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• How can I gather client's data on Google App Engine without using Datastore/Backend Instances too much?

  - by ruslan

  One of the projects I'm working on is online survey engine. It's my first big commercial project on Google App Engine. I need your advice on how to collect stats and efficiently record them in DataStore without bankrupting me. Initial requirements are: After user finishes survey client sends list of pairs [ID (int) + PercentHit (double)]. This list shows how close answers of this user match predefined answers of reference answerers (which identified by IDs). I call them "target IDs". Creator of the survey wants to see aggregated % for given IDs for last hour, particular timeframe or from the beginning of the survey. Some surveys may have thousands of target/reference answerers. So I created entity public class HitsStatsDO implements Serializable { @Id transient private Long id; transient private Long version = (long) 0; transient private Long startDate; @Parent transient private Key parent; // fake parent which contains target id @Transient int targetId; private double avgPercent; private long hitCount; } But writing HitsStatsDO for each target from each user would give a lot of data. For instance I had a survey with 3000 targets which was answered by ~4 million people within one week with 300K people taking survey in first day. Even if we assume they were answering it evenly for 24 hours it would give us ~1040 writes/second. Obviously it hits concurrent writes limit of Datastore. I decided I'll collect data for one hour and save that, that's why there are avgPercent and hitCount in HitsStatsDO. GAE instances are stateless so I had to use dynamic backend instance. There I have something like this: // Contains stats for one hour private class Shard { ReadWriteLock lock = new ReentrantReadWriteLock(); Map<Integer, HitsStatsDO> map = new HashMap<Integer, HitsStatsDO>(); // Key is target ID public void saveToDatastore(); public void updateStats(Long startDate, Map<Integer, Double> hits); } and map with shard for current hour and previous hour (which doesn't stay here for long) private HashMap<Long, Shard> shards = new HashMap<Long, Shard>(); // Key is HitsStatsDO.startDate So once per hour I dump Shard for previous hour to Datastore. Plus I have class LifetimeStats which keeps Map<Integer, HitsStatsDO> in memcached where map-key is target ID. Also in my backend shutdown hook method I dump stats for unfinished hour to Datastore. There is only one major issue here - I have only ONE backend instance :) It raises following questions on which I'd like to hear your opinion: Can I do this without using backend instance ? What if one instance is not enough ? How can I split data between multiple dynamic backend instances? It hard because I don't know how many I have because Google creates new one as load increases. I know I can launch exact number of resident backend instances. But how many ? 2, 5, 10 ? What if I have no load at all for a week. Constantly running 10 backend instances is too expensive. What do I do with data from clients while backend instance is dead/restarting?

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• Algorithms or patterns for a linked question and answer cost calculator

  - by kmc

  I've been asked to build an online calculator in PHP (and the Laravel framework). It will take the answers to a series of questions to estimate the cost of a home extension. For example, a couple of questions may be: What is the lie of your property? Flat, slightly inclined, heavily inclined. (these suggestive values could have specific values in the underlying calculator like, 0 degrees, 5 degrees, 10 degrees. What is your current flooring system? Wooden, or concrete? These would then impact the results of other questions. Once the size of the extension has been input, the lie of the land will affect how much site works will cost, and how much rubbish collection will cost. The second question will impact the cost of the extensions flooring, as stumping and laying floorboards is a different cost to laying foundations and a concrete slab. It will also influence what heating and cooling systems are available in the calculator. So it's VERY interlinked. The answer to any question can influence the options of other questions, and the end result. I'm having trouble figuring out an approach to this that will allow new options and questions to be plugged in at a later stage without having things too coupled. The Observer pattern, or Laravel's events may be handy, but currently the sheer breadth of the calculator has me struggling to gather my thoughts and see a sensible implementation. Are there any patterns or OO approaches that may help? Thanks!

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• Should I cache the data or hit the database?

  - by JD01

  I have not worked with any caching mechanisms and was wondering what my options are in the .net world for the following scenario. We basically have a a REST Service where the user passes an ID of a Category (think folder) and this category may have lots of sub categories and each of the sub categories could have 1000 of media containers (think file reference objects) which contain information about a file that may be on a NAS or SAN server (files are videos in this case). The relationship between these categories is stored in a database together with some permission rules and meta data about the sub categories. So from a UI perspective we have a lazy loaded tree control which is driven by the user by clicking on each sub folder (think of Windows explorer). Once they come to a URL of the video file, they then can watch the video. The number of users could grow into the 1000s and the sub categories and videos could be in the 10000s as the system grows. The question is should we carry on the way it is currently working where each request hits the database or should we think about caching the data? We are on using IIS 6/7 and Asp.net.

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• Why do programming languages allow shadowing/hiding of variables and functions?

  - by Simon

  Many of the most popular programming languges (such as C++, Java, Python etc.) have the concept of hiding / shadowing of variables or functions. When I've encountered hiding or shadowing they have been the cause of hard to find bugs and I've never seen a case where I found it necessary to use these features of the languages. To me it would seem better to disallow hiding and shadowing. Does anybody know of a good use of these concepts?

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• Recommendations for a web-based help system

  - by ggkmath

  Hi Experts, I'm putting together a fairly large GUI. I'm a tech person, but more on the hardware side, not software. I'm wondering what software package would be best suited to enable me to generate a web-based help-system. Preferably it takes care of a lot of coding, allowing me to focus on the content. For example, the user would click on a link in the GUI when they have a question, that brings them to a web-based Help Guide, for example, providing an overview of how to use the GUI, perhaps a searchable index (key-word based index), table of contents, etc, for navigating through the Help Guide. My first thought was to program everything in XHTML using Dreamweaver, but my layout requirements are fairly modest (just figures and text, maybe a few equations), and I'd prefer not to spend a lot of time concentrating on the programming. Was wondering if any software existed that made generating web-based navigatable pages easy to create/publish. Again, I'm not really a programmer, so if there's something obvious out there, I'm probably not aware of it. Any advice much appreciated! Thanks in advance.

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• Game ideas for a platformer

  - by user5925

  I have created a platformer which currently has the features listed below. I would greatly appreciate any further ideas which I could implement! (I don't play a lot of games which is why I require help) -- Walking/jumping/movement -- player can shoot lasers -- enemies also walk, fly, and shoot lasers -- water (you can swim in this) -- mud (slows you down on contact, and stops you from jumping) -- ladders -- damage when falling from a large height, unless falling into water -- moving platforms -- springboards (jumping on them shoot you into the air) -- growing platforms (allow you to reach new places) -- key and door system -- gem and coin collection system

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• What browser do you build in? [closed]

  - by Ryan

  Lately I have been using Chrome, but I am starting to think I should use FF. What are the advantages and disadvantages of the various mainstream browsers (with an emphasis on Chrome and FF) when doing web development? Is it easier to start with clean code for a relatively conforming browser, and later add hacks/workarounds for acceptable display with less conforming browsers, or is it easier to work with a variety of browsers from the beginning, so we never have a page that's completely unacceptable with, for example, IE 6?

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• Logarithmic spacing of FFT subbands

  - by Mykel Stone

  I'm trying to do the examples within the GameDev.net Beat Detection article ( http://archive.gamedev.net/archive/reference/programming/features/beatdetection/index.html ) I have no issue with performing a FFT and getting the frequency data and doing most of the article. I'm running into trouble though in the section 2.B, Enhancements and beat decision factors. in this section the author gives 3 equations numbered R10-R12 to be used to determine how many bins go into each subband: R10 - Linear increase of the width of the subband with its index R11 - We can choose for example the width of the first subband R12 - The sum of all the widths must not exceed 1024 He says the following in the article: "Once you have equations (R11) and (R12) it is fairly easy to extract 'a' and 'b', and thus to find the law of the 'wi'. This calculus of 'a' and 'b' must be made manually and 'a' and 'b' defined as constants in the source; indeed they do not vary during the song." However, I cannot seem to understand how these values are calculated...I'm probably missing something simple, but learning fourier analysis in a couple of weeks has left me Decimated-in-Mind and I cannot seem to see it.

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• Making Class Diagram for MVC Pattern Project

  - by iMohammad

  I have a question about making a class diagram for an MVC based college senior project. If we have 2 actors of users in my system, lets say Undergrad and Graduate students are the children of abstract class called User. (Generalisation) Each actor has his own features. My question, in such case, do we need to have these two actors in separate classes which inherits from the abstract class User? even though, I'm going to implement them as roles using one Model called User Model ? I think you can see my confusion here. I code using MVC pattern, but I've never made a class diagram for this pattern. Thank you in advance!

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• How should I structure my database to gain maximum efficiently in this scenario?

  - by Bob Jansen

  I'm developing a PHP script that analyzes the web traffic of my clients websites. By placing a link to a javascript on the clients website (think of Google Analyses), my script harvests information like: the visitors IP address, reference link, current page link, user agent, etc. Now my clients can view these statistics via a control panel that I have build. These clients can also adjust profile settings, set firewall rules, create support tickets and pay invoices. Currently all the the traffic is stored in one table. You can imagine that this tabel would become very large as some my clients receive thousands of pageviews per day. Furthermore, all the traffic data of each client would be stored in the same table, creating a mess. This is the same for the firewall rules currently, and the invoice and support system. I'm looking for way to structure my database in a more organized way to hold large amounts of data of multiple users. This is the first project that I'm developing that deals with so much data, and would like to hear suggestions and tips. I was thinking of using multiple databases to structure the data. The main database will store users data (email,pass,id,etc) admin/website settings. Than each client will have an unique database labeled prefix_userid, which carry tables holding their traffic, invoice, and support ticket data. Would this be a solution, and would it slow down or speed up overall performances (that is spreading the data over muliple databases). I have a solid VPS, but would like to safe and be as effient as possible.

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• High resolution graphical representation of the Earth's surface

  - by Simon

  I've got a library, which I inherited, which presents a zoomable representation of the Earth. It's a Mercator projection and is constructed from triangles, the properties of which are stored in binary files. The surface is built up, for any given view port, by drawing these triangles in an overlapping fashion to produce the image. The definition of each triangle is the lat/long of the vertices. It looks OK at low values of zoom but looks progressively more ragged as the user zooms in. The view ports are primarily referenced though a rectangle of lat/long co-ordinates. I'd like to replace it with a better quality approach. The problem is, I don't know where to begin researching the options as I am not familiar either with the projections needed nor the graphics techniques used to render them. For example, I imagine that I could acquire high resolution images, say Mercator projections although I'm open to anything, break them into tiles and somehow wrap them onto a graphical representation of a sphere. I'm not asking for "how do I", more where should I begin to understand what might be involved and the techniques I will need to learn. I am most grateful for any "Earth rendering 101" pointers folks might have.

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• Service Layer - how broad should it be, and should it be used also on the local application?

  - by BornToCode

  Background: I need to build a main application with some operations (CRUD and more) (-in winforms), I need to make another application which will re-use some of the functions of the main application (-in webforms). I understood that using service layer is the best approach here. If I understood correctly the service should be calling the function on the BL layer (correct me if I'm wrong) The dilemma: In my main winform UI - should I call the functions from the BL, or from the service? (please explain why) Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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• Presenting Loading Data Warehouse Partitions with SSIS 2012 at SQL Saturday DC!

  - by andyleonard

  Join Darryll Petrancuri and me as we present Loading Data Warehouse Partitions with SSIS 2012 Saturday 8 Dec 2012 at SQL Saturday 173 in DC ! SQL Server 2012 table partitions offer powerful Big Data solutions to the Data Warehouse ETL Developer. In this presentation, Darryll Petrancuri and Andy Leonard demonstrate one approach to loading partitioned tables and managing the partitions using SSIS 2012, and reporting partition metrics using SSRS 2012. Objectives A practical solution for loading Big...(read more)

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• which style of member-access is preferable

  - by itwasntpete

  the purpose of oop using classes is to encapsulate members from the outer space. i always read that accessing members should be done by methods. for example: template<typename T> class foo_1 { T state_; public: // following below }; the most common doing that by my professor was to have a get and set method. // variant 1 T const& getState() { return state_; } void setState(T const& v) { state_ = v; } or like this: // variant 2 // in my opinion it is easier to read T const& state() { return state_; } void state(T const& v) { state_ = v; } assume the state_ is a variable, which is checked periodically and there is no need to ensure the value (state) is consistent. Is there any disadvantage of accessing the state by reference? for example: // variant 3 // do it by reference T& state() { return state_; } or even directly, if I declare the variable as public. template<typename T> class foo { public: // variant 4 T state; }; In variant 4 I could even ensure consistence by using c++11 atomic. So my question is, which one should I prefer?, Is there any coding standard which would decline one of these pattern? for some code see here

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• Is game development Subcontracted?

  - by Darv

  I was having a conversation with someone who believed that components of a games code where subcontracted out to programmers in different countries where it would be cheaper, then assembled by the local company. I understand that people often use pre-built engines but I would think that making the actual game would require people to work closely in the same studio. I couldn't find much clear information on this when I looked, does anyone know?

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• What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

  - by hal9k2

  As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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• How many tiers should my models have in a DB driven web app?

  - by Hanno Fietz

  In my experience, the "Model" in MVC is often not really a single layer. I would regularly have "backend" models and "frontend" models, where the backend ones would have properties that I want to hide from the UI code, and the frontend ones have derived or composite properties which are more meaningful in the context of the UI. Recently, I have started to introduce a third layer in between when database normalization created tables that did not really match the conceptual domain objects anymore. In those projects I have model classes that are equivalent with the DB structure, these become components of objects that represent the domain model, and finally these are filtered and amended for displaying information to the user. Are there patterns or guidelines for how, when and why to organize the data model across application layers?

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• How do I set an event off when player is on certain tile?

  - by Tom Burman

  Here is the code I use to create and print my map to the canvas: var board = []; function loadMap(map) { if (map == 1) { return [ [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,3,3,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,3,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,3,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,3,3,3,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,3,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,3,3,3,3,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2] ]; } } board = loadMap(1); enterfor (y = 0; y <= viewHeight; y++) { for (x = 0; x <= viewWidth; x++) { var theX = x * 32; var theY = y * 32; context.drawImage(mapTiles[board[y+viewY][x+viewX]], theX, theY, 32, 32); } } And here is the code I use for player movement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerX > 0) playerX--; break; case 38: // Up if (playerY > 0) playerY--; break; case 39: // Right if (playerX < worldWidth) playerX++; break; case 40: // Down if (playerY < worldHeight) playerY++; break; } viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; }, false); What I am looking for is a method for when the player lands on tile 3 he loses health. I have tried to use this in the player movement but it doesnt seem to work e.g the left movement: case 37: // Left if (playerX > 0) playerX--; if(board[x2 - 1] == 3) { health--; playerX--; }

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• Drawing large 2D sidescroller level terrain

  - by Yar

  I'm a relatively good programmer but now that it comes to add some basic levels to my 2D game I'm kinda stuck. What I want to do: An acceptable, large (8000 * 1000 pixels) "green hills" test level for my game. What is the best way for me to do this? It doesn't have to look great, it just shouldn't look like it was made in MS paint with the line and paint bucket tool. Basically it should just mud with grass on top of it, shaped in some form of hills. But how should I draw it, I can't just take out the pencil tool and start drawing it pixel per pixel, can I?

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• How URL Redirection affects SEO?

  - by Costa

  The following paragraph is from SEO Google Guide Google is good at crawling all types of URL structures, even if they're quite complex, but spending the time to make your URLs as simple as possible for both users and search engines can help. Some webmasters try to achieve this by rewriting their dynamic URLs to static ones; while Google is fine with this, we'd like to note that this is an advanced procedure and if done incorrectly, could cause crawling issues with your site. What makes URL re-writing implementation incorrect for GoogleBot? I am using Asp.net 3.5 framework. Thanks

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• Looping 3D environment in shmups

  - by kamziro

  So I was watching Ikaruga: http://www.youtube.com/watch?v=Aj23K8Ri68E And then raystorm: http://www.youtube.com/watch?v=TQ4V0G5ykAg After looking at their 3D backgrounds for a little bit, it appears that they use a lot of repeated segments. How would one start with the development with such systems? Would there be editors that can be used (or at least help) with creating the environments? Perhaps a 3D map with splines describing the path of the ship, as well as events on the splines?

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• Algorithmic Forecasting and Pattern Recognition

  - by Ryan King

  Say a user could enter project data into my software. Each project has 2 variables "size" and "work" and they're related but the relationship is not known. Is there a way to programmatically determine the relationship between the variables based on previous data and forecast the amount of work provided if only given the size of the project in the future? For Example, say the user had manually entered the following projects. Project 1 - Size:1, Work: 4 Project 2 - Size:2, Work: 7 Project 3 - Size:3, Work: 10 Project 4 - Size:4, Work: x What should I look into to be able to programmatically determine, that Work = Size*3+1 and therefor be able to say that x=13?

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• Breaking 1NF to model subset constraints. Does this sound sane?

  - by Chris Travers

  My first question here. Appologize if it is in the wrong forum but this seems pretty conceptual. I am looking at doing something that goes against conventional wisdom and want to get some feedback as to whether this is totally insane or will result in problems, so critique away! I am on PostgreSQL 9.1 but may be moving to 9.2 for this part of this project. To re-iterate: Does it seem sane to break 1NF in this way? I am not looking for debugging code so much as where people see problems that this might lead. The Problem In double entry accounting, financial transactions are journal entries with an arbitrary number of lines. Each line has either a left value (debit) or a right value (credit) which can be modelled as a single value with negatives as debits and positives as credits or vice versa. The sum of all debits and credits must equal zero (so if we go with a single amount field, sum(amount) must equal zero for each financial journal entry). SQL-based databases, pretty much required for this sort of work, have no way to express this sort of constraint natively and so any approach to enforcing it in the database seems rather complex. The Write Model The journal entries are append only. There is a possibility we will add a delete model but it will be subject to a different set of restrictions and so is not applicable here. If and when we allow deletes, we will probably do them using a simple ON DELETE CASCADE designation on the foreign key, and require that deletes go through a dedicated stored procedure which can enforce the other constraints. So inserts and selects have to be accommodated but updates and deletes do not for this task. My Proposed Solution My proposed solution is to break first normal form and model constraints on arrays of tuples, with a trigger that breaks the rows out into another table. CREATE TABLE journal_line ( entry_id bigserial primary key, account_id int not null references account(id), journal_entry_id bigint not null, -- adding references later amount numeric not null ); I would then add "table methods" to extract debits and credits for reporting purposes: CREATE OR REPLACE FUNCTION debits(journal_line) RETURNS numeric LANGUAGE sql IMMUTABLE AS $$ SELECT CASE WHEN $1.amount < 0 THEN $1.amount * -1 ELSE NULL END; $$; CREATE OR REPLACE FUNCTION credits(journal_line) RETURNS numeric LANGUAGE sql IMMUTABLE AS $$ SELECT CASE WHEN $1.amount > 0 THEN $1.amount ELSE NULL END; $$; Then the journal entry table (simplified for this example): CREATE TABLE journal_entry ( entry_id bigserial primary key, -- no natural keys :-( journal_id int not null references journal(id), date_posted date not null, reference text not null, description text not null, journal_lines journal_line[] not null ); Then a table method and and check constraints: CREATE OR REPLACE FUNCTION running_total(journal_entry) returns numeric language sql immutable as $$ SELECT sum(amount) FROM unnest($1.journal_lines); $$; ALTER TABLE journal_entry ADD CONSTRAINT CHECK (((journal_entry.running_total) = 0)); ALTER TABLE journal_line ADD FOREIGN KEY journal_entry_id REFERENCES journal_entry(entry_id); And finally we'd have a breakout trigger: CREATE OR REPLACE FUNCTION je_breakout() RETURNS TRIGGER LANGUAGE PLPGSQL AS $$ BEGIN IF TG_OP = 'INSERT' THEN INSERT INTO journal_line (journal_entry_id, account_id, amount) SELECT NEW.id, account_id, amount FROM unnest(NEW.journal_lines); RETURN NEW; ELSE RAISE EXCEPTION 'Operation Not Allowed'; END IF; END; $$; And finally CREATE TRIGGER AFTER INSERT OR UPDATE OR DELETE ON journal_entry FOR EACH ROW EXECUTE_PROCEDURE je_breaout(); Of course the example above is simplified. There will be a status table that will track approval status allowing for separation of duties, etc. However the goal here is to prevent unbalanced transactions. Any feedback? Does this sound entirely insane? Standard Solutions? In getting to this point I have to say I have looked at four different current ERP solutions to this problems: Represent every line item as a debit and a credit against different accounts. Use of foreign keys against the line item table to enforce an eventual running total of 0 Use of constraint triggers in PostgreSQL Forcing all validation here solely through the app logic. My concerns are that #1 is pretty limiting and very hard to audit internally. It's not programmer transparent and so it strikes me as being difficult to work with in the future. The second strikes me as being very complex and required a series of contraints and foreign keys against self to make work, and therefore it strikes me as complex, hard to sort out at least in my mind, and thus hard to work with. The fourth could be done as we force all access through stored procedures anyway and this is the most common solution (have the app total things up and throw an error otherwise). However, I think proof that a constraint is followed is superior to test cases, and so the question becomes whether this in fact generates insert anomilies rather than solving them. If this is a solved problem it isn't the case that everyone agrees on the solution....

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• What is the best wrapping strategy ?

  - by Riduidel

  Hi, I'm planning to integrate an external tool (ffmpeg in my particular case, but it could be anything, in fact, as lolng as its tasks are long running ones). This tool has a lot of command-line parameters. For now, I've done to simple things with it, already requiring me a good bunch of class writing, to embed all the information it can return to me. I now face the even more complex task of having to send it a bunch of parameters and to handle possible errors. So, what is a best way for that ? Create classes containing all possible options Relying upon a reverse equivalent of commons-cli / CliBuilder / OptionParser Directly write all options from user input Obiwan Kenobi powers (or anything I don't even know about) Please notice I do it in an uncommon language (for the sake of me, don't ask me what it is, as it looks like a desperate and sterile union between CoffeeScript and lua), as a consequence, there can be no framework doing what I want in the language I use.

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• Are programming languages pretty much "stable" for now?

  - by Sauron

  Recently i have looked at the "timeline" of Programming Languages and while a lot has changed in the past 5-10 years, there are a lot of languages that have pretty much "stayed" the same in their niche/use. For example, let's take C language. We don't really ever see much languages being developed (correct me if i'm wrong) to try to Unseat C. However, there are a lot of languages that try to do similar things (look at all the SQL/No-SQL languages) Scripting Languages, etc... Is there a reason for this trend? Or is it just because C was designed very well ? and there isn't really any need for new once?

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