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• Which opcodes are faster at the CPU level?

  - by Geotarget

  In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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• Another good free utility - Campwood Software Source Monitor

  - by TATWORTH

  The Campwoood Source Monitor at http://www.campwoodsw.com/sourcemonitor.html  says in its introduction "The freeware program SourceMonitor lets you see inside your software source code to find out how much code you have and to identify the relative complexity of your modules. For example, you can use SourceMonitor to identify the code that is most likely to contain defects and thus warrants formal review. SourceMonitor, written in C++, runs through your code at high speed, typically at least 10,000 lines of code per second." It is indeed very high-speed and is useful as it: Collects metrics in a fast, single pass through source files. Measures metrics for source code written in C++, C, C#, VB.NET, Java, Delphi, Visual Basic (VB6) or HTML. Includes method and function level metrics for C++, C, C#, VB.NET, Java, and Delphi. Offers Modified Complexity metric option. Saves metrics in checkpoints for comparison during software development projects. Displays and prints metrics in tables and charts, including Kiviat diagrams. Operates within a standard Windows GUI or inside your scripts using XML command files. Exports metrics to XML or CSV (comma-separated-value) files for further processing with other tools.

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• PHP/MySQL Database application development tool

  - by RCH

  I am an amateur PHP coder, and have built a couple of dozen projects from scratch (including fairly simple e-commerce systems with user authentication, PayPal integration etc - all coded by hand from a clean page. Have also done a price comparison engine that takes data from multiple sites etc.). But I am no expert with OO and other such advanced techniques - I just have a fairly decent grasp of the basics of data processing, logic, functions and trying to optimize code as much as possible. I just want to make this clear so you have some idea of where I'm coming from. I have a couple of fairly large new projects on my plate for corporate clients - both require bespoke database-driven applications with complex relationships, many tables and lots of different front-end functions to manipulate that data for the internal staff in these companies. I figured building these systems from scratch would probably be a huge waste of time. Instead, there must be tools out there that will allow me to construct MySQL databases and build the pages with things like pagination, action buttons, table construction etc. Some kind of database abstraction layer, or system generator, if you will. What tool do you recommend for such a purpose for someone at my level? Open source would be great, but I don't mind paying for something decent as well. Thanks for any advice.

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• Hidden Gems: Accelerating Oracle Data Integrator with SOA, Groovy, SDK, and XML

  - by Alex Kotopoulis

  On the last day of Oracle OpenWorld, we had a final advanced session on getting the most out of Oracle Data Integrator through the use of various advanced techniques. The primary way to improve your ODI processes is to choose the optimal knowledge modules for your load and take advantage of the optimized tools of your database, such as OracleDataPump and similar mechanisms in other databases. Knowledge modules also allow you to customize tasks, allowing you to codify best practices that are consistently applied by all integration developers. ODI SDK is another very powerful means to automate and speed up your integration development process. This allows you to automate Life Cycle Management, code comparison, repetitive code generation and change of your integration projects. The SDK is easily accessible through Java or scripting languages such as Groovy and Jython. Finally, all Oracle Data Integration products provide services that can be integrated into a larger Service Oriented Architecture. This moved data integration from an isolated environment into an agile part of a larger business process environment. All Oracle data integration products can play a part in thisracle GoldenGate can integrate into business event streams by processing JMS queues or publishing new events based on database transactions. Oracle GoldenGate can integrate into business event streams by processing JMS queues or publishing new events based on database transactions. Oracle Data Integrator allows full control of its runtime sessions through web services, so that integration jobs can become part of business processes. Oracle Data Service Integrator provides a data virtualization layer over your distributed sources, allowing unified reading and updating for heterogeneous data without replicating and moving data. Oracle Enterprise Data Quality provides data quality services to cleanse and deduplicate your records through web services.

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• It could be worse....

  - by Darryl Gove

  As "guest" pointed out, in my file I/O test I didn't open the file with O_SYNC, so in fact the time was spent in OS code rather than in disk I/O. It's a straightforward change to add O_SYNC to the open() call, but it's also useful to reduce the iteration count - since the cost per write is much higher: ... #define SIZE 1024 void test_write() { starttime(); int file = open("./test.dat",O_WRONLY|O_CREAT|O_SYNC,S_IWGRP|S_IWOTH|S_IWUSR); ... Running this gave the following results: Time per iteration 0.000065606310 MB/s Time per iteration 2.709711563906 MB/s Time per iteration 0.178590114758 MB/s Yup, disk I/O is way slower than the original I/O calls. However, it's not a very fair comparison since disks get written in large blocks of data and we're deliberately sending a single byte. A fairer result would be to look at the I/O operations per second; which is about 65 - pretty much what I'd expect for this system. It's also interesting to examine at the profiles for the two cases. When the write() was trapping into the OS the profile indicated that all the time was being spent in system. When the data was being written to disk, the time got attributed to sleep. This gives us an indication how to interpret profiles from apps doing I/O. It's the sleep time that indicates disk activity.

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• Is encoding needed in this decryption?

  - by Lijo

  I have a Encryption – Decryption scenario as shown below. //[Clear text ID string as input] -- [(ASCII GetByte) + Encoding] -- [Encrption as byte array] -- [Database column is in VarBinary] -- [Pass byte[] as VarBinary parameter to SP for comparison] //[ID stored as VarBinary in Database] -- [Read as byte array] -- [(Decrypt as byte array) + Encoding + (ASCII Get String)] -- Show as string in the UI My question is in the decryption scenario. After decryption I get a byte array. I am doing an encoding (IBM037) after that. Is it correct? Is there something wrong in the flow shown above? private static byte[] GetEncryptedID(string id) { Interface_Request input = new Interface_Request(); input.RequestText = Encodeto64(id); input.RequestType = Encryption; ProgramInterface inputRequest = new ProgramInterface(); inputRequest.Test_Trial_Request = input; using (KTestService operation = new KTestService()) { return ((operation.KTrialOperation(inputRequest)).Test_Trial_Response.ResponseText); } } private static string GetDecryptedID(byte[] id) { Interface_Request input = new Interface_Request(); input.RequestText = id; input.RequestType = Decryption; ProgramInterface request = new ProgramInterface(); request.Test_Trial_Request = input; using (KTestService operationD = new KTestService()) { ProgramInterface1 response = operationD.KI014Operation(request); byte[] decryptedValue = response.ICSF_AES_Response.ResponseText; Encoding sourceByteFormat = Encoding.GetEncoding("IBM037"); Encoding destinationByteFormat = Encoding.ASCII; //Convert from one byte format to other (IBM to ASCII) byte[] ibmEncodedBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat,decryptedValue); return System.Text.ASCIIEncoding.ASCII.GetString(ibmEncodedBytes); } } private static byte[] EncodeTo64(string toEncode) { byte[] dataInBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(toEncode); Encoding destinationByteFormat = Encoding.GetEncoding("IBM037"); Encoding sourceByteFormat = Encoding.ASCII; //Convert from one byte format to other (ASCII to IBM) byte[] asciiBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat, dataInBytes); return asciiBytes; }

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• Getting the PC speaker to beep

  - by broiyan

  There has been much written on getting the beep sound from Ubuntu releases over the years. Example: fixing the beep My needs are slightly different in that I do not want to ensure sound card beeps are functioning. Instead, I want PC speaker beeps, the kind produced by the original built-in speaker because I believe they will produce less CPU load. I have confirmed that my computer has the PC speaker by unplugging the external speakers and shutting down Ubuntu. At some point in the shutdown and restart process a beep is heard even though the external speakers have no power. I have tried the following: In /etc/modprobe.d/blacklist.conf, turn these lines into comments: #blacklist snd_pcsp #blacklist pcspkr In .bashrc /usr/bin/xset b on /usr/bin/xset b 100 Enable in the gnome terminal: Edit Profile Prefs General Terminal Bell Ensure no "mute" selections in: System Prefs Sound various tabs (uncheck them all). Select "Enable window and button sounds" in: System Prefs Sound Sound Effects In gconf-editor desktop gnome sound, select the three sound check boxes. In gconf-editor apps metacity general select the audible bell check box. Still I get no PC speaker beeps when I send code 7 to the console via my Java program or use echo -e '\a' on the bash command line. What else should I try? Update Since my goal is to minimize load on the CPU, here is a comparison of elapsed times. Each test is for 100,000 iterations. Each variant was performed three times so three results are presented for each. printwriter.format("%c", 7); // 1.3 seconds, 1.5 seconds, 1.5 seconds Toolkit.getDefaultToolkit().beep(); // 0.8 seconds, 0.3 seconds, 0.5 seconds try { Runtime.getRuntime().exec("beep"); } catch (IOException e) { } // 10.3 seconds, 16.3 seconds, 11.4 seconds These runs were done inside Eclipse so multiply by some value less than 1 for standalone execution. Unfortunately, Toolkit's beep is silent on my computer and so is code 7. The beep utility works but has the most cost.

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• Raspberry Pi, Time Capsule Progress

  - by Richard Jones

  So by way of an update. I thought all was good with my Raspberry Pi, Debian and Netatalk Apple Time Capsule Clone. However something very strange going on. Although I could backup my Mac's + PC's fine to Raspberry Pi with external USB HD; strangely with RPI running, I couldn't use AirPlay. I found myself unable to play anything from Mac to Apple TV. So after lots of trying to make this work, I about turned and finally went out and got myself a 2TB Apple Time Capsule. More cash than I would want to spend on anything like this, but Apple you got me. I would like to offer a top tip, which maybe goes a small way to justifying silly expenditure... You can easily add a USB HD to any Time Capsule. I've just added a 3 TB external USB HD, giving me a 5 TB of total backup grunt. 3 TB External USB HD, was peanuts by comparison to Apple kit. So all working, its all solid as you'd expect.Apple 2, maybe me .5. But strong, solid backups now happening, without hassle (but a bit of a credit card bill to follow)

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• Why has my internet speed dropped down?

  - by Door Knob

  I recently switched to Ubuntu. I've been having a lot of internet troubles ever since. I used Windows 7 before. I've had trouble loading web pages, and it would take a solid minute or two to even start displaying anything. Why is this? How can I fix this? Details: Ubuntu 14.04 ifconfig: eth0 Link encap:Ethernet HWaddr f0:4d:a2:2c:59:42 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:21 Memory:f7ae0000-f7b00000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:785 errors:0 dropped:0 overruns:0 frame:0 TX packets:785 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:70511 (70.5 KB) TX bytes:70511 (70.5 KB) wlan0 Link encap:Ethernet HWaddr 14:da:e9:b0:9d:66 inet addr:192.168.2.12 Bcast:192.168.2.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11979 errors:0 dropped:0 overruns:0 frame:0 TX packets:10503 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:13659505 (13.6 MB) TX bytes:1449698 (1.4 MB) Here's a comparison: Speedtest on my phone: Speedtest on my PC: Taken about 30 seconds apart.

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• Don't miss Virtual Developer Day - All about ADF next week

  - by Shay Shmeltzer

  In case you haven't heard we are holding a free online virtual developer day next week - July 10th that you should attend - even if you think you already know ADF. First the registration link - http://bit.ly/fusiondev. While one of the tracks is aimed at developer who are relatively new to ADF - and cover ADF Faces, ADF Controller and a comparison of productivity with Forms and other tools - the two other tracks have great content on some topics that you might not be familiar with even if you already work with ADF. This include sessions about the upcoming ADF Mobile, The new ADF support in Eclipse and information about Application Life Cycle Management with ADF and JDeveloper. As well as sessions that will open your mind to the areas where ADF integrates with other Fusion Middleware Solutions such as ADF integration with BI, WebCenter and SOA. Most of the sessions are quite heavy on demos and you'll get a chance to interact with the presenters and ask questions during the live event. You should register even if you can't attend the live event - this way you'll get an email pointing you to the recorded sessions for on demand viewing. See you next week.

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• Transitioning from Internal to Public Speaking

  - by TJB

  For whatever reason, I've always enjoyed giving presentations. As a developer, I've grown from giving the rare presentation when asked to frequently doing 'brown bag' talks and other presentations on new technology, projects etc. I'd like to expand as a presenter and start giving talks in public, outside of just my workplace, and I'm looking for tips on how to get there. At a high level, I'd love to know a good path to take & useful tips to help me grow from just giving internal talks to my group (10-20 people) to eventually be a presenter at medium-large sized conferences. Here are some specific questions, but I will take any advice you can offer: 1. How much experience do I need to speak at user groups etc? I've been in industry for around 5 years, which pales in comparison to most speakers that I normally see. 2. What is a good venue for my 1st public talk? 3. What surprises can I expect when transistioning from speaking to a small group of friends to presenting in public to strangers? I live in southern California and my background is mostly .net / web, so if you have any specific user group / venues those are also greatly appreciated.

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• filtering dates in a data view webpart when using webservices datasource

  - by Patrick Olurotimi Ige

  I was working on a data view web part recently and i had  to filter the data based on dates.Since the data source was web services i couldn't use  the Offset which i blogged about earlier.When using web services to pull data in sharepoint designer you would have to use xpath.So for example this is the soap that populates the rows<xsl:variable name="Rows" select="/soap:Envelope/soap:Body/ddw1:GetListItemsResponse/ddw1:GetListItemsResult/ddw1:listitems/rs:data/z:row/>But you would need to add some predicate [] and filter the date nodes.So you can do something like this (marked in red)<xsl:variable name="Rows" select="/soap:Envelope/soap:Body/ddw1:GetListItemsResponse/ddw1:GetListItemsResult/ddw1:listitems/rs:data/z:row[ddwrt:FormatDateTime(string(@ows_Created),1033,'yyyyMMdd') &gt;= ddwrt:FormatDateTime(string(substring-after($fd,'#')),1033,'yyyyMMdd')]"/>For the filtering to work you need to have the date formatted  above as yyyyMMdd.One more thing you must have noticed is the $fd variable.This variable is created by me creating a calculated column in the list so something like this [Created]-2So basically that the xpath is doing is get me data only when the Created date  is greater than or equal to the Created date -2 which is 2 date less than the created date.Also not that when using web services in sharepoint designer and try to use the default filtering you won't get to see greater tha or less than in the option list comparison.:(Hope this helps.

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• Virtualbox install 12.04 guest: "pae not present"

  - by Peter.O

  I get this message while trying to install Ubuntu 12.04 as a guest in VirutalBox 4.1.18, on an Ubuntu 10.04 host. This kernel requires the following feature not present on the CPU: pae Some host specs: The host's kernel is: Linux 2.6.32-41-generic-pae GNU/Linux lscpu (host): Architecture: i686, CPU op-mode(s): 32-bit, 64-bit grep --color=always -i PAE /proc/cpuinfo   does show pae in its output. The 12.04 iso used is: ubuntu-12.04.0-desktop-i386.iso As a comparison/check, I downloaded and installed Linux Mint 13 Cinnamon to the same host on the exact same VM (I just changed the .iso image). It worked fine. Its iso is: linuxmint-13-cinnamon-dvd-32bit.iso It seems (to me) that I have pae.. what is going on here? Update: I had assumed that Linux Mint also required pae (being Ubuntu based), but I've just run;   grep --color=always -i PAE /proc/cpuinfo   in the Mint VM.   It showed no output.   So it seems the issue may lie with VirtualBox.   If that is the case, how can I get Virtualbox into pae mode?

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• Relationship between SOA and OOA

  - by TheSilverBullet

  Thomas Erl defines SOA as follows in his site: Service-oriented computing represents a new generation distributed computing platform. As such, it encompasses many things, including its own design paradigm and design principles, design pattern catalogs, pattern languages, a distinct architectural model, and related concepts, technologies, and frameworks. This definitely sounds like a whole new category which is parallel to object orientation. Almost one in which you would expect an entirely new language to exist for. Like procedural C and object oriented C#. Here is my understanding: In real life, we don't have entirely new language for SOA. And most application which have SOA architecture have an object oriented design underneath it. SOA is a "strategy" to make the entire application/service distributed and reliable. SOA needs OOPS working underneath it. Is this correct? Where does SOA (if at all it does) fit in with object oriented programming practices? Edit: I have learnt through answers that OOA and SOA work with each other and cannot be compared (in a "which is better" way). I have changed the title to "Relationship between SOA and OOA" rather than "comparison".

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• eSTEP Newsletter November 2011 now available

  - by uwes

  Dear Partners,We would like to inform you that the November issue of our Newsletter is now available.The issue contains informations to the following topics:Notes from Corporate: Magic Quadrant for Enterprise Application Servers, Oracle Buys RightNow Technical Corner: Oracle Solaris 11 – The First Cloud OS, Oracle Solaris 10 8/11 now available, New RAC/Containers certifications, DTrace and Container for Oracle Linux, Oracle Enterprise Manager Ops Center released, News from the Oracle Solaris Cluster, SPARC - New roadmap, T-Series Benchmarks Learning & Events: eSTEP Events Schedule, Recently Delivered TechCasts, Delivered Campaigns in 2011 How to ...: About Oracle Solaris Containers, Detailed feature comparison between the different versions of database 11g, Upgrade Advantage Program + table with examples, Sun Software Name ===> New Oracle Name, Oracle Linux and OVM Certification Search, TO YOUR ATTENTION - Repricing Servers and Xoptions You find the Newsletter on our portal under eSTEP News ---> Latest Newsletter. You will need to provide your email address and the pin below to get access. Link to the portal is shown below.URL: http://launch.oracle.com/PIN: eSTEP_2011Previous published Newsletters can be found under the Archived Newsletters section and more useful information under the Events, Download and Links tab. Feel free to explore and any feedback is appreciated to help us improve the service and information we deliver.Thanks and best regards,Partner HW Enablement EMEA

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• GUI based backup utility [closed]

  - by Chethan S.

  Possible Duplicate: Comparison of backup tools I have read favorable reviews for 'Back In Time' for the purpose stated above. Still I am posting this question as I have some demands in my mind. Few years back I was using ThinkVantage Rescue and Recovery by IBM on my Lenovo PC under Windows. That provided me nice features like compressed backups, boot time options - OS Repair, Restore entire OS, restore entire system to an older date, restore individual files etc. Out of these the feature I liked the most was compressed backups. Similar features are available in software like Norton Ghost too. In Back In Time I was surprised to see that the snapshot takes up same amount of space as that of the original contents, no compression at all. Furthermore, I was not able to find options to change the compression ratio etc. under settings. According to me compression of backups is a must have feature. Therefore, can anyone suggest me any other utility which can serve the purpose. I insist on GUI based tool since I don't want to mess up with backups!

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• What is a 'good number' of exceptions to implement for my library?

  - by Fuzz

  I've always wondered how many different exception classes I should implement and throw for various pieces of my software. My particular development is usually C++/C#/Java related, but I believe this is a question for all languages. I want to understand what is a good number of different exceptions to throw, and what the developer community expect of a good library. The trade-offs I see include: More exception classes can allow very fine grain levels of error handling for API users (prone to user configuration or data errors, or files not being found) More exception classes allows error specific information to be embedded in the exception, rather than just a string message or error code More exception classes can mean more code maintenance More exception classes can mean the API is less approachable to users The scenarios I wish to understand exception usage in include: During 'configuration' stage, which might include loading files or setting parameters During an 'operation' type phase where the library might be running tasks and doing some work, perhaps in another thread Other patterns of error reporting without using exceptions, or less exceptions (as a comparison) might include: Less exceptions, but embedding an error code that can be used as a lookup Returning error codes and flags directly from functions (sometimes not possible from threads) Implemented an event or callback system upon error (avoids stack unwinding) As developers, what do you prefer to see? If there are MANY exceptions, do you bother error handling them separately anyway? Do you have a preference for error handling types depending on the stage of operation?

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• Cuda driver, CPU/GPU performances issue

  - by elect

  I implemented a RNS Montgomery exponentiation in Cuda and on cpu for comparison. Everything nice everything fine. It runs on just one SM. However I am going to tell you some strange regression in both cpu/gpu performances. During the devoloping, about two month ago, I was using Cuda 5 preview on Ubuntu 11.04 64b. In this time, I reach the following performances: cpu 460ms gpu 120ms Then one day when I turn on the pc, the graphical environment didnt start. I dont know which was the problem, however I switched to the console and installed again the Cuda driver. At the following boot performances changed: cpu 310ms gpu 80ms I was like Q.Q...uhm ok, nice to see this, but I was wondering how that could be possible However, I went then in holiday for 10 days and I continued developing and optimizing on my notebook (but not the same part of the code, some additional stuff) When I was back, I just updated the source files, and performances came back to 460/120ms.. I couldnt believe it, I tried to install Cuda 5 RC, updating the video driver too... nothing changed... I checked Debug/Release, Cuda computability, but the problem seems being somewhere else.. Looking around the net I found this, I am pretty sure it must have something to do with the driver, because the performance change affected both cpu and gpu Do you have some tips/ideas/suggestions?

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• Is there any kind of established architecture for browser based MMO games?

  - by black_puppydog

  I am beginning the development of a broser based game in which players take certain actions at any point in time. Big parts of gameplay will be happening in real life and just have to be entered into the system. I believe a good kind of comparison might be a platform for managing fantasy football, although I have virtually no experience playing that, so please correct me if I am mistaken here. The point is that some events happen in the program (i.e. on the server, out of reach for the players) like pulling new results from some datasource, starting of a new round by a game master and such. Other events happen in real life (two players closing a deal on the transfer of some team member or whatnot - again: have never played fantasy football) and have to be entered into the system. The first part is pretty easy since the game masters will be "staff" and thus can be trusted to a certain degree to not mess with the system. But the second part bothers me quite a lot, especially since the actions may involve multiple steps and interactions with different players, like registering a deal with the system that then has to be approved by the other party or denied and passed on to a game master to decide. I would of course like to separate the game logic as far as possible from the presentation and basic form validation but am unsure how to do this in a clean fashion. Of course I could (and will) put some effort into making my own architectural decisions and prototype different ideas. But I am bound to make some stupid mistakes at some point, so I would like to avoid some of that by getting a little "book smart" beforehand. So the question is: Is there any kind of architectural works that I can read up on? Papers, blogs, maybe design documents or even source code? Writing this down this seems more like a business application with business rules, workflows and such... Any good entry points for that?

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• Nullable types and ?? operator C# [en-US]

  - by ruimachado

  Nullable types vs Non-nullable types   While developing our C# projects its frequent the null comparison operation to avoid null exceptions. This simple operation is mainly coded using the "var x = null" code example inside an if clause. However not all types of variables are nullable, which means that setting a variable to null is not allowed in every cases, it depends on what kind of type are you defining. But what if there was an extension to your non-nullable type that would convert your variable types to nullable? This extension really exists. As I said before in C# you have nullable types which represent all the values of an underlying type, and an additional null value and can be declared easily using "T?", where T is the type of the variable and for example the normal int type cannot be null, so its a non-nullable type, however if you define a "int?" your variable can be null, what you do is convert a non-nullable type to a nullable type. Example: int x=null;     Not allowed     int? x=null;   Allowed     While using nullable types you can check if a variable is null the same way you do it with nullable types:     But what about setting a default value when a certain variable is null?   In this cases the c# .net framework let you set a default value when you try to assign a nullable type to a non-nullable type, using the ?? operator. If you don't use this operator you can still catch the InvalidOperationException which is throw in this cases. For example  without the ?? operator :     Using the ?? operator your code becomes cleaner and more easy to read and you get a bonus, you can set a default value for multiple variables using the ?? in a chain set.     That’s it,   Thanks, Rui Machado rpmachado.wordpress.com

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• Clustering Strings on the basis of Common Substrings

  - by pk188

  I have around 10000+ strings and have to identify and group all the strings which looks similar(I base the similarity on the number of common words between any two give strings). The more number of common words, more similar the strings would be. For instance: How to make another layer from an existing layer Unable to edit data on the network drive Existing layers in the desktop Assistance with network drive In this case, the strings 1 and 3 are similar with common words Existing, Layer and 2 and 4 are similar with common words Network Drive(eliminating stop word) The steps I'm following are: Iterate through the data set Do a row by row comparison Find the common words between the strings Form a cluster where number of common words is greater than or equal to 2(eliminating stop words) If number of common words<2, put the string in a new cluster. Assign the rows either to the existing clusters or form a new one depending upon the common words Continue until all the strings are processed I am implementing the project in C#, and have got till step 3. However, I'm not sure how to proceed with the clustering. I have researched a lot about string clustering but could not find any solution that fits my problem. Your inputs would be highly appreciated.

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• What are solutions and tradeoffs to maintain search result consistency in a web application

  - by iammichael

  Consider a web application with a custom search function that must display the results in a paged manner (twenty per page with up to hundreds of thousands of total results) and the ability to drill down to individual results that maintain next/previous links to navigate through the results. Re-executing the search on each page request to get the appropriate results for that page of data can be too expensive (up to 15s per search). Also, since the underlying data can change frequently (e.g. addition of new results), re-executing could cause the next/previous functionality to result in inconsistent behavior (e.g. the same results reappearing on a later page after having been viewed on an earlier page). What options exist to ensure the search results can be viewed across multiple pages in a consistent manner, and what tradeoffs does each option have in terms of network, CPU, memory, and storage requirements? EDIT: I thought caching the query search results was an obvious necessity. The question is really asking about where to cache the result set and what tradeoffs might exist to each. For example, storing the ids of the entities in the result set on the client, or storing the IDs of the entities themselves in the users session on the web server, or in a temporary table in the database. I'm not looking specifically for a single solution as different scenarios may result in different approaches (and such a question would be more suited for stackoverflow.com rather than here), but more of a design comparison between the possible approaches.

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

  - by billpg

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

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• Why does there seem to be a lot of fear in choosing the "wrong" language to learn?

  - by Shewbox

  Perhaps its just me, but as a current CS student I have already come across many questions on this site and elsewhere about not just "Which language should I use for x?" but also "Does anyone still use language Y?" My first CS class was taught in Scheme, which, if I'm not mistaken, isn't used widely (at least in comparison to languages like Java, PHP, Python, etc). Many of my classmates balked at the idea of having to learn a language they would never have to use again, but I don't quite understand where so much of this fear of learning less popular languages comes from. No, I may not use Scheme in any job I get, but I certainly don't regret having learned to use it (albeit in a very beginner, not very in-depth manner in that one semester). I am taking a search engines class this semester, which is done in Perl and again I am seeing classmates complaining about the language choice. I can understand having a favorite language and disliking others but why do some get worked up over learning it in the first place? Can you really learn the "wrong" language? Isn't learning something like Scheme or Haskell good mental exercise if nothing else, and useful at least to exposure to different ways of solving problems?

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• Booting off a ZFS root in 14.04

  - by RJVB

  I've been running a Debian derivative (LMDE) on a ZFS root for half a year now. It was created by cloning a regular ext4-based install with all the necessary packages onto a ZFS pool, chrooting into that pool and recreating a grub menu and bootloader. The system uses an ext-3 dedicated /boot partition. I would like to do the same with Ubuntu 14.04, but have encountered several obstacles. There is no Trusty zfs-grub package The default grub package doesn't have ZFS support built in. I found a small bug in the build system responsible for that (report with patch created) and built my own grub packages. The built-in ZFS support is dysfunctional, it does not add the proper arguments to the kernel command line I thus installed the ZoL grub package I also use on my LMDE system, which does give me a correct grub.cfg However, even with that correct grub.cfg, the boot process apparently doesn't retrieve the bootfs parameter from the ZFS pool; instead the variable that's supposed to receive the value remains empty. As a result, initrd tries to load the default pool ("rpool"), which fails of course. I can however import the pool by hand, and complete the process by hand. If memory serves me well, I also had to disable apparmor, to avoid the boot process from blocking after importing the pool. Am I overlooking something? Just for comparison, I installed the Ubuntu 3.13 kernel on my LMDE system, and that works just fine (i.e. the identical kernel and grub binaries allow successful booting without glitches on LMDE but not on Ubuntu).

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