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  • "EXC_BAD_ACCESS: Unable to restore previously selected frame" Error, Array size?

    - by Job
    Hi there, I have an algorithm for creating the sieve of Eratosthenes and pulling primes from it. It lets you enter a max value for the sieve and the algorithm gives you the primes below that value and stores these in a c-style array. Problem: Everything works fine with values up to 500.000, however when I enter a large value -while running- it gives me the following error message in xcode: Program received signal: “EXC_BAD_ACCESS”. warning: Unable to restore previously selected frame. Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.) My first idea was that I didn't use large enough variables, but as I am using 'unsigned long long int', this should not be the problem. Also the debugger points me to a point in my code where a point in the array get assigned a value. Therefore I wonder is there a maximum limit to an array? If yes: should I use NSArray instead? If no, then what is causing this error based on this information? EDIT: This is what the code looks like (it's not complete, for it fails at the last line posted). I'm using garbage collection. /*--------------------------SET UP--------------------------*/ unsigned long long int upperLimit = 550000; // unsigned long long int sieve[upperLimit]; unsigned long long int primes[upperLimit]; unsigned long long int indexCEX; unsigned long long int primesCounter = 0; // Fill sieve with 2 to upperLimit for(unsigned long long int indexA = 0; indexA < upperLimit-1; ++indexA) { sieve[indexA] = indexA+2; } unsigned long long int prime = 2; /*-------------------------CHECK & FIND----------------------------*/ while(!((prime*prime) > upperLimit)) { //check off all multiples of prime for(unsigned long long int indexB = prime-2; indexB < upperLimit-1; ++indexB) { // Multiple of prime = 0 if(sieve[indexB] != 0) { if(sieve[indexB] % prime == 0) { sieve[indexB] = 0; } } } /*---------------- Search for next prime ---------------*/ // index of current prime + 1 unsigned long long int indexC = prime - 1; while(sieve[indexC] == 0) { ++indexC; } prime = sieve[indexC]; // Store prime in primes[] primes[primesCounter] = prime; // This is where the code fails if upperLimit > 500000 ++primesCounter; indexCEX = indexC + 1; } As you may or may not see, is that I am -very much- a beginner. Any other suggestions are welcome of course :)

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  • Why is my implementation of the Sieve of Atkin overlooking numbers close to the specified limit?

    - by Ross G
    My implementation either overlooks primes near the limit or composites near the limit. while some limits work and others don't. I'm am completely confused as to what is wrong. def AtkinSieve (limit): results = [2,3,5] sieve = [False]*limit factor = int(math.sqrt(lim)) for i in range(1,factor): for j in range(1, factor): n = 4*i**2+j**2 if (n <= lim) and (n % 12 == 1 or n % 12 == 5): sieve[n] = not sieve[n] n = 3*i**2+j**2 if (n <= lim) and (n % 12 == 7): sieve[n] = not sieve[n] if i>j: n = 3*i**2-j**2 if (n <= lim) and (n % 12 == 11): sieve[n] = not sieve[n] for index in range(5,factor): if sieve[index]: for jndex in range(index**2, limit, index**2): sieve[jndex] = False for index in range(7,limit): if sieve[index]: results.append(index) return results For example, when I generate a primes to the limit of 1000, the Atkin sieve misses the prime 997, but includes the composite 965. But if I generate up the limit of 5000, the list it returns is completely correct.

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  • Why is my implementation of the Sieve of Atkin overlooking numbers close to the specified limit?

    - by Ross G
    My implementation either overlooks primes near the limit or composites near the limit. while some limits work and others don't. I'm am completely confused as to what is wrong. def AtkinSieve (limit): results = [2,3,5] sieve = [False]*limit factor = int(math.sqrt(lim)) for i in range(1,factor): for j in range(1, factor): n = 4*i**2+j**2 if (n <= lim) and (n % 12 == 1 or n % 12 == 5): sieve[n] = not sieve[n] n = 3*i**2+j**2 if (n <= lim) and (n % 12 == 7): sieve[n] = not sieve[n] if i>j: n = 3*i**2-j**2 if (n <= lim) and (n % 12 == 11): sieve[n] = not sieve[n] for index in range(5,factor): if sieve[index]: for jndex in range(index**2, limit, index**2): sieve[jndex] = False for index in range(7,limit): if sieve[index]: results.append(index) return results For example, when I generate a primes to the limit of 1000, the Atkin sieve misses the prime 997, but includes the composite 965. But if I generate up the limit of 5000, the list it returns is completely correct.

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  • How do I EFI boot Zenbook Prime UX31A from built-in card reader?

    - by Richard Ayotte
    How do I EFI boot Zenbook Prime UX31A from built-in card reader? Ubuntu 12.10 64bit has been copied onto an a SD card which I'm trying to boot from. When I power on my Zenbook and press ESC, the SD card isn't an option. There is an "Add boot option" in the BIOS but it requires a few a things that I'm not quite sure of. Add boot option - I guess any identifier works here. I've been entering ubuntu. Select Filesystem - The only option available is PCI(1F|2)\DevicePath(Type 3, SubType 12)HD(Part1,Sig787e6287-xxxx-xxxx-xxxx-xxxxxxxxxxxx) Path for boot option - I've been entering ubuntu:\EFI\BOOT\BOOTx64.EFI Then I select Create and the new boot option appears in the boot menu but it doesn't work.

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  • Can't find the error in my javascript code

    - by Olivier
    This js program should display the first 100 prime numbers, but instead it crashes each and every time and I can't find the error! Could someone point me towards the best way to debug js code?! Thank you! // initialisation of the array p holding the first 100 prime numbers var p = []; // set the first prime number to 2 p.push(2); // find the first 100 prime numbers and place them in the array p var i = 3; while (p.length < 100) { var prime = true; loop: for (var item in p){ if (i%item === 0){ prime = false; break loop; } } if (prime) p.push(i); i = i + 2; } // display the first 100 prime numbers found var i=1; for (var item in p){ document.writeln(i,item); i++; }

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  • Where to install boot loader on a Zenbook Prime?

    - by Christians
    I cannot figure out where to install the boot loader on my Zenbook UX31A Prime. I have installed Ubuntu many times on normal hard drives, but this is the first SSD and I am struggling. Installed Ubuntu 12.04 64-bit selecting "UEFI: general" boot entry. Installation type: Something Else Created partition /sda5 mount as /, /sda6 mount as /home, /sda7 mount as swap Selected /dev/sda for boot loader installation. Other options are /dev/sda, /dev/sda1/dev/sda3 Windows 7 (loader) ... Grub comes up with 6 entries Ubuntu - this runs great Linux 3.2.0-29-generic recovery mode: mode hangs with "fb: conflicting fb hw usae interdrnfb vs EFI VGA - removing generic adapter" memtest86:erro: unknown command `linux 16' memtest86 serial: unknown command `linux 16' Windows 7 (loader) (on /dev/sda3): invalid EFI file path Windows Recovery Environment (on /dev/sda8): unknown command drivemap, invalid EFI file path. My workaround for booting Windows 7 is hitting ESC during boot, windows boot manager comes up and * for booting into Windows 7 I select "WIndows Boot Manager (PO: SanDisk ....". * for booting into Ubuntu I select ubuntu (P0: SanDisk...) How can I boot into Windows from Grub?

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  • Determine if a number is a prime with regex?

    - by kitlite
    I found the following code example for Java on RosettaCode: public static boolean prime(int n) { return !new String(new char[n]).matches(".?|(..+?)\\1+"); } I don't know Java in particular but understand all aspects of this snippet except for the regex itself I have basic to basic-advanced knowledge of Regex as you find it in the built-in PHP functions How does .?|(..+?)\\1+ match prime numbers?

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  • Why is my "Page [0]" not centered in my webpage?

    - by William
    My "Page [0]" text isn't centered on my webpage. Anyone know why? I could really use some help please. Here is the html: <html> <head> <title>Test Forum</title> <link href="http://prime.programming-designs.com/test_forum/style.css" rel="stylesheet" type="text/css" /> </head> <body> <a href="http://prime.programming-designs.com/test_forum/"><img src="http://prime.programming-designs.com/test_forum//images/banner1.png" alt="" id="banner" /></a> <h1>Test Forums</h1> <hr /> <div id="navi"><div id="naviheader">Boards</div><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=0">Testing</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=1">General Discussion</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=2">Video Games</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=3">Anime and Manga</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=4">BlazBlue</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=5">Shin Megami Tensei</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=6">Earthbound</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=7">Phantasy Star</a><br /><a href="http://prime.programming-designs.com/test_forum/viewboard.php?board=8">Mobile Suit Gundam</a><br /></div> <div class="postbox"><h4>CyanPrime</h4><hr />Welcome to the King's Gate BBS!</div>Page: [<a href="http://prime.programming-designs.com/test_forum/index.php?page=0">0</a>] </body> </html> Here is the CSS: @charset "windows-1252"; body{ background-color: #EEFFF8; color: #000000; text-align: center; } .postbox{ text-align: left; margin: auto; background-color: #dbfef8; border: 1px solid #82FFCD; width: 50%; margin-top: 10px; } .stickypostbox{ text-align: left; margin: auto; background-color: #F5FFFA; border: 1px solid #82FFCD; width: 50%; margin-top: 10px; } h4{ margin: 0px 0px 0px 0px; padding: 0px 0px 0px 0px; color: #9932CC; } h1{ color: #551A8B; } hr{ color: #82FFCD; background-color: #82FFCD; height: 1px; border: 0px dotted #82FFCD; } a{ color: #7F00FF; text-decoration: none; } a:hover{ color: #7F00FF; text-decoration: underline; } form{ margin: 0px auto; width: 50%; } #formdiv { background-color:#dbfef8; border:1px solid #82FFCD; } .fielddiv1{ background-color: #f9f9f9; border: 1px solid #DBFEF8; vertical-align: middle; width: 45%; float: left; } .fielddiv2{ background-color: #f9f9f9; border: 1px solid #DBFEF8; vertical-align: middle; width: 100%; } .fieldtext1{ width: 50%; background-color: #82FFCD; float: left; } .fieldtext2{ width: 100%; background-color: #82FFCD; } #replydiv{ width: 100%; background-color: #DBFEF8; margin: 10px 0 10px 0; } #admindiv{ width: 100%; background-color: #DBFEF8; margin: 10px 0 10px 0; } #navi{ width: 200px; background-color: #dbfef8; border: 1px solid #82FFCD; text-align: left; float: left; } #naviheader{ width: 100%; background-color: #82FFCD; } #submitbutton{ border: 1px solid #82FFCD; background-color: #DBFEF8; color: #000000; margin-top: 5px; width: 100px; height: 20px; } #banner{ border: 1px solid #82FFCD; } .postbar{ margin-right: 0px; margin-top: 0px; } .bannedtext{ margin: 0px 0px 0px 0px; padding: 0px 0px 0px 0px; color: #FF0000; } And here is the webpage so you can get some context (you'll notice that my "page [0]" is centered on the other boards, but not the index. http://prime.programming-designs.com/test_forum/

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  • output with "Private`" Content in Mathematica Package

    - by madalina
    Hello everyone, I am trying to solve the following implementation problem in Mathematica 7.0 for some days now and I do not understand exactly what is happening so I hope someone can give me some hints. I have 3 functions that I implemented in Mathematica in a source file with extension *.nb. They are working okay to all the examples. Now I want to put these functions into 3 different packages. So I created three different packages with extension .*m in which I put all the desired Mathematica function. An example in the "stereographic.m" package which contain the code: BeginPackage["stereographic`"] stereographic::usage="The package stereographic...." formEqs::usage="The function formEqs[complexBivPolyEqn..." makePoly::usage="The function makePoly[algebraicEqn] ..." getFixPolys::usage="The function..." milnorFibration::usage="The function..." Begin["Private`"] Share[]; formEqs[complex_,{m_,n_}]:=Block[{complexnew,complexnew1, realeq, imageq, expreal, expimag, polyrealF, polyimagF,s,t,u,v,a,b,c,epsilon,x,y,z}, complexnew:=complex/.{m->s+I*t,n->u+I*v}; complexnew1:=complexnew/.{s->(2 a epsilon)/(1+a^2+b^2+c^2),t->(2 b epsilon)/(1+a^2+b^2+c^2),u->(2 c epsilon)/(1+a^2+b^2+c^2),v->(- epsilon+a^2 epsilon+b^2 epsilon+c^2 epsilon)/(1+a^2+b^2+c^2)}; realeq:=ComplexExpand[Re[complexnew1]]; imageq:=ComplexExpand[Im[complexnew1]]; expreal:=makePoly[realeq]; expimag:=makePoly[imageq]; polyrealF:=expreal/.{a->x,b->y,c->z}; polyimagF:=expimag/.{a->x,b->y,c->z}; {polyrealF,polyimagF} ] End[] EndPackage[] Now to test the function I load the package Needs["stereographic`"] everything is okay. But when I test the function for example with formEqs[x^2-y^2,{x,y}] I get the following ouput: {Private`epsilon^2 + 2 Private`x^2 Private`epsilon^2 + Private`x^4 Private`epsilon^2 - 6 Private`y^2 Private`epsilon^2 + 2 Private`x^2 Private`y^2 Private`epsilon^2 + Private`y^4 Private`epsilon^2 - 6 Private`z^2 Private`epsilon^2 + 2 Private`x^2 Private`z^2 Private`epsilon^2 + 2 Private`y^2 Private`z^2 Private`epsilon^2 + Private`z^4 Private`epsilon^2, 8 Private`x Private`y Private`epsilon^2 + 4 Private`z Private`epsilon^2 - 4 Private`x^2 Private`z Private`epsilon^2 - 4 Private`y^2 Private`z Private`epsilon^2 - 4 Private`z^3 Private`epsilon^2} Of course I do not understand why Private` appears in front of any local variable which I returned in the final result. I would want not to have this Private` in the computed output. Any idea or better explanations which could indicate me why this happens? Thank you very much for your help. Best wishes, madalina

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  • Tab Sweep - Java EE wins, Prime Faces JSF, NetBeans, Jelastic for GlassFish, BeanValidation, Ewok and more...

    - by alexismp
    Recent Tips and News on Java, Java EE 6, GlassFish & more : • PrimeFaces 3.2 Final Released (primefaces.org) • Java EE wins over Spring (Bill Burke) • Customizing Components in JSF 2.0 (Mr. Bool) • Key to the Java EE 6 Platform: NetBeans IDE 7.1.x (OTN) • How to use GlassFish’s Connection Pool in Jelastic (jelastic.com) • Bean Validation 1.1 early draft 1 is out - time for feedback (Emmanuel) • Code artifacts published for Bean Validation 1.1 early draft 1 (Emmanuel) • Aprendendo Java EE 6 com GlassFish 3 e NetBeans 7.1 (Marcello) • JavaEE6 and the Ewoks (Murat)

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  • Project Euler: Programmatic Optimization for Problem 7?

    - by bmucklow
    So I would call myself a fairly novice programmer as I focused mostly on hardware in my schooling and not a lot of Computer Science courses. So I solved Problem 7 of Project Euler: By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the 10001st prime number? I managed to solve this without problem in Java, but when I ran my solution it took 8 and change seconds to run. I was wondering how this could be optimized from a programming standpoint, not a mathematical standpoint. Is the array looping and while statements the main things eating up processing time? And how could this be optimized? Again not looking for a fancy mathematical equation..there are plenty of those in the solution thread. SPOILER My solution is listed below. public class PrimeNumberList { private ArrayList<BigInteger> primesList = new ArrayList<BigInteger>(); public void fillList(int numberOfPrimes) { primesList.add(new BigInteger("2")); primesList.add(new BigInteger("3")); while (primesList.size() < numberOfPrimes){ getNextPrime(); } } private void getNextPrime() { BigInteger lastPrime = primesList.get(primesList.size()-1); BigInteger currentTestNumber = lastPrime; BigInteger modulusResult; boolean prime = false; while(!prime){ prime = true; currentTestNumber = currentTestNumber.add(new BigInteger("2")); for (BigInteger bi : primesList){ modulusResult = currentTestNumber.mod(bi); if (modulusResult.equals(BigInteger.ZERO)){ prime = false; break; } } if(prime){ primesList.add(currentTestNumber); } } } public BigInteger get(int primeTerm) { return primesList.get(primeTerm - 1); } }

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  • Effective java hashcode implementation

    - by Scobal
    I was wondering if someone could explain in detail what (int)(l ^ (l >>> 32)); does in the following hashcode implementation (generated by eclipse, but the same as Effective Java): private int i; private char c; private boolean b; private short s; private long l; private double d; private float f; @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + i; result = prime * result + s; result = prime * result + (b ? 1231 : 1237); result = prime * result + c; long t = Double.doubleToLongBits(d); result = prime * result + (int) (t ^ (t >>> 32)); result = prime * result + Float.floatToIntBits(f); result = prime * result + (int) (l ^ (l >>> 32)); return result; } Thanks!

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  • Project Euler #3

    - by Alex
    Question: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143? I found this one pretty easy, but running the file took an extremely long time, it's been going on for a while and the highest number I've got to is 716151937. Here is my code, am I just going to have a wait or is there an error in my code? //User made class public class Three { public static boolean checkPrime(long p) { long i; boolean prime = false; for(i = 2;i<p/2;i++) { if(p%i==0) { prime = true; break; } } return prime; } } //Note: This is a separate file public class ThreeMain { public static void main(String[] args) { long comp = 600851475143L; boolean prime; long i; for(i=2;i<comp/2;i++) { if(comp%i==0) { prime = Three.checkPrime(i); if(prime==true) { System.out.println(i); } } } } }

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  • Why should the "prime-based" hashcode implmentation be used instead of the "naive" one?

    - by Wilhelm
    I have seen that a prime number implmentation of the GetHashCode function is being recommend, for example here. However using the following code (in VB, sorry), it seems as if that implementation gives the same hash density as a "naive" xor implementation. If the density is the same, I would suppose there is the same probability of cllision in both implementations. Am I missing anything on why is the prime approach preferred? I am supossing that if the hash code is a byte I do not lose generality for the integer case. Sub Main() Dim XorHashes(255) As Integer Dim PrimeHashes(255) As Integer For i = 0 To 255 For j = 0 To 255 For k = 0 To 255 XorHashes(GetXorHash(i, j, k)) += 1 PrimeHashes(GetPrimeHash(i, j, k)) += 1 Next Next Next For i = 0 To 255 Console.WriteLine("{0}: {1}, {2}", i, XorHashes(i), PrimeHashes(i)) Next Console.ReadKey() End Sub Public Function GetXorHash(ByVal valueOne As Integer, ByVal valueTwo As Integer, ByVal valueThree As Integer) As Byte Return CByte((valueOne Xor valueTwo Xor valueThree) Mod 256) End Function Public Function GetPrimeHash(ByVal valueOne As Integer, ByVal valueTwo As Integer, ByVal valueThree As Integer) As Byte Dim TempHash = 17 TempHash = 31 * TempHash + valueOne TempHash = 31 * TempHash + valueTwo TempHash = 31 * TempHash + valueThree Return CByte(TempHash Mod 256) End Function

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  • Interview question : What is the fastest way to generate prime number recursively ?

    - by hilal
    Generation of prime number is simple but what is the fastest way to find it and generate( prime numbers) it recursively ? Here is my solution. However, it is not the best way. I think it is O(N*sqrt(N)). Please correct me, if I am wrong. public static boolean isPrime(int n) { if (n < 2) { return false; } else if (n % 2 == 0 & n != 2) { return false; } else { return isPrime(n, (int) Math.sqrt(n)); } } private static boolean isPrime(int n, int i) { if (i < 2) { return true; } else if (n % i == 0) { return false; } else { return isPrime(n, --i); } } public static void generatePrimes(int n){ if(n < 2) { return ; } else if(isPrime(n)) { System.out.println(n); } generatePrimes(--n); } public static void main(String[] args) { generatePrimes(200); }

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  • C/C++: Passing a structure by value, with another structure as one of its members, changes values of

    - by jellyfisharepretty
    Sorry for the confusing title, but it basically says it all. Here's the structures I'm using (found in OpenCV) : struct CV_EXPORTS CvRTParams : public CvDTreeParams { bool calc_var_importance; int nactive_vars; CvTermCriteria term_crit; CvRTParams() : CvDTreeParams( 5, 10, 0, false, 10, 0, false, false, 0 ), calc_var_importance(false), nactive_vars(0) { term_crit = cvTermCriteria( CV_TERMCRIT_ITER+CV_TERMCRIT_EPS, 50, 0.1 ); } } and typedef struct CvTermCriteria { int type; int max_iter; double epsilon; } CvTermCriteria; CV_INLINE CvTermCriteria cvTermCriteria( int type, int max_iter, double epsilon ) { CvTermCriteria t; t.type = type; t.max_iter = max_iter; t.epsilon = (float)epsilon; return t; } Now, I initialize a CvRTParams structure and set values for its members : CvRTParams params; params.max_depth = 8; params.min_sample_count = 10; params.regression_accuracy = 0; params.use_surrogates = false; params.max_categories = 10; params.priors = priors; params.calc_var_importance = true; params.nactive_vars = 9; params.term_crit.max_iter = 33; params.term_crit.epsilon = 0.1; params.term_crit.type = 3; Then call a function of an object, taking params in as a parameter : CvRTrees* rt = new CvRTrees; rt->train(t, CV_ROW_SAMPLE, r, 0, 0, var_type, 0, params) What happens now ? Values of... params.term_crit.max_iter params.term_crit.epsilon params.term_crit.type have changed ! They are no longer 33, 0.1 and 3, but something along the lines of 3, 7.05541e-313 and 4, and this, for the whole duration of the CvRtrees::train() function...

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  • Removing words from a file

    - by user1765792
    I'm trying to take a regular text file and remove words identified in a separate file (stopwords) containing the words to be removed separated by carriage returns ("\n"). Right now I'm converting both files into lists so that the elements of each list can be compared. I got this function to work, but it doesn't remove all of the words I have specified in the stopwords file. Any help is greatly appreciated. def elimstops(file_str): #takes as input a string for the stopwords file location stop_f = open(file_str, 'r') stopw = stop_f.read() stopw = stopw.split('\n') text_file = open('sample.txt') #Opens the file whose stop words will be eliminated prime = text_file.read() prime = prime.split(' ') #Splits the string into a list separated by a space tot_str = "" #total string i = 0 while i < (len(stopw)): if stopw[i] in prime: prime.remove(stopw[i]) #removes the stopword from the text else: pass i += 1 # Creates a new string from the compilation of list elements # with the stop words removed for v in prime: tot_str = tot_str + str(v) + " " return tot_str

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  • When can Java produce a NaN (with specific code question)

    - by Brent
    I'm a bit perplexed by some code I'm currently writing. I am trying to preform a specific gradient descent (main loop included below) and depending on the initial conditions I will alternatively get good looking results (perhaps 20% of the time) or everything becomes NaN (the other 80% of the time). However it seems to me that none of the operations in my code could produce NaN's when given honest numbers! My main loop is: // calculate errors delta = m1 + m2 - M; eta = f1 + f2 - F; for (int i = 0; i < numChildren; i++) { epsilon[i] = p[i]*m1+(1-p[i])*m2+q[i]*f1+(1-q[i])*f2-C[i]; } // use errors in gradient descent // set aside differences for the p's and q's float mDiff = m1 - m2; float fDiff = f1 - f2; // first update m's and f's m1 -= rate*delta; m2 -= rate*delta; f1 -= rate*eta; f2 -= rate*eta; for (int i = 0; i < numChildren; i++) { m1 -= rate*epsilon[i]*p[i]; m2 -= rate*epsilon[i]*(1-p[i]); f1 -= rate*epsilon[i]*q[i]; f2 -= rate*epsilon[i]*(1-q[i]); } // now update the p's and q's for (int i = 0; i < numChildren; i++) { p[i] -= rate*epsilon[i]*mDiff; q[i] -= rate*epsilon[i]*fDiff; } This behavior can be seen when we have rate = 0.01; M = 30; F = 30; C = {15, 25, 35, 45}; with the p[i] and q[i] chosen randomly uniformly between 0 and 1, m1 and m2 chosen randomly uniformly to add to M, and f1 and f2 chosen randomly uniformly to add up to F. Does anyone see anything that could create these NaN's?

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  • [0-9a-zA-Z]* string expressed with primes or prime-factorization-style way to break it into parts?

    - by HH
    Suppose a string consists of numbers and alphabets. You want to break it into parts, an analogy is primes' factorization, but how can you do similar thing with strings [0-9a-zA-Z]* or even with arbitrary strings? I could express it in alphabets and such things with octal values and then prime-factorize it but then I need to keep track of places where I had the non-numbers things. Is there some simple way to do it? I am looking for simple succinct solutions and don't want too much side-effects. [Update] mvds has the correct idea, to change the base, how would you implement it?

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  • Count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers such that all numbers are co-prime to 'C'

    - by rajneesh2k10
    I came across the solution of a problem which involve dynamic-programming approach, solved using a three dimensional matrix. Link to actual problem is: http://community.topcoder.com/stat?c=problem_statement&pm=12189&rd=15177 Solution to this problem is here under MuddyRoad2: http://apps.topcoder.com/wiki/display/tc/SRM+555 In the last paragraph of explanation, author describes a dynamic programming approach to count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers (not necessarily different), such that every number is co-prime to 3 and the order in which these numbers appear does matter. I am not able to grasp that approach. Can anyone help me understand how DP is acting here. I can't understand what is a state here and how it is derived from the previous state.

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  • Project Euler 10: (Iron)Python

    - by Ben Griswold
    In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 10.  As always, any feedback is welcome. # Euler 10 # http://projecteuler.net/index.php?section=problems&id=10 # The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. # Find the sum of all the primes below two million. import time start = time.time() def primes_to_max(max): primes, number = [2], 3 while number < max: isPrime = True for prime in primes: if number % prime == 0: isPrime = False break if (prime * prime > number): break if isPrime: primes.append(number) number += 2 return primes primes = primes_to_max(2000000) print sum(primes) print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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  • Most Elegant Way to write isPrime in java

    - by Anantha Kumaran
    public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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