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• Can certain system-hungry modules be disabled in Ubuntu?

  - by Ole Thomsen Buus

  Hi, Let me add some context: I am currently using Ubuntu 9.10 64-bit (Desktop) on a relatively powerful stationary PC (Intel Core i7 920, 12GB ram). My purpose is highspeed imaging with a pointgrey Grashopper machine-vision camera (for research, PhD project). This camera is capable of 200 fps at full VGA (640x480) resolution. The camera is connected using Firewire (1394b) and the drivers and software from Pointgrey works great. I have developed a console C++ application that can grap a certain number of frames to preallocated memory and after this also save the grapped frames to harddrive. Currently it works fine but sometimes I am observing a few framedrops (1-3). When this happens I reset the experiment and repeat the recording and usually i am lucky the second time with no framedrops (the camera-driver has a internal framecounter that I am using). Question: I usually go to tty1 and use "sudo service gdm stop" to disable the graphical frontend. It seems to release some memory though that is not my main concern. My concern is CPU resources. Are there other system hungry modules that can be disabled temporarily such that the CPU gets less busy on Ubuntu 9.10? At some point in the future I will update to 10.10. Should I perhaps option for the server edition instead? Thanks.

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• Simple website with a GPL V3 Framework

  - by sineverba

  I write web-based software and simple website ("Home", "Who we are", "Contact"). For a simple website I'm using a covered GPL v3 framework. The user surf the website, send an email, take info, etc. I repeat: simple website, not a Joomla or Wordpress. 1) Will the website be covered with the GPL? I don't modify the framework. I'm using his classes in other classes... (OOP). 2) For the point 1, if yes, do I need to add (e.g. in the footer) name of framework and his link? 3) I must permit download of entire website to study code (nothing that a programmer has interest in)? E.g. placing it in Github? 4) If 2 is NO, how you can "understand" that we use that framework? In effect no php lines are exposed to the browser... You cannot understand that when you push "Send email" the site is calling $this->send($email). If you write me an email "Are you using XXX framework"? I can answer NO.

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• Are there design patterns or generalised approaches for particle simulations?

  - by romeovs

  I'm working on a project (for college) in C++. The goal is to write a program that can more or less simulate a beam of particles flying trough the LHC synchrotron. Not wanting to rush into things, me and my team are thinking about how to implement this and I was wondering if there are general design patterns that are used to solve this kind of problem. The general approach we came up with so far is the following: there is a World that holds all objects you can add objects to this world such as Particle, Dipole and Quadrupole time is cut up into discrete steps, and at each point in time, for each Particle the magnetic and electric forces that each object in the World generates are calculated and summed up (luckily electro-magnetism is linear). each Particle moves accordingly (using a simple estimation approach to solve the differential movement equations) save the Particle positions repeat This seems a good approach but, for instance, it is hard to take into account symmetries that might be present (such as the magnetic field of each Quadrupole) and is this thus suboptimal. To take into account such symmetries as that of the Quadrupole field, it would be much easier to (also) make space discrete and somehow store form of the Quadrupole field somewhere. (Since 2532 or so Quadrupoles are stored this should lead to a massive gain of performance, not having to recalculate each Quadrupole field) So, are there any design patterns? Is the World-approach feasible or is it old-fashioned, bad programming? What about symmetry, how is that generally taken into acount?

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• Where should "display functions" live in an MVC web app?

  - by User

  I'm using the Yii Framework which is an MVC php framework that is pretty similar to your standard web-based MVC framework. I want to display the related data from a many-to-many table as a list of strings in my view. Assuming a table schema like: tag { id, name } post { id, title, content, date } post_tag { post_id, tag_id } A post will display like: Date: 9/27/2012 Title: Some Title Content: blah blah blah... Tags: Smart Funny Cool Informative I can achieve this by doing something like this in my Post view: <?php echo join(' ', array_map(function($tag) { return $tag->name; }, $model->tags)); ?> (where $model->tags is an array of Tag objects associated with my model) My questions are: Is this amount of code/logic okay in the view? (Personally I think I'd rather just reference a property or call a single function.) If not, where should this code live? In the model? the controller? a helper? Potentially I may want to use in in other views as well. Ultimately I think its purely a display issue which would make me think it should be in the view, but then I have to repeat the code in any view I want to use it in.

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• C# Threading Background Process - Programming - How to?

  - by Magic

  Hello...I have been given the horrible task of doing this. Launch the website Take a screenshot Fill in the form details, click on Next Take a screenshot ... ... ... Rinse. Repeat. Now, with various combinations, this comes up to 300 screenshots. And I have to do this for 4 different browsers. Chrome, Firefox, IE 6 and IE 7. I cannot use tools which will capture the screenshot and store them, such as, SnagIT. I need to take a screenshot, copy it to a Word Document and take the second screenshot and take it to a Word Document. I thought, I will write a tiny utility which will help me do this. Here is the requirement spec that I put up for it - An executable which once launched seats itself in the System Tray. While it is active, all instances of Key Press (Print Scrn), it should write the contents to a Word Document as defined (either a default path or a user defined one). Save the document periodically. Now, my question is - if I am going to develop this using C# (Winforms application), how do I go about doing this. I can do a fair bit of C# programming and I am willing to learn. But I am not able to locate the references for how to do a background process so that it runs in the background. And while it runs, it has to capture the Print Scrn command. Can you folks point me to the right material where I can learn this? Theoretical references should suffice. But if there are practical references, then nothing like it. Thanks!

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• Late feedback

  - by Sveta Smirnova

  MySQL Community team asked me to write about Devconf 2013 few months ago. Conference was in June, 2013, but I remembered about this my promise only now: month later after my participating in MySQL Connect and Expert Troubleshooting seminar (change country to United Kingdom if you see blank page). I think it is too late for the feedback, but I still have few thoughts which I want to record.DevConf (former PHPConf) always was a place where I tried new topics. At first, because I know audience there very well and they will be bored if I repeat a story which I was telling last year, but also because it is much easier to get feedback in your own native language. But last years my habit seems started to change and I presented improved version of my 2012 MySQL Connect talk about MySQL backups. Of course, I also had a seminar with unique topic, made for this conference first time: Troubleshooting MySQL Performance with EXPLAIN and Using Performance Schema to Troubleshoot MySQL. And these topics, improved, were presented at the expert seminar. It is interesting how my habit changes and one public speaking activity interferes next one.What is good about DevConf is it forces you to create new ideas and do it really well, because audience is not forgiving at all, so they catch everything you miss or prepared not good enough. This can be bad if you want to make a marketing-style topic for free, but allows to present technical features in really good details: all these sudden discussions really help.In year 2013 Oracle had a booth at the conference and was presented by a bunch of people. Dmitry Lenev presented topic "New features of replication in MySQL 5.6" and Victoria Reznichenko worked on the booth. What was new at the conference this year is greater interest in NoSQL, scale and fast development solutions. This, unfortunately, means not so huge interest in MySQL as it was earlier. However, at the same time, "Common" track was really MySQL track: not only Oracle, but people from other companies presented about it.

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• How do I improve terrain rendering batch counts using DirectX?

  - by gamer747

  We have determined that our terrain rendering system needs some work to minimize the number of batches being transferred to the GPU in order to improve performance. I'm looking for suggestions on how best to improve what we're trying to accomplish. We logically split our terrain mesh into smaller grid cells which are 32x32 world units. Each cell has meta data that dictates the four 256x256 textures that are used for spatting along with the alpha blend data, shadow, and light mappings. Each cell contains 81 vertices in a 9x9 grid. Presently, we examine each cell and determine the four textures that are being used to spat the cell. We combine that geometry with any other cell that perhaps uses the same four textures regardless of spat order. If the spat order for a cell differs, the blend map is adjusted so that the spat order is maintained the same as other like cells and blending happens in the right order too. But even with this batching approach, it isn't uncommon when looking out across an area of open terrain to have between 1200-1700 batch count depending upon how frequently textures differ or have different texture blends are between cells. We are only doing frustum culling presently. So using texture spatting, are there other alternatives that can reduce the batch count and allow rendering to be extremely performance-friendly even under DirectX9c? We considered using texture atlases since we're targeting DirectX 9c & older OpenGL platforms but trying to repeat textures using atlases and shaders result in seam artifacts which we haven't been able to eliminate with the exception of disabling mipmapping. Disabling mipmapping results in poor quality textures from a distance. How have others batched together terrain geometry such that one could spat terrain using various textures, minimizing batch count and texture state switches so that rendering performance isn't negatively impacted?

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• Cookie access within a HTTP Class

  - by James Jeffery

  I have a HTTP class that has a Get, and Post, method. It's a simple class I created to encapsulate Post and Get requests so I don't have to repeat the get/post code throughout the application. In C#: class HTTP { private CookieContainer cookieJar; private String userAgent = "..."; public HTTP() { this.cookieJar = new CookieContainer(); } public String get(String url) { // Make get request. Return the JSON } public String post(String url, String postData) { // Make post request. Return the JSON } } I've made the CookieJar a property because I want to preserve the cookie values throughout the session. If the user is logged into Twitter with my application, each request I make (be it get or post) I want to use the cookies so they remain logged in. That's the basics of it anyway. But, I don't want to return a string in all instances. Sometimes I may want the cookie, or a header value, or something else from the request. Ideally I'd like to be able to do this in my code: Cookie cookie = http.get("http://google.com").cookie("g_user"); String g_user = cookie.value; or String source = http.get("http://google.com").body; My question - To do this, would I need to have a Get class, and a Post class, that are included within the HTTP class and are accessible via accessors? Within the Get and Post class I would then have the Cookie method, and the body property, and whatever else is needed. Should I also use an interface, or create a Request class and have Post and Get extend it so that common methods and properties are available to both classes? Or, am I thinking totally wrong?

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• Blogger Blog Takes Ages to Load after Custom Domain Redirection

  - by abhisek

  I recently bought a custom domain for a blogger blog (technabled.com) I have for sometime now. I followed the instructions on blogger's documentation. I added A-name records and CNAME records with my DNS provider. But, now, some strange problems are cropping up. If I connect to my broadband network and then ping technabled.com, it times out. Then, if I visit the webpage, which takes almost one and half minutes to load, and then if I ping technabled.com, it shows expected result. This is not just me. I asked some of the regular readers, who reported the same issue. As a result of this, I am losing a lot of visits. What is stranger is that the subsequent visits to the blog is faster. I have checked with a few online services to test the performance. WebPageTest seems to say the same thing: http://www.webpagetest.org/result/110117_1N_7PE/ (please see the First View / Repeat View time) Also, the pagespeed score is not that bad. So I am ruling out other possibilities. I am at a loss as to what I should do to find a solution. Help is much appreciated. :)

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• Good sysadmin practise?

  - by Randomthrowaway

  Throwaway account here. Recently our sysadmin sent us the following email (I removed the names): Hi, I had a situation yesterday (not mentioning names) when I had to perform a three way md5 checksum verification over the phone, more than once. If we can stick to the same standards then this will save any confusion if you are ever asked to repeat something over the phone or in the office for clarification. This is of particular importance when trying to speak or say this over the phone … m4f7s29gsd32156ffsdf … that’s really difficult to get right on a bad line. The rule is very simple: 1) Speak in blocks of 4 characters and continue until the end. The recipient can read back or ask for verification on one of the blocks. 2) Use the same language! http://en.wikipedia.org/wiki/Phoenetic_alphabet#NATO Myself, xxx and a few others I know all speak the NATO phonetic alphabet (aka police speak) and this makes it so much easier and saves so much time. If you want to learn quickly then all you really need is A to F and 0 to 9. 0 to 9 is really easy, A to F is only 6 characters to learn. Could you tell me if forcing the developers to learn NATO alphabet is a good practise, or if there are ways (and which ways) to avoid being in such a situation?

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• How do I produce "enjoyably" random, as opposed to pseudo-random?

  - by Hilton Campbell

  I'm making a game which presents a number of different kinds of puzzles in sequence. I choose each puzzle with a pseudorandom number. For each puzzle, there are a number of variations. I choose the variation with another pseudorandom number. And so on. The thing is, while this produces near-true randomness, this isn't what the player really wants. The player typically wants what they perceive to be and identify as random, but only if it doesn't tend to repeat puzzles. So, not really random. Just unpredictable. Giving it some thought, I can imagine hacky ways of doing it. For example, temporarily eliminating the most recent N choices from the set of possibilities when selecting a new choice. Or assigning every choice an equal probability, reducing a choice's probability to zero on selection, and then increasing all probabilities slowly with each selection. I assume there's an established way of doing this, but I just don't know the terminology so I can't find it. Anyone know? Or has anyone solved this in a pleasing way?

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• How to refactor to cleaner version of maintaing states of the widget

  - by George

  Backstory I inherited a bunch of code that I'd like to refactor. It is a UI application written in javascript. Current state: We have main application which consist of several UI components. And each component has entry fields, textboxes, menus, etc), like "ticket", "customer information", etc. Based on input, where the application was called from, who is the user, we enable/disable, hide, show, change titles. Unfortunately, the app grew to the point where it is really hard to scale, add new features. Main the driver (application code) calls set/unset functions of the respective components. So a lot of the stuff look like this Main app unit function1() { **call_function2()** component1.setX(true); component1.setY(true); component2.setX(false); } call_function2() { // it may repeat some of the code function1 called } and we have a lot of this in the main union. I am cleaning this mess. What is the best way to maintain the state of widgets? Please let me know if you need me to clarify.

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• Authenticate with Django 1.5

  - by gorjuce

  I'm currently testing django 1.5 and a custom User model, but I've some problems. I've created a User class in my account app, which looks like: class User(AbstractBaseUser): email = models.EmailField() activation_key = models.CharField(max_length=255) is_active = models.BooleanField(default=False) is_admin = models.BooleanField(default=False) USERNAME_FIELD = 'email' I can correctly register a user, who is stored in my account_user table. Now, how can I log in? I've tried with: def login(request): form = AuthenticationForm() if request.method == 'POST': form = AuthenticationForm(request.POST) email = request.POST['username'] password = request.POST['password'] user = authenticate(username=email, password=password) if user is not None: if user.is_active: login(user) else: message = 'disabled account, check validation email' return render( request, 'account-login-failed.html', {'message': message} ) return render(request, 'account-login.html', {'form': form}) I can correctly register a new User My forms.py which contains my register form class RegisterForm(forms.ModelForm): """ a form to create user""" password = forms.CharField( label="Password", widget=forms.PasswordInput() ) password_confirm = forms.CharField( label="Password Repeat", widget=forms.PasswordInput() ) class Meta: model = User exclude = ('last_login', 'activation_key') def clean_password_confirm(self): password = self.cleaned_data.get("password") password_confirm = self.cleaned_data.get("password_confirm") if password and password_confirm and password != password_confirm: raise forms.ValidationError("Password don't math") return password_confirm def clean_email(self): if User.objects.filter(email__iexact=self.cleaned_data.get("email")): raise forms.ValidationError("email already exists") return self.cleaned_data['email'] def save(self): user = super(RegisterForm, self).save(commit=False) user.password = self.cleaned_data['password'] user.activation_key = generate_sha1(user.email) user.save() return user My question is: Why does authenticate give me None? I know I'm trying to authenticate() with an email as username but is that not one of the reasons to use a custom User model?

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• How to find out when to increase bit rate? (TCP streaming solution)

  - by Kabumbus

  How to find out when to increase bit rate? (TCP streaming solution) We have a stream with "frames". each "frame" has a "timestamp" . frames have bit rate property which is actually there size. We generate frames with our app and stream them one by one on to our TCP server socket. At the same time server post replies so when after each sent frame we try to read from socket we receive which timestamp is currently on server. if timestamp is lover than previous frame we lover bit rate 20%. Such scheme seems to work giving me one way vbr (lowering) but I wonder how to implement increase? I mean we can always try to increase 5% each frame until some limited desired value but each time we have delay will lose real-time feature of our stream... Generally such scheme is for finding out how much of network stream is currently used by other user apps and give picture of how much server is loaded at the same time so we can stream just right amount of data for all to receive it in real time. So what shall I do to add increase to my scheme? So having current bit rate of A I thought we could add +7% for 3 frames and than one -20% and than if all that 3 frames with +7% came in time we could add 14% to A and repeat circle and it would hopefully not be really noticeable if 2nd frame wold come to us with delay... probably this one is too localised because it is a requirement for me to use TCP.

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• Partition tool with console UI (as in server installation)?

  - by lepe

  Back in 2006, Ray (3DLover) posted the same question in: http://ubuntuforums.org/showthread.php?t=309680 but none of the answers were really useful. Now with a little help from AskUbuntu community, I would like to repeat his question again to see if this time it can be answered correctly. So this is the question (and what I wish too): I'm looking for a UI tool for managing partitions in a console. I have installed Ubuntu Server, so I don't have X Windows at all. fdisk and sfdisk are entirely command line. parted is slightly better, but it's not really a UI. cfdisk has somewhat of a UI, but it only works on one disk at a time, and there's no advanced options like configuring LVM or RAID. Just partitioning. I love the partition tool that is available during the OS install procedure. You can partition, configure RAID's and LMV sets. It can format the partitions with several different file systems, it can set labels, mount options and it can insert your volumes into your fstab. Is this tool available as a stand-alone program? I can't find it anywhere. I think it's called parted_server, but I can't find much information about where to get it. In the past, I have run the Ubuntu install procedure just to use the partition manager that comes with it. (canceling the install after making my partition edits) Anyone help me on this? Thanks -Ray Thanks in advance.

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• JSR 308 Moves Forward

  - by abuckley

  I am pleased to announce a number of recent milestones for JSR 308, Annotations on Java Types: Adoption of JCP 2.8 Thanks to the agreement of the Expert Group, JSR 308 operates under JCP 2.8 from September 2012. There is a publicly archived mailing list for EG members, and a companion list for anyone who wishes to follow EG traffic by email. There is also a "suggestion box" mailing list where anyone can send feedback to the E.G. directly. Feedback will be discussed on the main EG list. Co-spec lead Prof. Michael Ernst maintains an issue tracker and a document archive. Early-Access Builds of the Reference Implementation Oracle has published binaries for all platforms of JDK 8 with support for type annotations. Builds are generated from OpenJDK's type-annotations/type-annotations forest (notably the langtools repo). The forest is owned by the Type Annotations project. Integration with Enhanced Metadata On the enhanced metadata mailing list, Oracle has proposed support for repeating annotations in the Java language in Java SE 8. For completeness, it must be possible to repeat annotations on types, not only on declarations. The implementation of repeating annotations on declarations is already in the type-annotations/type-annotations forest (and hence in the early-access builds above) and work is underway to extend it to types.

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• What makes one language any better than another when both are designed for the same goals? [closed]

  - by Justin808

  I'm in the process of creating a grammar for a scripting language but as I'm working on it I started to wonder what makes a language good in the first place. I know the goals for my script but there are always 1000 different ways to go about doing things. Goals: Easy to use and understand (not my grandma could do it easy, but the secretary at the front desk could do it or the VP of marketing could do it type of easy) No user defined functions or subroutines. Its use would be in events of objects in a system similar to HyperCard. Conceptually I was thinking of a language like this: set myVariable to 'Hello World' set counter to 0 repeat 5 times with x begin set counter to counter add x end set myVariable to myVariable plus ' ' plus counter popup myVariable set text of label named 'label' to 'new text' set color of label named 'label' to blue The end result would popup a dialog with the contents Hello World 15 it would also change the text of a label and make it blue. But I could do the same thing 1000 different ways. So what makes one language any better than another when both are designed for the same goals?

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• Handling commands or events that wait for an action to be completed afterwards

  - by virulent

  Say you have two events: Action1 and Action2. When you receive Action1, you want to store some arbitrary data to be used the next time Action2 rolls around. Optimally, Action1 is normally a command however it can also be other events. The idea is still the same. The current way I am implementing this is by storing state and then simply checking when Action2 is called if that specific state is there. This is obviously a bit messy and leads to a lot of redundant code. Here is an example of how I am doing that, in pseudocode form (and broken down quite a bit, obviously): void onAction1(event) { Player = event.getPlayer() Player.addState("my_action_to_do") } void onAction2(event) { Player = event.getPlayer() if not Player.hasState("my_action_to_do") { return } // Do something } When doing this for a lot of other actions it gets somewhat ugly and I wanted to know if there is something I can do to improve upon it. I was thinking of something like this, which wouldn't require passing data around, but is this also not the right direction? void onAction1(event) { Player = event.getPlayer() Player.onAction2(new Runnable() { public void run() { // Do something } }) } If one wanted to take it even further, could you not simply do this? void onPlayerEnter(event) { // When they join the server Player = event.getPlayer() Player.onAction1(new Runnable() { public void run() { // Now wait for action 2 Player.onAction2(new Runnable() { // Do something }) } }, true) // TRUE would be to repeat the event, // not remove it after it is called. } Any input would be wonderful.

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• What's is the point of PImpl pattern while we can use interface for same purpose in C++?

  - by ZijingWu

  I see a lot of source code which using PIMPL idiom in C++. I assume Its purposes are hidden the private data/type/implementation, so it can resolve dependence, and then reduce compile time and header include issue. But interface class in C++ also have this capability, it can also used to hidden data/type and implementation. And to hidden let the caller just see the interface when create object, we can add an factory method in it declaration in interface header. The comparison is: Cost: The interface way cost is lower, because you doesn't even need to repeat the public wrapper function implementation void Bar::doWork() { return m_impl->doWork(); }, you just need to define the signature in the interface. Well understand: The interface technology is more well understand by every C++ developer. Performance: Interface way performance not worse than PIMPL idiom, both an extra memory access. I assume the performance is same. Following is the pseudocode code to illustrate my question: // Forward declaration can help you avoid include BarImpl header, and those included in BarImpl header. class BarImpl; class Bar { public: // public functions void doWork(); private: // You doesn't need to compile Bar.cpp after change the implementation in BarImpl.cpp BarImpl* m_impl; }; The same purpose can be implement using interface: // Bar.h class IBar { public: virtual ~IBar(){} // public functions virtual void doWork() = 0; }; // to only expose the interface instead of class name to caller IBar* createObject(); So what's the point of PIMPL?

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• Vote for bugs which impact you!

  - by Sveta Smirnova

  Matt Lord already announced this change, but I am so happy, so want to repeat. MySQL Community Bugs Database Team introduced new button "Affects Me". After you click this button, counter, assigned to each of bug reports, will increase by one. This means we: MySQL Support and Engineering, - will see how many users are affected by the bug. Why is this important? We have always considered community input as we prioritize bug fixes, and this is one more point of reference for us. Before this change we only had a counter for support customers which increased when they opened a support request, complaining they are affected by a bug. But our customers are smart and not always open support request when hit a bug: sometimes they simply implement workaround. Or there could be other circumstances when they don't create a ticket. Or this could be just released version, which big shops frighten to use in production. Therefore, sometimes, when discussing which bug to prioritize and which not we can not rely only on "Affects paying customers" number, rather need to make guess if one or another bug can affect large group of our users. We used number of bug report subscribers, most recent comments, searched forums, but all these methods gave only approximation. Therefore I want to ask you. If you hit a bug which already was reported, but not fixed yet, please click "Affects Me" button! It will take just a few seconds, but your voice will be heard.

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• What's a good algorithm for a random, uneven distribution of a fixed amount of a resource?

  - by NickC

  Problem I have X, a positive integer, of some resource, R. There are N potential targets. I want to distribute all of R to the N targets in some "interesting" way. "Interesting" means: Some targets may not get any R. It should rarely be near even (with a majority of target getting near X/N of the resource). There should be at least a small chance of one target getting all of R. Bad solutions The naive approach would be to pick a random target and give one R to it and repeat X times. This would result in too even of an approach. The next idea is to pick a random number between 1 and X and give it to a random target. This results in too large of a number (at least X/2 on average) being given to one target. Question This algorithm will be used frequently and I want the distribution to be interesting and uneven so that the surprise doesn't wear off for users. Is there a good algorithm for something in between these two approaches, that fits the definition of interesting above?

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• How to manually patch Blogger template to use Disqus

  - by user317944

  I'm trying to add disqus to my blog and I tried following this guide to do so: http://disqus.com/docs/patch-blogger/ However their instructions are completely off with what I have on my custom template. Here is the template: <b:skin><![CDATA[/*----------------------------------------------- Blogger Template Style Name: Picture Window Designer: Josh Peterson URL: www.noaesthetic.com ----------------------------------------------- */ /* Variable definitions ==================== */ /* Content ----------------------------------------------- */ body { font: $(body.font); color: $(body.text.color); } html body .region-inner { min-width: 0; max-width: 100%; width: auto; } .content-outer { font-size: 90%; } a:link { text-decoration:none; color: $(link.color); } a:visited { text-decoration:none; color: $(link.visited.color); } a:hover { text-decoration:underline; color: $(link.hover.color); } .body-fauxcolumn-outer { background: $(body.background); } .content-outer { background: $(content.background); -moz-border-radius: $(content.border.radius); -webkit-border-radius: $(content.border.radius); -goog-ms-border-radius: $(content.border.radius); border-radius: $(content.border.radius); -moz-box-shadow: 0 0 $(content.shadow.spread) rgba(0, 0, 0, .15); -webkit-box-shadow: 0 0 $(content.shadow.spread) rgba(0, 0, 0, .15); -goog-ms-box-shadow: 0 0 $(content.shadow.spread) rgba(0, 0, 0, .15); box-shadow: 0 0 $(content.shadow.spread) rgba(0, 0, 0, .15); margin: $(content.margin) auto; } .content-inner { padding: $(content.padding); } /* Header ----------------------------------------------- */ .header-outer { background: $(header.background.color) $(header.background.gradient) repeat-x scroll top left; _background-image: none; color: $(header.text.color); -moz-border-radius: $(header.border.radius); -webkit-border-radius: $(header.border.radius); -goog-ms-border-radius: $(header.border.radius); border-radius: $(header.border.radius); } .Header img, .Header #header-inner { -moz-border-radius: $(header.border.radius); -webkit-border-radius: $(header.border.radius); -goog-ms-border-radius: $(header.border.radius); border-radius: $(header.border.radius); } .header-inner .Header .titlewrapper, .header-inner .Header .descriptionwrapper { padding-left: $(header.padding); padding-right: $(header.padding); } .Header h1 { font: $(header.font); text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.3); } .Header h1 a { color: $(header.text.color); } .Header .description { font-size: 130%; } /* Tabs ----------------------------------------------- */ .tabs-inner { margin: .5em $(tabs.margin.sides) $(tabs.margin.bottom); padding: 0; } .tabs-inner .section { margin: 0; } .tabs-inner .widget ul { padding: 0; background: $(tabs.background.color) $(tabs.background.gradient) repeat scroll bottom; -moz-border-radius: $(tabs.border.radius); -webkit-border-radius: $(tabs.border.radius); -goog-ms-border-radius: $(tabs.border.radius); border-radius: $(tabs.border.radius); } .tabs-inner .widget li { border: none; } .tabs-inner .widget li a { display: block; padding: .5em 1em; margin-$endSide: $(tabs.spacing); color: $(tabs.text.color); font: $(tabs.font); -moz-border-radius: $(tab.border.radius) $(tab.border.radius) 0 0; -webkit-border-top-left-radius: $(tab.border.radius); -webkit-border-top-right-radius: $(tab.border.radius); -goog-ms-border-radius: $(tab.border.radius) $(tab.border.radius) 0 0; border-radius: $(tab.border.radius) $(tab.border.radius) 0 0; background: $(tab.background); border-$endSide: 1px solid $(tabs.separator.color); } .tabs-inner .widget li:first-child a { padding-$startSide: 1.25em; -moz-border-radius-top$startSide: $(tab.first.border.radius); -moz-border-radius-bottom$startSide: $(tabs.border.radius); -webkit-border-top-$startSide-radius: $(tab.first.border.radius); -webkit-border-bottom-$startSide-radius: $(tabs.border.radius); -goog-ms-border-top-$startSide-radius: $(tab.first.border.radius); -goog-ms-border-bottom-$startSide-radius: $(tabs.border.radius); border-top-$startSide-radius: $(tab.first.border.radius); border-bottom-$startSide-radius: $(tabs.border.radius); } .tabs-inner .widget li.selected a, .tabs-inner .widget li a:hover { position: relative; z-index: 1; background: $(tabs.selected.background.color) $(tab.selected.background.gradient) repeat scroll bottom; color: $(tabs.selected.text.color); -moz-box-shadow: 0 0 $(region.shadow.spread) rgba(0, 0, 0, .15); -webkit-box-shadow: 0 0 $(region.shadow.spread) rgba(0, 0, 0, .15); -goog-ms-box-shadow: 0 0 $(region.shadow.spread) rgba(0, 0, 0, .15); box-shadow: 0 0 $(region.shadow.spread) rgba(0, 0, 0, .15); } /* Headings ----------------------------------------------- */ h2 { font: $(widget.title.font); text-transform: $(widget.title.text.transform); color: $(widget.title.text.color); margin: .5em 0; } /* Main ----------------------------------------------- */ .main-outer { background: $(main.background); -moz-border-radius: $(main.border.radius.top) $(main.border.radius.top) 0 0; -webkit-border-top-left-radius: $(main.border.radius.top); -webkit-border-top-right-radius: $(main.border.radius.top); -webkit-border-bottom-left-radius: 0; -webkit-border-bottom-right-radius: 0; -goog-ms-border-radius: $(main.border.radius.top) $(main.border.radius.top) 0 0; border-radius: $(main.border.radius.top) $(main.border.radius.top) 0 0; -moz-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); -webkit-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); -goog-ms-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); } .main-inner { padding: 15px $(main.padding.sides) 20px; } .main-inner .column-center-inner { padding: 0 0; } .main-inner .column-left-inner { padding-left: 0; } .main-inner .column-right-inner { padding-right: 0; } /* Posts ----------------------------------------------- */ h3.post-title { margin: 0; font: $(post.title.font); } .comments h4 { margin: 1em 0 0; font: $(post.title.font); } .post-outer { background-color: $(post.background.color); border: solid 1px $(post.border.color); -moz-border-radius: $(post.border.radius); -webkit-border-radius: $(post.border.radius); border-radius: $(post.border.radius); -goog-ms-border-radius: $(post.border.radius); padding: 15px 20px; margin: 0 $(post.margin.sides) 20px; } .post-body { line-height: 1.4; font-size: 110%; } .post-header { margin: 0 0 1.5em; color: $(post.footer.text.color); line-height: 1.6; } .post-footer { margin: .5em 0 0; color: $(post.footer.text.color); line-height: 1.6; } blog-pager { font-size: 140% } comments .comment-author { padding-top: 1.5em; border-top: dashed 1px #ccc; border-top: dashed 1px rgba(128, 128, 128, .5); background-position: 0 1.5em; } comments .comment-author:first-child { padding-top: 0; border-top: none; } .avatar-image-container { margin: .2em 0 0; } /* Widgets ----------------------------------------------- */ .widget ul, .widget #ArchiveList ul.flat { padding: 0; list-style: none; } .widget ul li, .widget #ArchiveList ul.flat li { border-top: dashed 1px #ccc; border-top: dashed 1px rgba(128, 128, 128, .5); } .widget ul li:first-child, .widget #ArchiveList ul.flat li:first-child { border-top: none; } .widget .post-body ul { list-style: disc; } .widget .post-body ul li { border: none; } /* Footer ----------------------------------------------- */ .footer-outer { color:$(footer.text.color); background: $(footer.background); -moz-border-radius: $(footer.border.radius.top) $(footer.border.radius.top) $(footer.border.radius.bottom) $(footer.border.radius.bottom); -webkit-border-top-left-radius: $(footer.border.radius.top); -webkit-border-top-right-radius: $(footer.border.radius.top); -webkit-border-bottom-left-radius: $(footer.border.radius.bottom); -webkit-border-bottom-right-radius: $(footer.border.radius.bottom); -goog-ms-border-radius: $(footer.border.radius.top) $(footer.border.radius.top) $(footer.border.radius.bottom) $(footer.border.radius.bottom); border-radius: $(footer.border.radius.top) $(footer.border.radius.top) $(footer.border.radius.bottom) $(footer.border.radius.bottom); -moz-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); -webkit-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); -goog-ms-box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); box-shadow: 0 $(region.shadow.offset) $(region.shadow.spread) rgba(0, 0, 0, .15); } .footer-inner { padding: 10px $(main.padding.sides) 20px; } .footer-outer a { color: $(footer.link.color); } .footer-outer a:visited { color: $(footer.link.visited.color); } .footer-outer a:hover { color: $(footer.link.hover.color); } .footer-outer .widget h2 { color: $(footer.widget.title.text.color); } ]] <b:template-skin> <b:variable default='930px' name='content.width' type='length' value='930px'/> <b:variable default='0' name='main.column.left.width' type='length' value='180px'/> <b:variable default='360px' name='main.column.right.width' type='length' value='180px'/> <![CDATA[ body { min-width: $(content.width); } .content-outer, .region-inner { min-width: $(content.width); max-width: $(content.width); _width: $(content.width); } .main-inner .columns { padding-left: $(main.column.left.width); padding-right: $(main.column.right.width); } .main-inner .fauxcolumn-center-outer { left: $(main.column.left.width); right: $(main.column.right.width); /* IE6 does not respect left and right together */ _width: expression(this.parentNode.offsetWidth - parseInt("$(main.column.left.width)") - parseInt("$(main.column.right.width)") + 'px'); } .main-inner .fauxcolumn-left-outer { width: $(main.column.left.width); } .main-inner .fauxcolumn-right-outer { width: $(main.column.right.width); } .main-inner .column-left-outer { width: $(main.column.left.width); right: $(main.column.left.width); margin-right: -$(main.column.left.width); } .main-inner .column-right-outer { width: $(main.column.right.width); margin-right: -$(main.column.right.width); } #layout { min-width: 0; } #layout .content-outer { min-width: 0; width: 800px; } #layout .region-inner { min-width: 0; width: auto; } ]]> </b:template-skin> <div class='main-cap-bottom cap-bottom'> <div class='cap-left'/> <div class='cap-right'/> </div> </div> <footer> <div class='footer-outer'> <div class='footer-cap-top cap-top'> <div class='cap-left'/> <div class='cap-right'/> </div> <div class='fauxborder-left footer-fauxborder-left'> <div class='fauxborder-right footer-fauxborder-right'/> <div class='region-inner footer-inner'> <macro:include id='footer-sections' name='sections'> <macro:param default='2' name='num' value='3'/> <macro:param default='footer' name='idPrefix'/> <macro:param default='foot' name='class'/> <macro:param default='false' name='includeBottom'/> </macro:include> <!-- outside of the include in order to lock Attribution widget --> <b:section class='foot' id='footer-3' showaddelement='no'> document.body.className = document.body.className.replace('loading', ''); <macro:if cond='data:col.num &gt;= 2'> <table border='0' cellpadding='0' cellspacing='0' mexpr:class='&quot;section-columns columns-&quot; + data:col.num'> <tbody> <tr> <td class='first columns-cell'> <b:section mexpr:class='data:col.class' mexpr:id='data:col.idPrefix + &quot;-2-1&quot;'/> </td> <td class='columns-cell'> <b:section mexpr:class='data:col.class' mexpr:id='data:col.idPrefix + &quot;-2-2&quot;'/> </td> <macro:if cond='data:col.num &gt;= 3'> <td class='columns-cell'> <b:section mexpr:class='data:col.class' mexpr:id='data:col.idPrefix + &quot;-2-3&quot;'/> </td> </macro:if> <macro:if cond='data:col.num &gt;= 4'> <td class='columns-cell'> <b:section mexpr:class='data:col.class' mexpr:id='data:col.idPrefix + &quot;-2-4&quot;'/> </td> </macro:if> </tr> </tbody> </table> <macro:if cond='data:col.includeBottom'> <b:section mexpr:class='data:col.class' mexpr:id='data:col.idPrefix + &quot;-3&quot;' showaddelement='no'/> </macro:if> </macro

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• Content Container Overlaps Menu?

  - by Harold

  I'm currently working on a Joomla template using CSS divs. I have a header set up with our logo image in a div floated to the left, an adspace floated to the right, and the menu bar on the bottom. My content is divided into three div columns that are contained in "container.": the left column is floated left, the center is not floated, and the right is floated to the right. The problem is the "container" for the three content divs is overlapping the menu, as you can see in this image: http://www.ndpstudentcouncil.org/images/shot1.png Here's the HTML code: > <body> <div id="backdrop"> <div > id="wrapper"> <div id="header"> > <div id="topimage"> </div> > <div id="adspace1"><jdoc:include > type="modules" name="Ad Space #1" /> > This will be the location for our > "newsflash" items. </div> > > <div id="ddtopmenubar" > class="mattblackmenu"> > <ul> > <li><a href="http://www.ndpstudentcouncil.org">Home</a></li> > <li><a href="http://www.dynamicdrive.com/new.htm" rel="ddsubmenu1">DHTML</a></li> > <li><a href="http://www.dynamicdrive.com/style/" > rel="ddsubmenu2">CSS</a></li> > <li><a href="http://www.dynamicdrive.com/forums/">Forums</a></li> > <li><a href="http://tools.dynamicdrive.com/" > rel="ddsubmenu3">Web Tools</a></li> > </ul> > <script type="text/javascript" src="js/ddlevelsmenu.js"> > ddlevelsmenu.setup("ddtopmenubar", "topbar") > //ddlevelsmenu.setup("mainmenuid", > "topbar|sidebar") > </script> > <ul id="ddsubmenu1" class="ddsubmenustyle"> > <li><a href="#">Item 1a</a></li> > <li><a href="#">Item 2a</a></li> > <li><a href="#">Item Folder 3a</a> > <ul> > <li><a href="#">Sub Item 3.1a</a></li> > </ul> > </li> > <li><a href="#">Item 4a</a></li> > <li><a href="#">Item Folder 5a</a> > <ul> > <li><a href="#">Sub Item 5.1a</a></li> > <li><a href="#">Item Folder 5.2a</a> > <ul> > <li><a href="#">Sub Item 5.2.1a</a></li> > <li><a href="#">Sub Item 5.2.2a</a></li> > </ul> > </li> > </ul> > </a> > </li> > <li><a href="#">Item 6a</a></li> > </ul> </div> </div> > <div id="container"> <script language="javascript"> > matchHeight=function(){ > var divs,contDivs,maxHeight,divHeight,d; > // get all <div> elements in the document > divs=document.getElementsByTagName('div'); > contDivs=[]; > // initialize maximum height value > maxHeight=0; > // iterate over all <div> elements in the document > for(var i=0;i<divs.length;i++){ > // make collection with <div> elements with class attribute > 'container' > if(/\bcontainer\b/.test(divs[i].className)){ > d=divs[i]; > contDivs[contDivs.length]=d; > // determine height for <div> element > if(d.offsetHeight){ > divHeight=d.offsetHeight; > } > else if(d.style.pixelHeight){ > divHeight=d.style.pixelHeight; > } > // calculate maximum height > maxHeight=Math.max(maxHeight,divHeight); > } > } > // assign maximum height value to all of container <div> elements > for(var i=0;i<contDivs.length;i++){ > contDivs[i].style.height=maxHeight; > } > } > // execute function when page loads > window.onload=function(){ > if(document.getElementsByTagName){ > matchHeight(); > } > } > </script> <div id="left"> > <jdoc:include type="modules" name="left" /> </div> <div > id="middle"> > <jdoc:include type="component" /> </div> <div id="right"> > <jdoc:include type="modules" name="right" /> > </div> > </div> > <div id="footer" class="clear"><jdoc:include > type="modules" name="footer" /> > &copy; 2010 NDP Student Council<br > />Website Development Subcommitee > </div> </div> </div> </body> The CSS: > #backdrop { width:100%; height:100%; background: #FFFFFF > url(../images/gradient.jpg) repeat-x; > } > > #wrapper { margin:auto; width:95%; height:95%; border-right:thick solid > black; border-bottom:thick solid > black; border-top:thick solid black; > border-left:thick solid black; > background-color:white; } > > #header { height:131px; width:100%; background-color: #FFFFFF; > border-bottom:thick solid black; } > > #topimage { float:left; height:131px; width:63%; > background-image: > url("../images/ndps2.png"); > background-repeat:no-repeat; } > > #adspace1 { float:right; width:27%; height:131px; } > > #container { clear:both; } > #left{ width:20%; float:left; padding:5px; text-align:center; } > > #middle{ width:60%; padding:5px; text-align:center; } > > #right{ float:right; width:20%; padding:5px; text-align:right; } > #footer { border-top:thick solid black; width:100%; > text-align:center; } .clear { > clear:both; } Here is the CSS for the menu itself, which is from DynamicDrive.com: > .mattblackmenu ul{ margin: 0; padding: > 0; font: bold 12px Verdana; > list-style-type: none; border-bottom: > 1px solid gray; background: #414141; > overflow: hidden; width: 100%; > clear:both; } > > .mattblackmenu li{ display: inline; > margin: 0; } > > .mattblackmenu li a{ float: left; > display: block; text-decoration: none; > margin: 0; padding: 6px 8px; /*padding > inside each tab*/ border-right: 1px > solid white; /*right divider between > tabs*/ color: white; background: > #414141; Thanks for the help!

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• AngularJS databinding

  - by user3652865

  How can I add multiple values to one object in an Array. I am having Environment and Cluster, I am able to assign multiple clusters to one environment. Now I want to add application name to this environment and cluster pair. I am having page called "Add Application". Here I am using select menu to for environment and Cluster. My first question is, when I select environment then want to show only those clusters which are assigned to that environment name. And assign application name to that pair. Also should be able to edit the Application field. I am using environmentServices and clusterServices to store updated data. link of JSFiddle: http://jsfiddle.net/avinashMaddy/J2KLK/5/ Please if someone can help me in this. Below is my code: <div class="maincontent" ng-controller="manageApplicationController"> <div class="article"> <form> <section> <!-- Environment --> <div class="col-md-4"> <label>Environment:</label> <select ng-model="newApp.selectedEnvironment" class="form-control" ng-options="environment.name for environment in environments"> <option value='' disabled style='display:none;'> Select Environment </option> </select> <span> <select ng-switch-when="true" disabled ng-model="newApp.selectedEnvironment" class="form-control" ng-options="environment.name for environment in environments"> <option value='' disabled style='display:none;'> Select Environment </option> </select> </span> </div> <!-- Cluster --> <div class="col-md-4"> <label>Cluster:</label> <span ng-switch on="newApp.showCancel"> <select ng-switch-default ng-model="newApp.selectedCluster" class="form-control" ng-options="cluster for cluster in clusters"> <option value='' disabled style='display:none;'> Select Environment </option> </select> <select ng-switch-when="true" disabled ng-model="newApp.selectedCluster" class="form-control" ng-options="cluster for cluster in clusters"> <option value='' disabled style='display:none;'> Select Environment </option> </select> </span> </div> <!-- Application Name --> <div class="col-md-4"> <label>Application Name:</label> <input type="text" class="form-control" name="applicationName" placeholder="Application" ng-model="app.name" required> <br/> <input type="hidden" ng-model="app.id" /> </div> </section> <!-- submit button --> <section class="col-md-12"> <button type="button" class="btn btn-default pull-right" ng-click="saveNewApplicatons()">Save</button> </section> </form> </div> <!-- table --> <div class="article"> <table class="table table-bordered table-striped"> <tr> <th colspan="6"> <div class="pull-left">Cluster Info</div> </th> </tr> <tr> <th>Environment</th> <th>Cluster</th> <th>Application</th> <th>Edit</th> <th>Header Ifo</th> </tr> <tr ng-repeat="app in applications"> <td>{{app.environment}}</td> <td>{{app.cluster}}</td> <td>{{app.name}}</td> <td> <a href="" ng-click="edit(app.id)" title="Edit">edit</span></a> | <a href="" ng-click="remove(app.id)" title="Delete">delete</a> </td> <td> <!-- Add template --> <script type="text/ng-template" id="addHederInfo.html"> <div class="modal-header"> <h3>Add Header Info</h3> </div> <div class="modal-body"> <input type="text" class="form-control" name="eName" placeholder="Header Key" ng-model="$parent.header.key"> <br/> <input type="text" class="form-control" name="eName" placeholder="Header Value" ng-model="$parent.header.value"> <br /> <input type="hidden" ng-model="header.id" /> <section> <div class="pull-right"> <button class="btn btn-primary" ng-click="saveHeader()">Add</button> <button class="btn btn-warning" ng-click="cancel()">Close</button> </div> </section> </div> <div class="modal-footer"> <h3>Existing Header Info for </h3> <table class="table table-bordered table-striped"> <tr> <th>Header Key</th> <th>Header Vlaue</th> </tr> <tr ng-repeat="header in headers"> <td>{{header.key}}</td> <td>{{header.value}}</td> </tr> </table> </div> </script> <!-- /Add template --> <script type="text/ng-template" id="editHederInfo.html"> <div class="modal-header"> <h3>Edit Header Info</h3> </div> <div class="modal-body"> <input type="text" class="form-control" name="eName" placeholder="Header Key" ng-model="$parent.header.key"> <br/> <input type="text" class="form-control" name="eName" placeholder="Header Value" ng-model="$parent.header.value"> <br /> <input type="hidden" ng-model="header.id" /> <section> <div class="pull-right"> <button class="btn btn-primary" ng-click="saveHeader()">Update</button> <button class="btn btn-warning" ng-click="cancel()">Close</button> </div> </section> </div> <div class="modal-footer"> <h3>Existing Header Info for</h3> <table class="table table-bordered table-striped"> <tr> <th>Header Key</th> <th>Header Vlaue</th> <th>Edit</th> </tr> <tr ng-repeat="header in headers"> <td>{{header.key}}</td> <td>{{header.value}}</td> <td> <a href="" ng-click="editHeader(header.id)" title="Edit"><span class="glyphicon glyphicon-edit" ></span></a> | <a href="" ng-click="removeHeader(header.id)" title="Edit"><span class="glyphicon glyphicon-trash"></span></a> </td> </tr> </table> </div> </script> <!-- Add template --> <!-- /Add template --> <a href="" ng-click="addInfo()">Add</a> | <a href="" ng-click="editInfo()">Edit</a> </td> </tr> </table> </div> </div> Controller.js: var apsApp = angular.module('apsApp', []); apsApp.service('clusterService', function(){ var clusters=[]; //simply returns the environment list this.list = function () { return clusters; }; }); apsApp.service('environmentService', function(){ var environments=[ {name :'DEV',}, {name:'PROD',}, {name:'QA',}, {name:'Linux_Dev',} ]; //simply returns the environment list this.list = function () { return environments; }; apsApp.controller('manageApplicationController', function ($scope, environmentService, clusterService) { var uid = 0; $scope.environments= environmentService.list(); $scope.clusters= clusterService.list(); $scope.newApp = {}; $scope.newApp.selectedEnvironment = $scope.environments[0]; $scope.newApp.selectedCluster = $scope.clusters[0]; $scope.newApp.buttonLabel = 'Save'; $scope.newApp.showCancel = false; /*$scope.applications=[ {'name': 'Enterprice App Store' }, {'name': 'UsageGateway'}, {'name': 'Click 2 Fill'}, {'name': 'ATT SmartWiFi'} ];*/ //add new application $scope.saveNewApplicatons = function() { if ($scope.select.id == undefined) { //if this is new application, add it in applications array $scope.clusters.push({ id: uid++, cluster: $scope.newApp.cluster, environment: $scope.newApp.selectedEnvironment }); } else { $scope.clusters[$scope.select.id].cluster = $scope.select.cluster; $scope.newApp.id = undefined; $scope.newApp.buttonLabel = 'Save Cluster'; $scope.newApp.showCancel = false; }; //clear the add appplicaitons form $scope.newApp.selectedEnvironment = $scope.environments[0]; }; //delete application $scope.remove = function (id) { //search app with given id and delete it for (i in $scope.clusters) { if ($scope.clusters[i].id == id) { confirm("This Cluster will get deleted permanently"); $scope.clusters.splice(i, 1); $scope.clust = {}; } } }; $scope.cancelUpdate = function () { $scope.newApp.buttonLabel = 'Save Cluster'; $scope.newApp.showCancel = false; $scope.newApp.id = undefined; $scope.newApp.cluster = ""; $scope.newApp.selectedEnvironment = $scope.environments[0]; }; });

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• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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