Adwaith-Rajesh/gperf
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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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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);
}