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• Partner Webcast – Oracle Weblogic 12c for New Projects - 07 Nov 2013

  - by Thanos Terentes Printzios

  Fast-growing organizations need to stay agile in the face of changing customer, business or market requirements. Oracle WebLogic Server 12c is the industry's best application server platform that allows you to quickly develop and deploy reliable, secure, scalable and manageable enterprise Java EE applications.WebLogic Server Java EE applications are based on standardized, modular components. WebLogic Server provides a complete set of services for those modules and handles many details of application behavior automatically, without requiring programming. New project applications are created by Java programmers, Web designers, and application assemblers. Programmers and designers create modules that implement the business and presentation logic for the application. Application assemblers assemble the modules into applications that are ready to deploy on WebLogic Server. Build and run high-performance enterprise applications and services with Oracle WebLogic Server 12c, available in three editions to meet the needs of traditional and cloud IT environments. Join us, in this webcast, as we will show you how WebLogic Server 12c helps you building and deployingenterprise Java EE applications with support for new features for lowering cost of operations, improving performance, enhancing scalability. Agenda Oracle WebLogic Server Introduction Application Development on WebLogic Using Java EE Overview of the Application Deployment Process Monitoring Application Performance Q&A November 07th, 2013 -  9am UTC/11am EET Delivery FormatThis FREE online LIVE eSeminar will be delivered over the Web. Registrations received less than 24hours prior to start time may not receive confirmation to attend. Duration: 1 hour REGISTER NOW For any questions please contact us at partner.imc-AT-beehiveonline.oracle-DOT-com Stay Connected Oracle Newsletters

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• How to collaborate on features using github

  - by Robert Dailey

  github encourages 1 fork per user, so that that user can work independently on a feature and then request that feature to be accepted into the main repository via pull request. However, what if 2 developers need to collaborate on that feature? What is the ideal workflow for this? I could see a number of options: Both developers fork the original repository. Each developer pulls/pushes changes between each other's repository. This seems like a lot of work (tiny micro operations) and also creates a delay between changes, so increases the window for conflicts. Developer 1 forks from the main repository, developer 2 forks from developer 1. Same as #1 mainly but hopefully simplifies Developer 2's life a little? Developer 1 gives Developer 2 permissions to his own fork, so they both work out of the same central repository. Not sure if this is ideal. I'm also curious where branches come into this. Obviously there would be a branch for the feature itself but that branch can't exist in a single place, it would have to exist on multiple forks and be synchronized. Basically just really confused about this workflow, would like an approach for how this can be best accomplished.

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• Any algorithm to dedicate a set of known resources to a set of known requirements (scheduling)

  - by Saeed Neamati

  I'm developing an application to help school principals in dedicating teachers to classes and courses over the hours of a week (scheduling). The scenario is roughly something like this: User enters the list of teachers and their free times into the system User enters the list of courses for this semester User enters the list of available classes into the system Well, up to here, there is no big deal. Just simple CRUD operations and nothing extraordinary. However, now what makes this system useful is that the application should automatically and based on an algorithm create the semester scheduling. I think you've got the main idea here. For example application should suggest that teacher A should go to class 1 for mathematics, and at the same time teacher B should go to class 2 for physics. This way all of the classes would be dedicated to lessons and teacher times won't overlap each other. Piece a cake for school principal. However, I can't find a good algorithm for this resource dedication. I mean it seems hard to me. Searching Google resulted in articles from different websites, but they are of no help and use to me. For example: http://en.wikipedia.org/wiki/Resource_allocation or http://en.wikipedia.org/wiki/Scheduling_(production_processes) Is there any algorithm out there, or any application or engine which can help me here? Does this requirements have a known name, like for example time scheduling engine? Any help would be appreciated.

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• How to decide if I should take a profit sharing offer or insist on hard cash

  - by Icode4food

  I am currently the sole developer at the very beginning stages of what I think could be a successful startup. My question is simply how to go about determining if I am interested in accepting a permanent stock in the enterprise or if I should insist on hard cash. This startup is seeking venture capital and it is looking likely that they will get something, I don't know how much. I know very little about the business plan or financial operations at all. The founders have experience with other startup type devours that have been successful. From a business perspective I have a reasonable amount of confidence in them. However, I have never met them face to face. They have offered me a partnership in the project but I'm fairly confident that I don't want to do that. I have done some work for them and they really like me so I'm not to afraid of loosing the position all together. I am a young developer with no experience with this sort of thing and need some experience to point me in the right direction. How to I begin to evaluate how much stock or what percentage of the profit should I ask for? Any suggestions at all would be appreciated! P.S. Any suggestions for better tags?

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• How can I mark a pixel in the stencil buffer?

  - by János Turánszki

  I never used the stencil buffer for anything until now, but I want to change this. I have an idea of how it should work: the gpu discards or keeps rasterized pixels before the pixel shader based on the stencil buffer value on the given position and some stencil operation. What I don't know is how would I mark a pixel in the stencil buffer with a specific value. For example I draw my scene and want to mark everything which is drawn with a specific material (this material could be looked up from a texture so ideally I should mark the pixel in the pixel shader), so that later when I do some post processing on my scene I would only do it on the marked pixels. I didn't find anything on the internet besides how to set up a stencil buffer and explaining the different stencil operations. I was expecting to find some System-Value semantics like SV_Depth to write to in the pixel shader (because the stencil buffer shares the same resource with the depth buffer in D3D11), but there is no such thing on MSDN. So how should I do this? If I am misunderstanding something please help me clear that up.

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• Handling Types for Real and Complex Matrices in a BLAS Wrapper

  - by mga

  I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write matrix algebra in an intuitive way (e.g. similar to MATLAB) e.g.: A = B*C*D.Inverse() + E.Transpose(); My problem is how to go about dealing with real (R) and complex (C) matrices, because of C++'s "curse" of letting you do the same thing in N different ways. I do have a clear idea of what it should look like to the user: s/he should be able to define the two separately, but operations would return a type depending on the types of the operands (R*R = R, C*C = C, R*C = C*R = C). Additionally R can be cast into C and vice versa (just by setting the imaginary parts to 0). I have considered the following options: As a real number is a special case of a complex number, inherit CMatrix from RMatrix. I quickly dismissed this as the two would have to return different types for the same getter function. Inherit RMatrix and CMatrix from Matrix. However, I can't really think of any common code that would go into Matrix (because of the different return types). Templates. Declare Matrix<T> and declare the getter function as T Get(int i, int j), and operator functions as Matrix *(Matrix RHS). Then specialize Matrix<double> and Matrix<complex>, and overload the functions. Then I couldn't really see what I would gain with templates, so why not just define RMatrix and CMatrix separately from each other, and then overload functions as necessary? Although this last option makes sense to me, there's an annoying voice inside my head saying this is not elegant, because the two are clearly related. Perhaps I'm missing an appropriate design pattern? So I guess what I'm looking for is either absolution for doing this, or advice on how to do better.

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• How much overhead is there in persistent connections?

  - by nynex

  Ok so I'm musing over a little side project I want to start. Essentially its a multi-session web based FTP client. Multi-session in that you can log into several FTP servers at the same time and perform operations like moving a file from one FTP server to another. I'm doing this mainly to brush up on the new webdev technologies, particularly websockets. I'm using node.js + socket.io to keep a persistent bi-directional connection between the web browser and the web server. The web server will also have persistent connections to each FTP server the user has logged into. So if there are 100 concurrent users each logged into 5 ftp accounts, the web server will have 100 websocket connections + 500 ftp connections. Is servicing 600 connections a lot? I know it depends on the hardware resources of the server but is something like this doable on a budget? Are there more efficient means of doing something like this? I know its unlikely that this project will really get popular but I want it to scale well regardless. Thanks for any help, I've still got a lot to learn.

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• Mercurial says "nothing changed", but it did. Sometimes my software is too clever.

  - by user12608033

  It seems I have found a "bug" in Mercurial. It takes a shortcut when checking for differences in tracked files. If the file's size and modification time are unchanged, it assumes its contents are unchanged: $ hg init . $ cp -p .sccs2hg/2005-06-05_00\:00\:00\,nicstat.c nicstat.c $ ls -ogE nicstat.c -rw-r--r-- 1 14722 2012-08-24 11:22:48.819451726 -0700 nicstat.c $ hg add nicstat.c $ hg commit -m "added nicstat.c" $ cp -p .sccs2hg/2005-07-02_00\:00\:00\,nicstat.c nicstat.c $ ls -ogE nicstat.c -rw-r--r-- 1 14722 2012-08-24 11:22:48.819451726 -0700 nicstat.c $ hg diff $ hg commit nothing changed $ touch nicstat.c $ hg diff diff -r b49cf59d431d nicstat.c --- a/nicstat.c Fri Aug 24 11:21:27 2012 -0700 +++ b/nicstat.c Fri Aug 24 11:22:50 2012 -0700 @@ -2,7 +2,7 @@ * nicstat - print network traffic, Kb/s read and written. Solaris 8+. * "netstat -i" only gives a packet count, this program gives Kbytes. * - * 05-Jun-2005, ver 0.81 (check for new versions, http://www.brendangregg.com) + * 02-Jul-2005, ver 0.90 (check for new versions, http://www.brendangregg.com) * [...] Now, before you agree or disagree with me on whether this is a bug, I will also say that I believe it is a feature. Yes, I feel it is an acceptable shortcut because in "real" situations an edit to a file will change the modification time by at least one second (the resolution that hg diff or hg commit is looking for). The benefit of the shortcut is greatly improved performance of operations like "hg diff" and "hg status", particularly where your repository contains a lot of files. Why did I have no change in modification time? Well, my source file was generated by a script that I have written to convert SCCS change history to Mercurial commits. If my script can generate two revisions of a file within a second, and the files are the same size, then I run afoul of this shortcut. Solution - I will just change my script to apply the modification time from the SCCS history to the file prior to commit. A "touch -t " will do that easily.

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• How do I throttle a command in a terminal window?

  - by To Do

  I needed to run convert with a lot of images at the same time. The command took quite a while but this doesn't bother me. The issue is that this command rendered my computer unusable while the command was running (for about 15 minutes). So is it possible to throttle the command by limiting resources (processor and memory) to the command, directly from the command line? This can only work if I add something to the same line before pressing Enter because once I start the process the computer slows so much that it is impossible for example to switch to "System monitor" and reduce priority. Edit: top and iotop results I managed to run top and sudo iotop >iotop.txt while doing one of these convert operations. (The iotop.txt file produced is difficult to read) Results of top: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 14275 username 20 0 4043m 3.0g 1448 D 7.0 80.4 0:16.45 convert Results of iotop: [?1049h[1;24r(B[m[4l[?7h[?1h=[39;49m[?25l[39;49m(B[m[H[2JTotal DISK READ: 1269.04 K/s | Total DISK WRITE:[59G0.00 B/s (B[0;7m TID PRIO USER DISK READ DISK WRITE SWAPIN(B[0;1;7m IO(B[0;7m COMMAND [3;2H(B[m2516 be/4 username 350.08 K/s 0.00 B/s 0.00 % 0.00 % zeitgeist-datahub 7394 be/4 username 568.88 K/s 0.00 B/s 77.41 % 0.00 % --rendere~.530483991[5;1H14275 idle username 350.08 K/s 0.00 B/s 37.49 % 0.00 % convert S~f test.pdf[6;2H2048 be/4 root[6;24H0.00 B/s 0.00 B/s 0.00 % 0.00 % [kworker/3:2] [5G1 be/4 root[7;24H0.00 B/s 0.00 B/s 0.00 % 0.00 % init Furthermore, even after the process ends, the computer does not return to the previous performance. I found a way around this by running sudo swapoff -a followed by sudo swapon -a

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• Are these advanced/unfair interview questions regarding Java concurrency?

  - by sparc_spread

  Here are some questions I've recently asked interviewees who say they know Java concurrency: Explain the hazard of "memory visibility" - the way the JVM can reorder certain operations on variables that are unprotected by a monitor and not declared volatile, such that one thread may not see the changes made by another thread. Usually I ask this one by showing code where this hazard is present (e.g. the NoVisibility example in Listing 3.1 from "Java Concurrency in Practice" by Goetz et al) and asking what is wrong. Explain how volatile affects not just the actual variable declared volatile, but also any changes to variables made by a thread before it changes the volatile variable. Why might you use volatile instead of synchronized? Implement a condition variable with wait() and notifyAll(). Explain why you should use notifyAll(). Explain why the condition variable should be tested with a while loop. My question is - are these appropriate or too advanced to ask someone who says they know Java concurrency? And while we're at it, do you think that someone working in Java concurrency should be expected to have an above-average knowledge of Java garbage collection?

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• Ubuntu 13.10 Unity doesn't load after upgrade

  - by William

  Just upgraded to Ubuntu 13.10 only to find that Unity won't load (login freezes, after doing ctrl+alt+F1, logging in and then doing startx, I get a blank desktop and the mouse pointer, and nothing else). I can right click, but the only operations that work are "create new file" and "create new folder". For example, "change desktop background" doesn't work. Also, after doing a few right clicks and choosing "change desktop background", I get a warning message box: "compiz closed unexpectedly." Guest login works fine. Tried creating a new user, but I experience the same thing with the new user. Tried removing all configuration files from my home directory... same thing. Doing dconf reset -f /org/compiz/ gives an error "error spawning command line..." Doing unity --reset also gives errors. Tried uninstalling unity (and compiz) and reinstalling, but that doesn't help. Tried reconfiguring lightdm, didn't help. I don't have any proprietary drivers installed. Once again, the funny thing is that the guest session works fine.

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• Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

  - by Matthew Patrick Cashatt

  Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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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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• Generic rule parser for RPG board game rules - how to do it?

  - by burzum

  I want to build a generic rule parser for pen and paper style RPG systems. A rule can involve usually 1 to N entities 1 to N roles of a dice and calculating values based on multiple attributes of an entity. For example: Player has STR 18, his currently equipped weapon gives him a bonus of +1 STR but a malus of DEX -1. He attacks a monster entity and the game logic now is required to run a set of rules or actions: Player rolls the dice, if he gets for example 8 or more (base attack value he needs to pass is one of his base attributes!) his attack is successfully. The monster then rolls the dice to calculate if the attack goes through it's armor. If yes the damage is taken if not the attack was blocked. Besides simple math rules can also have constraints like applying only to a certain class of user (warrior vs wizzard for example) or any other attribute. So this is not just limited to mathematical operations. If you're familiar with RPG systems like Dungeon and Dragons you'll know what I'm up to. My issue is now that I have no clue how to exactly build this the best possible way. I want people to be able to set up any kind of rule and later simply do an action like selecting a player and a monster and run an action (set of rules like an attack). I'm asking less for help with the database side of things but more about how to come up with a structure and a parser for it to keep my rules flexible. The language of choice for this is php by the way.

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• Debugger for file I/O development?

  - by datenwolf

  Okay, the question title may be a bit cryptic. But it aptly describes what I'm looking for: I think every experienced coder went through this numerous times: You get a binary file format specification, you implement the reader for it, and… nothing works like expected. So you run your code in the debugger, go execute through the code line by line, every header field is read in seemingly correct, but when it comes to the bulk data, offset and indices no longer match up. What would really help in this situation was a binary file viewer, that shows you the progress of your file pointer, as you step through the code, and ideally would also highlight all memory maps. Then you could see the context of the current I/O operations, most notably those darn "off-by-one" mistakes, which are even more annoying when reading a file. Implementing such a debugger should not be too hard. traces on the process' file descriptors/handles and triggers on the I/O functions, to update the display. Only: I don't know of such a kind of debugger to exist. Do I just lack knowledge about the existance of such a tool, or is there really no such thing?

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• Beginners guide to developing optimization software

  - by Florenc

  I am novice in "serious" programming i.e. applications that deal with real-life applications and software projects that go beyond school assignments. My interests include optimization, operations research, algorithms and lately i discovered how much I do like software design/development/engineering. I have already developed some simple desktop applications for some "famous" problems like TSP using heuristc approaches, a VRP solver (in progress) and so on. While developing this kind of software I actually used basic concepts taught at school such as object-orientation analysis and design. But, I found these courses rather elementary and quite boring (for my expectations). So I decided to go a little further and start developing "real" software (and this is where I realized how important and interesting software engineering/design is.) Now, here's my issue: I can not find a "study guide" for developing software of this kind. Currently, there are numerous resources out there (books, websites, tutorials) in designing and developing complex IS, web applications, smartphone apps but I can't find a book for example entitled "optimization software development". Definetly, someone could claim that "design patterns apply to software in general" but that's not my point. My point is that I could simply use my imagination for "simple" implementations, but what happens, when my imagination can not go further? In other words I'm looking for a guide/path to bridge the gap between: Mathematics-Algorithm Design-Software Engineering-Optimization-Software development

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• Name of the Countdown Numbers round problem - and algorithmic solutions?

  - by Dai

  For the non-Brits in the audience, there's a segment of a daytime game-show where contestants have a set of 6 numbers and a randomly generated target number. They have to reach the target number using any (but not necessarily all) of the 6 numbers using only arithmetic operators. All calculations must result in positive integers. An example: Youtube: Countdown - The Most Extraordinary Numbers Game Ever? A detailed description is given on Wikipedia: Countdown (Game Show) For example: The contentant selects 6 numbers - two large (possibilities include 25, 50, 75, 100) and four small (numbers 1 .. 10, each included twice in the pool). The numbers picked are 75, 50, 2, 3, 8, 7 are given with a target number of 812. One attempt is (75 + 50 - 8) * 7 - (3 * 2) = 813 (This scores 7 points for a solution within 5 of the target) An exact answer would be (50 + 8) * 7 * 2 = 812 (This would have scored 10 points exactly matching the target). Obviously this problem has existed before the advent of TV, but the Wikipedia article doesn't give it a name. I've also saw this game at a primary school I attended where the game was called "Crypto" as an inter-class competition - but searching for it now reveals nothing. I took part in it a few times and my dad wrote an Excel spreadsheet that attempted to brute-force the problem, I don't remember how it worked (only that it didn't work, what with Excel's 65535 row limit), but surely there must be an algorithmic solution for the problem. Maybe there's a solution that works the way human cognition does (e.g. in-parallel to find numbers 'close enough', then taking candidates and performing 'smaller' operations).

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• Is ZeroMQ a good choice to make a Python app and a C# managed assembly work together?

  - by Alex Bausk

  I have a task that involves talking to a .NET-based API (namely AutoCAD) to retrieve data, send commands, and react to events. I want to separate the API operations and the proper program logic (largely already implemented in Python) by using natural tools for both: a C# DLL for the former and a Python app for the latter. To connect these two pieces, I began exchanging JSON in ZeroMQ messages. I'm at early development stages but having recently discovered that ZeroMQ does not guarantee message delivery/order, I have reservations about whether this is a feasible way to go. Right now my app is a very basic REQ/REP pair and I plan to handle reacting to events and executing different commands by adding some sort of 'recipient-function' field to my message format. The reason that I want to use ZMQ is that I might be able to scale the software into a larger, multi-user, distributed solution sometime. I am a lay programmer so I would ask for your advice about this architecture. Should I just go ahead with it and plan to deal with message reliability/ordering when problems appear? Should I consider developing some kind of a REST wrapper around ZMQ?

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• Live Webcast: Discover Primavera Unifier - December 5th

  - by Melissa Centurio Lopes

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Join our live webcast to see what Primavera Unifier can do for you and your organization. We are very excited to introduce you to the newest addition to the Primavera product family, Primavera Unifier (formerly known as Skire Unifier). Attend this webcast and learn why this new cloud-based solution is the most comprehensive Enterprise Project Portfolio Management (EPPM) offering to manage the complete project lifecycle, from capital planning and construction to operations and maintenance. Save your seat: Register today for this online event and learn how the addition of Primavera Unifier can help your organization manage their projects and facilities with more predictability and financial control, improving profitability and operational efficiency

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• How to handle monetary values in PHP and MySql?

  - by Songo

  I've inherited a huge pile of legacy code written in PHP on top of a MySQL database. The thing I noticed is that the application uses doubles for storage and manipulation of data. Now I came across of numerous posts mentioning how double are not suited for monetary operations because of the rounding errors. However, I have yet to come across a complete solution to how monetary values should be handled in PHP code and stored in a MySQL database. Is there a best practice when it comes to handling money specifically in PHP? Things I'm looking for are: How should the data be stored in the database? column type? size? How should the data be handling in normal addition, subtraction. multiplication or division? When should I round the values? How much rounding is acceptable if any? Is there a difference between handling large monetary values and low ones? Note: A VERY simplified sample code of how I might encounter money values in everyday life: $a= $_POST['price_in_dollars']; //-->(ex: 25.06) will be read as a string should it be cast to double? $b= $_POST['discount_rate'];//-->(ex: 0.35) value will always be less than 1 $valueToBeStored= $a * $b; //--> any hint here is welcomed $valueFromDatabase= $row['price']; //--> price column in database could be double, decimal,...etc. $priceToPrint=$valueFromDatabase * 0.25; //again cast needed or not? I hope you use this sample code as a means to bring out more use cases and not to take it literally of course. Bonus Question If I'm to use an ORM such as Doctrine or PROPEL, how different will it be to use money in my code.

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• Anemic Domain Model, Business Logic and DataMapper (PHP)

  - by sunwukung

  I've implemented a rudimentary ORM layer based on DataMapper (I don't want to use a full blown ORM like Propel/Doctrine - for anything beyond simple fetch/save ops I prefer to access the data directly layer using a SQL abstraction layer). Following the DataMapper pattern, I've endeavoured to keep all persistence operations in the Mapper - including the location of related entities. My Entities have access to their Mapper, although I try not to call Mapper logic from the Entity interface (although this would be simple enough). The result is: // get a mapper and produce an entity $ProductMapper = $di->get('product_mapper'); $Product = $ProductMapper->find('[email protected]','email'); //.. mutaute some values.. save $ProductMapper->save($Product) // uses __get to trigger relation acquisition $Manufacturer = $Product->manufacturer; I've read some articles regarding the concept of an Anemic Domain model, i.e. a Model that does not contain any "business logic". When demonstrating the sort of business logic ideally suited to a Domain Model, however, acquiring related data items is a common example. Therefore I wanted to ask this question: Is persistence logic appropriate in Domain Model objects?

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• Data Synchronization in mobile apps - multiple devices, multiple users

  - by ProgrammerNewbie

  I'm looking into building my first mobile app. One of the core features of the application is that multiple devices/users will have access to the same data -- and all of them will have CRUD rights. I believe the architecture should involve a central server where all the data is stored. The devices will use an API to interact with the server to perform its data operations (e.g. adding a record, editing a record, deleting a record). I imagine a scenario where synchronizing the data will become a problem. Assume the application should work when it is not connected to the Internet, and thus cannot communicate with this central server. So: User A is offline and edits record #100 User B is offline and edits record #100 User C is offline and deletes record #100 User C goes online (presumably, record #100 should get deleted on the server) User A and B goes online, but the records they edited no longer exist All sorts of scenarios similar to the above can come up. How is this generally handled? I plan to use MySQL, but am wondering if it's not appropriate for such a problem.

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• String manipulation functions in SQL Server 2000 / 2005

  - by Vipin

  SQL Server provides a range of string manipulation functions. I was aware of most of those in back of the mind, but when I needed to use one, I had to dig it out either from SQL server help file or from google. So, I thought I will list some of the functions which performs some common operations in SQL server. Hope it will be helpful to you all. Len (' String_Expression' ) - returns the length of input String_Expression. Example - Select Len('Vipin') Output - 5 Left ( 'String_Expression', int_characters ) - returns int_characters characters from the left of the String_Expression.     Example - Select Left('Vipin',3), Right('Vipin',3) Output -  Vip,  Pin  LTrim ( 'String_Expression' ) - removes spaces from left of the input 'String_Expression'  RTrim ( 'String_Expression' ) - removes spaces from right of the input 'String_Expression' Note - To removes spaces from both ends of the string_expression use Ltrim and RTrim in conjunction Example - Select LTrim(' Vipin '), RTrim(' Vipin ') , LTrim ( RTrim(' Vipin ')) Output - 'Vipin ' , ' Vipin' , 'Vipin' (Single quote marks ' ' are not part of the SQL output, it's just been included to demonstrate the presence of space at the end of string.) Substring ( 'String_Expression' , int_start , int_length ) - this function returns the part of string_expression. Right ( 'String_Expression', int_characters ) - returns int_characters characters from the right of the String_Expression.

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• Why is apt-cache so slow?

  - by Damn Terminal

  After upgrade to Trusty (14.04) from Saucy (13.10), all apt operations are very slow. Even those that do not include downloading anything, or connecting to any servers. For example, displaying the apt policy # time apt-cache policy [...] real 0m8.951s user 0m5.069s sys 0m3.861s takes almost ten seconds! Mostly a weird lag right after issuing the command. And it's the same even if I issue the same command again. On another system it doesn't take a tenth of a second real 0m0.096s user 0m0.070s sys 0m0.023s The other system is a little beefier but there was no noticeable difference before the upgrade. It's the same with apt-get, anything apt-related. How do I find out the source of this lag and fix it? Additional info: # cat /etc/nsswitch.conf # /etc/nsswitch.conf # # Example configuration of GNU Name Service Switch functionality. # If you have the `glibc-doc-reference' and `info' packages installed, try: # `info libc "Name Service Switch"' for information about this file. passwd: compat group: compat shadow: compat hosts: files dns networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis BTW is my understanding of how apt-cache works correct? It doesn't make any network connections when I run apt-cache policy, right? In case I'm wrong and it matters, here are my sources https://gist.github.com/anonymous/02920270ff68e23fc3ec

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• Using visitor pattern with large object hierarchy

  - by T. Fabre

  Context I've been using with a hierarchy of objects (an expression tree) a "pseudo" visitor pattern (pseudo, as in it does not use double dispatch) : public interface MyInterface { void Accept(SomeClass operationClass); } public class MyImpl : MyInterface { public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } } This design was, however questionnable, pretty comfortable since the number of implementations of MyInterface is significant (~50 or more) and I didn't need to add extra operations. Each implementation is unique (it's a different expression or operator), and some are composites (ie, operator nodes that will contain other operator/leaf nodes). Traversal is currently performed by calling the Accept operation on the root node of the tree, which in turns calls Accept on each of its child nodes, which in turn... and so on... But the time has come where I need to add a new operation, such as pretty printing : public class MyImpl : MyInterface { // Property does not come from MyInterface public string SomeProperty { get; set; } public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } public void Accept(SomePrettyPrinter printer) { printer.PrettyPrint(this.SomeProperty); } } I basically see two options : Keep the same design, adding a new method for my operation to each derived class, at the expense of maintainibility (not an option, IMHO) Use the "true" Visitor pattern, at the expense of extensibility (not an option, as I expect to have more implementations coming along the way...), with about 50+ overloads of the Visit method, each one matching a specific implementation ? Question Would you recommand using the Visitor pattern ? Is there any other pattern that could help solve this issue ?

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