srand

问题 This question already has answers here : How does calling srand more than once affect the quality of randomness? (5 answers) Closed 2 years ago . I am pretty new to C++ and am trying to make a simple die roll with a Die class/main. I can get a random number within my range 1-dieSize, however, each time I "roll the dice" it just gives me the same random number. For example, when I roll this dice three times, it will cout 111 or 222 etc instead of 3 different random rolls. Any help explaining

问题 I'm generating 2D terrain with 1D perlin noise using Mersenne Twister to for random numbers. My first thought was using Mersenne Twister will give me always the same results with same seed on any given hardware. But when I compare the values/terrain on different devices it gives me different results. (It worked for IOS, OSX and MAC, but not for WP8). Code: class 1DNoiseTest { typedef std::mt19937 MyRNG; MyRNG rng; 1DNoiseTest( unsigned seed ) { rng.seed(seed); std::uniform_real_distribution

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Generate Random numbers uniformly over entire range C++ random float How can I generate a random number between 5 and 25 in c++ ? #include <iostream> #include <cstdlib> #include <time.h> using namespace std; void main() { int number; int randomNum; srand(time(NULL)); randomNum = rand(); } 回答1: Do rand() % 20 and increment it by 5. 回答2: In C++11: #include <random> std::default_random_engine re; re.seed(time(NULL)

问题 Here is the code, but the outputs aren't coming out random? Maybe cause when the program runs it has the same time as all the loops? #include <iostream> using namespace std; #include <string> #include <cmath> #include <ctime> #include <cstdlib> int main() { long int x = 0; bool repeat = true; srand( time(0)); int r1 = 2 + rand() % (11 - 2); //has a range of 2-10 int r3 = rand(); for (int i = 0; i <5; i++) { cout << r1 << endl; //loops 5 times but the numbers are all the same cout << r3 <<

问题 I know this kind of question has been asked a few times, but alot of them answers boil down to RTFM, but I'm hoping if I can ask the right question... I can get a quasi-definitive answer for everyone else as well, regarding implementation. I'm trying to generate a sequence of random numbers in one of the two following ways: #include <cstdlib> #include <ctime> #include <cmath> #include "Cluster.h" #include "LatLng.h" srand((unsigned)time(0)); double heightRand; double widthRand; for (int p = 0

问题 Trying to solve an exercise where I have to print a random temperature value between 35°C & -10°C every 5 seconds followed by the date and time. Everything looks to be working as intended, however when I enter the code in a test script I get following errors. This is my code: #include<stdio.h> #include<unistd.h> #include<time.h> #define temp_max 35 #define temp_min -10 #define FREQUENCY 5 int main(void) { srand(time(NULL)); while(1) { int number = rand() % (temp_max*100 - temp_min*100) + temp

问题 Since I found this particular documentation on https://www.tutorialspoint.com/c_standard_library/c_function_rand.htm ,I have been thinking about this particular line of code srand((unsigned)time(&t)); .Whenever I had to generate some stuff,I used srand(time(NULL)) in order not to generate the same stuff everytime I run the program,but when I came across this,I have been wondering :Is there any difference between srand((unsigned)time(&t)) and srand(time(NULL)) ?Because to me they seem like

问题 I am forking multiple processes from a manager process. I then would like to make a random port number for these forked processes to listen on. However, when I seed random, and get a random number, I get the same number between the three processes. For example: manager: int main(){ for(int i = 0; i < rCount; i++){ pid_t pid = fork(); if (pid == 0) {// child execl(ROUTERLOCATION,"",NULL); //create router process } else { // parent } } } router: int main(){ randomPort(); } void randomPort(){

问题 I am currently running a multithreading simulation application with 8+ pipes (threads). These pipes run a very complex code that depends on a random sequence generated by a seed. The sequence is then boiled down to a single 0/1. I want this "random processing" to be 100% deterministic after passing a seed to the processing pipe from the main thread. So, I can replicate the results in a second run. So, for example: (I have this coded and it works) Pipe 1 -> Seed: 123 -> Result: 0 Pipe 2 ->

问题 I've got an unmanaged c++ console application in which I'm using srand() and rand(). I don't need this to solve a particular problem, but was curious: is the original seed passed to srand() stored somewhere in memory that I can query? Is there any way to figure out what the seed was? 回答1: The seed is not required to be stored, only the last random number returned is. Here's the example from the manpage: static unsigned long next = 1; /* RAND_MAX assumed to be 32767 */ int myrand(void) { next