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tables: use bitsets for a performance boost

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Suggested by Yuri at
<http://lists.gnu.org/archive/html/bison-patches/2012-01/msg00000.html>.

The improvement is marginal for most grammars, but notable for large
grammars (e.g., PosgreSQL's postgre.y), and very large for the
sample.y grammar submitted by Yuri in
http://lists.gnu.org/archive/html/bison-patches/2012-01/msg00012.html.
Measured with --trace=time -fsyntax-only.

parser action tables    postgre.y     sample.y
Before                 0,129 (44%)  37,095 (99%)
After                  0,117 (42%)   5,046 (93%)

* src/tables.c (pos): Replace this set of integer coded as an unsorted
array or integers with...
(pos_set): this bitset.
This commit is contained in:
Theophile Ranquet
2012-11-13 10:38:49 +00:00
committed by Akim Demaille
parent b5cd777ad6
commit af1c6f973a
1 changed files with 25 additions and 16 deletions
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41
src/tables.c
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@@ -21,6 +21,7 @@
#include <config.h>
#include "system.h"
#include <bitset.h>
#include <bitsetv.h>
#include "complain.h"
@@ -110,7 +111,9 @@ base_number *base = NULL;
computation equals to BASE_MINIMUM, later mapped to BASE_NINF to
keep parser tables small. */
base_number base_ninf = 0;
static base_number *pos = NULL;
/* Bitset representing an integer set in the range
-nstates..table_size (as an upper bound) */
static bitset pos_set = NULL;
static unsigned *conflrow;
unsigned *conflict_table;
@@ -150,20 +153,23 @@ table_grow (int desired)
table_size *= 2;
if (trace_flag & trace_resource)
fprintf (stderr, "growing table and check from: %d to %d\n",
fprintf (stderr, "growing tables from %d to %d\n",
old_size, table_size);
table = xnrealloc (table, table_size, sizeof *table);
memset (table + old_size, 0,
sizeof *table * (table_size - old_size));
conflict_table = xnrealloc (conflict_table, table_size,
sizeof *conflict_table);
check = xnrealloc (check, table_size, sizeof *check);
memset (conflict_table + old_size, 0,
sizeof *conflict_table * (table_size - old_size));
for (/* Nothing. */; old_size < table_size; ++old_size)
{
table[old_size] = 0;
conflict_table[old_size] = 0;
check[old_size] = -1;
}
check = xnrealloc (check, table_size, sizeof *check);
for (int i = old_size; i < table_size; ++i)
check[i] = -1;
bitset_resize (pos_set, table_size + nstates);
}
@@ -659,10 +665,8 @@ pack_vector (vector_number vector)
ok = false;
}
if (ok)
for (int k = 0; k < vector; k++)
if (pos[k] == res)
ok = false;
if (ok && bitset_test (pos_set, nstates + res))
ok = false;
}
if (ok)
@@ -720,7 +724,7 @@ static void
pack_table (void)
{
base = xnmalloc (nvectors, sizeof *base);
pos = xnmalloc (nentries, sizeof *pos);
pos_set = bitset_create (table_size + nstates, BITSET_FRUGAL);
table = xcalloc (table_size, sizeof *table);
conflict_table = xcalloc (table_size, sizeof *conflict_table);
check = xnmalloc (table_size, sizeof *check);
@@ -746,7 +750,12 @@ pack_table (void)
/* Action of I were already coded for S. */
place = base[s];
pos[i] = place;
/* Store PLACE into POS_SET. PLACE might not belong to the set
of possible values for instance with useless tokens. It
would be more satisfying to eliminate the need for this
'if'. */
if (0 <= nstates + place)
bitset_set (pos_set, nstates + place);
base[order[i]] = place;
}
@@ -754,7 +763,7 @@ pack_table (void)
base_ninf = table_ninf_remap (base, nvectors, BASE_MINIMUM);
table_ninf = table_ninf_remap (table, high + 1, ACTION_NUMBER_MINIMUM);
free (pos);
bitset_free (pos_set);
}