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New option --multiple-iterations.

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This commit is contained in:
Bruno Haible
2003-01-15 13:01:25 +00:00
parent c67f999b54
commit c3467c5302
11 changed files with 207 additions and 10 deletions
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42
src/keyword-list.cc
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@@ -25,18 +25,60 @@
#include <stddef.h>
/* -------------------------- Keyword_List class --------------------------- */
/* Constructor. */
Keyword_List::Keyword_List (Keyword *car)
: _cdr (NULL), _car (car)
{
}
/* ------------------------- KeywordExt_List class ------------------------- */
/* Unused constructor. */
KeywordExt_List::KeywordExt_List (KeywordExt *car)
: Keyword_List (car)
{
}
/* ------------------------ Keyword_List functions ------------------------- */
/* Copies a linear list, sharing the list elements. */
Keyword_List *
copy_list (Keyword_List *list)
{
Keyword_List *result;
Keyword_List **lastp = &result;
while (list != NULL)
{
Keyword_List *new_cons = new Keyword_List (list->first());
*lastp = new_cons;
lastp = &new_cons->rest();
list = list->rest();
}
*lastp = NULL;
return result;
}
/* Copies a linear list, sharing the list elements. */
KeywordExt_List *
copy_list (KeywordExt_List *list)
{
return static_cast<KeywordExt_List *> (copy_list (static_cast<Keyword_List *> (list)));
}
/* Deletes a linear list, keeping the list elements in memory. */
void
delete_list (Keyword_List *list)
{
while (list != NULL)
{
Keyword_List *rest = list->rest();
delete list;
list = rest;
}
}
#ifndef __OPTIMIZE__

7
src/keyword-list.h
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@@ -57,6 +57,13 @@ public:
KeywordExt_List *& rest ();
};
/* Copies a linear list, sharing the list elements. */
extern Keyword_List * copy_list (Keyword_List *list);
extern KeywordExt_List * copy_list (KeywordExt_List *list);
/* Deletes a linear list, keeping the list elements in memory. */
extern void delete_list (Keyword_List *list);
#ifdef __OPTIMIZE__
#define INLINE inline

26
src/options.cc
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@@ -65,7 +65,7 @@ static const char *const DEFAULT_DELIMITERS = ",\n";
void
Options::short_usage (FILE * stream) const
{
fprintf (stream, "Usage: %s [-cCdDef[num]F<initializers>GhH<hashname>i<init>Ijk<keys>K<keyname>lL<language>nN<function name>ors<size>S<switches>tTvW<wordlistname>Z<class name>7] [input-file]\n"
fprintf (stream, "Usage: %s [-cCdDef[num]F<initializers>GhH<hashname>i<init>Ij<jump>k<keys>K<keyname>lL<language>m<num>nN<function name>ors<size>S<switches>tTvW<wordlistname>Z<class name>7] [input-file]\n"
"Try '%s --help' for more information.\n",
program_name, program_name);
}
@@ -192,6 +192,12 @@ Options::long_usage (FILE * stream) const
" argument represents the number of times to iterate\n"
" when resolving a collision. '0' means \"iterate by\n"
" the number of keywords\".\n");
fprintf (stream,
" -m, --multiple-iterations=ITERATIONS\n"
" Perform multiple choices of the -i and -j values,\n"
" and choose the best results. This increases the\n"
" running time by a factor of ITERATIONS but does a\n"
" good job minimizing the generated table size.\n");
fprintf (stream,
" -i, --initial-asso=N Provide an initial value for the associate values\n"
" array. Default is 0. Setting this value larger helps\n"
@@ -413,6 +419,7 @@ Options::Options ()
_iterations (0),
_jump (DEFAULT_JUMP_VALUE),
_initial_asso_value (0),
_asso_iterations (0),
_total_switches (1),
_size_multiple (1),
_function_name (DEFAULT_NAME),
@@ -459,6 +466,7 @@ Options::~Options ()
"\nword list name = %s"
"\nkey name = %s"
"\ninitializer suffix = %s"
"\nasso_values iterations = %d"
"\njump value = %d"
"\nhash table size multiplier = %d"
"\ninitial associated value = %d"
@@ -486,8 +494,8 @@ Options::~Options ()
_option_word & SEVENBIT ? "enabled" : "disabled",
_iterations,
_function_name, _hash_name, _wordlist_name, _key_name,
_initializer_suffix, _jump, _size_multiple, _initial_asso_value,
_delimiters, _total_switches);
_initializer_suffix, _asso_iterations, _jump, _size_multiple,
_initial_asso_value, _delimiters, _total_switches);
if (_option_word & ALLCHARS)
fprintf (stderr, "all characters are used in the hash function\n");
else
@@ -535,6 +543,7 @@ static const struct option long_options[] =
{ "fast", required_argument, NULL, 'f' },
{ "initial-asso", required_argument, NULL, 'i' },
{ "jump", required_argument, NULL, 'j' },
{ "multiple-iterations", required_argument, NULL, 'm' },
{ "no-strlen", no_argument, NULL, 'n' },
{ "occurrence-sort", no_argument, NULL, 'o' },
{ "random", no_argument, NULL, 'r' },
@@ -556,7 +565,7 @@ Options::parse_options (int argc, char *argv[])
while ((option_char =
getopt_long (_argument_count, _argument_vector,
"adcCDe:Ef:F:gGhH:i:Ij:k:K:lL:nN:oprs:S:tTvW:Z:7",
"acCdDe:Ef:F:gGhH:i:Ij:k:K:lL:m:nN:oprs:S:tTvW:Z:7",
long_options, NULL))
!= -1)
{
@@ -738,6 +747,15 @@ Options::parse_options (int argc, char *argv[])
}
break;
}
case 'm': /* Multiple iterations for finding good asso_values. */
{
if ((_asso_iterations = atoi (/*getopt*/optarg)) < 0)
{
fprintf (stderr, "asso_iterations value must not be negative, assuming 0\n");
_asso_iterations = 0;
}
break;
}
case 'n': /* Don't include the length when computing hash function. */
{
_option_word |= NOLENGTH;

6
src/options.h
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@@ -190,6 +190,9 @@ public:
/* Returns the initial associated character value. */
int get_initial_asso_value () const;
/* Returns the number of iterations for finding good asso_values. */
int get_asso_iterations () const;
/* Returns the total number of switch statements to generate. */
int get_total_switches () const;
@@ -250,6 +253,9 @@ private:
/* Initial value for asso_values table. */
int _initial_asso_value;
/* Number of attempts at finding good asso_values. */
int _asso_iterations;
/* Number of switch statements to generate. */
int _total_switches;

7
src/options.icc
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@@ -146,6 +146,13 @@ Options::get_initial_asso_value () const
return _initial_asso_value;
}
/* Returns the number of iterations for finding finding good asso_values. */
INLINE int
Options::get_asso_iterations () const
{
return _asso_iterations;
}
/* Returns the total number of switch statements to generate. */
INLINE int
Options::get_total_switches () const

83
src/search.cc
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@@ -434,6 +434,9 @@ Search::prepare_asso_values ()
if (option[RANDOM] || option.get_jump () == 0)
/* We will use rand(), so initialize the random number generator. */
srand (reinterpret_cast<long>(time (0)));
_initial_asso_value = (option[RANDOM] ? -1 : option.get_initial_asso_value ());
_jump = option.get_jump ();
}
/* Puts a first guess into asso_values[]. */
@@ -441,14 +444,14 @@ Search::prepare_asso_values ()
void
Search::init_asso_values ()
{
if (option[RANDOM])
if (_initial_asso_value < 0)
{
for (int i = 0; i < _alpha_size; i++)
_asso_values[i] = rand () & (_asso_value_max - 1);
}
else
{
int asso_value = option.get_initial_asso_value ();
int asso_value = _initial_asso_value;
asso_value = asso_value & (_asso_value_max - 1);
for (int i = 0; i < _alpha_size; i++)
@@ -565,7 +568,7 @@ Search::try_asso_value (unsigned char c, KeywordExt *curr, int iterations)
/* Try next value. Wrap around mod _asso_value_max. */
_asso_values[c] =
(_asso_values[c] + (option.get_jump () ? option.get_jump () : rand ()))
(_asso_values[c] + (_jump != 0 ? _jump : rand ()))
& (_asso_value_max - 1);
/* Iteration Number array is a win, O(1) intialization time! */
@@ -733,7 +736,77 @@ Search::optimize ()
prepare_asso_values ();
/* Search for good _asso_values[]. */
find_asso_values ();
int asso_iteration;
if ((asso_iteration = option.get_asso_iterations ()) == 0)
/* Try only the given _initial_asso_value and _jump. */
find_asso_values ();
else
{
/* Try different pairs of _initial_asso_value and _jump, in the
following order:
(0, 1)
(1, 1)
(2, 1) (0, 3)
(3, 1) (1, 3)
(4, 1) (2, 3) (0, 5)
(5, 1) (3, 3) (1, 5)
..... */
KeywordExt_List *saved_head = _head;
int best_initial_asso_value = 0;
int best_jump = 1;
int *best_asso_values = new int[_alpha_size];
int best_collisions = INT_MAX;
int best_max_hash_value = INT_MAX;
_initial_asso_value = 0; _jump = 1;
for (;;)
{
/* Restore the keyword list in its original order. */
_head = copy_list (saved_head);
/* Find good _asso_values[]. */
find_asso_values ();
/* Test whether it is the best solution so far. */
int collisions = 0;
int max_hash_value = INT_MIN;
_collision_detector->clear ();
for (KeywordExt_List *ptr = _head; ptr; ptr = ptr->rest())
{
KeywordExt *keyword = ptr->first();
int hashcode = compute_hash (keyword);
if (max_hash_value < hashcode)
max_hash_value = hashcode;
if (_collision_detector->set_bit (hashcode))
collisions++;
}
if (collisions < best_collisions
|| (collisions == best_collisions
&& max_hash_value < best_max_hash_value))
{
memcpy (best_asso_values, _asso_values,
_alpha_size * sizeof (_asso_values[0]));
best_collisions = collisions;
best_max_hash_value = max_hash_value;
}
/* Delete the copied keyword list. */
delete_list (_head);
if (--asso_iteration == 0)
break;
/* Prepare for next iteration. */
if (_initial_asso_value >= 2)
_initial_asso_value -= 2, _jump += 2;
else
_initial_asso_value += _jump, _jump = 1;
}
_head = saved_head;
/* Install the best found asso_values. */
_initial_asso_value = best_initial_asso_value;
_jump = best_jump;
memcpy (_asso_values, best_asso_values,
_alpha_size * sizeof (_asso_values[0]));
delete[] best_asso_values;
/* The keywords' _hash_value fields are recomputed below. */
}
/* Make one final check, just to make sure nothing weird happened.... */
_collision_detector->clear ();
@@ -749,7 +822,7 @@ Search::optimize ()
{
fprintf (stderr,
"\nInternal error, duplicate value %d:\n"
"try options -D or -r, or use new key positions.\n\n",
"try options -D or -m or -r, or use new key positions.\n\n",
hashcode);
exit (1);
}

5
src/search.h
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@@ -132,6 +132,11 @@ private:
/* Exclusive upper bound for every _asso_values[c]. A power of 2. */
int _asso_value_max;
/* Initial value for asso_values table. -1 means random. */
int _initial_asso_value;
/* Jump length when trying alternative values. 0 means random. */
int _jump;
/* Maximal possible hash value. */
int _max_hash_value;