rand changes value without changing seed
c++, random, random-seed
Solution
Each call to `rand()` will always generate a different random number.
The seed actually determines the sequence of random numbers that's created. Using a different seed will get you another 3 random numbers, but you will always get those 3 numbers for a given seed.
If you want to have the same number multiple times just call `rand()` once and save it in a variable.
Problem
Take the following program: ``` #include <cstdlib> using std::rand; #include <iostream> using std::cout; int main() { cout << rand() << ' ' << rand() << ' ' << rand() << '\n'; } ``` Due to `rand` producing the same values as long as the seed isn't changed using `srand`, this should produce three identical numbers. e.g. ``` 567 567 567 ``` However, when I run this program it gives me three different values. e.g. ``` 6334 18467 41 ``` When the program is (compiled and) run again, the same three numbers are generated. Shouldn't I have to use `srand` to change the seed before I start getting different results from `rand`? Is this just my compiler/implementation trying to do me a favour? OS: Windows XP Compiler: GCC 4.6.2 Libraries: MinGW EDIT: By trying to use `srand`, I discovered that this is the result from a seed of 1 (which I guess is made default).