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• How to achieve selection of a tile from a tile sheet based on an ID?

  - by Bugster

  Let's say I have a tile sheet that contains 8 sprites per sheet. Each sprite is a tile of 30x30. I wrote my own custom map parser/map loader however I'm having trouble extracting a certain tile sprite from the file. I'll describe my problem better in order for everyone to understand. I wrote an enum of materials, each material has a value according to it's location relative to the tile sheet. For example void is 1, grass is 2, rock is 3, etc. So in my tile sheet they are represented as such: +---+---+---+---+---+ | 1 | 2 | 3 | 4 | 5 | +---+---+---+---+---+ Which is equivalent to: +------+-------+-------+ | void | grass | stone | +------+-------+-------+ Basically when rendering, I created a tile class, each tile has 2 coordinates: X and Y (They are calculated automatically) and a material which can be represented either as a number, either as a value (ID). When rendering, I have a vector of sprites which are all taken from 1 file called tilesheet.png, however each of them must only draw a certain portion of the tile sheet, for example say I have something like this: tile coordinateBounds(topLeftX, topLeftY, tileWidth, tileHeight); During the initialization of the map I calculate an array of tiles, and I give each of them their position, their materials based on the values in a map file and a few other variables such as collision. I need to apply the coordinateBounds to each of them according to their material value. For example if the material is grass it should only take the grass sprite from the tilesheet. I must also mention I'm using SFML, and there are no borders or spacing between the tiles.

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• What language and topics should be covered when teaching non-CS college students how to program?

  - by michaelcarrano

  I have been asked by many of my non-computer science friends to teach them how to program. I have agreed to hold a seminar for them that will last for approximately 1 to 2 hours. My thoughts are to use Python as the language to teach them basic programming skills. I figured Python is relatively easier to learn from what I have researched. It is also a language I want to learn which will make holding this seminar all the more enjoyable. The topics I plan to cover are as followed: Variables / Arrays Logic - If else statements, switch case, nested statements Loops - for, while, do-while and nested loops Functions - pass by value, pass by reference (is this the correct terms for Python? I am mostly a C/C++ person) Object Oriented Programming Of course, I plan to have code examples for all topics and I will try to have each example flow into each other so that at the end of the seminar everyone will have a complete working program. I suppose my question is, if you were given 1 to 2 hours to teach a group of college students how to program, what language would you choose and what topics would you cover? Update: Thank you for the great feedback. I should have mentioned in my earlier post above that a majority of the students attending the seminar have some form of programming experience whether it was with Java or using Matlab. Most of these students are 3rd/4th year Engineering students who want to get a refresher on programming before they graduate.

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• The Growing Importance of Network Virtualization

  - by user12608550

  The Growing Importance of Network Virtualization We often focus on server virtualization when we discuss cloud computing, but just as often we neglect to consider some of the critical implications of that technology. The ability to create virtual environments (or VEs [1]) means that we can create, destroy, activate and deactivate, and more importantly, MOVE them around within the cloud infrastructure. This elasticity and mobility has profound implications for how network services are defined, managed, and used to provide cloud services. It's not just servers that benefit from virtualization, it's the network as well. Network virtualization is becoming a hot topic, and not just for discussion but for companies like Oracle and others who have recently acquired net virtualization companies [2,3]. But even before this topic became so prominent, Solaris engineers were working on technologies in Solaris 11 to virtualize network services, known as Project Crossbow [4]. And why is network virtualization so important? Because old assumptions about network devices, topology, and management must be re-examined in light of the self-service, elasticity, and resource sharing requirements of cloud computing infrastructures. Static, hierarchical network designs, and inter-system traffic flows, need to be reconsidered and quite likely re-architected to take advantage of new features like virtual NICs and switches, bandwidth control, load balancing, and traffic isolation. For example, traditional multi-tier Web services (Web server, App server, DB server) that share net traffic over Ethernet wires can now be virtualized and hosted on shared-resource systems that communicate within a larger server at system bus speeds, increasing performance and reducing wired network traffic. And virtualized traffic flows can be monitored and adjusted as needed to optimize network performance for dynamically changing cloud workloads. Additionally, as VEs come and go and move around in the cloud, static network configuration methods cannot easily accommodate the routing and addressing flexibility that VE mobility implies; virtualizing the network itself is a requirement. Oracle Solaris 11 [5] includes key network virtualization technologies needed to implement cloud computing infrastructures. It includes features for the creation and management of virtual NICs and switches, and for the allocation and control of the traffic flows among VEs [6]. Additionally it allows for both sharing and dedication of hardware components to network tasks, such as allocating specific CPUs and vNICs to VEs, and even protocol-specific management of traffic. So, have a look at your current network topology and management practices in view of evolving cloud computing technologies. And don't simply duplicate the physical architecture of servers and connections in a virtualized environment…rethink the traffic flows among VEs and how they can be optimized using Oracle Solaris 11 and other Oracle products and services. [1] I use the term "virtual environment" or VE here instead of the more commonly used "virtual machine" or VM, because not all virtualized operating system environments are full OS kernels under the control of a hypervisor…in other words, not all VEs are VMs. In particular, VEs include Oracle Solaris zones, as well as SPARC VMs (previously called LDoms), and x86-based Solaris and Linux VMs running under hypervisors such as OEL, Xen, KVM, or VMware. [2] Oracle follows VMware into network virtualization space with Xsigo purchase; http://www.mercurynews.com/business/ci_21191001/oracle-follows-vmware-into-network-virtualization-space-xsigo [3] Oracle Buys Xsigo; http://www.oracle.com/us/corporate/press/1721421 [4] Oracle Solaris 11 Networking Virtualization Technology, http://www.oracle.com/technetwork/server-storage/solaris11/technologies/networkvirtualization-312278.html [5] Oracle Solaris 11; http://www.oracle.com/us/products/servers-storage/solaris/solaris11/overview/index.html [6] For example, the Solaris 11 'dladm' command can be used to limit the bandwidth of a virtual NIC, as follows: dladm create-vnic -l net0 -p maxbw=100M vnic0

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• I can't program because the code I am using uses old coding styles. Is this normal to programmers? [closed]

  - by Renato Dinhani Conceição

  I'm in my first real job as programmer, but I can't solve any problems because of the coding style used. The code here: Does not have comments Does not have functions (50, 100, 200, 300 or more lines executed in sequence) Uses a lot of if statements with a lot of paths Has variables that make no sense (eg.: cf_cfop, CF_Natop, lnom, r_procod) Uses an old language (Visual FoxPro 8 from 2002), but there are new releases from 2007. I feel like I have gone back to 1970. Is it normal for a programmer familiar with OOP, clean-code, design patterns, etc. to have trouble with coding in this old-fashion way? EDIT: All the answers are very good. For my (un)hope, appears that there are a lot of this kind of code bases around the world. A point mentioned to all answers is refactor the code. Yeah, I really like to do it. In my personal project, I always do this, but... I can't refactor the code. Programmers are only allowed to change the files in the task that they are designed for. Every change in old code must be keep commented in the code (even with Subversion as version control), plus meta informations (date, programmer, task) related to that change (this became a mess, there are code with 3 used lines and 50 old lines commented). I'm thinking that is not only a code problem, but a management of software development problem.

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• Strategies for managing use of types in Python

  - by dave

  I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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• How to suggest changes as a recently-hired employee ?

  - by ereOn

  Hi, I was recently hired in a big company (thousands of people, to give an idea of the size). They said they hired me because of my rigor and because I was, despite my youngness (i'm 25), experienced as a C/C++ programer. Now that I'm in, I can see that the whole system is old and often uses obsolete technologies. There is no naming convention (files, functions, variables, ...), they don't use Version Control, don't use exceptions or polymorphism and it seems like almost everybody lost his passion (some of them are only 30 years old). I'd like to suggest somes changes but i don't want to be "the new guy that wants to change everything just because he doesn't want to fit in". I tried to "fit in", but actually, It takes me one week to do what I would do in one afternoon, just because of the poor tools we're forced to use. A lot my collegues never look at the new "things" and techniques that people use nowadays. It's like they just given up. The situation is really frustrating. Have you ever been in a similar situation and, if so, what advices would you give me ? Is there a subtle way of changing things without becoming the black sheep here ? Or should I just give up my passion and energy as well ? Thank you. Updates Just in case (if anyone cares): following your precious advices I was able to suggest changes and am now in charge of the team that must create and deploy Subversion :D Thanks to all of you !

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• PHP-FPM stops responding and dies [migrated]

  - by user12361

  I'm running Drupal 6 with Nginx 1.5.1 and PHP-FPM (PHP 5.3.26) on a 1GB single core VPS with 3GB of swap space on SSD storage. I just switched from shared hosting to this unmanaged VPS because my site was getting too heavy, so I'm still learning the ropes. I have moderately high traffic, I don't really monitor it closely but Google Adsense usually record close to 30K page views/day. I usually have 50 to 80 authenticated users logged in and a few hundred more anonymous users hitting the Boost static HTML cache at any given moment. The problem I'm having is that PHP-FPM frequently stops responding, resulting in Nginx 502 or 504 errors. I swear I have read every page on the internet about this issue, which seems fairly common, and I've tried endless combinations of configurations, and I can't find a good solution. After restarting Nginx and PHP-FPM, the site runs really fast for a while, and then without warning it simply stops responding. I get a white screen while the browser waits on the server, and after about 30 seconds to a minute it throws an Nginx 502 or 504 error. Sometimes it runs well for 2 minutes, sometimes 5 minutes, sometimes 5 hours, but it always ends up hanging. When I find the server in this state, there is still plenty of free memory (500MB or more) and no major CPU usage, the control and worker PHP-FPM processes are still present, and the server is still pingable and usable via SSH. A reload of PHP-FPM via the init script revives it again. The hangups don't seem to correspond to the amount of traffic, because I observed this behavior consistently when I was testing this configuration on a development VPS with no traffic at all. I've been constantly tweaking the settings, but I can't definitively eliminate the problem. I set Nginx workers to just 1. In the PHP-FPM config I have tried all three of the process managers. "Dynamic" is definitely the least reliable, consistently hanging up after only a few minutes. "Static" also has been unreliable and unpredictable. The least buggy has been "ondemand", but even that is failing me, sometimes after as much as 12 to 24 hours. But I can't leave the server unattended because PHP-FPM dies and never comes back on its own. I tried adjusting the pm.max_children value from as low as 3 to as high as 50, doesn't make a lot of difference, but I currently have it at 10. Same thing for the spare servers values. I also have set pm.max_requests anywhere from 30 to unlimited, and it doesn't seem to make a difference. According to the logs, the PHP-FPM processes are not exiting with SIGSEGV or SIGBUS, but rather with SIGTERM. I get a lot of lines like: WARNING: [pool www] child 3739, script '/var/www/drupal6/index.php' (request: "GET /index.php") execution timed out (38.739494 sec), terminating and: WARNING: [pool www] child 3738 exited on signal 15 (SIGTERM) after 50.004380 seconds from start I actually found several articles that recommend doing a graceful reload of PHP-FPM via cron every few minutes or hours to circumvent this issue. So that's what I did, "/etc/init.d/php-fpm reload" every 5 minutes. So far, it's keeping the lights on. But it feels like a dreadful hack. Is PHP-FPM really that unreliable? Is there anything else I can do? Thanks a lot!

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• Dreaded SQLs

  - by lavanyadeepak

  Dreaded SQLs We used to think that a SQL statement without a where clause is only dangerous right since running that on a server TSQL is just going to impact the entire table like waving the magic wand. For that reason we should cultivate the habit first to write the statement as select and then to modify the select portion as update. Within the T-SQL Window, I would normally prefer the following first: select * from employee where empid in (4,5) and then once I am satisfied with the results, I would go ahead with the following change: --select * delete from employee where empid in (4,5) Today I just discovered another coding horror. This would typically be applicable in a stored procedure and with respect to variable nomenclature. It is always desirable to have a suitable nomenclature for parameters distinct from the column names and internal variables. This would help quicker debugging of the stored procedures besides enhancing the readability. Else in a quick bout of enthusiasm a statement like   if (@CustomerID = @CustomerID) [when the latter is intended to denote the column name and there is a superflous @ prepended], zeroing in on the problem would be little tricky. Had there been a still powerful nomenclature rules then debugging would have been more straight-forward and simpler right?

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• Teach Your Kid to Code Coming to Philly.NET

  - by Steve Michelotti

  Originally posted on: http://geekswithblogs.net/michelotti/archive/2014/05/20/teach-your-kid-to-code-coming-to-philly.net.aspxTomorrow night (Wednesday, May 21) my son and I will be at Philly.NET presenting Teach Your Kid to Code. Bring your kid out to Philly.NET with you for a fun evening! After our first talk, I’ll then be giving an introduction to TypeScript. Of any presentation I’ve ever given, this is my favorite: Have you ever wanted a way to teach your kid to code? For that matter, have you ever wanted to simply be able to explain to your kid what you do for a living? Putting things in a context that a kid can understand is not as easy as it sounds. If you are someone curious about these concepts, this is a “can’t miss” presentation that will be co-presented by Justin Michelotti (6th grader) and his father. Bring your kid with you to Philly.NET for this fun and educational session. We will show tools you may not have been aware of like SmallBasic and Kodu – we’ll even throw in a little Visual Studio and JavaScript. Concepts such as variables, conditionals, loops, and functions will be covered while we introduce object oriented concepts without any of the confusing words. Kids are not required for entry!

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• An observation on .NET loops – foreach, for, while, do-while

  It’s very common that .NET programmers use “foreach” loop for iterating through collections. Following is my observation whilst I was testing simple scenario on loops. “for” loop is 30% faster than “foreach” and “while” loop is 50% faster than “foreach”. “do-while” is bit faster than “while”. Someone may feel that how does it make difference if I’m iterating only 1000 times in a loop. This test case is only for simple iteration. According to the "Data structure" concepts, best and worst cases are completely based on the data we provide to the algorithm. so we can not conclude that a "foreach" algorithm is not good. All I want to tell that we need to be little cautious even choosing the loops. Example:- You might want to chose quick sort when you want to sort more numbers. At the same time bubble sort may be effective than quick sort when you want to sort less numbers. Take a simple scenario, a request of a simple web application fetches the data of 10000 (10K) rows and iterating them for some business logic. Think, this application is being accessed by 1000 (1K) people simultaneously. In this simple scenario you are ending up with 10000000 (10Million or 1 Crore) iterations. below is the test scenario with simple console application to test 100 Million records. using System;using System.Collections.Generic;using System.Diagnostics;namespace ConsoleApplication1{ class Program { static void Main(string[] args) { var sw = new Stopwatch(); var numbers = GetSomeNumbers(); sw.Start(); foreach (var item in numbers) { } sw.Stop(); Console.WriteLine( String.Format("\"foreach\" took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); for (int i = 0; i < numbers.Count; i++) { } sw.Stop(); Console.WriteLine( String.Format("\"for\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it = 0; while (it++ < numbers.Count) { } sw.Stop(); Console.WriteLine( String.Format("\"while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it2 = 0; do { } while (it2++ < numbers.Count); sw.Stop(); Console.WriteLine( String.Format("\"do-while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); } #region Get me 10Crore (100 Million) numbers private static List<int> GetSomeNumbers() { var lstNumbers = new List<int>(); var count = 100000000; for (var i = 1; i <= count; i++) { lstNumbers.Add(i); } return lstNumbers; } #endregion Get me some numbers }} In above example, I was just iterating through 100 Million numbers. You can see the time to execute various  loops provided in .NET Output "foreach" took 1108 milliseconds "for" loop took 727 milliseconds "while" loop took 596 milliseconds "do-while" loop took 594 milliseconds   Press any key to continue . . . So I feel we need to be careful while choosing the looping strategy. Please comment your thoughts. span.fullpost {display:none;}

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• TXPAUSE : polite waiting for hardware transactional memory

  - by Dave

  Classic locks are an appropriate tool to prevent potentially conflicting operations A and B, invoked by different threads, from running at the same time. In a sense the locks cause either A to run before B or vice-versa. Similarly, we can replace the locks with hardware transactional memory, or use transactional lock elision to leverage potential disjoint access parallelism between A and B. But often we want A to wait until B has run. In a Pthreads environment we'd usually use locks in conjunction with condition variables to implement our "wait until" constraint. MONITOR-MWAIT is another way to wait for a memory location to change, but it only allows us to track one cache line and it's only available on x86. There's no similar "wait until" construct for hardware transactions. At the instruction-set level a simple way to express "wait until" in transactions would be to add a new TXPAUSE instruction that could be used within an active hardware transaction. TXPAUSE would politely stall the invoking thread, possibly surrendering or yielding compute resources, while at the same time continuing to track the transaction's address-set. Once a transaction has executed TXPAUSE it can only abort. Ideally that'd happen when some other thread modifies a variable that's in the transaction's read-set or write-set. And since we're aborting all writes would be discarded. In a sense this gives us multi-location MWAIT but with much more flexibility. We could also augment the TXPAUSE with a cycle-count bound to cap the time spent stalled. I should note that we can already enter a tight spin loop in a transaction to wait for updates to address-set to cause an abort. Assuming that the implementation monitors the address-set via cache-coherence probes, by waiting in this fashion we actually communicate via the probes, and not via memory values. That is the updating thread signals the waiter via probes instead of by traditional memory values. But TXPAUSE gives us a polite way to spin.

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• How to justify rewriting/revamping legacy software in a business case?

  - by sxthomson

  I work for a great little software company which makes good revenue from our main software package. The problem for me is that it's almost unmaintainable. It's written in Delphi 7 (has upgraded versions over time) and has been worked on by a lot of developers over the past 20 or so years. The software lacks any meaningful architecture - there's no object orientation whatsoever, horrible amounts of cyclical dependencies and an over-reliance on global variables to name just a few things. Another huge thing for me is Delphi 7 does NOT support 64-bit. The problem here for me is that my management team don't care about technical things, they want to know why they should care. Obviously that's expected, so what I'm asking here is for some guidance, or tales, or pitfalls about this kind of thing. There's a few things I would love to include, namely for me, the length of time taken to debug/write a feature in "legacy" code, versus coherent, well structured OO code. Does anyone know of any blog posts or the like where this is talked about? For us in the company this is a huge reason. Despite being decent developers we feel like writing a new feature is just piling more rubbish on top. On top of that, even for me who has a decent level of understanding of the code, changing things is infuriating - a small change can have a ridiculous domino effect. Anyone have any experiences they'd like to share?

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• How to visualize code?

  - by gablin

  I've mostly only had to read my own code. As such, I've had no need to visualize the code as I already know how each and every class and module communicate with one another. But the few times I've had to read someone else's code - let us now assume we are talking about at least one larger module which contains several internal classes - I've almost always found myself wishing "This would have been so much easier to understand if I could just visualize it!" So what are the common methods or tools for enabling this? Which do you use, and why do you prefer them over the others? I've heard stuff like UML, module and class diagrams, but I imagine there are more. Furthermore, any of these is most likely better than anything I can devise on my own. EDIT: For those who answer with "Use pen and paper and just draw it": This isn't very helpful unless you explain this further. What exactly am I supposed to draw? A box for each class? Should I include the public methods? What about its fields? How should I draw connections that explain how one class uses another? What about modules? What if the language isn't object-oriented but functional or logical, or even just imperative (C, for instance)? What about global variables and functions? Is there an already-standardized way of drawing this, or do I need to think up of a method of my own? You get the drift.

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• Hopping/Tumbling Windows Could Introduce Latency.

  This is a pre-article to one I am going to be writing on adjusting an event’s time and duration to satisfy business process requirements but it is one that I think is really useful when understanding the way that Hopping/Tumbling windows work within StreamInsight.  A Tumbling window is just a special shortcut version of  a Hopping window where the width of the window is equal to the size of the hop Here is the simplest and often used definition for a Hopping Window.  You can find them all here public static CepWindowStream<CepWindow<TPayload>> HoppingWindow<TPayload>(     this CepStream<TPayload> source,     TimeSpan windowSize,     TimeSpan hopSize,     WindowInputPolicy inputPolicy,     HoppingWindowOutputPolicy outputPolicy )   And here is the definition for a Tumbling Window public static CepWindowStream<CepWindow<TPayload>> TumblingWindow<TPayload>(     this CepStream<TPayload> source,     TimeSpan windowSize,     WindowInputPolicy inputPolicy,     HoppingWindowOutputPolicy outputPolicy )   These methods allow you to group events into windows of a temporal size.  It is a really useful and simple feature in StreamInsight.  One of the downsides though is that the windows cannot be flushed until an event in a following window occurs.  This means that you will potentially never see some events or see them with a delay.  Let me explain. Remember that a stream is a potentially unbounded sequence of events. Events in StreamInsight are given a StartTime.  It is this StartTime that is used to calculate into which temporal window an event falls.  It is best practice to assign a timestamp from the source system and not one from the system clock on the processing server.  StreamInsight cannot know when a window is over.  It cannot tell whether you have received all events in the window or whether some events have been delayed which means that StreamInsight cannot flush the stream for you.   Imagine you have events with the following Timestamps 12:10:10 PM 12:10:20 PM 12:10:35 PM 12:10:45 PM 11:59:59 PM And imagine that you have defined a 1 minute Tumbling Window over this stream using the following syntax var HoppingStream = from shift in inputStream.TumblingWindow(TimeSpan.FromMinutes(1),HoppingWindowOutputPolicy.ClipToWindowEnd) select new WindowCountPayload { CountInWindow = (Int32)shift.Count() };   The events between 12:10:10 PM and 12:10:45 PM will not be seen until the event at 11:59:59 PM arrives.  This could be a real problem if you need to react to windows promptly This can always be worked around by using a different design pattern but a lot of the examples I see assume there is a constant, very frequent stream of events resulting in windows always being flushed. Further examples of using windowing in StreamInsight can be found here

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• How to factorize code in Unreal Kismet (i.e. "Material Function"s for Kismet)

  - by Georges Dupéron

  In the Unreal Development Kit, when using the Material Editor, one can factorize frequently-used groups of nodes by creating a Material Function (content Browser ? right-click ? new matrial function, IIRC). When defining the behaviour of some actor in Kismet, one can easily have a dozen nodes involved. If I have many actors that share the same behaviour, then I'll copy-paste these nodes, and change the variables so they point to the other actors. This leads to inconsistencies (a modification in the behaviour of an actor isn't propagated in the copy-pasted nodes), complexity (you end up with hundreds of nodes), and generally useless effort. My question is : Can I create a "kismet function", just like a material function ? Note: I'd rather avoid using UnrealScript. I don't even know where to type UnrealScripts, don't know where the documentation is and more generally don't have enough time to invest in learning UnrealScript. This "kismet function" feature must be usable by graphists (with little programming knowledge). If a (simple) script suffices to add this feature in the Kismet editor, so that one can create several "functions" without using UnrealScript, then fine, but I don't really want to have to write a script each time I want to factorize a few nodes. Thanks for any information !

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• Do cross reference database tables have a place in domain driven design?

  - by Mike Cellini

  First some background. Let's say we have a system where a customer is placing an order in a web interface. The items that customer is ordering can priced in various ways. Sometimes including the cost of delivery and sometimes not at all. That pricing effectively depends on a variety of factors including the vendor's own pricing model, that vendor's individual contracts with customers as well as that vendor's contracts with its own suppliers. Let's assume that once a customer places an order for a particular item and chooses a contract if any, the method of delivery can be determined by variables on those contracts. Those delivery methods also live in their own table in the database and have various properties consumed downstream. It makes sense that a cross reference or lookup table would store that information. That table would be loaded into the domain and could then be used to apply the appropriate delivery method while processing the order. Does this make sense in the context of domain driven design? Or is my thinking too relational? Is this logic that should be built into it's own class/method (I mean beyond apply the cross reference table data)?

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• Pure functional programming and game state

  - by Fu86

  Is there a common technique to handle state (in general) in a functional programming language? There are solutions in every (functional) programming language to handle global state, but I want to avoid this as far as I could. All state in a pure functional manner are function parameters. So I need to put the whole game state (a gigantic hashmap with the world, players, positions, score, assets, enemies, ...)) as a parameter to all functions which wants to manipulate the world on a given input or trigger. The function itself picks the relevant information from the gamestate blob, do something with it, manipulate the gamestate and return the gamestate. But this looks like a poor mans solution for the problem. If I put the whole gamestate into all functions, there is no benefit for me in contrast to global variables or the imperative approach. I could put just the relevant information into the functions and return the actions which will be taken for the given input. And one single function apply all the actions to the gamestate. But most functions need a lot of "relevant" information. move() need the object position, the velocity, the map for collision, position of all enemys, current health, ... So this approach does not seem to work either. So my question is how do I handle the massive amount of state in a functional programming language -- especially for game development?

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• Should I expose IObservable<T> on my interfaces?

  - by Alex

  My colleague and I have dispute. We are writing a .NET application that processes massive amounts of data. It receives data elements, groups subsets of them into blocks according to some criterion and processes those blocks. Let's say we have data items of type Foo arriving some source (from the network, for example) one by one. We wish to gather subsets of related objects of type Foo, construct an object of type Bar from each such subset and process objects of type Bar. One of us suggested the following design. Its main theme is exposing IObservable objects directly from the interfaces of our components. // ********* Interfaces ********** interface IFooSource { // this is the event-stream of objects of type Foo IObservable<Foo> FooArrivals { get; } } interface IBarSource { // this is the event-stream of objects of type Bar IObservable<Bar> BarArrivals { get; } } / ********* Implementations ********* class FooSource : IFooSource { // Here we put logic that receives Foo objects from the network and publishes them to the FooArrivals event stream. } class FooSubsetsToBarConverter : IBarSource { IFooSource fooSource; IObservable<Bar> BarArrivals { get { // Do some fancy Rx operators on fooSource.FooArrivals, like Buffer, Window, Join and others and return IObservable<Bar> } } } // this class will subscribe to the bar source and do processing class BarsProcessor { BarsProcessor(IBarSource barSource); void Subscribe(); } // ******************* Main ************************ class Program { public static void Main(string[] args) { var fooSource = FooSourceFactory.Create(); var barsProcessor = BarsProcessorFactory.Create(fooSource) // this will create FooSubsetToBarConverter and BarsProcessor barsProcessor.Subscribe(); fooSource.Run(); // this enters a loop of listening for Foo objects from the network and notifying about their arrival. } } The other suggested another design that its main theme is using our own publisher/subscriber interfaces and using Rx inside the implementations only when needed. //********** interfaces ********* interface IPublisher<T> { void Subscribe(ISubscriber<T> subscriber); } interface ISubscriber<T> { Action<T> Callback { get; } } //********** implementations ********* class FooSource : IPublisher<Foo> { public void Subscribe(ISubscriber<Foo> subscriber) { /* ... */ } // here we put logic that receives Foo objects from some source (the network?) publishes them to the registered subscribers } class FooSubsetsToBarConverter : ISubscriber<Foo>, IPublisher<Bar> { void Callback(Foo foo) { // here we put logic that aggregates Foo objects and publishes Bars when we have received a subset of Foos that match our criteria // maybe we use Rx here internally. } public void Subscribe(ISubscriber<Bar> subscriber) { /* ... */ } } class BarsProcessor : ISubscriber<Bar> { void Callback(Bar bar) { // here we put code that processes Bar objects } } //********** program ********* class Program { public static void Main(string[] args) { var fooSource = fooSourceFactory.Create(); var barsProcessor = barsProcessorFactory.Create(fooSource) // this will create BarsProcessor and perform all the necessary subscriptions fooSource.Run(); // this enters a loop of listening for Foo objects from the network and notifying about their arrival. } } Which one do you think is better? Exposing IObservable and making our components create new event streams from Rx operators, or defining our own publisher/subscriber interfaces and using Rx internally if needed? Here are some things to consider about the designs: In the first design the consumer of our interfaces has the whole power of Rx at his/her fingertips and can perform any Rx operators. One of us claims this is an advantage and the other claims that this is a drawback. The second design allows us to use any publisher/subscriber architecture under the hood. The first design ties us to Rx. If we wish to use the power of Rx, it requires more work in the second design because we need to translate the custom publisher/subscriber implementation to Rx and back. It requires writing glue code for every class that wishes to do some event processing.

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• Java game design question (graphical objects)

  - by vemalsar

  Hello Guys, I'm beginner in game development, in Java and here on this site too and I have a game design question. Please comment my idea: I have a main loop which call update and draw method. I want to use an ArrayList which store graphical objects, they have coordinate and image or text to draw and my game objects extends this class. In update, I can choose which objects should be put in the array and in draw method I'll display the elements of array on the screen. I'm using a buffer and draw first there, but it is not important now I guess...Here is a simple (not full) code, only the logic: public class GamePanel extends JPanel implements KeyListener { ArrayList<graphicalObjects> graphArray = new ArrayList<graphicalObjects>(); public void update() { //change the game scene, update the graphArray, process input etc. } public void draw() { //draws every element of graphArray to a JPanel } public static main(String[] args) { while(true) { update(); draw(); } } } My questions: Should have I use interface or abstract class for graphicalObjects? graphicalObjects class and the ArrayList really needs or there is some better solution? How to draw objects? They draw themself with their own method or in the draw method I have to draw manually based on graphicalObjects variables (x,y coordinates, image etc.)? If this conception is wrong, please suggest another one! All comments are welcome and sorry if this is dumb question, thanks!

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• Reasons behind polymorphism related behaviour in java

  - by Shades88

  I read this code somewhere class Foo { public int a; public Foo() { a = 3; } public void addFive() { a += 5; } public int getA() { System.out.println("we are here in base class!"); return a; } } public class Polymorphism extends Foo{ public int a; public Poylmorphism() { a = 5; } public void addFive() { System.out.println("we are here !" + a); a += 5; } public int getA() { System.out.println("we are here in sub class!"); return a; } public static void main(String [] main) { Foo f = new Polymorphism(); f.addFive(); System.out.println(f.getA()); // SOP 1 System.out.println(f.a); // SOP 2 } } For SOP1 we get answer 10 and for SOP2 we get answer 3. Reason for this is that you can't override variables whereas you can do so for methods. This happens because type of the reference variable is checked when a variable is accessed and type of the object is checked when a method is accessed. But I am wondering, just why is it that way? Can anyone explain me what is the reason for this behaviour

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• Instead of the specified Texture, black circles on a green background are getting rendered. Why?

  - by vinzBad

  I'm trying to render a Texture via OpenGL. But instead of the texture black circles on a green background are rendered. (They scale, depending what the rotation of the texture is) Example: The texture I'm trying to render is the following: This is the code I use to render the texture, it's located in my Sprite-class. public void Render() { Matrix4 matrix = Matrix4.CreateTranslation(-OriginX, -OriginY, 0) * Matrix4.CreateRotationZ(Rotation) * Matrix4.CreateTranslation(X, Y, 0); Vector2[] corners = { new Vector2(0,0), //top left new Vector2(Width ,0),//top right new Vector2(Width,Height),//bottom rigth new Vector2(0,Height)//bottom left }; //copy the corners to the uv coordinates Vector2[] uv = corners.ToArray<Vector2>(); //transform the coordinates for (int i = 0; i < 4; i++) corners[i] = new Vector2(Vector3.Transform(new Vector3(corners[i]), matrix)); //GL.Color3(TintColor); GL.BindTexture(TextureTarget.Texture2D, _ID); GL.Begin(BeginMode.Quads); { for (int i = 0; i < 4; i++) { GL.TexCoord2(uv[i]); GL.Vertex3(corners[i].X, corners[i].Y, _layerDepth); } } GL.End(); if (EnableDebugDraw) { GL.Color3(Color.Violet); GL.PointSize(3); GL.Begin(BeginMode.Points); { for (int i = 0; i < 4; i++) GL.Vertex2(corners[i]); } GL.End(); GL.Color3(Color.Green); GL.Begin(BeginMode.Points); GL.Vertex2(X, Y); GL.End(); } } This is how I setup OpenGL. public static void SetupGL() { GL.Enable(EnableCap.AlphaTest); GL.AlphaFunc(AlphaFunction.Greater, 0.1f); GL.Enable(EnableCap.Texture2D); GL.Hint(HintTarget.PerspectiveCorrectionHint, HintMode.Nicest); } With this function I load the texture: public static uint LoadTexture(string path) { uint id; GL.GenTextures(1, out id); GL.BindTexture(TextureTarget.Texture2D, id); Bitmap bitmap = new Bitmap(path); BitmapData data = bitmap.LockBits(new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb); GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, data.Width, data.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0); bitmap.UnlockBits(data); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear); return id; } And here I call Sprite.Render() protected override void OnRenderFrame(FrameEventArgs e) { GL.ClearColor(Color.MidnightBlue); GL.Clear(ClearBufferMask.ColorBufferBit); _sprite.Render(); SwapBuffers(); base.OnRenderFrame(e); } As I stole this code from the Textures-Example from OpenTK, I don't understand why this doesn't work.

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• What language available on commodity web hosts would suit a C# developer? [closed]

  - by billpg

  Recognising its ubiquity on commodity web hosting services, I tried developing in PHP a few years ago. I really didn't like it, later deciding that life was too short for PHP. (In brief, having to put $ on variable names; mis-spelt variable names become new variables; converting non-numeric strings to integers without complaint; the need for an "and this time I mean it" comparison operator.) In my ideal world, commodity web hosts would all support C#/ASP.NET, my preferred web-development language and framework, but this is not my ideal world. Even Mono has barely made a dent on Linux based hosts. However, last time I moaned about PHP's ubiquity, someone followed up that this was no longer the case, and that many other languages are now commonly usable on web hosts too. What programming language; a. Would suit a developer who prefers C#. b. Is available to run on many web hosts.

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• Need help: jBPM installation issue

  - by Kouky

  This is Ms Kahina, I’m getting started with jBPM & Java EE, I tried to install the jBPM 5.4 version by following all the steps stated in the iBPM user guide as below: 1- I’ve installed Java (JDK 1.7) and ant ( Apache-ant-1.9.4). 2- I’ve set both JAVA_HOME and ANT_HOME environement variables. 3- I’ve downloaded the jBPM 5.4 full installer and run the installation script “ant install.demo” and after that the start script “ant start.demo”. But unfortunately jBPM 5.4 is not working. When running the installation Script I’m getting successful message but with the following warnings : [copy] Warning: Could not find file C:\jbpm-installer\db\task-persistence.xml to copy. [copy] Warning: Could not find file C:\jbpm-installer\db\Taskorm.xml to copy. The start demo was successful. Actually when I try to open any tool provided with the jBPM such us the jBPM-console for example I’m getting the following messages: Address not found or sometimes the http status 404 occurred even if the Welcome page of jBoss AS was opened at http://localhost:8080/. Please need your assistance to sort out this issue in order to move forward in my project as I'm blocked in the installation stage since more than a week now, I don’t know if this is related to the jBoss AS7 or to any other thing that I didn’t find out. Looking forward to hearing from you. Thanks Kahina

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• How to debug a fatal system crash - [graphical loop DOTA2]?

  - by Huw

  Whilst playing DOTA2, I occasionally and apparently randomly seem to be experiencing a fatal crash where the display freezes fixed and the audio loops over approx the last .5 of a second. Now, I'm interested in resolving this - but my trouble is I don't know where to start. The error appears non-reproducible (I've tried returning to games and deploying the same combination of events in hopes of pinning to to a certain shader etc), and I don't know which part of 'the stack' it might be coming from. Variables that occur to me: I custom build this system, did I do something wrong - is my PSU not providing enough power to the graphics card? I am running Steam and DOTA under Linux, could this new software have a bug Might it be something to do with my ATI Catalyst graphics drivers Is some other background process interfering I'm usually mid game when this occurs, so i quickly kill the power and reboot (when i'm lucky i can get back in with only 1-2 mins lost!). So my question here relates to logs. Where should I start to look or how might I set up logs to help me pin down a fatal crash of this kind by recording moments up to / before a crash and is this likely to be something I should push Steam to do, or is there something at a system level? Then perhaps I can return with a more specific question and perhaps even a bug report :) Many thanks in advance.

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• why my code still cannot connect with database? [closed]

  - by Wen Teng

  package com.mems.travis; import java.util.ArrayList; import java.util.List; import org.apache.http.NameValuePair; import org.apache.http.message.BasicNameValuePair; import org.json.JSONObject; import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.content.Intent; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.RadioButton; public class UserRegister extends Activity { JSONParser jsonParser = new JSONParser(); EditText inputName; EditText inputUsername; EditText inputEmail; EditText inputPassword; RadioButton button1; RadioButton button2; Button button3; int success = 0; // url to create new product private static String url_register_user = "http://192.168.1.100/MEMS/add_user.php"; // JSON Node names private static final String TAG_SUCCESS = "success"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_user_register); // Edit Text inputName = (EditText) findViewById(R.id.nameTextBox); inputUsername = (EditText) findViewById(R.id.usernameTextBox); inputEmail = (EditText) findViewById(R.id.emailTextBox); inputPassword = (EditText) findViewById(R.id.pwTextBox); // Create button //RadioButton button1 = (RadioButton) findViewById(R.id.studButton); // RadioButton button2 = (RadioButton) findViewById(R.id.shopownerButton); Button button3 = (Button) findViewById(R.id.regSubmitButton); // button click event button3.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { String name = inputName.getText().toString(); String username = inputUsername.getText().toString(); String email = inputEmail.getText().toString(); String password = inputPassword.getText().toString(); if (name.contentEquals("")||username.contentEquals("")||email.contentEquals("")||password.contentEquals("")) { AlertDialog.Builder builder = new AlertDialog.Builder(UserRegister.this); // 2. Chain together various setter methods to set the dialog characteristics builder.setMessage(R.string.nullAlert) .setTitle(R.string.alertTitle); builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { // User clicked OK button } }); // 3. Get the AlertDialog from create() AlertDialog dialog = builder.show(); } else { new RegisterNewUser().execute(); } } }); } class RegisterNewUser extends AsyncTask<String, String, String>{ protected String doInBackground(String... args) { String name = inputName.getText().toString(); String username = inputUsername.getText().toString(); String email = inputEmail.getText().toString(); String password = inputPassword.getText().toString(); // Building Parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("name", name)); params.add(new BasicNameValuePair("username", username)); params.add(new BasicNameValuePair("email", email)); params.add(new BasicNameValuePair("password", password)); // getting JSON Object // Note that create product url accepts POST method JSONObject json = jsonParser.makeHttpRequest(url_register_user, "GET", params); // check log cat for response Log.d("Send Notification", json.toString()); try { int success = json.getInt(TAG_SUCCESS); if (success == 1) { // successfully created product Intent i = new Intent(getApplicationContext(), StudentLogin.class); startActivity(i); finish(); } else { // failed to register } } catch (Exception e) { e.printStackTrace(); } return null; } } }

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