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• Updating an ADF Web Service Data Control When Service Structure or Location Change

  - by Shay Shmeltzer

  The web service data control in Oracle ADF gives you a simplified approach to consuming services in ADF applications, and now with ADF Mobile the usage of this service seems to be growing. A frequent question we get is what happens if the service that I'm consuming changes - how do I update my data control? Well, first we should mention that if you do a good design of your application before you actually code - then things like Web service method signature shouldn't change. The signature is the contract between the publisher and the consumer, and contracts shouldn't be broken. But in reality things do change during development stages, so here is how you can update both method signatures and service location with the Web service data control: After watching this video you might be tempted to not copy the WSDLs to your project - which lets you use the right click update on a data control. However there is a reason why the copy is on by default, it reduces network traffic when you are actually running your application since ADF doesn't need to go to the server to find out the service structure. So for runtime performance, you probably should keep the WSDL local.  I encourage you to further look into both the connections.xml file where your service location is saved, and the datacontrols.dcx file where its definition is kept to get an even deeper understanding of how ADF works underneath the declarative layers.

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• Optimize Many-to-Many with SUMMARIZE and Other Techniques

  - by Marco Russo (SQLBI)

  We are still in the early days of DAX and even if I have been using it since 2 years ago, there is still a lot to learn on that. One of the topics that historically interests me (and many of the readers here, probably) is the many-to-many relationships between dimensions in a dimensional data model. When I and Alberto wrote the The Many to Many Revolution 2.0 we discovered the SUMMARIZE based pattern very late in the whitepaper writing. It is very important for performance optimization and it should be always used. In the last month, Gerhard Brueckl also presented an approach based on cross table filtering behavior that simplify the syntax involved, even if it’s harder to explain how it works internally. I published a short article titled Optimize Many-to-Many Calculation in DAX with SUMMARIZE and Cross Table Filtering on SQLBI website just to provide a quick reference to the three patterns available. A further study is still required to compare performance between SUMMARIZE and Cross Table Filtering patterns. Up to now, I haven’t observed big differences between them, even if their execution plans might be not identical and this suggest me that depending on other conditions you might favor one over the other.

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• GWB | Comment Spam On The Rise

  - by Geekswithblogs Administrator

  I don’t know a member on Geekswithblogs.net that is not frustrated with the amount of spam they get. It is a major problem that we have been dealing with for 6+ years and trying to come up with new ways to fight. As spammers get smarter, we have to continue to upgrade the tools we use to combat it. Just like any spam filter, sometimes good comments will get caught up. This has been a huge concern for some bloggers causing us to tame what we call spam and not spam. So this post is here just to state we know the spam problem is like a wave, sometimes it is not so bad, other times it gets worse. Right now it is worse. One measure we will take is a requirement for CAPTCHA soon if it continues since most members don’t clean up their spam via the admin tools (which are not the best tools, I know). Also I want to solicit a better approach from the members, what would you like the spam interface on GWB to be like? Be realistic cause we all want “Zero Spam, Good Comment live”. Related Tags: Geekswithblogs.net, Spam

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• Finding shapes in 2D Array, then optimising

  - by assemblism

  I'm new so I can't do an image, but below is a diagram for a game I am working on, moving bricks into patterns, and I currently have my code checking for rotated instances of a "T" shape of any colour. The X and O blocks would be the same colour, and my last batch of code would find the "T" shape where the X's are, but what I wanted was more like the second diagram, with two "T"s Current result      Desired Result [X][O][O]                [1][1][1] [X][X][_]                [2][1][_] [X][O][_]                [2][2][_] [O][_][_]                [2][_][_] My code loops through x/y, marks blocks as used, rotates the shape, repeats, changes colour, repeats. I have started trying to fix this checking with great trepidation. The current idea is to: loop through the grid and make note of all pattern occurrences (NOT marking blocks as used), and putting these to an array loop through the grid again, this time noting which blocks are occupied by which patterns, and therefore which are occupied by multiple patterns. looping through the grid again, this time noting which patterns obstruct which patterns That much feels right... What do I do now? I think I would have to try various combinations of conflicting shapes, starting with those that obstruct the most other patterns first.How do I approach this one? use the rational that says I have 3 conflicting shapes occupying 8 blocks, and the shapes are 4 blocks each, therefore I can only have a maximum of two shapes. (I also intend to incorporate other shapes, and there will probably be score weighting which will need to be considered when going through the conflicting shapes, but that can be another day) I don't think it's a bin packing problem, but I'm not sure what to look for. Hope that makes sense, thanks for your help

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• Data structure for bubble shooter game

  - by SundayMonday

  I'm starting to make a bubble shooter game for a mobile OS. Assume this is just the basic "three or more same-color bubbles that touch pop" and all bubbles that are separated from their group fall/pop. What data structures are common for storing the bubbles? I've considered using an undirected, connected graph where each node is a bubble. This seems like it could help answer the question "which bubbles (if any) should fall now?" after some arbitrary bubbles are popped and corresponding nodes are removed from the graph. I think the answer is all bubbles that were just disconnected from the graph should fall. However the graph approach might be overkill so I'm not sure. Another consideration for the data structure is collision detection. Perhaps being able to grab a list of neighboring bubbles in constant time for a particular "bubble slot" is useful. So the collision detection would be something like "moving bubble is closest to slot ij, neighbors of slot ij are bubbles a,b,c, moving bubble is sufficiently close to bubble b hence moving bubble should come to rest in slot ij". A game like this could be probably be made with a relatively crude grid structure as the primary data structure. However it seems like answering "which bubbles (if any) should fall now?" would be trickier with this data structure.

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• SUM of metric for normalized logical hierarchy

  - by Alex254

  Suppose there's a following table Table1, describing parent-child relationship and metric: Parent | Child | Metric (of a child) ------------------------------------ name0 | name1 | a name0 | name2 | b name1 | name3 | c name2 | name4 | d name2 | name5 | e name3 | name6 | f Characteristics: 1) Child always has 1 and only 1 parent; 2) Parent can have multiple children (name2 has name4 and name5 as children); 3) Number of levels in this "hierarchy" and number of children for any given parent are arbitrary and do not depend on each other; I need SQL request that will return result set with each name and a sum of metric of all its descendants down to the bottom level plus itself, so for this example table the result would be (look carefully at name1): Name | Metric ------------------ name1 | a + c + f name2 | b + d + e name3 | c + f name4 | d name5 | e name6 | f (name0 is irrelevant and can be excluded). It should be ANSI or Teradata SQL. I got as far as a recursive query that can return a SUM (metric) of all descendants of a given name: WITH RECURSIVE temp_table (Child, metric) AS ( SELECT root.Child, root.metric FROM table1 root WHERE root.Child = 'name1' UNION ALL SELECT indirect.Child, indirect.metric FROM temp_table direct, table1 indirect WHERE direct.Child = indirect.Parent) SELECT SUM(metric) FROM temp_table; Is there a way to turn this query into a function that takes name as an argument and returns this sum, so it can be called like this? SELECT Sum_Of_Descendants (Child) FROM Table1; Any suggestions about how to approach this from a different angle would be appreciated as well, because even if the above way is implementable, it will be of poor performance - there would be a lot of iterations of reading metrics (value f would be read 3 times in this example). Ideally, the query should read a metric of each name only once.

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• Software development process for a part time University project for 1 developer?

  - by Pricey

  I will be doing a part time University project soon and the time frame for it is around 8 months with approximately 10-15 hours a week spent working on it, with a review by a tutor each quarter. My question is what software development process would you recommend using when the course requires you to work on your own in order to manage yourself as well as the project? I wanted to use a weekly or bi-weekly iterative approach to my work but a lot of the processes seem tailored to teams of people. I am looking at XP (Extreme Programming) OR Scrum as something that is less than the norm for University work but again Scrum I don't know a lot about yet, and a question I have is; can you say you are doing XP without pair-programming? because my tutor seems to think that I have to stick to all the practices otherwise I can't do it (nevermind if I am working alone). We can have external user input as well but due to the small timescales with part time work it may be more beneficial for myself to be the user as well, which is not what I prefer considering how I can get lost in the design.

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• Oracle SOA Governance EMEA Workshop for Partners & System Integrators: Nov 5-7th | Madrid, Spain

  - by Lionel Dubreuil

  The EMEA Fusion Middleware Product Management team is delighted to announce an exciting and a much-awaited workshop on our market-leading SOA Governance offering. Oracle SOA Governance solution is Oracle Fusion Middleware's strategic approach to governing SOA. Whether just embarking on an SOA program, or expanding from project or pilot to broader deployment, the Oracle SOA Governance solution closes the loop on measuring SOA success from project inception through to realization, and providing the proof of ROI on SOA. Would your prospects and customers like to: Align their SOA Vision and Execution Improve Decision Making Effectively Manage Business and Technology Change Enable Control Foster Enterprise-wide Collaboration Reduce Development Costs Track their SOA Investments and Returns Demonstrate business value and ROI of SOA This FREE hands-on workshop is dedicated to EMEA Partners & System Integrators (SIs). It'll be delivered by Oracle HQ Product Management and will primarily focus on : SOA Governance as a Strategy and Methodology Hands-on with Oracle Enterprise Repository (OER) and Oracle Service Registry (OSR) When, how and whom to position our SOA Governance offerings Our SOA Governance Rapid Start Service Hands-on sessions for the most popular customer use cases Seats are limited, book now - you cannot afford to miss this training! If you're interested please contact Yogesh Sontakke: [email protected].

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• Good design for a simple site that contains a blog

  - by bporter

  What is a good design for a simple web site with mostly static pages and a blog? I am helping a friend build this for their small business. We are looking for a simple approach that can be implemented fairly quickly. (I am a programmer and can help with coding, hosting, etc.) One option is to use a site like virb, which lets you choose from one of their themes and build a site pretty easily. You can also include a blog. They host the site for a pretty low monthly rate. I recommended this option, but my friend wants a design that is unique and custom. So, I took one of the themes and started modifying the HTML and CSS. This might still be a good option, but... ...If we are going to greatly modify it, why not just create the static pages from scratch and use something like Wordpress for the blog. Is this a good option? It looks fairly easy to integrate Wordpress with a site so that the design and behavior are really cohesive. Is this a good idea? Do you recommend any other approaches?

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• SOA Starting Point: Methods for Service Identification and Definition

  As more and more companies start to incorporate a Service Oriented Architectural design approach into their existing enterprise systems, it creates the need for a standardized integration technology. One common technology used by companies is an Enterprise Service Bus (ESB). An ESB, as defined by Progress Software, connects and mediates all communications and interactions between services. In essence an ESB is a form of middleware that allows services to communicate with one another regardless of framework, environment, or location. With the emergence of ESB, a new emphasis is now being placed on approaches that can be used to determine what Web services should be built. In addition, what order should these services be built? In May 2011, SOA Magazine published an article that identified 10 common methods for identifying and defining services. SOA’s Ten Common Methods for Service Identification and Definition: Business Process Decomposition Business Functions Business Entity Objects Ownership and Responsibility Goal-Driven Component-Based Existing Supply (Bottom-Up) Front-Office Application Usage Analysis Infrastructure Non-Functional Requirements  Each of these methods provides various pros and cons in regards to their use within the design process. I personally feel that during a design process, multiple methodologies should be used in order to accurately define a design for a system or enterprise system. Personally, I like to create a custom cocktail derived from combining these methodologies in order to ensure that my design fits with the project’s and business’s needs while still following development standards and guidelines. Of these ten methods, I am particularly fond of Business Process Decomposition, Business Functions, Goal-Driven, Component-Based, and routinely use them in my designs.  Works Cited Hubbers, J.-W., Ligthart, A., & Terlouw , L. (2007, 12 10). Ten Ways to Identify Services. Retrieved from SOA Magazine: http://www.soamag.com/I13/1207-1.php Progress.com. (2011, 10 30). ESB ARCHITECTURE AND LIFECYCLE DEFINITION. Retrieved from Progress.com: http://web.progress.com/en/esb-architecture-lifecycle-definition.html

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• Augmenting functionality of subclasses without code duplication in C++

  - by Rob W

  I have to add common functionality to some classes that share the same superclass, preferably without bloating the superclass. The simplified inheritance chain looks like this: Element -> HTMLElement -> HTMLAnchorElement Element -> SVGElement -> SVGAlement The default doSomething() method on Element is no-op by default, but there are some subclasses that need an actual implementation that requires some extra overridden methods and instance members. I cannot put a full implementation of doSomething() in Element because 1) it is only relevant for some of the subclasses, 2) its implementation has a performance impact and 3) it depends on a method that could be overridden by a class in the inheritance chain between the superclass and a subclass, e.g. SVGElement in my example. Especially because of the third point, I wanted to solve the problem using a template class, as follows (it is a kind of decorator for classes): struct Element { virtual void doSomething() {} }; // T should be an instance of Element template<class T> struct AugmentedElement : public T { // doSomething is expensive and uses T virtual void doSomething() override {} // Used by doSomething virtual bool shouldDoSomething() = 0; }; class SVGElement : public Element { /* ... */ }; class SVGAElement : public AugmentedElement<SVGElement> { // some non-trivial check bool shouldDoSomething() { /* ... */ return true; } }; // Similarly for HTMLAElement and others I looked around (in the existing (huge) codebase and on the internet), but didn't find any similar code snippets, let alone an evaluation of the effectiveness and pitfalls of this approach. Is my design the right way to go, or is there a better way to add common functionality to some subclasses of a given superclass?

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• Sending changes to a terrain heightmap over UDP

  - by Floomi

  This is a more conceptual, thinking-out-loud question than a technical one. I have a 3D heightmapped terrain as part of a multiplayer RTS that I would like to terraform over a network. The terraforming will be done by units within the gameworld; the player will paint a "target heightmap" that they'd like the current terrain to resemble and units will deform towards that on their own (a la Perimeter). Given my terrain is 257x257 vertices, the naive approach of sending heights when they change will flood the bandwidth very quickly - updating a quarter of the terrain every second will hit ~66kB/s. This is clearly way too much. My next thought was to move to a brush-based system, where you send e.g. the centre of a circle, its radius, and some function defining the influence of the brush from the centre going outwards. But even with reliable UDP the "start" and "stop" messages could still be delayed. I guess I could compare timestamps and compensate for this, although it'd likely mean that clients would deform verts too much on their local simulations and then have to smooth them back to the correct heights. I could also send absolute vert heights in the "start" and "stop" messages to guarantee correct data on the clients. Alternatively I could treat brushes in a similar way to units, and do the standard position + velocity + client-side prediction jazz on them, with the added stipulation that they deform terrain within a certain radius around them. The server could then intermittently do a pass and send (a subset of) recently updated verts to clients as and when there's bandwidth to spare. Any other suggestions, or indications that I'm on the right (or wrong!) track with any of these ideas would be greatly appreciated.

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• Need theoretical help, how to comprehend an if-else dependency net

  - by macbie

  I am going to face a following issue: I'm writing a program that manages some properties, some of them are general and some are specific. Each property is a pair of key and value, and for example: if it is given a general property and other specific property with exactly the same key and value has been existed before then the general property will swap the specific one in the register. If there are two the same general properties - both will remain in the register. And so on; it is like a net of dependencies. In my case I can handle with it intuitively and foresee all cases, but only because the system is not too vast. What if it would? I have met such problems a few times in many different programs and languages (i.e working with C semaphores) and my question is: How to approach this kind of problem? Is this connected with finite state machine, graph theory or something similar? How to be sure that I have considered the whole system and each possible case? Could you recommend some resources (books, sites) to learn from?

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• Turning a problem into a data

  - by Fogmeister

  OK, I have an app that I'm creating but I'm just really not sure about how to approach the problem. The idea is fairly simple. I'm just not sure how to wrap it in a data model (or even if I should). TBH I feel like I'm making it more complicated than it needs to be. How it works. The app will have circles along the top in a row that need to be connected to circles along the bottom in a row. 10 circles at the top. 10 at the bottom. One connection per pair of dots. Anyway, I can get the dots to connect I'm just not sure how to wrap it in a data model so that I can analyse what has been connected and see if it is right or not. The circles will be questions and answers. I can make an array of question objects with a question and answer properties. I can then display these as the dot pairs. I'm just not sure how to record which questions have been connected to which answers. It is valid for a user to connect a wrong answer as they all get checked at the end. I was thinking of using SpriteKit but this isn't a restriction. I could use UIKit or something else. TBH, this question is fairly language free as I'm just after a way of modelling it.

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• Is Moving Entity Framework objects over a webservice really the best way?

  - by aceinthehole

  I've inherited a .NET project that has close to 2 thousand clients out in the field that need to push data periodically up to a central repository. The clients wake up and attempt to push the data up via a series of WCF webservices where they are passing each entity framework entity as parameter. Once the service receives this object, it preforms some business logic on the data, and then turns around and sticks it in it's own database that mirrors the database on the client machines. The trick is, is that this data is being transmitted over a metered connection, which is very expensive. So optimizing the data is a serious priority. Now, we are using a custom encoder that compresses the data (and decompresses it on the other end) while it is being transmitted, and this is reducing the data footprint. However, the amount of data that the clients are using, seem ridiculously large, given the amount of information that is actually being transmitted. It seems me that entity framework itself may be to blame. I'm suspecting that the objects are very large when serialized to be sent over wire, with a lot context information and who knows what else, when what we really need is just the 'new' inserts. Is using the entity framework and WCF services as we have done so far the correct way, architecturally, of approaching this n-tiered, asynchronous, push only problem? Or is there a different approach, that could optimize the data use?

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• Finding the shortest path through a digraph that visits all nodes

  - by Boluc Papuccuoglu

  I am trying to find the shortest possible path that visits every node through a graph (a node may be visited more than once, the solution may pick any node as the starting node.). The graph is directed, meaning that being able to travel from node A to node B does not mean one can travel from node B to node A. All distances between nodes are equal. I was able to code a brute force search that found a path of only 27 nodes when I had 27 nodes and each node had a connection to 2 or 1 other node. However, the actual problem that I am trying to solve consists of 256 nodes, with each node connecting to either 4 or 3 other nodes. The brute force algorithm that solved the 27 node graph can produce a 415 node solution (not optimal) within a few seconds, but using the processing power I have at my disposal takes about 6 hours to arrive at a 402 node solution. What approach should I use to arrive at a solution that I can be certain is the optimal one? For example, use an optimizer algorithm to shorten a non-optimal solution? Or somehow adopt a brute force search that discards paths that are not optimal? EDIT: (Copying a comment to an answer here to better clarify the question) To clarify, I am not saying that there is a Hamiltonian path and I need to find it, I am trying to find the shortest path in the 256 node graph that visits each node AT LEAST once. With the 27 node run, I was able to find a Hamiltonian path, which assured me that it was an optimal solution. I want to find a solution for the 256 node graph which is the shortest.

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• How to divide work to a network of computers?

  - by Morpork

  Imagine a scenario as follows: Lets say you have a central computer which generates a lot of data. This data must go through some processing, which unfortunately takes longer than to generate. In order for the processing to catch up with real time, we plug in more slave computers. Further, we must take into account the possibility of slaves dropping out of the network mid-job as well as additional slaves being added. The central computer should ensure that all jobs are finished to its satisfaction, and that jobs dropped by a slave are retasked to another. The main question is: What approach should I use to achieve this? But perhaps the following would help me arrive at an answer: Is there a name or design pattern to what I am trying to do? What domain of knowledge do I need to achieve the goal of getting these computers to talk to each other? (eg. will a database, which I have some knowledge of, be enough or will this involve sockets, which I have yet to have knowledge of?) Are there any examples of such a system? The main question is a bit general so it would be good to have a starting point/reference point. Note I am assuming constraints of c++ and windows so solutions pointing in that direction would be appreciated.

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• Which is a better practice - helper methods as instance or static?

  - by Ilian Pinzon

  This question is subjective but I was just curious how most programmers approach this. The sample below is in pseudo-C# but this should apply to Java, C++, and other OOP languages as well. Anyway, when writing helper methods in my classes, I tend to declare them as static and just pass the fields if the helper method needs them. For example, given the code below, I prefer to use Method Call #2. class Foo { Bar _bar; public void DoSomethingWithBar() { // Method Call #1. DoSomethingWithBarImpl(); // Method Call #2. DoSomethingWithBarImpl(_bar); } private void DoSomethingWithBarImpl() { _bar.DoSomething(); } private static void DoSomethingWithBarImpl(Bar bar) { bar.DoSomething(); } } My reason for doing this is that it makes it clear (to my eyes at least) that the helper method has a possible side-effect on other objects - even without reading its implementation. I find that I can quickly grok methods that use this practice and thus help me in debugging things. Which do you prefer to do in your own code and what are your reasons for doing so?

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• Museum of Modern Art Starts Video Game Collection; Acquires Myst, Pac-Man, and More

  - by Jason Fitzpatrick

  The Museum of Modern Art is weighing in on the video-games-as-art debate by starting a collection of iconic video games and putting them up for public display. Read on to see what games are included in the initial batch and the MoMA’s reasons behind starting a video game collection. Although the MoMA is slated to grow to over 40 titles, the seed batch is 14 titles including: Pac-Man, Tetris, Sim City 2000, Myst, Portal, and Dwarf Fortress. In the announcement they explain the motivation for building a video game collection: Are video games art? They sure are, but they are also design, and a design approach is what we chose for this new foray into this universe. The games are selected as outstanding examples of interaction design—a field that MoMA has already explored and collected extensively, and one of the most important and oft-discussed expressions of contemporary design creativity. Our criteria, therefore, emphasize not only the visual quality and aesthetic experience of each game, but also the many other aspects—from the elegance of the code to the design of the player’s behavior—that pertain to interaction design. In order to develop an even stronger curatorial stance, over the past year and a half we have sought the advice of scholars, digital conservation and legal experts, historians, and critics, all of whom helped us refine not only the criteria and the wish list, but also the issues of acquisition, display, and conservation of digital artifacts that are made even more complex by the games’ interactive nature. This acquisition allows the Museum to study, preserve, and exhibit video games as part of its Architecture and Design collection. The above quote is only a small snippet of a much lengthier look at the benefits of examining and preserving video games, hit up the link below to check out the full post including future titles the MoMA would like to include in their archive. Video Games: 14 in the Collection, for Starters [Inside/Out] How To Boot Your Android Phone or Tablet Into Safe Mode HTG Explains: Does Your Android Phone Need an Antivirus? How To Use USB Drives With the Nexus 7 and Other Android Devices

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• how to make a continuous machine gun sound-effect

  - by Jan

  I am trying to make an entity fire one or more machine-guns. For each gun I store the time between shots (1.0 / firing rate) and the time since the last shot. Also I've loaded ~10 different gun-shot sound-effects. Now, for each gun I do the following: function update(deltatime): timeSinceLastShot += deltatime if timeSinceLastShot >= timeBetweenShots + verySmallRandomValue(): timeSinceLastShot -= timeBetweenShots if gunIsFiring: displayMuzzleFlash() spawnBullet() selectRandomSound().play() But now I often get a crackling noise (which I assume is when two or more guns are firing at the same time and confuse the sound-device). My question is whether A) This a common problem and there is a well-known solution, maybe to do with the channels or something, or B) I am using a completely wrong approach to the task. I had a look at some sound-assets for other games and they used complete burst with multiple shots. I suppose I could try that, but I would like to have organic little hickups in the gun-fire (that's what the random value is for) to make the game more gritty and dirty. I am using Panda3D, but I had the exact same problem in PyGame and SDL. [edit] Thanks a lot for the answers so far! One more problem with faking it though: Now how do I stop the sound? Let's say I have an effect with 5 bangs... *bang* *bang* *bang* *bang* *bang* And I magically manage to loop it so that there's no gap or overlap if the player fires more than 5 shots. Now, what do I do if the player stops firing halfway through the third bang? How do I know how long to keep playing the sample so that the third bang is completed and I can start playing the rumbling echo of the last shot? Of course I can look up the shot/pause timing of that sound-sample and code accordingly, but it feels extremely hacky.

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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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• Real-time stock market application

  - by Sam

  I'm an amateur programmer. I'd like to develop a software application (like Tradestation), to analyse real-time market data. Please teach me if the following approach is correct, ie the procedures, knowledge or software needed etc: Use a DB to read the real-time feed from data provider: what should be the right DB to use? I know it should be a time serious one. Can I use SQL, Mysql, or others? What database can receive real-time data feed? Do I need to configure the DB to do this? If the real-time data is in ASCII form, how can it be converted to those that can be read by the DB and my application? Should I have to write codes or just use some add-ins? What kind of add-in are needed? How should I code the program to retrieve the changing data from the DB so that the analysis software screen data can also change asynchronously? (like the RTD in excel) Which aspects of programming do I need to learn to develop the above? Are there web resources/ books I can refer to for more information?

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• Microeconomical simulation: coordination/planning between self-interested trading agents

  - by Milton Manfried

  In a typical perfect-information strategy game like Chess, an agent can calculate its best move by searching the state tree for the best possible move, while assuming that the opponent will also make the best possible move (i.e. Mini-max). I would like to use this approach in a "game" modeling economic activity, where the possible "moves" would be to buy or sell for a given price, and the goal, rather than a specific class of states (e.g. Checkmate), would be to maximize some function F of the agent's state (e.g. F(money, widget) = 10*money + widget). How to handle buy/sell actions that require coordination between both parties, at the very least agreement upon a price? The cheap way out would be to set the price beforehand, maybe based upon the current supply -- but the idea of this simulation is to examine how prices emerge when freely determined by "perfectly rational" agents. A great example of what I do not want is the trading algorithm in SugarScape -- paraphrasing from Growing Artificial Societies p101-102: when a pair of agents interact to trade, they each compute their internal valuations of the goods, then a bargaining process is conducted and a price is agreed to. If this price makes both agents better off, they complete the transaction The protocol itself is beautiful, but what it cannot capture (as far as I can tell) is the ability for an agent to pay more than it might otherwise for a good, because it knows that it can sell it for even more at a later date -- what appears to be called "strategic thinking" in this pape at Google Books Multi-Agent-Based Simulation III: 4th International Workshop, MABS 2003... to get realistic behavior like that, it seems one would either (1) have to build an outrageously-complex internal valuation system which could at best only cover situations that were planned for at compile-time, or otherwise (2) have some mechanism to search the state tree... which would require some way of planning future trades. Note: The chess analogy only works as far as the state-space search goes; the simulation isn't intended to be "zero sum", so a literal mini-max search wouldn't be appropriate -- and ideally, it should work with more than two agents.

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• Building a template engine - starting point

  - by Anirudh

  We're building a Django-based project with a template component. This component will be separate from the project as such and can be Django/Python, Node, Java or whatever works. The template has to be rendered into HTML. The templates will contain references to objects with properties that are defined in the DB, say, a Bus. For eg, it could be something like [object type="vehicle" weight="heavy"] and it would have to pull a random object from the DB fulfilling the criteria : type="vehicle" weight="heavy" (bus/truck/jet) and then substitute that tag with an image, say, of a Bus. Also it would have to be able to handle some processing. Eg: What is [X type="integer" lte="10"] + [Y type="integer" lte="10"] [option X+Y correct_ans="true"] [option X-Y correct_ans="false"] [option X+y+1 correct_ans="false"] The engine would be expected to fill in a random integer value <= 10 for X and Y and show radioboxes for each of the options. Would also have to store the fact that the first option is the correct answer. Does it to make sense to write something from the scratch? Or is it better to use an existing templating system (like Django's own templating system) as a starting point? Any suggestions on how I can approach this?

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• Best peer-to-peer game architecture

  - by Dejw

  Consider a setup where game clients: have quite small computing resources (mobile devices, smartphones) are all connected to a common router (LAN, hotspot etc) The users want to play a multiplayer game, without an external server. One solution is to host an authoritative server on one phone, which in this case would be also a client. Considering point 1 this solution is not acceptable, since the phone's computing resources are not sufficient. So, I want to design a peer-to-peer architecture that will distribute the game's simulation load among the clients. Because of point 2 the system needn't be complex with regards to optimization; the latency will be very low. Each client can be an authoritative source of data about himself and his immediate environment (for example bullets.) What would be the best approach to designing such an architecture? Are there any known examples of such a LAN-level peer-to-peer protocol? Notes: Some of the problems are addressed here, but the concepts listed there are too high-level for me. Security I know that not having one authoritative server is a security issue, but it is not relevant in this case as I'm willing to trust the clients. Edit: I forgot to mention: it will be a rather fast-paced game (a shooter). Also, I have already read about networking architectures at Gaffer on Games.

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