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RE2: a principled approach to regular expression matching

Regular expressions are one of computer science's shining examples of the benefits of good computer science theory. They were originally developed by theorists as a way to describe...

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Why no fortran standard library ?

- by Stefano Borini

To be a language focused on mathematics and scientific computing, I am always baffled by the total lack of useful mathematical routines in the Fortran standard library. One would expect it to be shipped at least with a routine to compute standard deviation and mean, but this is not the case. In particular with the introduction of Fortran 90 and the addition of modules (thus reducing namespace pollution), I don't see any reason why of this critical lack of services. I would like to hear your knowledge about why this is the case.

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C# Performance Pitfall – Interop Scenarios Change the Rules

- by Reed

C# and .NET, overall, really do have fantastic performance in my opinion. That being said, the performance characteristics dramatically differ from native programming, and take some relearning if you’re used to doing performance optimization in most other languages, especially C, C++, and similar. However, there are times when revisiting tricks learned in native code play a critical role in performance optimization in C#. I recently ran across a nasty scenario that illustrated to me how dangerous following any fixed rules for optimization can be… The rules in C# when optimizing code are very different than C or C++. Often, they’re exactly backwards. For example, in C and C++, lifting a variable out of loops in order to avoid memory allocations often can have huge advantages. If some function within a call graph is allocating memory dynamically, and that gets called in a loop, it can dramatically slow down a routine. This can be a tricky bottleneck to track down, even with a profiler. Looking at the memory allocation graph is usually the key for spotting this routine, as it’s often “hidden” deep in call graph. For example, while optimizing some of my scientific routines, I ran into a situation where I had a loop similar to: for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i]); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This loop was at a fairly high level in the call graph, and often could take many hours to complete, depending on the input data. As such, any performance optimization we could achieve would be greatly appreciated by our users. After a fair bit of profiling, I noticed that a couple of function calls down the call graph (inside of ProcessElement), there was some code that effectively was doing: // Allocate some data required DataStructure* data = new DataStructure(num); // Call into a subroutine that passed around and manipulated this data highly CallSubroutine(data); // Read and use some values from here double values = data->Foo; // Cleanup delete data; // ... return bar; Normally, if “DataStructure” was a simple data type, I could just allocate it on the stack. However, it’s constructor, internally, allocated it’s own memory using new, so this wouldn’t eliminate the problem. In this case, however, I could change the call signatures to allow the pointer to the data structure to be passed into ProcessElement and through the call graph, allowing the inner routine to reuse the same “data” memory instead of allocating. At the highest level, my code effectively changed to something like: DataStructure* data = new DataStructure(numberToProcess); for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i], data); } delete data; Granted, this dramatically reduced the maintainability of the code, so it wasn’t something I wanted to do unless there was a significant benefit. In this case, after profiling the new version, I found that it increased the overall performance dramatically – my main test case went from 35 minutes runtime down to 21 minutes. This was such a significant improvement, I felt it was worth the reduction in maintainability. In C and C++, it’s generally a good idea (for performance) to: Reduce the number of memory allocations as much as possible, Use fewer, larger memory allocations instead of many smaller ones, and Allocate as high up the call stack as possible, and reuse memory I’ve seen many people try to make similar optimizations in C# code. For good or bad, this is typically not a good idea. The garbage collector in .NET completely changes the rules here. In C#, reallocating memory in a loop is not always a bad idea. In this scenario, for example, I may have been much better off leaving the original code alone. The reason for this is the garbage collector. The GC in .NET is incredibly effective, and leaving the allocation deep inside the call stack has some huge advantages. First and foremost, it tends to make the code more maintainable – passing around object references tends to couple the methods together more than necessary, and overall increase the complexity of the code. This is something that should be avoided unless there is a significant reason. Second, (unlike C and C++) memory allocation of a single object in C# is normally cheap and fast. Finally, and most critically, there is a large advantage to having short lived objects. If you lift a variable out of the loop and reuse the memory, its much more likely that object will get promoted to Gen1 (or worse, Gen2). This can cause expensive compaction operations to be required, and also lead to (at least temporary) memory fragmentation as well as more costly collections later. As such, I’ve found that it’s often (though not always) faster to leave memory allocations where you’d naturally place them – deep inside of the call graph, inside of the loops. This causes the objects to stay very short lived, which in turn increases the efficiency of the garbage collector, and can dramatically improve the overall performance of the routine as a whole. In C#, I tend to: Keep variable declarations in the tightest scope possible Declare and allocate objects at usage While this tends to cause some of the same goals (reducing unnecessary allocations, etc), the goal here is a bit different – it’s about keeping the objects rooted for as little time as possible in order to (attempt) to keep them completely in Gen0, or worst case, Gen1. It also has the huge advantage of keeping the code very maintainable – objects are used and “released” as soon as possible, which keeps the code very clean. It does, however, often have the side effect of causing more allocations to occur, but keeping the objects rooted for a much shorter time. Now – nowhere here am I suggesting that these rules are hard, fast rules that are always true. That being said, my time spent optimizing over the years encourages me to naturally write code that follows the above guidelines, then profile and adjust as necessary. In my current project, however, I ran across one of those nasty little pitfalls that’s something to keep in mind – interop changes the rules. In this case, I was dealing with an API that, internally, used some COM objects. In this case, these COM objects were leading to native allocations (most likely C++) occurring in a loop deep in my call graph. Even though I was writing nice, clean managed code, the normal managed code rules for performance no longer apply. After profiling to find the bottleneck in my code, I realized that my inner loop, a innocuous looking block of C# code, was effectively causing a set of native memory allocations in every iteration. This required going back to a “native programming” mindset for optimization. Lifting these variables and reusing them took a 1:10 routine down to 0:20 – again, a very worthwhile improvement. Overall, the lessons here are: Always profile if you suspect a performance problem – don’t assume any rule is correct, or any code is efficient just because it looks like it should be Remember to check memory allocations when profiling, not just CPU cycles Interop scenarios often cause managed code to act very differently than “normal” managed code. Native code can be hidden very cleverly inside of managed wrappers

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Work Item Traceability in TFS 2010

- by Sam Patrick

I have created a Windows Form project (VS solution) under a TFS 2010 project. I may eventually add more solutions to the TFS project. My question: Can we create a Use Case WIT for a specific solution within a TFS project? Furthermore, is it possible to create a "traceability matrix" that starts at the Use Case level and goes down to the the code level (at least the namespace level) of that particular VS solution?

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Cluster Node Recovery Using Second Node in Solaris Cluster

- by Onur Bingul

Assumptions:Node 0a is the cluster node that has crashed and could not boot anymore.Node 0b is the node in cluster and in production with services active.Both nodes have their boot disk mirrored via SDS/SVM.We have many options to clone the boot disk from node 0b:- make a copy via network using the ufsdump command and pipe to ufsrestore - make a copy inserting the disk locally on node 0b and creating the third mirror with SDS- make a copy inserting the disk locally on node 0b using dd commandIn this procedure we are going to use dd command (from my experience this is the best option).Bare in mind that in the examples provided we work on Sun Fire V240 systems which have SCSI internal disks. In the case of Fibre Channel (FC) internal disks you must pay attention to the unique identifier, or World Wide Name (WWN), associated with each FC disk (in this case take a look at infodoc #40133 in order to recreate the device tree correctly).Procedure:On node 0b the boot disk is c1t0d0 (c1t1d0 mirror) and this is the VTOC:* Partition Tag Flags Sector Count Sector Mount Directory 0 2 00 0 2106432 2106431 1 3 01 2106432 74630784 76737215 2 5 00 0 143349312 143349311 4 7 00 76737216 50340672 127077887 5 4 00 127077888 14683968 141761855 6 0 00 141761856 1058304 142820159 7 0 00 142820160 529152 143349311We will insert the new disk on node 0b and it will be seen as c1t2d0.1) On node 0b we make a copy via dd from disk c1t0d0s2 to disk c1t2d0s2# dd if=/dev/rdsk/c1t0d0s2 of=/dev/rdsk/c1t2d0s2 bs=8192kA copy of a 72GB disk will take approximately about 45 minutes.Note: as an alternative to make identical copy of root over network follow Document ID: 47498Title: Sun[TM] Cluster 3.0: How to Rebuild a node with Veritas Volume Manager2) Perform an fsck on disk c1t2d0 data slices: 1. fsck -o f /dev/rdsk/c1t2d0s0 (root) 2. fsck -o f /dev/rdsk/c1t2d0s4 (/var) 3. fsck -o f /dev/rdsk/c1t2d0s5 (/usr) 4. fsck -o f /dev/rdsk/c1t2d0s6 (/globaldevices)3) Mount the root file system in order to edit following files for changing the node name:# mount /dev/dsk/c1t2d0s0 /mntChange the hostname from 0b to 0a:# cd /mnt/etc# vi hosts # vi hostname.bge0 # vi hostname.bge2 # vi nodename 4) Change the /mnt/etc/vfstab from the actual:/dev/md/dsk/d201 - - swap - no -/dev/md/dsk/d200 /dev/md/rdsk/d200 / ufs 1 no -/dev/md/dsk/d205 /dev/md/rdsk/d205 /usr ufs 1 no logging/dev/md/dsk/d204 /dev/md/rdsk/d204 /var ufs 1 no logging#/dev/md/dsk/d206 /dev/md/rdsk/d206 /globaldevices ufs 2 yes loggingswap - /tmp tmpfs - yes -/dev/md/dsk/d206 /dev/md/rdsk/d206 /global/.devices/node@2 ufs 2 noglobalto this (unencapsulate disk from SDS/SVM):/dev/dsk/c1t0d0s1 - - swap - no -/dev/dsk/c1t0d0s0 /dev/rdsk/c1t0d0s0 / ufs 1 no -/dev/dsk/c1t0d0s5 /dev/rdsk/c1t0d0s5 /usr ufs 1 no logging/dev/dsk/c1t0d0s4 /dev/rdsk/c1t0d0s4 /var ufs 1 no logging#/dev/md/dsk/d206 /dev/md/rdsk/d206 /globaldevices ufs 2 yes loggingswap - /tmp tmpfs - yes -/dev/dsk/c1t0d0s6 /dev/rdsk/c1t0d0s6 /global/.devices/node@1 ufs 2 no globalIt is important that global device partition (slice 6) in the new vfstab will point to the physical partition of the disk (in our case slice 6).Be careful with the name you use for the new disk. In this case we define it as c1t0d0 because we will insert it as target 0 in node 0a.But this could be different based on the configuration you are working on.5) Remove following entry from /mnt/etc/system (part of unencapsulation procedure):rootdev:/pseudo/md@0:0,200,blk6) Correct the link shared -> ../../global/.devices/node@2/dev/md/shared in order to point to the nodeid of node 0a (in our case nodeid 1):# cd /mnt/dev/mdhow it is now.... node 0b has nodeid 2lrwxrwxrwx 1 root root 42 Mar 10 2005 shared ->../../global/.devices/node@2/dev/md/shared# rm shared# ln -s ../../global/.devices/node@1/dev/md/shared sharedhow is going to be... with nodeid 1 for node 0alrwxrwxrwx 1 root root 42 Mar 10 2005 shared ->../../global/.devices/node@1/dev/md/shared7) Change nodeid (in our case from 2 to 1):# cd /mnt/etc/cluster# vi nodeid8) Change the file /mnt/etc/path_to_inst in order to reflect the correct nodeid for node 0a:# cd /mnt/etc# vi path_to_instChange entries from node@2 to node@1 with the vi command ":%s/node@2/node@1/g"9) Write the bootblock to the disk... just in case:# /usr/sbin/installboot /usr/platform/sun4u/lib/fs/ufs/bootblk /dev/rdsk/c1t2d0s0Now the disk is ready to be inserted in node 0a in order to bootup the node.10) Bootup node 0a with command "boot -sx"... this is becasue we need to make some changes in ccr files in order to recreate did environment.11) Modify cluster ccr:# cd /etc/cluster/ccr# rm did_instances# rm did_instances.bak# vi directory - remove the did_instances line.# /usr/cluster/lib/sc/ccradm -i /etc/cluster/ccr/directory # grep ccr_gennum /etc/cluster/ccr/directory ccr_gennum -1 # /usr/cluster/lib/sc/ccradm -i /etc/cluster/ccr/infrastructure # grep ccr_gennum /etc/cluster/ccr/infrastructure ccr_gennum -112) Bring the node 0a down again to the ok prompt and then issue the command "boot -r"Now the node will join the cluster and from scstat and metaset command you can verify functionality. Next step is to encapsulate the boot disk in SDS/SVM and create the mirrors.In our case node 0b has metadevice name starting from d200. For this reason on node 0a we need to create metadevice starting from d100. This is just an example, you can have different names.The important thing to remember is that metadevice boot disks have different names on each node.13) Remove metadevice pointing to the boot and mirror disks (inherit from node 0b):# metaclear -r -f d200# metaclear -r -f d201# metaclear -r -f d204# metaclear -r -f d205# metaclear -r -f d206verify from metastat that no metadevices are set for boot and mirror disks.14) Encapsulate the boot disk:# metainit -f d110 1 1 c1t0d0s0# metainit d100 -m d110# metaroot d10015) Reboot node 0a.16) Create all the metadevice for slices remaining on boot disk# metainit -f d111 1 1 c1t0d0s1# metainit d101 -m d111# metainit -f d114 1 1 c1t0d0s4# metainit d104 -m d114# metainit -f d115 1 1 c1t0d0s5# metainit d105 -m d115# metainit -f d116 1 1 c1t0d0s6# metainit d106 -m d11617) Edit the vfstab in order to specifiy metadevices created:old:/dev/dsk/c1t0d0s1 - - swap - no -/dev/md/dsk/d100 /dev/md/rdsk/d100 / ufs 1 no -/dev/dsk/c1t0d0s5 /dev/rdsk/c1t0d0s5 /usr ufs 1 no logging/dev/dsk/c1t0d0s4 /dev/rdsk/c1t0d0s4 /var ufs 1 no logging#/dev/md/dsk/d206 /dev/md/rdsk/d206 /globaldevices ufs 2 yes loggingswap - /tmp tmpfs - yes -/dev/dsk/c1t0d0s6 /dev/rdsk/c1t0d0s6 /global/.devices/node@1 ufs 2 no globalnew:/dev/md/dsk/d101 - - swap - no -/dev/md/dsk/d100 /dev/md/rdsk/d100 / ufs 1 no -/dev/md/dsk/d105 /dev/md/rdsk/d105 /usr ufs 1 no logging/dev/md/dsk/d104 /dev/md/rdsk/d104 /var ufs 1 no logging#/dev/md/dsk/106 /dev/md/rdsk/d106 /globaldevices ufs 2 yes loggingswap - /tmp tmpfs - yes -/dev/md/dsk/d106 /dev/md/rdsk/d106 /global/.devices/node@1 ufs 2 noglobal18) Reboot node 0a in order to check new SDS/SVM boot configuration.19) Label the mirror disk c1t1d0 with the VTOC of boot disk c1t0d0:# prtvtoc /dev/dsk/c1t0d0s2 > /var/tmp/VTOC_c1t0d0 # fmthard -s /var/tmp/VTOC_c1t0d0 /dev/rdsk/c1t1d0s220) Put DB replica on slice 7 of disk c1t1d0:# metadb -a -c 3 /dev/dsk/c1t1d0s721) Create metadevice for mirror disk c1t1d0 and attach the new mirror side:# metainit d120 1 1 c1t1d0s0# metattach d100 d120# metainit d121 1 1 c1t1d0s1# metattach d101 d121# metainit d124 1 1 c1t1d0s4# metattach d104 d124# metainit d125 1 1 c1t1d0s5# metattach d105 d125# metainit d126 1 1 c1t1d0s6# metattach d106 d126

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Simultaneous remote connections

- by user3215

Is there any package for Ubuntu which allows me to connect to remote computer without disturbing or terminating others who have already connected to that server or who are accessing the computer directly?. I remember I did this in Windows Server 2003 installing Terminal Server when I was doing my course which allowed multiple clients to connect to the server simultaneously with no disturbance to clients and even direct access to server. Is there any package like this for Ubuntu desktops?

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Tips on ensuring Model Quality

- by [email protected]

Given enough data that represents well the domain and models that reflect exactly the decision being optimized, models usually provide good predictions that ensure lift. Nevertheless, sometimes the modeling situation is less than ideal. In this blog entry we explore the problems found in a few such situations and how to avoid them.1 - The Model does not reflect the problem you are trying to solveFor example, you may be trying to solve the problem: "What product should I recommend to this customer" but your model learns on the problem: "Given that a customer has acquired our products, what is the likelihood for each product". In this case the model you built may be too far of a proxy for the problem you are really trying to solve. What you could do in this case is try to build a model based on the result from recommendations of products to customers. If there is not enough data from actual recommendations, you could use a hybrid approach in which you would use the [bad] proxy model until the recommendation model converges.2 - Data is not predictive enoughIf the inputs are not correlated with the output then the models may be unable to provide good predictions. For example, if the input is the phase of the moon and the weather and the output is what car did the customer buy, there may be no correlations found. In this case you should see a low quality model.The solution in this case is to include more relevant inputs.3 - Not enough cases seenIf the data learned does not include enough cases, at least 200 positive examples for each output, then the quality of recommendations may be low. The obvious solution is to include more data records. If this is not possible, then it may be possible to build a model based on the characteristics of the output choices rather than the choices themselves. For example, instead of using products as output, use the product category, price and brand name, and then combine these models.4 - Output leaking into input giving the false impression of good quality modelsIf the input data in the training includes values that have changed or are available only because the output happened, then you will find some strong correlations between the input and the output, but these strong correlations do not reflect the data that you will have available at decision (prediction) time. For example, if you are building a model to predict whether a web site visitor will succeed in registering, and the input includes the variable DaysSinceRegistration, and you learn when this variable has already been set, you will probably see a big correlation between having a Zero (or one) in this variable and the fact that registration was successful.The solution is to remove these variables from the input or make sure they reflect the value as of the time of decision and not after the result is known.

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Problems with subversion (in gnome keyring, maybe), user=null

- by Tom Brito

I'm having a problem with my subversion in Ubuntu, and it's happening only on my computer, my colleagues are working fine. It asks for password for user "(null)": Password for '(null)' GNOME keyring: entering the password it shows: svn: OPTIONS of 'http://10.0.203.3/greenfox': authorization failed: Could not authenticate to server: rejected Basic challenge (http://10.0.203.3) What can be causing that (again: it's just on my computer, the svn server is ok).

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Are highly capable programmers paid more than their managers?

- by Fun Mun Pieng

I know a lot of programmers are paid less than their managers by significant amounts, as highlighted there. How often is it that a programmer gets paid more than his manager? Or phrased different how many programmers are paid more than their managers? Personally, I know of one case. I'm asking to see how common is the case. When I say "manager", I mean anyone further up their organization hierarchy.

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SQL SERVER – Introduction to Function SIGN

- by pinaldave

Yesterday I received an email from a friend asking how do SIGN function works. Well SIGN Function is very fundamental function. It will return the value 1, -1 or 0. If your value is negative it will return you negative -1 and if it is positive it will return you positive +1. Let us start with a simple small example. DECLARE @IntVal1 INT, @IntVal2 INT,@IntVal3 INT DECLARE @NumVal1 DECIMAL(4,2), @NumVal2 DECIMAL(4,2),@NumVal3 DECIMAL(4,2) SET @IntVal1 = 9; SET @IntVal2 = -9; SET @IntVal3 = 0; SET @NumVal1 = 9.0; SET @NumVal2 = -9.0; SET @NumVal3 = 0.0; SELECT SIGN(@IntVal1) IntVal1,SIGN(@IntVal2) IntVal2,SIGN(@IntVal3) IntVal3 SELECT SIGN(@NumVal1) NumVal1,SIGN(@NumVal2) NumVal2,SIGN(@NumVal2) NumVal3 The above function will give us following result set. You will notice that when there is positive value the function gives positive values and if the values are negative it will return you negative values. Also you will notice that if the data type is INT the return value is INT and when the value passed to the function is Numeric the result also matches it. Not every datatype is compatible with this function. Here is the quick look up of the return types. bigint -> bigint int/smallint/tinyint -> int money/smallmoney -> money numeric/decimal -> numeric/decimal everybody else -> float What will be the best example of the usage of this function that you will not have to use the CASE Statement. Here is example of CASE Statement usage and the same replaced with SIGN function. USE tempdb GO CREATE TABLE TestTable (Date1 SMALLDATETIME, Date2 SMALLDATETIME) INSERT INTO TestTable (Date1, Date2) SELECT '2012-06-22 16:15', '2012-06-20 16:15' UNION ALL SELECT '2012-06-24 16:15', '2012-06-22 16:15' UNION ALL SELECT '2012-06-22 16:15', '2012-06-22 16:15' GO -- Using Case Statement SELECT CASE WHEN DATEDIFF(d,Date1,Date2) > 0 THEN 1 WHEN DATEDIFF(d,Date1,Date2) < 0 THEN -1 ELSE 0 END AS Col FROM TestTable GO -- Using SIGN Function SELECT SIGN(DATEDIFF(d,Date1,Date2)) AS Col FROM TestTable GO DROP TABLE TestTable GO This was interesting blog post for me to write. Let me know your opinion. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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Error splicing file: Input/output error with a USB SD/HC card reader [closed]

- by PirateRussell

I recently got a new Droid Bionic, and it has the SD/HC card. Today, I got a new USB card reader that reads the HC format. When I plug it into my Linux Mint 11 (katya), Gnome 32-bit computer, I get this error every I try to copy or move any file off of the card onto my desktop: Error splicing file: Input/output error I don't have the problem on a Windows Vista computer. Any ideas??? Thanks in advance...

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How to Never Use iTunes With Your iPhone, iPad, or iPod Touch

- by Chris Hoffman

iTunes isn’t an amazing program on Windows. There was a time when Apple device users had to plug their devices into their PCs or Macs and use iTunes for device activation, updates, and syncing, but iTunes is no longer necessary. Apple still allows you to use iTunes for these things, but you don’t have to. Your iOS device can function independently from iTunes, so you should never be forced to plug it into a PC or Mac. Device Activation When the iPad first came out, it was touted as a device that could replace full PCs and Macs for people who only needed to perform light computing tasks. Yet, to set up a new iPad, users had to plug it into a PC or Mac running iTunes and use iTunes to activate the device. This is no longer necessary. With new iPads, iPhones, and iPod Touches, you can simply go through the setup process after turning on your new device without ever having to plug it into iTunes. Just connect to a Wi-Fi or cellular data network and log in with your Apple ID when prompted. You’ll still see an option that allows you to activate the device via iTunes, but this should only be necessary if you don’t have a wireless Internet connection available for your device. Operating System Updates You no longer have to use Apple’s iTunes software to update to a new version of Apple’s iOS operating system, either. Just open the Settings app on your device, select the General category, and tap Software Update. You’ll be able to update right from your device without ever opening iTunes. Purchased iTunes Media Apple allows you to easily access content you’ve purchased from the iTunes Store on any device. You don’t have to connect your device to your computer and sync via iTunes. For example, you can purchase a movie from the iTunes Store. Then, without any syncing, you can open the iTunes Store app on any of your iOS devices, tap the Purchased section, and see stuff you’ve downloaded. You can download the content right from the store to your device. This also works for apps — apps you purchase from the App Store can be accessed in the Purchased section on the App Store on your device later. You don’t have to sync apps from iTunes to your device, although iTunes still allows you to. You can even set up automatic downloads from the iTunes & App Store settings screen. This would allow you to purchase content on one device and have it automatically download to your other devices without any hassle. Music Apple allows you to re-download purchased music from the iTunes Store in the same way. However, there’s a good chance you have your own music you didn’t purchase from iTunes. Maybe you spent time ripping it all from your old CDs and you’ve been syncing it to your devices via iTunes ever since. Apple’s solution for this is named iTunes Match. This feature isn’t free, but it’s not a bad deal at all. For $25 per year, Apple allows you to upload all your music to your iCloud account. You can then access all your music from any iPhone, IPad, or iPod Touch. You can stream all your music — perfect if you have a huge library and little storage on your device — and choose which songs you want to download to your device for offline use. When you add additional music to your computer, iTunes will notice it and upload it using iTunes Match, making it available for streaming and downloading directly from your iOS devices without any syncing. This feature is named iTunes Match because it doesn’t just upload music — if Apple already has a song you upload, it will “match” your song with Apple’s copy. This means you may get higher-quality versions of your songs if you ripped them from CD at a lower bitrate. Podcasts You don’t have to use iTunes to subscribe to podcasts and sync them to your devices. Even if you have a lowly iPod Touch, you can install APple’s Podcasts app from the app store. Use it to subscribe to podcasts and configure them to automatically download directly to your device. You can use other podcast apps for this, too. Backups You can continue backing up your device’s data through iTunes, generating local backups that are stored on your computer. However, new iOS devices are configured to automatically back up their data to iCloud. This happens automatically in the background without you even having to think about it, and you can restore such backups when setting up a device simply by logging in with your Apple ID. Personal Data In the days of PalmPilots, people would use desktop programs like iTunes to sync their email, contacts, and calendar events with their mobile devices. You probably shouldn’t have to sync this data form your computer. Just sign into your email account — for example, a Gmail account — on your device and iOS will automatically pull your email, contacts, and calendar events from your associated account. Photos Rather than connecting your iOS device to your computer and syncing photos from it, you can use an app that automatically uploads your photos to a web service. Dropbox, Google+, and even Flickr all have this feature in their apps. You’ll be able to access your photos from any computer and have a backup copy without any syncing required. You may still need to use iTunes if you want to sync local music without paying for iTunes Match or copy local video files to your device. Copying large local files over is the only real scenario where you’d need iTunes. If you don’t need to copy such files over, you can go ahead and uninstall iTunes from your Windows PC if you like. You shouldn’t need it.

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Developing a Cost Model for Cloud Applications

- by BuckWoody

Note - please pay attention to the date of this post. As much as I attempt to make the information below accurate, the nature of distributed computing means that components, units and pricing will change over time. The definitive costs for Microsoft Windows Azure and SQL Azure are located here, and are more accurate than anything you will see in this post: http://www.microsoft.com/windowsazure/offers/ When writing software that is run on a Platform-as-a-Service (PaaS) offering like Windows Azure / SQL Azure, one of the questions you must answer is how much the system will cost. I will not discuss the comparisons between on-premise costs (which are nigh impossible to calculate accurately) versus cloud costs, but instead focus on creating a general model for estimating costs for a given application. You should be aware that there are (at this writing) two billing mechanisms for Windows and SQL Azure: “Pay-as-you-go” or consumption, and “Subscription” or commitment. Conceptually, you can consider the former a pay-as-you-go cell phone plan, where you pay by the unit used (at a slightly higher rate) and the latter as a standard cell phone plan where you commit to a contract and thus pay lower rates. In this post I’ll stick with the pay-as-you-go mechanism for simplicity, which should be the maximum cost you would pay. From there you may be able to get a lower cost if you use the other mechanism. In any case, the model you create should hold. Developing a good cost model is essential. As a developer or architect, you’ll most certainly be asked how much something will cost, and you need to have a reliable way to estimate that. Businesses and Organizations have been used to paying for servers, software licenses, and other infrastructure as an up-front cost, and power, people to the systems and so on as an ongoing (and sometimes not factored) cost. When presented with a new paradigm like distributed computing, they may not understand the true cost/value proposition, and that’s where the architect and developer can guide the conversation to make a choice based on features of the application versus the true costs. The two big buckets of use-types for these applications are customer-based and steady-state. In the customer-based use type, each successful use of the program results in a sale or income for your organization. Perhaps you’ve written an application that provides the spot-price of foo, and your customer pays for the use of that application. In that case, once you’ve estimated your cost for a successful traversal of the application, you can build that into the price you charge the user. It’s a standard restaurant model, where the price of the meal is determined by the cost of making it, plus any profit you can make. In the second use-type, the application will be used by a more-or-less constant number of processes or users and no direct revenue is attached to the system. A typical example is a customer-tracking system used by the employees within your company. In this case, the cost model is often created “in reverse” - meaning that you pilot the application, monitor the use (and costs) and that cost is held steady. This is where the comparison with an on-premise system becomes necessary, even though it is more difficult to estimate those on-premise true costs. For instance, do you know exactly how much cost the air conditioning is because you have a team of system administrators? This may sound trivial, but that, along with the insurance for the building, the wiring, and every other part of the system is in fact a cost to the business. There are three primary methods that I’ve been successful with in estimating the cost. None are perfect, all are demand-driven. The general process is to lay out a matrix of: components units cost per unit and then multiply that times the usage of the system, based on which components you use in the program. That sounds a bit simplistic, but using those metrics in a calculation becomes more detailed. In all of the methods that follow, you need to know your application. The components for a PaaS include computing instances, storage, transactions, bandwidth and in the case of SQL Azure, database size. In most cases, architects start with the first model and progress through the other methods to gain accuracy. Simple Estimation The simplest way to calculate costs is to architect the application (even UML or on-paper, no coding involved) and then estimate which of the components you’ll use, and how much of each will be used. Microsoft provides two tools to do this - one is a simple slider-application located here: http://www.microsoft.com/windowsazure/pricing-calculator/ The other is a tool you download to create an “Return on Investment” (ROI) spreadsheet, which has the advantage of leading you through various questions to estimate what you plan to use, located here: https://roianalyst.alinean.com/msft/AutoLogin.do?d=176318219048082115 You can also just create a spreadsheet yourself with a structure like this: Program Element Azure Component Unit of Measure Cost Per Unit Estimated Use of Component Total Cost Per Component Cumulative Cost Of course, the consideration with this model is that it is difficult to predict a system that is not running or hasn’t even been developed. Which brings us to the next model type. Measure and Project A more accurate model is to actually write the code for the application, using the Software Development Kit (SDK) which can run entirely disconnected from Azure. The code should be instrumented to estimate the use of the application components, logging to a local file on the development system. A series of unit and integration tests should be run, which will create load on the test system. You can use standard development concepts to track this usage, and even use Windows Performance Monitor counters. The best place to start with this method is to use the Windows Azure Diagnostics subsystem in your code, which you can read more about here: http://blogs.msdn.com/b/sumitm/archive/2009/11/18/introducing-windows-azure-diagnostics.aspx This set of API’s greatly simplifies tracking the application, and in fact you can use this information for more than just a cost model. After you have the tracking logs, you can plug the numbers into ay of the tools above, which should give a representative cost or in some cases a unit cost. The consideration with this model is that the SDK fabric is not a one-to-one comparison with performance on the actual Windows Azure fabric. Those differences are usually smaller, but they do need to be considered. Also, you may not be able to accurately predict the load on the system, which might lead to an architectural change, which changes the model. This leads us to the next, most accurate method for a cost model. Sample and Estimate Using standard statistical and other predictive math, once the application is deployed you will get a bill each month from Microsoft for your Azure usage. The bill is quite detailed, and you can export the data from it to do analysis, and using methods like regression and so on project out into the future what the costs will be. I normally advise that the architect also extrapolate a unit cost from those metrics as well. This is the information that should be reported back to the executives that pay the bills: the past cost, future projected costs, and unit cost “per click” or “per transaction”, as your case warrants. The challenge here is in the model itself - statistical methods are not foolproof, and the larger the sample (in this case I recommend the entire population, not a smaller sample) is key. References and Tools Articles: http://blogs.msdn.com/b/patrick_butler_monterde/archive/2010/02/10/windows-azure-billing-overview.aspx http://technet.microsoft.com/en-us/magazine/gg213848.aspx http://blog.codingoutloud.com/2011/06/05/azure-faq-how-much-will-it-cost-me-to-run-my-application-on-windows-azure/ http://blogs.msdn.com/b/johnalioto/archive/2010/08/25/10054193.aspx http://geekswithblogs.net/iupdateable/archive/2010/02/08/qampa-how-can-i-calculate-the-tco-and-roi-when.aspx Other Tools: http://cloud-assessment.com/ http://communities.quest.com/community/cloud_tools

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Boot into Windows after uninstalling Ubuntu (Dual-boot)

- by user1320771

I had a Windows 7/Ubuntu dual-boot set up on my laptop. I deleted Ubuntu, and when I load up my computer, I am now met with a screen displaying the following: error: no such partition. grub rescue> How can I have my computer boot straight into Windows 7 again? Solved: I created a win7 system repair disc using another machine, and fixed the problem using the bootrec command within command prompt.

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.NET licenses and project worths millions

- by Ivan Tanasijevic

I have a question about. NET licenses. I heard that in the case when project becomes worth millions, Microsoft have rights on great percent of this amount. If this is true, then how are things with social network which is built with ASP.NET MVC. Is this the same situation as in the case of the profit coming from selling software, because in this situation profit comes from marketing not from direct selling software.

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Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

- by Motti Strom

Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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Do you write common pre-conditions for a large number of unit test cases ?

- by Vinoth Kumar

I have heard/read writing common pre-conditions for a large number of test cases is a bad thing, since this dependency may cause large number of test cases to fail if something changes . What are your thoughts on it ? If this is so , then what exactly is the purpose of setUp() method in Junit that runs before each test case ? If the same code inside setUp() runs before each test case , why cant it run only once before running all the test cases together ?

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Ubuntu Install 11.10 doesn't recognize Windows 7 installation with new HDD

- by arlendo

Replaced my crashed HDD with a Seagate 2TB Sata (bought from a company who pulled it from a working computer, OS unknown) and did a fresh install of Windows 7. Windows shows 100MB boot partition (bootable NTFS) and 200GB Windows partition (NTFS), the rest is unallocated. Win7 Disk Management says the partitioning type is Master Boot Record. Win7 boots and runs fine. Ubuntu 11.10 Install procedes to Allocate Drive Space screen and should say This computer currently has Windows 7 on it. What would you like to do? Instead, it says something like Install doesn't detect any existing OS on this computer. When I click on Something else, the partition table shows only the unallocated space of 1.8TB. Ubuntu Disk Utility says Partitioning: Master Boot Record, but GParted Live says Partition Table: gpt. It was my original intention to have the Windows boot partition and application partition, then install Ubuntu 11.10 using boot, root, swap, and home partitions, and maybe another partition just for data (mostly photos). Currently, I would be happy if I could just get Ubuntu installed along with Win7. I am aware of the MBR limits of 3 Primary partitions and 1 Extended partition. I suspect that my new HDD is partitioned for GPT and that is why Ubuntu can't see the Win7 installation. Am I on the right track? I was going to use Windows Disk Management to convert GPT to MBR but I only have the one drive on my AMD-64 mini-computer and it says I have to empty the drive of all partitions before I can access the Convert command. And I can't find any bootable software that would allow me to do that conversion. Here is the result of sudo fdisk -l: ubuntu@ubuntu:~$ sudo fdisk -l WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 224 heads, 19 sectors/track, 918004 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xd4a68c18 Device Boot Start End Blocks Id System /dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sda2 206848 419637247 209715200 7 HPFS/NTFS/exFAT ubuntu@ubuntu:~$ Keep in mind that I'm a definite newbie to screwing around with the inner workings of Ubuntu. I previously had Ubuntu 10.04 running with Vista and I don't remember even having to partition anything that wasn't automatic in the install. Thanks for taking a look here. My Win7 is running fine but I miss my Ubuntu.

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Exadata ROI cases

- by Javier Puerta

The following cases illustrate the type of ROI benefits that customers can obtain from their investment in Exadata infrastructure. Australian Finance Group will achieve a 42% ROI by and break even in three years by consolidating Oracle E-Business Suite and Siebel applications on Oracle Exadata. Read the ROI case at: http://www.oracle.com/us/corporate/customers/afg-1-exadata-cs-1354807.pdf In addition to this study, there are Oracle Exadata Mainstay ROI Case Studies for the following: Merck -Pharma, Oracle Exadata Achieves Fivefold Performance Increase for Critical Product Research Platform Turkcell Accelerates Reporting Tenfold, Saves on Storage and Energy Costs with Consolidated Oracle Exadata Platform

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Green Technology Management

Computer Recycling: Computer recycling is the recycling or reuse of computers. It includes both finding another use for materials and having systems dismantled in a manner that allows for the safe e... [Author: Chris Loo - Computers and Internet - April 09, 2010]

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What are the Key Requirements for Privacy Control Software?

Are you concerned about protecting your privacy regarding your computer activities? With today?s personal computers and operating systems insuring your privacy on your personal computer requires much... [Author: Chet Childers - Computers and Internet - August 24, 2009]

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Green Technology Management

Computer Recycling: Computer recycling is the recycling or reuse of computers. It includes both finding another use for materials and having systems dismantled in a manner that allows for the safe e... [Author: Chris Loo - Computers and Internet - April 26, 2010]

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How does someone with a business degree become a software consultant?

- by gambit14

I'm a 4th year computer engineering student from a reputable university in Toronto and i'm curious as to how some of these software consulting positions with the large firms (Accenture, Deloitte, IBM, etc.) accept business grads as well as comp-sci and computer engineers? How does a business grad consult on software without having a background in software? Besides communication skills and other soft skills, what separates me from a business grad for these positions? Thanks.

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How to Get Burned by Your Internet History

Burned by your Internet history? What do you mean? Perhaps you are not aware but your personal computer is one big, powerful recorder of all your computer activity. Whether you are searching the Inte... [Author: Chet Childers - Computers and Internet - August 24, 2009]

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Protection against CheatEngine and other injectors [duplicate]

- by Lucas

This question already has an answer here: Strategies to Defeat Memory Editors for Cheating - Desktop Games 10 answers Is protection against CheatEngine and other inject tools are possible to do? I was thinking a day and the only one idea I've got is about writting some small application which will scan the processes running every second, and in case if any injector will be found the game client will exit immadiately. I'm writing here to see your opinions on this case as some of you may have some expierence against protecting the game clients against DLL or PYC injection or something.

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