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• Minimize useless tweaking of a numeric app

  - by Potatoswatter

  I'm developing a numeric application (nonlinear optimizer), with a zillion knobs to tweak and rising. It's not my first foray into this domain, but this time there are even more variables in the code and I'm on a tight schedule. Don't want to waste time fiddling. Days or even months can potentially be wasted adjusting variables, recompiling, and reprocessing benchmark datasets. The resulting data is viewed and trouble spots are checked. The overall quality of the solution is reported by the program but the meaning of the report could change over time. (Numeric units for the report are one thing I'm trying to nail down.) One main problem is organizing result files to identify each with specific code changes. Note taking can be a pain, is there software to help with this? Are there agreed best practices to making this kind of development cycle reliably move forward? The solver package converges to its optimal solution with mechanical determination, but I'm all too familiar with the way an excess of design decisions can mire development.

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• Operating systems -- using minimum number of semaphores

  - by stackuser

  The three cooperating processes all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'd like to use semaphores to synchronize the following processes: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W I'm wondering how to use the minimum number of semaphores to solve this. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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• Flame Experiments Aboard the ISS Yield Surprising Results

  - by Jason Fitzpatrick

  Recent flame-based experiments aboard the International Space Station yielded results scientists simply thought couldn’t happen–combustion in microgravity is a curious thing. Smithsonian magazine reports on the findings: Here on Earth, when a flame burns, it heats the surrounding atmosphere, causing the air to expand and become less dense. The pull of gravity draws colder, denser air down to the base of the flame, displacing the hot air, which rises. This convection process feeds fresh oxygen to the fire, which burns until it runs out of fuel. The upward flow of air is what gives a flame its teardrop shape and causes it to flicker. But odd things happen in space, where gravity loses its grip on solids, liquids and gases. Without gravity, hot air expands but doesn’t move upward. The flame persists because of the diffusion of oxygen, with random oxygen molecules drifting into the fire. Absent the upward flow of hot air, fires in microgravity are dome-shaped or spherical—and sluggish, thanks to meager oxygen flow. “If you ignite a piece of paper in microgravity, the fire will just slowly creep along from one end to the other,” says Dietrich. “Astronauts are all very excited to do our experiments because space fires really do look quite alien.” Hit up the link below for the full article including how NASA is applying the findings. Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder? Why Your Android Phone Isn’t Getting Operating System Updates and What You Can Do About It How To Delete, Move, or Rename Locked Files in Windows

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• Craft a Drinkable Density Column

  - by Jason Fitzpatrick

  Earlier this month we shared a clever 9-layer density column demonstration you’d most certainly not want to drink. This smaller demonstration, however, is a delicious column of fruit flavors. The secret sauce? In the previous experiment we shared the secret was using fluids with naturally varying densities (such as lamp oil and vegetable oil); in this experiment you’ll be relying on varying amounts of sugar in each layer to change the density of the water and keep them separate (and edible). You’ll need some Skittles, a few drinking glasses, water, and for best effect, a tall and narrow glass or graduated cylinder. Hit up the link below for the full details on the experiment and tips on how to carefully layer the liquids. Make a Drinkable Rainbow in a Glass [i09] Can Dust Actually Damage My Computer? What To Do If You Get a Virus on Your Computer Why Enabling “Do Not Track” Doesn’t Stop You From Being Tracked

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• What is Atomicity?

  - by James Jeffery

  I'm really struggling to find a concrete, easy to grasp, explanation of Atomicity. My understanding thus far is that to ensure an operation is atomic you wrap the critical code in a locker. But that's about as much as I actually understand. Definitions such as the one below make no sense to me at all. An operation during which a processor can simultaneously read a location and write it in the same bus operation. This prevents any other processor or I/O device from writing or reading memory until the operation is complete. Atomic implies indivisibility and irreducibility, so an atomic operation must be performed entirely or not performed at all. What does the last sentence mean? Is the term indivisibility relating to mathematics or something else? Sometimes the jargon with these topics confuse more than they teach.

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• DIY Homemade Hybrid Rocket Engine [Video]

  - by Jason Fitzpatrick

  Remember the guy with the cool DIY astronaut ice cream build? He’s back with a mini hybrid rocket engine that runs off oxygen and acrylic. I built a small rocket engine for demonstration purposes. The engine is built from a 2″ diameter acrylic rod through which I drilled a 0.5″ hole. The oxygen at 80 psi or less is passed through the hole and then is forced through a convergent-divergent nozzle at the tail end. The nozzle’s throat is about 0.25″ and expands to 0.625″. I lit the engine by inserting a burning cotton swab (with wooden stick) while a small amount of oxygen was flowing. The acrylic catches fire very easily in a pure oxygen environment. The engine can be throttled and shut off completely, which is a major benefit to hybrid engine designs. Solid-fuel rockets cannot be throttled or shut off, which makes them difficult to control. [via Make] HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference How To Troubleshoot Internet Connection Problems

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• How can I make sure that I'm actually learning how to program rather than simply learning the details of a language?

  - by Ryan

  I often hear that a real programmer can easily learn any language within a week. Languages are just tools for getting things done, I'm told. Programming is the ultimate skill that must be learned and mastered. How can I make sure that I'm actually learning how to program rather than simply learning the details of a language? And how can I develop programming skills that can be applied towards all languages instead of just one?

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• Make Your Own Paper-Craft Enigma Machine [DIY Project]

  - by Asian Angel

  If you love tinkering around with ciphers and want a fun DIY project for the upcoming weekend, then we have just the thing for you. Using common household items you can construct your own personal Enigma machine that will be completely compatible with all the settings of a real Enigma machine (models I, M1, M2 and M3). Visit the second link below for the step-by-step instructions and enjoy putting together this awesome DIY project! PDF Templates for the Enigma Machine Note: This is a direct link for the PDF file itself and the templates are sized for printing on 2 A4 sheets of paper. Enigma/Paper Enigma Instruction Homepage [via BoingBoing] HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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• What's a nice explanation for pointers?

  - by Macneil

  In your own studies (on your own, or for a class) did you have an "ah ha" moment when you finally, really understood pointers? Do you have an explanation you use for beginner programmers that seems particularly effective? For example, when beginners first encounter pointers in C, they might just add &s and *s until it compiles (as I myself once did). Maybe it was a picture, or a really well motivated example, that made pointers "click" for you or your student. What was it, and what did you try before that didn't seem to work? Were any topics prerequisites (e.g. structs, or arrays)? In other words, what was necessary to understand the meaning of &s and *, when you could use them with confidence? Learning the syntax and terminology or the use cases isn't enough, at some point the idea needs to be internalized. Update: I really like the answers so far; please keep them coming. There are a lot of great perspectives here, but I think many are good explanations/slogans for ourselves after we've internalized the concept. I'm looking for the detailed contexts and circumstances when it dawned on you. For example: I only somewhat understood pointers syntactically in C. I heard two of my friends explaining pointers to another friend, who asked why a struct was passed with a pointer. The first friend talked about how it needed to be referenced and modified, but it was just a short comment from the other friend where it hit me: "It's also more efficient." Passing 4 bytes instead of 16 bytes was the final conceptual shift I needed.

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• How to Make a Laser Microscope at Home [Video]

  - by Asian Angel

  Earlier this year we shared a video that showed you how to make a microscope projector using a green laser light and a webcam lens. Today we are back with a video demonstrating an easy “at home” method using that same green laser light, a syringe, two glasses, and a blank wall. Note: Video contains some language that may be considered inappropriate. How to make a laser microscope [via Geeks are Sexy] Use Amazon’s Barcode Scanner to Easily Buy Anything from Your Phone How To Migrate Windows 7 to a Solid State Drive Follow How-To Geek on Google+

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• What are the fundamentals of game development?

  - by Matt

  Hi, I completely do not understand how a video game can be coded. I'm a beginner programmer and only have experience writing console applications that do math and what not. I do not understand how these logical processes can make images move on the screen (video games). Obviously if i jumped into a game development book or something like that I would understand but I am currently still getting a grasp of the fundamentals of programming in general. Could anyone give a simple explanation , coding wise, on the jump between making a computer do simple math to making a computer produce amazing graphical programs such as video games? Maybe there are some intro videos someone can point me to? I

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• This Week in Geek History: The Call of Cthulhu, the Columbia Shuttle Disaster, and the Birth of Facebook

  - by Jason Fitzpatrick

  This week in Geek History saw the beginning of the Cthulhu horror mythos, the Columbia space shuttle disaster, and the birth of Facebook. Also, check out our new addition “Other Notable Moments” at the end for more facts and trivia from this week in Geek History. Latest Features How-To Geek ETC How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin The How-To Geek Video Guide to Using Windows 7 Speech Recognition Stylebot Customizes Web Pages in Chrome, Now Has Downloadable Styles Blackberry, Dell, Apple, and Motorola Tablets Compared [Infographic] Encrypt Your Google Search Queries Vintage Posters Showcase the History of Tech Advertising Google Cloud Print Extension Lets You Print Doc/PDF/Txt Files from Web Sites Hack a $10 Flashlight into an Ultra-bright Premium One

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• Do you count a Masters in CS as a negative?

  - by Pete Hodgson

  In my experience interviewing developers I feel like candidates who've achieved a Masters in Comp Sci tend to be worse programmers on average that those who don't have a Masters. Is that just me, or have others noticed this phenomenon? If so, why would that be the case? UPDATE I appreciate the thoughtful comments. I think I should have been clearer in the comparison I'm making. Given two candidates who graduated from college around the same time, someone who went on to gain a Masters seems on average to be a worse programmer than someone who spent all their time in industry.

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• The Evolution of the Moon – Past to Present [Video]

  - by Asian Angel

  The Moon seems like a pretty quiet place these days, but it has not always been so. Take a journey through time and watch the evolution of the Moon with this terrific video from NASA! NASA | Evolution of the Moon [via Geeks are Sexy] The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos

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• What are some recommended video lectures for a non-CS student to prepare for the GRE CS subject test?

  - by aristos

  Well the title kinda explains all there is to explain. I'm a non-cs student and was preparing to apply PhD programs in applied mathematics. But for my senior thesis I've been reading lots of machine learning and pattern recognition literature and enjoying it a lot. I've taken lots of courses with statistics and stochastics content, which I think, would help me if I get accepted to a program with ML focus, but there are only two CS courses -introduction to programming- in my transcript and therefore I decided to take the CS subject test to increase my chances. Which courses do you think would be most essential to have a good result from CS subject test? I'm thinking of watching video lectures of them, so do you have any recommendations?

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• Classic UFO Identification Chart from March 1967 [Retro Image]

  - by Asian Angel

  If you love classic sci-fi goodness, then you will definitely enjoy looking through the various ‘alien’ starcraft featured in this classic chart from yesteryear! View the Full-Size Version (914*1280 pixels) UFO Identification Chart – Stargods Blog [via Cheezburger.com] Java is Insecure and Awful, It’s Time to Disable It, and Here’s How What Are the Windows A: and B: Drives Used For? HTG Explains: What is DNS?

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• I'm having trouble learning

  - by Gavin Sapp

  I'm only 13 but i'm genuinely interested in CS and would really like it if I could actually accomplish it. I've read books on C++ and C#, but ALL of them are the same!! They all say "Ok so since you have no prior knowledge in this what so ever, write a snippet that will do this and then make a GUI and then throw it into the Priafdhsu hfad then add the program and then program your own compiler to do some stuff". It's really getting annoying. I've payed near $40 (via Paypal) on ebooks that supposedly taught people to program with no prior knowledge. ALL OF THEM EXPECT ME TO ALREADY KNOW THE LANGUAGE. Is there something that I'm missing or am I suppose to be born with the property of CS? I would very much appreciate it if someone could explain this to me or possibly refer me to a tutorial on Programming Theory that starts from below ground zero as I have know knowledge in CS at all.

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• What if the Earth were Hollow? [Video]

  - by Asian Angel

  What would things be like if you dug a tunnel completely through the Earth for travel purposes or if our planet were hollow? Minute Physics takes a look at how things would be if either of these scenarios actually existed. What if the Earth were Hollow? [via Geeks are Sexy] How To Switch Webmail Providers Without Losing All Your Email How To Force Windows Applications to Use a Specific CPU HTG Explains: Is UPnP a Security Risk?

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• Common mistakes made by new programmers without CS backgrounds [on hold]

  - by mblinn

  I've noticed that there seems to be a class of mistakes that new programmers without CS backgrounds tend to make, that programmers with CS backgrounds tend not to. I'm not talking about not understanding source control, or how to design large programs, or a whole host of other things that both freshly minted CS graduates and non-CS graduates tend to not understand, I'm talking about basic mistakes that having a CS background will prevent a programmer from making. One obvious and well trod example is that folks who don't have a basic understanding of formal languages will often try to parse arbitrary HTML or XML using regular expressions, and possibly summon Cthulu in the process. Another fairly common one that I've seen is using common data structures in suboptimal ways like using a vector and a search function as if it were a hash map. What sorts of other things along these lines would you look out for when on-boarding a batch of newly minted, non-CS programmers.

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• How many copies are needed to enlarge an array?

  - by user10326

  I am reading an analysis on dynamic arrays (from the Skiena's algorithm manual). I.e. when we have an array structure and each time we are out of space we allocate a new array of double the size of the original. It describes the waste that occurs when the array has to be resized. It says that (n/2)+1 through n will be moved at most once or not at all. This is clear. Then by describing that half the elements move once, a quarter of the elements twice, and so on, the total number of movements M is given by: This seems to me that it adds more copies than actually happen. E.g. if we have the following: array of 1 element +--+ |a | +--+ double the array (2 elements) +--++--+ |a ||b | +--++--+ double the array (4 elements) +--++--++--++--+ |a ||b ||c ||c | +--++--++--++--+ double the array (8 elements) +--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x | +--++--++--++--++--++--++--++--+ double the array (16 elements) +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x || || || || || || || || | +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ We have the x element copied 4 times, c element copied 4 times, b element copied 4 times and a element copied 5 times so total is 4+4+4+5 = 17 copies/movements. But according to formula we should have 1*(16/2)+2*(16/4)+3*(16/8)+4*(16/16)= 8+8+6+4=26 copies of elements for the enlargement of the array to 16 elements. Is this some mistake or the aim of the formula is to provide a rough upper limit approximation? Or am I missunderstanding something here?

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• Which is the next dominant programming paradigm? [closed]

  - by Kugathasan Abimaran

  What is the next programming paradigm when OOP get lost in the market? Or else will OOP be for ever? What is your advise for the future developers? To which paradigm should we aware of? Because, before OOP, structured programming paradigm is there with C. Don't close it Please, because I need to aware, which paradigm have the ability to withstand in future? Aspect-oriented programming. Declarative programming. Functional programming. Object-oriented programming. Any Others? This describes programming paradigm according to their kernel language.

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• Do you count a Masters in CS as a negative? [closed]

  - by Pete Hodgson

  In my experience interviewing developers I feel like candidates who've achieved a Masters in Comp Sci tend to be worse programmers on average that those who don't have a Masters. Is that just me, or have others noticed this phenomenon? If so, why would that be the case? UPDATE I appreciate the thoughtful comments. I think I should have been clearer in the comparison I'm making. Given two candidates who graduated from college around the same time, someone who went on to gain a Masters seems on average to be a worse programmer than someone who spent all their time in industry.

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• When and why are certain data structures used in the context of web development?

  - by Ein Doofus

  While browsing around the MSDN I came across: http://msdn.microsoft.com/en-us/library/aa287104%28v=vs.71%29 which lists various data structures such as: Queues Stacks Hashtables Binary Trees Binary Search Trees Graphs (I believe there are also Lists) and I was hoping to get a high-level overview of when these various data structures can be used in the broad context of web development, and when used, why one data structure is generally used instead of any other one.

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• Motion Sickness – What is It? [Video]

  - by Asian Angel

  Experiencing motion sickness is unpleasant and frustrating, but have you ever wondered what causes you to feel it? This video from AsapSCIENCE explains what causes you to feel motion sickness and shows some ‘events’ you might avoid that can trigger it… Motion Sickness – What is it? [via Neatorama] 8 Deadly Commands You Should Never Run on Linux 14 Special Google Searches That Show Instant Answers How To Create a Customized Windows 7 Installation Disc With Integrated Updates

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• Creating your own computer! [closed]

  - by AntonioCS

  I recently found this article on a guy that built his own computer. It's just a bunch of wire (as far as I can tell any way) and I was just wondering what would I have to learn/read/do to make such a thing (or at least to have a really basic understanding of what he did). He also made his own operating system, which I find really impressive. I know it will take a while and I am in no hurry. Note: I am a web programmer and also have done some desktop apps (a few years ago).

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