Microsoft Windows default random number generator
This document present the way the random() and srandom() function work under MS Windows 2000/XP (maybe on others too).
- srandom() : Simply initialise a static unsigned int by the value given in parameter. Lets call this variable holdrand.
- random() : Modify holdran as though : holdrand = holdrand * 214013L + 2531011L. Returns a "random value" computed with the new holdrand value : return (holdrand >> 16) & 0x7fff;
The following code sample implements it :
class W32Rand {
private:
unsigned int holdrand;
public:
void srand(unsigned int seed) {
holdrand = seed;
}
public:
unsigned int rand(void) {
return ((holdrand = holdrand * 214013L + 2531011L) >> 16) & 0x7fff;
}
};
Posted in: Articles , samedi 4 février 2006
