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• Career advice: stay with PHP or start a new career in something else ( .Net?)

  - by Christian P

  I'm planning on moving to NY in 6-12 months tops, so I'm forced to find a new job. When I'm planing to start my life in another city it's also probably a good time to think about career changes. I've found a lot of different opinions about PHP vs .Net vs Java and this is not topic here. I don't want to start a new fight about which language is better. Knowing programming language is not the most important thing for being a software developer. To be a really good developer you need to know OOP, design patterns, testing... and language is just a tool to make things happen. So back to my question. I have mixed experience in IT - 1 year as an IT support guy (Windows administration and support), around 2 years of experience in embedded programming (VB.Net 2005) and for the last 2 years I'm working with PHP/MySQL. I have worked with Magento web shop, assisted in some projects in Symfony, modified few Drupal sites. My main concerns are following: Do I continue to improve my skills in PHP e.g. to start learning some major PHP framework like Zend, Symfony maybe get some PHP certification. Or do I start learning .NET or Java. I'm more familiar to .NET so I'll probably choose it if choice falls between .NET and Java ( or you could convince me to choose Java :). Career-wise, I don't know what is the best choice. Learning new framework and language is more time consuming then improving my existing skills in PHP. But with .NET you have a lot of possibilities (Windows 7 Phone development, Silverlight, WPF) and possibly bigger chances to find better jobs. PHP jobs are less payed then .NET, at least, according to my researches (correct me if I'm wrong). But if I start now with .NET I'm just a beginner and my salary will be low. I need at least 2+ years of experience in some language to even try to find some job that is paying higher than $50-60k in NY. My main goal in next 2-3 years is to try to find a job in a $60-80k category. Don't get me wrong, I'm not just chasing money, but money is an important factor when you're trying to start a family. I'm 27 years old and I feel that there isn't a lot of room for wrong decisions regarding my career, so any advice will be very welcome. Update Thank you all for spending time to help me with my problem. All of the answers and comments have been very helpful. I have decided to stick with PHP but also to learn C# and Silverlight 4. We'll see where the life will take me.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• More elegant way to avoid hard coding the format of a a CSV file?

  - by dsollen

  I know this is trivial issue, but I just feel this can be more elegant. So I need to write/read data files for my program, lets say they are CSV for now. I can implement the format as I see fit, but I may have need to change that format later. The simply thing to do is something like out.write(For.getValue()+","+bar.getMinValue()+","+fi.toString()); This is easy to write, but obviously is guilty of hard coding and the general 'magic number' issue. The format is hard-coded, requires parsing of the code to figure out the file format, and changing the format requires changing multiple methods. I could instead have my constants specifying the location that I want each variable to be saved in the CSV file to remove some of the 'magic numbers'; then save/load into the an array at the location specified by the constants: int FOO_LOCATION=0; int BAR_MIN_VAL_LOCATION=1; int FI_LOCATION=2 int NUM_ARGUMENTS=3; String[] outputArguments=new String[NUM_ARGUMENTS]; outputArguments[FOO_LOCATION] = foo.getValue(); outputArgumetns[BAR_MIN_VAL_LOCATION] = bar.getMinValue(); outptArguments[FI_LOCATOIN==fi.toString(); writeAsCSV(outputArguments); But this is...extremely verbose and still a bit ugly. It makes it easy to see the format of existing CSV and to swap the location of variables within the file easily. However, if I decide to add an extra value to the csv I need to not only add a new constant, but also modify the read and write methods to add the logic that actually saves/reads the argument from the array; I still have to hunt down every method using these variables and change them by hand! If I use Java enums I can clean this up slightly, but the real issue is still present. Short of some sort of functional programming (and java's inner classes are too ugly to be considered functional) I still have no obvious way of clearly expressing what variable is associated with each constant short of writing (and maintaining) it in the read/write methods. For instance I still need to write somewhere that the FOO_LOCATION specifies the location of foo.getValue(). It seems as if there should be a prettier, easier to maintain, manner for approaching this? Incidentally, I'm working in java at the moment, however, I am interested conceptually about the design approach regardless of language. Some library in java that does all the work for me is definitely welcome (though it may prove more hassle to get permission to add it to the codebase then to just write something by hand quickly), but what I'm really asking is more about how to write elegant code if you had to do this by hand.

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• Generic Adjacency List Graph implementation

  - by DmainEvent

  I am trying to come up with a decent Adjacency List graph implementation so I can start tooling around with all kinds of graph problems and algorithms like traveling salesman and other problems... But I can't seem to come up with a decent implementation. This is probably because I am trying to dust the cobwebs off my data structures class. But what I have so far... and this is implemented in Java... is basically an edgeNode class that has a generic type and a weight-in the event the graph is indeed weighted. public class edgeNode<E> { private E y; private int weight; //... getters and setters as well as constructors... } I have a graph class that has a list of edges a value for the number of Vertices and and an int value for edges as well as a boolean value for whether or not it is directed. The brings up my first question, if the graph is indeed directed, shouldn't I have a value in my edgeNode class? Or would I just need to add another vertices to my LinkedList? That would imply that a directed graph is 2X as big as an undirected graph wouldn't it? public class graph { private List<edgeNode<?>> edges; private int nVertices; private int nEdges; private boolean directed; //... getters and setters as well as constructors... } Finally does anybody have a standard way of initializing there graph? I was thinking of reading in a pipe-delimited file but that is so 1997. public graph GenereateGraph(boolean directed, String file){ List<edgeNode<?>> edges; graph g; try{ int count = 0; String line; FileReader input = new FileReader("C:\\Users\\derekww\\Documents\\JavaEE Projects\\graphFile"); BufferedReader bufRead = new BufferedReader(input); line = bufRead.readLine(); count++; edges = new ArrayList<edgeNode<?>>(); while(line != null){ line = bufRead.readLine(); Object edgeInfo = line.split("|")[0]; int weight = Integer.parseInt(line.split("|")[1]); edgeNode<String> e = new edgeNode<String>((String) edges.add(e); } return g; } catch(Exception e){ return null; } } I guess when I am adding edges if boolean is true I would be adding a second edge. So far, this all depends on the file I write. So if I wrote a file with the following Vertices and weights... Buffalo | 18 br Pittsburgh | 20 br New York | 15 br D.C | 45 br I would obviously load them into my list of edges, but how can I represent one vertices connected to the other... so on... I would need the opposite vertices? Say I was representing Highways connected to each city weighted and un-directed (each edge is bi-directional with weights in some fictional distance unit)... Would my implementation be the best way to do that? I found this tutorial online Graph Tutorial that has a connector object. This appears to me be a collection of vertices pointing to each other. So you would have A and B each with there weights and so on, and you would add this to a list and this list of connectors to your graph... That strikes me as somewhat cumbersome and a little dismissive of the adjacency list concept? Am I wrong and that is a novel solution? This is all inspired by steve skiena's Algorithm Design Manual. Which I have to say is pretty good so far. Thanks for any help you can provide.

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• Procedual level generation for a platformer game (tilebased) using player physics

  - by Notbad

  I have been searching for information about how to build a 2d world generator (tilebased) for a platformer game I am developing. The levels should look like dungeons with a ceiling and a floor and they will have a high probability of being just made of horizontal rooms but sometimes they can have exits to a top/down room. Here is an example of what I would like to achieve. I'm refering only to the caves part. I know level design won't be that great when generated but I think it is possible to have something good enough for people to enjoy the procedural maps (Note: Supermetrod Spoiler!): http://www.snesmaps.com/maps/SuperMetroid/SuperMetroidMapNorfair.html Well, after spending some time thinking about this I have some ideas to create the maps that I would like to share with you: 1) I have read about celular automatas and I would like to use them to carve the rooms but instead of carving just a tile at once I would like to carve full columns of tiles. Of course this carving system will have some restrictions like how many tiles must be left for the roof and the ceiling, etc... This way I could get much cleaner rooms than using the ussual automata. 2) I want some branching into the rooms. It will have little probability to happen but I definitely want it. Thinking about carving I came to the conclusion that I could be using some sort of path creation algorithm that the carving system would follow to create a path in the rooms. This could be more noticiable if we make the carving system to carve columns with the height of a corridor or with the height of a wide room (this will be added to the system as a param). This way at some point I could spawn a new automa beside the main one to create braches. This new automata should play side by side with the first one to create dead ends, islands (both paths created by the automatas meet at some point or lead to the same room. It would be too long to explain here all the tests I have done, etc... just will try to summarize the problems to see if anyone could bring some light to solve them (I don't mind sharing my successes but I think they aren't too relevant): 1) Zone reachability: How can I make sure that the player will be able to reach all zones I created (mainly when branches happen or vertical rooms are created). When branches are created I have to make sure that there will be a way to get onto the new created branch. I mean a bifurcation that the player could follow. Player will follow the main path or jump to a platform to get onto the other way). On the other hand if an island is created by the meeting of both branches I need to make sure the player will be able to get onto the island too. 2) When a branch is created and corridors are generated for each branch how can I make then both merge or repel to create an island or just make them separated corridors. 3) When I create a branch and an island is created becasue both corridors merge at somepoint or they lead to the same room, is there any way to detect this and randomize where to create the needed platforms to get onto the created isle? This platforms could be created at the start of the island or at the end. I guess part of the problem could be solved using some sort of graph following the created paths but I'm a bit lost in this sea of precedural content creation :). On the other hand I don't expect a solution to the problem but some information to get me moving forward again. Thanks in advance.

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• Taking a Chomp out of a (Social Network) Product Hype

  - by kellsey.ruppel

  Andrew Kershaw, Senior Director Oracle Social Network Product Development, speaks about Oracle Social Network One of our competitors is being very aggressive with its own developed Social Network add-on, but there should be no doubt in the minds that the Oracle social capabilities available with Fusion CRM stack up well against it. Within the Oracle Cloud, we have announced a product called Oracle Social Network. That technology is pre-integrated into Fusion Applications, enabling your customer to build a collaborative and social enterprise (without all the noise!). Oracle Social Network is designed together with our Fusion Applications. It is very conveniently pre-integrated with CRM, HCM, Financials, Projects, Supply Chain, and the Fusion family. But what's even better is that the individual teams can take a considered approach to what they are trying to achieve within the collaboration process and the outcome they are trying to enable. Then they can utilize the network and collaboration tools to support that result. And there's more! The Fusion teams can design social interactions that bridge across and outside their individual product lines because we have more than just a product line and they know they have the social network to connect them. I know we have a superior product, but it is our ability to understand and execute across the enterprise that will enable us to deliver a much more robust and capable platform in the short term than our competitor can. We have built a product specifically designed for enterprise social collaboration which is not the same for the competition. We have delivered a much more effective solution - one in which individuals can easily collaborate to get results, while being confident that they know who has access to their information. Our platform has been pre-built to cross the company boundaries and enable our customers to collaborate, not just with their customers, but with their partners and suppliers as well. So Fusion addresses the combination of the enterprise application suite with enterprise collaboration and social networking. Oracle Social Network already has a feature function advantage over our competitor's tool providing a real added value to the employees. Plus Oracle has the ability to execute in a broad enterprise and cross-enterprise way that our competitors cannot. We have the power of a tool that provides the core social fabric across all of the applications, as well as supporting enterprise collaboration. That allows us to provide intelligent business insight, connections, and recommendations that our competitor simply can't. From our competitors, customers get integration for Sales; they get integration for Service, but then they have to integrate every other enterprise asset that they have by themselves. With Oracle, we are doing the integration. Fusion Applications will be pre-integrated, and over time, all of the applications in the business suite, including our Applications Unlimited and specialist industry applications, will connect to the Oracle Social Network. I'm confident these capabilities make Oracle Social Network the only collaboration platform on which to deliver the social enterprise.

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• Keeping your options open in a cloud solution

  - by BuckWoody

  In on-premises solutions we have the full range of options open for a given computing solution – but we don’t always take advantage of them, for multiple reasons. Data goes in a Relational Database Management System, files go on a share, and e-mail goes to the Exchange server. Over time, vendors (including ourselves) add in functionality to one product that allow non-standard use of the platform. For example, SQL Server (and Oracle, and others) allow large binary storage in or through the system – something not originally intended for an RDBMS to handle. There are certainly times when this makes sense, of course, but often these platform hammers turn every problem into a nail. It can make us “lazy” in our design – we sometimes don’t take the time to learn another architecture because the one we’ve spent so much time with can handle what we want to do. But there’s a distinct danger here. In nature, when a population shares too many of the same traits, it can cause a complete collapse if a situation exploits a weakness shared by that population. The same is true with not using the righttool for the job in a computing environment. Your company or organization depends on your knowledge as a professional to select the best mix of supportable, flexible, cost-effective technologies to solve their problems, whether you’re in an architect role or not.  So take some time today to learn something new. The way I do this is to select a given problem, and try to solve it with a technology I’m not familiar with. For instance – create a Purchase Order system in Excel, then in Hadoop or MongoDB, or even in flat-files using PowerShell as an interface. No, I’m not suggesting any of these architectures are the proper way to solve the PO problem, but taking something concrete that you know well and applying that meta-knowledge to another platform will assist you in exercising the “little grey cells” and help you and your organization understand what is open to you. And of course you can do all of this on-premises – but my recommendation is to check out a cloud platform (my suggestion would of course be Windows Azure :) ) and try it there. Most providers (including Microsoft) provide free time to do that.

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• How to get around the Circular Reference issue with JSON and Entity

  - by DanScan

  I have been experimenting with creating a website that leverages MVC with JSON for my presentation layer and Entity framework for data model/database. My Issue comes into play with serializing my Model objects into JSON. I am using the code first method to create my database. When doing the code first method a one to many relationship (parent/child) requires the child to have a reference back to the parent. (Example code my be a typo but you get the picture) class parent { public List<child> Children{get;set;} public int Id{get;set;} } class child { public int ParentId{get;set;} [ForeignKey("ParentId")] public parent MyParent{get;set;} public string name{get;set;} } When returning a "parent" object via a JsonResult a circular reference error is thrown because "child" has a property of class parent. I have tried the ScriptIgnore attribute but I lose the ability to look at the child objects. I will need to display information in a parent child view at some point. I have tried to make base classes for both parent and child that do not have a circular reference. Unfortunately when I attempt to send the baseParent and baseChild these are read by the JSON Parser as their derived classes (I am pretty sure this concept is escaping me). Base.baseParent basep = (Base.baseParent)parent; return Json(basep, JsonRequestBehavior.AllowGet); The one solution I have come up with is to create "View" Models. I create simple versions of the database models that do not include the reference to the parent class. These view models each have method to return the Database Version and a constructor that takes the database model as a parameter (viewmodel.name = databasemodel.name). This method seems forced although it works. NOTE:I am posting here because I think this is more discussion worthy. I could leverage a different design pattern to over come this issue or it could be as simple as using a different attribute on my model. In my searching I have not seen a good method to overcome this problem. My end goal would be to have a nice MVC application that heavily leverages JSON for communicating with the server and displaying data. While maintaining a consistant model across layers (or as best as I can come up with).

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• If most of team can't follow the architecture, what do you do?

  - by Chris

  Hi all, I'm working on a greenfields project with two other developers. We're all contractors, and myself and one other just started working on the project while the orginal one has been doing most of the basic framework coding. In the past month, my fellow programmer and I have been just frustrated by the design descisions done by our co-worker. Here's a little background information: The application at face value appeared to be your standard n-layered web application using C# on the 3.5 framework. We have a data layer, business layer and a web interface. But as we got deeper into the project we found some very interesting things that have caused us some troubles. There is a custom data access sqlHelper type base which only accepts dictionary key/valued entries and returns only data tables. There are no entity objects, but there are some massive objects which do everything and then are tossed into session for persitance. The general idea is that the pages (.aspx) don't do anything, while the controls (.ascx) do everything. The general flow is that a client clicks on a button, which goes to a user control base which passes a process request to the 'BLL' class which goes to the page processor, which then goes to a getControlProcessor, which at last actually processes the request. The request itself is made up of a dictionary which is passing a string valued method name, stored procedure name, a control name and possibly a value. All switching of the processing is done by comparing the string values of the control names and method names. Pages are linked together via a common header control that uses a combination of javascript and tables to create a hyperlink effect. And as I found out yesterday, a simple hyperlink between one page and another does not work because of the need to have quite a bit of information in session to determine which control to display on a page. My fellow programmer and I both believe that this is a strange and uncommon approach to web application development. Both of us have been in this business for over five years and neither of us have seen this approach. My question is this, how would we approach our co-worker and voice our concerns and what should we do if he does not want to accept the criteic? We both do not want to insult the work that has been done, but feel that going forward will create a nightmare for development. Thanks for your comments.

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• Why can't the IT industry deliver large, faultless projects quickly as in other industries?

  - by MainMa

  After watching National Geographic's MegaStructures series, I was surprised how fast large projects are completed. Once the preliminary work (design, specifications, etc.) is done on paper, the realization itself of huge projects take just a few years or sometimes a few months. For example, Airbus A380 "formally launched on Dec. 19, 2000", and "in the Early March, 2005", the aircraft was already tested. The same goes for huge oil tankers, skyscrapers, etc. Comparing this to the delays in software industry, I can't help wondering why most IT projects are so slow, or more precisely, why they cannot be as fast and faultless, at the same scale, given enough people? Projects such as the Airbus A380 present both: Major unforeseen risks: while this is not the first aircraft built, it still pushes the limits if the technology and things which worked well for smaller airliners may not work for the larger one due to physical constraints; in the same way, new technologies are used which were not used yet, because for example they were not available in 1969 when Boeing 747 was done. Risks related to human resources and management in general: people quitting in the middle of the project, inability to reach a person because she's on vacation, ordinary human errors, etc. With those risks, people still achieve projects like those large airliners in a very short period of time, and despite the delivery delays, those projects are still hugely successful and of a high quality. When it comes to software development, the projects are hardly as large and complicated as an airliner (both technically and in terms of management), and have slightly less unforeseen risks from the real world. Still, most IT projects are slow and late, and adding more developers to the project is not a solution (going from a team of ten developer to two thousand will sometimes allow to deliver the project faster, sometimes not, and sometimes will only harm the project and increase the risk of not finishing it at all). Those which are still delivered may often contain a lot of bugs, requiring consecutive service packs and regular updates (imagine "installing updates" on every Airbus A380 twice per week to patch the bugs in the original product and prevent the aircraft from crashing). How can such differences be explained? Is it due exclusively to the fact that software development industry is too young to be able to manage thousands of people on a single project in order to deliver large scale, nearly faultless products very fast?

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• CI tests to enforce specific development rules - good practice?

  - by KeithS

  The following is all purely hypothetical and any particular portion of it may or may not accurately describe real persons or situations, whether living, dead or just pretending. Let's say I'm a senior dev or architect in charge of a dev team working on a project. This project includes a security library for user authentication/authorization of the application under development. The library must be available for developers to edit; however, I wish to "trust but verify" that coders are not doing things that could compromise the security of the finished system, and because this isn't my only responsibility I want it to be done in an automated way. As one example, let's say I have an interface that represents a user which has been authenticated by the system's security library. The interface exposes basic user info and a list of things the user is authorized to do (so that the client app doesn't have to keep asking the server "can I do this?"), all in an immutable fashion of course. There is only one implementation of this interface in production code, and for the purposes of this post we can say that all appropriate measures have been taken to ensure that this implementation can only be used by the one part of our code that needs to be able to create concretions of the interface. The coders have been instructed that this interface and its implementation are sacrosanct and any changes must go through me. However, those are just words; the security library's source is open for editing by necessity. Any of my devs could decide that this secured, private, hash-checked implementation needs to be public so that they could do X, or alternately they could create their own implementation of this public interface in a different library, exposing the hashing algorithm that provides the secure checksum, in order to do Y. I may not be made aware of these changes so that I can beat the developer over the head for it. An attacker could then find these little nuggets in an unobfuscated library of the compiled product, and exploit it to provide fake users and/or falsely-elevated administrative permissions, bypassing the entire security system. This possibility keeps me awake for a couple of nights, and then I create an automated test that reflectively checks the codebase for types deriving from the interface, and fails if it finds any that are not exactly what and where I expect them to be. I compile this test into a project under a separate folder of the VCS that only I have rights to commit to, have CI compile it as an external library of the main project, and set it up to run as part of the CI test suite for user commits. Now, I have an automated test under my complete control that will tell me (and everyone else) if the number of implementations increases without my involvement, or an implementation that I did know about has anything new added or has its modifiers or those of its members changed. I can then investigate further, and regain the opportunity to beat developers over the head as necessary. Is this considered "reasonable" to want to do in situations like this? Am I going to be seen in a negative light for going behind my devs' backs to ensure they aren't doing something they shouldn't?

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• Pixels - A cry for some insight

  - by CarrotFile

  I'm pretty new to web developing and I'd love some clarification. Although reading more than one book on the topic, I cannot seem to wrap my head around the pixel concept. I encounter problems with this issue when trying to use CSS and pixel units for design that fits different screen sizes. To my understanding a pixel is the most basic unit used by a monitor in order to compose an image on the screen. So if me resolution is 800 by 600, everything on my screen is rendered using those 800*600 basic building blocks. If I were to enlarge my screen resolution, 3 things would accrue: A. The basic image building block(the pixel) would shrink in size B. The pixels would move close together C. Well, more pixels would now be available All these combined lead to a sharper(depending on the viewing distance) and more detail enabling image. Well so far so good. Here is were I start getting lost: To my knowledge a pixel is not a physical, real object. Monitors are not embedded with a few thousand pixels. I am drawn to this conclusion because anyone can change his screen's resolution, making a pixel on his screen bigger or smaller, and adding or subtracting the amount of total pixels on screen. Adding to that, I have herd that different monitors have different pixel densities. For example Apple's retina monitors. Taking all of the above as my knowledge base, These are my questions: If a pixel has no real world constant size, what does comparing different pixel densities matter? Each screen company can define it's own pixel concept and declare the higher density. What does a bigger pixel density mean? Say we take two screens with the same physical dimensions, but with a different pixel density, am I to assert that the main difference would be the larger density screen being able to display a higher max resolution? Or am I to assert that given the same resolution on both monitors, the higher density one would display a sharper, smaller image? If a pixel is not a fixed size within one monitor, is it a fixed size between the same resolution on two different monitors? For example, would two different monitors, set to the same resolution, be comprised of same size, same quantity pixels? I'd love some help (:

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• Is return-type-(only)-polymorphism in Haskell a good thing?

  - by dainichi

  One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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• Multidimensional multiple-choice knapsack problem: find a feasible solution

  - by Onheiron

  My assignment is to use local search heuristics to solve the Multidimensional multiple-choice knapsack problem, but to do so I first need to find a feasible solution to start with. Here is an example problem with what I tried so far. Problem R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 11.0 3 2 2 12.0 1 1 3 G2: 20.0 1 1 3 5.0 2 3 2 G3: 10.0 2 2 3 30.0 1 1 3 Sorting strategies To find a starting feasible solution for my local search I decided to ignore maximization of gains and just try to fit the resources requirements. I decided to sort the choices (strategies) in each group by comparing their "distance" from the multidimensional space origin, thus calculating SQRT(R1^2 + R2^2 + ... + RN^2). I felt like this was a keen solution as it somehow privileged those choices with resouce usages closer to each other (e.g. R1:2 R2:2 R3:2 < R1:1 R2:2 R3:3) even if the total sum is the same. Doing so and selecting the best choice from each group proved sufficent to find a feasible solution for many[30] different benchmark problems, but of course I knew it was just luck. So I came up with the problem presented above which sorts like this: R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 12.0 1 1 3 < select this 11.0 3 2 2 G2: 20.0 1 1 3 < select this 5.0 2 3 2 G3: 30.0 1 1 3 < select this 10.0 2 2 3 And it is not feasible because the resources consmption is R1:3, R2:3, R3:9. The easy solution is to pick one of the second best choices in group 1 or 2, so I'll need some kind of iteration (local search[?]) to find the starting feasible solution for my local search solution. Here are the options I came up with Option 1: iterate choices I tried to find a way to iterate all the choices with a specific order, something like G1 G2 G3 1 1 1 2 1 1 1 2 1 1 1 2 2 2 1 ... believeng that feasible solutions won't be that far away from the unfeasible one I start with and thus the number of iterations will keep quite low. Does this make any sense? If yes, how can I iterate the choices (grouped combinations) of each group keeping "as near as possibile" to the previous iteration? Option 2: Change the comparation term I tried to think how to find a better variable to sort the choices on. I thought at a measure of how "precious" a resource is based on supply and demand, so that an higer demand of a more precious resource will push you down the list, but this didn't help at all. Also I thought there probably isn't gonna be such a comparsion variable which assures me a feasible solution at first strike. I there such a variable? If not, is there a better sorting criteria anyways? Option 3: implement any known sub-optimal fast solving algorithm Unfortunately I could not find any of such algorithms online. Any suggestion?

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• How do I keep user input and rendering independent of the implementation environment?

  - by alex

  I'm writing a Tetris clone in JavaScript. I have a fair amount of experience in programming in general, but am rather new to game development. I want to separate the core game code from the code that would tie it to one environment, such as the browser. My quick thoughts led me to having the rendering and input functions external to my main game object. I could pass the current game state to the rendering method, which could render using canvas, elements, text, etc. I could also map input to certain game input events, such as move piece left, rotate piece clockwise, etc. I am having trouble designing how this should be implemented in my object. Should I pass references to functions that the main object will use to render and process user input? For example... var TetrisClone = function(renderer, inputUpdate) { this.renderer = renderer || function() {}; this.inputUpdate = input || function() {}; this.state = {}; }; TetrisClone.prototype = { update: function() { // Get user input via function passed to constructor. var inputEvents = this.inputUpdate(); // Update game state. // Render the current game state via function passed to constructor. this.renderer(this.state); } }; var renderer = function(state) { // Render blocks to browser page. } var inputEvents = {}; var charCodesToEvents = { 37: "move-piece-left" /* ... */ }; document.addEventListener("keypress", function(event) { inputEvents[event.which] = true; }); var inputUpdate = function() { var translatedEvents = [], event, translatedEvent; for (event in inputEvents) { if (inputEvents.hasOwnProperty(event)) { translatedEvent = charCodesToEvents[event]; translatedEvents.push(translatedEvent); } } inputEvents = {}; return translatedEvents; } var game = new TetrisClone(renderer, inputUpdate); Is this a good game design? How would you modify this to suit best practice in regard to making a game as platform/input independent as possible?

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• Curating projects of deceased friends

  - by Ant

  A very good friend of mine, and an avid programmer, recently passed away. He left nearly 40 projects on BitBucket. Most of them are public, but a few of them are marked as private. I've decided to take on curation duties for the projects rather than leave his work to disappear. If you have been in the same situation, what did you do? Did you open-source everything? Continue development? Delete it all? I'm very interested to hear other people's experiences. There are a few reasons why some of the projects are marked as private (private projects on BitBucket are visible only to invited users and the original creator): One of them is an iOS web app that was free in the app store. I've had to remove the app from the store as I'm shutting down his web sites as a favour to his widow. However, I've already made the app public under the GPL v3 (he was a big GPL supporter). One of them contains proprietary code. It can't be open-sourced. Others are very much work-in-progress. I don't know if he intended to make them into hosted, paid services or if he wanted to give the code away under an open-source licence when they were finished. Here's a list of the private projects: Some kind of living cell simulator that uses SBML along with Runge-Kutta and Euler algorithms to do... something. There's a fair amount of code here but I don't know what it does or how far along it is. No docs. An accountacy application; it seems to have a solid DB design behind it but there's little code on top of that. A website whose purpose is to suggest good restaurants. Built on yii. Seems to have a lot of code but I'd need to set up a WAMP stack to see how far along it is. A website intended to host memorials to people who suffered from the same problem he was. Built on Joomla. I'm not sure how much of the code is just Joomla and how much is custom; again, I'd need to get Joomla running to find out. I'd just introduced him to Mercurial and BitBucket. All of the private projects are single commits of codebases he wasn't using version control with/was previously using SVN. I don't have the SVN repositories so I can't see the commit logs.

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• The difference

  So with the CTP tools available, weve been building a few apps, just to get a feel for the tools and whats supported in the framework.  Whats been great is that everything is fairly familiar and consistent, largely to do with the .net framework and Microsofts focus on providing good tools.  Weve produced mobile applications, mostly in concept form, for Windows Phone Classic, iPhone and Android but never so quickly and not of such high quality and visual impression.  I attribute some of this obviously to our familiarity to the Microsoft platform and tools.  Though when you look at the designs our team has produced, it becomes clear that this is not just another mobile application container.                                                            The Metro design language implores content prominence with fluid motion and transitions, with a crisp font and easily organized features and services placement.  In addition to a purposeful right edge tease, where the intent is for users to discover new premium content and services.   The concept that enables this is called hubs, building application with hubs changes your thinking from a single mobile application task, to thinking creatively about a mobile experience. Its engaging to think of the other brands and industry verticals that will take advantage of this core feature.  Combine this with Windows Phone 7 live tiles, more on that later, and you have a recipe for a solid mobile services platform.                                                              This so much more fun and liberating than my icon on a gridDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Is my implementation of A* wrong?

  - by Bloodyaugust

  I've implemented the A* algorithm in my program. However, it would seem to be functioning incorrectly at times. Below is a screenshot of one such time. The obviously shorter line is to go immediately right at the second to last row. Instead, they move down, around the tower, and continue to their destination (bottom right from top left). Below is my actual code implementation: nodeMap.prototype.findPath = function(p1, p2) { var openList = []; var closedList = []; var nodes = this.nodes; for (var i = 0; i < nodes.length; i++) { //reset heuristics and parents for nodes var curNode = nodes[i]; curNode.f = 0; curNode.g = 0; curNode.h = 0; curNode.parent = null; if (curNode.pathable === false) { closedList.push(curNode); } } openList.push(this.getNode(p1)); while(openList.length > 0) { // Grab the lowest f(x) to process next var lowInd = 0; for(i=0; i<openList.length; i++) { if(openList[i].f < openList[lowInd].f) { lowInd = i; } } var currentNode = openList[lowInd]; if (currentNode === this.getNode(p2)) { var curr = currentNode; var ret = []; while(curr.parent) { ret.push(curr); curr = curr.parent; } return ret.reverse(); } closedList.push(currentNode); for (i = 0; i < openList.length; i++) { //remove currentNode from openList if (openList[i] === currentNode) { openList.splice(i, 1); break; } } for (i = 0; i < currentNode.neighbors.length; i++) { if(closedList.indexOf(currentNode.neighbors[i]) !== -1 ) { continue; } if (currentNode.neighbors[i].isPathable === false) { closedList.push(currentNode.neighbors[i]); continue; } var gScore = currentNode.g + 1; // 1 is the distance from a node to it's neighbor var gScoreIsBest = false; if (openList.indexOf(currentNode.neighbors[i]) === -1) { //save g, h, and f then save the current parent gScoreIsBest = true; currentNode.neighbors[i].h = currentNode.neighbors[i].heuristic(this.getNode(p2)); openList.push(currentNode.neighbors[i]); } else if (gScore < currentNode.neighbors[i].g) { //current g better than previous g gScoreIsBest = true; } if (gScoreIsBest) { currentNode.neighbors[i].parent = currentNode; currentNode.neighbors[i].g = gScore; currentNode.neighbors[i].f = currentNode.neighbors[i].g + currentNode.neighbors[i].h; } } } return false; } Towers block pathability. Is there perhaps something I am missing here, or does A* not always find the shortest path in a situation such as this? Thanks in advance for any help.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• Optionally Running SPSecurity.RunWithElevatedPrivileges with Delgates

  - by Damon Armstrong

  I was writing some SharePoint code today where I needed to give people the option of running some code with elevated permission.  When you run code in an elevated fashion it normally looks like this: SPSecurity.RunWithElevatedPrivileges(()=> {     //Code to run }); It wasn’t a lot of code so I was initially inclined to do something horrible like this: public void SomeMethod(bool runElevated) {     if(runElevated)     {         SPSecurity.RunWithElevatedPrivileges(()=>         {             //Code to run         });     }     else     {         //Copy of code to run     } } Easy enough, but I did not want to draw the ire of my coworkers for employing the CTRL+C CTRL+V design pattern.  Extracting the code into a whole new method would have been overkill because it was a pretty brief piece of code.  But then I thought, hey, wait, I’m basically just running a delegate, so why not define the delegate once and run it either in an elevated context or stand alone, which resulted in this version which I think is much cleaner because the code is only defined once and it didn’t require a bunch of extra lines of code to define a method: public void SomeMethod(bool runElevated) {     var code = new SPSecurity.CodeToRunElevated(()=>     {         //Code to run     });     if(runElevated)     {         SPSecurity.RunWithElevatedPermissions(code);         }     else     {         Code();     } }

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• Spotlight on an office - Nairobi, Kenya

  - by Maria Sandu

  Hi everyone, my name is Joash Mitei. I am a graduate Intern at Oracle Systems Kenya and I will briefly take you through our offices and the working environment here in Nairobi, Kenya. I’ve been with Oracle since February 2012 and I’m responsible for Applications Pre-sales focusing on Oracle EPM and E-Business Suite. My background is Finance and Accounting therefore joining Oracle was almost a totally a different ball game but the transition has been smooth. The Oracle offices here are located on the second floor of Mebank Towers. We moved to the 2nd floor just three months ago from the 5th floor mainly because of the growing workforce. We are covering the whole Eastern Africa region hence diversity in culture is evident. This is a plus since you get to interact with people of very different backgrounds, cultures and ways of thinking. The building itself is on the outskirts of the CBD hence free from the hustle and bustle of the town. The office is split into different sections; there is a main working area which has an open desk design that fosters interaction between colleagues, there are 4 conference rooms for meetings and presentations, there are 3 quiet rooms for a little privacy when needed and there is a dining area for meals and ‘hanging out’. The working environment is world-class, to say the least. The employees are very professional, quite smart and needless to say, very busy. There are 4 interns covering sales and pre-sales in both Tech and Apps. As an intern you get support from your supervisor but you are required to show initiative yourself and thus the need to be very pro-active and inquisitive. The local management is well structured and communicative to ensure effectiveness and efficiency in the office. Apart from the daily work, we usually have events to boost staff morale such as ‘TGIF hang -out’, football matches against each other or versus other companies, and team building retreats. All these are monumental in fostering the RED POTENTIAL. We also do numerous CSR activities in the local communities . Well, that’s the Kenyan office for you. Glad to be your tour guide. Have a superb day!

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• When a co-worker asks you to teach him what you know, do you share the information or keep it to yourself? [closed]

  - by Chuck

  I am the only developer/DBA in a small IT department. There is another guy who can do it, but he's more of a backup as he spends his time working on IT support stuff. Anyway we have a new hire and I've been training him on the IT support side of things. Seems like he is eager to learn and be productive, but nobody is going out of their way to show him anything. He's been asking me to teach him database design, SQL, etc. For some reason, the boss has him working with me. He is also sending him to meetings that I go to, yet he hasn't said outright that I have to teach him anything. Meanwhile, the boss insists on doing a lot of the support work himself (i.e. he hoards information and doesn't delegate to anyone). I'm a little bit on the fence. First, the new guy doesn't yet have a strong foundation on the IT support functions which is where we really need help at this time. Second, I paid thousands of dollars for classes and spent many hours learning this stuff. Is it my responsibility to teach others skills that I had to learn on my own? Others here really aren't quick to share information so I'm not sure that I should either in this environment. I do know that if I get him involved, and get him started on projects, then I'd be responsible for his mistakes. I had to take the heat for the other guy when he made mistakes. OTOH the guy wants to learn something, is motivated, and I don't want to stop him. We've had our share of slackers in the group and it's nice to have someone who is willing to work for a change. So what would you guys do? Would you teach him the skills that you spent all of that time learning? Set him up with a test database on his PC and recommend some books for him? Encourage him to get a strong foundation in IT support first and ask later? We haven't had a new hire in years, let alone one that is interested in what I do, so this is new to me.

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• Should we persist with an employee still writing bad code after many years?

  - by user94986

  I've been assigned the task of managing developers for a well-established company. They have a single developer who specialises in all their C++ coding (since forever), but the quality of the work is abysmal. Code reviews and testing have revealed many problems, one of the worst being memory leaks. The developer has never tested his code for leaks, and I discovered that the applications could leak many MBs with only a minute of use. User's were reporting huge slowdowns, and his take was, "it's nothing to do with me - if they quit and restart, it's all good again." I've given him tools to detect and trace the leaks, and sat down with him for many hours to demonstrate how the tools are used, where the problems occur, and what to do to fix them. We're 6 months down the track, and I assigned him to write a new module. I reviewed it before it was integrated into our larger code base, and was dismayed to discover the same bad coding as before. The part that I find incomprehensible is that some of the coding is worse than amateurish. For example, he wanted a class (Foo) that could populate an object of another class (Bar). He decided that Foo would hold a reference to Bar, e.g.: class Foo { public: Foo(Bar& bar) : m_bar(bar) {} private: Bar& m_bar; }; But (for other reasons) he also needed a default constructor for Foo and, rather than question his initial design, he wrote this gem: Foo::Foo() : m_bar(*(new Bar)) {} So every time the default constructor is called, a Bar is leaked. To make matters worse, Foo allocates memory from the heap for 2 other objects, but he didn't write a destructor or copy constructor. So every allocation of Foo actually leaks 3 different objects, and you can imagine what happened when a Foo was copied. And - it only gets better - he repeated the same pattern on three other classes, so it isn't a one-off slip. The whole concept is wrong on so many levels. I would feel more understanding if this came from a total novice. But this guy has been doing this for many years and has had very focussed training and advice over the past few months. I realise he has been working without mentoring or peer reviews most of that time, but I'm beginning to feel he can't change. So my question is, would you persist with someone who is writing such obviously bad code?

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• [AJAX Numeric Updown Control] Microsoft JScript runtime error: The number of fractional digits is out of range

  - by Jenson

  If you have using Ajax control toolkits a lot (which I will skip the parts on where to download and how to configure it in Visual Studio 2010), you might have encountered some bugs or limitations of the controls, or rather, some weird behaviours. I would call them weird behaviours though. Recently, I've been working on a Ajax numeric updown control, which i remember clearly it was working fine without problems. In fact, I use 2 numeric updown control this time. So I went on to configure it to be as simple as possible and I will just use the default up and down buttons provided by it (so that I won't need to design my own). I have two textbox controls to display the value controlled by the updown control. One for month, and another for year. <asp:TextBox ID="txtMonth" runat="server" CssClass="txtNumeric" ReadOnly="True" Width="150px" /> <asp:TextBox ID="txtYear" runat="server" CssClass="txtNumeric" ReadOnly="True" Width="150px" /> So I will now drop 1 numeric updown control for each of the textboxes. <asp:NumericUpDownExtender ID="txtMonth_NumericUpDownExtender"     runat="server" TargetControlID="txtMonth" Maximum="12" Minimum="1" Width="152"> </asp:NumericUpDownExtender>                          <asp:NumericUpDownExtender ID="txtYear_NumericUpDownExtender"     runat="server" TargetControlID="txtYear" Width="152"> </asp:NumericUpDownExtender>                                                  You noticed that I configure the Maximum and Minimum value for the first numericupdown control, but I never did the same for the second one (for txtYear). That's because it won't work, well, at least for me. So I remove the Minimum="2000" and Maximum="2099" from there. Then I would configure the initial value to the the current year, and let the year to flow up and down freely. If you want, you want write the codes to restrict it. Here are the codes I used on PageLoad:     Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load         If Not Page.IsPostBack Then             If Trim(txtMonth.Text) = "" Then                 Me.txtMonth.Text = System.DateTime.Today.Month             End If             If Trim(txtYear.Text) = "" Then                 Me.txtYear.Text = System.DateTime.Today.Year             End If         End If     End Sub   Enjoy!

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• What's the best way to cache a growing database table for html generation?

  - by McLeopold

  I've got a database table which will grow in size by about 5000 rows a hour. For a key that I would be querying by, the query will grow in size by about 1 row every hour. I would like a web page to show the latest rows for a key, 50 at a time (this is configurable). I would like to try and implement memcache to keep database activity low for reads. If I run a query and create a cache result for each page of 50 results, that would work until a new entry is added. At that time, the page of latest results gets new result and the oldest results drops off. This cascades down the list of cached pages causing me to update every cache result. It seems like a poor design. I could build the cache pages backwards, then for each page requested I should get the latest 2 pages and truncate to the proper length of 50. I'm not sure if this is good or bad? Ideally, the mechanism I use to insert a new row would also know how to invalidate the proper cache results. Has someone already solved this problem in a widely acceptable way? What's the best method of doing this? EDIT: If my understanding of the MYSQL query cache is correct, it has table level granularity in invalidation. Given the fact that I have about 5000 updates before a query on a key should need to be invalidated, it seems that the database query cache would not be used. MS SQL caches execution plans and frequently accessed data pages, so it may do better in this scenario. My query is not against a single table with TOP N. One version has joins to several tables and another has sub-selects. Also, since I want to cache the html generated table, I'm wondering if a cache at the web server level would be appropriate? Is there really no benefit to any type of caching? Is the best advice really to just allow a website site query to go through all the layers and hit the database every request?

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