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Full Discussion: Hash Function Speed
Top Forums Programming Hash Function Speed Post 302364252 by jim mcnamara on Thursday 22nd of October 2009 11:54:47 AM
Old 10-22-2009
As to hash improvement in general - test avalanche/distribution for your data sets on these:

Code:
// XOR-Bernstein hash

unsigned xor_b_hash ( const void *key, 
                      const int len,
                      const unsigned tablesize )
{
  const unsigned char *p = (const unsigned char *)key;
  unsigned hval = 0;
  int i=0;

  for ( i = 0; i < len; i++, p++ )
    hval = 33 * hval ^ *p;

  return hval % tablesize;
}

// fowler/nol/vo hash

unsigned fnv_hash ( const void *key, 
                    const int len,
                    const unsigned tablesize )
{
  const unsigned char *p = (const unsigned char *)key;
  unsigned hval = 2166136261U;
  int i=0;

  for ( i = 0; i < len; i++, p++ )
    hval = ( hval * 16777619 ) ^ *p;

  return hval % tablesize;
}

OP's additive hash fails to treat permutations, i.e., “xyz”, “zyx”, and “xzy” all result in the same hash value.

And if the original hash is "slow", then so will these be. Did you try instrumtenting your code, or using a profiler? ...before you decided the hash algorithm was the bottleneck.
 

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HMAC(3) 							      OpenSSL								   HMAC(3)

NAME
HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message authentication code SYNOPSIS
#include <openssl/hmac.h> unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len, const unsigned char *d, int n, unsigned char *md, unsigned int *md_len); void HMAC_CTX_init(HMAC_CTX *ctx); void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len, const EVP_MD *md); void HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len, const EVP_MD *md, ENGINE *impl); void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len); void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len); void HMAC_CTX_cleanup(HMAC_CTX *ctx); void HMAC_cleanup(HMAC_CTX *ctx); DESCRIPTION
HMAC is a MAC (message authentication code), i.e. a keyed hash function used for message authentication, which is based on a hash function. HMAC() computes the message authentication code of the n bytes at d using the hash function evp_md and the key key which is key_len bytes long. It places the result in md (which must have space for the output of the hash function, which is no more than EVP_MAX_MD_SIZE bytes). If md is NULL, the digest is placed in a static array. The size of the output is placed in md_len, unless it is NULL. evp_md can be EVP_sha1(), EVP_ripemd160() etc. key and evp_md may be NULL if a key and hash function have been set in a previous call to HMAC_Init() for that HMAC_CTX. HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_cleanup() erases the key and other data from the HMAC_CTX and releases any associated resources. It must be called when an HMAC_CTX is no longer required. HMAC_cleanup() is an alias for HMAC_CTX_cleanup() included for back compatibility with 0.9.6b, it is deprecated. The following functions may be used if the message is not completely stored in memory: HMAC_Init() initializes a HMAC_CTX structure to use the hash function evp_md and the key key which is key_len bytes long. It is deprecated and only included for backward compatibility with OpenSSL 0.9.6b. HMAC_Init_ex() initializes or reuses a HMAC_CTX structure to use the function evp_md and key key. Either can be NULL, in which case the existing one will be reused. HMAC_CTX_init() must have been called before the first use of an HMAC_CTX in this function. N.B. HMAC_Init() had this undocumented behaviour in previous versions of OpenSSL - failure to switch to HMAC_Init_ex() in programs that expect it will cause them to stop working. HMAC_Update() can be called repeatedly with chunks of the message to be authenticated (len bytes at data). HMAC_Final() places the message authentication code in md, which must have space for the hash function output. RETURN VALUES
HMAC() returns a pointer to the message authentication code. HMAC_CTX_init(), HMAC_Init_ex(), HMAC_Update(), HMAC_Final() and HMAC_CTX_cleanup() do not return values. CONFORMING TO
RFC 2104 SEE ALSO
sha(3), evp(3) HISTORY
HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() are available since SSLeay 0.9.0. HMAC_CTX_init(), HMAC_Init_ex() and HMAC_CTX_cleanup() are available since OpenSSL 0.9.7. 0.9.8 2009-04-03 HMAC(3)
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