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Search found 168 results on 7 pages for 'computational linguistics'.

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• SPUtility.SendMail and the 2048 Character Limit

  - by Damon

  We were in the middle of testing a web part responsible for gathering information from visitors to our Client's website and emailing it to someone responsible for responding to the request.  During testing, however, it was brought to our attention that the message was cutting off at 2048 characters.  Now, 2048 is one of those numbers that is usually indicative of some computational limit, but I was hopeful that Microsoft had thought through the possibility of emailing more than 2048 characters from SharePoint.  Luckily I was right. and wrong. As it turns out, SPUtility.SendMail is not limited to any specific character limit as far as I can tell.  However, each LINE of text that you send via SendMail cannot exceed 2048 characters.  Since we were sending an HTML email it was constructed entirely without line breaks, far exceeding the 2048 character limit and ultimately helping to educate me about this obscure technical limitation whose only benefit thus far is offering me something to rant about on my blog.  The fix is simple, just put in a carriage return and a line break often enough to avoid going past the 2048 character limit.  I'm sure someone can present a great technical reason for the 2048 character limit, but it seems fairly arbitrary since the "\r\n" that got appended to the string are ultimately just characters too.

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• What types of programming contest problems are there?

  - by Alex

  Basically, I want to make a great reference for use with programming contests that would have all of the algorithms that I can put together that I would need during a contest as well as sample useage for the code. I'm planning on making this into a sort of book that I could print off and take with me to competitions. I would like to do this rather than simply bringing other books (such as Algorithms books) because I think that I will learn a lot more by going over all of the algorithms myself as well as I would know exactly what I have in the book, making it more efficient to have and use. So, I've been doing research to determine what types of programming problems and algorithms are common on contests, and the only thing I can really find is this (which I have seen referenced a few times): Hal Burch conducted an analysis over spring break of 1999 and made an amazing discovery: there are only 16 types of programming contest problems! Furthermore, the top several comprise almost 80% of the problems seen at the IOI. Here they are: Dynamic Programming Greedy Complete Search Flood Fill Shortest Path Recursive Search Techniques Minimum Spanning Tree Knapsack Computational Geometry Network Flow Eulerian Path Two-Dimensional Convex Hull BigNums Heuristic Search Approximate Search Ad Hoc Problems The most challenging problems are Combination Problems which involve a loop (combinations, subsets, etc.) around one of the above algorithms - or even a loop of one algorithm with another inside it. These seem extraordinarily tricky to get right, even though conceptually they are ``obvious''. Now that's good and all, but that study was conducted in 1999, which was 13 years ago! One thing I know is that there are no BigNums problems any more (as Java has a BigInteger class, they have stopped making those problems). So, I'm wondering if anyone knows of any more recent studies of the types of problems that may be seen in a programming contest? Or what the most helpful algorithms on contests would be?

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• Does F# kill C++?

  - by MarkPearl

  Okay, so the title may be a little misleading… but I am currently travelling and so have had very little time and access to resources to do much fsharping – this has meant that I am right now missing my favourite new language. I was interested to see this post on Stack Overflow this evening concerning the performance of the F# language. The person posing the question asked 8 key points about the F# language, namely… How well does it do floating-point? Does it allow vector instructions How friendly is it towards optimizing compilers? How big a memory foot print does it have? Does it allow fine-grained control over memory locality? Does it have capacity for distributed memory processors, for example Cray? What features does it have that may be of interest to computational science where heavy number processing is involved? Are there actual scientific computing implementations that use it? Now, I don’t have much time to look into a decent response and to be honest I don’t know half of the answers to what he is asking, but it was interesting to see what was put up as an answer so far and would be interesting to get other peoples feedback on these questions if they know of anything other than what has been covered in the answer section already.

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• HLSL How to flip geometry horizontally

  - by cubrman

  I want to flip my asymmetric 3d model horizontally in the vertex shader alongside an arbitrary plane parallel to the YZ plane. This should switch everything for the model from the left hand side to the right hand side (like flipping it in Photoshop). Doing it in pixel shader would be a huge computational cost (extra RT, more fullscreen samples...), so it must be done in the vertex shader. Once more: this is NOT reflection, i need to flip THE WHOLE MODEL. I thought I could simply do the following: Turn off culling. Run the following code in the vertex shader: input.Position = mul(input.Position, World); // World[3][0] holds x value of the model's pivot in the World. if (input.Position.x <= World[3][0]) input.Position.x += World[3][0] - input.Position.x; else input.Position.x -= input.Position.x - World[3][0]; ... The model is never drawn. Where am I wrong? I presume that messes up the index buffer. Can something be done about it? P.S. it's INSANELY HARD to format code here. Thanks to Panda I found my problem. SOLUTION: // Do thins before anything else in the vertex shader. Position.x *= -1; // To invert alongside the object's YZ plane.

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• Writing Web "server less" applications

  - by crodjer

  TL;DR What are the prospects of write applications which are completely based on a REST database server (CouchDB) and web applications which directly access the DB instead of having a web server in between? I recently started looking up some NoSQL databases. MongoDB seems to be a popular choices. I also liked the project. But I personally liked the REST interface of CouchDB. So what I wanted to know is if there was the possibility of applications (maybe cached apps in web browser, a chrome extension etc.) which could just just query the database directly with no requirement of a webserver in between. All the computational logic would reside in the client application and the database will do what it does, CRUD. Since mostly (I don't know which doesn't) client frameworks support REST quaries, it could be a good way writing applications well optimized for respective framework. These applications though won't be doing complicated computation, but still provide enough functionality which could replace lots of conventional applications. Are existing resources and projects which would help me move towards writing such applications and also the scope and moving towards developing in this way? Are their any technical/security issues with this? This post will help me decide to look into project like CouchDB (and maybe Dive into Erlang later) or stay with the conventional frameworks (like django) and SQL databases. Update A specific point of such apps I had in mind is creation of offline applications just by replicating couchdb data on client.

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• Apache DVB http video Streaming bandwidth or priority problem

  - by igino manfre'

  I'm streaming few precompressed DVB videos from cloud. The streams are generated from VLC on "impossible" ports (such as 64085, 64086 etc) reverse proxed by Apache on port 80 and 8080. All the generated streams are listed in "http://95.110.164.61/indexv.html". From an ADSL connection with enough downlink bandwidth, recalling the stream generated by VLC (such as "http://95.110.164.61:64087/mpg2_6.4") it flows fluently. Recalling the same stream proxed by Apache ("http://95.110.164.61/mpg2_6.4") the stream stops and goes. The only situation in which the Apache proxed streams flow regularly is from a site connected through 64 Mbps warranted bandwith with RTT to the server less than 10 mseconds. Please note that streams below 2 Mbps are fluently proxed. The system is a single core xeon with windows 2008 R2 on 4 GB of RAM with 1 Gbps of network bandwidth. The drain of computational and bandwidth resources is negligeable, the RAM usage always lower than 50%. On the system I run many VLC streamers. Any of them drains a variable amount of RAM (from about 25 to 70 MB). On the contrary the couple of httpd.exe processes drain no more than 7 MB. Using Wireshark (on the server) I see that VLC directy send to the client much more packets than Apache, and the stream is framgmented on many frames. I'm not a programmer, a newby of Apache. Can anyone please address me to a specific portion of the Apache's huge documentation? Thank you. igino

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• Modular Web App Network Architecture

  - by nairware

  Assuming that I am dealing with dedicated physical servers or VPSs, is it conceivable and does it make sense to have distinct servers setup with the following roles to host a web application? Reverse Proxy Web server Application server Database server Specific points of interest: I am confused how to even separate the web and application servers. My understanding was that such 3-tier architectures were feasible. It is unclear to me if the app server would reside directly between the web and database server, or if the web server could directly interact with the database as well. The app server could either do the computational heavy-lifting on behalf of the app server or it could do heavy-lifting plus control all of the business logic (as implied in the diagram above, thus denying the web server of direct database access). I am also unsure what role the reverse proxy (ex. nginx) could and should fulfill as a web server, given the above mentioned setup. I know that nginx has web server features. But I do not know if it makes sense to have the reverse proxy be its own VPS, given that the web server–in theory–would be separate from the app server.

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• Will I be able to get programming interviews at good software companies with a non-CS degree?

  - by friend

  I'll be graduating in a year, but I'll have a degree in Economics. I'm pretty much done with my Economics coursework, and by the time next year comes around I will have devoted 1.5 years to learning CS. I will have almost finished the requirements to graduate with a degree in CS, but unfortunately my school requires a science series that would add another 6-9 months of study if I were to try and get the degree (not to mention a max unit cap). I have or will have taken: Objected Oriented Programming Discrete Math Data structures Calculus through multivariable (doubt this matters at all) Linear Algebra (same) Computer Organization Operating Systems Computational Statistics (many data mining projects in R) Parallel Programming Programming Languages Databases Algorithms Compilers Artificial Intelligence I've done well in the ones I've taken, and I hope to do well in the rest, but will that matter if I can't say to the HR people that I have a CS degree? I'd be happy to get an internship at first too, so should I just apply as if I'm an intern and not looking for fulltime, and then try and parlay that into something? Sidenote if you have time -- Is a computer networks or theory of computation class important? Would it be worth taking either of those in lieu of a class on my list? edit -- I know this isn't AskReddit or College Confidential; I know there will be some outrage at posting a question like this. I'm merely looking for insight into a situation that I've been struggling with, and I think this is the absolute best place to find an answer to this question. Thanks.

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• High-level strategy for distinguishing a regular string from invalid JSON (ie. JSON-like string detection)

  - by Jonline

  Disclaimer On Absence of Code: I have no code to post because I haven't started writing; was looking for more theoretical guidance as I doubt I'll have trouble coding it but am pretty befuddled on what approach(es) would yield best results. I'm not seeking any code, either, though; just direction. Dilemma I'm toying with adding a "magic method"-style feature to a UI I'm building for a client, and it would require intelligently detecting whether or not a string was meant to be JSON as against a simple string. I had considered these general ideas: Look for a sort of arbitrarily-determined acceptable ratio of the frequency of JSON-like syntax (ie. regex to find strings separated by colons; look for colons between curly-braces, etc.) to the number of quote-encapsulated strings + nulls, bools and ints/floats. But the smaller the data set, the more fickle this would get look for key identifiers like opening and closing curly braces... not sure if there even are more easy identifiers, and this doesn't appeal anyway because it's so prescriptive about the kinds of mistakes it could find try incrementally parsing chunks, as those between curly braces, and seeing what proportion of these fractional statements turn out to be valid JSON; this seems like it would suffer less than (1) from smaller datasets, but would probably be much more processing-intensive, and very susceptible to a missing or inverted brace Just curious if the computational folks or algorithm pros out there had any approaches in mind that my semantics-oriented brain might have missed. PS: It occurs to me that natural language processing, about which I am totally ignorant, might be a cool approach; but, if NLP is a good strategy here, it sort of doesn't matter because I have zero experience with it and don't have time to learn & then implement/ this feature isn't worth it to the client.

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• CodePlex Daily Summary for Thursday, December 02, 2010

  CodePlex Daily Summary for Thursday, December 02, 2010Popular ReleasesChronos WPF: Chronos v2.0 Beta 3: Release notes: Updated introduction document. Updated Visual Studio 2010 Extension (vsix) package. Added horizontal scrolling to the main window TaskBar. Added new styles for ListView, ListViewItem, GridViewColumnHeader, ... Added a new WindowViewModel class (allowing to fetch data). Added a new Navigate method (with several overloads) to the NavigationViewModel class (protected). Reimplemented Task usage for the WorkspaceViewModel.OnDelete method. Removed the reflection effect...MDownloader: MDownloader-0.15.26.7024: Fixed updater; Fixed MegauploadDJ - jQuery WebControls for ASP.NET: DJ 1.2: What is new? Update to support jQuery 1.4.2 Update to support jQuery ui 1.8.6 Update to Visual Studio 2010 New WebControls with samples added Autocomplete WebControl Button WebControl ToggleButt WebControl The example web site is including in source code project.LateBindingApi.Excel: LateBindingApi.Excel Release 0.7g: Unterschiede zur Vorgängerversion: - Zusätzliche Interior Properties - Group / Ungroup Methoden für Range - Bugfix COM Reference Handling für Application Objekt in einigen Klassen Release+Samples V0.7g: - Enthält Laufzeit DLL und Beispielprojekte Beispielprojekte: COMAddinExample - Demonstriert ein versionslos angebundenes COMAddin Example01 - Background Colors und Borders für Cells Example02 - Font Attributes undAlignment für Cells Example03 - Numberformats Example04 - Shapes, WordArts, P...ESRI ArcGIS Silverlight Toolkit: November 2010 - v2.1: ESRI ArcGIS Silverlight Toolkit v2.1 Added Windows Phone 7 build. New controls added: InfoWindow ChildPage (Windows Phone 7 only) See what's new here full details for : http://help.arcgis.com/en/webapi/silverlight/help/#/What_s_new_in_2_1/016600000025000000/ Note: Requires Visual Studio 2010, .NET 4.0 and Silverlight 4.0.ASP .NET MVC CMS (Content Management System): Atomic CMS 2.1.1: Atomic CMS 2.1.1 release notes Atomic CMS installation guide Winware: Winware 3.0 (.Net 4.0): Winware 3.0 is base on .Net 4.0 with C#. Please open it with Visual Studio 2010. This release contains a lab web application.EnhSim: EnhSim 2.1.1: 2.1.1This release adds in the changes for 4.03a. To use this release, you must have the Microsoft Visual C++ 2010 Redistributable Package installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=A7B7A05E-6DE6-4D3A-A423-37BF0912DB84 To use the GUI you must have the .NET 4.0 Framework installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=9cfb2d51-5ff4-4491-b0e5-b386f32c0992 - Switched Searing Flames bac...AI: Initial 0.0.1: It’s simply just one code file; it simulates AI and machine in a simulated world. The AI has a little understanding of its body machine and parts, and able to use its feet to do actions just start and stop walking. The world is all of white with nothing but just the machine on a white planet. Colors, odors and position information make no sense. I’m previous C# programmer and I’m learning F# during this project, although I’m still not a good F# programmer, in this project I learning to prog...NKinect: NKinect Preview: Build features: Accelerometer reading Motor serial number property Realtime image update Realtime depth calculation Export to PLY (On demand) Control motor LED Control Kinect tiltMicrosoft - Domain Oriented N-Layered .NET 4.0 App Sample (Microsoft Spain): V1.0 - N-Layer DDD Sample App .NET 4.0: Required Software (Microsoft Base Software needed for Development environment) Visual Studio 2010 RTM & .NET 4.0 RTM (Final Versions) Expression Blend 4 SQL Server 2008 R2 Express/Standard/Enterprise Unity Application Block 2.0 - Published May 5th 2010 http://www.microsoft.com/downloads/en/details.aspx?FamilyID=2D24F179-E0A6-49D7-89C4-5B67D939F91B&displaylang=en http://unity.codeplex.com/releases/view/31277 PEX & MOLES 0.94.51023.0, 29/Oct/2010 - Visual Studio 2010 Power Tools http://re...Sense/Net Enterprise Portal & ECMS: SenseNet 6.0.1 Community Edition: Sense/Net 6.0.1 Community Edition This half year we have been working quite fiercely to bring you the long-awaited release of Sense/Net 6.0. Download this Community Edition to see what we have been up to. These months we have worked on getting the WebCMS capabilities of Sense/Net 6.0 up to par. New features include: New, powerful page and portlet editing experience. HTML and CSS cleanup, new, powerful site skinning system. Upgraded, lightning-fast indexing and query via Lucene. Limita...Minecraft GPS: Minecraft GPS 1.1.1: New Features Compass! New style. Set opacity on main window to allow overlay of Minecraft. Open World in any folder. Fixes Fixed style so listbox won't grow the window size. Fixed open file dialog issue on non-vista kernel machines.DotSpatial: DotSpatial 11-28-2001: This release introduces some exciting improvements. Support for big raster, both in display and changing the scheme. Faster raster scheme creation for all rasters. Caching of the "sample" values so once obtained the raster symbolizer dialog loads faster. Reprojection supported for raster and image classes. Affine transform fully supported for images and rasters, so skewed images are now possible. Projection uses better checks when loading unprojected layers. GDAL raster support f...Virtu: Virtu 0.9.0: Source Requirements.NET Framework 4 Visual Studio 2010 or Visual Studio 2010 Express Silverlight 4 Tools for Visual Studio 2010 Windows Phone 7 Developer Tools (which includes XNA Game Studio 4) Binaries RequirementsSilverlight 4 .NET Framework 4 XNA Framework 4Cropper: 1.9.4: Mostly fixes for issues with a few feature requests. Fixed Issues 2730 & 3638 & 14467 11044 11447 11448 11449 14665 Implemented Features 6123 11581PFC: PFC for PB 11.5: This is just a migration from the 11.0 code. No changes have been made yet (and they are needed) for it to work properly with 11.5.PDF Rider: PDF Rider 0.5: This release does not add any new feature for pdf manipulation, but enables automatic updates checking, so it is reccomended to install it in order to stay updated with next releases. Prerequisites * Microsoft Windows Operating Systems (XP - Vista - 7) * Microsoft .NET Framework 3.5 runtime * A PDF rendering software (i.e. Adobe Reader) that can be opened inside Internet Explorer. Installation instructionsChoose one of the following methods: 1. Download and run the "pdfRider0...BCLExtensions: BCL Extensions v1.0: The files associated with v1.0 of the BCL Extensions library.Microsoft All-In-One Code Framework: Visual Studio 2010 Code Samples 2010-11-25: Code samples for Visual Studio 2010New Projects<geomap/> - Mapping UI Extensions to HTML / XHTML: A extension to HTML that adds support for declaratively adding maps to web applications. Initially there will only be support for Bing Maps, but a plugin API will be available to add other providers.ActiveRecord Provider: AR Provider is a .NET Membership provider implemented in C#, using Castle ActiveRecord for data persistence.AS PhoneBook: PhoneBook is very simple program which helps you to easily save your contacts names, numbers and e-mails. Designed look, easy dashboard, simple codes developed in c#, perfect perfomance...BAFactory Framework: A multipurpose frameworkBaqUP: Log syncronization system.C++ Bitmap Library: The C++ Bitmap Library consists of simple, robust, optimized and portable 24-bit bitmap image processing algorithms for the C++ language. Drag & Drop for SharePoint: Organize your SharePoint document libraries by moving documents using jQuery Multi-Select Drag&Drop (MSDD) functionality. Estoque: Estoque is a Todo-App that comes with TFS integration an sync.FBA Configuration Manager for SharePoint 2010: Setting up Forms Based Authentication in SharePoint 2010 requires updating the web.config file of three web applications. This utility allows you to update all 3 configs in a single click. The updater can also be invoked from PowerShell.Hackathon - DotNetNuke Razor Contact List: This is a simple set of Razor scripts for displaying a contact list in DotNetNuke using profile data.Joselyn Web Toolkit: A JS LibraryKind Of Magic MSBuild Task: MSBuild task to simplify implementation of INotifyPropertyChanged interface. Injects supporting code in property setters: raising PropertyChanged event when value changed. LocalizationLibrary: The Localization Library is a collection of reusable software component that provide support for localization. This library enables you to localize WPF (Windows Presentation Foundation), Silverlight and WP7 (Windows Phone 7) applications.M1Library: Simple home library managernerdcms: nerdcms.PkrClck: I don't have a summary yet.Poplar: Poplar populates trees.Pyxis 2: NETMF based Operating EnvironmentSchifra Reed Solomon Error Correcting Code Library: Schifra is a very robust, highly optimized and extremely configurable Reed-Solomon error correcting code library for both software and IP core based applications with implementations in C++ and VHDL. Sharepoint (WSS 3.0, MOSS 2007) Reference Samples: A project that contains Sharepoint (WSS 3.0, MOSS 2007) Reference Samples including Custom Site Definition Feature, Custom List View Web Part Feature, List Event Receiver Feature with Feature Receiver, and Custom Theme Feature.Sharepoint 2010 Reset Version Number: Two workflows for SharePoint 2010 which will renumber the versions of an item depending on your needs.Silverlight Control Templates: Replace the default look of Silverlight controls with animated templates.TeamBuy???: ASP.NET????The C++ String Toolkit Library: The C++ String Toolkit Library (StrTk) consists of robust, optimized and portable string processing algorithms for the C++ language. StrTk is designed to be easy to use and integrate within existing code bases. The E2 Compiler and Simulator: The E2 compiler and simulator.tinymceaspdotnet: TinyMceEditor with image uploaderTwinkle Tasks: Twinkle Tasks (TT) is a file based work item tracking (WIT) system designed to work on the command prompt in conjunction with Distributed Version Control Systems (DVCS), such as Mercurial and GIT. UserVoice Helper for WebMatrix: The UserVoice Helper for WebMatrix and ASP.NET Web Pages allows you to easily add UserVoice feedback functionality to your site. Helper also wraps several public API calls. web pejsci: Jedna se o jednoduchy web o psech, s jednoduchym administracnim rozhranim v ASP.NETWykobi Computational Geometry Library: Wykobi is an efficient, robust and simple to use multi-platform 2D/3D computational geometry library. Wykobi provides a concise, predictable, and deterministic interface for geometric primitives and complex geometric routines using and conforming to the ISO/IEC 14882:2003 C++ lanXL5 Module Sheet Converter: This is for workbooks that contain Excel5/95 Module sheets that require the VBA Converter Pack HotFix download to open (see Microsoft KB 926430). It exports the XL5 Module Sheets, removes them and then imports them back in as a Visual Basic Editor modules.????: ?????????????????，??????????????????，?????????????????，?????，?????????????????????????，??????????????????????????????。 ?????OAuth， ?????.Net Framework4.0, ?????C# ???????????，????????????，???????????。

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• Controlling FPU behavior in an OpenMP program?

  - by STingRaySC

  I have a large C++ program that modifies the FPU control word (using _controlfp()). It unmasks some FPU exceptions and installs a SEHTranslator to produce typed C++ exceptions. I am using VC++ 9.0. I would like to use OpenMP (v.2.0) to parallelize some of our computational loops. I've already successfully applied it to one, but the numerical results are slightly different (though I understand it could also be due to calculations being performed in a different order). I'm assuming this is because the FPU state is thread-specific. Is there some way to have the OpenMP threads inherit that state from the master thread? Or is there some way to specify using OpenMP that new threads execute a particular function that sets up the correct state? What is the idiomatic way to deal with this situation?

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• what languages are used in AI research today?

  - by aaa

  hi. I am currently dabbling in expert systems, emacs lisp, and reading up about artificial intelligence. Traditionally, artificial intelligence is associated with LISP and expert systems with CLIPS. However, I have noticed in computational sciences how much Python is being used. What about the area of artificial intelligence and machine learning? is it still been dominated by LISP? how much is python being used in AI? are any of the newer functional languages, clojure for example, being used in research? in the area of expert systems, which shells are most used/popular today? are there any interesting developments language wise which you know of? Thanks a lot

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• F# performance in scientific computing

  - by aaa

  hello. I am curious as to how F# performance compares to C++ performance? I asked a similar question with regards to Java, and the impression I got was that Java is not suitable for heavy numbercrunching. I have read that F# is supposed to be more scalable and more performant, but how is this real-world performance compares to C++? specific questions about current implementation are: How well does it do floating-point? Does it allow vector instructions how friendly is it towards optimizing compilers? How big a memory foot print does it have? Does it allow fine-grained control over memory locality? does it have capacity for distributed memory processors, for example Cray? what features does it have that may be of interest to computational science where heavy number processing is involved? Are there actual scientific computing implementations that use it? Thanks

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• chomsky hierarchy and programming languages

  - by dader51

  Hi, I'm trying to learn some aspects of the CH ( chomsky hierarchy ) which are related to PL ( programming languages ), and i still have to read the Dragon Book. I've read that most of the PL can be parsed as CFG ( context free grammar ). In term of computational power, it equals the one of a pushdown non deterministic automaton. Am I right ? If it's true, then how could a CFG holds a UG ( unrestricted grammar, which is turing complete ) ? I'm asking because, even if PL are CFG they are actually used to describe TM (turing machines ) and through UG. I think that's because of at least two different levels of computing, the first, which is the parsing of a CFG focuses on the syntax related to the structure ( representation ? ) of the language, while the other focuses on the semantic ( sense, interpretation of the data itself ? ) related to the capabilities of the pl which is turing complete. Again, are these assumptions rights ? thanx a lot.

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• Is it possible to create a quine in every turing-complete language?

  - by sub

  I just wanted to know if it is 100% possible, if my language is turing-complete, to write a program in it that prints itself out (of course not using a file reading function) So if the language just has the really necessary things in order to make it turing complete (I would prove that by translating Brainf*ck code to it), like output, variables, conditions and gotos (hell yes, gotos), can I try writing a quine in it? I'm also asking this because I'm not sure that a quine directly fits into Turing's law that the turing machine is capable of any computational task. I just want to know so I don't try for years without knowing that it may be impossible.

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• Embed a Python persistance layer into a C++ application - good idea?

  - by Rickard

  say I'm about to write an application with a thin GUI layer, a really fat calculation layer (doing computationally heavy calibrations and other long-running stuff) and fairly simple persistance layer. I'm looking at building the GUI + calculation layer in C++ (using Qt for the gui parts). Now - would it be a crazy idea to build the persistance layer in Python, using sqlalchemy, and embed it into the C++ application, letting the layers interface with eachother through lightweigth data transfer objects (written in C++ but accessible from python)? (the other alternative I'm leaning towards would probably be to write the app in Python from the start, using the PyQt wrapper, and then calling into C++ for the computational tasks) Thanks, Rickard

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• How is schoolbook long division an O(n^2) algorithm?

  - by eSKay

  Premise: This Wikipedia page suggests that the computational complexity of Schoolbook long division is O(n^2). Deduction: Instead of taking "Two n-digit numbers", if I take one n-digit number and one m-digit number, then the complexity would be O(n*m). Contradiction: Suppose you divide 100000000 (n digits) by 1000 (m digits), you get 100000, which takes six steps to arrive at. Now, if you divide 100000000 (n digits) by 10000 (m digits), you get 10000 . Now this takes only five steps. Conclusion: So, it seems that the order of computation should be something like O(n/m). Question: Who is wrong, me or Wikipedia, and where?

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• What is more interesting or powerful: Curry/Mercury/Lambda-Prolog/your suggestion.

  - by Bubba88

  Hi! I would like to ask you about what formal system could be more interesting to implement from scratch/reverse engineer. I've looked through some existing and rather open (open in the sense of free/open-source) projects of logical/declarative programming systems. I've decided to make up something similar in my free time, or at least to catch the general idea of implementation. It would be great if some of these systems would provide most of the expressive power and conciseness of modern academic investigations in logic and it's relation with computational models. What would you recommend to study at least at the conceptual level? For example, Lambda-Prolog is interesting particularly because it allows for higher order relations, but AFAIK (I might really be mistaken :)) is based on intuitionist logic and therefore lack the excluded-middle principle; that's generally a disatvantage for me.. I would also welcome any suggestions about modern logical programming systems which are less popular but more expressive/powerful. I guess, this question will need refactoring, but thank you in advance! :)

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• Concise description of the lua vm?

  - by anon

  I've skimmed Programing in Lua, I've looked at the Lua Reference. However, they both tells me this function does this, but not how. When reading SICP, I got this feeling of: "ah, here's the computational model underlying scheme"; I'm trying to get the same sense concerning lua -- i.e. a concise description of it's vm, a "how" rather than a "what". Does anyone know of a good document (besides the C source) describing this? Thanks!

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• what practical proofs are there about the Turing completeness of neural nets? what nns can execute c

  - by Albert

  I'm interested in the computational power of neural nets. It is generally accepted that recurrent neural nets are Turing complete. Now I was searching for some papers which proofs this. What I found so far: Turing computability with neural nets, Hava T. Siegelmann and Eduardo D. Sontag, 1991 I think this is only interesting from a theoretical point of view because it needs to have the neuron activity of infinite exactness (to encode the state somehow as a rational number). S. Franklin and M. Garzon, Neural computability This needs an unbounded number of neurons and also doesn't really seem to be that much practical. (Note that another question of mine tries to point out this kind of problem between such theoretical results and the practice.) I'm searching mostly for some neural net which really can execute some code which I can also simulate and test in practice. Of course, in practice, they would have some kind of limited memory. Does anyone know something like this?

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• What is the optimal number of threads for performing IO operations in java?

  - by marc

  In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade performance..." My question is, when performing I/O operations such as file writing, file reading, file deleting, etc, are there guidelines for the number of threads to use to achieve maximum performance? I understand this will be just a guide number, since disk speeds and a host of other factors play into this. Still, I'm wondering: can 20 threads write 1000 separate files to disk faster than 4 threads can on a 4-cpu machine?

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• Faster way to compare two sets of points in N-dimensional space?

  - by Amit

  List1 contains a high number (~7^10) of N-dimensional points (N <=10), List2 contains the same or fewer number of N-dimensional points (N <=10). My task is this: I want to check which point in List2 is closest (euclidean distance) to a point in List1 for every point in List1 and subsequently perform some operation on it. I have been doing it the simple- the nested loop way when I didn't have more than 50 points in List1, but with 7^10 points, this obviously takes up a lot of time. What is the fastest way to do this? Any concepts from Computational Geometry might help?

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• How long can a hash left out in the open be considered safe?

  - by Xeoncross

  If I were to leave a SHA2 family hash out on my website - how long would it be considered safe? How long would I have before I could be sure that someone would find a collision for it and know what was hashed? I know that the amount of time would be based on the computational power of the one seeking to break it. It would also depend on the string length, but I'm curious just how secure hashes are. Since many of us run web-servers we constantly have to be prepared for the day when someone might make it all the way to the database which stores the user hashes. So, move the server security out of the way and then what do you have? This is a slightly theoretical area for many of the people I have talked with, so I would love to actually have some more information about average expectations for cracking.

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• Why are C, C++, and LISP so prevalent in embedded devices and robots?

  - by David

  It seems that the software language skills most sought for embedded devices and robots are C, C++, and LISP. Why haven't more recent languages made inroads into these applications? For example, Erlang would seem particularly well-suited to robotic applications, since it makes concurrent programming easier and allows hot swapping of code. Python would seem to be useful, if for no other reason than its support of multiple programming paradigms. I'm even surprised that Java hasn't made a foray into general robotic programming. I'm sure one argument would be, "Some newer languages are interpreted, not compiled" - implying that compiled languages are quicker and use fewer computational resources. Is this still the case, in a time when we can put a Java Virtual Machine on a cell phone or a SunSpot? (and isn't LISP interpreted anyway?)

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• C++ Virtual keyword as away to avoid including code units.

  - by user394663

  Currently we have a body of code that allows service plugins which offer forms of communication to the core e.g tcp/ip, udp/ip, usb, etc... These service plugins feedback notifier class instances to the core for further processing. In the current implementation a service project (which is a separate dynamically linked library brought in at runtime by the core via dlopen and friends) will compile against the notifier.cpp file that resides in the core source code (a separate project). This gives access to the notifiers method implementations. This works perfectly no complaints. Two alternative options: 1. put the notifier method implementations in the header file. 2. declare the notifier methods virtual and delay binding until runtime. Avoiding the issues of computational overhead what are the impacts of option 2? Are there any other options available to us? Thanks

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