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  • Convex Hull for Concave Objects

    - by Lighthink
    I want to implement GJK and I want it to handle concave shapes too (almost all my shapes are concave). I've thought of decomposing the concave shape into convex shapes and then building a hierarchical tree out of convex shapes, but I do not know how to do it. Nothing I could find on the Internet about it wasn't satisfying my needs, so maybe someone can point me in the right direction or give a full explanation.

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  • Search Engine Optimization - The Importance of Page Optimization in Search Engine Optimization

    In order for your website to rank well, your internal linking structure is critical to your success. This is covered some of the theory for this in various articles and blogs about Page Structure of a website, which said how you should map out the physical linking structure, but in this guide I will explain more about the importance of interlinking your pages, while using your targeted keyword in your anchor text.

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  • Performance and Optimization Isn’t Evil

    - by Reed
    Donald Knuth is a fairly amazing guy.  I consider him one of the most influential contributors to computer science of all time.  Unfortunately, most of the time I hear his name, I cringe.  This is because it’s typically somebody quoting a small portion of one of his famous statements on optimization: “premature optimization is the root of all evil.” I mention that this is only a portion of the entire quote, and, as such, I feel that Knuth is being quoted out of context.  Optimization is important.  It is a critical part of every software development effort, and should never be ignored.  A developer who ignores optimization is not a professional.  Every developer should understand optimization – know what to optimize, when to optimize it, and how to think about code in a way that is intelligent and productive from day one. I want to start by discussing my own, personal motivation here.  I recently wrote about a performance issue I ran across, and was slammed by multiple comments and emails that effectively boiled down to: “You’re an idiot.  Premature optimization is the root of all evil.  This doesn’t matter.”  It didn’t matter that I discovered this while measuring in a profiler, and that it was a portion of my code base that can take “many hours to complete.”  Even so, multiple people instantly jump to “it’s premature – it doesn’t matter.” This is a common thread I see.  For example, StackOverflow has many pages of posts with answers that boil down to (mis)quoting Knuth.  In fact, just about any question relating to a performance related issue gets this quote thrown at it immediately – whether it deserves it or not.  That being said, I did receive some positive comments and emails as well.  Many people want to understand how to optimize their code, approaches to take, tools and techniques they can use, and any other advice they can discover. First, lets get back to Knuth – I mentioned before that Knuth is being quoted out of context.  Lets start by looking at the entire quote from his 1974 paper Structured Programming with go to Statements: “We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified.” Ironically, if you read Knuth’s original paper, this statement was made in the middle of a discussion of how Knuth himself had changed how he approaches optimization.  It was never a statement saying “don’t optimize”, but rather, “optimizing intelligently provides huge advantages.”  His approach had three benefits: “a) it doesn’t take long” … “b) the payoff is real”, c) you can “be less efficient in the other parts of my programs, which therefore are more readable and more easily written and debugged.” Looking at Knuth’s premise here, and reading that section of his paper, really leads to a few observations: Optimization is important  “he will be wise to look carefully at the critical code” Normally, 3% of your code – three lines out of every 100 you write, are “critical code” and will require some optimization: “we should not pass up our opportunities in that critical 3%” Optimization, if done well, should not be time consuming: “it doesn’t take long” Optimization, if done correctly, provides real benefits: “the payoff is real” None of this is new information.  People who care about optimization have been discussing this for years – for example, Rico Mariani’s Designing For Performance (a fantastic article) discusses many of the same issues very intelligently. That being said, many developers seem unable or unwilling to consider optimization.  Many others don’t seem to know where to start.  As such, I’m going to spend some time writing about optimization – what is it, how should we think about it, and what can we do to improve our own code.

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  • Title Tag Optimization For SEO - (Search Engine Optimization)

    In this article we have discussed the importance of the title tag in search engine optimization and further we have discussed important techniques for the title tag optimization that can get good results for search engine optimization. Title tag optimization can play a dramatic role in increasing the ranking of a web page in search engine results pages.

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  • Benchmark for website speed optimization

    - by gowri
    I working on website speed optimization. I mostly used 3 tools for analyzing speed of optimization. Speed analyzing Tools: Google pagespeed tool Yslow Firefox extenstion Web Page Performance Test I am measuring performance using above tool and benchmark result as below like before and after. Before optimization : Google PageSpeed Insights score : 53/100 Web Page Performance Test : 55/100 (First View : 10.710s, Repeat view : 6.387s ) Yahoo Overall performance score : 68 Stage 1 After optimization : Google PageSpeed Insights score : 88/100 Web Page Performance Test : 88/100 (First View : 6.733s, Repeat view : 1.908s ) Yahoo Overall performance score : 80 My question is ? Am i doing correct way ? What is the best way of benchmark for speed optimization ? Is there any standard ? Is there any much better tool for analyzing speed ?

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  • Converting convex hull to binary mask

    - by Jonas
    I want to generate a binary mask that has ones for all pixels inside and zeros for all pixels outside a volume. The volume is defined by the convex hull around a set of 3D coordinates (<100; some of the coordinates are inside the volume). I can get the convex hull using CONVHULLN, but how do I convert that into a binary mask? In case there is no good way to go via the convex hull, do you have any other idea how I could create the binary mask?

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  • Best open source Mixed Integer Optimization Solver

    - by Mark
    I am using CPLEX for solving huge optimization models (more than 100k variables) now I'd like to see if I can find an open source alternative, I solve mixed integer problems (MILP) and CPLEX works great but it is very expensive if we want to scale so I really need to find an alternative or start writing our own ad-hoc optimization library (which will be painful) Any suggestion/insight would be much appreciated

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  • Keywords Optimization For Website Optimization

    Saying that you need to do website optimization sounds like saying you need to get healthy. To get healthy we do 2 things: diet management and exercise. Lets start with diet management. Keywords are like food for your WebPages. This article explains the role of keywords in website optimization.

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  • Can compiler optimization introduce bugs ?

    - by ereOn
    Hi, Today I had a discussion with a friend of mine and we debated for a couple of hours about "compiler optimization". I defended the point that sometimes, a compiler optimization might introduce bugs or at least, undesired behavior. My friend totally disagreed, saying that "compiler are built by smart people and do smart things" and thus, can never go wrong. He didn't convinced my at all, but I have to admit I lack of real-life examples to strengthen my point. Who is right here ? If I am, do you have any real-life example where a compiler optimization produced a bug in the resulting software ? If I'm mistaking, should I stop programming and learn fishing instead ? Thank you !

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  • Java2D: Fill a convex rounded polygon (QuadCurves)

    - by Martijn Courteaux
    Hi, If I have a QuadCurve like this (+ = node): + + \ ./ +--?? And I fill it in Java 2D the result is something like this: (x = colored) +xxxxxxxxx+ \xxxxxx./ +--?? But I want to color the other side: + + x\ ./x xxx +--??xx xxxxxxxxxxx This succeeds by drawing a rectangle around the curve in the color I want to color the other side and then fill the curve with the background color. But this isn't good enough to fill a convex rounded (based on QuadCurves) polygon. In case of some coordinates for the rectangles (as explained in the trick I used) overlap other pieces of the polygon. Here are two images (the green area is my polygon): So, the question is simple: "How can I color a shape build of curves?" But to the answer will not be simple I think... Any advice would be VERY VERY appreciated. Thanks in advance. Maybe I'm going to make a bounty for this question if I don't get an answer

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  • Search Engine Optimization (SEO) Tips - Code Optimization

    Code optimization is a very important in making your website Search Engine Friendly. A webpage is called Search Engine Friendly when it is coded in such a way that search engines can read and understand it to the maximum. For making your Webpage Search Engine Friendly you have to keep the following factors in mind and code accordingly.

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  • Collision detection of convex shapes on voxel terrain

    - by Dave
    I have some standard convex shapes (cubes, capsules) on a voxel terrain. It is very easy to detect single vertex collisions. However, it becomes computationally expensive when many vertices are involved. To clarify, currently my algorithm represents a cube as multiple vertices covering every face of the cube, not just the corners. This is because the cubes can be much bigger than the voxels, so multiple sample points (vertices) are required (the distance between sample points must be at least the width of a voxel). This very rapidly becomes intractable. It would be great if there were some standard algorithm(s) for collision detection between convex shapes and arbitrary voxel based terrain (like there is with OBB's and seperating axis theorem etc). Any help much appreciated.

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  • Find vertices of a convex hull

    - by Jeff Bullard
    I am attempting to do this within CGAL. From a 3D point cloud, find the convex hull, then loop over the finite facets of the convex hull and print each facet's vertices. It seems like there should be a straightforward way to do this; I would have expected that 3D polyhedra would own a vector of facet objects, each of which in turn would own a vector of its edges, each of which in turn would own a vector of its vertices, and that their would be some access through this hierarchy using iterators. But so far I have been unable to find a simple way to navigate through this hierarchy (if it exists).

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  • The Expert Secret to Search Engine Optimization - Effective Website Optimization

    Throwing keywords into a program that shows you how popular they are and then using those keywords without doing a little bit of preliminary research and answering some very important questions can just spell disaster. There are three questions that are extremely important to ask yourself before just doing random search engine optimization. And believe it or not those three questions are not, "What are the most popular keywords for my particular website?" Those questions are much more fundamental and strategic and they can be much more important to your overall efforts in getting your site ranked on the search engines.

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  • Search Engine Optimization - How Search Engine Optimization Works

    There are many ways to direct extra traffic to your web site, but search engine optimization may be the best. Unlike many traditional types of advertising, such as banner ads, this technique does not cast a wide net and hope for the best. Instead, it takes the opposite approach, simply making your site easier to find for people who are looking for a site that is similar to it. This is a much more reliable method of gaining additional viewers for your site, especially because it only targets people who are interested in you in the first place.

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  • SQLAuthority News – Microsoft SQL Server 2005/2008 Query Optimization & Performance Tuning Training

    - by pinaldave
    Last 3 days to register for the courses. This is one time offer with big discount. The deadline for the course registration is 5th May, 2010. There are two different courses are offered by Solid Quality Mentors 1) Microsoft SQL Server 2005/2008 Query Optimization & Performance Tuning – Pinal Dave Date: May 12-14, 2010 Price: Rs. 14,000/person for 3 days Discount Code: ‘SQLAuthority.com’ Effective Price: Rs. 11,000/person for 3 days 2) SharePoint 2010 – Joy Rathnayake Date: May 10-11, 2010 Price: Rs. 11,000/person for 3 days Discount Code: ‘SQLAuthority.com’ Effective Price: Rs. 8,000/person for 2 days Download the complete PDF brochure. To register, either send an email to [email protected] or call +91 95940 43399. Feel free to drop me an email at pinal “at” SQLAuthority.com for any additional information and clarification. Training Venue: Abridge Solutions, #90/B/C/3/1, Ganesh GHR & MSY Plaza, Vittalrao Nagar, Near Image Hospital, Madhapur, Hyderabad – 500 081. Additionally there is special program of SolidQ India Insider. This is only available to first few registrants of the courses only. Read more details about the course here. Read my TechEd India 2010 experience here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, SQLAuthority News, T SQL, Technology

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  • What is the best retort to "premature optimization is the root of all evil"

    - by waffles
    Often I hear the sentiment ... "Why worry about performance, write slow code, get your product to market ... don't worry about performance. You can sort that out later" The culmination of this sentiment is: "... premature optimization is the root of all evil ... #winning" I was wondering, does anybody have a good retort to this one liner. Ideally an equally strong one liner that encompasses the reverse of this sentiment?

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  • Web page database query optimization

    - by morpheous
    I am putting together a web page which is quite 'expensive' in terms of database hits. I don't want to start optimizing at this stage - though with me trying to hit a deadline, I may end up not optimizing at all. Currently the page requires 18 (that's right eighteen) hits to the db. I am already using joins, and some of the queries are UNIONed to minimize the trips to the db. My local dev machine can handle this (page is not slow) however, I feel if I release this into the wild, the number of queries will quickly overwhelm my database (MySQL). I could always use memcache or something similar, but I would much rather continue with my other dev work that needs to be completed before the deadline - at least retrieving the page works - its simply a matter of optimization now (if required). My question therefore is - is 18 db queries for a single page retrieval completely outrageous - (i.e. I should put everything on hold and optimize the hell of the retrieval logic), or shall I continue as normal, meet the deadline and release on schedule and see what happens? [Edit] Just to clarify, I have already done the 'obvious' things like using (single and composite) indexes for fields used in the queries. What I haven't yet done is to run a query analyzer to see if my indexes etc are optimal.

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  • Why would this Lua optimization hack help?

    - by Ian Boyd
    i'm looking over a document that describes various techniques to improve performance of Lua script code, and i'm shocked that such tricks would be required. (Although i'm quoting Lua, i've seen similar hacks in Javascript). Why would this optimization be required: For instance, the code for i = 1, 1000000 do local x = math.sin(i) end runs 30% slower than this one: local sin = math.sin for i = 1, 1000000 do local x = sin(i) end They're re-declaring sin function locally. Why would this be helpful? It's the job of the compiler to do that anyway. Why is the programmer having to do the compiler's job? i've seen similar things in Javascript; and so obviously there must be a very good reason why the interpreting compiler isn't doing its job. What is it? i see it repeatedly in the Lua environment i'm fiddling in; people redeclaring variables as local: local strfind = strfind local strlen = strlen local gsub = gsub local pairs = pairs local ipairs = ipairs local type = type local tinsert = tinsert local tremove = tremove local unpack = unpack local max = max local min = min local floor = floor local ceil = ceil local loadstring = loadstring local tostring = tostring local setmetatable = setmetatable local getmetatable = getmetatable local format = format local sin = math.sin What is going on here that people have to do the work of the compiler? Is the compiler confused by how to find format? Why is this an issue that a programmer has to deal with? Why would this not have been taken care of in 1993? i also seem to have hit a logical paradox: Optimizatin should not be done without profiling Lua has no ability to be profiled Lua should not be optimized

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  • Optimization of time-varying parameters

    - by brama
    I need to find an optimal set of "n" parameter values that minimize an objective function (a 2-hr simulation of a system). I have looked at genetic algorithm and simulated annealing methods, but was wondering if there are any better algorithms and guidance on their merits and limitations. With the above optimization methods I can find the optimal parameter values that hold true for the entire simulation duration. Incase, I want to find the optimal "time varying" parameter values (parameter values change with time during the 2-hr simulation), are there any methods/ideas other than making each time varying parameter value a variable to optimize? Any thoughts?

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