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Search found 1848 results on 74 pages for 'algorithms'.

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  • Finding the width of a directed acyclic graph... with only the ability to find parents

    - by Platinum Azure
    Hi guys, I'm trying to find the width of a directed acyclic graph... as represented by an arbitrarily ordered list of nodes, without even an adjacency list. The graph/list is for a parallel GNU Make-like workflow manager that uses files as its criteria for execution order. Each node has a list of source files and target files. We have a hash table in place so that, given a file name, the node which produces it can be determined. In this way, we can figure out a node's parents by examining the nodes which generate each of its source files using this table. That is the ONLY ability I have at this point, without changing the code severely. The code has been in public use for a while, and the last thing we want to do is to change the structure significantly and have a bad release. And no, we don't have time to test rigorously (I am in an academic environment). Ideally we're hoping we can do this without doing anything more dangerous than adding fields to the node. I'll be posting a community-wiki answer outlining my current approach and its flaws. If anyone wants to edit that, or use it as a starting point, feel free. If there's anything I can do to clarify things, I can answer questions or post code if needed. Thanks! EDIT: For anyone who cares, this will be in C. Yes, I know my pseudocode is in some horribly botched Python look-alike. I'm sort of hoping the language doesn't really matter.

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  • Standard term for a thread I/O reorder buffer?

    - by Crashworks
    I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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  • Selecting item from set given distribution

    - by JH
    I have a set of X items such as {blower, mower, stove} and each item has a certain percentage of times it should be selected from the overall set {blower=25%,mower=25%,stove=75%} along with a certain distribution that these items should follow (blower should be selected more at the beginning of selection and stove more at the end). We are given a number of objects to be overall selected (ie 100) and a overall time to do this in (say 100 seconds). I was thinking of using a roulette wheel algorithm where the weights on the wheel are affected by the current distribution as a function of the elapsed time (and the allowed duration) so that simple functions could be used to determine the weight. Are there any common approaches to problems like this that anyone is aware of? Currently i have programmed something similar to this in java using functions such as x^2 (with correct normalization for the weights) to ensure that a good distribution occurs. Other suggestions or common practices would be welcome :-)

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  • help implementing algorithm

    - by davit-datuashvili
    http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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  • How to implement B+ Tree for file systems ?

    - by user312544
    I have a text file which contains some info on extents about all the files in the file system, like below C:\Program Files\abcd.txt 12345 100 23456 200 C:\Program Files\bcde.txt 56789 50 26746 300 ... Now i have another binary which tries to find out about extents for all the files. Now currently i am using linear search to find extent info for the files in the above mentioned text file. This is a time consuming process. Is there a better way of coding this ? Like Implementing any good data structure like BTree. If B+ Tree is used what is the key, branch factor i need to use ?

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  • delete item from array in java

    - by davit-datuashvili
    hello can anybody tell me what is wrong here? i want delete item from array but it shows me error ArrayIndexOutBound exception public class delete{ public static void main(String[]args){ int i; //delete item from array int k[]=new int[]{77,99,44,11,00,55,66,33,10}; //delete 55 int searchkey=55; int nums=k.length; for ( i=0;i<nums;i++) if (k[i]==searchkey) break; for (int t=i;t<nums;t++) k[t]=k[t+1]; nums--; for (int m=0;m<nums;m++){ System.out.println(k[m]); } } }

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  • Looking for advice on how to do some bit-twiddling [closed]

    - by davit-datuashvili
    hi everybody fisrt of all this is not homework and now question is like this suppose i have array int a[]=new int[]{0xBCDA,0xABFE,0xBCAD,0xEFCA,0xFFCA} i know that there is always some hexadecimal number which occurs in all number or in this case A is repeat in array everywhere so my aim is print only repeat number and other numbers should be zero so my new array should be like this 0x000A, 0xA000,0x00A0 0x000A,0x000A any idea please help me? p.s please nobody say that this is homework

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  • help implementing All Nearest Smaller Values algorithm

    - by davit-datuashvili
    http://en.wikipedia.org/wiki/All_nearest_smaller_values this is site of the problem and here is my code but i have some trouble to implement it import java.util.*; public class stack{ public static void main(String[]args){ int x[]=new int[]{ 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15 }; Stack<Integer> st=new Stack<Integer>(); for (int a:x){ while (!st.empty() && st.pop()>=a){ System.out.println( st.pop()); if (st.empty()){ break; } else{ st.push(a); } } } } } and here is pseudo code from site S = new empty stack data structure for x in the input sequence: while S is nonempty and the top element of S is greater than or equal to x: pop S if S is empty: x has no preceding smaller value else: the nearest smaller value to x is the top element of S push x onto S

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  • Complexity in using Binary search and Trie

    - by user121196
    given a large list of alphabetically sorted words in a file,I need to write a program that, given a word x, determines if x is in the list. Preprocessing is ok since I will be calling this function many times over different inputs. priorties: 1. speed. 2. memory I already know I can use (n is number of words, m is average length of the words) 1. a trie, time is O(log(n)), space(best case) is O(log(n*m)), space(worst case) is O(n*m). 2. load the complete list into memory, then binary search, time is O(log(n)), space is O(n*m) I'm not sure about the complexity on tri, please correct me if they are wrong. Also are there other good approaches?

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  • What is the most efficient algorithm for reversing a String in Java?

    - by Hultner
    I am wondering which way to reverse a string in Java that is most efficient. Should I use some sort of xor method? The easy way would be to put all the chars in a stack and put them back into a string again but I doubt that's a very efficient way to do it. And please do not tell me to use some built in function in Java. I am interested in learning how to do it not to use an efficient function but not knowing why it's efficient or how it's built up.

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  • bit count in array

    - by davit-datuashvili
    hello i have following question i know that to count number of set bit in number of number of 1 bit there is following code int t ;//in which we want count how many bit are set for instance 3 011 there is 2 bit set int count=0; while(t>0){ t&=(t-1); count++; } now let take array example int x[]={3,5,6,8,9,7}; i have following code int sum=0; int count; for (int i=0;i<x.length;i++){ count=0; while (x[i]>0){ x[i]&=(x[i]-1); count++; } sum+=count; } I have question what is wrong? it doesn't work doesn't show me result;

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  • Heap property of this array

    - by davit-datuashvili
    From programming pearls, it is known that array[1...n] has heap property if for all 2<=i<=n x[i/2]<=x[i]. Here is my code: import java.math.*; public class Heap { public static void main(String[]args){ int x[]=new int[]{12,20,15,29,23,17,22,35,40,26,51,19}; int i=1; while (i<x.length) { if (x[Math.round(i/2)]<=x[i]) System.out.println("heap"); i++; } System.out.println("not heap"); } } Here I used Math.round because 4/2 and 5/2 is same and =2. When I compile this code it shows me at last line that it is not heap. Maybe because the index starts from 1 and we don't pay attention to index 0, yes?

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  • partition from programming pearls

    - by davit-datuashvili
    hi suppose i have following array int a[]=new int[]{55,41,59,26,53,58,97,93}; i want to partition it around 55 so new array will be such } 41,26,53,55,59,58,93,93}; i have done such kinds of problems myself but this is from programming pearls and here code is like this we have some array[a..b] and given value t we write code following way int m=a-1; for i=[a..b] if ( array[i]<t) swap (++m;i); where swap function exchange two element in array at indexes ++m and i, i have run this program and it showed me mistake Exception java.lang.NullPointerException can anybody help me?

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  • Linked List. Insert integers in order

    - by user69514
    I have a linked list of integers. When I insert a new Node I need to insert it not at the end, but in oder... i.e. 2, 4, 5, 8, 11, 12, 33, 55, 58, 102, etc. I don't think I am inserting it in the correct position. Do see what Im doing wrong? Node newNode = new Node(someInt); Node current = head; for(int i=0; i<count; i++){ if(current == tail && tail.data < someInt){ tail.next = newNode; } if(current.data < someInt && current.next.data >= someInt){ newNode.next = current.next; current.next = newNode; } }

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  • Merging and splitting overlapping rectangles to produce non-overlapping ones

    - by uj
    I am looking for an algorithm as follows: Given a set of possibly overlapping rectangles (All of which are "not rotated", can be uniformly represented as (left,top,right,bottom) tuplets, etc...), it returns a minimal set of (non-rotated) non-overlapping rectangles, that occupy the same area. It seems simple enough at first glance, but prooves to be tricky (at least to be done efficiently). Are there some known methods for this/ideas/pointers? Methods for not necessarily minimal, but heuristicly small, sets, are interesting as well, so are methods that produce any valid output set at all.

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  • How to compare two char* variables

    - by davit-datuashvili
    Suppose we have the following method (it is in c code): const char *bitap_search(const char *text, const char *pattern) My question is how can I compare text and pattern if they are char? This method is like a substring problem but I am confused a bit can I write in term of char such code? if (text[i]==pattern[i])? look i am interesting at this algorithm in java http://en.wikipedia.org/wiki/Bitap_algorithm how implement this in java? R = malloc((k+1) * sizeof *R); and please help me to translate this code in java

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  • very simple question but i am confused

    - by davit-datuashvili
    Suppose we have the following method (it is in c code): const char *bitap_search(const char *text, const char *pattern) My question is how can I compare text and pattern if they are char? This method is like a substring problem but I am confused a bit can I write in term of char such code? if (text[i]==pattern[i])?

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  • i have done code so please help

    - by davit-datuashvili
    public class bitap{ public static void main(String[]args){ String text="tbillisi"; String pattern="tbilxiri"; int k=2; int m=pattern.length(); long pattern_mask[]=new long[Character.MAX_VALUE+1]; String result=""; boolean[]R=new boolean[m+1]; long i,d; for (i=0;i<=k;i++){ R[i]=~1; } for (i=0;i if (0==(R[k]& (1< System.out.println(result); } } http://en.wikipedia.org/wiki/Bitap_algorithm from this site

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  • please help me to solve problem

    - by davit-datuashvili
    hi everybody fisrt of all this is not homework and now question is like this suppose i have array int a[]=new int[]{0xBCDA,0xABFE,0xBCAD,0xEFCA,0xFFCA} i know that there is always some hexadecimal number which occurs in all number or in this case A is repeat in array everywhere so my aim is print only repeat number and other numbers should be zero so my new array should be like this 0x000A, 0xA000,0x00A0 0x000A,0x000A any idea please help me? p.s please nobody say that this is homework

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  • serious problems please help me

    - by davit-datuashvili
    guys some of you tell me that i have not accepted your answers on my problems or it is 0 % accepted answers really trust me it is technical problem i did not know what to do in case of get answers please tell me what to do i have accepted all answers they helped me very much what to do? can u explain me what to do and how to do in case i will get correct answers and i accept it?

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  • What algorithms can I use for bullet movement toward the enemy?

    - by theateist
    I develop 2D strategy game(probably for Android). There are weapons that shooting on enemies. From what I've read in this, this, this and this post I think that I need Linear algebra, but I don't really understand what algorithm I should use so the bullet will go to the target? Do I nee pathfinder, why? Can you please suggest what algorithms and/or books I can use for bullet movement toward the enemy?

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  • What is the best book for learning about Algorithms?

    - by sheats
    I know what algorithms are, but I have never consciously used or created one for any of the programming that I have done. So I'd like to get a book about the subject - I'd prefer if it was in python but that's not a strict requirement. What book about algorithms helped you most to understand, use, and create algorithms? One book per answer so they can be voted on...

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