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  • General directions on developing a server side control system for JS/Canvas Action RPG

    - by Billy Ninja
    Well, yesterday I asked on anti-cheat JS, and confirmed what I kind of already knew that it's just not possible. Now I wanna measure roughly how hard it is to implement a server side checking that is agnostic to client input, that does not mess with the game experience so much. I don't wanna waste to much resource on this matter, since it's going to be initially a single player game, that I may or would like to introduce some kind of ranking, trading system later on. I'd rather deliver better more cool game features instead. I don't wanna have to guarantee super fast server response to keep the game going lag free. I'd rather go with more loose discrete control of key variables and instances. Like store user's action on a fifo buffer on the client, and push that actions to the server gradually. I'd love to see a elegant, generic solution that I could plug into my client game logic root (not having to scatter treatments everywhere in my client js) - and have few classes on Node.js server that could handle that - without having to mirror/describe all of my game entities a second time on the server.

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  • ext4 jbd2 journaling active even on empty filesystem

    - by Paul
    I have been having several issues with my ext4 filesystems that seem to be due to jbd2 journaling. I made a related post here and am rephrasing it with the hope that someone may be able to help. For a minimal example, I start with an empty 8gb USB stick and use gparted to create one ext4 partition. The command used by gparted when creating the ext4 file system is: mkfs.ext4 -j -O extent -L DataTraveler8gb /dev/sde1 I check the filesystem with gparted: e2fsck -f -y -v /dev/sde1 and I mount it: sudo mount /dev/sde1 /media/test The disk is empty, but the journaling is very active on this disk (/dev/sde1). The other disks are ext4 SSDs formatted similarly. A snapshot of iotop: % sudo iotop -oPa Total DISK READ: 0.00 B/s | Total DISK WRITE: 2027.21 K/s PID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND 262 be/3 root 0.00 B 56.00 K 0.00 % 0.18 % [jbd2/sda1-8] 29069 be/3 root 0.00 B 0.00 B 0.00 % 0.16 % [jbd2/sde1-8] 891 be/3 root 0.00 B 4.00 K 0.00 % 0.03 % [jbd2/sdc1-8] What is jbd2 doing with /dev/sde1? If I follow the same steps with a larger 2Tb disk, iotop indicates this empty disk is constantly being written to by jbd2 at the rate of Mb/s as soon as I mount it. On the other disks, which have the OS and /home, I have tried to find if any files are being modified by processes to cause this behavior but couldn't find any. I also moved many of the disk intensive process to use a tmpfs. And used noatime. I have another non-SSD hard disk on this machine, /dev/sdb, that is also ext4 but was not formatted by gparted (given to me by a coworker). It does not appear in iotop. So I am assuming there an issue with gparted. Any suggestions are appreciated. Also any tips on how to modify existing partitions to fix the issue without having to start from scratch would be great. There are some posts related to jbd2 but they didn't help (eg. here).

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  • Email attachments sent to a group don't show up for some

    - by blsub6
    My boss sent out an email from my Exchange 2010 org and attached a PDF and a Word doc to it. He came back the next day and told me that some of the 8 or 10 people that received this email could open up the attachments no problem. The other 2 or 3 people, could not. One of these people who could not open the attachment, went so far as to call Comcast (his email service provider) and ask them where his attachments went. Comcast told this person that when they received the email, the attachment was 0 bytes in size. This may sound like more of a rant than a question but I'm genuinely concerned. Is there any possible way that something could have gone wrong on my end that sent out the email to some with the attachment and to some without?

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  • Gre Tunnel Cisco Linux traffic forwarding

    - by mezgani
    I setup a gre tunnel a cisco router and a Linux machine, the tunnel interface in the Linux box named pic. Well i have to forward traffic coming from cisco through the Linux box. the rules i've set in the Linux box is described as follow: echo "1" /proc/sys/net/ipv4/ip_forward iptables -A INPUT -p 47 -j ACCEPT iptables -A FORWARD -i ppp0 -j ACCEPT iptables -A FORWARD -i pic -o ppp0 -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -i ppp0 -o pic -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE I see the traffic coming from tunnel and forwarded to internet but no reply from sent packet. May i miss something like a routing rule.

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  • Beeping Hard Disk - Seagate 250GB Momentus 5400.6

    - by Pez Cuckow
    I have been trying to repair a laptop that simply beeps instead of booting. After taking it apart I have now realised that it is the hard disk beeping. I know that may sound strange but I guarantee that is what it is! (Currently powered on it's own with a Sata Mains lead). The beeping is slightly faster than one per second there is a link to this recording. This recording was made resting the mic on the hard disk while it was sat on a table on it's own, there are no speakers anywhere near, the sound is coming from the hard disk. Does anyone know what this beep means? Is the hard drive just dead, or is it fixable and the data recoverable? Many thanks,

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  • Can fragments of a packet be refragmented again?

    - by gsinha
    In IPv4, fragmentation is done by routers on way to the destination if DF(do not fragment) flag is not set in the IP packet. Once a packet is fragmented, its fragments may take different paths (due to various reasons like topology changes) to the destination. If, on some link again in the path to destination, one routers find that the link MTU is smaller than the frame size, then either the packet needs to be fragmented or dropped. Can fragments of a packet be refragmented again? If yes, what will be the value of MF flag in the new individual fragments created by this?

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  • Can't copy files with 'additional permissions' to ext4 drive -- files that have @ after permissions,

    - by 99miles
    I am copying files from Snow Leopard to a mounted ext4 share via Samba, that's on a Fedora machine. Some files cannot be copied, and give this error: The operation can’t be completed because you don’t have permission to access some of the items. I've noticed that the files that can't be copied have an @ at the end of their permissions whien I do 'ls -l' in the command line. For example, I can copy the second file but not the first: -rwxrwxrwx@ 1 miles staff 1448 May 14 22:55 test.txt -rw-r--r-- 1 miles staff 136 Apr 5 17:06 image.psd.zip From what I've found, the @ means the file has 'additional properties'. Does anyone know how I can resolve this issue so I can copy the files to the fileshare?? Thanks!

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  • Make mysqldump output USE statements or full table names when dumping a single table with where clause

    - by tobyodavies
    Is it possible to get mysqldump to output USE statements for a single (partial) table dump? I've already got some scripts that I'd like to reuse which run mysqldump with some arguments and apply them to a remote server. However, since I haven't bothered to parse all the arguments to mysqldump, and there is no USE in the dump, the remote server is saying no database selected. I'm a programmer more than anything else, so I can easily use sed to modify the dump before applying it in the worst case, but those scripts won't allow me to do this as I don't have access to the dump between creation and application. EDIT: the ability to output fully qualified table names may also solve my problem

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  • Craftsmanship is ALL that Matters

    - by Wayne Molina
    Today, I'm going to talk about a touchy subject: the notion of working in a company that doesn't use the prescribed "best practices" in its software development endeavours.  Over the years I have, using a variety of pseudonyms, asked this question on popular programming forums.  Although I always add in some minor variation of the story to avoid suspicion that it's the same person posting, the crux of the tale remains the same: A Programmer’s Tale A junior software developer has just started a new job at an average company, creating average line-of-business applications for internal use (the most typical scenario programmers find themselves in).  This hypothetical newbie has spent a lot of time reading up on the "theory" of software development, devouring books, blogs and screencasts from well-known and respected software developers in the community in order to broaden his knowledge and "do what the pros do".  He begins his new job, eager to apply what he's learned on a real-world project only to discover that his new teammates doesn't use any of those concepts and techniques.  They hack their way through development, or in a best-case scenario use some homebrew, thrown-together semblance of a framework for their applications that follows not one of the best practices suggested by the “elite” in the software community - things like TDD (TDD as a "best practice" is the only subjective part of this post, but it's included here due to a very large following of respected developers who consider it one), the SOLID principles, well-known and venerable tools, even version control in a worst case and truly nightmarish scenario.  Our protagonist is frustrated that he isn't doing things the "proper" way - a way he's spent personal time digesting and learning about and, more importantly, a way that some of the top developers in the industry advocate - and turns to a forum to ask the advice of his peers. Invariably the answer I, in the guise of the concerned newbie, will receive is that A) I don't know anything and should just shut my mouth and sling code the bad way like everybody else on the team, and B) These "best practices" are fade or a joke, and the only thing that matters is shipping software to your customers. I am here today to say that anyone who says this, or anything like it, is not only full of crap but indicative of exactly the type of “developer” that has helped to give our industry a bad name.  Here is why: One Who Knows Nothing, Understands Nothing On one hand, you have the cognoscenti of the .NET development world.  Guys like James Avery, Jeremy Miller, Ayende Rahien and Rob Conery; all well-respected and noted programmers that are pretty much our version of celebrities.  These guys write blogs, books, and post videos outlining the "correct" way of writing software to make sure it not only works but is maintainable and extensible and a joy to work with.  They tout the virtues of the SOLID principles, or of using TDD/BDD, or using a mature ORM like NHibernate, Subsonic or even Entity Framework. On the other hand, you have Joe Everyman, Lead Software Developer at Initrode Corporation - in our hypothetical story Joe is the junior developer's new boss.  Joe's been with Initrode for 10 years, starting as the company’s very first programmer and over the years building up a little fiefdom of his own until at the present he’s in charge of all Initrode’s software development.  Joe writes code the same way he always has, without bothering to learn much, if anything.  He looked at NHibernate once and found it was "too hard", so he uses a primitive implementation of the TableDataGateway pattern as a wrapper around SqlClient.SqlConnection and SqlClient.SqlCommand instead of an actual ORM (or, in a better case scenario, has created his own ORM); the thought of using LINQ or Entity Framework or really anything other than his own hastily homebrew solution has never occurred to him.  He doesn't understand TDD and considers “testing” to be using the .NET debugger to step through code, or simply loading up an app and entering some values to see if it works.  He doesn't really understand SOLID, and he doesn't care to.  He's worked as a programmer for years, and that's all that counts.  Right?  WRONG. Who would you rather trust?  Someone with years of experience and who writes books, creates well-known software and is akin to a celebrity, or someone with no credibility outside their own minute environment who throws around their clout and company seniority as the "proof" of their ability?  Joe Everyman may have years of experience at Initrode as a programmer, and says to do things "his way" but someone like Jeremy Miller or Ayende Rahien have years of experience at companies just like Initrode, THEY know ten times more than Joe Everyman knows or could ever hope to know, and THEY say to do things "this way". Here's another way of thinking about it: If you wanted to get into politics and needed advice on the best way to do it, would you rather listen to the mayor of Hicktown, USA or Barack Obama?  One is a small-time nobody while the other is very well-known and, as such, would probably have much more accurate and beneficial advice. NOTE: The selection of Barack Obama as an example in no way, shape, or form suggests a political affiliation or political bent to this post or blog, and no political innuendo should be mistakenly read from it; the intent was merely to compare a small-time persona with a well-known persona in a non-software field.  Feel free to replace the name "Barack Obama" with any well-known Congressman, Senator or US President of your choice. DIY Considered Harmful I will say right now that the homebrew development environment is the WORST one for an aspiring programmer, because it relies on nothing outside it's own little box - no useful skill outside of the small pond.  If you are forced to use some half-baked, homebrew ORM created by your Director of Software, you are not learning anything valuable you can take with you in the future; now, if you plan to stay at Initrode for 10 years like Joe Everyman, this is fine and dandy.  However if, like most of us, you want to advance your career outside a very narrow space you will do more harm than good by sticking it out in an environment where you, to be frank, know better than everybody else because you are aware of alternative and, in almost most cases, better tools for the job.  A junior developer who understands why the SOLID principles are good to follow, or why TDD is beneficial, or who knows that it's better to use NHibernate/Subsonic/EF/LINQ/well-known ORM versus some in-house one knows better than a senior developer with 20 years experience who doesn't understand any of that, plain and simple.  Anyone who disagrees is either a liar, or someone who, just like Joe Everyman, Lead Developer, relies on seniority and tenure rather than adapting their knowledge as things evolve. In many cases, the Joe Everymans of the world act this way out of fear - they cannot possibly fathom that a “junior” could know more than them; after all, they’ve spent 10 or more years in the same company, doing the same job, cranking out the same shoddy software.  And here comes a newbie who hasn’t spent 10+ years doing the same things, with a fresh and often radical take on the craft, and Joe Everyman is afraid he might have to put some real effort into his career again instead of just pointing to his 10 years of service at Initrode as “proof” that he’s good, or that he might have to learn something new to improve; in most cases the problem is Joe Everyman, and by extension Initrode itself, has a mentality of just being “good enough”, and mediocrity is the rule of the day. A Thorn Bush is No Place for a Phoenix My advice is that if you work on a team where they don't use the best practices that some of the most famous developers in our field say is the "right" way to do things (and have legions of people who agree), and YOU are aware of these practices and can see why they work, then LEAVE the company.  Find a company where they DO care about quality, and craftsmanship, otherwise you will never be happy.  There is no point in "dumbing" yourself down to the level of your co-workers and slinging code without care to craftsmanship.  In 95% of these situations there will be no point in bringing it to the attention of Joe Everyman because he won't listen; he might even get upset that someone is trying to "upstage" him and fire the newbie, and replace someone with loads of untapped potential with a drone that will just nod affirmatively and grind out the tasks assigned without question. Find a company that has people smart enough to listen to the "best and brightest", and be happy.  Do not, I repeat, DO NOT waste away in a job working for ignorant people.  At the end of the day software development IS a craft, and a level of craftsmanship is REQUIRED for any serious professional.  When you have knowledgeable people with the credibility to back it up saying one thing, and small-time people who are, to put it bluntly, nobodies in the field saying and doing something totally different because they can't comprehend it, leave the nobodies to their own devices to fade into obscurity.  Work for a company that uses REAL software engineering techniques and really cares about craftsmanship.  The biggest issue affecting our career, and the reason software development has never been the respected, white-collar career it was meant to be, is because hacks and charlatans can pass themselves off as professional programmers without following a lick of good advice from programmers much better at the craft than they are.  These modern day snake-oil salesmen entrench themselves in companies by hoodwinking non-technical businesspeople and customers with their shoddy wares, end up in senior/lead/executive positions, and push their lack of knowledge on everybody unfortunate enough to work with/for/under them, crushing any dissent or voices of reason and change under their tyrannical heel and leaving behind a trail of dismayed and, often, unemployed junior developers who were made examples of to keep up the facade and avoid the shadow of doubt being cast upon them. To sum this up another way: If you surround yourself with learned people, you will learn.  Surround yourself with ignorant people who can't, as the saying goes, see the forest through the trees, and you'll learn nothing of any real value.  There is more to software development than just writing code, and the end goal should not be just "shipping software", it should be shipping software that is extensible, maintainable, and above all else software whose creation has broadened your knowledge in some capacity, even if a minor one.  An eager newbie who knows theory and thirsts for knowledge can easily be moulded and taught the advanced topics, but the same can't be said of someone who only cares about the finish line.  This industry needs more people espousing the benefits of software craftsmanship and proper software engineering techniques, and less Joe Everymans who are unwilling to adapt or foster new ways of thinking. Conclusion - I Cast “Protection from Fire” I am fairly certain this post will spark some controversy and might even invite the flames.  Please keep in mind these are opinions and nothing more.  A little healthy rant and subsequent flamewar can be good for the soul once in a while.  To paraphrase The Godfather: It helps to get rid of the bad blood.

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  • Generating a record of the full(-ish) package management state

    - by intuited
    I'm about to make some system changes and I'd like to have a record of my current happy system state. Is there a convenient way to create a record of this? I'd like to keep track of info like currently installed packages and their versions which packages are pinned at what version which source (as in /etc/apt/sources.list) they were installed from whether they were installed directly or automatically installed as a dependency of a different package "unknown unknowns": ie stuff that I don't know that I should be keeping track of but which may be important when trying to figure out why something doesn't work In short, I'd like to keep as much of the aptitude database as possible. What's the best way to do this? It would be nice if the resulting records were easily readable, though this is not really essential. It would be extra nice if it were readily versionable through an SCM tool like git. There is a superuser question that partially answers this, but it only provides the list of currently installed packages.

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  • Generating a record of the full(-ish) package management state

    - by intuited
    I'm about to make some system changes and I'd like to have a record of my current happy system state. Is there a convenient way to create a record of this? I'd like to keep track of info like currently installed packages and their versions which packages are pinned at what version which source (as in /etc/apt/sources.list) they were installed from whether they were installed directly or automatically installed as a dependency of a different package "unknown unknowns": ie stuff that I don't know that I should be keeping track of but which may be important when trying to figure out why something doesn't work In short, I'd like to keep as much of the aptitude database as possible. What's the best way to do this? It would be nice if the resulting records were easily readable, though this is not really essential. It would be extra nice if it were readily versionable through an SCM tool like git. There is a superuser question that partially answers this, but it only provides the list of currently installed packages.

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  • Windows XP cannot execute binary file on Network Share

    - by angerman
    I'm having a Network Share provided by a Mac OS X Lion Server on a recent Mac Mini Server (CIFS / SMB); mounting the share in Windows (XP) is no problem, reading and writing neither. But when ever I try to execute an executable .exe, Windows complains that it's not a valid win32 executable. Copying the file from the network share to the desktop or some other local location, allows the file to be subsequently executed. Pointers to what the root cause of this problem may be are greatly appreciated.

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  • Should a developer create test cases and then run through test cases

    - by Eben Roux
    I work for a company where the development manager expects a developer to create test cases before writing any code. These test cases have to then be maintained by the developers. Every-so-often a developer will be expected to run through the test cases. From this you should be able to gather that the company in question is rather small and there are no testers. Coming from a Software Architect position and having to write / execute test cases wearing my 'tester' hat is somewhat of a shock to the system. I do it anyway but it does seem to be a rather expensive exercise :) EDIT: I seem to need to elaborate here: I am not talking about unit-testing, TDD, etc. :) I am talking about that bit of testing a tester does. Once I have developed a system (with my unit tests / tdd / etc.) the software goes through a testing phase. Should a developer be that tester and developer those test cases? I think the misunderstanding may stem from the fact that developers, typically, are not involved with this type of testing and, therefore, assumed I am referring to that testing we do do: unit testing. But alas, no. I hope that clears it up.

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  • Archiving to Tape

    - by Bruno
    This is not about backups, this is about archiving. For arguments sake lets say I have 2TB 7z file that I would like to archive to tape. I have 4 LTO-5 tapes ( 1.5TB each ). This may be a stupid question but what set up would I need that would allow me to drag and drop those files directly onto those 2 tapes and would automatically split the file accross 2 tapes like so: ------------------ | Copy 1 | | 1.5TB | ------------------ ------------------ | Copy 1 | | 0.5TB | ------------------ ------------------ | Copy 2 | | 1.5TB | ------------------ ------------------ | Copy 2 | | 0.5TB | ------------------ I just want to be able to specify which files go on which tapes as oppose to backups where the tapes just rotate. Thanks.

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  • Performance Optimization &ndash; It Is Faster When You Can Measure It

    - by Alois Kraus
    Performance optimization in bigger systems is hard because the measured numbers can vary greatly depending on the measurement method of your choice. To measure execution timing of specific methods in your application you usually use Time Measurement Method Potential Pitfalls Stopwatch Most accurate method on recent processors. Internally it uses the RDTSC instruction. Since the counter is processor specific you can get greatly different values when your thread is scheduled to another core or the core goes into a power saving mode. But things do change luckily: Intel's Designer's vol3b, section 16.11.1 "16.11.1 Invariant TSC The time stamp counter in newer processors may support an enhancement, referred to as invariant TSC. Processor's support for invariant TSC is indicated by CPUID.80000007H:EDX[8]. The invariant TSC will run at a constant rate in all ACPI P-, C-. and T-states. This is the architectural behavior moving forward. On processors with invariant TSC support, the OS may use the TSC for wall clock timer services (instead of ACPI or HPET timers). TSC reads are much more efficient and do not incur the overhead associated with a ring transition or access to a platform resource." DateTime.Now Good but it has only a resolution of 16ms which can be not enough if you want more accuracy.   Reporting Method Potential Pitfalls Console.WriteLine Ok if not called too often. Debug.Print Are you really measuring performance with Debug Builds? Shame on you. Trace.WriteLine Better but you need to plug in some good output listener like a trace file. But be aware that the first time you call this method it will read your app.config and deserialize your system.diagnostics section which does also take time.   In general it is a good idea to use some tracing library which does measure the timing for you and you only need to decorate some methods with tracing so you can later verify if something has changed for the better or worse. In my previous article I did compare measuring performance with quantum mechanics. This analogy does work surprising well. When you measure a quantum system there is a lower limit how accurately you can measure something. The Heisenberg uncertainty relation does tell us that you cannot measure of a quantum system the impulse and location of a particle at the same time with infinite accuracy. For programmers the two variables are execution time and memory allocations. If you try to measure the timings of all methods in your application you will need to store them somewhere. The fastest storage space besides the CPU cache is the memory. But if your timing values do consume all available memory there is no memory left for the actual application to run. On the other hand if you try to record all memory allocations of your application you will also need to store the data somewhere. This will cost you memory and execution time. These constraints are always there and regardless how good the marketing of tool vendors for performance and memory profilers are: Any measurement will disturb the system in a non predictable way. Commercial tool vendors will tell you they do calculate this overhead and subtract it from the measured values to give you the most accurate values but in reality it is not entirely true. After falling into the trap to trust the profiler timings several times I have got into the habit to Measure with a profiler to get an idea where potential bottlenecks are. Measure again with tracing only the specific methods to check if this method is really worth optimizing. Optimize it Measure again. Be surprised that your optimization has made things worse. Think harder Implement something that really works. Measure again Finished! - Or look for the next bottleneck. Recently I have looked into issues with serialization performance. For serialization DataContractSerializer was used and I was not sure if XML is really the most optimal wire format. After looking around I have found protobuf-net which uses Googles Protocol Buffer format which is a compact binary serialization format. What is good for Google should be good for us. A small sample app to check out performance was a matter of minutes: using ProtoBuf; using System; using System.Diagnostics; using System.IO; using System.Reflection; using System.Runtime.Serialization; [DataContract, Serializable] class Data { [DataMember(Order=1)] public int IntValue { get; set; } [DataMember(Order = 2)] public string StringValue { get; set; } [DataMember(Order = 3)] public bool IsActivated { get; set; } [DataMember(Order = 4)] public BindingFlags Flags { get; set; } } class Program { static MemoryStream _Stream = new MemoryStream(); static MemoryStream Stream { get { _Stream.Position = 0; _Stream.SetLength(0); return _Stream; } } static void Main(string[] args) { DataContractSerializer ser = new DataContractSerializer(typeof(Data)); Data data = new Data { IntValue = 100, IsActivated = true, StringValue = "Hi this is a small string value to check if serialization does work as expected" }; var sw = Stopwatch.StartNew(); int Runs = 1000 * 1000; for (int i = 0; i < Runs; i++) { //ser.WriteObject(Stream, data); Serializer.Serialize<Data>(Stream, data); } sw.Stop(); Console.WriteLine("Did take {0:N0}ms for {1:N0} objects", sw.Elapsed.TotalMilliseconds, Runs); Console.ReadLine(); } } The results are indeed promising: Serializer Time in ms N objects protobuf-net   807 1000000 DataContract 4402 1000000 Nearly a factor 5 faster and a much more compact wire format. Lets use it! After switching over to protbuf-net the transfered wire data has dropped by a factor two (good) and the performance has worsened by nearly a factor two. How is that possible? We have measured it? Protobuf-net is much faster! As it turns out protobuf-net is faster but it has a cost: For the first time a type is de/serialized it does use some very smart code-gen which does not come for free. Lets try to measure this one by setting of our performance test app the Runs value not to one million but to 1. Serializer Time in ms N objects protobuf-net 85 1 DataContract 24 1 The code-gen overhead is significant and can take up to 200ms for more complex types. The break even point where the code-gen cost is amortized by its faster serialization performance is (assuming small objects) somewhere between 20.000-40.000 serialized objects. As it turned out my specific scenario involved about 100 types and 1000 serializations in total. That explains why the good old DataContractSerializer is not so easy to take out of business. The final approach I ended up was to reduce the number of types and to serialize primitive types via BinaryWriter directly which turned out to be a pretty good alternative. It sounded good until I measured again and found that my optimizations so far do not help much. After looking more deeper at the profiling data I did found that one of the 1000 calls did take 50% of the time. So how do I find out which call it was? Normal profilers do fail short at this discipline. A (totally undeserved) relatively unknown profiler is SpeedTrace which does unlike normal profilers create traces of your applications by instrumenting your IL code at runtime. This way you can look at the full call stack of the one slow serializer call to find out if this stack was something special. Unfortunately the call stack showed nothing special. But luckily I have my own tracing as well and I could see that the slow serializer call did happen during the serialization of a bool value. When you encounter after much analysis something unreasonable you cannot explain it then the chances are good that your thread was suspended by the garbage collector. If there is a problem with excessive GCs remains to be investigated but so far the serialization performance seems to be mostly ok.  When you do profile a complex system with many interconnected processes you can never be sure that the timings you just did measure are accurate at all. Some process might be hitting the disc slowing things down for all other processes for some seconds as well. There is a big difference between warm and cold startup. If you restart all processes you can basically forget the first run because of the OS disc cache, JIT and GCs make the measured timings very flexible. When you are in need of a random number generator you should measure cold startup times of a sufficiently complex system. After the first run you can try again getting different and much lower numbers. Now try again at least two times to get some feeling how stable the numbers are. Oh and try to do the same thing the next day. It might be that the bottleneck you found yesterday is gone today. Thanks to GC and other random stuff it can become pretty hard to find stuff worth optimizing if no big bottlenecks except bloatloads of code are left anymore. When I have found a spot worth optimizing I do make the code changes and do measure again to check if something has changed. If it has got slower and I am certain that my change should have made it faster I can blame the GC again. The thing is that if you optimize stuff and you allocate less objects the GC times will shift to some other location. If you are unlucky it will make your faster working code slower because you see now GCs at times where none were before. This is where the stuff does get really tricky. A safe escape hatch is to create a repro of the slow code in an isolated application so you can change things fast in a reliable manner. Then the normal profilers do also start working again. As Vance Morrison does point out it is much more complex to profile a system against the wall clock compared to optimize for CPU time. The reason is that for wall clock time analysis you need to understand how your system does work and which threads (if you have not one but perhaps 20) are causing a visible delay to the end user and which threads can wait a long time without affecting the user experience at all. Next time: Commercial profiler shootout.

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  • Adding an Admin user to an ASP.NET MVC 4 application using a single drop-in file

    - by Jon Galloway
    I'm working on an ASP.NET MVC 4 tutorial and wanted to set it up so just dropping a file in App_Start would create a user named "Owner" and assign them to the "Administrator" role (more explanation at the end if you're interested). There are reasons why this wouldn't fit into most application scenarios: It's not efficient, as it checks for (and creates, if necessary) the user every time the app starts up The username, password, and role name are hardcoded in the app (although they could be pulled from config) Automatically creating an administrative account in code (without user interaction) could lead to obvious security issues if the user isn't informed However, with some modifications it might be more broadly useful - e.g. creating a test user with limited privileges, ensuring a required account isn't accidentally deleted, or - as in my case - setting up an account for demonstration or tutorial purposes. Challenge #1: Running on startup without requiring the user to install or configure anything I wanted to see if this could be done just by having the user drop a file into the App_Start folder and go. No copying code into Global.asax.cs, no installing addition NuGet packages, etc. That may not be the best approach - perhaps a NuGet package with a dependency on WebActivator would be better - but I wanted to see if this was possible and see if it offered the best experience. Fortunately ASP.NET 4 and later provide a PreApplicationStartMethod attribute which allows you to register a method which will run when the application starts up. You drop this attribute in your application and give it two parameters: a method name and the type that contains it. I created a static class named PreApplicationTasks with a static method named, then dropped this attribute in it: [assembly: PreApplicationStartMethod(typeof(PreApplicationTasks), "Initializer")] That's it. One small gotcha: the namespace can be a problem with assembly attributes. I decided my class didn't need a namespace. Challenge #2: Only one PreApplicationStartMethod per assembly In .NET 4, the PreApplicationStartMethod is marked as AllMultiple=false, so you can only have one PreApplicationStartMethod per assembly. This was fixed in .NET 4.5, as noted by Jon Skeet, so you can have as many PreApplicationStartMethods as you want (allowing you to keep your users waiting for the application to start indefinitely!). The WebActivator NuGet package solves the multiple instance problem if you're in .NET 4 - it registers as a PreApplicationStartMethod, then calls any methods you've indicated using [assembly: WebActivator.PreApplicationStartMethod(type, method)]. David Ebbo blogged about that here:  Light up your NuGets with startup code and WebActivator. In my scenario (bootstrapping a beginner level tutorial) I decided not to worry about this and stick with PreApplicationStartMethod. Challenge #3: PreApplicationStartMethod kicks in before configuration has been read This is by design, as Phil explains. It allows you to make changes that need to happen very early in the pipeline, well before Application_Start. That's fine in some cases, but it caused me problems when trying to add users, since the Membership Provider configuration hadn't yet been read - I got an exception stating that "Default Membership Provider could not be found." The solution here is to run code that requires configuration in a PostApplicationStart method. But how to do that? Challenge #4: Getting PostApplicationStartMethod without requiring WebActivator The WebActivator NuGet package, among other things, provides a PostApplicationStartMethod attribute. That's generally how I'd recommend running code that needs to happen after Application_Start: [assembly: WebActivator.PostApplicationStartMethod(typeof(TestLibrary.MyStartupCode), "CallMeAfterAppStart")] This works well, but I wanted to see if this would be possible without WebActivator. Hmm. Well, wait a minute - WebActivator works in .NET 4, so clearly it's registering and calling PostApplicationStartup tasks somehow. Off to the source code! Sure enough, there's even a handy comment in ActivationManager.cs which shows where PostApplicationStartup tasks are being registered: public static void Run() { if (!_hasInited) { RunPreStartMethods(); // Register our module to handle any Post Start methods. But outside of ASP.NET, just run them now if (HostingEnvironment.IsHosted) { Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleUtility.RegisterModule(typeof(StartMethodCallingModule)); } else { RunPostStartMethods(); } _hasInited = true; } } Excellent. Hey, that DynamicModuleUtility seems familiar... Sure enough, K. Scott Allen mentioned it on his blog last year. This is really slick - a PreApplicationStartMethod can register a new HttpModule in code. Modules are run right after application startup, so that's a perfect time to do any startup stuff that requires configuration to be read. As K. Scott says, it's this easy: using System; using System.Web; using Microsoft.Web.Infrastructure.DynamicModuleHelper; [assembly:PreApplicationStartMethod(typeof(MyAppStart), "Start")] public class CoolModule : IHttpModule { // implementation not important // imagine something cool here } public static class MyAppStart { public static void Start() { DynamicModuleUtility.RegisterModule(typeof(CoolModule)); } } Challenge #5: Cooperating with SimpleMembership The ASP.NET MVC Internet template includes SimpleMembership. SimpleMembership is a big improvement over traditional ASP.NET Membership. For one thing, rather than forcing a database schema, it can work with your database schema. In the MVC 4 Internet template case, it uses Entity Framework Code First to define the user model. SimpleMembership bootstrap includes a call to InitializeDatabaseConnection, and I want to play nice with that. There's a new [InitializeSimpleMembership] attribute on the AccountController, which calls \Filters\InitializeSimpleMembershipAttribute.cs::OnActionExecuting(). That comment in that method that says "Ensure ASP.NET Simple Membership is initialized only once per app start" which sounds like good advice. I figured the best thing would be to call that directly: new Mvc4SampleApplication.Filters.InitializeSimpleMembershipAttribute().OnActionExecuting(null); I'm not 100% happy with this - in fact, it's my least favorite part of this solution. There are two problems - first, directly calling a method on a filter, while legal, seems odd. Worse, though, the Filter lives in the application's namespace, which means that this code no longer works well as a generic drop-in. The simplest workaround would be to duplicate the relevant SimpleMembership initialization code into my startup code, but I'd rather not. I'm interested in your suggestions here. Challenge #6: Module Init methods are called more than once When debugging, I noticed (and remembered) that the Init method may be called more than once per page request - it's run once per instance in the app pool, and an individual page request can cause multiple resource requests to the server. While SimpleMembership does have internal checks to prevent duplicate user or role entries, I'd rather not cause or handle those exceptions. So here's the standard single-use lock in the Module's init method: void IHttpModule.Init(HttpApplication context) { lock (lockObject) { if (!initialized) { //Do stuff } initialized = true; } } Putting it all together With all of that out of the way, here's the code I came up with: using Mvc4SampleApplication.Filters; using System.Web; using System.Web.Security; using WebMatrix.WebData; [assembly: PreApplicationStartMethod(typeof(PreApplicationTasks), "Initializer")] public static class PreApplicationTasks { public static void Initializer() { Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleUtility .RegisterModule(typeof(UserInitializationModule)); } } public class UserInitializationModule : IHttpModule { private static bool initialized; private static object lockObject = new object(); private const string _username = "Owner"; private const string _password = "p@ssword123"; private const string _role = "Administrator"; void IHttpModule.Init(HttpApplication context) { lock (lockObject) { if (!initialized) { new InitializeSimpleMembershipAttribute().OnActionExecuting(null); if (!WebSecurity.UserExists(_username)) WebSecurity.CreateUserAndAccount(_username, _password); if (!Roles.RoleExists(_role)) Roles.CreateRole(_role); if (!Roles.IsUserInRole(_username, _role)) Roles.AddUserToRole(_username, _role); } initialized = true; } } void IHttpModule.Dispose() { } } The Verdict: Is this a good thing? Maybe. I think you'll agree that the journey was undoubtedly worthwhile, as it took us through some of the finer points of hooking into application startup, integrating with membership, and understanding why the WebActivator NuGet package is so useful Will I use this in the tutorial? I'm leaning towards no - I think a NuGet package with a dependency on WebActivator might work better: It's a little more clear what's going on Installing a NuGet package might be a little less error prone than copying a file A novice user could uninstall the package when complete It's a good introduction to NuGet, which is a good thing for beginners to see This code either requires either duplicating a little code from that filter or modifying the file to use the namespace Honestly I'm undecided at this point, but I'm glad that I can weigh the options. If you're interested: Why are you doing this? I'm updating the MVC Music Store tutorial to ASP.NET MVC 4, taking advantage of a lot of new ASP.NET MVC 4 features and trying to simplify areas that are giving people trouble. One change that addresses both needs us using the new OAuth support for membership as much as possible - it's a great new feature from an application perspective, and we get a fair amount of beginners struggling with setting up membership on a variety of database and development setups, which is a distraction from the focus of the tutorial - learning ASP.NET MVC. Side note: Thanks to some great help from Rick Anderson, we had a draft of the tutorial that was looking pretty good earlier this summer, but there were enough changes in ASP.NET MVC 4 all the way up to RTM that there's still some work to be done. It's high priority and should be out very soon. The one issue I ran into with OAuth is that we still need an Administrative user who can edit the store's inventory. I thought about a number of solutions for that - making the first user to register the admin, or the first user to use the username "Administrator" is assigned to the Administrator role - but they both ended up requiring extra code; also, I worried that people would use that code without understanding it or thinking about whether it was a good fit.

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  • Problem closing MDI child window in Terminal Services/Remote Desktop Connection 7.0

    - by Justin Love
    I have one user whose computer just got updated to the 7.0 Remote Desktop Connection. Concurrently, she has started having a problem closing the MDI child windows in an old FoxPro application running on the remote server. We have two different servers, both 2003, running the same application, one locally and one at a remote office. Only the remote office server is giving trouble. It works fine for me, even when logging into her TS account. No other users have complained. The other day the same user experienced an error message (path not found for a path showing a localization placeholder) starting the RDC, fixed by reboot. I suspect she may have had RDC running during the 7.0 upgrade.

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  • July, the 31 Days of SQL Server DMO’s – Day 20 (sys.dm_tran_locks)

    - by Tamarick Hill
    The sys.dm_tran_locks DMV is used to return active lock resources on your server. Locking is a mechanism used by SQL Server to protect the integrity of data when you have multiple users that may potentially access the same data at the same time. Let’s run a query against this DMV so we can analyze the results. SELECT * FROM sys.dm_tran_locks As we can see, its a lot of lock information returned from this DMV. I will not go into detail about each of the columns returned, but I will touch on the ones that I feel are the most important. The first column in the output is the resource_type column which tells you the type of lock a particular row represents. It could be a PAGE lock, RID, OBJECT, DATABASE, or several other lock types. The resource_database_id represents the id of the database for a particular lock resource. The resource_lock_partition column represents the ID of a lock partition. When you have a table that is partitioned, locks can be escalated to the partition level before going to a table level lock. The request_mode column gives us information about the type of lock that is being requested. From the screenshots above we see RangeS-S locks which represent a share range lock and IS locks which represent Intent Shared locks. The request_status column displays whether the lock has been granted or whether the lock is waiting to be acquired. The request_session_id  shows the session_id that is requesting the lock. This DMV is the best place to go when you need to identify the exact locks that are being held or pending for individual requests. You might need this information when you are troubleshooting severe blocking or deadlocking problems on your server. For more information on this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms190345.aspx Follow me on Twitter @PrimeTimeDBA

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  • What is the best way to build a database from a MS Word document?

    - by Jayron Soares
    Please advise me on how to approach this problem: I have a sequential list of metadata in a document in MS Word. The basic idea is to create a Python algorithm to iterate over the information, retrieving just the name of the PROCESS, when is made a queue, from a database. Example metadata: Process: Process Walker (1965) Exact reference: Walker Process Equipment., Inc. v. Food Machinery Corp. Link: http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=382&invol= Type of procedure: Certiorari to the United States Court of Appeals for the Seventh Circuit. Parties: Walker Process Equipment, Inc. Sector: Systems is ... Start Date: October 12-13 Arguedas, 1965 Summary: Food Machinery Company has initiated a process to stop or slow the entry of competitors through the use of a patent obtained by fraud. The case concerned a patent on "knee action swing diffusers" used in aeration equipment for sewage treatment systems, and the question was whether "the maintenance and enforcement of a patent obtained by fraud before the patent office" may be a basis for antitrust punishment. Report of the evolution process: petitioner, in answer to respond... Importance: a) First case which established an analysis for the diagnosis of dispute… There are about 200 pages containing the information above. I have in mind the idea of implementing an algorithm in Python to be able to break this information sequence and try to store it in a web database (an open source application that I’m looking for) in order to allow for free consultations.

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  • How did I get here? My route to Android, iPhone, Windows Phone 7, and interest in Mobile Devices

    - by Wallym
    I get asked all the time how/why I got interested in mobile and jumped on this fairly early.  I tend to give half answers because it wasn't just one thing that took me to mobile, but a whole host of separate ivents culminating in a specific event where I wasdoing market research in May/June 2008.  Let me throw out the events and the facts about me: I tend to like new, different, cool stuff.  I jumped on .NET early on.  I jumped on Ajax early on.  I don't jump on every new technology that comes down the road, I'm probably the only person on the planet that doesn't "get" MVC, though I acknowledge that a lot of people do and it solves a number of problems in the default settings of ASP.NET WebForms. I remember buying an early Windows CE device. It was interesting, but dang, this stylus thing sucks. After I lost my third stylus, i just gave up.  I got my first mobile phone in early 1999.  Reception was crappy, but I could see the value in being mobile. In 1999, I worked on a manufacturing systems project.  One piece of the projects was a set of handheld devices on the shop floor.  While the UI was a crappy DOS based, yes I said DOS as in Disk Operating System Version 6.22, I could see that the wireless world was a direction I wanted to be in. In 2000, Microsoft released the first public alpha of .NET.  Very cool stuff indeed.  One piece of the puzzle was a set of mobile controls for ASP.NET.  I build numerous test apps as well as mobile version using these mobile controls.  Now, the mobile UIs of the time were based on WML, which was crap. I could real all the analysis of mobile and read all about growth rates.  Now, you have to realize that growth rates can be impressive when dealing with small numbers, but I knew it was a comer. In our first book, I got talked out of mobile because of the line from the publisher "Wally, mobile doesn't sell." Blackberry was the dominant device of the mid 2000s.  Its users were referred to as "Crackberry addicts."  Unfortunately, the mobile development experience for native apps was crap and the web experience was fairly rough as well, but if they could get the ecosystem started, other phones and better blackberryies would come out.  I finally jumped into using a blackberry. Sometime around 2006, I heard "Wally, mobile doesn't sell" again.  Now, anyone that knows me knows that someone saying something like this to me means I'll keep trying it. The phones of the mid 2000s were moving to be more graphical, but there were too many that had this idea that they had to use a stylus.  Stylus suck.  They get lost too easily. I worked on a project in 2007 and 2008 for a startup trying to answer the question of "What is there to do where I am at?"  For some reason, they wanted to be tied to PCs.  As it became obvious that they were having problems, their investor asked us to do some market research and to figure out what the marketplace did want.  One of the important things that I figured out was the we lived in a mobile world and if you had a mobile app, it need to be on a mobile device, not tied to a desktop/laptop/netbook device.  If there was any single event, this was it - I was doing some market research and sat and talked to people in a bar/restaurant in Atlanta called "The Grove" on Lavista.  The consensus of the people that I talked to was that they wanted their data where ever they were at, laptop, pc, mobile, whereever. In 2007, Apple released the iPhone.  Wow, what an impressive device, even with all the problems of a 1st generation device.  I bought an iPod Touch 1st generation to understand touch better, one of the best decisions I ever made. I decided in late 2008, to make a move into cloud, for a number of reasons.  I was working on an example app.  In April, 2009, one of my friends at Microsoft said "don't mention my name with this, but you need an iPhone front end for this app."  How do you get on the iPhone.  Well, there are a number of ways including: ObjectiveC.  Its hard to teach an old dog new tricks, and this dog knows .NET, not ObjectiveC. HTML, web, javascript optimized interface.  yeah, this is possible. PhoneGap.  Now, this is interesting, take an html interface and get it to run on the iPhone, Android, Blackberry, and other platforms.  I thought that this way made the most sense for me until......... MonoTouch.  In May/June 2009, Novell announced a way for .NET/c# developers to write apps for the iPhone.  This is the way that made the most sense to me. Titanium by Appcelerator.  This is similar in concept to PhoneGap.  I haven't played with this much but do want to learn more about it. In July, 2009, I emailed one of my contacts at Wrox to see if they would be interested in a short MonoTouch ebook in their Wrox Blox format.  I fully expected another  response along the lines of "Wally, mobile doesn't sell."  The response I got was "Wally, iPhone is H O T, get started immediately, can you have this to me before Labor Day."  Not quite the response I expected.  Thankfully, we didn't make the Labor Day, first draft date. I kept pushing back because I had a feeling that things were not going to be quite as polished and feature rich as necessary.  After all, Novell doesn't have the resouces of Microsoft's developer division. The ebook shipped on November 30, 2009. On about December, 15, 2009, my editor emailed and said "Your ebook is selling really well, lets do a full book and it by March 1 so get started."  Thankfully, guys like Craig Dunn and Chris Hardy were interested along with Martin and Ror joinged us later on. I bought my wife an iPhone 3Gs in early 2010 to go along with all my iPod Touch devices. I tried to pretend in 2010 that I wasn't that interested in mobile and still had interest in the desktop technologies.  I love the technologies and continue to use them today, but that isn't where my interest is right now.  I'm just about all mobile all the time with my energies.  Our book shipped in the beginning of July, 2010 right in the middle of the Apple FUD.I've been looking at Mobile Web as a way around the AppStores and Apple FUD problems of 2010. With all the Apple self FUD, we became interested in Android.I went up to Dino Esposito at DevConnections in Las Vegas at introduced myself. I've always tried to keep up with what Dino has been doing. I was shocked, he wanted to meet me.  We must have talked for 1.5 hours. It was way more time than I deserved. If you get a chance, go and introduce yourself to Dino. He's a great guy. Microsoft released Windows Phone 7 in the Fall of 2010.  I'm not doing development on that platform at this time.  I think they have a very interesting user interface.  The devices are being positively reviewed.  For my purposes, the devices are limited at this point in time.  We'll see what 2011 brings as far as updates to the operating system.  I need multitasking/background processing and html5 in the browser. Add that as well as acceptance in the marketplace and I'll be more interested in the device. Obviosuly, I'm now working on a MonoDroid book . I own Android and iPhone/iOS devices.  I am currently working on some startup ideas and am exploring as much in that area as I can. For 2011, I'm planning on speaking at Android Developer's Conference (AnDevCon) and Mobile Connections.  I'm really excited about this. I have a couple of magazine articles coming out in 2011 on Android and iPhone development with the Mono technologies.is Mono "The Answer"? What's "The Question?" I think it will work for me.  It might work for you, it might not.  it depends on your situation.  Its the current horse that I am riding. I might find a better horse tomorrow. So, that's how I got here.  I'm in love with mobile.  Mobile native apps on the device as well as mobile web.  I'm into all this cool stuff.  Where are you at?

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  • WinXP How to Tunnel LPT over USB

    - by Michael Pruitt
    I have a windows program that accesses a device connected to a LPT (1-3) 25 pin port. The communication is bidirectional, and I suspected the control lines are also accessed directly. I would like to migrate the device to a machine that does not have a LPT port. I saw the dos2usb software, but that takes the output (from a DOS program) and 'prints' it formatted for a specific printer. I need a raw LPT connection, and a cable that provides access to all the control signals. I do have a USB to 36-pin Centronics that may have the extra signals. I use it with a vinyl cutter that doesn't like most of the USB dongles. It comes up as USB001. Would adding and sharing a generic printer, then mapping LPT1 to the share get me closer? Would that work for a parallel port scanner? My preferred solution is a USB cable with a driver that will map it to LPT1, LPT2, or LPT3.

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  • Bash vs. Gnu screen : Replace Ctrl-A with Ctrl-Shift-A

    - by Stefan Lasiewski
    I'm a new user to GNU Screen. I've been using Bash for a very long time, and I want to give GNU Screen a try. As you know, GNU Screen uses 'C-a' (Control-A) as as the command character. Trouble is, this interferes with the Line Editing feature in Bash (and GNU Readline), because Control-A in Bash will Move to the start of the line." I know I can set the Command Character to another key sequence, like "^Q" or "``" (Backtick), but I have trouble finding another key sequence which isn't already in use (^Q is used by the terminal, backtick is used when writing shell scripts). It appears that the Command Character may only be one or two characters in length. Can I set the GNU Screen control character to be something like "Control-Shift-A"? (I can't use more then one hyperlink yet, so I cannot link to the Bash documentation)

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  • VLOOKUP in Excel, part 2: Using VLOOKUP without a database

    - by Mark Virtue
    In a recent article, we introduced the Excel function called VLOOKUP and explained how it could be used to retrieve information from a database into a cell in a local worksheet.  In that article we mentioned that there were two uses for VLOOKUP, and only one of them dealt with querying databases.  In this article, the second and final in the VLOOKUP series, we examine this other, lesser known use for the VLOOKUP function. If you haven’t already done so, please read the first VLOOKUP article – this article will assume that many of the concepts explained in that article are already known to the reader. When working with databases, VLOOKUP is passed a “unique identifier” that serves to identify which data record we wish to find in the database (e.g. a product code or customer ID).  This unique identifier must exist in the database, otherwise VLOOKUP returns us an error.  In this article, we will examine a way of using VLOOKUP where the identifier doesn’t need to exist in the database at all.  It’s almost as if VLOOKUP can adopt a “near enough is good enough” approach to returning the data we’re looking for.  In certain circumstances, this is exactly what we need. We will illustrate this article with a real-world example – that of calculating the commissions that are generated on a set of sales figures.  We will start with a very simple scenario, and then progressively make it more complex, until the only rational solution to the problem is to use VLOOKUP.  The initial scenario in our fictitious company works like this:  If a salesperson creates more than $30,000 worth of sales in a given year, the commission they earn on those sales is 30%.  Otherwise their commission is only 20%.  So far this is a pretty simple worksheet: To use this worksheet, the salesperson enters their sales figures in cell B1, and the formula in cell B2 calculates the correct commission rate they are entitled to receive, which is used in cell B3 to calculate the total commission that the salesperson is owed (which is a simple multiplication of B1 and B2). The cell B2 contains the only interesting part of this worksheet – the formula for deciding which commission rate to use: the one below the threshold of $30,000, or the one above the threshold.  This formula makes use of the Excel function called IF.  For those readers that are not familiar with IF, it works like this: IF(condition,value if true,value if false) Where the condition is an expression that evaluates to either true or false.  In the example above, the condition is the expression B1<B5, which can be read as “Is B1 less than B5?”, or, put another way, “Are the total sales less than the threshold”.  If the answer to this question is “yes” (true), then we use the value if true parameter of the function, namely B6 in this case – the commission rate if the sales total was below the threshold.  If the answer to the question is “no” (false), then we use the value if false parameter of the function, namely B7 in this case – the commission rate if the sales total was above the threshold. As you can see, using a sales total of $20,000 gives us a commission rate of 20% in cell B2.  If we enter a value of $40,000, we get a different commission rate: So our spreadsheet is working. Let’s make it more complex.  Let’s introduce a second threshold:  If the salesperson earns more than $40,000, then their commission rate increases to 40%: Easy enough to understand in the real world, but in cell B2 our formula is getting more complex.  If you look closely at the formula, you’ll see that the third parameter of the original IF function (the value if false) is now an entire IF function in its own right.  This is called a nested function (a function within a function).  It’s perfectly valid in Excel (it even works!), but it’s harder to read and understand. We’re not going to go into the nuts and bolts of how and why this works, nor will we examine the nuances of nested functions.  This is a tutorial on VLOOKUP, not on Excel in general. Anyway, it gets worse!  What about when we decide that if they earn more than $50,000 then they’re entitled to 50% commission, and if they earn more than $60,000 then they’re entitled to 60% commission? Now the formula in cell B2, while correct, has become virtually unreadable.  No-one should have to write formulae where the functions are nested four levels deep!  Surely there must be a simpler way? There certainly is.  VLOOKUP to the rescue! Let’s redesign the worksheet a bit.  We’ll keep all the same figures, but organize it in a new way, a more tabular way: Take a moment and verify for yourself that the new Rate Table works exactly the same as the series of thresholds above. Conceptually, what we’re about to do is use VLOOKUP to look up the salesperson’s sales total (from B1) in the rate table and return to us the corresponding commission rate.  Note that the salesperson may have indeed created sales that are not one of the five values in the rate table ($0, $30,000, $40,000, $50,000 or $60,000).  They may have created sales of $34,988.  It’s important to note that $34,988 does not appear in the rate table.  Let’s see if VLOOKUP can solve our problem anyway… We select cell B2 (the location we want to put our formula), and then insert the VLOOKUP function from the Formulas tab: The Function Arguments box for VLOOKUP appears.  We fill in the arguments (parameters) one by one, starting with the Lookup_value, which is, in this case, the sales total from cell B1.  We place the cursor in the Lookup_value field and then click once on cell B1: Next we need to specify to VLOOKUP what table to lookup this data in.  In this example, it’s the rate table, of course.  We place the cursor in the Table_array field, and then highlight the entire rate table – excluding the headings: Next we must specify which column in the table contains the information we want our formula to return to us.  In this case we want the commission rate, which is found in the second column in the table, so we therefore enter a 2 into the Col_index_num field: Finally we enter a value in the Range_lookup field. Important:  It is the use of this field that differentiates the two ways of using VLOOKUP.  To use VLOOKUP with a database, this final parameter, Range_lookup, must always be set to FALSE, but with this other use of VLOOKUP, we must either leave it blank or enter a value of TRUE.  When using VLOOKUP, it is vital that you make the correct choice for this final parameter. To be explicit, we will enter a value of true in the Range_lookup field.  It would also be fine to leave it blank, as this is the default value: We have completed all the parameters.  We now click the OK button, and Excel builds our VLOOKUP formula for us: If we experiment with a few different sales total amounts, we can satisfy ourselves that the formula is working. Conclusion In the “database” version of VLOOKUP, where the Range_lookup parameter is FALSE, the value passed in the first parameter (Lookup_value) must be present in the database.  In other words, we’re looking for an exact match. But in this other use of VLOOKUP, we are not necessarily looking for an exact match.  In this case, “near enough is good enough”.  But what do we mean by “near enough”?  Let’s use an example:  When searching for a commission rate on a sales total of $34,988, our VLOOKUP formula will return us a value of 30%, which is the correct answer.  Why did it choose the row in the table containing 30% ?  What, in fact, does “near enough” mean in this case?  Let’s be precise: When Range_lookup is set to TRUE (or omitted), VLOOKUP will look in column 1 and match the highest value that is not greater than the Lookup_value parameter. It’s also important to note that for this system to work, the table must be sorted in ascending order on column 1! If you would like to practice with VLOOKUP, the sample file illustrated in this article can be downloaded from here. Similar Articles Productive Geek Tips Using VLOOKUP in ExcelImport Microsoft Access Data Into ExcelImport an Access Database into ExcelCopy a Group of Cells in Excel 2007 to the Clipboard as an ImageShare Access Data with Excel in Office 2010 TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Quickly Schedule Meetings With NeedtoMeet Share Flickr Photos On Facebook Automatically Are You Blocked On Gtalk? Find out Discover Latest Android Apps On AppBrain The Ultimate Guide For YouTube Lovers Will it Blend? iPad Edition

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  • How do you deal with translating theory into practice?

    - by Mr. Shickadance
    Hello all! Being a computer scientist in a research field I am often tasked with working alongside professionals outside of the software domain (think math people, electrical engineer etc), and then translating their theories and ideas into real-world implementations. I often find it difficult when they present a theoretical problem which appears to be somewhat disconnected from reality. I am not saying that the theory is bogus, only that it is difficult to translate into real-world situations. For example, recently I have been working with software defined radios. We are exploring many different areas, but often the math specialists in my group would present a problem which is heavily grounded in theory (signal processing, physics, whatever). I often struggle at times where it is hard to draw direct parallels between the theory and the real-world implementation that I need to develop. Say we are working on an energy detector, the theory person in my group would say "you need to measure the noise variance with no signal present." This leads me to think "how the hell do I isolate noise from a signal in reality?" There are many examples, but I hope you see where I am going. So, my question is how does one deal with implementation of theoretical concepts when the theory seems detached from reality? Or at least when the connections are not so clear. Or perhaps, the person with the 'theory' may be ignorant of real restrictions? Note: I found this to be a hard question to ask - hopefully you are following me. If you have suggestions on how I could improve it, by all means let me know! Thanks for looking! EDIT: To be a bit more clear, I understand in situations like this that I must learn that specific domain myself to an extent (i.e. signal processing), but I am more concerned with when those theoretical concepts do not appear to be as grounded in practice as one would like.

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  • The fastest way to resize images from ASP.NET. And it’s (more) supported-ish.

    - by Bertrand Le Roy
    I’ve shown before how to resize images using GDI, which is fairly common but is explicitly unsupported because we know of very real problems that this can cause. Still, many sites still use that method because those problems are fairly rare, and because most people assume it’s the only way to get the job done. Plus, it works in medium trust. More recently, I’ve shown how you can use WPF APIs to do the same thing and get JPEG thumbnails, only 2.5 times faster than GDI (even now that GDI really ultimately uses WIC to read and write images). The boost in performance is great, but it comes at a cost, that you may or may not care about: it won’t work in medium trust. It’s also just as unsupported as the GDI option. What I want to show today is how to use the Windows Imaging Components from ASP.NET APIs directly, without going through WPF. The approach has the great advantage that it’s been tested and proven to scale very well. The WIC team tells me you should be able to call support and get answers if you hit problems. Caveats exist though. First, this is using interop, so until a signed wrapper sits in the GAC, it will require full trust. Second, the APIs have a very strong smell of native code and are definitely not .NET-friendly. And finally, the most serious problem is that older versions of Windows don’t offer MTA support for image decoding. MTA support is only available on Windows 7, Vista and Windows Server 2008. But on 2003 and XP, you’ll only get STA support. that means that the thread safety that we so badly need for server applications is not guaranteed on those operating systems. To make it work, you’d have to spin specialized threads yourself and manage the lifetime of your objects, which is outside the scope of this article. We’ll assume that we’re fine with al this and that we’re running on 7 or 2008 under full trust. Be warned that the code that follows is not simple or very readable. This is definitely not the easiest way to resize an image in .NET. Wrapping native APIs such as WIC in a managed wrapper is never easy, but fortunately we won’t have to: the WIC team already did it for us and released the results under MS-PL. The InteropServices folder, which contains the wrappers we need, is in the WicCop project but I’ve also included it in the sample that you can download from the link at the end of the article. In order to produce a thumbnail, we first have to obtain a decoding frame object that WIC can use. Like with WPF, that object will contain the command to decode a frame from the source image but won’t do the actual decoding until necessary. Getting the frame is done by reading the image bytes through a special WIC stream that you can obtain from a factory object that we’re going to reuse for lots of other tasks: var photo = File.ReadAllBytes(photoPath); var factory = (IWICComponentFactory)new WICImagingFactory(); var inputStream = factory.CreateStream(); inputStream.InitializeFromMemory(photo, (uint)photo.Length); var decoder = factory.CreateDecoderFromStream( inputStream, null, WICDecodeOptions.WICDecodeMetadataCacheOnLoad); var frame = decoder.GetFrame(0); We can read the dimensions of the frame using the following (somewhat ugly) code: uint width, height; frame.GetSize(out width, out height); This enables us to compute the dimensions of the thumbnail, as I’ve shown in previous articles. We now need to prepare the output stream for the thumbnail. WIC requires a special kind of stream, IStream (not implemented by System.IO.Stream) and doesn’t directlyunderstand .NET streams. It does provide a number of implementations but not exactly what we need here. We need to output to memory because we’ll want to persist the same bytes to the response stream and to a local file for caching. The memory-bound version of IStream requires a fixed-length buffer but we won’t know the length of the buffer before we resize. To solve that problem, I’ve built a derived class from MemoryStream that also implements IStream. The implementation is not very complicated, it just delegates the IStream methods to the base class, but it involves some native pointer manipulation. Once we have a stream, we need to build the encoder for the output format, which could be anything that WIC supports. For web thumbnails, our only reasonable options are PNG and JPEG. I explored PNG because it’s a lossless format, and because WIC does support PNG compression. That compression is not very efficient though and JPEG offers good quality with much smaller file sizes. On the web, it matters. I found the best PNG compression option (adaptive) to give files that are about twice as big as 100%-quality JPEG (an absurd setting), 4.5 times bigger than 95%-quality JPEG and 7 times larger than 85%-quality JPEG, which is more than acceptable quality. As a consequence, we’ll use JPEG. The JPEG encoder can be prepared as follows: var encoder = factory.CreateEncoder( Consts.GUID_ContainerFormatJpeg, null); encoder.Initialize(outputStream, WICBitmapEncoderCacheOption.WICBitmapEncoderNoCache); The next operation is to create the output frame: IWICBitmapFrameEncode outputFrame; var arg = new IPropertyBag2[1]; encoder.CreateNewFrame(out outputFrame, arg); Notice that we are passing in a property bag. This is where we’re going to specify our only parameter for encoding, the JPEG quality setting: var propBag = arg[0]; var propertyBagOption = new PROPBAG2[1]; propertyBagOption[0].pstrName = "ImageQuality"; propBag.Write(1, propertyBagOption, new object[] { 0.85F }); outputFrame.Initialize(propBag); We can then set the resolution for the thumbnail to be 96, something we weren’t able to do with WPF and had to hack around: outputFrame.SetResolution(96, 96); Next, we set the size of the output frame and create a scaler from the input frame and the computed dimensions of the target thumbnail: outputFrame.SetSize(thumbWidth, thumbHeight); var scaler = factory.CreateBitmapScaler(); scaler.Initialize(frame, thumbWidth, thumbHeight, WICBitmapInterpolationMode.WICBitmapInterpolationModeFant); The scaler is using the Fant method, which I think is the best looking one even if it seems a little softer than cubic (zoomed here to better show the defects): Cubic Fant Linear Nearest neighbor We can write the source image to the output frame through the scaler: outputFrame.WriteSource(scaler, new WICRect { X = 0, Y = 0, Width = (int)thumbWidth, Height = (int)thumbHeight }); And finally we commit the pipeline that we built and get the byte array for the thumbnail out of our memory stream: outputFrame.Commit(); encoder.Commit(); var outputArray = outputStream.ToArray(); outputStream.Close(); That byte array can then be sent to the output stream and to the cache file. Once we’ve gone through this exercise, it’s only natural to wonder whether it was worth the trouble. I ran this method, as well as GDI and WPF resizing over thirty twelve megapixel images for JPEG qualities between 70% and 100% and measured the file size and time to resize. Here are the results: Size of resized images   Time to resize thirty 12 megapixel images Not much to see on the size graph: sizes from WPF and WIC are equivalent, which is hardly surprising as WPF calls into WIC. There is just an anomaly for 75% for WPF that I noted in my previous article and that disappears when using WIC directly. But overall, using WPF or WIC over GDI represents a slight win in file size. The time to resize is more interesting. WPF and WIC get similar times although WIC seems to always be a little faster. Not surprising considering WPF is using WIC. The margin of error on this results is probably fairly close to the time difference. As we already knew, the time to resize does not depend on the quality level, only the size does. This means that the only decision you have to make here is size versus visual quality. This third approach to server-side image resizing on ASP.NET seems to converge on the fastest possible one. We have marginally better performance than WPF, but with some additional peace of mind that this approach is sanctioned for server-side usage by the Windows Imaging team. It still doesn’t work in medium trust. That is a problem and shows the way for future server-friendly managed wrappers around WIC. The sample code for this article can be downloaded from: http://weblogs.asp.net/blogs/bleroy/Samples/WicResize.zip The benchmark code can be found here (you’ll need to add your own images to the Images directory and then add those to the project, with content and copy if newer in the properties of the files in the solution explorer): http://weblogs.asp.net/blogs/bleroy/Samples/WicWpfGdiImageResizeBenchmark.zip WIC tools can be downloaded from: http://code.msdn.microsoft.com/wictools To conclude, here are some of the resized thumbnails at 85% fant:

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