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• Is It Worth It To Learn Experimental Languages

  - by Xander Lamkins

  I'm a young programmer who desires to work in the field someday as a programmer. I know Java, VB.NET and C#. I want to learn a new language (as I programmer, I know that it is valuable to extend what I know - to learn languages that make you think differently). I took a look online to see what languages were common. Everybody knows C and C++ (even those muggles who know so little about computers in general), so I thought, maybe I should push for C. C and C++ are nice but they are old. Things like Haskell and Forth (etc. etc. etc.) are old and have lost their popularity. I'm scared of learning C (or even C++) for this same reason. Java is pretty old as well and is slow because it's run by the JVM and not compiled to native code. I've been a Windows developer for quite a while. I recently started using Java - but only because it was more versatile and spreadable to other places. The problem is that it doesn't look like a very usable language for these reasons: It's most used purpose is for web application and cellphone apps (specifically Android) As far as actual products made with it, the only things that come to mind are Netbeans, Eclipse (hurrah for making and IDE with the language the IDE is for - it's like making a webpage for writing HTML/CSS/Javascript), and Minecraft which happens to be fun but laggy and bipolar as far as computer spec. support. Other than that it's used for servers but heck - I don't only want to make/configure servers. The .NET languages are nice, however: People laugh if I even mention VB.NET or C# in a serious conversation. It isn't cross-platform unless you use MONO (which is still in development and has some improvements to be made). Lacks low level stuff because, like Java with the JVM, it is run/managed by the CLR. My first thought was learning something like C and then using it to springboard into C++ (just to make sure I would have a strong understanding/base), but like I said earlier, it's getting older and older by the minute. What I've Looked Into Fantom looks nice. It's like a nice middleman between my two favorite languages and even lets me publish between the two interchangeably, but, unlike what I want, it compiles to the CLR or JVM (depending on what you publish it to) instead of it being a complete compile. D also looks nice. It seems like a very usable language and from multiple sources it appears to actually be better than C/C++. I would jump right with it, but I'm still unsure of its success because it obviously isn't very mainstream at this point. There are a couple others that looked pretty nice that focused on other things such as Opa with web development and Go by GOOGLE. My Question Is it worth learning these "experimental" languages? I've read other questions that say that if you aren't constantly learning languages and open to all languages that you aren't in the right mindset for programming. I understand this and I still might not quite be getting it, but in truth, if a language isn't going to become mainstream, should I spend my time learning something else? I don't want to learn old (or any going to soon be old) programming languages. I know that many people see this as something important, *but would any of you ever actually consider (assuming you didn't already know) FORTRAN? My goal is to stay current to make sure I'm successful in the future. Disclaimer Yes, I am a young programmer, so I probably made a lot of naive statements in my question. Feel free to correct me on ANYTHING! I have to start learning somewhere so I'm sure a lot of my knowledge is sketchy enough to have caused to incorrect statements or flaws in my thinking. Please leave any feelings you have in the comments.

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• Is it worth to learn Experimental Languages?

  - by Xander Lamkins

  I'm a young programmer who desires to work in the field someday as a programmer. I know Java, VB.NET and C#. I want to learn a new language (as I programmer, I know that it is valuable to extend what I know - to learn languages that make you think differently). I took a look online to see what languages were common. Everybody knows C and C++ (even those muggles who know so little about computers in general), so I thought, maybe I should push for C. C and C++ are nice but they are old. Things like Haskell and Forth (etc. etc. etc.) are old and have lost their popularity. I'm scared of learning C (or even C++) for this same reason. Java is pretty old as well and is slow because it's run by the JVM and not compiled to native code. I've been a Windows developer for quite a while. I recently started using Java - but only because it was more versatile and spreadable to other places. The problem is that it doesn't look like a very usable language for these reasons: It's most used purpose is for web application and cellphone apps (specifically Android) As far as actual products made with it, the only things that come to mind are Netbeans, Eclipse (hurrah for making and IDE with the language the IDE is for - it's like making a webpage for writing HTML/CSS/Javascript), and Minecraft which happens to be fun but laggy and bipolar as far as computer spec. support. Other than that it's used for servers but heck - I don't only want to make/configure servers. The .NET languages are nice, however: People laugh if I even mention VB.NET or C# in a serious conversation. It isn't cross-platform unless you use MONO (which is still in development and has some improvements to be made). Lacks low level stuff because, like Java with the JVM, it is run/managed by the CLR. My first thought was learning something like C and then using it to springboard into C++ (just to make sure I would have a strong understanding/base), but like I said earlier, it's getting older and older by the minute. What I've Looked Into Fantom looks nice. It's like a nice middleman between my two favorite languages and even lets me publish between the two interchangeably, but, unlike what I want, it compiles to the CLR or JVM (depending on what you publish it to) instead of it being a complete compile. D also looks nice. It seems like a very usable language and from multiple sources it appears to actually be better than C/C++. I would jump right with it, but I'm still unsure of its success because it obviously isn't very mainstream at this point. There are a couple others that looked pretty nice that focused on other things such as Opa with web development and Go by GOOGLE. My Question Is it worth learning these "experimental" languages? I've read other questions that say that if you aren't constantly learning languages and open to all languages that you aren't in the right mindset for programming. I understand this and I still might not quite be getting it, but in truth, if a language isn't going to become mainstream, should I spend my time learning something else? I don't want to learn old (or any going to soon be old) programming languages. I know that many people see this as something important, *but would any of you ever actually consider (assuming you didn't already know) FORTRAN? My goal is to stay current to make sure I'm successful in the future. Disclaimer Yes, I am a young programmer, so I probably made a lot of naive statements in my question. Feel free to correct me on ANYTHING! I have to start learning somewhere so I'm sure a lot of my knowledge is sketchy enough to have caused to incorrect statements or flaws in my thinking. Please leave any feelings you have in the comments.

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• Best approach to depth streaming via existing codec

  - by Kevin

  I'm working on a development system (and game) intended for games set mostly in static third-person views. We produce our scenery by CG and photographic techniques. Our background art is rendered off-line by a production-grade renderer. To allow the runtime imagery to properly interact with the background art, I wrote a program to convert from depth output by Mental Ray into a texture, and a pixel shader to draw a quad such that the Z data comes from the texture. This technique is working out very well, but now we've decided that some of the camera angle changes between scenes should be animated. The animation itself is straightforward to produce from our CG models. We intend to encode it to some HD video codec such as H.264. The problem is that in order to maintain our runtime imagery on the screen, the depth buffer will need to be loaded for each video frame. Due to the bandwidth, the video's depth data will need to be compressed efficiently. I've looked into methods for performing temporal compression of depth info and found an interesting research paper here: http://web4.cs.ucl.ac.uk/staff/j.kautz/publications/depth-streaming.pdf The method establishes a mapping between 16-bit depth values and YCbCr values. The mapping is tuned to the properties of existing video codecs in order to maximize precision of the decoded depths after the YCbCr has undergone video compression. It allows an existing, unmodified video codec to be used on the backend. I'm looking at how to pull this off with the least possible work. (This design change was unplanned.) Our game engine itself is native C++, presently for Win32 and DirectX, although we've worked hard to keep platform dependence segregated because we intend other ports. We don't have motion video facilities in the engine yet but will ultimately need that anyway for cinematics. I was planning on using some off-the-shelf motion video solution we can plug into our engine, and haven't chosen one yet. This new added requirement makes selecting one harder since, among other things, we'll now need to bypass colourspace conversion on one of the streams, and also will need to be playing two streams simultaneously in lockstep, on top of in some cases audio on one of them (for the cinematics). I'm also wondering if it's possible (or even useful) to do the conversion from YCbCr to depth in a pixel shader, or if it's better to just do it in CPU and separately load the resulting depth values into a locked tex. The conversion unfortunately does involve branching logic per-pixel. (There are more naive mappings that don't need branching, but they produce inferior results.) It could be reduced to a table lookup but the table would be 32MB. Programming is second-nature to me but I'm not that experienced with pix shaders and have zero knowledge of off-the-shelf video solutions. I'd therefore be interested in advice from others who may have dealt more with depth streaming, pixel shaders, and/or off-the-shelf codecs, regarding how feasible the proposed application is and what off-the-shelf video systems out there would best get along with this usage case.

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• Libgdx 2D Game, Random generated World of random size, how to get mouse coordinates?

  - by Solom

  I'm a noob and English is not my mothertongue, so please bear with me! I'm generating a map for a Sidescroller out of a 2D-array. That is, the array holds different values and I create blocks based on that value. Now, my problem is to match mouse coordinates on screen with the actual block the mouse is pointing at. public class GameScreen implements Screen { private static final int WIDTH = 100; private static final int HEIGHT = 70; private OrthographicCamera camera; private Rectangle glViewport; private Spritebatch spriteBatch; private Map map; private Block block; ... @Override public void show() { camera = new OrthographicCamera(WIDTH, HEIGHT); camera.position.set(WIDTH/2, HEIGHT/2, 0); glViewport = new Rectangle(0, 0, WIDTH, HEIGHT); map = new Map(16384, 256); map.printTileMap(); // Debugging only spriteBatch = new SpriteBatch(); } @Override public void render(float delta) { // Clear previous frame Gdx.gl.glClearColor(1, 1, 1, 1 ); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); GL30 gl = Gdx.graphics.getGL30(); // gl.glViewport((int) glViewport.x, (int) glViewport.y, (int) glViewport.width, (int) glViewport.height); spriteBatch.setProjectionMatrix(camera.combined); camera.update(); spriteBatch.begin(); // Draw Map this.drawMap(); // spriteBatch.flush(); spriteBatch.end(); } private void drawMap() { for(int a = 0; a < map.getHeight(); a++) { // Bounds check (y) if(camera.position.y + camera.viewportHeight < a)// || camera.position.y - camera.viewportHeight > a) break; for(int b = 0; b < map.getWidth(); b++) { // Bounds check (x) if(camera.position.x + camera.viewportWidth < b)// || camera.position.x > b) break; // Dynamic rendering via BlockManager int id = map.getTileMap()[a][b]; Block block = BlockManager.map.get(id); if(block != null) // Check if Air { block.setPosition(b, a); spriteBatch.draw(block.getTexture(), b, a, 1 ,1); } } } } As you can see, I don't use the viewport anywhere. Not sure if I need it somewhere down the road. So, the map is 16384 blocks wide. One block is 16 pixels in size. One of my naive approaches was this: if(Gdx.input.isButtonPressed(Input.Buttons.LEFT)) { Vector3 mousePos = new Vector3(); mousePos.set(Gdx.input.getX(), Gdx.input.getY(), 0); camera.unproject(mousePos); System.out.println(Math.round(mousePos.x)); // *16); // Debugging // TODO: round // map.getTileMap()[mousePos.x][mousePos.y] = 2; // Draw at mouse position } I confused myself somewhere down the road I fear. What I want to do is, update the "block" (or rather the information in the Map/2D-Array) so that in the next render() there is another block. Basically drawing on the spriteBatch g So if anyone could point me in the right direction this would be highly appreciated. Thanks!

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• Approach for packing 2D shapes while minimizing total enclosing area

  - by Dennis

  Not sure on my tags for this question, but in short .... I need to solve a problem of packing industrial parts into crates while minimizing total containing area. These parts are motors, or pumps, or custom-made components, and they have quite unusual shapes. For some, it may be possible to assume that a part === rectangular cuboid, but some are not so simple, i.e. they assume a shape more of that of a hammer or letter T. With those, (assuming 2D shape), by alternating direction of top & bottom, one can pack more objects into the same space, than if all tops were in the same direction. Crude example below with letter "T"-shaped parts: ***** xxxxx ***** x ***** *** ooo * x vs * x vs * x vs * x o * x * xxxxx * x * x o xxxxx xxx Right now we are solving the problem by something like this: using CAD software, make actual models of how things fit in crate boxes make estimates of actual crate dimensions & write them into Excel file (1) is crazy amount of work and as the result we have just a limited amount of possible entries in (2), the Excel file. The good things is that programming this is relatively easy. Given a combination of products to go into crates, we do a lookup, and if entry exists in the Excel (or Database), we bring it out. If it doesn't, we say "sorry, no data!". I don't necessarily want to go full force on making up some crazy algorithm that given geometrical part description can align, rotate, and figure out best part packing into a crate, given its shape, but maybe I do.. Question Well, here is my question: assuming that I can represent my parts as 2D (to be determined how), and that some parts look like letter T, and some parts look like rectangles, which algorithm can I use to give me a good estimate on the dimensions of the encompassing area, while ensuring that the parts are packed in a minimal possible area, to minimize crating/shipping costs? Are there approximation algorithms? Seeing how this can get complex, is there an existing library I could use? My thought / Approach My naive approach would be to define a way to describe position of parts, and place the first part, compute total enclosing area & dimensions. Then place 2nd part in 0 degree orientation, repeat, place it at 180 degree orientation, repeat (for my case I don't think 90 degree rotations will be meaningful due to long lengths of parts). Proceed using brute force "tacking on" other parts to the enclosing area until all parts are processed. I may have to shift some parts a tad (see 3rd pictorial example above with letters T). This adds a layer of 2D complexity rather than 1D. I am not sure how to approach this. One idea I have is genetic algorithms, but I think those will take up too much processing power and time. I will need to look out for shape collisions, as well as adding extra padding space, since we are talking about real parts with irregularities rather than perfect imaginary blocks. I'm afraid this can get geometrically messy fairly fast, and I'd rather keep things simple, if I can. But what if the best (practical) solution is to pack things into different crate boxes rather than just one? This can get a bit more tricky. There is human element involved as well, i.e. like parts can go into same box and are thus a constraint to be considered. Some parts that are not the same are sometimes grouped together for shipping and can be considered as a common grouped item. Sometimes customers want things shipped their way, which adds human element to constraints. so there will have to be some customization.

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• Ideal backup appliance for backup software like Bacula?

  - by Ricket

  I'm at a small company and we (the IT department of two) manage <100 client computers and a handful of servers. Currently we're using a company's appliance to handle backup; it does a small backup every night and a full backup every weekend, and a guy comes on Wednesday to take an offsite backup drive (and gives back last week's drive to swap with it). The backup is done only on the servers' hard drives, because our client computers and employees make sure not to store anything worthwhile on their own computers. So it's a pretty simple situation. Lately this system, mainly the appliance, has been having problems, so we are looking for an alternative. I'm researching other companies but also looking into what we might expect from trying to do this ourselves. There will undoubtedly be a large learning curve, but hey, that's what serverfault is for, right? :) So anyway I was looking at Bacula. Feature list sounds great, documentation is plentiful, but it's only software. So my question is, what is the ideal backup server to run the Bacula server software on? And not only the server but other related appliances. Our current backup appliance uses only hard drives, not tape drives. It has several plugged into it at one time, in hotswap bays on the front of the machine. I couldn't help but notice though, it's hardly more than Windows XP with hard drive bays, a PCI eSATA card (which connects to another appliance extension piece with 2 more bays), and their software. Since the company will take back their appliance if/when we cancel with them, where can I go to configure a server with these kinds of things? And should I consider switching to tape drives? What other concerns should I be thinking about when I pick out hardware for a backup server? Maybe I'm being naive, I'm sure Dell (and any other computer company) sells them in the small business section of their website, but I wanted to make sure that there's not some other more recommended place that other companies are getting their hardware from, and that I don't need anything special for Bacula.

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• Benchmarking hosting providers IO with Bonnie

  - by Derek Organ

  Ok, because of a bunch of projects I'm working on I've access to dedicated Servers on a 3 hosting providers. As an experiment and for educational purposes I decided to see if I could benchmark how good the IO is with each. Bit of research lead me to Bonnie++ So I installed it on the server and ran this simple command /usr/sbin/bonnie -d /tmp/foo The 3 machines in different hosting providers are all dedicated machines, one is a VPS, other two are on some cloud platform e.g. VMWare / Xen using some kind of clustered SAN for storage This might be a naive thing to do but here are the results I found. HOST A Version 1.03c ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP xxxxxxxxxxxxxxxx 1G 45081 88 56244 14 19167 4 20965 40 67110 6 67.2 0 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 15264 28 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ xxxxxxxx,1G,45081,88,56244,14,19167,4,20965,40,67110,6,67.2,0,16,15264,28,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++ HOST B Version 1.03d ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP xxxxxxxxxxxx 4G 43070 91 64510 15 19092 0 29276 47 39169 0 448.2 0 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 24799 52 +++++ +++ +++++ +++ 25443 54 +++++ +++ +++++ +++ xxxxxxx,4G,43070,91,64510,15,19092,0,29276,47,39169,0,448.2,0,16,24799,52,+++++,+++,+++++,+++,25443,54,+++++,+++,+++++,+++ HOST C Version 1.03c ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP xxxxxxxxxxxxx 1536M 15598 22 85698 13 258969 20 16194 22 723655 21 +++++ +++ ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 14142 22 +++++ +++ 18621 22 13544 22 +++++ +++ 17363 21 xxxxxxxx,1536M,15598,22,85698,13,258969,20,16194,22,723655,21,+++++,+++,16,14142,22,+++++,+++,18621,22,13544,22,+++++,+++,17363,21 Ok, so first off what is the best way to read the figures and are there any issues with really comparing these numbers? Is this in any way a true representation of IO Speed? If not is there any way for me to test that? Note: these 3 machines are using either Ubuntu or Debian (I presume that doesn't really matter)

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• Nameserver not resolving or domain not pingable [closed]

  - by Ricky

  Sorry, if anyone can think of a better title please change it! I want to host my own websites from home. For testing purposes, I have a virtual machine running a trial version of Windows Server 2008 Enterprise. Note I currently run a VPS and host my own websites but due to a nice speed upgrade on our line I now want to host from home. I have several domains but I wanted to test with one, that is rickyoleary.com. Our ISP does not provide static IP addresses unless we have a business account so I've been looking at no-ip.com. I admit my networking isn't the best, hence this question but I've been bashing my head all day on this one. I created a host name, muffinbubble.no-ip.org which runs on IP: 86.148.124.15. I've setup IIS on the server with a simple test page. I've then forwarded port 80 traffic from the router and from what I can see, it's working. If I access my website (I was unable to link to this for some reason so please copy and paste this) - http://86.148.124.15/ - I see my test page. So the next step was to create my nameservers. This domain is with namecheap.com so I created my nameservers, ns1.rickyoleary.com and ns2.rickyoleary.com. Both these point to the same IP (and yes, that will be changed after testing), the same IP as above: 86.148.124.15. On the server itself I have set up DNS entries as below which I believe to be correct and added rickyoleary.com and www.rickyoleary.com in the host headers (or bindings) in IIS 7.0. If I try and look up my domain, rickyoleary.com it shows ns1.rickyoleary.com and ns2.rickyoleary.com as the nameservers. I then tried to use just-ping.com on my nameserver ns1.rickyoleary.com. I get 100% packets lost, but the correct IP address is returned (I'm guessing the router does not allow pings, but is still accessible...). I get no response when pinging rickyoleary.com. Here's the problems: I cannot ping ns1.rickyoleary.com or ns2.rickyoleary.com from a command prompt. I'm not sure if this is an issue. When I added the nameservers in Windows Server 2008 and clicked 'resolve' a message box displays stating "No such host is known". I cannot ping rickyoleary.com. rickyoleary.com is not showing my test page on my server. Now - please note, I've waited around 6 hours for propagation. From my experience, although you're told to wait 24 - 48 hours, the changes are normally pretty quick so perhaps I'm being impatient or naive to think it should all be working fine until then. I would really appreciate some help here. Thanks.

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• How to correctly partition usb flash drive and which filesystem to choose considering wear leveling?

  - by random1

  Two problems. First one: how to partition the flash drive? I shouldn't need to do this, but I'm no longer sure if my partition is properly aligned since I was forced to delete and create a new partition table after gparted complained when I tried to format the drive from FAT to ext4. The naive answer would be to say "just use default and everything is going to be alright". However if you read the following links you'll know things are not that simple: https://lwn.net/Articles/428584/ and http://linux-howto-guide.blogspot.com/2009/10/increase-usb-flash-drive-write-speed.html Then there is also the issue of cylinders, heads and sectors. Currently I get this: $sfdisk -l -uM /dev/sdd Disk /dev/sdd: 30147 cylinders, 64 heads, 32 sectors/track Warning: The partition table looks like it was made for C/H/S=*/255/63 (instead of 30147/64/32). For this listing I'll assume that geometry. Units = mebibytes of 1048576 bytes, blocks of 1024 bytes, counting from 0 Device Boot Start End MiB #blocks Id System /dev/sdd1 1 30146 30146 30869504 83 Linux $fdisk -l /dev/sdd Disk /dev/sdd: 31.6 GB, 31611420672 bytes 255 heads, 63 sectors/track, 3843 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00010c28 So from my current understanding I should align partitions at 4 MiB (currently it's at 1 MiB). But I still don't know how to set the heads and sectors properly for my device. Second problem: file system. From the benchmarks I saw ext4 provides the best performance, however there is the issue of wear leveling. How can I know that my Transcend JetFlash 700's microcontroller provides for wear leveling? Or will I just be killing my drive faster? I've seen a lot of posts on the web saying don't worry the newer drives already take care of that. But I've never seen a single piece of backed evidence of that and at some point people start mixing SSD with USB flash drives technology. The safe option would be to go for ext2, however a serious of tests that I performed showed horrible performance!!! These values are from a real scenario and not some synthetic test: 42 files: 3,429,415,284 bytes copied to flash drive original fat32: 15.1 MiB/s ext4 after new partition table: 10.2 MiB/s ext2 after new partition table: 1.9 MiB/s Please read the links that I posted above before answering. I would also be interested in answers backed up with some references because a lot is said and re-said but then it lacks facts. Thank you for the help.

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• Using Amazon S3 for multiple remote data site uploads, securely

  - by Aitch

  I've been playing about with Amazon S3 a little for the first time and like what I see for various reasons relating to my potential use case. We have multiple (online) remote server boxes harvesting sensor data that is regularly uploaded every hour or so (rsync'ed) to a VPS server. The number of remote server boxes is growing regularly and forecast to keep growing (hundreds). The servers are geographically dispersed. The servers are also automatically built, therefore generic with standard tools and not bespoke per location. The data is many hundreds of files per day. I want to avoid a situation where I need to provision more VPS storage, or additional servers every time we hit the VPS capacity limit, after every N server deployments, whatever N might be. The remote servers can never be considered fully secure due to us not knowing what might happen to them when we are not looking. Our current solution is a bit naive and simply restricts inbound rsync only over ssh to known mac address directories and a known public key. There are plenty of holes to pick in this, I know. Let's say I write or use a script like s3cmd/s3sync to potentially push up the files. Would I need to manage hundreds of access keys and have each server customized to include this (do-able, but key management becomes nightmarish?) Could I restrict inbound connections somehow (eg by mac address), or just allow write-only to any client that was running the script? ( i could deal with a flood of data if someone got into a system? ) having a bucket per remote machine does not seem feasible due to bucket limits? I don't think I want to use a single common key as if one machine is breached then potentially, a malicious hack could get access to the filestore key and start deleting for ll clients, correct? I hope my inexperience has not blinded me to some other solution that might be suggested! I've read lots of examples of people using S3 for backup, but can't really find anything about this sort of data collection, unless my google terminology is wrong... I've written more than I should here, perhaps it can be summarised thus: In a perfect world I just want to have one of our techs install a new remote server into a location and it automagically starts sending files home with little or no intervention, and minimises risk? Pipedream or feasible? TIA, Aitch

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• Thunderbird 3: can't change column width?

  - by rumtscho

  I recently installed Thunderbird 3.0.3. Just noticed a suboptimal UI setting: in the upper pane, which lists the e-mails in the current folder, the Date column is about 200px wide. So when I keep the window at 480x600, all I see in a row is: | tree icon | favourites icon | attachment icon | read icon | junk icon | Date and time, followed by 5cm whitespace | ... | P Where "P" is the first letter of the name of the sender. And the "..." is actually shown this way, I have no idea which column it is meant to be. But I don't see neither the sender, nor the message subject, which makes scrolling a folder for a certain mail rather pointless. I see these when I maximize the window, actually the columns are then not only bigger, they are arranged in another sequence. But I feel that holding a mail client permanently maximised at 1600x1200 is a waste of screen real estate. My naive solution attempt was to try to go with the mouse cursor to the right edge of the date column and try to shrink it by moving the cursor left while holding down the left mouse button. Not only is this default behaviour for all resizable columns I've ever encountered in GUIs, the cursor actually turns into a horizontal double-headed arrow. But pulling has no effect at all. I cannot make a wide column narrow, and I cannot make the narrow columns wide. I didn't find anything in the preferences either. So can please somebody explain how to get the columns arranged sensibly? Edit: I found out that I only have the problem when I drag the Thunderbird window to a GridMove screen area. It gets automatically resized, but doesn't notice the resize event or something, so the column width remains the same as under a maximized window. First making the window narrow using the mouse helps with column width, but the width of the mail pane is still too wide (rows don't reflow). Anyway, this seems to be a bug caused by the combination of the two applications and not a configuration problem, so I guess I'll have to live with it.

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• open source knowledge base CMS system

  - by Thomi

  I'm looking for an open source knowledge base system that uses tags, rather than free-text search to identify articles (a lot like serverfault does). I've looked at twiki, which many people suggested, but haven't found what I'm looking for. Basically I want to be able to create and tag articles, and provide an easy way for anonymous users to search based on tags. Edit: OK, here's some more detail regarding what I want. Basically, all the knowledge base systems I have seen so far are a collection of articles, each article with a title. Most of them allow you to categorise articles into groups and sub-groups. Users of the system can search for information using a title search, for example "How do I print from AwesomeProduct?" - which then shows a list of any articles that match that search text. This is fine and dandy when your KB is for one version of the software product (the mythical AwesomeProduct ver 1.0). However, the development team then go ahead and create a new version (ver 2.0) that adds many new features and changes some existing features. Now, how do we support both products in the same KB? The Naive method is to copy all articles from 1.0, and update them for 2.0, adding and removing articles in 2.0 as required. We can then add text at the top of every 1.0 article that says: "this articles applies to 1.0 only, to see the 2.0 version, click here" (or something similar) The problem with articles being indexed in the system by title is that it's very hard to filter based on meta-data like version. What happens when we create version 3.0 or 4.0? The end-situation here is that you have a mess of articles. They're hard to search, hard to filter, and even harder to manage. The solution (it seems to me) is to use tags, rather than text as the article index mechanism. So articles can be tagged with a tag representing the software version, topic area etc. etc. Users can then filter based on tag - an example search might be "version_1 printing" - which straight away gives a list of articles with all these tags. So that's what I'm looking for - a KB system that uses tags, rather than text to index many articles. I'm sure I could build something with drupal, but I was hoping for something that worked out-of-the-box.

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• How do Windows 7 encrypted files look like?

  - by Sean Farrell

  Ok this is kind of an odd question: How do Windows 7 (Home Premium) encrypted files look like "from the outside"? Now here is the story. An acquaintance of a freind of mine got a nasty virus / scareware. So I wiped out my PC technician cap and went to work on it. What I did was remove the drive from the laptop and put drive into my external drive bay. I scanned the drive and yes it was loaded with stuff. That basically cured the infection and I could start the system back up. To check if it cured the problem I wanted to see the system while running. There where two user accounts, on with a password and one without (both admin users !?!). So I logged into the unprotected user and cleaned up the residual issues, like proxy server to localhost in the browser config. Now I wanted to do the same for the password protected user. What I noticed that from my system and the unprotected user account the files of the protected user looked garbled. The files are something like 12 random alphanum chars, but the folders looked ok. Naive as was thought this might be how encrypted files looked "from the outside". (I never use Microsoft's own security features, so how would I know. TrueCrypt is one big blob.) Since the second user could not be reached, I though sod it and removed the password from the account. (That might have been a mistake, I know.) Now I did the same clean up tasks and all nice and fine; except for the files which where still "encrypted". So I looked into many Windows Encrypted Files recovery posts and not all hope is lost, since I should be able to extract the certificate and with the password regain access to the files. Also note that windows did "only" prompt me that removing the password would be insecure, not that access to encrypted files would be lost, like it is claimed in most recovery articles. Resetting the password did not help and I gave up for the night. The question that nagged me half of the last night was, what if the files are not encrypted, but the scare-ware encrypted / destroyed the files? I don't want to spend hours of work trying to recover files that are not recoverable. The ting is that the user does not remember turning it on and aren't the files marked in blue and the filename is readable? Many thanks for input from users who have more knowledge about WEF...

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• SQL SERVER – Weekly Series – Memory Lane – #005

  - by pinaldave

  Here is the list of curetted articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 SQL SERVER – Cursor to Kill All Process in Database I indeed wrote this cursor and when I often look back, I wonder how naive I was to write this. The reason for writing this cursor was to free up my database from any existing connection so I can do database operation. This worked fine but there can be a potentially big issue if there was any important transaction was killed by this process. There is another way to to achieve the same thing where we can use ALTER syntax to take database in single user mode. Read more about that over here and here. 2007 Rules of Third Normal Form and Normalization Advantage – 3NF The rules of 3NF are mentioned here Make a separate table for each set of related attributes, and give each table a primary key. If an attribute depends on only part of a multi-valued key, remove it to a separate table If attributes do not contribute to a description of the key, remove them to a separate table. Correct Syntax for Stored Procedure SP Sometime a simple question is the most important question. I often see in industry incorrectly written Stored Procedure. Few writes code after the most outer BEGIN…END and few writes code after the GO Statement. In this brief blog post, I have attempted to explain the same. 2008 Switch Between Result Pan and Query Pan – SQL Shortcut Many times when I am writing query I have to scroll the result displayed in the result set. Most of the developer uses the mouse to switch between and Query Pane and Result Pane. There are few developers who are crazy about Keyboard shortcuts. F6 is the keyword which can be used to switch between query pane and tabs of the result pane. Interesting Observation – Use of Index and Execution Plan Query Optimization is a complex game and it has its own rules. From the example in the article we have discovered that Query Optimizer does not use clustered index to retrieve data, sometime non clustered index provides optimal performance for retrieving Primary Key. When all the rows and columns are selected Primary Key should be used to select data as it provides optimal performance. 2009 Interesting Observation – TOP 100 PERCENT and ORDER BY If you pull up any application or system where there are more than 100 SQL Server Views are created – I am very confident that at one or two places you will notice the scenario wherein View the ORDER BY clause is used with TOP 100 PERCENT. SQL Server 2008 VIEW with ORDER BY clause does not throw an error; moreover, it does not acknowledge the presence of it as well. In this article we have taken three perfect examples and demonstrated which clause we should use when. Comma Separated Values (CSV) from Table Column A Very common question – How to create comma separated values from a table in the database? The answer is also very common if we use XML. Check out this article for quick learning on the same subject. Azure Start Guide – Step by Step Installation Guide Though Azure portal has changed a quite bit since I wrote this article, the concept used in this article are not old. They are still valid and many of the functions are still working as mentioned in the article. I believe this one article will put you on the track to use Azure! Size of Index Table for Each Index – Solution Earlier I have posted a small question on this blog and requested help from readers to participate here and provide a solution. The puzzle was to write a query that will return the size for each index that is on any particular table. We need a query that will return an additional column in the above listed query and it should contain the size of the index. This article presents two of the best solutions from the puzzle. 2010 Well, this week in 2010 was the week of puzzles as I posted three interesting puzzles. Till today I am noticing pretty good interesting in the puzzles. They are tricky but for sure brings a great value if you are a database developer for a long time. I suggest you go over this puzzles and their answers. Did you really know all of the answers? I am confident that reading following three blog post will for sure help you enhance the experience with T-SQL. SQL SERVER – Challenge – Puzzle – Usage of FAST Hint SQL SERVER – Puzzle – Challenge – Error While Converting Money to Decimal SQL SERVER – Challenge – Puzzle – Why does RIGHT JOIN Exists 2011 DVM sys.dm_os_sys_info Column Name Changed in SQL Server 2012 Have you ever faced a situation where something does not work? When you try to fix it - you enjoy fixing it and started to appreciate the breaking changes. Well, this was exactly I felt yesterday. Before I begin my story, I want to candidly state that I do not encourage anybody to use * in the SELECT statement. Now the disclaimer is over – I suggest you read the original story – you will love it! Get Directory Structure using Extended Stored Procedure xp_dirtree Here is the question to you – why would you do something in SQL Server where you can do the same task in command prompt much easily. Well, the answer is sometime there are real use cases when we have to do such thing. This is a similar example where I have demonstrated how in SQL Server 2012 we can use extended stored procedure to retrieve directory structure. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• What Counts For A DBA: Foresight

  - by drsql

  Of all the valuable attributes of a DBA covered so far in this series, ranging from passion to humility to practicality, perhaps one of the most important attributes may turn out to be the most seemingly-nebulous: foresight. According to Free Dictionary foresight is the "perception of the significance and nature of events before they have occurred". Foresight does not come naturally to most people, as the parent of any teenager will attest. No matter how clearly you see their problems coming they won't listen, and have to fail before eventually (hopefully) learning for themselves. Having graduated from the school of hard knocks, the DBA, the naive teenager no longer, acquires the ability to foretell how events will unfold in response to certain actions or attitudes with the unerring accuracy of a doom-laden prophet. Like Simba in the Lion King, after a few blows to the head, we foretell that a sore head that will be the inevitable consequence of a swing of Rafiki's stick, and we take evasive action. However, foresight is about more than simply learning when to duck. It's about taking the time to understand and prevent the habits that caused the stick to swing in the first place. And based on this definition, I often think there is a lot less foresight on display in my industry than there ought to be. Most DBAs reading this blog will spot a line such as the following in a piece of "working" code, understand immediately why it is less than optimimum, and take evasive action. …WHERE CAST (columnName as int) = 1 However, the programmers who regularly write this sort of code clearly lack that foresight, and this and numerous other examples of similarly-malodorous code prevail throughout our industry (and provide premium-grade fertilizer for the healthy growth of many a consultant's bank account). Sometimes, perhaps harried by impatient managers and painfully tight deadlines, everyone makes mistakes. Yes, I too occasionally write code that "works", but basically stinks. When the problems manifest, it is sometimes accompanied by a sense of grim recognition that somewhere in me existed the foresight to know that that approach would lead to this problem. However, in the headlong rush, warning signs got overlooked, lessons learned previously, which could supply the foresight to the current project, were lost and not applied.   Of course, the problem often is a simple lack of skills, training and knowledge in the relevant technology and/or business space; programmers and DBAs forced to do their best in the face of inadequate training, or to apply their skills in areas where they lack experience. However, often the problem goes deeper than this; I detect in some DBAs and programmers a certain laziness of attitude.   They veer from one project to the next, going with "whatever works", unwilling or unable to take the time to understand where their actions are leading them. Of course, the whole "Agile" mindset is often interpreted to favor flexibility and rapid production over aiming to get things right the first time. The faster you try to travel in the dark, frequently changing direction, the more important it is to have someone who has the foresight to know at least roughly where you are heading. This is doubly true for the data tier which, no matter how you try to deny it, simply cannot be "redone" every month as you learn aspects of the world you are trying to model that, with a little bit of foresight, you would have seen coming.   Sometimes, when as a DBA you can glance briefly at 200 lines of working SQL code and know instinctively why it will cause problems, foresight can feel like magic, but it isn't; it's more like muscle memory. It is acquired as the consequence of good experience, useful communication with those around you, and a willingness to learn continually, through continued education as well as from failure. Foresight can be deployed only by finding time to understand how the lessons learned from other DBAs, and other projects, can help steer the current project in the right direction.   C.S. Lewis once said "The future is something which everyone reaches at the rate of sixty minutes an hour, whatever he does, whoever he is." It cannot be avoided; the quality of what you build now is going to affect you, and others, at some point in the future. Take the time to acquire foresight; it is a love letter to your future self, to say you cared.

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• My First Weeks at Red Gate

  - by Jess Nickson

  Hi, my name’s Jess and early September 2012 I started working at Red Gate as a Software Engineer down in The Agency (the Publishing team). This was a bit of a shock, as I didn’t think this team would have any developers! I admit, I was a little worried when it was mentioned that my role was going to be different from normal dev. roles within the company. However, as luck would have it, I was placed within a team that was responsible for the development and maintenance of Simple-Talk and SQL Server Central (SSC). I felt rather unprepared for this role. I hadn’t used many of the technologies involved and of those that I had, I hadn’t looked at them for quite a while. I was, nevertheless, quite excited about this turn of events. As I had predicted, the role has been quite challenging so far. I expected that I would struggle to get my head round the large codebase already in place, having never used anything so much as a fraction of the size of this before. However, I was perhaps a bit naive when it came to how quickly things would move. I was required to start learning/remembering a number of different languages and technologies within time frames I would never have tried to set myself previously. Having said that, my first week was pretty easy. It was filled with meetings that were designed to get the new starters up to speed with the different departments, ideals and rules within the company. I also attended some lightning talks being presented by other employees, which were pretty useful. These occur once a fortnight and normally consist of around four speakers. In my spare time, we set up the Simple-Talk codebase on my computer and I started exploring it and worked on my first feature – redirecting requests for URLs that used incorrect casing! It was also during this time that I was given my first introduction to test-driven development (TDD) with Michael via a code kata. Although I had heard of the general ideas behind TDD, I had definitely never tried it before. Indeed, I hadn’t really done any automated testing of code before, either. The session was therefore very useful and gave me insights as to some of the coding practices used in my team. Although I now understand the importance of TDD, it still seems odd in my head and I’ve yet to master how to sensibly step up the functionality of the code a bit at a time. The second week was both easier and more difficult than the first. I was given a new project to work on, meaning I was no longer using the codebase already in place. My job was to take some designs, a WordPress theme, and some initial content and build a page that allowed users of the site to read provided resources and give feedback. This feedback could include their thoughts about the resource, the topics covered and the page design itself. Although it didn’t sound the most challenging of projects when compared to fixing bugs in our current codebase, it nevertheless provided a few sneaky problems that had me stumped. I really enjoyed working on this project as it allowed me to play around with HTML, CSS and JavaScript; all things that I like working with but rarely have a chance to use. I completed the aims for the project on time and was happy with the final outcome – though it still needs a good designer to take a look at it! I am now into my third week at Red Gate and I have temporarily been pulled off the website from week 2. I am again back to figuring out the Simple-Talk codebase. Monday provided me with the chance to learn a bunch of new things: system level testing, Selenium and Python. I was set the challenge of testing a bug fix dealing with the search bars in Simple-Talk. The exercise was pretty fun, although Mike did have to point me in the right direction when I started making the tests a bit too complex. The rest of the week looks set to be focussed on pair programming with Mike as we work together on a new feature. I look forward to the challenges that still face me and hope that I will be able to get up to speed quickly. *fingers crossed*

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• Implementing a Custom Coherence PartitionAssignmentStrategy

  - by jpurdy

  A recent A-Team engagement required the development of a custom PartitionAssignmentStrategy (PAS). By way of background, a PAS is an implementation of a Java interface that controls how a Coherence partitioned cache service assigns partitions (primary and backup copies) across the available set of storage-enabled members. While seemingly straightforward, this is actually a very difficult problem to solve. Traditionally, Coherence used a distributed algorithm spread across the cache servers (and as of Coherence 3.7, this is still the default implementation). With the introduction of the PAS interface, the model of operation was changed so that the logic would run solely in the cache service senior member. Obviously, this makes the development of a custom PAS vastly less complex, and in practice does not introduce a significant single point of failure/bottleneck. Note that Coherence ships with a default PAS implementation but it is not used by default. Further, custom PAS implementations are uncommon (this engagement was the first custom implementation that we know of). The particular implementation mentioned above also faced challenges related to managing multiple backup copies but that won't be discussed here. There were a few challenges that arose during design and implementation: Naive algorithms had an unreasonable upper bound of computational cost. There was significant complexity associated with configurations where the member count varied significantly between physical machines. Most of the complexity of a PAS is related to rebalancing, not initial assignment (which is usually fairly simple). A custom PAS may need to solve several problems simultaneously, such as: Ensuring that each member has a similar number of primary and backup partitions (e.g. each member has the same number of primary and backup partitions) Ensuring that each member carries similar responsibility (e.g. the most heavily loaded member has no more than one partition more than the least loaded). Ensuring that each partition is on the same member as a corresponding local resource (e.g. for applications that use partitioning across message queues, to ensure that each partition is collocated with its corresponding message queue). Ensuring that a given member holds no more than a given number of partitions (e.g. no member has more than 10 partitions) Ensuring that backups are placed far enough away from the primaries (e.g. on a different physical machine or a different blade enclosure) Achieving the above goals while ensuring that partition movement is minimized. These objectives can be even more complicated when the topology of the cluster is irregular. For example, if multiple cluster members may exist on each physical machine, then clearly the possibility exists that at certain points (e.g. following a member failure), the number of members on each machine may vary, in certain cases significantly so. Consider the case where there are three physical machines, with 3, 3 and 9 members each (respectively). This introduces complexity since the backups for the 9 members on the the largest machine must be spread across the other 6 members (to ensure placement on different physical machines), preventing an even distribution. For any given problem like this, there are usually reasonable compromises available, but the key point is that objectives may conflict under extreme (but not at all unlikely) circumstances. The most obvious general purpose partition assignment algorithm (possibly the only general purpose one) is to define a scoring function for a given mapping of partitions to members, and then apply that function to each possible permutation, selecting the most optimal permutation. This would result in N! (factorial) evaluations of the scoring function. This is clearly impractical for all but the smallest values of N (e.g. a partition count in the single digits). It's difficult to prove that more efficient general purpose algorithms don't exist, but the key take away from this is that algorithms will tend to either have exorbitant worst case performance or may fail to find optimal solutions (or both) -- it is very important to be able to show that worst case performance is acceptable. This quickly leads to the conclusion that the problem must be further constrained, perhaps by limiting functionality or by using domain-specific optimizations. Unfortunately, it can be very difficult to design these more focused algorithms. In the specific case mentioned, we constrained the solution space to very small clusters (in terms of machine count) with small partition counts and supported exactly two backup copies, and accepted the fact that partition movement could potentially be significant (preferring to solve that issue through brute force). We then used the out-of-the-box PAS implementation as a fallback, delegating to it for configurations that were not supported by our algorithm. Our experience was that the PAS interface is quite usable, but there are intrinsic challenges to designing PAS implementations that should be very carefully evaluated before committing to that approach.

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• Java ReentrantReadWriteLocks - how to safely acquire write lock?

  - by Andrzej Doyle

  I am using in my code at the moment a ReentrantReadWriteLock to synchronize access over a tree-like structure. This structure is large, and read by many threads at once with occasional modifications to small parts of it - so it seems to fit the read-write idiom well. I understand that with this particular class, one cannot elevate a read lock to a write lock, so as per the Javadocs one must release the read lock before obtaining the write lock. I've used this pattern successfully in non-reentrant contexts before. What I'm finding however is that I cannot reliably acquire the write lock without blocking forever. Since the read lock is reentrant and I am actually using it as such, the simple code lock.getReadLock().unlock(); lock.getWriteLock().lock() can block if I have acquired the readlock reentrantly. Each call to unlock just reduces the hold count, and the lock is only actually released when the hold count hits zero. EDIT to clarify this, as I don't think I explained it too well initially - I am aware that there is no built-in lock escalation in this class, and that I have to simply release the read lock and obtain the write lock. My problem is/was that regardless of what other threads are doing, calling getReadLock().unlock() may not actually release this thread's hold on the lock if it acquired it reentrantly, in which case the call to getWriteLock().lock() will block forever as this thread still has a hold on the read lock and thus blocks itself. For example, this code snippet will never reach the println statement, even when run singlethreaded with no other threads accessing the lock: final ReadWriteLock lock = new ReentrantReadWriteLock(); lock.getReadLock().lock(); // In real code we would go call other methods that end up calling back and // thus locking again lock.getReadLock().lock(); // Now we do some stuff and realise we need to write so try to escalate the // lock as per the Javadocs and the above description lock.getReadLock().unlock(); // Does not actually release the lock lock.getWriteLock().lock(); // Blocks as some thread (this one!) holds read lock System.out.println("Will never get here"); So I ask, is there a nice idiom to handle this situation? Specifically, when a thread that holds a read lock (possibly reentrantly) discovers that it needs to do some writing, and thus wants to "suspend" its own read lock in order to pick up the write lock (blocking as required on other threads to release their holds on the read lock), and then "pick up" its hold on the read lock in the same state afterwards? Since this ReadWriteLock implementation was specifically designed to be reentrant, surely there is some sensible way to elevate a read lock to a write lock when the locks may be acquired reentrantly? This is the critical part that means the naive approach does not work.

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• Most efficient algorithm for merging sorted IEnumerable<T>

  - by franck

  Hello, I have several huge sorted enumerable sequences that I want to merge. Theses lists are manipulated as IEnumerable but are already sorted. Since input lists are sorted, it should be possible to merge them in one trip, without re-sorting anything. I would like to keep the defered execution behavior. I tried to write a naive algorithm which do that (see below). However, it looks pretty ugly and I'm sure it can be optimized. It may exist a more academical algorithm... IEnumerable<T> MergeOrderedLists<T, TOrder>(IEnumerable<IEnumerable<T>> orderedlists, Func<T, TOrder> orderBy) { var enumerators = orderedlists.ToDictionary(l => l.GetEnumerator(), l => default(T)); IEnumerator<T> tag = null; var firstRun = true; while (true) { var toRemove = new List<IEnumerator<T>>(); var toAdd = new List<KeyValuePair<IEnumerator<T>, T>>(); foreach (var pair in enumerators.Where(pair => firstRun || tag == pair.Key)) { if (pair.Key.MoveNext()) toAdd.Add(pair); else toRemove.Add(pair.Key); } foreach (var enumerator in toRemove) enumerators.Remove(enumerator); foreach (var pair in toAdd) enumerators[pair.Key] = pair.Key.Current; if (enumerators.Count == 0) yield break; var min = enumerators.OrderBy(t => orderBy(t.Value)).FirstOrDefault(); tag = min.Key; yield return min.Value; firstRun = false; } } The method can be used like that: // Person lists are already sorted by age MergeOrderedLists(orderedList, p => p.Age); assuming the following Person class exists somewhere: public class Person { public int Age { get; set; } } Duplicates should be conserved, we don't care about their order in the new sequence. Do you see any obvious optimization I could use?

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• Convert JSON flattened for forms back to an object

  - by George Jempty

  I am required (please therefore no nit-picking the requirement, I've already nit-picked it, and this is the req) to convert certain form fields that have "object nesting" embedded in the field names, back to the object(s) themselves. Below are some typical form field names: phones_0_patientPhoneTypeId phones_0_phone phones_1_patientPhoneTypeId phones_1_phone The form fields above were derived from an object such as the one toward the bottom (see "Data"), and that is the format of the object I need to reassemble. It can be assumed that any form field with a name that contains the underscore _ character needs to undergo this conversion. Also that the segment of the form field between underscores, if numeric, signifies a Javascript array, otherwise an object. I found it easy to devise a (somewhat naive) implementation for the "flattening" of the original object for use by the form, but am struggling going in the other direction; below the object/data below I'm pasting my current attempt. One problem (perhaps the only one?) with it is that it does not currently properly account for array indexes, but this might be tricky because the object will subsequently be encoded as JSON, which will not account for sparse arrays. So if "phones_1" exists, but "phones_0" does not, I would nevertheless like to ensure that a slot exists for phones[0] even if that value is null. Implementations that tweak what I have begun, or are entirely different, encouraged. If interested let me know if you'd like to see my code for the "flattening" part that is working. Thanks in advance Data: var obj = { phones: [{ "patientPhoneTypeId": 4, "phone": "8005551212" }, { "patientPhoneTypeId": 2, "phone": "8885551212" }]}; Code to date: var unflattened = {}; for (var prop in values) { if (prop.indexOf('_') > -1) { var lastUnderbarPos = prop.lastIndexOf('_'); var nestedProp = prop.substr(lastUnderbarPos + 1); var nesting = prop.substr(0, lastUnderbarPos).split("_"); var nestedRef, isArray, isObject; for (var i=0, n=nesting.length; i<n; i++) { if (i===0) { nestedRef = unflattened; } if (i < (n-1)) { // not last if (/^\d+$/.test(nesting[i+1])) { isArray = true; isObject = false; } else { isArray = true; isObject = false; } var currProp = nesting[i]; if (!nestedRef[currProp]) { if (isArray) { nestedRef[currProp] = []; } else if (isObject) { nestedRef[currProp] = {}; } } nestedRef = nestedRef[currProp]; } else { nestedRef[nestedProp] = values[prop]; } } }

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• How to make efficient code emerge through unit testing

  - by Jean

  Hi, I participate in a TDD Coding Dojo, where we try to practice pure TDD on simple problems. It occured to me however that the code which emerges from the unit tests isn't the most efficient. Now this is fine most of the time, but what if the code usage grows so that efficiency becomes a problem. I love the way the code emerges from unit testing, but is it possible to make the efficiency property emerge through further tests ? Here is a trivial example in ruby: prime factorization. I followed a pure TDD approach making the tests pass one after the other validating my original acceptance test (commented at the bottom). What further steps could I take, if I wanted to make one of the generic prime factorization algorithms emerge ? To reduce the problem domain, let's say I want to get a quadratic sieve implementation ... Now in this precise case I know the "optimal algorithm, but in most cases, the client will simply add a requirement that the feature runs in less than "x" time for a given environment. require 'shoulda' require 'lib/prime' class MathTest < Test::Unit::TestCase context "The math module" do should "have a method to get primes" do assert Math.respond_to? 'primes' end end context "The primes method of Math" do should "return [] for 0" do assert_equal [], Math.primes(0) end should "return [1] for 1 " do assert_equal [1], Math.primes(1) end should "return [1,2] for 2" do assert_equal [1,2], Math.primes(2) end should "return [1,3] for 3" do assert_equal [1,3], Math.primes(3) end should "return [1,2] for 4" do assert_equal [1,2,2], Math.primes(4) end should "return [1,5] for 5" do assert_equal [1,5], Math.primes(5) end should "return [1,2,3] for 6" do assert_equal [1,2,3], Math.primes(6) end should "return [1,3] for 9" do assert_equal [1,3,3], Math.primes(9) end should "return [1,2,5] for 10" do assert_equal [1,2,5], Math.primes(10) end end # context "Functionnal Acceptance test 1" do # context "the prime factors of 14101980 are 1,2,2,3,5,61,3853"do # should "return [1,2,3,5,61,3853] for ${14101980*14101980}" do # assert_equal [1,2,2,3,5,61,3853], Math.primes(14101980*14101980) # end # end # end end and the naive algorithm I created by this approach module Math def self.primes(n) if n==0 return [] else primes=[1] for i in 2..n do if n%i==0 while(n%i==0) primes<<i n=n/i end end end primes end end end

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• Translate Java class with static attributes and Annotation to Scala equivalent

  - by ifischer

  I'm currently trying to "translate" the following Java class to an equivalent Scala class. It's part of a JavaEE6-application and i need it to use the JPA2 MetaModel. import javax.persistence.metamodel.SingularAttribute; import javax.persistence.metamodel.StaticMetamodel; @StaticMetamodel(Person.class) public class Person_ { public static volatile SingularAttribute<Person, String> name; } A dissassembling of the compiled class file reveals the following information for the compiled file: > javap Person_.class : public class model.Person_ extends java.lang.Object{ public static volatile javax.persistence.metamodel.SingularAttribute name; public model.Person_(); } So now i need an equivalent Scala file that has the same structure, as JPA depends on it, cause it resolves the attributes by reflection to make them accessible at runtime. So the main problem i think is that the attribute is static, but the Annotation has to be on an (Java)Object (i guess) My first naive attempt to create a Scala equivalent is the following: @StaticMetamodel(classOf[Person]) class Person_ object Person_ { @volatile var name:SingularAttribute[Person, String] = _; } But the resulting classfile is far away from the Java one, so it doesn't work. When trying to access the attributes at runtime, e.g. "Person_.firstname", it resolves to null, i think JPA can't do the right reflection magic on the compiled classfile (the Java variant resolves to an instance of org.hibernate.ejb.metamodel.SingularAttributeImpl at runtime). > javap Person_.class : public class model.Person_ extends java.lang.Object implements scala.ScalaObject{ public static final void name_$eq(javax.persistence.metamodel.SingularAttribute); public static final javax.persistence.metamodel.SingularAttribute name(); public model.Person_(); } > javap Person_$.class : public final class model.Person__$ extends java.lang.Object implements scala.ScalaObject public static final model.Person__$ MODULE$; public static {}; public javax.persistence.metamodel.SingularAttribute name(); public void name_$eq(javax.persistence.metamodel.SingularAttribute); } So now what i'd like to know is if it's possible at all to create a Scala equivalent of the Java class? It seems to me that it's absolutely not, but maybe there is a workaround or something (except just using Java, but i want my app to be in Scala where possible) Any ideas, anyone? Thanks in advance!

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• Synchronizing thread communication?

  - by Roger Alsing

  Just for the heck of it I'm trying to emulate how JRuby generators work using threads in C#. Also, I'm fully aware that C# haas built in support for yield return, I'm just toying around a bit. I guess it's some sort of poor mans coroutines by keeping multiple callstacks alive using threads. (even though none of the callstacks should execute at the same time) The idea is like this: The consumer thread requests a value The worker thread provides a value and yields back to the consumer thread Repeat untill worker thread is done So, what would be the correct way of doing the following? //example class Program { static void Main(string[] args) { ThreadedEnumerator<string> enumerator = new ThreadedEnumerator<string>(); enumerator.Init(() => { for (int i = 1; i < 100; i++) { enumerator.Yield(i.ToString()); } }); foreach (var item in enumerator) { Console.WriteLine(item); }; Console.ReadLine(); } } //naive threaded enumerator public class ThreadedEnumerator<T> : IEnumerator<T>, IEnumerable<T> { private Thread enumeratorThread; private T current; private bool hasMore = true; private bool isStarted = false; AutoResetEvent enumeratorEvent = new AutoResetEvent(false); AutoResetEvent consumerEvent = new AutoResetEvent(false); public void Yield(T item) { //wait for consumer to request a value consumerEvent.WaitOne(); //assign the value current = item; //signal that we have yielded the requested enumeratorEvent.Set(); } public void Init(Action userAction) { Action WrappedAction = () => { userAction(); consumerEvent.WaitOne(); enumeratorEvent.Set(); hasMore = false; }; ThreadStart ts = new ThreadStart(WrappedAction); enumeratorThread = new Thread(ts); enumeratorThread.IsBackground = true; isStarted = false; } public T Current { get { return current; } } public void Dispose() { enumeratorThread.Abort(); } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { if (!isStarted) { isStarted = true; enumeratorThread.Start(); } //signal that we are ready to receive a value consumerEvent.Set(); //wait for the enumerator to yield enumeratorEvent.WaitOne(); return hasMore; } public void Reset() { throw new NotImplementedException(); } public IEnumerator<T> GetEnumerator() { return this; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this; } } Ideas?

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• Invoke Python modules from Java

  - by user36813

  I have a Python interface of a graph library written in C - igraph (the name of library). My need is to invoke the python modules pertaining to this graph library from Java code. It goes like this, the core of library is in c. This core has been imported into Python and interfaces to the functions embedded in core are available in Python. My project's rest of the code is in Java and hence I would like to call the graph functions by Java as well. Jython - which lets you invoke python modules with in Java was an option.I went on trying Jython to discover that it will not work in my case as the core code is in C and Jython wont support anything that is imported as a c dll in python code.I also thought of opting for the approach of calling graph routines directly in c. That is without passing through Python code. I am assuming there must be something which lets you call c code from Java, how ever I am not good in C hence I did not go for it. My last resort seems to execute Python interpreter from command line using Java. But that is a dirty and shameless. Also to deal with the results produced by Python code I will have to write the results in a file and read it back in java. Again dirty way. Is there something that any one can suggest me? Thanks to every one giving time. Thanks Igal for answering. I had a look at it. At first glance it appears as if it is simply calling the python script. Jep jep = new Jep(false, SCRIPT_PATH, cl); jep.set("query", query); jep.runScript(SCRIPT_PATH + file); jep.close(); Isnt it very similar to what we would do if called the python interpreter from command line through a Java code. Runtime runtime = Runtime.getRuntime(); Process proc = runtime.exec("python test.py"); Concern is how do I use the results generated by Python script. The naive way is to write them to file and read it back in Java. I am searching for a smarter approach.Thanks for suggestion anyway.

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• gcc, strict-aliasing, and casting through a union

  - by Joseph Quinsey

  About a year ago the following paragraph was added to the GCC Manual, version 4.3.4, regarding -fstrict-aliasing: Similarly, access by taking the address, casting the resulting pointer and dereferencing the result has undefined behavior [emphasis added], even if the cast uses a union type, e.g.: union a_union { int i; double d; }; int f() { double d = 3.0; return ((union a_union *)&d)->i; } Does anyone have an example to illustrate this undefined behavior? Note this question is not about what the C99 standard says, or does not say. It is about the actual functioning of gcc, and other existing compilers, today. My simple, naive, attempt fails. For example: #include <stdio.h> union a_union { int i; double d; }; int f1(void) { union a_union t; t.d = 3333333.0; return t.i; // gcc manual: 'type-punning is allowed, provided ...' } int f2(void) { double d = 3333333.0; return ((union a_union *)&d)->i; // gcc manual: 'undefined behavior' } int main(void) { printf("%d\n", f1()); printf("%d\n", f2()); return 0; } works fine, giving on CYGWIN: -2147483648 -2147483648 Also note that taking addresses is obviously wrong (or right, if you are trying to illustrate undefined behavior). For example, just as we know this is wrong: extern void foo(int *, double *); union a_union t; t.d = 3.0; foo(&t.i, &t.d); // UD behavior so is this wrong: extern void foo(int *, double *); double d = 3.0; foo(&((union a_union *)&d)->i, &d); // UD behavior For background discussion about this, see for example: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1422.pdf http://gcc.gnu.org/ml/gcc/2010-01/msg00013.html http://davmac.wordpress.com/2010/02/26/c99-revisited/ http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html http://stackoverflow.com/questions/98650/what-is-the-strict-aliasing-rule http://stackoverflow.com/questions/2771023/c99-strict-aliasing-rules-in-c-gcc/2771041#2771041 The first link, draft minutes of an ISO meeting seven months ago, notes in section 4.16: Is there anybody that thinks the rules are clear enough? No one is really able to interpret tham.

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