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  • How can I transfer files to a Kindle Fire with a Micro-USB cable?

    - by Jeff
    I'm running Ubuntu 11.10, and when I connect my Kindle Fire to my computer via micro usb, it is not recognized automatically. Other usb devices, such as my ipod and digital camera, are recognized just fine. It does not appear to be a usb power issue, since the Kindle Fire wakes up from sleeping when it is plugged in. I never get the message on the Kindle telling me it is ready to accept files from the computer, though. Here are the last 15 lines of dmesg after plugging the kindle in: jeff@prime:~$ dmesg | tail -n 15 [45918.269671] ieee80211 phy0: wl_ops_bss_info_changed: arp filtering: enabled true, count 1 (implement) [45929.072149] wlan0: no IPv6 routers present [46743.224217] usb 1-1: new high speed USB device number 5 using ehci_hcd [46743.364623] scsi8 : usb-storage 1-1:1.0 [46744.366102] scsi 8:0:0:0: Direct-Access Amazon Kindle 0001 PQ: 0 ANSI: 2 [46744.366356] scsi: killing requests for dead queue [46744.372494] scsi: killing requests for dead queue [46744.384510] scsi: killing requests for dead queue [46744.392348] scsi: killing requests for dead queue [46744.392731] scsi: killing requests for dead queue [46744.396853] scsi: killing requests for dead queue [46744.397214] scsi: killing requests for dead queue [46744.400795] scsi: killing requests for dead queue [46744.401589] sd 8:0:0:0: Attached scsi generic sg2 type 0 [46744.407520] sd 8:0:0:0: [sdb] Attached SCSI removable disk And here are my mounted filesystems: jeff@prime:~$ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 298594984 174663712 108763480 62% / udev 1407684 4 1407680 1% /dev tmpfs 566924 896 566028 1% /run none 5120 0 5120 0% /run/lock none 1417308 300 1417008 1% /run/shm /home/jeff/.Private 298594984 174663712 108763480 62% /home/jeff I should note that, since I got Dropbox working on my Kindle, the usb is no longer strictly necessary, but as a matter of principle I'd love to get it working.

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  • How should I implement a command processing application?

    - by Nini Michaels
    I want to make a simple, proof-of-concept application (REPL) that takes a number and then processes commands on that number. Example: I start with 1. Then I write "add 2", it gives me 3. Then I write "multiply 7", it gives me 21. Then I want to know if it is prime, so I write "is prime" (on the current number - 21), it gives me false. "is odd" would give me true. And so on. Now, for a simple application with few commands, even a simple switch would do for processing the commands. But if I want extensibility, how would I need to implement the functionality? Do I use the command pattern? Do I build a simple parser/interpreter for the language? What if I want more complex commands, like "multiply 5 until >200" ? What would be an easy way to extend it (add new commands) without recompiling? Edit: to clarify a few things, my end goal would not be to make something similar to WolframAlpha, but rather a list (of numbers) processor. But I want to start slowly at first (on single numbers). I'm having in mind something similar to the way one would use Haskell to process lists, but a very simple version. I'm wondering if something like the command pattern (or equivalent) would suffice, or if I have to make a new mini-language and a parser for it to achieve my goals?

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  • What You Said: Cutting the Cable Cord

    - by Jason Fitzpatrick
    Earlier this week we asked you if you’d cut the cable and switched to alternate media sources to get your movie and TV fix. You responded and we’re back with a What You Said roundup. One of the recurrent themes in reader comments and one, we must admit, we didn’t expect to see with such prevalence, was the number of people who had ditched cable for over-the-air HD broadcasts. Fantasm writes: I have a triple HD antenna array, mounted on an old tv tower, each antenna facing out from a different side of the triangular tower. On tope of the tower are two 20+ year old antennas… I’m 60 miles from toronto and get 35 channels, most in brilliant HD… Anything else, comes from the Internet… Never want cable or sat again… Grant uses a combination of streaming services and, like Fantasm, manages to pull in HD content with a nice antenna setup: We use Netflix, Hulu Plus, Amazon Prime, Crackle, and others on a Roku as well as OTA on a Tivo Premier. The Tivo is simply the best DVR interface I have ever used. The Tivo Netflix application, though, is terrible, and it does not support Amazon Prime. Having both boxes makes it easy to use all of the services. 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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  • Ubuntu Desktop does not load

    - by Niklas
    If I login on my Ubuntu 14.04, I get the following desktop: This weird behavior appeared after I executed sudo apt-get update && sudo apt-get upgrade and restarted my computer. Don't know why though. To my Ubuntu I have tried the following (nothing seems to work so far) Fix any broken packages: sudo apt-get update sudo apt-get autoclean sudo apt-get clean sudo apt-get autoremove Locate any broken packages and reinstall them: sudo apt-get install debsums sudo apt-get clean sudo debsums_init sudo debsums -cs sudo apt-get install --reinstall $(sudo dpkg -S $(sudo debsums -c) | cut -d : -f 1 | sort -u) Removing some compiz files: rm -r ~/.cache/compizconfig-1 rm -r ~/.compiz Purging of NVIDIA and installing NVIDIA-prime: sudo apt-get install --reinstall ubuntu-desktop sudo apt-get install unity sudo apt-get purge nvidia* bumblebee* sudo apt-get install nvidia-prime sudo shutdown -r now Compizconfig Settings Manager: sudo apt-get install compizconfig-settings-manager export DISPLAY=:0 ccsm // Back to UI and enablement of Unity Plugin Unity replace, which stopped at a while and did nothing afterwards unity --replace Some dconf reset dconf reset -f /org/compiz/ unity --reset-icons &disown Actually dconf did not work and I got this error: error: Cannot autolaunch D-Bus without X11 $DISPLAY Can anybody help me on that? This is my hardware (hope it helps in any way): Intel® Core™ i7-3770 ASUS GTX660TI-DC2-OG-2GD5 (NVIDIA driver is/was installed) ASUS P8Z77-V LX Corsair DIMM 8 GB DDR3-1600 Kit Samsung 830series 2,5" 256 GB (Windows is installed here) Seagate ST31000524AS 1 TB (3/4 are reserved for files; 1/4 is for Ubuntu (16GB swap included))

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  • Rails: Law of Demeter Confusion

    - by user2158382
    I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • Law of Demeter confusion [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • Rails: The Law of Demeter [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • How can I be certain that my code is flawless? [duplicate]

    - by David
    This question already has an answer here: Theoretically bug-free programs 5 answers I have just completed an exercise from my textbook which wanted me to write a program to check if a number is prime or not. I have tested it and seems to work fine, but how can I be certain that it will work for every prime number? public boolean isPrime(int n) { int divisor = 2; int limit = n-1 ; if (n == 2) { return true; } else { int mod = 0; while (divisor <= limit) { mod = n % divisor; if (mod == 0) { return false; } divisor++; } if (mod > 0) { return true; } } return false; } Note that this question is not a duplicate of Theoretically Bug Free Programs because that question asks about whether one can write bug free programs in the face of the the limitative results such as Turing's proof of the incomputability of halting, Rice's theorem and Godel's incompleteness theorems. This question asks how a program can be shown to be bug free.

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  • Anything wrong with this function for comparing floats?

    - by Michael Borgwardt
    When my Floating-Point Guide was yesterday published on slashdot, I got a lot of flak for my suggested comparison function, which was indeed inadequate. So I finally did the sensible thing and wrote a test suite to see whether I could get them all to pass. Here is my result so far. And I wonder if this is really as good as one can get with a generic (i.e. not application specific) float comparison function, or whether I still missed some edge cases. import static org.junit.Assert.assertFalse; import static org.junit.Assert.assertTrue; import org.junit.Test; public class NearlyEqualsTest { public static boolean nearlyEqual(float a, float b) { final float epsilon = 0.000001f; final float absA = Math.abs(a); final float absB = Math.abs(b); final float diff = Math.abs(a-b); if (a*b==0) { // a or b or both are zero // relative error is not meaningful here return diff < Float.MIN_VALUE / epsilon; } else { // use relative error return diff / (absA+absB) < epsilon; } } /** Regular large numbers - generally not problematic */ @Test public void big() { assertTrue(nearlyEqual(1000000f, 1000001f)); assertTrue(nearlyEqual(1000001f, 1000000f)); assertFalse(nearlyEqual(10000f, 10001f)); assertFalse(nearlyEqual(10001f, 10000f)); } /** Negative large numbers */ @Test public void bigNeg() { assertTrue(nearlyEqual(-1000000f, -1000001f)); assertTrue(nearlyEqual(-1000001f, -1000000f)); assertFalse(nearlyEqual(-10000f, -10001f)); assertFalse(nearlyEqual(-10001f, -10000f)); } /** Numbers around 1 */ @Test public void mid() { assertTrue(nearlyEqual(1.0000001f, 1.0000002f)); assertTrue(nearlyEqual(1.0000002f, 1.0000001f)); assertFalse(nearlyEqual(1.0002f, 1.0001f)); assertFalse(nearlyEqual(1.0001f, 1.0002f)); } /** Numbers around -1 */ @Test public void midNeg() { assertTrue(nearlyEqual(-1.000001f, -1.000002f)); assertTrue(nearlyEqual(-1.000002f, -1.000001f)); assertFalse(nearlyEqual(-1.0001f, -1.0002f)); assertFalse(nearlyEqual(-1.0002f, -1.0001f)); } /** Numbers between 1 and 0 */ @Test public void small() { assertTrue(nearlyEqual(0.000000001000001f, 0.000000001000002f)); assertTrue(nearlyEqual(0.000000001000002f, 0.000000001000001f)); assertFalse(nearlyEqual(0.000000000001002f, 0.000000000001001f)); assertFalse(nearlyEqual(0.000000000001001f, 0.000000000001002f)); } /** Numbers between -1 and 0 */ @Test public void smallNeg() { assertTrue(nearlyEqual(-0.000000001000001f, -0.000000001000002f)); assertTrue(nearlyEqual(-0.000000001000002f, -0.000000001000001f)); assertFalse(nearlyEqual(-0.000000000001002f, -0.000000000001001f)); assertFalse(nearlyEqual(-0.000000000001001f, -0.000000000001002f)); } /** Comparisons involving zero */ @Test public void zero() { assertTrue(nearlyEqual(0.0f, 0.0f)); assertFalse(nearlyEqual(0.00000001f, 0.0f)); assertFalse(nearlyEqual(0.0f, 0.00000001f)); } /** Comparisons of numbers on opposite sides of 0 */ @Test public void opposite() { assertFalse(nearlyEqual(1.000000001f, -1.0f)); assertFalse(nearlyEqual(-1.0f, 1.000000001f)); assertFalse(nearlyEqual(-1.000000001f, 1.0f)); assertFalse(nearlyEqual(1.0f, -1.000000001f)); assertTrue(nearlyEqual(10000f*Float.MIN_VALUE, -10000f*Float.MIN_VALUE)); } /** * The really tricky part - comparisons of numbers * very close to zero. */ @Test public void ulp() { assertTrue(nearlyEqual(Float.MIN_VALUE, -Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, Float.MIN_VALUE)); assertTrue(nearlyEqual(Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, Float.MIN_VALUE)); assertFalse(nearlyEqual(Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(-Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, 0.0f)); assertFalse(nearlyEqual(0.0f, 1e20f*Float.MIN_VALUE)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, -1e20f*Float.MIN_VALUE)); } }

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  • Inline function v. Macro in C -- What's the Overhead (Memory/Speed)?

    - by Jason R. Mick
    I searched Stack Overflow for the pros/cons of function-like macros v. inline functions. I found the following discussion: Pros and Cons of Different macro function / inline methods in C ...but it didn't answer my primary burning question. Namely, what is the overhead in c of using a macro function (with variables, possibly other function calls) v. an inline function, in terms of memory usage and execution speed? Are there any compiler-dependent differences in overhead? I have both icc and gcc at my disposal. My code snippet I'm modularizing is: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = AttractiveTerm * AttractiveTerm; EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); My reason for turning it into an inline function/macro is so I can drop it into a c file and then conditionally compile other similar, but slightly different functions/macros. e.g.: double AttractiveTerm = pow(SigmaSquared/RadialDistanceSquared,3); double RepulsiveTerm = pow(SigmaSquared/RadialDistanceSquared,9); EnergyContribution += 4 * Epsilon * (RepulsiveTerm - AttractiveTerm); (note the difference in the second line...) This function is a central one to my code and gets called thousands of times per step in my program and my program performs millions of steps. Thus I want to have the LEAST overhead possible, hence why I'm wasting time worrying about the overhead of inlining v. transforming the code into a macro. Based on the prior discussion I already realize other pros/cons (type independence and resulting errors from that) of macros... but what I want to know most, and don't currently know is the PERFORMANCE. I know some of you C veterans will have some great insight for me!!

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  • Why is Java not telling me when I can't use Integer?

    - by Sebi
    For a small project (Problem 10 Project Euler) i tried to sum up all prime numbers below 2 millions. So I used a brute force method and iterated from 0 to 2'000'000 and checked if the number is a prime. If it is I added it to the sum: private int sum = 0; private void calculate() { for (int i = 0; i < 2000000; i++) { if (i.isPrime()) { sum = sum + i; } } sysout(sum) } The result of this calculation is 1179908154, but this is incorrect. So i changed int to BigInteger and now i get the correct sum 142913828922. Obviously the range of int was overflowed. But why can't Java tell my that? (e.g. by an exception)

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  • Java: omitting a data member from the equals method.

    - by cchampion
    public class GamePiece { public GamePiece(char cLetter, int nPointValue) { m_cLetter=cLetter; m_nPointValue=nPointValue; m_nTurnPlaced=0; //has not been placed on game board yet. } public char GetLetter() {return m_cLetter;} public int GetPointValue() {return m_nPointValue;} public int GetTurnPlaced() {return m_nTurnPlaced;} public void SetTurnPlaced(int nTurnPlaced) { m_nTurnPlaced=nTurnPlaced; } @Override public boolean equals(Object obj) { /*NOTE to keep this shorter I omitted some of the null checking and instanceof stuff. */ GamePiece other = (GamePiece) obj; //not case sensitive, and I don`t think we want it to be here. if(m_cLetter != other.m_cLetter) { return false; } if(m_nPointValue != other.m_nPointValue) { return false; } /* NOTICE! m_nPointValue purposely omitted. It does not affect hashcode or equals */ return true; } @Override public int hashCode() { /* NOTICE! m_nPointValue purposely omitted. It should not affect hashcode or equals */ final int prime = 41; return prime * (prime + m_nPointValue + m_cLetter); } private char m_cLetter; private int m_nPointValue; private int m_nTurnPlaced;//turn which the game piece was placed on the game board. Does not affect equals or has code! } Consider the given piece of code. This object has been immutable until the introduction of the m_nTurnPlaced member (which can be modified by the SetTurnPlaced method, so now GamePiece becomes mutable). GamePiece is used in an ArrayList, I call contains and remove methods which both rely on the equals method to be implemented. My question is this, is it ok or common practice in Java for some members to not affect equals and hashcode? How will this affect its use in my ArrayList? What type of java Collections would it NOT be safe to use this object now that it is mutable? I've been told that you're not supposed to override equals on mutable objects because it causes some collections to behave "strangely" (I read that somewhere in the java documentation).

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  • More ruby-like solution to this problem?

    - by RaouL
    I am learning ruby and practicing it by solving problems from Project Euler. This is my solution for problem 12. # Project Euler problem: 12 # What is the value of the first triangle number to have over five hundred divisors? require 'prime' triangle_number = ->(num){ (num *(num + 1)) / 2 } factor_count = ->(num) do prime_fac = Prime.prime_division(num) exponents = prime_fac.collect { |item| item.last + 1 } fac_count = exponents.inject(:*) end n = 2 loop do tn = triangle_number.(n) if factor_count.(tn) >= 500 puts tn break end n += 1 end Any improvements that can be made to this piece of code?

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  • c++ and c# speed compared

    - by Mack
    I was worried about C#'s speed when it deals with heavy calculations, when you need to use raw CPU power. I always thought that C++ is much faster than C# when it comes to calculations. So I did some quick tests. The first test computes prime numbers < an integer n, the second test computes some pandigital numbers. The idea for second test comes from here: Pandigital Numbers C# prime computation: using System; using System.Diagnostics; class Program { static int primes(int n) { uint i, j; int countprimes = 0; for (i = 1; i <= n; i++) { bool isprime = true; for (j = 2; j <= Math.Sqrt(i); j++) if ((i % j) == 0) { isprime = false; break; } if (isprime) countprimes++; } return countprimes; } static void Main(string[] args) { int n = int.Parse(Console.ReadLine()); Stopwatch sw = new Stopwatch(); sw.Start(); int res = primes(n); sw.Stop(); Console.WriteLine("I found {0} prime numbers between 0 and {1} in {2} msecs.", res, n, sw.ElapsedMilliseconds); Console.ReadKey(); } } C++ variant: #include <iostream> #include <ctime> int primes(unsigned long n) { unsigned long i, j; int countprimes = 0; for(i = 1; i <= n; i++) { int isprime = 1; for(j = 2; j < (i^(1/2)); j++) if(!(i%j)) { isprime = 0; break; } countprimes+= isprime; } return countprimes; } int main() { int n, res; cin>>n; unsigned int start = clock(); res = primes(n); int tprime = clock() - start; cout<<"\nI found "<<res<<" prime numbers between 1 and "<<n<<" in "<<tprime<<" msecs."; return 0; } When I ran the test trying to find primes < than 100,000, C# variant finished in 0.409 seconds and C++ variant in 5.553 seconds. When I ran them for 1,000,000 C# finished in 6.039 seconds and C++ in about 337 seconds. Pandigital test in C#: using System; using System.Diagnostics; class Program { static bool IsPandigital(int n) { int digits = 0; int count = 0; int tmp; for (; n > 0; n /= 10, ++count) { if ((tmp = digits) == (digits |= 1 << (n - ((n / 10) * 10) - 1))) return false; } return digits == (1 << count) - 1; } static void Main() { int pans = 0; Stopwatch sw = new Stopwatch(); sw.Start(); for (int i = 1; i <= 123456789; i++) { if (IsPandigital(i)) { pans++; } } sw.Stop(); Console.WriteLine("{0}pcs, {1}ms", pans, sw.ElapsedMilliseconds); Console.ReadKey(); } } Pandigital test in C++: #include <iostream> #include <ctime> using namespace std; int IsPandigital(int n) { int digits = 0; int count = 0; int tmp; for (; n > 0; n /= 10, ++count) { if ((tmp = digits) == (digits |= 1 << (n - ((n / 10) * 10) - 1))) return 0; } return digits == (1 << count) - 1; } int main() { int pans = 0; unsigned int start = clock(); for (int i = 1; i <= 123456789; i++) { if (IsPandigital(i)) { pans++; } } int ptime = clock() - start; cout<<"\nPans:"<<pans<<" time:"<<ptime; return 0; } C# variant runs in 29.906 seconds and C++ in about 36.298 seconds. I didn't touch any compiler switches and bot C# and C++ programs were compiled with debug options. Before I attempted to run the test I was worried that C# will lag well behind C++, but now it seems that there is a pretty big speed difference in C# favor. Can anybody explain this? C# is jitted and C++ is compiled native so it's normal that a C++ will be faster than a C# variant. Thanks for the answers!

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  • List of divisors of an integer n (Haskell)

    - by Code-Guru
    I currently have the following function to get the divisors of an integer: -- All divisors of a number divisors :: Integer -> [Integer] divisors 1 = [1] divisors n = firstHalf ++ secondHalf where firstHalf = filter (divides n) (candidates n) secondHalf = filter (\d -> n `div` d /= d) (map (n `div`) (reverse firstHalf)) candidates n = takeWhile (\d -> d * d <= n) [1..n] I ended up adding the filter to secondHalf because a divisor was repeating when n is a square of a prime number. This seems like a very inefficient way to solve this problem. So I have two questions: How do I measure if this really is a bottle neck in my algorithm? And if it is, how do I go about finding a better way to avoid repetitions when n is a square of a prime?

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  • How to find the largest square in the number (Java)

    - by Ypsilon IV
    Hello everyone, I want to find the largest square in the number, but I am stuck at some point. I would really appreciate some suggestions. This is what I've done so far: I take the number on the input, factorize into prime numbers, and put the sequence of prime numbers to ArrayList. Numbers are sorted, in a sense, thus the numbers in the sequence are increasing. For example, 996 is 2 2 3 83 1000 is 2 2 2 5 5 5 100000 is 2 2 2 2 2 5 5 5 5 5 My idea now is to count number of occurrences of each elements in the sequence, so if the number of occurrences is divisible by two, then this is the square. In this way, I can get another sequence, where the right most element divisible by two is the largest square. What is the most efficient way to count occurrences in the ArrayList? Or is there any better way to find the largest square? Many thanks in advance!

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  • Split text files Accross threads

    - by Kevin
    The problem: I have a few text files (10) with numbers in them on every line. I need to have them split across some threads I create using the pthread library. these threads that are created (worker threads) are to find the largest prime number that gets sent to them (and over all the largest prime from all of the text files). My current thoughts on solutions: I am thinking myself to have two arrays and all of the text files in one array and the other array will contain a binary file that I can read say 1000 lines and send the pointer to the index of that binary file in a struct that contains the id, file pointer, and file position and let it crank through that. a little bit of what I am talking about pthread_create(&threads[index],NULL,calc_sqrt,(void *)threadFields[index]);//Pass struct to each worker Struct: typedef struct threadFields{ int *id, *position; FILE *Fin; }tField; If anyone has any insight or a better solution it would be greatly appreciated Thanks

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  • Différence entre :before et ::before, les pseudos-element en CSS3 par Louis Lazaris, traduit par Jérôme Debray

    Lorsquevous faites une recherche sur les pseudo-éléments en CSS, vous pouvez constater différentes syntaxes pour :before et :after, précédés de deux-points doublés (::) ou non. Cela peut sembler un peu déroutant de prime abord mais il y a, en fait, une explication plutôt simple. J'avais supposé qu'il y avait une différence de fonctionnement entre les deux types de syntaxe, mais ce n'est pas le cas comme le montre, ci dessous, les explications courte et longue.

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  • Ubuntu 14.04 Nvidia Optimus Bumblebee error

    - by Cristian
    I know that in Ubuntu 14.04 there exists nvidia-prime for Nvidia Optimus, but I don't like it and neither am I able to get it work. After upgrading from Ubuntu 12.04 everything crashed, and I made a clean install of Ubuntu 14.04 and Bumblebee, but now I have new troubles. After running optirun glxgears I get the following error: **[ 4703.996785] [ERROR]Cannot access secondary GPU, secondary X is not active.** **[ 4703.996910] [ERROR]Aborting because fallback start is disabled.** Please help.

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  • How Do Colors Influence Web Design?

    Colors hold prime importance in any web design. Colors are what add visual vibrancy to the design and layout of the website. In fact, a website without colors looks plain and bland and seldom appeals... [Author: Kabir Bedi - Web Design and Development - April 05, 2010]

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