how to keep a randomized value from an array randomized?

[Boneman]

hi! Let's jump straight to the code:

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <ctime>
#include <string>
#include <sstream>

using namespace std;


int main(){
srand(time(NULL));

int abilitydamage[2]{0,rand()% 1100 +1};
int damage;


for (int tttt = 0; tttt < 3; tttt++){
    cout << "this is the loop timer: " << tttt << endl;
    damage = abilitydamage[1];
    cout << "This is a randomizer test: " << damage << endl;
}
}

I'm pulling a randomized number from inside the ability array and give damage the same value. But I want this value to keep randomizing, and instead it remains static. I also noticed while running it several times, that even the initial random value would consistently show the same value in a row, and slowly increase it over time as I kept reopening the program. How do I keep the value randomized, and stop this weird behavior too?

[TarikNeaj]

1. Pick a better variable name to loop with.
2. Arrays start at 1. Meaning, your array of size to can be accessed - abilitydamage[0-1]. So you want the loop to run on 0 and 1.

3.

I also noticed while running it several times, that even the initial random value would consistently show the same value in a row, and slowly increase it over time as I kept reopening the program.

Read here:

http://stackoverflow.com/questions/6668282/srandtimenull-generating-similar-results

srand is pretty shittie and you should not use it, there is a much better way of doings things now, using the random header <random> introduced in c++11 -

http://www.cplusplus.com/reference/random/

Watch this great video -

https://channel9.msdn.com/Events/GoingNative/2013/rand-Considered-Harmful

Here is what it should look like though in your code -

for(int i = 0; i < 2; i++) // loops twice
{
     cout << "this is the loop timer: " << i << endl;
     damage = abilitydamage[i];
     cout << "This is a randomizer test: " << damage << endl;
}

[Boneman]

ok, looked up the video on <random>, and tried to run the example code, but I only get this error:

terminate called after throwing an instance of 'std::runtime_error'
what(): random_device::random_device(const std::string&)

I get the same error using any example with random_device. Why is that? How do I fix that?

And the original question still stands, how do I keep the value in an array randomizing each time it is called?

[TarikNeaj]

And the original question still stands, how do I keep the value in an array randomizing each time it is called?

Could you be more specific, I don't understand the question. Each time what is called? you're not calling anything in your code. Keep what the value? It is being kept in the code I gave you.

[tom221b]

Here is an example (generating 10 numbers with both methods)

#include <iostream>
#include <random>
#include <ctime>

int main()
{
    //the old method
    srand(time(nullptr));
    for(int i = 0; i < 10; ++i)
    {
        int r = rand() % 10 + 1; //returns random numbers
        std::cout << r << " ";
    }
    std::cout << "\n\n";

    //the new method
    std::default_random_engine e;
    //e.seed(999); //you can manually seed
    std::uniform_int_distribution<int> d(1, 9); //range

    for(int i = 0; i < 10; ++i)
    {
        int r = d(e);
        std::cout << r << " ";
    }
    std::cout << "\n";

    return 0;
}

[Boneman]

with seed numbers the program doesn't crash, but because of that the numbers are now even generated the same. I really need someone to tell me how to get random_device working, and then I will test if it will continually randomize my value in the array.

I'll say again what I want:

int abilitydamage[2]{0,rand()% 1100 +1}; //the goal is to get this value to randomize each time it is being called.
int damage;


for (int tttt = 0; tttt < 3; tttt++){
    cout << "this is the loop timer: " << tttt << endl;
    damage = abilitydamage[1]; //so that everytime the loop prints it out, instead of giving e.g: "203,203,203" or "380,380,380", it should give something like "730,482,1039".
    cout << "This is a randomizer test: " << damage << endl;
}

[TarikNeaj]

The reason the numbers are being repeated is because here - rand()% 1100 +1 is returning a number, and then you simply give that number to damage 3 times. You'll need to refresh it -

int abilitydamage[2]{0, rand() % 1100 + 1};
int damage;

	
for (int tttt = 0; tttt < 3; tttt++){
	cout << "this is the loop timer: " << tttt << endl;
	damage = abilitydamage[1];
	cout << "This is a randomizer test: " << damage << endl;
	abilitydamage[1] = rand() % 1100 + 1; // get a new random number
}

[Boneman]

yup, that works! Ty so far!

I want to know one other thing, I have dozens of these randomized numbers in my array, is there a smooth way to let them re-roll all at once, or can I only change them one by one, like in the example?

I have been trying to use abilitydamage[10] = {//all the random numbers..} for that, but the compiler won't accept it. Is this idea even possible?

//edit: removed the {} entirely, and the compiler let's it at least run, but I don't see any changes. Ughhhhhhh!!

[Boneman]

Hello again! I have been working to sorting this issue out on my own, and I got it solved.

First, I learned more about <random> and found out a way to use it without random_device and instead with the system clock. I have to store every value I generate to a designated name/location, but that came in useful later on:

unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();

std::minstd_rand0 generator (seed);

std::uniform_int_distribution<int> D_RANDOM_VALUE(1,1100); //The distribute value

int RANDOM_VALUE = D_RANDOM_VALUE(generator); //The actual value 

The arrays refuse to generate random numbers and proved to be the biggest roadblock. So instead of hacking together a big code to work around it, I figured, since I already have all the values stored to specific names, I don't need to bother forcing them into an array, but instead just let the array point to their location. This was a major step to a complete solution:

int *RandomArray[1]{&RANDOM_VALUE};


However, there was one more thing missing. The values were randomly generated the first run, but then again, stayed the same. After a bit of tinkering, I realized that I had to re-generate the base values after every time they were called. In my game I used a specific loop to re-generate every ability again, which is highly pragmatic and performance-heavy, but until it becomes a real issue / I figure out how to do it more practical, it will suffice.

for (int tttt = 0; tttt < 3; tttt++){

    RANDOM_VALUE = D_RANDOM_VALUE(generator);
    damage = *RandomArray[0];
    cout << "This is the damage: " << damage << "\n" << endl;
    cout << "This is the random value: " << RANDOM_VALUE << "\n" << endl;
}

And this is how I solved it. The game works perfectly fine, and the random-generator has not failed thus far. Here is the complete testcode that sums the post up:

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <ctime>
#include <time.h>
#include <string>
#include <sstream>
#include <random>
#include <chrono>

unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();

std::minstd_rand0 generator (seed);

std::uniform_int_distribution<int> D_RANDOM_VALUE(1,1100); //The distribute value

int RANDOM_VALUE = D_RANDOM_VALUE(generator); //The actual value

int health = 2000;
int damage;
int *RandomArray[1]{&RANDOM_VALUE};

using namespace std;

int main(){




AGAIN: //DEBUG

for (int tttt = 0; tttt < 3; tttt++){

    RANDOM_VALUE = D_RANDOM_VALUE(generator);

    cout << "this is the loop timer: " << tttt << "\n" << endl;
    damage = *RandomArray[0];
    health = health - damage;
    cout << "This is the damage: " << damage << "\n" << endl;
    cout << "This is the random value: " << RANDOM_VALUE << "\n" << endl;
    cout << "This is the health: " << health << "\n" << endl;
    damage = 0;
    health = 2000;
system("pause");
system("cls");
}


goto AGAIN; //DEBUG

}

With this, I will mark this thread as solved. Hope this will answer the question for everyone who may look it up in the future. Hello from 2016 by the way!! Wuuuu!