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  • How to run system-commands in the background?

    - by sid_com
    #!/usr/bin/env perl use warnings; use strict; use 5.012; use IPC::System::Simple qw(system); system( 'xterm', '-geometry', '80x25-5-5', '-bg', 'green', '&' ); say "Hello"; say "World"; I tried this to run the xterm-command in the background, but it doesn't work: No absolute path found for shell: & What would be the right way to make it work?

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  • Postgresql error: could not open segment 1 of relation base/20983/2416

    - by kokonut
    I'm running a Postgresql query and getting the following error: ActiveRecord::StatementInvalid (PGError: ERROR: could not open segment 1 of relation base/20983/24161 (target block 5046584): No such file or directory The query is of the format 'SELECT "locations".* FROM "locations" WHERE ("locations"."id" IN (115990, 78330, 77891, 78248, ...)' with about 600 ids in the IN clause - not an optimal query I know but it's what I have to work with for the moment! The server is running PostgreSQL 8.4.6 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.4.real (Ubuntu 4.4.1-4ubuntu9) 4.4.1, 64-bit. Postgis 1.5 is also installed, and the locations table contains a geometry column. Anyone have any idea what could be causing the error? Thanks!

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  • Python/Tkinter make a custom window

    - by user1435947
    I want to make a window without the top taskbar (that is movable), so there is only thin outline around the GUI box. I also want to add my own 'X' to the box. import Tkinter class Application(Frame): def __init__(self, master=None): Frame.__init__(self, master) self.parent = master ............ def main(): root = Tk() root.attributes('-fullscreen', True) root.geometry('500x250+500+200') app = Application(root) app.parent.configure(background = 'gray32') root.resizable(width=FALSE, height=FALSE) app.mainloop() main() I tried forcing the box to resize after going into fullscreen to remove the taskbar, though box is no longer movable. Any suggestions? [I have seen this thread: Python/Tkinter: Removing/disabling a resizable window's maximize button under Windows The -toolwindow attribute didn't work for me, maybe because I use linux...]

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  • Explain to me the following VS 2010 Extension Sample code..

    - by ealshabaan
    Coders, I am building a VS 2010 extension and I am experimenting around some of the samples that came with the VS 2010 SDK. One of the sample projects is called TextAdornment. In that project there is a weirdo class that looks like the following: [Export(typeof(IWpfTextViewCreationListener))] [ContentType("text")] [TextViewRole(PredefinedTextViewRoles.Document)] internal sealed class TextAdornment1Factory : IWpfTextViewCreationListener While I was experimenting with this project, I tried to debug the project to see the flow of the program and I noticed that this class gets hit when I first start the debugging. Now my question is the following: what makes this class being the first class to get called when VS starts? In other words, why this class gets active and it runs as of some code instantiate an object of this class type? Here is the only two files in the sample project: TextAdornment1Factory.cs using System.ComponentModel.Composition; using Microsoft.VisualStudio.Text.Editor; using Microsoft.VisualStudio.Utilities; namespace TextAdornment1 { #region Adornment Factory /// /// Establishes an to place the adornment on and exports the /// that instantiates the adornment on the event of a 's creation /// [Export(typeof(IWpfTextViewCreationListener))] [ContentType("text")] [TextViewRole(PredefinedTextViewRoles.Document)] internal sealed class TextAdornment1Factory : IWpfTextViewCreationListener { /// /// Defines the adornment layer for the adornment. This layer is ordered /// after the selection layer in the Z-order /// [Export(typeof(AdornmentLayerDefinition))] [Name("TextAdornment1")] [Order(After = PredefinedAdornmentLayers.Selection, Before = PredefinedAdornmentLayers.Text)] [TextViewRole(PredefinedTextViewRoles.Document)] public AdornmentLayerDefinition editorAdornmentLayer = null; /// <summary> /// Instantiates a TextAdornment1 manager when a textView is created. /// </summary> /// <param name="textView">The <see cref="IWpfTextView"/> upon which the adornment should be placed</param> public void TextViewCreated(IWpfTextView textView) { new TextAdornment1(textView); } } #endregion //Adornment Factory } TextAdornment1.cs using System.Windows; using System.Windows.Controls; using System.Windows.Media; using Microsoft.VisualStudio.Text; using Microsoft.VisualStudio.Text.Editor; using Microsoft.VisualStudio.Text.Formatting; namespace TextAdornment1 { /// ///TextAdornment1 places red boxes behind all the "A"s in the editor window /// public class TextAdornment1 { IAdornmentLayer _layer; IWpfTextView _view; Brush _brush; Pen _pen; ITextView textView; public TextAdornment1(IWpfTextView view) { _view = view; _layer = view.GetAdornmentLayer("TextAdornment1"); textView = view; //Listen to any event that changes the layout (text changes, scrolling, etc) _view.LayoutChanged += OnLayoutChanged; _view.Closed += new System.EventHandler(_view_Closed); //selectedText(); //Create the pen and brush to color the box behind the a's Brush brush = new SolidColorBrush(Color.FromArgb(0x20, 0x00, 0x00, 0xff)); brush.Freeze(); Brush penBrush = new SolidColorBrush(Colors.Red); penBrush.Freeze(); Pen pen = new Pen(penBrush, 0.5); pen.Freeze(); _brush = brush; _pen = pen; } void _view_Closed(object sender, System.EventArgs e) { MessageBox.Show(textView.Selection.IsEmpty.ToString()); } /// <summary> /// On layout change add the adornment to any reformatted lines /// </summary> private void OnLayoutChanged(object sender, TextViewLayoutChangedEventArgs e) { foreach (ITextViewLine line in e.NewOrReformattedLines) { this.CreateVisuals(line); } } private void selectedText() { } /// <summary> /// Within the given line add the scarlet box behind the a /// </summary> private void CreateVisuals(ITextViewLine line) { //grab a reference to the lines in the current TextView IWpfTextViewLineCollection textViewLines = _view.TextViewLines; int start = line.Start; int end = line.End; //Loop through each character, and place a box around any a for (int i = start; (i < end); ++i) { if (_view.TextSnapshot[i] == 'a') { SnapshotSpan span = new SnapshotSpan(_view.TextSnapshot, Span.FromBounds(i, i + 1)); Geometry g = textViewLines.GetMarkerGeometry(span); if (g != null) { GeometryDrawing drawing = new GeometryDrawing(_brush, _pen, g); drawing.Freeze(); DrawingImage drawingImage = new DrawingImage(drawing); drawingImage.Freeze(); Image image = new Image(); image.Source = drawingImage; //Align the image with the top of the bounds of the text geometry Canvas.SetLeft(image, g.Bounds.Left); Canvas.SetTop(image, g.Bounds.Top); _layer.AddAdornment(AdornmentPositioningBehavior.TextRelative, span, null, image, null); } } } } } }

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  • Is there a transformation matrix that can scale the x and/or y axis logarithmically?

    - by Dave M
    I'm using .net WPF geometry classes to graph waveforms. I've been using the matrix transformations to convert from the screen coordinate space to my coordinate space for the waveform. Everything works great and it's really simple to keep track of my window and scaling, etc. I can even use the inverse transform to calculate the mouse position in terms of the coordinate space. I use the built in Scaling and Translation classes and then a custom matrix to do the y-axis flipping (there's not a prefab matrix for flipping). I want to be able to graph these waveforms on a log scale as well (either x axis or y axis or both), but I'm not sure if this is even possible to do with a matrix transformation. Does anyone know if this is possible, and if it is, what is the matrix?

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  • How to create a shape acting like a textbox?

    - by subho100
    Please refer this control http://www.charlespetzold.com/blog/2009/10/Using-Text-Outlines-in-Silverlight.html The formattedtext control is a shape which helps to generate the shape of the text with proper geometry. I would like to make this control act like a text box with cursors and features like typing in from keyboard. Right now I use an invisible text box with a formattedtext control to act like that. But the cursor position always creates a problem when the size of the text is not equal to the size of the rendered text as shape. Can anyone please show the way to achieve this.

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  • Retrieving Gtk::Widget's relative position: get_allocate() doesn't work

    - by a-v
    I need to retrieve the position of a Gtk::Widget relative to its parent, a Gtk::Table. Most sources (e.g. http://library.gnome.org/devel/gtk-faq/stable/x642.html) say that one needs to call Gtk::Widget::get_allocation(). However, the returned Gtk::Allocation object always contains x = -1, y = -1, width = 1, height = 1. I have to note that this happens before the Gtk::Table object is actually exposed and rendered. A call to show_all_children() or check_resize(), which I would expect to recalculate child widget geometry, doesn't help. What am I doing wrong? Thanks in advance.

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  • Is there a way to substr a value returned by toShortString()?

    - by Jym Khana
    I am working with openlayers and I can get a point on a map but I can't get the individual coords. feat = drawLayer.features[0]; var geom = feat.geometry; var loca = geom.toShortString(); var long = loc.substr(0,9); alert(geom.toShortString());//returns the correct coords in xx.xxx,xx.xxx format alert(loca);//returns 2 very large numbers in xx.xxx,xx.xxx format alert(long);//returns the first, incorrect number What exaclty am I doing wrong and how can I correct it? Thanks

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  • This Week in Geek History: Gmail Goes Public, Deep Blue Wins at Chess, and the Birth of Thomas Edison

    - by Jason Fitzpatrick
    Every week we bring you a snapshot of the week in Geek History. This week we’re taking a peek at the public release of Gmail, the first time a computer won against a chess champion, and the birth of prolific inventor Thomas Edison. Gmail Goes Public It’s hard to believe that Gmail has only been around for seven years and that for the first three years of its life it was invite only. In 2007 Gmail dropped the invite only requirement (although they would hold onto the “beta” tag for another two years) and opened its doors for anyone to grab a username @gmail. For what seemed like an entire epoch in internet history Gmail had the slickest web-based email around with constant innovations and features rolling out from Gmail Labs. Only in the last year or so have major overhauls at competitors like Hotmail and Yahoo! Mail brought other services up to speed. Can’t stand reading a Week in Geek History entry without a random fact? Here you go: gmail.com was originally owned by the Garfield franchise and ran a service that delivered Garfield comics to your email inbox. No, we’re not kidding. Deep Blue Proves Itself a Chess Master Deep Blue was a super computer constructed by IBM with the sole purpose of winning chess matches. In 2011 with the all seeing eye of Google and the amazing computational abilities of engines like Wolfram Alpha we simply take powerful computers immersed in our daily lives for granted. The 1996 match against reigning world chest champion Garry Kasparov where in Deep Blue held its own, but ultimately lost, in a  4-2 match shook a lot of people up. What did it mean if something that was considered such an elegant and quintessentially human endeavor such as chess was so easy for a machine? A series of upgrades helped Deep Blue outright win a match against Kasparov in 1997 (seen in the photo above). After the win Deep Blue was retired and disassembled. Parts of Deep Blue are housed in the National Museum of History and the Computer History Museum. Birth of Thomas Edison Thomas Alva Edison was one of the most prolific inventors in history and holds an astounding 1,093 US Patents. He is responsible for outright inventing or greatly refining major innovations in the history of world culture including the phonograph, the movie camera, the carbon microphone used in nearly every telephone well into the 1980s, batteries for electric cars (a notion we’d take over a century to take seriously), voting machines, and of course his enormous contribution to electric distribution systems. Despite the role of scientist and inventor being largely unglamorous, Thomas Edison and his tumultuous relationship with fellow inventor Nikola Tesla have been fodder for everything from books, to comics, to movies, and video games. Other Notable Moments from This Week in Geek History Although we only shine the spotlight on three interesting facts a week in our Geek History column, that doesn’t mean we don’t have space to highlight a few more in passing. This week in Geek History: 1971 – Apollo 14 returns to Earth after third Lunar mission. 1974 – Birth of Robot Chicken creator Seth Green. 1986 – Death of Dune creator Frank Herbert. Goodnight Dune. 1997 – Simpsons becomes longest running animated show on television. Have an interesting bit of geek trivia to share? Shoot us an email to [email protected] with “history” in the subject line and we’ll be sure to add it to our list of trivia. Latest Features How-To Geek ETC Here’s a Super Simple Trick to Defeating Fake Anti-Virus Malware How to Change the Default Application for Android Tasks Stop Believing TV’s Lies: The Real Truth About "Enhancing" Images The How-To Geek Valentine’s Day Gift Guide Inspire Geek Love with These Hilarious Geek Valentines RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? Clean Up Google Calendar’s Interface in Chrome and Iron The Rise and Fall of Kramerica? [Seinfeld Video] GNOME Shell 3 Live CDs for OpenSUSE and Fedora Available for Testing Picplz Offers Special FX, Sharing, and Backup of Your Smartphone Pics BUILD! An Epic LEGO Stop Motion Film [VIDEO] The Lingering Glow of Sunset over a Winter Landscape Wallpaper

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  • Windows Azure Use Case: Web Applications

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Many applications have a requirement to be located outside of the organization’s internal infrastructure control. For instance, the company website for a brick-and-mortar retail company may want to post not only static but interactive content to be available to their external customers, and not want the customers to have access inside the organization’s firewall. There are also cases of pure web applications used for a great many of the internal functions of the business. This allows for remote workers, shared customer/employee workloads and data and other advantages. Some firms choose to host these web servers internally, others choose to contract out the infrastructure to an “ASP” (Application Service Provider) or an Infrastructure as a Service (IaaS) company. In any case, the design of these applications often resembles the following: In this design, a server (or perhaps more than one) hosts the presentation function (http or https) access to the application, and this same system may hold the computational aspects of the program. Authorization and Access is controlled programmatically, or is more open if this is a customer-facing application. Storage is either placed on the same or other servers, hosted within an RDBMS or NoSQL database, or a combination of the options, all coded into the application. High-Availability within this scenario is often the responsibility of the architects of the application, and by purchasing more hosting resources which must be built, licensed and configured, and manually added as demand requires, although some IaaS providers have a partially automatic method to add nodes for scale-out, if the architecture of the application supports it. Disaster Recovery is the responsibility of the system architect as well. Implementation: In a Windows Azure Platform as a Service (PaaS) environment, many of these architectural considerations are designed into the system. The Azure “Fabric” (not to be confused with the Azure implementation of Application Fabric - more on that in a moment) is designed to provide scalability. Compute resources can be added and removed programmatically based on any number of factors. Balancers at the request-level of the Fabric automatically route http and https requests. The fabric also provides High-Availability for storage and other components. Disaster recovery is a shared responsibility between the facilities (which have the ability to restore in case of catastrophic failure) and your code, which should build in recovery. In a Windows Azure-based web application, you have the ability to separate out the various functions and components. Presentation can be coded for multiple platforms like smart phones, tablets and PC’s, while the computation can be a single entity shared between them. This makes the applications more resilient and more object-oriented, and lends itself to a SOA or Distributed Computing architecture. It is true that you could code up a similar set of functionality in a traditional web-farm, but the difference here is that the components are built into the very design of the architecture. The API’s and DLL’s you call in a Windows Azure code base contains components as first-class citizens. For instance, if you need storage, it is simply called within the application as an object.  Computation has multiple options and the ability to scale linearly. You also gain another component that you would either have to write or bolt-in to a typical web-farm: the Application Fabric. This Windows Azure component provides communication between applications or even to on-premise systems. It provides authorization in either person-based or claims-based perspectives. SQL Azure provides relational storage as another option, and can also be used or accessed from on-premise systems. It should be noted that you can use all or some of these components individually. Resources: Design Strategies for Scalable Active Server Applications - http://msdn.microsoft.com/en-us/library/ms972349.aspx  Physical Tiers and Deployment  - http://msdn.microsoft.com/en-us/library/ee658120.aspx

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  • VirtualBox 3.2 is released! A Red Letter Day?

    - by Fat Bloke
    Big news today! A new release of VirtualBox packed full of innovation and improvements. Over the next few weeks we'll take a closer look at some of these new features in a lot more depth, but today we'll whet your appetite with the headline descriptions. To start with, we should point out that this is the first Oracle-branded version which makes today a real Red-letter day ;-)  Oracle VM VirtualBox 3.2 Version 3.2 moves VirtualBox forward in 3 main areas ( handily, all beginning with "P" ) : performance, power and supported guest operating system platforms.  Let's take a look: Performance New Latest Intel hardware support - Harnessing the latest in chip-level support for virtualization, VirtualBox 3.2 supports new Intel Core i5 and i7 processor and Intel Xeon processor 5600 Series support for Unrestricted Guest Execution bringing faster boot times for everything from Windows to Solaris guests; New Large Page support - Reducing the size and overhead of key system resources, Large Page support delivers increased performance by enabling faster lookups and shorter table creation times. New In-hypervisor Networking - Significant optimization of the networking subsystem has reduced context switching between guests and host, increasing network throughput by up to 25%. New New Storage I/O subsystem - VirtualBox 3.2 offers a completely re-worked virtual disk subsystem which utilizes asynchronous I/O to achieve high-performance whilst maintaining high data integrity; New Remote Video Acceleration - The unique built-in VirtualBox Remote Display Protocol (VRDP), which is primarily used in virtual desktop infrastructure deployments, has been enhanced to deliver video acceleration. This delivers a rich user experience coupled with reduced computational expense, which is vital when servers are running hundreds of virtual machines; Power New Page Fusion - Traditional Page Sharing techniques have suffered from long and expensive cache construction as pages are scrutinized as candidates for de-duplication. Taking a smarter approach, VirtualBox Page Fusion uses intelligence in the guest virtual machine to determine much more rapidly and accurately those pages which can be eliminated thereby increasing the capacity or vm density of the system; New Memory Ballooning- Ballooning provides another method to increase vm density by allowing the memory of one guest to be recouped and made available to others; New Multiple Virtual Monitors - VirtualBox 3.2 now supports multi-headed virtual machines with up to 8 virtual monitors attached to a guest. Each virtual monitor can be a host window, or be mapped to the hosts physical monitors; New Hot-plug CPU's - Modern operating systems such Windows Server 2008 x64 Data Center Edition or the latest Linux server platforms allow CPUs to be dynamically inserted into a system to provide incremental computing power while the system is running. Version 3.2 introduces support for Hot-plug vCPUs, allowing VirtualBox virtual machines to be given more power, with zero-downtime of the guest; New Virtual SAS Controller - VirtualBox 3.2 now offers a virtual SAS controller, enabling it to run the most demanding of high-end guests; New Online Snapshot Merging - Snapshots are powerful but can eat up disk space and need to be pruned from time to time. Historically, machines have needed to be turned off to delete or merge snapshots but with VirtualBox 3.2 this operation can be done whilst the machines are running. This allows sophisticated system management with minimal interruption of operations; New OVF Enhancements - VirtualBox has supported the OVF standard for virtual machine portability for some time. Now with 3.2, VirtualBox specific configuration data is also stored in the standard allowing richer virtual machine definitions without compromising portability; New Guest Automation - The Guest Automation APIs allow host-based logic to drive operations in the guest; Platforms New USB Keyboard and Mouse - Support more guests that require USB input devices; New Oracle Enterprise Linux 5.5 - Support for the latest version of Oracle's flagship Linux platform; New Ubuntu 10.04 ("Lucid Lynx") - Support for both the desktop and server version of the popular Ubuntu Linux distribution; And as a man once said, "just one more thing" ... New Mac OS X (experimental) - On Apple hardware only, support for creating virtual machines run Mac OS X. All in all this is a pretty powerful release packed full of innovation and speedups. So what are you waiting for?  -FB 

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  • newline-ignoring diff / diff across multiple lines / reflow-ignoring diff

    - by Adam
    Does anybody know of a diff-like tool that can show me the changes between two text files, but ignore changes in whitespace including newlines? Here's an example: the quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. the quick brown fox jumped over the lazy bear. All I did was delete one word and reflow it, but "diff -b" detects a change on every line (as it should; I'm not saying this is a bug in diff). But for large LaTeX files this is a major problem; change one word in a long paragraph and the diff you get back is basically useless. By the way, I'm aware that this requires way more computational power than the usual lines-are-atomic diff. I'm only doing this on small human-generated files and am happy to wait a long time if I have to.

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  • Computer science textbooks

    - by Barrett Conrad
    I would like to try the book question a little bit differently. My goal is to know what the community thinks are the quintessential computer science textbooks. <beginsadstory>I lost all of my computer science and math books from college in Hurricane Katrina in 2005. I greatly miss having my familiar tomes to refer to when topics and problems come up, so I am looking to rebuild my library.<endsadstory> What are your recommendations for the best examples of academic caliber books for the field of computer science and its associated mathematics? I am looking for books on subjects like computational theory, programming languages, compilers, operating systems, algorithms and so on. Don't limit your suggestions to your textbooks only. If there is a book you have read that covers computer science or a related math in a formal way, but is not strictly a textbook, I would be love to hear about them as well. Finally, for the sake of creating a good reference for all of us, may I suggest posting one book per answer so they can be rated individually.

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  • Would OpenID or OAuth work for authorization/authentication on a distributed web service?

    - by David Eyk
    We're in the early stages of designing a RESTful/resource-oriented web service API for a computational lingustics application. Because many of the resources we plan to serve are rights-encumbered, a key design decision has been to specify the platform so that each resource provider can expose their own web service that complies with the API spec. This way, the rights owner maintains control over their content (and thus the ability to throttle or deny access at will) and a direct relationship with the consumer, while still being able to participate in in the collaborative network. At the same time, to simplify the job of writing a client for this service, we want to allow a client access to the distributed service through one end-point, with the server handling content negotiation and retrieval from the appropriate providers. Right now, we're at an impasse on authentication/authorization schemes. One of our number has argued for the (technical) simplicity of a central authentication registry, but others are concerned about the organizational complexity of such a scheme. It seems to me, based on an albeit limited understanding of the technologies, that a combination of OpenID and OAuth would do the trick, with a client authenticating with the end-point via OpenID, and the server taking action on the user's behalf with the various content providers using OAuth. I've only ever seen implementations (e.g. stackoverflow, twitter, etc.) where a human was present to intervene, and I still need to do more research on these technologies. Would a scheme like this work for an automated web service, or would it make the client too difficult to implement and operate?

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  • Scalable / Parallel Large Graph Analysis Library?

    - by Joel Hoff
    I am looking for good recommendations for scalable and/or parallel large graph analysis libraries in various languages. The problems I am working on involve significant computational analysis of graphs/networks with 1-100 million nodes and 10 million to 1+ billion edges. The largest SMP computer I am using has 256 GB memory, but I also have access to an HPC cluster with 1000 cores, 2 TB aggregate memory, and MPI for communication. I am primarily looking for scalable, high-performance graph libraries that could be used in either single or multi-threaded scenarios, but parallel analysis libraries based on MPI or a similar protocol for communication and/or distributed memory are also of interest for high-end problems. Target programming languages include C++, C, Java, and Python. My research to-date has come up with the following possible solutions for these languages: C++ -- The most viable solutions appear to be the Boost Graph Library and Parallel Boost Graph Library. I have looked briefly at MTGL, but it is currently slanted more toward massively multithreaded hardware architectures like the Cray XMT. C - igraph and SNAP (Small-world Network Analysis and Partitioning); latter uses OpenMP for parallelism on SMP systems. Java - I have found no parallel libraries here yet, but JGraphT and perhaps JUNG are leading contenders in the non-parallel space. Python - igraph and NetworkX look like the most solid options, though neither is parallel. There used to be Python bindings for BGL, but these are now unsupported; last release in 2005 looks stale now. Other topics here on SO that I've looked at have discussed graph libraries in C++, Java, Python, and other languages. However, none of these topics focused significantly on scalability. Does anyone have recommendations they can offer based on experience with any of the above or other library packages when applied to large graph analysis problems? Performance, scalability, and code stability/maturity are my primary concerns. Most of the specialized algorithms will be developed by my team with the exception of any graph-oriented parallel communication or distributed memory frameworks (where the graph state is distributed across a cluster).

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  • Autodetect Presence of CSV Headers in a File

    - by banzaimonkey
    Short question: How do I automatically detect whether a CSV file has headers in the first row? Details: I've written a small CSV parsing engine that places the data into an object that I can access as (approximately) an in-memory database. The original code was written to parse third-party CSV with a predictable format, but I'd like to be able to use this code more generally. I'm trying to figure out a reliable way to automatically detect the presence of CSV headers, so the script can decide whether to use the first row of the CSV file as keys / column names or start parsing data immediately. Since all I need is a boolean test, I could easily specify an argument after inspecting the CSV file myself, but I'd rather not have to (go go automation). I imagine I'd have to parse the first 3 to ? rows of the CSV file and look for a pattern of some sort to compare against the headers. I'm having nightmares of three particularly bad cases in which: The headers include numeric data for some reason The first few rows (or large portions of the CSV) are null There headers and data look too similar to tell them apart If I can get a "best guess" and have the parser fail with an error or spit out a warning if it can't decide, that's OK. If this is something that's going to be tremendously expensive in terms of time or computation (and take more time than it's supposed to save me) I'll happily scrap the idea and go back to working on "important things". I'm working with PHP, but this strikes me as more of an algorithmic / computational question than something that's implementation-specific. If there's a simple algorithm I can use, great. If you can point me to some relevant theory / discussion, that'd be great, too. If there's a giant library that does natural language processing or 300 different kinds of parsing, I'm not interested.

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  • Haskell Linear Algebra Matrix Library for Arbitrary Element Types

    - by Johannes Weiß
    I'm looking for a Haskell linear algebra library that has the following features: Matrix multiplication Matrix addition Matrix transposition Rank calculation Matrix inversion is a plus and has the following properties: arbitrary element (scalar) types (in particular element types that are not Storable instances). My elements are an instance of Num, additionally the multiplicative inverse can be calculated. The elements mathematically form a finite field (??2256). That should be enough to implement the features mentioned above. arbitrary matrix sizes (I'll probably need something like 100x100, but the matrix sizes will depend on the user's input so it should not be limited by anything else but the memory or the computational power available) as fast as possible, but I'm aware that a library for arbitrary elements will probably not perform like a C/Fortran library that does the work (interfaced via FFI) because of the indirection of arbitrary (non Int, Double or similar) types. At least one pointer gets dereferenced when an element is touched (written in Haskell, this is not a real requirement for me, but since my elements are no Storable instances the library has to be written in Haskell) I already tried very hard and evaluated everything that looked promising (most of the libraries on Hackage directly state that they wont work for me). In particular I wrote test code using: hmatrix, assumes Storable elements Vec, but the documentation states: Low Dimension : Although the dimensionality is limited only by what GHC will handle, the library is meant for 2,3 and 4 dimensions. For general linear algebra, check out the excellent hmatrix library and blas bindings I looked into the code and the documentation of many more libraries but nothing seems to suit my needs :-(. Update Since there seems to be nothing, I started a project on GitHub which aims to develop such a library. The current state is very minimalistic, not optimized for speed at all and only the most basic functions have tests and therefore should work. But should you be interested in using or helping out developing it: Contact me (you'll find my mail address on my web site) or send pull requests.

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  • Small-o(n^2) implementation of Polynomial Multiplication

    - by AlanTuring
    I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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  • Floating point precision in Visual C++

    - by Luigi Giaccari
    HI, I am trying to use the robust predicates for computational geometry from Jonathan Richard Shewchuk. I am not a programmer, so I am not even sure of what I am saying, I may be doing some basic mistake. The point is the predicates should allow for precise aritmthetic with adaptive floating point precision. On my computer: Asus pro31/S (Core Due Centrino Processor) they do not work. The problem may stay in the fact the my computer may use some improvements in the floating point precision taht conflicts with the one used by Shewchuk. The author says: /* On some machines, the exact arithmetic routines might be defeated by the / / use of internal extended precision floating-point registers. Sometimes / / this problem can be fixed by defining certain values to be volatile, / / thus forcing them to be stored to memory and rounded off. This isn't / / a great solution, though, as it slows the arithmetic down. */ Now what I would like to know is that there is a way, maybe some compiler option, to turn off the internal extended precision floating-point registers. I really appriaciate your help

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  • What is faster- Java or C# (Or good old C)?

    - by Rexsung
    I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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  • GUI for generating XML

    - by Kenston
    Hello. Does anybody know of GUIs for generating XMLs? This means the user will not be presented with an IDE with support for XML for him to type XML codes. This would be helpful for non-technical people using the system. I know this sounds easy, given many libraries that can help in generating XMLs. The issue here is that the schema is really that flexible rather than being straightforward like representing books in a library with their properties. Imagine HTML, where we can create font tags inside a body, a table, a div, or nested even within itself. The solution is a WYSIWYG application that allows user to generate html codes (XML). However, that is good for XML applied in webpages since they involve visual aspect and design. My application of XML would focus on representing some conceptual and computational definitions, much like sql-like syntax, but more than that. I'm actually after the approach or previous works done or tried, although having a library/working framework for that would be better. Btw, I'm using Java for this project. Currently, I'm just thinking of presenting element tags where user will be able to drag and drop them and nest them with each other. And perhaps, assist them through a forms in inputing values for XML attributes. I'm still hoping if there are better ideas from the community. Thank you.

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  • CORBA on MacOS X (Cocoa)

    - by user8472
    I am currently looking into different ways to support distributed model objects (i.e., a computational model that runs on several different computers) in a project that initially focuses on MacOS X (using Cocoa). As far as I know there is the possibility to use the class cluster around NSProxy. But there also seem to be implementations of CORBA around with Objective-C support. At a later time there may be the need to also support/include Windows machines. In that case I would need to use something like Gnustep on the Windows side (which may be an option, if it works well) or come up with a combination of both technologies. Or write something manually (which is, of course, the least desirable option). My questions are: If you have experience with both technologies (Cocoa native infrastructure vs. CORBA) can you point out some key features/issues of either approach? Is it possible to use Gnustep with Cocoa in the way explained above? Is it possible (and reasonably feasible, i.e. simpler than writing a network layer manually) to communicate among all MacOS clients using Cocoa's technology and with Windows clients through CORBA?

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  • pure/const functions in C++

    - by Albert
    Hi, I'm thinking of using pure/const functions more heavily in my C++ code. (pure/const attribute in GCC) However, I am curious how strict I should be about it and what could possibly break. The most obvious case are debug outputs (in whatever form, could be on cout, in some file or in some custom debug class). I probably will have a lot of functions, which don't have any side effects despite this sort of debug output. No matter if the debug output is made or not, this will absolutely have no effect on the rest of my application. Or another case I'm thinking of is the use of my own SmartPointer class. In debug mode, my SmartPointer class has some global register where it does some extra checks. If I use such an object in a pure/const function, it does have some slight side effects (in the sense that some memory probably will be different) which should not have any real side effects though (in the sense that the behaviour is in any way different). Similar also for mutexes and other stuff. I can think of many complex cases where it has some side effects (in the sense of that some memory will be different, maybe even some threads are created, some filesystem manipulation is made, etc) but has no computational difference (all those side effects could very well be left out and I would even prefer that). How does it work out in practice? If I mark such functions as pure/const, could it break anything (considering that the code is all correct)?

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  • Is this linear search implementation actually useful?

    - by Helper Method
    In Matters Computational I found this interesting linear search implementation (it's actually my Java implementation ;-)): public static int linearSearch(int[] a, int key) { int high = a.length - 1; int tmp = a[high]; // put a sentinel at the end of the array a[high] = key; int i = 0; while (a[i] != key) { i++; } // restore original value a[high] = tmp; if (i == high && key != tmp) { return NOT_CONTAINED; } return i; } It basically uses a sentinel, which is the searched for value, so that you always find the value and don't have to check for array boundaries. The last element is stored in a temp variable, and then the sentinel is placed at the last position. When the value is found (remember, it is always found due to the sentinel), the original element is restored and the index is checked if it represents the last index and is unequal to the searched for value. If that's the case, -1 (NOT_CONTAINED) is returned, otherwise the index. While I found this implementation really clever, I wonder if it is actually useful. For small arrays, it seems to be always slower, and for large arrays it only seems to be faster when the value is not found. Any ideas?

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  • Travelling software. Is that a concept?

    - by Bubba88
    Hi! This is barely a sensible question. I would like to ask if there existed a program, which were intended to travel (for example following some physical forces) across the planet, possibly occupying and freeing computational resources/nodes. Literally that means that some agent-based system is just regularly changing it's location and (inevitably to some extent) configuration. An example would be: suppose you have external sensors, and free computers - nodes - across the space; would it make sense to self-replicate agents to follow the initializers from sensors, but in such restrictive manner that the computation is only localized at where the physical business is going on. I want to stress that this question is just for 'theoretical' fun, cause I cannot see any practical benefits of the restrictions mentioned, apart from the optimization of 'outdated' (outplaced?) agent disposal. But maybe it could be of some interest. Thank you! EDIT: It's obvious that a virus is fitting example, although the deletion of such agents is rarely of concern of the developers. More precisely, I'm interested in 'travelling' software - that is, when the count (or at least order) of the agents is kind of constant, and it's just the whole system who travels.

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