Kevin P Kevin P - 1 year ago 90
C Question

Faster than rand()?

I'm working on an algorithm which needs to generate millions of numbers as fast as possible. Actually I found out that the rand() function of my algorithm takes 75% of the process time.

So I'm looking for something faster. And I don't need a big range at all. (I only need integer numbers below 1000)

Do you know something I could use ?

Thanks !

Edit :

I use this numbers for shuffling groups of less than 1000 entities.

I found out more about the "fast rand". And there is SSE version version which is even faster and generates 4 numbers at a time.

Answer Source
static unsigned int g_seed;

// Used to seed the generator.           
inline void fast_srand(int seed) {
    g_seed = seed;

// Compute a pseudorandom integer.
// Output value in range [0, 32767]
inline int fast_rand(void) {
    g_seed = (214013*g_seed+2531011);
    return (g_seed>>16)&0x7FFF;
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