there are no SMART values showing them yet. Any ideas? Thanks. As requested, output of top sorted by cpu usage (notice there is ~0 cpu usage). iowait is also zero which seems strange: top - 11:35:13 up 2 days, 9:40, 3 users, load average: 2.87, 2.58, 2.30 Tasks: 142 total, 1 running, 141 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3096304k total, 1482164k used, 1614140k free, 617672k buffers Swap: 1526132k total, 0k used, 1526132k free, 535416k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 45 root 20 0 0 0 0 S 0 0.0 2:17.02 scsi_eh_0 1 root 20 0 2808 1752 1204 S 0 0.1 0:00.46 init 2 root 20 0 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/0 4 root 20 0 0 0 0 S 0 0.0 0:00.17 ksoftirqd/0 5 root RT 0 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT 0 0 0 0 S 0 0.0 0:00.02 migration/1 ... dmesg errors, definitely looking like hardware: [202884.000157] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [202884.007015] ata5.00: failed command: FLUSH CACHE EXT [202884.013728] ata5.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0 [202884.013730] res 40/00:00:ff:59:2e/00:00:35:00:00/e0 Emask 0x4 (timeout) [202884.033667] ata5.00: status: { DRDY } [202884.040329] ata5: hard resetting link [202889.400050] ata5: link is slow to respond, please be patient (ready=0) [202894.048087] ata5: COMRESET failed (errno=-16) [202894.054663] ata5: hard resetting link [202899.412049] ata5: link is slow to respond, please be patient (ready=0) [202904.060107] ata5: COMRESET failed (errno=-16) [202904.066646] ata5: hard resetting link [202905.840056] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [202905.849178] ata5.00: configured for UDMA/133 [202905.849188] ata5: EH complete [203899.000292] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [203899.007096] ata5.00: failed command: IDENTIFY DEVICE [203899.013841] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [203899.013843] res 40/00:00:ff:f9:f6/00:00:38:00:00/e0 Emask 0x4 (timeout) [203899.041232] ata5.00: status: { DRDY } [203899.048133] ata5: hard resetting link [203899.816134] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [203899.826062] ata5.00: configured for UDMA/133 [203899.826079] ata5: EH complete [204375.000200] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204375.007421] ata5.00: failed command: IDENTIFY DEVICE [204375.014799] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204375.014800] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204375.044374] ata5.00: status: { DRDY } [204375.051842] ata5: hard resetting link [204380.408049] ata5: link is slow to respond, please be patient (ready=0) [204384.440076] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204384.449938] ata5.00: configured for UDMA/133 [204384.449955] ata5: EH complete [204395.988135] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen [204395.988140] ata5.00: failed command: IDENTIFY DEVICE [204395.988147] ata5.00: cmd ec/00:01:00:00:00/00:00:00:00:00/00 tag 0 pio 512 in [204395.988149] res 40/00:00:ff:0c:0f/00:00:39:00:00/e0 Emask 0x4 (timeout) [204395.988151] ata5.00: status: { DRDY } [204395.988156] ata5: hard resetting link [204399.320075] ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300) [204399.330487] ata5.00: configured for UDMA/133 [204399.330503] ata5: EH complete

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