c++ - What's the best hashing algorithm to use on a stl string when using hash_map?

Question

I've found the standard hashing function on VS2005 is painfully slow when trying to achieve high performance look ups. What are some good examples of fast and efficient hashing algorithms that should void most collisions?

Answer 1

I worked with Paul Larson of Microsoft Research on some hashtable implementations. He investigated a number of string hashing functions on a variety of datasets and found that a simple multiply by 101 and add loop worked surprisingly well.

unsigned int
hash(
    const char* s,
    unsigned int seed = 0)
{
    unsigned int hash = seed;
    while (*s)
    {
        hash = hash * 101  +  *s++;
    }
    return hash;
}