Kevin P - 8 months ago 67

C Question

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.

https://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/

Answer

```
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;
}
```

Source (Stackoverflow)