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  • Converting python collaborative filtering code to use Map Reduce

    - by Neil Kodner
    Using Python, I'm computing cosine similarity across items. given event data that represents a purchase (user,item), I have a list of all items 'bought' by my users. Given this input data (user,item) X,1 X,2 Y,1 Y,2 Z,2 Z,3 I build a python dictionary {1: ['X','Y'], 2 : ['X','Y','Z'], 3 : ['Z']} From that dictionary, I generate a bought/not bought matrix, also another dictionary(bnb). {1 : [1,1,0], 2 : [1,1,1], 3 : [0,0,1]} From there, I'm computing similarity between (1,2) by calculating cosine between (1,1,0) and (1,1,1), yielding 0.816496 I'm doing this by: items=[1,2,3] for item in items: for sub in items: if sub >= item: #as to not calculate similarity on the inverse sim = coSim( bnb[item], bnb[sub] ) I think the brute force approach is killing me and it only runs slower as the data gets larger. Using my trusty laptop, this calculation runs for hours when dealing with 8500 users and 3500 items. I'm trying to compute similarity for all items in my dict and it's taking longer than I'd like it to. I think this is a good candidate for MapReduce but I'm having trouble 'thinking' in terms of key/value pairs. Alternatively, is the issue with my approach and not necessarily a candidate for Map Reduce?

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  • Python optimization problem?

    - by user342079
    Alright, i had this homework recently (don't worry, i've already done it, but in c++) but I got curious how i could do it in python. The problem is about 2 light sources that emit light. I won't get into details tho. Here's the code (that I've managed to optimize a bit in the latter part): import math, array import numpy as np from PIL import Image size = (800,800) width, height = size s1x = width * 1./8 s1y = height * 1./8 s2x = width * 7./8 s2y = height * 7./8 r,g,b = (255,255,255) arr = np.zeros((width,height,3)) hy = math.hypot print 'computing distances (%s by %s)'%size, for i in xrange(width): if i%(width/10)==0: print i, if i%20==0: print '.', for j in xrange(height): d1 = hy(i-s1x,j-s1y) d2 = hy(i-s2x,j-s2y) arr[i][j] = abs(d1-d2) print '' arr2 = np.zeros((width,height,3),dtype="uint8") for ld in [200,116,100,84,68,52,36,20,8,4,2]: print 'now computing image for ld = '+str(ld) arr2 *= 0 arr2 += abs(arr%ld-ld/2)*(r,g,b)/(ld/2) print 'saving image...' ar2img = Image.fromarray(arr2) ar2img.save('ld'+str(ld).rjust(4,'0')+'.png') print 'saved as ld'+str(ld).rjust(4,'0')+'.png' I have managed to optimize most of it, but there's still a huge performance gap in the part with the 2 for-s, and I can't seem to think of a way to bypass that using common array operations... I'm open to suggestions :D

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  • What's the most trivial function that would benfit from being computed on a GPU?

    - by hanDerPeder
    Hi. I'm just starting out learning OpenCL. I'm trying to get a feel for what performance gains to expect when moving functions/algorithms to the GPU. The most basic kernel given in most tutorials is a kernel that takes two arrays of numbers and sums the value at the corresponding indexes and adds them to a third array, like so: __kernel void add(__global float *a, __global float *b, __global float *answer) { int gid = get_global_id(0); answer[gid] = a[gid] + b[gid]; } __kernel void sub(__global float* n, __global float* answer) { int gid = get_global_id(0); answer[gid] = n[gid] - 2; } __kernel void ranksort(__global const float *a, __global float *answer) { int gid = get_global_id(0); int gSize = get_global_size(0); int x = 0; for(int i = 0; i < gSize; i++){ if(a[gid] > a[i]) x++; } answer[x] = a[gid]; } I am assuming that you could never justify computing this on the GPU, the memory transfer would out weight the time it would take computing this on the CPU by magnitudes (I might be wrong about this, hence this question). What I am wondering is what would be the most trivial example where you would expect significant speedup when using a OpenCL kernel instead of the CPU?

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  • Is programming overrated?

    - by aengine
    [Subjective and intended to be a community wiki] I am sorry for such an offensive question: But here are my arguments Most of the progress in "computing" has came from non-programming sources. i.e. People invented faster microprocessors and better routers and novel memory devices. I dont think on average people are writting more efficient programs than those written 10 years ago. And the newer and popular languages are infact slower than C. though speed is one of the lesser criterias. Most of the progress came from novel paradigms. Web, Internet, Cloud computing and Social networking are novel paradigms and did not involve progress in programming as such. Heck even facebook was written in PHP and not some extreme language. Though it did face scalability issues (same with twitter) but i believe money and better programmers (who came in much later) took care of that. Thus ideating capability trumped programming capability/ Even things like Map-Reduce, Column oriented database and Probablistic algorithms (E.g. bloom filters) came from hardcore Algorithms research, rather than some programming convention. Thus my final point is why programming skill is so overstressed? To point a recent example about how only 10% of programmers can "write code" (binary search) without debugging. Isnt it a bit hypocritical, considering your real successs lies in coming up with better algorithm or a novel feature rather than getting right first time???

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  • JavaScript sleep

    - by Diazath
    yes, i know - that question has thousands of answers. please, don't tell me about "setTimeout" method becasuse - yes, everything is possible with that but not so easy as using sleep() method. for example: function fibonacci(n) { console.log("Computing Fibonacci for " + n + "..."); var result = 0; //wait 1 second before computing for lower n sleep(1000); result = (n <= 1) ? 1 : (fibonacci(n - 1) + fibonacci(n - 2)); //wait 1 second before announcing the result sleep(1000); console.log("F(" + n + ") = " + result); return result; } if you know how to get the same result using setTimeout - tell me ;) fibanacci is pretty easy task, because there not more than 2 recursions, but how about n-recursions (like fib(1) + fib(2) + .. + fib(n) and sleep after every "+"? nah, sleep would be muuuuuch easier. but still i can't get working example of implementing it. while (curr - start < time) { curr = (...) } is tricky, but it won't work (just stops my browser and then throw all console.logs at once).

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  • Creative Gesture Camera in Processing

    - by user2892963
    I'm trying to use the creative gesture camera in Processing. I started with the Intel Perceptual Computing SDK, and ran into an issue. I want to get the hand openness, and I am running into some issues - no matter what, the hand.openness returns 0. It otherwise runs quite well... Some Sample code I'm trying to get to work: If you open your hand it starts printing to the console, close it and it stops. import intel.pcsdk.*; PXCUPipeline session; PXCMGesture.GeoNode hand = new PXCMGesture.GeoNode(); void setup() { session = new PXCUPipeline(this); if(!session.Init(PXCUPipeline.GESTURE)) exit(); } void draw() { background(0); if(session.AcquireFrame(false)) { if(session.QueryGeoNode(PXCMGesture.GeoNode.LABEL_BODY_HAND_PRIMARY|PXCMGesture.GeoNode.LABEL_OPEN, hand)) //Only when primary hand is open { rect(0, 0, 10, 10); println(hand.openness + " : " + frameCount); //Openness should be from 0 to 100 } session.ReleaseFrame(); } } Using the current version of Processing (2.0.3), Perceptual Computing SDK Version 7383.

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  • Java Generics, JPA 2, J2EE, JSF 2, GWT, Ajax, Oracle's Java Strategies, Flex, iPhone, Agile ALM, Gra

    - by Kim Won
    Great Indian Developer Summit 2010 – India's Biggest Polyglot Conference and Workshops for IT Software Professionals Bangalore, April 9, 2010: The GIDS.Java Conference and Workshops has announced the complete program of over 50 sessions on the present and future of the Java language and VM, how they are evolving to meet the community's ever-changing needs, and some of the cutting-edge tools, technologies & techniques used for building robust enterprise Java applications today. The GIDs.Java track at Great Indian Developer Summit takes place 22 and 23 April 2010, at the Indian Institute of Science in Bangalore. As one of the longest running independent developer conferences in India, GIDS.Java at the Great Indian Developer Summit 2010 is uniquely positioned to provide a blend of practical, pragmatic and immediately applicable knowledge and a glimpse of the future of technology. During 22 and 23 April 2010, GIDS.Java offers a multi-track conference, workshops, expo show floor, and networking opportunities. The first keynote at GIDS.Java "Pointy Haired Bosses and Pragmatic Programmers" is led by Dr. Venkat Subramaniam. He speaks about how each of us has a professional responsibility to be objective and make decisions that will help us and our teams be productive and deliver results. Venkat will pick on some fallacies, lay down facts, and discuss how to stay professional and objective in our daily efforts. The second keynote of the day explains the practical features that make the Cloud so interesting, and why everyone should start using it in their everyday life. Simone Brunozzi, Amazon Web Services Technology Evangelist, will detail technical examples, business details all mixed with a lot of Italian humor to ensure audience enjoy this talk without a single line of code. The third keynote of the day gives an exciting overview of directions in the Java space for Oracle, featuring concrete signs of Oracles heavy investment, a clear concise strategy overview, and deep dives into some of the most interesting pieces of technology being developed in the Java Platform Group today; such as JavaEE, JDK7, JavaFX, and our exciting new visual tools. Featuring demos by a Java evangelism team star, Simon Ritter, this talk takes you top to bottom in Java Technology. Featured talks at GID.Web include: Good, Bad, and Ugly of Java Generics, Venkat Subramaniam Pure Java Ajax: An Overview of GWT 2.0, Marty Hall How JPA 2.0 Makes a Good Thing Even Better, Mike Keith Building Enterprise RIAs with Adobe Flex and Java, Sujit Reddy G Integrated Ajax Support in JSF 2.0, Marty Hall Design Patterns in Java and Groovy, Venkat Subramaniam A Gentle Introduction to iPhone and Obj-C for Java Developers, Matthew McCullough Cloud Computing: Azure for Java Developers, Janakiram MSV Ajax Support in the Prototype JavaScript Library, Marty Hall First steps to IT Heaven Through the Cloud. Part III: .Java, Simone Brunozi Building Web 2.0 User Interfaces for Web Service Models using JSF, Frank Nimphius and Jobinesh P Acceptance Test Driven Development, John Tobin and Mohammed Mohsinali Architecting Your Java Applications for the Cloud, Praveen Srivatsa Effective Java, Venkat Subramaniam The Amazing Groovy Weight-loss Plan, Scott Davis Enterprise Modeling - from Conceptual Planning to Technical Blueprints, J Sripad Java Collections Renaissance, Donald Raab and Vlad Zakharov Power 7 and IBM J9VM, Himanshu Goyal A Whistle-stop Tour of Maven 3.0, Matthew McCullough Mass Volume Opportunities for Java Developers, Jouko Nuottila Emerging Technology Complex Event Processing, Duvvuri Srinivas Agile ALM for Distributed Development, Karthi Swaminathan Dim Sum Grails - A Sampler of Practical Non Database-Driven Grails Applications, Scott Davis Diagnosing Performance Bottlenecks in J2EE, Deepak Kaul Business Driven Identity Management, Suneet Agera Combining Java EE with OSGi using Eclipse Gemini, Mike Keith Workshop: Essence of Functional Programming, Venkat Subramaniam Workshop: Agile Development, Tools, and Teams and Scrum Certification, Stephen Forte Workshop: Cloud Computing Boot Camp on the Google App Engine, Matthew McCullough Workshop: Building Your First Amazon App, Simone Brunozzi Workshop: The 180-min AJAX and JSON Spike Class, Scott Davis Workshop: PHP + Adobe Flex = Killer RIA, Shyamprasad P Workshop: User Expereince Evaluation Model Walkthrough, Sanna Häiväläinen Workshop: Building Data Centric Applications using Adobe Flex and Java, Prashant Singh Workshop: Monetizing your Apps with PayPal X Payments Platform, Khurram Khan, Praveen Alavilli Sponsors of Great Indian Developer Summit 2010 include: Platinum sponsors Microsoft, Oracle Forum Nokia and Adobe; Gold sponsors Intel and SAP; Silver sponsors Quest Software, PayPal, Telerik and AMT. About Great Indian Developer Summit Great Indian Developer Summit is the gold standard for India's software developer ecosystem for gaining exposure to and evaluating new projects, tools, services, platforms, languages, software and standards. Packed with premium knowledge, action plans and advise from been-there-done-it veterans, creators, and visionaries, the 2010 edition of Great Indian Developer Summit features focused sessions, case studies, workshops and power panels that will transform you into a force to reckon with. Featuring 3 co-located conferences: GIDS.NET, GIDS.Web, GIDS.Java and an exclusive day of in-depth tutorials - GIDS.Workshops, from 20 April to 24 April at the IISc campus in Bangalore. At GIDS you'll participate in hundreds of sessions encompassing the full range of Microsoft computing, Java, Agile, RIA, Rich Web, open source/standards, languages, frameworks and platforms, practical tutorials that deep dive into technical skill and best practices, inspirational keynote presentations, an Expo Hall featuring dozens of the latest projects and products activities, engaging networking events, and the interact with the best and brightest of speakers from around the world. For further information on GIDS 2010, please visit the summit on the web http://www.developersummit.com/ A Saltmarch Media Press Release E: [email protected] Ph: +91 80 4005 1000

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  • Ajax, Lizard Brain Web Design, JSF, Struts, JavaScript, Mobile Web, Flash, jQuery, GWT, Harmony at I

    - by Kim Won
    Great Indian Developer Summit 2010 – India's Biggest Polyglot Conference and Workshops for IT Software Professionals Bangalore, April 9, 2010: The GIDS.Web Conference and Workshops has announced the complete program of over 30 sessions on how browser and rich web technologies such as AJAX, DHTML, Mashups, Web 2.0, Enterprise 2.0 technologies, and Rich UI technologies are making money and gaining market-share for some of the leading businesses in the world. The GIDS.Web track at Great Indian Developer Summit takes place 21 and 23 April 2010, at the Indian Institute of Science in Bangalore. As one of the longest running independent developer conferences in India, GIDS.Web at the Great Indian Developer Summit 2010 is uniquely positioned to provide a blend of practical, pragmatic and immediately applicable knowledge and a glimpse of the future of technology. During 21 and 23 April 2010, GIDS.Web offers a multi-track conference, workshops, expo show floor, and networking opportunities. The first keynote at GIDS.Web is led by the leading Java EE and Ajax developer, speaker, and author Marty Hall. The best of India's Java and RIA programmers have learnt the subject from Marty's seminal books Core Servlets and JavaServer Pages (first and second editions), More Servlets and JavaServer Pages, and Core Web Programming (first and second editions) from Prentice Hall and Sun Microsystems Press. Marty's keynote address is a comparison of approaches to building rich Internet applications with Ajax. Marty says Ajax development is difficult, and there are several fundamentally different strategies to building Ajaxified Web applications. The keynote address will survey the three most important of these approaches: using an Ajax-enabled JavaScript library such as jQuery, Prototype, Scriptaculous, Dojo, or Ext/JS; using a Web framework such as JSF 2.0 or Struts 2 that has integrated Ajax support; using the Google Web Toolkit (GWT) to build "pure Java" Ajax applications. The talk will compare and contrast these three approaches, discussing the types of applications that fit best for each option. Over the course of the summit Marty will conduct several more sessions on "Choosing an Ajax/JavaScript Toolkit: A Comparison of the Most Popular JavaScript Libraries", "Pure Java Ajax: An Overview of GWT 2.0", "Integrated Ajax Support in JSF 2.0" and "Ajax Support in the Prototype JavaScript Library". The second keynote by the head of Adobe's Flash initiative in India, Ramesh Srinivasaraghavan, explores the state of art in web application development and identify trends that could transform the way we create and use web applications. The talk explains how the Adobe Flash Platform has fuelled this revolution with an integrated set of technologies for delivering the most compelling applications, content and video to the widest possible audience. The Director of Forum Nokia will explain how cloud computing coupled with mobile applications enable consumers to have access to powerful services and improved user experiences never before thought possible. IEEE's 2010 President-Elect Sorel Reisman's afternoon address steps to improve the IT profession in India. Featured talks at GID.Web also include: Web 2.0 Checklist - Deconstructing Modern Websites, Scott Davis Choosing an Ajax/JavaScript Toolkit: Comparison of Popular JavaScript Libraries, Marty Hall Lizard Brain Web Design, Scott Davis Effective Design Processes and Resources for Mobile Web Development, Arabella David NoSQL: The Shift to a Non-relational World, Nosh Petigara Open Source Web Debugging Tools, Matthew McCullough Building Line of Business Applications with Silverlight 4.0, Stephen Forte Hadoop - Divide and Conquer, Matthew McCullough Adobe Flash Catalyst for Agile Interaction Design, Harish Sivaramakrishnan Using jQuery and AJAX to Build Front-ends for ASP.NET and ASP.NET MVC, Pandurang Nayak First Steps to IT Heaven Through the Cloud. Part II: .WEB, Simone Brunozzi Building Rich Internet Applications with SL RIA Web Services, Pandurang Nayak Enriching Cloud Applications with Adobe Flash Platform, Ramesh Srinivasaraghavan Payments for the Web.future, Khurram Khan and Praveen Alavilli Longevity of Scalable Systems, Nishad Kamat Transform yourself into a Mobile App Developer Using Web Run Time, Balagopal K S Developing Multi Screen Applications on Adobe Flash Platform, Hemanth Sharma Why Harmony and For Whom?, Himanshu Goyal IIS Hosting Solution for ASP.net and PHP Web Sites, Nahas Mohammed Building Pluggable Web applications using Django, Lakshman Prasad Workshop: The 180-min AJAX and JSON Spike Class, Scott Davis Workshop: Essence of Functional Programming, Venkat Subramaniam Workshop: Agile Development, Tools, and Teams and Scrum Certification, Stephen Forte Workshop: PHP + Adobe Flex = Killer RIA, Shyamprasad P Workshop: Cloud Computing Boot Camp on the Google App Engine, Matthew McCullough Workshop: Building Data Centric Applications using Adobe Flex and Java, Prashant Singh Workshop: Building Your First Amazon App, Simone Brunozzi Workshop: Windows Azure Deep Dive, Ramaprasanna Chellamuthu Workshop: Monetizing your Apps with PayPal X Payments Platform, Khurram Khan, Praveen Alavilli Workshop: User Expereince Evaluation Model Walkthrough, Sanna Häiväläinen Sponsors of Great Indian Developer Summit 2010 include: Platinum sponsors Microsoft, Oracle Forum Nokia and Adobe; Gold sponsors Intel and SAP; Silver sponsors Quest Software, PayPal, Telerik and AMT. About Great Indian Developer Summit Great Indian Developer Summit is the gold standard for India's software developer ecosystem for gaining exposure to and evaluating new projects, tools, services, platforms, languages, software and standards. Packed with premium knowledge, action plans and advise from been-there-done-it veterans, creators, and visionaries, the 2010 edition of Great Indian Developer Summit features focused sessions, case studies, workshops and power panels that will transform you into a force to reckon with. Featuring 3 co-located conferences: GIDS.NET, GIDS.Web, GIDS.Java and an exclusive day of in-depth tutorials - GIDS.Workshops, from 20 April to 24 April at the IISc campus in Bangalore. At GIDS you'll participate in hundreds of sessions encompassing the full range of Microsoft computing, Java, Agile, RIA, Rich Web, open source/standards, languages, frameworks and platforms, practical tutorials that deep dive into technical skill and best practices, inspirational keynote presentations, an Expo Hall featuring dozens of the latest projects and products activities, engaging networking events, and the interact with the best and brightest of speakers from around the world. For further information on GIDS 2010, please visit the summit on the web http://www.developersummit.com/ A Saltmarch Media Press Release E: [email protected] Ph: +91 80 4005 1000

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  • Conceptually how does load-balancing on the EJB tier work in Glassfish/any ejb container

    - by Benju
    I am wondering conceptually how load-balancing works on the EJB-level (not web session replication) with Java EE containers like Glassfish. From what I have gleaned your remote interface is a proxy that delegates your call to one of many servers you may have in an environment. If things fail are they supposed to be able to "finish" on another server? I want to understand the basic theory behind this load balancing, why is it better than a bunch of servers all running a plain web application with session affinity on a load-balancer?

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  • Drag and drop with an image

    - by DJClayworth
    I need to create a drag and drop system in swing where an image of the thing being dragged is attached to the cursor during the drag. In theory this is achieveable with public Icon getVisualRepresentation(Transferable t) but there appears to be a long standing bug (here) that means this method is never called. I know I can do it by implementing my own DnD system with DragSource etc., but does anyone know of an easier workround that will get me what I need?

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  • Any recommended java profiling tutorial?

    - by Wing C. Chen
    Is there any recommended java application profiling tutorial? I am now using jProfiler and eclipse TPTP with my profiling. However, although equipped with wonderful weapons, as a newbie in java profiling, I am still missing the general theory and skill in pinpointing the bottleneck. So would you please provide me with some recommended tutorial for java profiling?

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  • Android: How to detect end of scroll

    - by Mix
    Hi! I need to implement HorizontalScrollView which is scrolled to predefined positions (similar to Home behaviour). It works with slow gestures, but does not work with flings. I hooked to View.onScrollChanged() and it is called when scrolling happened, but I can't determine when scrolling ends. In theory there should be a way to say that fling is over. Is there such API?

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  • Any rerefence of CPU world statistics?

    - by Áxel Costas Pena
    I am looking for any referencee about computer power statistics across the world. My main interest is about real computing capabilities, so I'd prefer information about real processor power, and even best if it includes also other critical hardware statistics, like RAM memory, but if it isn't possible, maybe statistics about brand/model distribution will be also useful. I've Googled for some minutes and I've found nothing related.

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  • domain specific languages and compilers

    - by hyperboreean
    I was looking over Martin Fowler's recent book contents - Domain Specific Languages and I noticed some ANTLR example - that got me thinking that writing compilers will become more and more popular since people needs in this matter will increase. So, will the compiler theory still be as arid (being subjective here) as it was until now or are there any chances that we'll get more applied, programmer oriented materials ?

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  • How can you animate a sprite in SFML (C++)

    - by Apoc
    Lets say I have 4 images and I want to use these 4 images to animate a character. The 4 images represent the character walking. I want the animation to repeat itself as long as I press the key to move but to stop right when I unpress it. It doesn't need to be SFML specific if you don't know it, just basic theory would really help me. Thank you.

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  • How can I run the same Linux Installation on my hardware and in a virtual machine?

    - by LithMaster
    I've started some development that requires Linux (I'm currently on Ubuntu, but I may switch to Debian), but I still use Windows 7 for my day-to-day computing. I have already tried a dual-boot setup, but I've found that it is too cumbersome to switch between Linux and Windows. I'm wondering if it's possible to setup an installation of Linux (again, Ubuntu or Debian) on a partition of my hard drive that I can also run from Windows in a virtualized environment.

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  • Odd ActiveRecord model dynamic initialization bug in production

    - by qfinder
    I've got an ActiveRecord (2.3.5) model that occasionally exhibits incorrect behavior that appears to be related to a problem in its dynamic initialization. Here's the code: class Widget < ActiveRecord::Base extend ActiveSupport::Memoizable serialize :settings VALID_SETTINGS = %w(show_on_sale show_upcoming show_current show_past) VALID_SETTINGS.each do |setting| class_eval %{ def #{setting}=(val); self.settings[:#{setting}] = (val == "1"); end def #{setting}; self.settings[:#{setting}]; end } end def initialize_settings self.settings ||= { :show_on_sale => true, :show_upcoming => true } end after_initialize :initialize_settings # All the other stuff the model does end The idea was to use a single record field (settings) to persist a bunch of configuration data for this object, but allow all the settings to seamlessly work with form helpers and the like. (Why this approach makes sense here is a little out of scope, but let's assume that it does.) Net-net, Widget should end up with instance methods (eg #show_on_sale= #show_on_sale) for all the entires in the VALID_SETTINGS array. Any default values should be specified in initialize_settings. And indeed this works, mostly. In dev and staging, no problems at all. But in production, the app sometimes ends up in a state where a) any writes to the dynamically generated setters fail and b) none of the default values appear to be set - although my leading theory is that the dynamically generated reader methods are just broken. The code, db, and environment is otherwise identical between the three. A typical error message / backtrace on the fail looks like: IndexError: index 141145 out of string (eval):2:in []=' (eval):2:inshow_on_sale=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:in send' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:in each' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2634:in `update_attributes!' ...(then controller and all the way down) Ideas or theories as to what might be going on? My leading theory is that something is going wrong in instance initialization wherein the class instance variable settings is ending up as a string rather than a hash. This explains both the above setter failure (:show_on_sale is being used to index into the string) and the fact that getters don't work (an out of bounds [] call on a string just returns nil). But then how and why might settings occasionally end up as a string rather than hash?

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  • Best Planar graph program

    - by brian
    In graph theory, a planar graph is a graph that can be embedded in the plane, i.e., it can be drawn on the plane in such a way that its edges intersect only at their endpoints. What is the best open source program for drawing the planar graph with support of input nodes size and fixed drawing boundary region

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  • shortest directed odd cycle

    - by gleb-pendler
    6.1.4 Describe an algorithm based on breadth-first search for finding a shortest odd cycle in a graph. 6.3.5 Describe an algorithm based on directed breadth-first search for finding a shortest directed odd cycle in a digraph. what is most importent is that it must be a directed graph not necessary bfs but must be the shortest directed odd cycle!!! Question was taken from "Graph Theory" by J.A. Bondy and U.S.R. Murty thanks in advance!!!

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  • How would you handle making an array or list that would have more entries than the standard implemen

    - by faceless1_14
    I am trying to create an array or list that could handle in theory, given adequate hardware and such, as many as 100^100 BigInteger entries. The problem with using an array or standard list is that they can only hold Integer.MAX_VALUE number of entries. How would you work around this limitations? A whole new class/interface? A wrapper for list? another data type entirely?

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  • Good introductory statistics book?

    - by lmsasu
    Hello, what is a good introductory statistics book you can recommend? if there is a whole sequence of books that should be read, please do not hesitate to mention it. Books with applications are also welcome. I am aware that a single search on Amazon (or any other book seller) will provide me tons of titles, but some of them are avoidable... About my background/knowledge: good knowledge of mathematics and probability theory, but almost null on statistics.

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