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Search found 491 results on 20 pages for 'rand'.

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  • initializing a vector of custom class in c++

    - by Flamewires
    Hey basically Im trying to store a "solution" and create a vector of these. The problem I'm having is with initialization. Heres my class for reference class Solution { private: // boost::thread m_Thread; int itt_found; int dim; pfn_fitness f; double value; std::vector<double> x; public: Solution(size_t size, int funcNo) : itt_found(0), x(size, 0.0), value(0.0), dim(30), f(Eval_Functions[funcNo]) { for (int i = 1; i < (int) size; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[funcNo]; } } Solution() : itt_found(0), x(31, 0.0), value(0.0), dim(30), f(Eval_Functions[1]) { for (int i = 1; i < 31; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[1]; } } Solution operator= (Solution S) { x = S.GetX(); itt_found = S.GetIttFound(); dim = S.GetDim(); f = S.GetFunc(); value = S.GetValue(); return *this; } void start() { value = f (dim, x); } /* plus additional getter/setter methods*/ } Solution S(30, 1) or Solution(2, 5) work and initalizes everything, but I need X of these solution objects. std::vector<Solution> Parents(X) will create X solutions with the default constructor and i want to construct using the (int, int) constructor. Is there any easy(one liner?) way to do this? Or would i have to do something like: size_t numparents = 10; vector<Solution> Parents; Parents.reserve(numparents); for (int i = 0; i<(int)numparents; i++) { Solution S(31, 0); Parents.push_back(S); }

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  • Check if Ruby object is a Boolean

    - by viatropos
    Can't seem to find how to check if an object is a boolean easily. Is there something like this in Ruby? true.is_a?(Boolean) false.is_a?(Boolean) Right now I'm doing this and would like to shorten it: some_var = rand(1) == 1 ? true : false (some_var.is_a?(TrueClass) || some_var.is_a?(FalseClass))

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  • Initializing a C++ vector to random values... fast

    - by Flamewires
    Hey, id like to make this as fast as possible because it gets called A LOT in a program i'm writing, so is there any faster way to initialize a C++ vector to random values than: double range;//set to the range of a particular function i want to evaluate. std::vector<double> x(30, 0.0); for (int i=0;i<x.size();i++) { x.at(i) = (rand()/(double)RAND_MAX)*range; } EDIT:Fixed x's initializer.

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  • random number in VC++

    - by BillDickson
    int randomNumber = (double)rand() / (RAND_MAX + 1) * (10 - 0) + 0; is the code I'm using, it is getting a random number, but is getting the SAME random combination every time? Can anyone see what I'm doing wrong?

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  • Counting number of searches

    - by shinjuo
    I am trying to figure out how to get the total number of tests each search makes in this algorithm. I am not sure how I can pass that information back from this algorithm though. I need to count how many times while runs and then pass that number back into an array to be added together and determine the average number of test. main.c #include <stdio.h> #include <stdlib.h> #include <time.h> #include <stdbool.h> #include "percentage.h" #include "sequentialSearch.h" #define searchAmount 100 int main(int argc, char *argv[]) { int numbers[100]; int searches[searchAmount]; int i; int where; int searchSuccess; int searchUnsuccess; int percent; srand(time(NULL)); for (i = 0; i < 100; i++){ numbers[i] = rand() % 200; } for (i = 0; i < searchAmount; i++){ searches[i] = rand() % 200; } searchUnsuccess = 0; searchSuccess = 0; for(i = 0; i < searchAmount; i++){ if(seqSearch(numbers, 100, searches[i], &where)){ searchSuccess++; }else{ searchUnsuccess++; } } percent = percentRate(searchSuccess, searchAmount); printf("Total number of searches: %d\n", searchAmount); printf("Total successful searches: %d\n", searchSuccess); printf("Success Rate: %d%%\n", percent); system("PAUSE"); return 0; } sequentialSearch.h bool seqSearch (int list[], int last, int target, int* locn){ int looker; looker = 0; while(looker < last && target != list[looker]){ looker++; } *locn = looker; return(target == list[looker]); }

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  • SQL query, select from 2 tables random

    - by klaus
    Hello all i have a problem that i just CANT get to work like i what it.. i want to show news and reviews (2 tables) and i want to have random output and not the same output here is my query i really hope some one can explain me what i do wrong SELECT anmeldelser.billed_sti , anmeldelser.overskrift , anmeldelser.indhold , anmeldelser.id , anmeldelser.godkendt FROM anmeldelser LIMIT 0,6 UNION ALL SELECT nyheder.id , nyheder.billed_sti , nyheder.overskrift , nyheder.indhold , nyheder.godkendt FROM nyheder ORDER BY rand() LIMIT 0,6

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  • c++ multithread array

    - by user1731972
    i'm doing something for fun, trying to learn multithreading Problems passing array by reference to threads but Arno pointed out that my threading via process.h wasn't going to be multi-threaded. What I'm hoping to do is something where I have an array of 100 (or 10,000, doesn't really matter I don't think), and split up the assignment of values to each thread. Example, 4 threads = 250 values per thread to be assigned. Then I can use this filled array for further calculations. Here's some code I was working on (which doesn't work) #include <process.h> #include <windows.h> #include <iostream> #include <fstream> #include <time.h> //#include <thread> using namespace std; void myThread (void *dummy ); CRITICAL_SECTION cs1,cs2; // global int main() { ofstream myfile; myfile.open ("coinToss.csv"); int rNum; long numRuns; long count = 0; int divisor = 1; float holder = 0; int counter = 0; float percent = 0.0; HANDLE hThread[1000]; int array[10000]; srand ( time(NULL) ); printf ("Runs (use multiple of 10)? "); cin >> numRuns; for (int i = 0; i < numRuns; i++) { //_beginthread( myThread, 0, (void *) (array1) ); //??? //hThread[i * 2] = _beginthread( myThread, 0, (void *) (array1) ); hThread[i*2] = _beginthread( myThread, 0, (void *) (array) ); } //WaitForMultipleObjects(numRuns * 2, hThread, TRUE, INFINITE); WaitForMultipleObjects(numRuns, hThread, TRUE, INFINITE); } void myThread (void *param ) { //thanks goes to stockoverflow //http://stackoverflow.com/questions/12801862/problems-passing-array-by-reference-to-threads int *i = (int *)param; for (int x = 0; x < 1000000; x++) { //param[x] = rand() % 2 + 1; i[x] = rand() % 2 + 1; } } Can anyone explain why it isn't working?

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  • Easiest way to choose a percentage of an amount of rows from a MySQL table?

    - by Rob
    I have a script that has a GET variable: $_GET['percentage'] I have a MySQL table of data. Now lets say that there are 100 rows of data in this table. In pseudo-code: SELECT data FROM table Now would it be possible to select $_GET['percentage'] of random data from table? For example (again in pseudo-code): $_GET['percentage'] = 10; SELECT 10% of data from table order by rand() If this IS possible, how could I do it?

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  • Unique text field in MySQL and php

    - by Jonathan
    I've created a salt using; md5(rand(0,10000000)); (there is probably a better way?) There doesn't seem to be possible to make a text field unique in MYSQL. So how do I check if the salt has already been used for a previous user? Or should I generate the salt based on the current date/time? as it is impossible for 2 users to register at exactly the same time correct?

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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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  • iphone shake error

    - by aaa
    Right now I have this- [code] - (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event { if (event.type == UIEventSubtypeMotionShake) { int text = rand() % 12; switch (text) { case 0: textview.text = @"blah." ; break;[/code] For some reason, the text has to be selected for it to work. If you just shake it, nothing will happen.

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  • Code to generate random numbers in C++

    - by user1678927
    Basically I have to write a program to generate random numbers to simulate the rolling of a pair of dice. This program should be constructed in multiple files. The main function should be in one file, the other functions should be in a second source file, and their prototypes should be in a header file. First I write a short function that returns a random value between 1 and 6 to simulate the rolling of a single 6-sided die.Second, i write a function that pretends to roll a pair of dice by calling this function twice. My program starts by asking the user how many rolls should be made. Then I write a function to simulate rolling the dice this many times, keeping a count of exactly how many times the values 2,3,4,5,6,7,8,9,10,11,12(each number is the sum of a pair of dice) occur in an array. Later I write a function to display a small bar chart using these counts that ideally would look something like below for a sample of 144 rolls, where the number of asterisks printed corresponds to the count: 2 3 4 5 6 7 8 9 10 11 12 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Next, to see how well the random number generator is doing, I write a function to compute the average value rolled. Compare this to the ideal average of 7. Also, print out a small table showing the counts of each roll made by the program, the ideal count based on the frequencies above given the total number of rolls, and the difference between these values in separate columns. This is my incomplete code so far: "Compiler visual studio 2010" int rolling(){ //Function that returns a random value between 1 and 6 rand(unsigned(time(NULL))); int dice = 1 + (rand() %6); return dice; } int roll_dice(int num1,int num2){ //it calls 'rolling function' twice int result1,result2; num1 = rolling(); num2 = rolling(); result1 = num1; result2 = num2; return result1,result2; } int main(void){ int times,i,sum,n1,n2; int c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11;//counters for each sum printf("Please enter how many times you want to roll the dice.\n") scanf_s("%i",&times); I pretend to use counters to count each sum and store the number(the count) in an array. I know i need a loop (for) and some conditional statements (if) but m main problem is to get the values from roll_dice and store them in n1 and n2 so then i can sum them up and store the sum in 'sum'.

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  • Select random line in SQL database

    - by Jensen
    Hi, I would like to select a random line in my database. I saw this solution on a website: SELECT column FROM table ORDER BY RAND() LIMIT 1 This SQL query run but someone said me that it was a non performant query. Is there another solution ? Thx

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  • Estimating the size of a tree

    - by Full Decent
    I'd like to estimate the number of leaves in a large tree structure for which I can't visit every node exhaustively. Is this algorithm appropriate? Does it have a name? Also, please pedant if I am using any terms improperly. sum_trials = 0 num_trials = 0 WHILE time_is_not_up bits = 0 ptr = tree.root WHILE count(ptr.children) > 0 bits += log2(count(ptr.children)) ptr = ptr.children[rand()%count(ptr.children)] sum_trials += bits num_trials++ estimated_tree_size = 2^(sum_trials/num_trials)

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  • generating random enums

    - by null_radix
    How do I randomly select a value for an enum type in C++? I would like to do something like this. enum my_type(A,B,C,D,E,F,G,h,J,V); my_type test(rand() % 10); But this is illegal... there is not an implicit conversion from int to an enum type.

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