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• Why do spammers use CELESTRON NEXTAR 6SE?

  - by fmz

  I am running a website for a volunteer organization that hosts an annual event. There is a form where people can volunteer to bring items for the event. All too frequently I get spam from users across the globe that enter things like this: Country - 1: Australia Material - 1: CELESTRON NEXTAR 6SE Country - 2: Australia Material - 2: C8 Newton Country - 3: Australia Material - 3: ETX 125EC Country - 4: Australia Material - 4: ETX 125EC Country - 5: Australia Material - 5: CELESTRON NEXTAR 6SE I don't really care about the country, but what is it with the telescope stuff? Is there some hidden meaning behind all this or is it some astronomy group that moonlights as spammers?

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• What is realism?

  - by eversor

  Beyond the obvious something that seams real, realism in games is a hard feature to hit. In some cases, things that are completely impossible in real life are seen as realistic by gamers. For instance, in some FPS you can survive being hit by a fair amount of bullets when in real life one is enough, Newton-defying car drifts, etc. So, in some cases, reductions of life-like actions or consequences implies a bigger sense of realism. The root of this pseudo-philosophical question lies in: I am going to create a engine for battles in an online (browser-based) strategic game. Browser-based means that the battle would not be seen. And i do not know how to approach this realism issue.

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• What are your most useful C# extension methods?

  - by Edward Tanguay

  Extension methods continually make the C# I work with more readable and intuitive to program. I want to collect useful extension methods into a library so I always have them, such FormatWith by James Newton-King. What are the most useful extension methods that you use?

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• Bracketing algorithm when root finding. Single root in "quadratic" function

  - by Ander Biguri

  I am trying to implement a root finding algorithm. I am using the hybrid Newton-Raphson algorithm found in numerical recipes that works pretty nicely. But I have a problem in bracketing the root. While implementing the root finding algorithm I realised that in several cases my functions have 1 real root and all the other imaginary (several of them, usually 6 or 9). The only root I am interested is in the real one so the problem is not there. The thing is that the function approaches the root like a cubic function, touching with the point the y=0 axis... Newton-Rapson method needs some brackets of different sign and all the bracketing methods I found don't work for this specific case. What can I do? It is pretty important to find that root in my program... EDIT: more problems: sometimes due to reaaaaaally small numerical errors, say a variation of 1e-6 in some value the "cubic" function does NOT have that real root, it is just imaginary with a neglectable imaginary part... (checked with matlab) EDIT 2: Much more information about the problem. Ok, I need root finding algorithm. Info I have: The root I need to find is between [0-1] , if there are more roots outside that part I am not interested in them. The root is real, there may be imaginary roots, but I don't want them. Probably all the rest of the roots will be imaginary The root may be double in that point, but I think that actually doesn't mater in numerical analysis problems I need to use the root finding algorithm several times during the overall calculations, but the function will always be a polynomial In one of the particular cases of the root finding, my polynomial will be similar to a quadratic function that touches Y=0 with the point. Example of a real case: The coefficient may not be 100% precise and that really slight imprecision may make the function not to touch the Y=0 axis. I cannot solve for this specific case because in other cases it may be that the polynomial is pretty normal and doesn't make any "strange" thing. The method I am actually using is NewtonRaphson hybrid, where if the derivative is really small it makes a bisection instead of NewRaph (found in numerical recipes). Matlab's answer to the function on the image: roots: 0.853553390593276 + 0.353553390593278i 0.853553390593276 - 0.353553390593278i 0.146446609406726 + 0.353553390593273i 0.146446609406726 - 0.353553390593273i 0.499999999999996 + 0.000000040142134i 0.499999999999996 - 0.000000040142134i The function is a real example I prepared where I know that the answer I want is 0.5 Note: I still haven't check completely some of the answers I you people have give me (Thank you!), I am just trying to give al the information I already have to complete the question.

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• Indexing with pointer C/C++

  - by Leavenotrace

  Hey I'm trying to write a program to carry out newtons method and find the roots of the equation exp(-x)-(x^2)+3. It works in so far as finding the root, but I also want it to print out the root after each iteration but I can't get it to work, Could anyone point out my mistake I think its something to do with my indexing? Thanks a million :) #include <stdio.h> #include <math.h> #include <malloc.h> //Define Functions: double evalf(double x) { double answer=exp(-x)-(x*x)+3; return(answer); } double evalfprime(double x) { double answer=-exp(-x)-2*x; return(answer); } double *newton(double initialrt,double accuracy,double *data) { double root[102]; data=root; int maxit = 0; root[0] = initialrt; for (int i=1;i<102;i++) { *(data+i)=*(data+i-1)-evalf(*(data+i-1))/evalfprime(*(data+i-1)); if(fabs(*(data+i)-*(data+i-1))<accuracy) { maxit=i; break; } maxit=i; } if((maxit+1==102)&&(fabs(*(data+maxit)-*(data+maxit-1))>accuracy)) { printf("\nMax iteration reached, method terminated"); } else { printf("\nMethod successful"); printf("\nNumber of iterations: %d\nRoot Estimate: %lf\n",maxit+1,*(data+maxit)); } return(data); } int main() { double root,accuracy; double *data=(double*)malloc(sizeof(double)*102); printf("NEWTONS METHOD PROGRAMME:\nEquation: f(x)=exp(-x)-x^2+3=0\nMax No iterations=100\n\nEnter initial root estimate\n>> "); scanf("%lf",&root); _flushall(); printf("\nEnter accuracy required:\n>>"); scanf("%lf",&accuracy); *data= *newton(root,accuracy,data); printf("Iteration Root Error\n "); printf("%d %lf \n", 0,*(data)); for(int i=1;i<102;i++) { printf("%d %5.5lf %5.5lf\n", i,*(data+i),*(data+i)-*(data+i-1)); if(*(data+i*sizeof(double))-*(data+i*sizeof(double)-1)==0) { break; } } getchar(); getchar(); free(data); return(0); }

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• Elliptical orbit modeling

  - by Nathon

  I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every frame as appropriate given Newton's law of universal gravitation. The point masses don't move (there's only 1 right now) so I would expect an elliptical orbit. Instead, I see this: I've tried with nearly circular orbits, and I've tried making the masses vastly different (a factor of a million) but I always get this rotated orbit. Here's some (D) code, for context: void accelerate(Vector delta) { velocity = velocity + delta; // Velocity is a member of the ship class. } // This function is called every frame with the fixed mass. It's a // method of the ship's. void fall(Well well) { // f=(m1 * m2)/(r**2) // a=f/m // Ship mass is 1, so a = f. float mass = 1; Vector delta = well.position - loc; float rSquared = delta.magSquared; float force = well.mass/rSquared; accelerate(delta * force * mass); }

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• PhysX for massive performance via GPU ?

  - by devdude

  I recently compared some of the physics engine out there for simulation and game development. Some are free, some are opensource, some are commercial (1 is even very commercial $$$$). Havok, Ode, Newton (aka oxNewton), Bullet, PhysX and "raw" build-in physics in some 3D engines. At some stage I came to conclusion or question: Why should I use anything but NVidia PhysX if I can make use of its amazing performance (if I need it) due to GPU processing ? With future NVidia cards I can expect further improvement independent of the regular CPU generation steps. The SDK is free and it is available for Linux as well. Of course it is a bit of vendor lock-in and it is not opensource. Whats your view or experience ? If you would start right now with development, would you agree with the above ? cheers

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• HTML is not being interpreted after JQuery's .ajax function

  - by Casidiablo

  Hello there... Once I have retrived an HTML string with the $.ajax function I put it into a div... the HTML is a simple message with a <b> tag, but it's not being interpreted by the browser, I mean, the <b> is not making the text bold. Here is what I do: $.ajax({ url: 'index.php?ajax=ejecutar_configuracion&id_gadget=cubrimientos', cache: false, success: function(html){ // html = '<b>hello</b> newton' $('#config_reporte').html(html).dialog({ height: 300, width: 500, modal: true }); } }); As you can see, I'm writing the content of the HTML result into a modal dialog window. Does anybody know why is this happening? This should be something easy to do... but I haven't been able to make it work properly. Thank you so much.

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• PagedDataSource does not support serialization - how can I enforce this ?

  - by Darkyo

  Sounds like I want to override a physics law, but at least it is the most reasonnable solution, cpu / HDD and Ram effective for my asp.net project. In fact, I got a pageddataSource and a customDataReader that supports paginated data. The truth is my data are in a viewstate variable, because it is re-used in an update panel. When I intend to use it into my pageddatasource, asp.net 3.5 kills me with a System.Web.UI.WebControls.PagedDataSource' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable. cool exception... So I'd rather not offend newton because I know he'll always win, but I would need some help to enforce this pagedDataSource law, that seems so unbelievable, except if someone has an explanation.

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• Dynamic creation of a pointer function in c++

  - by Liberalkid

  I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?

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• WebCenter Customer Spotlight: Fundação Petrobras de Seguridade Social

  - by me

  Author: Peter Reiser - Social Business Evangelist, Oracle WebCenter Solution Summary Fundação Petrobras de Seguridade Social (PetroS) is a Brazilian nonprofit organization pension fund serving 152 private companies with more then 145,000 plan participants and  managing a portfolio of  US$35.9 billion in equity. PetroS business objective was to implement a robust and flexible online solution to enable the foundation to successfully compete in the pension marketplace. PetroS implemented a robust, flexible and highly available database solution based on Oracle Database 11g, Enterprise Edition and modernized the company’s Web portal using Oracle WebCenter Suite.  The solution enables PetroS to make an average of 5,000 online loans per month to its 110,000 qualifying participants and supports 2,000 online consultations daily. Company ProfileFundação Petrobras de Seguridade Social (Petrobras Social Security Foundation)—better known as PetroS—is a pension fund founded in the 1970s to pay supplementary retirement benefits to Petrobras employees. Later, the foundation expanded its market to include 152 private companies, including Sanasa, Repsol YPF and Alesat. The Foundation, a nonprofit organization, has more than 145,000 plan participants, US$35.9 billion in equity, and a loan portfolio of US$730 million. Business ChallengesPetroS business objectives were to implement a robust and flexible solution to enable the foundation to successfully compete in the pension marketplace without affecting its monthly payments to 60,000 beneficiaries and to extend service delivery through the Web to better serve the fund’s more than 145,000 participants. Solution DeployedPetroS worked with Oracle Consulting to implement a robust, flexible and high available database solution based on Oracle Database 11g, Enterprise Edition and modernized the company’s Web portal using Oracle WebCenter Suite, enabling PetroS to deliver more flexible services to pension plan participants. Business ResultsThe solution enables PetroS to make an average of 5,000 online loans per month to its 110,000 qualifying participants and supports 2,000 online consultations daily. “The combination of Oracle Database 11g and Oracle WebCenter Suite has helped us deliver faster and better service for over 130,000 clients who participate in the 96 supplementary pension plans we currently offer. It has certainly helped to fuel our growth.” Newton Carneiro da Cunha, Diretor Administrativo, Fundação Petrobrás de Seguridade Social           Additional Information PetroS Customer Snapshot Oracle WebCenter Suite Oracle Database 11g, Enterprise Edition Oracle Real Application Clusters Oracle Diagnostics Pack Oracle Tuning Pack Oracle Consulting

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• maximum number of connections Squid

  - by Isaac

  I have a Squid proxy server that controls all internet traffic for my network. I need a way to stop users from downloading big files (say 50MB) in my network. I banned some famous ports (e.g. torrent) but some downloads are possible by HTTP port. Obviously I cannot ban port 80! A simple solution is limiting maxmimum number of the simultaneous connections for each IP (e.g. 3 connections). It's possible in Squid with this config: acl ACCOUNTSDEPT 192.168.5.0/24 acl limitusercon maxconn 3 http_access deny ACCOUNTSDEPT limitusercon But this solution has really bad impact in web browsing, because any smart browser get different parts of a website by several connections simultaneously to speedup web browsing. But if we have a maximum number of connections, the browsers will fail to get some parts and the website will be shown partially and some parts/images/frames will not be shown. So, can we limit maximum number of persist connections? I think this policy will works: Specify Maximum number of connections that is alive for 10 seconds But Number of simultaneous connections for every IP is unlimited But how can we implement this policy when Squid? With which config? UPDATE: artifex and Tom Newton offered using a bandwidth-limiting approach to fight against downloaders. But bandwidth-limiting in Squid has a shortcoming: It's static and cannot dynamically change. So a person has a limited bandwidth not matter how many people are using internet (maybe nobody!) Also, this solution cannot help to stop people from downloading. They still can download but in a lower speed. But if we find a way to terminate persist connections (or any connection that is alive more than a specific time), downloading big files will be almost impossible (always there is some way!)

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• F# in ASP.NET, mathematics and testing

  - by DigiMortal

  Starting from Visual Studio 2010 F# is full member of .NET Framework languages family. It is functional language with syntax specific to functional languages but I think it is time for us also notice and study functional languages. In this posting I will show you some examples about cool things other people have done using F#. F# and ASP.NET As I am ASP/ASP.NET MVP I am – of course – interested in how people use different languages and technologies with ASP.NET. C# MVP Tomáš Petrícek writes about developing ASP.NET MVC applications using F#. He also shows how to use LINQ To SQL in F# (using F# PowerPack) and provides sample solution and Visual Studio 2010 template for F# MVC web applications. You may also find interesting how you can create controllers in F#. Excellent work, Tomáš! Vladimir Matveev has interesting example about how to use F# and ApplicationHost class to process ASP.NET requests ouside of IIS. This is simple and very straight-forward example and I strongly suggest you to take a look at it. Very cool example is project Strom in Codeplex. Storm is web services testing tool that is fully written on F#. Take a look at this site because Codeplex offers also source code besides binaries. Math Functional languages are strong in fields like mathematics and physics. When I wrote my C# example about BigInteger class I found out that recursive version of Fibonacci algorithm in C# is not performing well. In same time I made same experiment on F# and in F# there were no performance problems with recursive version. You can find F# version of Fibonacci algorithm from Bob Palmer’s blog posting Fibonacci numbers in F#. Although golden spiral is useful for solving many problems I looked for some practical code example and found one. Kean Walmsley published in his Through the Interface blog very interesting posting Creating Fibonacci spirals in AutoCAD using F#. There are also other cool examples you may be interested in. Using numerical components by Extreme Optimization  it is possible to make some numerical integration (quadrature method) using F# (also C# example is available). fsharp.it introduces factorials calculation on F#. Robert Pickering has made very good work on programming The Game of Life in Silverlight and F# – I definitely suggest you to try out this example as it is very illustrative too. Who wants something more complex may take a look at Newton basin fractal example in F# by Jonathan Birge. Testing After some searching and surfing I found out that there is almost everything available for F# to write tests and test your F# code. FsCheck - FsCheck is a port of Haskell's QuickCheck. Important parts of the manual for using FsCheck is almost literally "adapted" from the QuickCheck manual and paper. Any errors and omissions are entirely my responsibility. FsTest - This project is designed to Language Oriented Programming constructs around unit testing and behavior testing in F#. The goal of this project is to create a Domain Specific Language for testing F# code in a way that makes sense for functional programming. FsUnit - FsUnit makes unit-testing with F# more enjoyable. It adds a special syntax to your favorite .NET testing framework. xUnit.NET - xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.0 and later, and offers several runners: console, GUI, MSBuild, and Visual Studio integration via TestDriven.net, CodeRush Test Runner and Resharper. It also offers test project integration for ASP.NET MVC. Getting started Well, as a first thing you need Visual Studio 2010. Then take a look at these resources: F# samples @ MSDN Microsoft F# Developer Center @ MSDN F# Language Reference @ MSDN F# blog F# forums Real World Functional Programming: With Examples in F# and C# (Amazon) Happy F#-ing! :)

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• The Oracle Retail Week Awards - most exciting awards yet?

  - by sarah.taylor(at)oracle.com

  Last night's annual Oracle Retail Week Awards saw the UK's top retailers come together to celebrate the very best of our industry over the last year.  The Grosvenor House Hotel on Park Lane in London was the setting for an exciting ceremony which this year marked several significant milestones in British - and global - retail.  Check out our videos about the event at our Oracle Retail YouTube channel, and see if you were snapped by our photographer on our Oracle Retail Facebook page. There were some extremely hot contests for many of this year's awards - and all very deserving winners.  The entries have demonstrated beyond doubt that retailers have striven to push their standards up yet again in all areas over the past year.  The judging panel includes some of the most prestigious names in the retail industry - to impress the panel enough to win an award is a substantial achievement.  This year the panel included the likes of Andy Clarke - Chief Executive of ASDA Group; Mark Newton Jones - CEO of Shop Direct Group; Richard Pennycook - the finance director at Morrisons; Rob Templeman - Chief Executive of Debenhams; and Stephen Sunnucks - the president of Gap Europe.  These are retail veterans  who have each helped to shape the British High Street over the last decade.  It was great to chat with many of them in the Oracle VIP area last night.  For me, last night's highlight was honouring both Sir Stuart Rose and Sir Terry Leahy for their contributions to the retail industry.  Both have set the standards in retailing over the last twenty years and taken their respective businesses from strength to strength, demonstrating that there is always a need for innovation even in larger businesses, and that a business has to adapt quickly to new technology in order to stay competitive.  Sir Terry Leahy's retirement this year marks the end of an era of global expansion for the Tesco group and a milestone in the progression of British retail.  Sir Terry has helped steer Tesco through nearly 20 years of change, with 14 years as Chief Executive.  During this time he led the drive for international expansion and an aggressive campaign to increase market share.  He has led the way for High Street retailers in adapting to the rise of internet retailing and nurtured a very successful home delivery service.  More recently he has pioneered the notion of cross-channel retailing with the introduction of Tesco apps for the iPhone and Android mobile phones allowing customers to scan barcodes of items to add to a shopping list which they can then either refer to in store or order for delivery.  John Lewis Partnership was a very deserving winner of The Oracle Retailer of the Year award for their overall dedication to excellent retailing practices.  The business was also named the American Express Marketing/Advertising Campaign of the Year award for their memorable 'Never Knowingly Undersold' advert series, which included a very successful viral video and radio campaign with Fyfe Dangerfield's cover of Billy Joel's 'She's Always a Woman' used for the adverts.  Store Design of the Year was another exciting category with Topshop taking the accolade for its flagship Oxford Street store in London, which combines boutique concession-style stalls with high fashion displays and exclusive collections from leading designers.  The store even has its own hairdressers and food hall, making it a truly all-inclusive fashion retail experience and a global landmark for any self-respecting international fashion shopper. Over the next few weeks we'll be exploring some of the winning entries in more detail here on the blog, so keep an eye out for some unique insights into how the winning retailers have made such remarkable achievements. 

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• SQL SERVER – Quiz and Video – Introduction to Hierarchical Query using a Recursive CTE

  - by pinaldave

  This blog post is inspired from SQL Queries Joes 2 Pros: SQL Query Techniques For Microsoft SQL Server 2008 – SQL Exam Prep Series 70-433 – Volume 2.[Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to Hierarchical Query using a Recursive CTE – A Primer. In the article we discussed various basics terminology of the CTE. The article further covers following important concepts of common table expression. What is a Common Table Expression (CTE) Building a Recursive CTE Identify the Anchor and Recursive Query Add the Anchor and Recursive query to a CTE Add an expression to track hierarchical level Add a self-referencing INNER JOIN statement Above six are the most important concepts related to CTE and SQL Server.  There are many more things one has to learn but without beginners fundamentals one can’t learn the advanced  concepts. Let us have small quiz and check how many of you get the fundamentals right. Quiz 1) You have an employee table with the following data. EmpID FirstName LastName MgrID 1 David Kennson 11 2 Eric Bender 11 3 Lisa Kendall 4 4 David Lonning 11 5 John Marshbank 4 6 James Newton 3 7 Sally Smith NULL You need to write a recursive CTE that shows the EmpID, FirstName, LastName, MgrID, and employee level. The CEO should be listed at Level 1. All people who work for the CEO will be listed at Level 2. All of the people who work for those people will be listed at Level 3. Which CTE code will achieve this result? WITH EmpList AS (SELECT Boss.EmpID, Boss.FName, Boss.LName, Boss.MgrID, 1 AS Lvl FROM Employee AS Boss WHERE Boss.MgrID IS NULL UNION ALL SELECT E.EmpID, E.FirstName, E.LastName, E.MgrID, EmpList.Lvl + 1 FROM Employee AS E INNER JOIN EmpList ON E.MgrID = EmpList.EmpID) SELECT * FROM EmpList WITH EmpListAS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID IS NULL UNION ALL SELECT EmpID, FirstName, LastName, MgrID, 2 as Lvl ) SELECT * FROM BossList WITH EmpList AS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID is NOT NULL UNION SELECT EmpID, FirstName, LastName, MgrID, BossList.Lvl + 1 FROM Employee INNER JOIN EmpList BossList ON Employee.MgrID = BossList.EmpID) SELECT * FROM EmpList 2) You have a table named Employee. The EmployeeID of each employee’s manager is in the ManagerID column. You need to write a recursive query that produces a list of employees and their manager. The query must also include the employee’s level in the hierarchy. You write the following code segment: WITH EmployeeList (EmployeeID, FullName, ManagerName, Level) AS ( –PICK ANSWER CODE HERE ) SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName mgr.FullName, 1 + 1 AS [Level] FROM Employee emp JOIN Employee mgr ON emp.ManagerID = mgr.EmployeeId SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName, mgr.FullName, mgr.Level + 1 FROM EmployeeList mgr JOIN Employee emp ON emp.ManagerID = mgr.EmployeeId Now make sure that you write down all the answers on the piece of paper. Watch following video and read earlier article over here. If you want to change the answer you still have chance. Solution 1) 1 2) 2 Now compare let us check the answers and compare your answers to following answers. I am very confident you will get them correct. Available at USA: Amazon India: Flipkart | IndiaPlaza Volume: 1, 2, 3, 4, 5 Please leave your feedback in the comment area for the quiz and video. Did you know all the answers of the quiz? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Investigating Strategies For Functional Decomposition

  - by Liam McLennan

  Introducing Functional Decomposition Before I begin I must apologise. I think I am using the term ‘functional decomposition’ loosely, and probably incorrectly. For the purpose of this article I use functional decomposition to mean the recursive splitting of a large problem into increasingly smaller ones, so that the one large problem may be solved by solving a set of smaller problems. The justification for functional decomposition is that the decomposed problem is more easily solved. As software developers we recognise that the smaller pieces are more easily tested, since they do less and are more cohesive. Functional decomposition is important to all scientific pursuits. Once we understand natural selection we can start to look for humanities ancestral species, once we understand the big bang we can trace our expanding universe back to its origin. Isaac Newton acknowledged the compositional nature of his scientific achievements: If I have seen further than others, it is by standing upon the shoulders of giants   The Two Strategies For Functional Decomposition of Computer Programs Private Methods When I was working on my undergraduate degree I was taught to functionally decompose problems by using private methods. Consider the problem of painting a house. The obvious solution is to solve the problem as a single unit: public void PaintAHouse() { // all the things required to paint a house ... } We decompose the problem by breaking it into parts: public void PaintAHouse() { PaintUndercoat(); PaintTopcoat(); } private void PaintUndercoat() { // everything required to paint the undercoat } private void PaintTopcoat() { // everything required to paint the topcoat } The problem can be recursively decomposed until a sufficiently granular level of detail is reached: public void PaintAHouse() { PaintUndercoat(); PaintTopcoat(); } private void PaintUndercoat() { prepareSurface(); fetchUndercoat(); paintUndercoat(); } private void PaintTopcoat() { fetchPaint(); paintTopcoat(); } According to Wikipedia, at least one computer programmer has referred to this process as “the art of subroutining”. The practical issues that I have encountered when using private methods for decomposition are: To preserve the top level API all of the steps must be private. This means that they can’t easily be tested. The private methods often have little cohesion except that they form part of the same solution. Decomposing to Classes The alternative is to decompose large problems into multiple classes, effectively using a class instead of each private method. The API delegates to related classes, so the API is not polluted by the sub-steps of the problem, and the steps can be easily tested because they are each in their own highly cohesive class. Additionally, I think that this technique facilitates better adherence to the Single Responsibility Principle, since each class can be decomposed until it has precisely one responsibility. Revisiting my previous example using class composition: public class HousePainter { private undercoatPainter = new UndercoatPainter(); private topcoatPainter = new TopcoatPainter(); public void PaintAHouse() { undercoatPainter.Paint(); topcoatPainter.Paint(); } } Summary When decomposing a problem there is more than one way to represent the sub-problems. Using private methods keeps the logic in one place and prevents a proliferation of classes (thereby following the four rules of simple design) but the class decomposition is more easily testable and more compatible with the Single Responsibility Principle.

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• How do people know so much about programming?

  - by Luciano

  I see people in this forums with a lot of points, so I assume they know about a lot of different programming stuff. When I was young I knew about basic (commodore) and the turbo pascal (pc). Then in college I learnt about C, memory management, x86 set, loop invariants, graphs, db query optimization, oop, functional, lambda calculus, prolog, concurrency, polymorphism, newton method, simplex, backtracking, dynamic programming, heuristics, np completeness, LR, LALR, neural networks, static & dynamic typing, turing, godel, and more in between. Then in industry I started with Java several years ago and learnt about it, and its variety of frameworks, and also design patterns, architecture patterns, web development, server development, mobile development, tdd, bdd, uml, use cases, bug trackers, process management, people management if you are a tech lead, profiling, security concerns, etc. I started to forget what I learnt in college... And then there is the stuff I don't know yet, like python, .net, perl, JVM stuff like groovy or scala.. Of course Google is a must for rapid documentation access to know if a problem has been solved already and how, and to keep informed about new stuff by blogs and places like this one. It's just too much or I just have a bad memory.. how do you guys manage it?

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• JAXB Annotated class - setting of a variable which is not an element

  - by sswdeveloper

  I have a JAXB annotated class say @XmlRootElement(namespace = "http://www.abc.com/customer") Class Customer{ @XmlElement(namespace = "http://www.abc.com/customer") private String Name; @XmlElement(namespace = "http://www.abc.com/customer") private String Address; @XmlTransient private HashSet set = new HashSet(); public String getName(){ return Name; } public void setName(String name){ this.Name = name; set.add("Name"); } public String getAddress(){ return Address; } public void setAddress(String address){ this.Address = address; set.add("Address"); } public void getSet(){ return set; } I have a XML of the form <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Customer xmlns="http://www.abc.com/customer" > <Name>Ralph</Name> <Address>Newton Street</Address> </Customer> I use JAXB unmarshalling to get the object representation of the XML input. The values for Name and Address are set correctly. However the value of set gets lost(since it is @XMLTransient it gets ignored) Is there any way of ensuring that it is still set in the object which has been unmarshalled? Some other annotation which I can use?

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• Iterating through items of CompositeCollection

  - by Dudu

  Consider the code: ObservableCollection<string> cities = new ObservableCollection<string>(); ObservableCollection<string> states = new ObservableCollection<string>(); ListBox list; cities.Add("Frederick"); cities.Add("Germantown"); cities.Add("Arlington"); cities.Add("Burbank"); cities.Add("Newton"); cities.Add("Watertown"); cities.Add("Pasadena"); states.Add("Maryland"); states.Add("Virginia"); states.Add("California"); states.Add("Nevada"); states.Add("Ohio"); CompositeCollection cmpc = new CompositeCollection(); CollectionContainer cc1 = new CollectionContainer(); cc1.Collection = cities; CollectionContainer cc2 = new CollectionContainer(); cc2.Collection = states; cmpc.Add(cc1); cmpc.Add(cc2); list.ItemsSource = cmpc; foreach(var itm in cmpc ) { // itm is CollectionContainer and there are only two itm’s // I need the strings } While list shows the right data on the GUI I need this data (without referring to the ListBox) and I am not getting it

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• Using "from __future__ import division" in my program, but it isn't loaded with my program

  - by Sara Fauzia

  I wrote the following program in Python 2 to do Newton's method computations for my math problem set, and while it works perfectly, for reasons unbeknownst to me, when I initially load it in ipython with %run -i NewtonsMethodMultivariate.py, the Python 3 division is not imported. I know this because after I load my Python program, entering x**(3/4) gives "1". After manually importing the new division, then x**(3/4) remains x**(3/4), as expected. Why is this? # coding: utf-8 from __future__ import division from sympy import symbols, Matrix, zeros x, y = symbols('x y') X = Matrix([[x],[y]]) tol = 1e-3 def roots(h,a): def F(s): return h.subs({x: s[0,0], y: s[1,0]}) def D(s): return h.jacobian(X).subs({x: s[0,0], y: s[1,0]}) if F(a) == zeros(2)[:,0]: return a else: while (F(a)).norm() > tol: a = a - ((D(a))**(-1))*F(a) print a.evalf(10) I would use Python 3 to avoid this issue, but my Linux distribution only ships SymPy for Python 2. Thanks to the help anyone can provide. Also, in case anyone was wondering, I haven't yet generalized this script for nxn Jacobians, and only had to deal with 2x2 in my problem set. Additionally, I'm slicing the 2x2 zero matrix instead of using the command zeros(2,1) because SymPy 0.7.1, installed on my machine, complains that "zeros() takes exactly one argument", though the wiki suggests otherwise. Maybe this command is only for the git version.

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• Last week I was presented with a Microsoft MVP award in Virtual Machines – time to thank all who hel

  - by Liam Westley

  MVP in Virtual Machines Last week, on 1st April, I received an e-mail from Microsoft letting me know that I had been presented with a 2010 Microsoft® MVP Award for outstanding contributions in Virtual Machine technical communities during the past year.   It was an honour to be nominated, and is a great reflection on the vibrancy of the UK user group community which made this possible. Virtualisation for developers, not just IT Pros I consider it a special honour as my expertise in virtualisation is as a software developer utilising virtual machines to aid my software development, rather than an IT Pro who manages data centre and network infrastructure.  I’ve been on a minor mission over the past few years to enthuse developers in a topic usually seen as only for network admins, but which can make their life a whole lot easier once understood properly. Continuous learning is fun In 1676, the scientist Isaac Newton, in a letter to Robert Hooke used the phrase (http://www.phrases.org.uk/meanings/268025.html) ‘If I have seen a little further it is by standing on the shoulders of Giants’ I’m a nuclear physicist by education, so I am more than comfortable that any knowledge I have is based on the work of others.  Although far from a science, software development and IT is equally built upon the work of others. It’s one of the reasons I despise software patents. So in that sense this MVP award is a result of all the great minds that have provided virtualisation solutions for me to talk about.  I hope that I have always acknowledged those whose work I have used when blogging or giving presentations, and that I have executed my responsibility to share any knowledge gained as widely as possible. Thanks to all those who helped – a big thanks to the UK user group community I reckon this journey started in 2003 when I started attending a user group called the London .Net Users Group (http://www.dnug.org.uk) started by a nice chap called Ian Cooper. The great thing about Ian was that he always encouraged non professional speakers to take the stage at the user group, and my first ever presentation was on 30th September 2003; SQL Server CE 2.0 and the.NET Compact Framework. In 2005 Ian Cooper was on the committee for the first DeveloperDeveloperDeveloper! day, the free community conference held at Microsoft’s UK HQ in Thames Valley park in Reading.  He encouraged me to take part and so on 14th May 2005 I presented a talk previously given to the London .Net User Group on Simplifying access to multiple DB providers in .NET.  From that point on I definitely had the bug; presenting at DDD2, DDD3, groking at DDD4 and SQLBits I and after a break, DDD7, DDD Scotland and DDD8.  What definitely made me keen was the encouragement and infectious enthusiasm of some of the other DDD organisers; Craig Murphy, Barry Dorrans, Phil Winstanley and Colin Mackay. During the first few DDD events I met the Dave McMahon and Richard Costall from NxtGenUG who made it easy to start presenting at their user groups.  Along the way I’ve met a load of great user group organisers; Guy Smith-Ferrier of the .Net Developer Network, Jimmy Skowronski of GL.Net and the double act of Ray Booysen and Gavin Osborn behind what was Vista Squad and is now Edge UG. Final thanks to those who suggested virtualisation as a topic ... Final thanks have to go the people who inspired me to create my Virtualisation for Developers talk.  Toby Henderson (@holytshirt) ensured I took notice of Sun’s VirtualBox, Peter Ibbotson for being a fine sounding board at the Kew Railway over quite a few Adnam’s Broadside and to Guy Smith-Ferrier for allowing his user group to be the guinea pigs for the talk before it was seen at DDD7.  Thanks to all of you I now know much more about virtualisation than I would have thought possible and it continues to be great fun. Conclusion If this was an academy award acceptance speech I would have been cut off after the first few paragraphs, so well done if you made it this far.  I’ll be doing my best to do justice to the MVP award and the UK community.  I’m fortunate in having a new employer who considers presenting at user groups as a good thing, so don’t expect me to stop any time soon. If you’ve never seen me in action, then you can view the original DDD7 Virtualisation for Developers presentation (filmed by the Microsoft Channel 9 team) as part of the full DDD7 video list here, http://www.craigmurphy.com/blog/?p=1591.  Also thanks to Craig Murphy’s fine video work you can also view my latest DDD8 presentation on Commercial Software Development, here, http://vimeo.com/9216563 P.S. If I’ve missed anyone out, do feel free to lambast me in comments, it’s your duty.

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• NET Math Libraries

  - by JoshReuben

  NET Mathematical Libraries   .NET Builder for Matlab The MathWorks Inc. - http://www.mathworks.com/products/netbuilder/ MATLAB Builder NE generates MATLAB based .NET and COM components royalty-free deployment creates the components by encrypting MATLAB functions and generating either a .NET or COM wrapper around them. .NET/Link for Mathematica www.wolfram.com a product that 2-way integrates Mathematica and Microsoft's .NET platform call .NET from Mathematica - use arbitrary .NET types directly from the Mathematica language. use and control the Mathematica kernel from a .NET program. turns Mathematica into a scripting shell to leverage the computational services of Mathematica. write custom front ends for Mathematica or use Mathematica as a computational engine for another program comes with full source code. Leverages MathLink - a Wolfram Research's protocol for sending data and commands back and forth between Mathematica and other programs. .NET/Link abstracts the low-level details of the MathLink C API. Extreme Optimization http://www.extremeoptimization.com/ a collection of general-purpose mathematical and statistical classes built for the.NET framework. It combines a math library, a vector and matrix library, and a statistics library in one package. download the trial of version 4.0 to try it out. Multi-core ready - Full support for Task Parallel Library features including cancellation. Broad base of algorithms covering a wide range of numerical techniques, including: linear algebra (BLAS and LAPACK routines), numerical analysis (integration and differentiation), equation solvers. Mathematics leverages parallelism using .NET 4.0's Task Parallel Library. Basic math: Complex numbers, 'special functions' like Gamma and Bessel functions, numerical differentiation. Solving equations: Solve equations in one variable, or solve systems of linear or nonlinear equations. Curve fitting: Linear and nonlinear curve fitting, cubic splines, polynomials, orthogonal polynomials. Optimization: find the minimum or maximum of a function in one or more variables, linear programming and mixed integer programming. Numerical integration: Compute integrals over finite or infinite intervals, over 2D and higher dimensional regions. Integrate systems of ordinary differential equations (ODE's). Fast Fourier Transforms: 1D and 2D FFT's using managed or fast native code (32 and 64 bit) BigInteger, BigRational, and BigFloat: Perform operations with arbitrary precision. Vector and Matrix Library Real and complex vectors and matrices. Single and double precision for elements. Structured matrix types: including triangular, symmetrical and band matrices. Sparse matrices. Matrix factorizations: LU decomposition, QR decomposition, singular value decomposition, Cholesky decomposition, eigenvalue decomposition. Portability and performance: Calculations can be done in 100% managed code, or in hand-optimized processor-specific native code (32 and 64 bit). Statistics Data manipulation: Sort and filter data, process missing values, remove outliers, etc. Supports .NET data binding. Statistical Models: Simple, multiple, nonlinear, logistic, Poisson regression. Generalized Linear Models. One and two-way ANOVA. Hypothesis Tests: 12 14 hypothesis tests, including the z-test, t-test, F-test, runs test, and more advanced tests, such as the Anderson-Darling test for normality, one and two-sample Kolmogorov-Smirnov test, and Levene's test for homogeneity of variances. Multivariate Statistics: K-means cluster analysis, hierarchical cluster analysis, principal component analysis (PCA), multivariate probability distributions. Statistical Distributions: 25 29 continuous and discrete statistical distributions, including uniform, Poisson, normal, lognormal, Weibull and Gumbel (extreme value) distributions. Random numbers: Random variates from any distribution, 4 high-quality random number generators, low discrepancy sequences, shufflers. New in version 4.0 (November, 2010) Support for .NET Framework Version 4.0 and Visual Studio 2010 TPL Parallellized – multicore ready sparse linear program solver - can solve problems with more than 1 million variables. Mixed integer linear programming using a branch and bound algorithm. special functions: hypergeometric, Riemann zeta, elliptic integrals, Frensel functions, Dawson's integral. Full set of window functions for FFT's. Product  Price Update subscription Single Developer License $999  $399  Team License (3 developers) $1999  $799  Department License (8 developers) $3999  $1599  Site License (Unlimited developers in one physical location) $7999  $3199    NMath http://www.centerspace.net .NET math and statistics libraries matrix and vector classes random number generators Fast Fourier Transforms (FFTs) numerical integration linear programming linear regression curve and surface fitting optimization hypothesis tests analysis of variance (ANOVA) probability distributions principal component analysis cluster analysis built on the Intel Math Kernel Library (MKL), which contains highly-optimized, extensively-threaded versions of BLAS (Basic Linear Algebra Subroutines) and LAPACK (Linear Algebra PACKage). Product  Price Update subscription Single Developer License $1295 $388 Team License (5 developers) $5180 $1554   DotNumerics http://www.dotnumerics.com/NumericalLibraries/Default.aspx free DotNumerics is a website dedicated to numerical computing for .NET that includes a C# Numerical Library for .NET containing algorithms for Linear Algebra, Differential Equations and Optimization problems. The Linear Algebra library includes CSLapack, CSBlas and CSEispack, ports from Fortran to C# of LAPACK, BLAS and EISPACK, respectively. Linear Algebra (CSLapack, CSBlas and CSEispack). Systems of linear equations, eigenvalue problems, least-squares solutions of linear systems and singular value problems. Differential Equations. Initial-value problem for nonstiff and stiff ordinary differential equations ODEs (explicit Runge-Kutta, implicit Runge-Kutta, Gear's BDF and Adams-Moulton). Optimization. Unconstrained and bounded constrained optimization of multivariate functions (L-BFGS-B, Truncated Newton and Simplex methods).   Math.NET Numerics http://numerics.mathdotnet.com/ free an open source numerical library - includes special functions, linear algebra, probability models, random numbers, interpolation, integral transforms. A merger of dnAnalytics with Math.NET Iridium in addition to a purely managed implementation will also support native hardware optimization. constants & special functions complex type support real and complex, dense and sparse linear algebra (with LU, QR, eigenvalues, ... decompositions) non-uniform probability distributions, multivariate distributions, sample generation alternative uniform random number generators descriptive statistics, including order statistics various interpolation methods, including barycentric approaches and splines numerical function integration (quadrature) routines integral transforms, like fourier transform (FFT) with arbitrary lengths support, and hartley spectral-space aware sequence manipulation (signal processing) combinatorics, polynomials, quaternions, basic number theory. parallelized where appropriate, to leverage multi-core and multi-processor systems fully managed or (if available) using native libraries (Intel MKL, ACMS, CUDA, FFTW) provides a native facade for F# developers

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• Building Enterprise Smartphone App &ndash; Part 2: Platforms and Features

  - by Tim Murphy

  This is part 2 in a series of posts based on a talk I gave recently at the Chicago Information Technology Architects Group.  Feel free to leave feedback. In the previous post I discussed what reasons a company might have for creating a smartphone application.  In this installment I will cover some of history and state of the different platforms as well as features that can be leveraged for building enterprise smartphone applications. Platforms Before you start choosing a platform to develop your solutions on it is good to understand how we got here and what features you can leverage. History To my memory we owe all of this to a product called the Apple Newton that came out in 1987. It was the first PDA and back then I was much more of an Apple fan.  I was very impressed with this device even though it never really went anywhere.  The Palm Pilot by US Robotics was the next major advancement in PDA. It had a simple short hand window that allowed for quick stylus entry.. Later, Windows CE came out and started the broadening of the PDA market. After that it was the Palm and CE operating systems that started showing up on cell phones and for some time these were the two dominant operating systems that were distributed with devices from multiple hardware vendors. Current The iPhone was the first smartphone to take away the stylus and give us a multi-touch interface.  It was a revolution in usability and really changed the attractiveness of smartphones for the general public.  This brought us to the beginning of the current state of the market with the concept of an online store that makes it easy for customers to get new features and functionality on demand. With Android, Google made this more than a one horse race.  Not only did they come to compete, their low cost actually made them the leading OS.  Of course what made Android so attractive also is its major fault.  It is so open that it has been a target for malware which leaves consumers exposed.  Fortunately for Google though, most consumers aren’t aware of the threat that they are under. Although Microsoft had put out one of the first smart phone operating systems with CE it had to play catch up and finally came out with the Windows Phone.  They have gone for a market approach between those of iOS and Android.  They support multiple hardware vendors like Google, but they kept a certification process for applications that is similar to Apple.  They also created a user interface that was different enough to give it a clear separation from the other two platforms. The result of all this is hundreds of millions of smartphones being sold monthly across all three platforms giving us a wide range of choices and challenges when it comes to developing solutions. Features So what are the features that make these devices flexible enough be considered for use in the enterprise? The biggest advantage of today's devices is network connectivity.  The ability to access information from multiple sources at a moment’s notice is critical for businesses.  Add to that the ability to communicate over a variety of text, voice and video modes and we have a powerful starting point. Every smartphone has a cameras and they are not just useful for posting to Instagram. We are seeing more applications such as Bing vision that allow us to scan just about any printed code or text to find information.  These capabilities have been made available to developers in the form of standard libraries for reading barcodes of just about an flavor and optical character recognition (OCR) interpretation. Bluetooth give us the ability to communicate with multiple devices. Whether these are headsets, keyboard or printers the wireless communication capabilities are just starting to evolve.  The more these wireless communication protocols grow, the more opportunities we will see to transfer data between users and a variety of devices. Local storage of information that can be called up even when the device cannot reach the network is the other big capability.  This give users the ability to work offline as well and transmit information when connections are restored. These are the tools that we have to work with to build applications that can be leveraged to gain a competitive advantage for companies that implement them. Coming Up In the third installment I will cover key concerns that you face when building enterprise smartphone apps. del.icio.us Tags: smartphones,enterprise smartphone Apps,architecture,iOS,Android,Windows Phone

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• R glm standard error estimate differences to SAS PROC GENMOD

  - by Michelle

  I am converting a SAS PROC GENMOD example into R, using glm in R. The SAS code was: proc genmod data=data0 namelen=30; model boxcoxy=boxcoxxy ~ AGEGRP4 + AGEGRP5 + AGEGRP6 + AGEGRP7 + AGEGRP8 + RACE1 + RACE3 + WEEKEND + SEQ/dist=normal; FREQ REPLICATE_VAR; run; My R code is: parmsg2 <- glm(boxcoxxy ~ AGEGRP4 + AGEGRP5 + AGEGRP6 + AGEGRP7 + AGEGRP8 + RACE1 + RACE3 + WEEKEND + SEQ , data=data0, family=gaussian, weights = REPLICATE_VAR) When I use summary(parmsg2) I get the same coefficient estimates as in SAS, but my standard errors are wildly different. The summary output from SAS is: Name df Estimate StdErr LowerWaldCL UpperWaldCL ChiSq ProbChiSq Intercept 1 6.5007436 .00078884 6.4991975 6.5022897 67911982 0 agegrp4 1 .64607262 .00105425 .64400633 .64813891 375556.79 0 agegrp5 1 .4191395 .00089722 .41738099 .42089802 218233.76 0 agegrp6 1 -.22518765 .00083118 -.22681672 -.22355857 73401.113 0 agegrp7 1 -1.7445189 .00087569 -1.7462352 -1.7428026 3968762.2 0 agegrp8 1 -2.2908855 .00109766 -2.2930369 -2.2887342 4355849.4 0 race1 1 -.13454883 .00080672 -.13612997 -.13296769 27817.29 0 race3 1 -.20607036 .00070966 -.20746127 -.20467944 84319.131 0 weekend 1 .0327884 .00044731 .0319117 .03366511 5373.1931 0 seq2 1 -.47509583 .00047337 -.47602363 -.47416804 1007291.3 0 Scale 1 2.9328613 .00015586 2.9325559 2.9331668 -127 The summary output from R is: Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 6.50074 0.10354 62.785 < 2e-16 AGEGRP4 0.64607 0.13838 4.669 3.07e-06 AGEGRP5 0.41914 0.11776 3.559 0.000374 AGEGRP6 -0.22519 0.10910 -2.064 0.039031 AGEGRP7 -1.74452 0.11494 -15.178 < 2e-16 AGEGRP8 -2.29089 0.14407 -15.901 < 2e-16 RACE1 -0.13455 0.10589 -1.271 0.203865 RACE3 -0.20607 0.09315 -2.212 0.026967 WEEKEND 0.03279 0.05871 0.558 0.576535 SEQ -0.47510 0.06213 -7.646 2.25e-14 The importance of the difference in the standard errors is that the SAS coefficients are all statistically significant, but the RACE1 and WEEKEND coefficients in the R output are not. I have found a formula to calculate the Wald confidence intervals in R, but this is pointless given the difference in the standard errors, as I will not get the same results. Apparently SAS uses a ridge-stabilized Newton-Raphson algorithm for its estimates, which are ML. The information I read about the glm function in R is that the results should be equivalent to ML. What can I do to change my estimation procedure in R so that I get the equivalent coefficents and standard error estimates that were produced in SAS? To update, thanks to Spacedman's answer, I used weights because the data are from individuals in a dietary survey, and REPLICATE_VAR is a balanced repeated replication weight, that is an integer (and quite large, in the order of 1000s or 10000s). The website that describes the weight is here. I don't know why the FREQ rather than the WEIGHT command was used in SAS. I will now test by expanding the number of observations using REPLICATE_VAR and rerunning the analysis.

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• approximating log10[x^k0 + k1]

  - by Yale Zhang

  Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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