pike.git/ src/ stralloc.c

1999-09-02

1999-09-02 04:40:49 by Fredrik Hübinette (Hubbe) <hubbe@hubbe.net>

• 2cbf7c018b8912ca02bb0799fde843f6cfe2be8e (64 lines) (+61/-3) ^{[ Show | Annotate ]}
  Branch: 7.9

dynamic HASH_PREFIX implementation (major optimization for some applications)

Rev: src/stralloc.c:1.62

23:   #define HUGE HUGE_VAL   #endif /*!HUGE*/    - RCSID("$Id: stralloc.c,v 1.61 1999/08/14 15:09:27 per Exp $"); + RCSID("$Id: stralloc.c,v 1.62 1999/09/02 04:40:49 hubbe Exp $");      #define BEGIN_HASH_SIZE 997   #define MAX_AVG_LINK_LENGTH 3 - #define HASH_PREFIX 64 +     -  + /* Experimental dynamic hash length */ + #ifndef HASH_PREFIX + static unsigned int HASH_PREFIX=32; + static int need_more_hash_prefix=0; + #endif +    unsigned INT32 htable_size=0;   static unsigned int hashprimes_entry=0;   static struct pike_string **base_table=0;
282:    int h)   {    struct pike_string *curr,**prev, **base; + #ifndef HASH_PREFIX +  unsigned int depth=0; + #endif       for(base = prev = base_table + h;( curr=*prev ); prev=&curr->next)    {
304:    *base = curr;    return curr; /* pointer to string */    } + #ifndef HASH_PREFIX +  depth++; + #endif    } -  + #ifndef HASH_PREFIX +  /* These heuruistics might require tuning! /Hubbe */ +  if(depth > HASH_PREFIX && HASH_PREFIX<len) +  { +  need_more_hash_prefix++; + /* fprintf(stderr,"depth=%d num_strings=%d need_more_hash_prefix=%d HASH_PREFIX=%d\n",depth,num_strings,need_more_hash_prefix,HASH_PREFIX); */ +  }else{ +  if(need_more_hash_prefix) +  need_more_hash_prefix--; +  } + #endif    return 0; /* not found */   }   
372:    base_table=(struct pike_string **)xalloc(sizeof(struct pike_string *)*htable_size);    MEMSET((char *)base_table,0,sizeof(struct pike_string *)*htable_size);    -  for(h=0;h<old;h++) rehash_string_backwards(old_base[h]); +  for(h=0;h<old;h++) +  rehash_string_backwards(old_base[h]);       if(old_base)    free((char *)old_base);
408:    num_strings++;    if(num_strings > MAX_AVG_LINK_LENGTH * htable_size)    rehash(); +  + #ifndef HASH_PREFIX +  /* These heuruistics might require tuning! /Hubbe */ +  if(need_more_hash_prefix > ( htable_size >> 4)) +  { +  /* This could in theory have a pretty ugly complexity */ +  /* /Hubbe +  */ +  unsigned INT32 save_full_hash_value=full_hash_value; +  +  need_more_hash_prefix=0; +  HASH_PREFIX=HASH_PREFIX*2; + /* fprintf(stderr,"Doubling HASH_PREFIX to %d and rehashing\n",HASH_PREFIX); */ +  +  for(h=0;h<htable_size;h++) +  { +  struct pike_string *tmp=base_table[h]; +  base_table[h]=0; +  while(tmp) +  { +  int h2; +  struct pike_string *tmp2=tmp; /* First unlink */ +  tmp=tmp2->next; +  +  h2=do_hash(tmp2); /* compute new hash value */ +  tmp2->hval=full_hash_value; +  +  tmp2->next=base_table[h2]; /* and re-hash */ +  base_table[h2]=tmp2;    } -  +  } +  full_hash_value=save_full_hash_value; +  } + #endif + }      struct pike_string *debug_begin_wide_shared_string(int len, int shift)   {