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  • Where to get laptop replacement parts?

    - by wai
    I am sure some of us have older laptops that still works but just one or two parts started not working very well. However, to send it back to the manufacturer for repair might not be worth the money (as some of them even charge consultation fees just to have it checked) as these old laptops are most probably well beyond warranty. Replacing these one or two parts could give your laptop a new lease of life. For example, I have a Dell Inspiron 640m which the fan recently failed. Everything else still works. I know enough to open up the laptop (after reading the service manual) and put it back together again, hence a replacement fan could save it. However, finding these parts turned out to be difficult. I guess I wouldn't be able to get it from Dell since I have been searching around the Dell forums and concluded if I were going to get Dell to at least talk to me, I would have to pay some money (since my warranty expired). I found this online:- http://www.parts-people.com/index.php?action=item&id=3725 However, as I don't live in the United States, shipping alone would cost me 3 times more than the part in question. In addition, if there's a problem, it would be difficult because I probably would have to mail the parts back (costing more money). One of my friend spilled water on her Macbook, she sent it back to Apple and they told her the cost of repairing it exceeds that of buying a new Macbook. They probably have to change everything except the LCD screen. I opened it up and found that most of the parts are still working, only the RAM had fried. Replaced it and it's working again. For some time before discovering only the RAM fried, I was toying with the idea of replacing the logic board myself but looks like I didn't have to. =) Now I know there's a site for Macbooks used replacement parts:- http://www.ifixit.com/ The question is, does anyone know where to get replacement parts at their own locality? It might benefit the community as a whole. Someone might know a local computer store that sells precisely just the things we needed (for now, I hope to find a shop that sells just the fan). If you own a laptop which you had an easy experience finding the replacement parts, do post that as well. PS: I wish laptop manufacturers have outlets where they sell these replacement parts (or at least let you place an order).

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  • Custom built machine has much higher power consumption than expected

    - by foraidt
    I built a machine according to the specs of a computer magazine (c't, Germany). According to the magazine, the power consumption should be at around 10W. I don't want to go into the specifics of the hardware but rather ask for general advice on where to look: I updated the BIOS/UEFI version to the latest version, installed all the recommended drivers and unplugged all hardware that's not necessary to boot into Windows. All that was left is the power supply, mainboard, cpu, cpu cooler and one SSD drive. But still I measured a power consumption of 50W, which is 40W more than it should be. I tried booting Linux Mint from a USB stick, so I don't think it's some Windows-related problem.. Where else could I look? Update 1 I dind't want the question to get closed for being too localized but if more details are necessary, here they are: The system is a desktop PC. The power consumption is measured using a Brennenstuhl PM 231 device, which was tested also by c't and they found it quite accurate. The PSU is an Enermax ETL300AWT, the mainboard Intel DH87RL (Socket 1150) and the CPU Intel G3220 (Haswell). Update 2 There is no online version of the article*. The most details I found can be read on its project page (in German, though...) (*)You can pay for downloadable PDFs, however. English translation of that project page Update 3 Regarding the sceptics: It may sound ridiculous but apparently 10W idle consumption is possible with Intel's Haswell architecture. As a kind of proof, there's an additional Blog article explicitly listing the steps needed to reduce the idle consumption to 10W. Additional hardware: I measured the consumption without the HDD, and as expected the usage dropped by around 10W. I have no chassis fans and the CPU fan is a "Scythe Mugen 4" model. It runs at around 600rpm so I think it won't draw much. When stripping off all my extra components I should be at 10W. But I'm not getting anywhere near that. I would be happy to see "just" 15W in the stripped down version but currently I'm not getting below 50W no matter which component I remove. As I see it this cannot be explained by the PSU being less efficient at lower consumption. I also waited half an hour or so (also checked that no Windows updates were running in the background) and the consumption dind't drop by more than a few watts.

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  • Objective-measures of the power of programming languages

    - by Casebash
    Are there any objective measures for measuring the power of programming languages? Turing-completeness is one, but it is not particularly discriminating. I also remember there being a few others measures of power which are more limited versions (like finite-state-autonoma), but is there any objective measure that is more powerful?

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  • Boosting my GA with Neural Networks and/or Reinforcement Learning

    - by AlexT
    As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

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  • two's complement, why the name "two"

    - by lenatis
    i know unsigned,two's complement, ones' complement and sign magnitude, and the difference between these, but what i'm curious about is: why it's called two's(or ones') complement, so is there a more generalize N's complement? in which way did these genius deduce such a natural way to represent negative numbers?

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  • Dynamic programming - Coin change decision problem?

    - by Tony
    I'm reviewing some old notes from my algorithms course and the dynamic programming problems are seeming a bit tricky to me. I have a problem where we have an unlimited supply of coins, with some denominations x1, x2, ... xn and we want to make change for some value X. We are trying to design a dynamic program to decide whether change for X can be made or not (not minimizing the number of coins, or returning which coins, just true or false). I've done some thinking about this problem, and I can see a recursive method of doing this where it's something like... MakeChange(X, x[1..n this is the coins]) for (int i = 1; i < n; i++) { if ( (X - x[i] ==0) || MakeChange(X - x[i]) ) return true; } return false; Converting this a dynamic program is not coming so easily to me. How might I approach this?

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  • I dont understand Access modifiers in OOP (JAVA)

    - by Imran
    I know this is a silly question but i don't understand Access Modifiers in OOP. Why do we make for example in JAVA instance variables private and then use public getter and setter methods to access them? I mean whats the reasoning/logic behind this? You still get to the instance variable but why use setter and getter methods when you can just make your variables public? please excuse my ignorance as i'm simply trying to understand why we do this? Thank you in advance;-)

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  • Dijkstra’s algorithms - a complete list

    - by baris_a
    Hi guys, I have recently asked a question about one of the Dijkstra’s algorithms. But, almost everyone thought it was shortest path. Therefore, I opened this post to gather all the algorithms that were invented by Dijkstra. Please add any if you know. Thanks in advance. 1 ) Shunting-yard algorithm

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  • netlogo programming question - catalyst implementation part 2

    - by user286190
    hi the catalyst speeds up the reaction but remains unchanged after the reaction has taken place i tried the following code breed [catalysts catalyst] breed [chemical-x chemical-x] ;then the forward reaction is sped up by the existence of catalysts to react-forward let num-catalysts count catalysts ;speed up by num-catalysts ;... end and it works fine but I want to make it so that the catalyst can be switched on and off with the 'switch' button ..so one can see the effects with and without the catalyst..i tried putting a switch in but catalyst has already been defined Also i want to make the catalyst visible so one can see it in the actual implementation (in the world) like making it a turtle is there are another way to implement this apart from using breeds i tried making the catalyst a turtle but it doesnt work ; Make catalyst visible in implementation clear-all crt catalysts 100 ask catalysts [ set color white ] show [breed] of one-of catalysts ; prints catalysts any help will be greatly appreciated thank you

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  • Papers on Software Methodology recommendation

    - by kunjaan
    Please recommend me software engineering/methodology/practices paper. So far I have enjoyed: 1968 Dijkstra : Go To Statement Considered Harmful Reason about correctness about program Nikalus Wirth : Program Development by Stepwise Refinement Not worried about program structure 1971 David Parnas : Information Distribution Aspects of Design Methodology 1972 Liskov : Design Methodology for Reliable Software Systems Extensible Language : Schuman and P Jourrand R. Balzer Structured Programming : Dahl - Hierarchical Program Structures 1971 Jim Morris Protection in Programming Languages 1973 Bill Wulf and Mary Shaw Global Variable Considered Harmful 1974 : Lisko and Zilles ADTs

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  • How do I work out IEEE 754 64-bit Floating Point Double Precision?

    - by yousef gassar
    enter code herehello i have done it in 32 but i could dont do it in 62bits please i need help I am stuck on this question and need help. I don't know how to work it out. This is the question. Below are two numbers represented in IEEE 754 64-bit Floating Point Double Precision, the bias of the signed exponent is -1023. Any particular real number ‘N’ represented in 64-bit form (i.e. with the following bit fields; 1-bit Sign, 11-bit Exponent, 52-bit Fraction) can be expressed in the form ±1.F2 × 2X by substituting the bit-field values using formula (IV.I): N = (-1) S × 1.F2 × 2(E – 1023) for 0 < E < 2047.........................….(IV.I) Where N= the number represented, S=Sign bit-value, E=Exponent=X +1023, F=Fraction or Mantissa are the values in the 1, 11 and 52-bit fields respectively in the IEEE 754 64-bit FP representation. Using formula (IV.I), express the 64-bit FP representation of each number as: (i) A binary number of the form:- ±1.F2 × 2X (ii) A decimal number of the form:- ±0.F10 × 10Y {limit F10 to 10 decimal places} Sign 0 1 Exponent 1000 0001 001 11 Fraction 1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 52 Sign 1 1 Exponent 1000 0000 000 11 Fraction 1001 0010 0001 1111 1011 0101 0100 0100 0100 0010 1101 0001 1000 52 I know I have to use the formula for each of the these but how do I work it out? Is it like this? N = (-1) S × 1.F2 × 2(E – 1023) = 1 x 1.1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 x 1000 0001 00111 (-1023)?

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  • Theory of Computation - Showing that a language is regular..

    - by Tony
    I'm reviewing some notes for my course on Theory of Computation and I'm a little bit stuck on showing the following statement and I was hoping somebody could help me out with an explanation :) Let A be a regular language. The language B = {ab | a exists in A and b does not exist in A*} Why is B a regular language? Some points are obvious to me. If b is simply a constant string, this is trivial. Since we know a is in A and b is a string, regular languages are closed under union, so unioning the language that accepts these two strings is obviously regular. I'm not sure that b is constant, however. Maybe it is, and if so, then this isn't really an issue. I'm having a hard time making sense of it. Thanks!

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  • Tablet as Car Computer

    - by Austin Fitzpatrick
    Okay, so forward this off to the right place if this isn't the right place to ask this question. I want to use a tablet computer as a car-computer. Minimum features would be to run my music (through iPod, Pandora, whatever I want) and GPS Navigation, watch TV or movies while I'm parked waiting for people, and the hard one: it needs to answer my phone calls with a pleasant interface much like in-dash systems do. It needs to detect that my phone is ringing in my pocket and provide an on-screen answer/ignore and then route the audio through the cars speakers. It would be nice to dial out and have address book access, but that is somewhat secondary. I have an iPhone myself and I figured that an iPad with 3G might make a good system for this - but I'm open to other options if an iPad can't do everything I need. I'm willing to write code, and I'm willing to jailbreak one or both devices. I haven't done much work in Obj-C, but I'm not opposed to learning a new language for this project. It's self enrichment for the most part, as I'm sure I can buy an indash entertainment system for less. Does anyone have experience with the iPhone/iPad SDK that can tell me whether or not it would be possible to get it an iPad to answer my calls in the car? What about an Android tablet? (that Adam looks promising, too).

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  • Evolutionary Algorithms: Optimal Repopulation Breakdowns

    - by Brian MacKay
    It's really all in the title, but here's a breakdown for anyone who is interested in Evolutionary Algorithms: In an EA, the basic premise is that you randomly generate a certain number of organisms (which are really just sets of parameters), run them against a problem, and then let the top performers survive. You then repopulate with a combination of crossbreeds of the survivors, mutations of the survivors, and also a certain number of new random organisms. Do that several thousand times, and efficient organisms arise. Some people also do things like introduce multiple "islands" of organisms, which are seperate populations that are allowed to crossbreed once in awhile. So, my question is: what are the optimal repopulation percentages? I have been keeping the top 10% performers, and repopulating with 30% crossbreeds and 30% mutations. The remaining 30% is for new organisms. I have also tried out the multiple island theory, and I'm interested in your results on that as well. It is not lost on me that this is exactly the type of problem an EA could solve. Are you aware of anyone trying that? Thanks in advance!

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  • Recommended Math textbooks for programmers

    - by Tony
    I learned math in a non-English environment, I recently read some books about algorithm analysis, I found some math concepts were confusing, and seemed not the same as what I've learned. What math textbooks would you recommend that covers math concepts from the scratch and suitable for self-learning ?

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  • What is a 'Closure'?

    - by Ben
    I asked a question about Currying and closures where mentioned. What is a closure? How does it relate to currying? Additional: Kyle's answer is great but to my poor procedural/OO mind Ben Childs answer is really useful.

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  • What are 'len', 'dir', 'vars' named?

    - by johannix
    I was wondering what language to use when talking about a function that takes in a specific object, acts on it and returns something else. Clearly they're functions, but I was wondering if there's a more specific term. A couple examples of Python built-in functions that fit this spec are: 'len', 'dir', 'vars' I thought it was 'predicate', but apparently that's specific to functions that return a boolean value.

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