Hello every one,
i've a string hash function it's performace is already good but there is some things that happens inside it and idon't know why
the hash function:
unsigned int table::hash(const string &word)
{
int hash = 0;
int n=word.length();
for(int i=0;i<n;i++)
hash = 31*hash+word;
return hash % MAX_TABLE;
}
my questions about it
why we multiply by 31 the hash every time is this for making weighting for the characters or any thing else?
thanks inadvance.

 

Stack of information can be obtained from here Hashing algorythms and examples , explanations

http://www.partow.net/programming/hashfunctions/#VariousFormsOfHashing

Should help you on this extensive subject

 

Notice that 31 is a Mersenne prime

http://en.wikipedia.org/wiki/Mersenne_prime

and the algorithm is related to the Linear Congruential Random Number Generator. Good random number generators seem to have desirable features for a hashing algorithm.

http://en.wikipedia.org/wiki/Linear_congruential_generator