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520077bd41
git-svn-id: https://tesseract-ocr.googlecode.com/svn/trunk@164 d0cd1f9f-072b-0410-8dd7-cf729c803f20
425 lines
13 KiB
C++
425 lines
13 KiB
C++
/* -*-C-*-
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********************************************************************************
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*
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* File: reduce.cpp
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* Description: Functions to reduce a TRIE into a DAWG
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* Author: Mark Seaman, OCR Technology
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* Created: Fri Oct 16 14:37:00 1987
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* Modified: Wed Jun 19 16:51:29 1991 (Mark Seaman) marks@hpgrlt
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* Language: C
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* Package: N/A
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* Status: Reusable Software Component
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*
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* (c) Copyright 1987, Hewlett-Packard Company, all rights reserved.
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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** http://www.apache.org/licenses/LICENSE-2.0
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*
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********************************************************************************
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*/
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/*
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----------------------------------------------------------------------
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I n c l u d e s
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----------------------------------------------------------------------
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*/
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#include "reduce.h"
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#include "makedawg.h"
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#include "cutil.h"
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#ifdef __UNIX__
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#include <assert.h>
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#endif
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/*
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----------------------------------------------------------------------
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T y p e s
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----------------------------------------------------------------------
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*/
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/*
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----------------------------------------------------------------------
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V a r i a b l e s
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----------------------------------------------------------------------
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*/
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static inT32 debug_1 = 0;
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/*
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----------------------------------------------------------------------
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M a c r o s
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----------------------------------------------------------------------
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*/
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/*
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----------------------------------------------------------------------
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F u n c t i o n s
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----------------------------------------------------------------------
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*/
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/**********************************************************************
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* collapse_source_nodes
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*
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* A pair of edges has been found that can be reduced. This function
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* accomplishes that reduction by collapsing the two nodes into a
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* single node.
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**********************************************************************/
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void collapse_source_nodes (EDGE_ARRAY dawg,
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NODE_REF source_node_1,
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NODE_REF source_node_2,
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NODE_REF dest_node,
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inT32 max_num_edges,
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inT32 reserved_edges) {
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inT32 num_links;
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EDGE_REF edge;
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/* NODE_REF new_source_1; */
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num_links = num_forward_edges (dawg, source_node_2);
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/* if (debug_1)
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printf ("Node = %d, Input 1 = %d, Input 2 = %6d, num_links = %d\n",
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dest_node, source_node_1, source_node_2, num_links);
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if (debug) {
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printf ("Node = %d, Input 1 = %d, Input 2 = %6d, num_links = %d\n",
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dest_node, source_node_1, source_node_2, num_links);
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print_dawg_node (dawg, source_node_1);
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print_dawg_node (dawg, source_node_2);
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new_line ();
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}
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*/
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/* Remove forward links in */
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edge = source_node_2; /* source_node_2 - dest_node */
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if (forward_edge (dawg, edge)) {
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do {
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remove_edge_linkage (dawg, dest_node, source_node_2,
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BACKWARD_EDGE,
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edge_letter (dawg, edge),
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end_of_word (dawg, edge));
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} edge_loop (dawg, edge);
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}
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/* Fix backward links */
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edge = source_node_2; /* in source_node_2 */
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edge += num_forward_edges (dawg, source_node_2);
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if (backward_edge (dawg, edge)) {
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do {
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move_node_if_needed (dawg, &source_node_1,
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max_num_edges, reserved_edges);
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add_edge_linkage (dawg, source_node_1, next_node (dawg, edge),
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BACKWARD_EDGE,
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edge_letter (dawg, edge),
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end_of_word (dawg, edge));
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/* Node moved */
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relocate_edge (dawg, next_node (dawg, edge),
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source_node_2, source_node_1);
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} edge_loop (dawg, edge);
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}
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delete_node (dawg, source_node_2);
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/* if (debug) {
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printf ("Number of edges source = %d, dest = %d\n",
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edges_in_node (dawg, new_source_1),
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edges_in_node (dawg, dest_node));
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print_int ("Number of edges = ", edges_in_node (dawg, dest_node));
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print_dawg_node (dawg, new_source_1);
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print_string ("_________________________________________");
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new_line ();
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}
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*/
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}
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/**********************************************************************
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* eliminate_redundant_edges
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*
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* Compare these two edges in this node to see if they point to two
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* nodes that could be collapsed. If they do, then perform the
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* reduction and return TRUE. If not, return FALSE.
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**********************************************************************/
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inT32 eliminate_redundant_edges (EDGE_ARRAY dawg,
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NODE_REF node,
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EDGE_REF edge_1,
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EDGE_REF edge_2,
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inT32 max_num_edges,
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inT32 reserved_edges) {
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static inT32 elim_count = 0;
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static inT32 keep_count = 0;
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if (same_output (dawg,
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next_node (dawg, edge_1),
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next_node (dawg, edge_2))) {
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elim_count++;
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collapse_source_nodes (dawg,
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next_node (dawg, edge_1),
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next_node (dawg, edge_2),
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node,
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max_num_edges, reserved_edges);
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/* if (debug_1) {
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printf ("Collapsing node %d\n", node);
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print_dawg_node (dawg, node);
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printf ("Candidate edges = %d, %d\n", edge_1, edge_2);
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printf ("Candidate nodes = %d, %d\n\n",
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next_node (dawg, edge_1), next_node (dawg, edge_2));
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new_line ();
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}
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*/
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return (TRUE);
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}
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else {
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keep_count++;
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}
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return (FALSE);
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}
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/**********************************************************************
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* letter_order
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*
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* Compare two edges to see which one of the letters is larger.
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**********************************************************************/
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inT32 letter_order (const void* edge1_ptr,
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const void* edge2_ptr) {
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if (letter_of_edge(*((EDGE_RECORD*) edge1_ptr)) <
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letter_of_edge(*((EDGE_RECORD*) edge2_ptr)))
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return (-1);
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if (letter_of_edge(*((EDGE_RECORD*) edge1_ptr)) >
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letter_of_edge(*((EDGE_RECORD*) edge2_ptr)))
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return (1);
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return (0);
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}
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/*
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printf ("%c%c %c%c ",
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edge1.letter, (edge1.flags & WORD_END_FLAG ? '*' : ' '),
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edge2.letter, (edge2.flags & WORD_END_FLAG ? '*' : ' '));
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printf ("\n");
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printf ("+\n");
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printf ("-\n");
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*/
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void print_n_edges (EDGE_RECORD *edge1,
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inT32 n) {
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EDGE_RECORD *edge;
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edge = edge1;
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while (n-- > 0) {
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printf ("%c ", letter_of_edge(edge[0]));
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edge++;
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}
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new_line ();
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}
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/**********************************************************************
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* reduce_lettered_edges
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*
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* The edge parameter is pointing to the first edge in a group of edges
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* in this node with a particular letter value. Look through these edges
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* to see if any of them can be collapsed. If so do it. When all edges
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* with this letter have been reduced then return to the caller.
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* If further reduction is possible with this same letter then the
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* edge parameter is not incremented. When no further reduction is
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* possible then FALSE is returned.
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**********************************************************************/
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inT32 reduce_lettered_edges (EDGE_ARRAY dawg,
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EDGE_REF *edge,
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NODE_REF node,
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NODE_MARKER reduced_nodes,
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inT32 max_num_edges,
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inT32 reserved_edges) {
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EDGE_REF edge_1;
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EDGE_REF edge_2;
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inT32 fixed_one;
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inT32 did_something = FALSE;
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if (debug_1)
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printf ("reduce_lettered_edges (edge=" REFFORMAT ")\n", *edge);
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/* Loop for each back edge */
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edge_1 = *edge;
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while ((! last_edge (dawg, edge_1)) &&
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edge_letter (dawg, edge_1) == edge_letter (dawg, *edge)) {
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edge_2 = edge_1 + 1; /* Compare all back edges */
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do {
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if (edge_letter (dawg, edge_1) < edge_letter (dawg, edge_2))
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break;
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if (debug_1) {
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printf (REFFORMAT " (%c), " REFFORMAT " (%c) ",
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edge_1, edge_letter (dawg, edge_1),
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edge_2, edge_letter (dawg, edge_2));
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}
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if (edge_2 != edge_1 &&
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edge_letter (dawg, edge_2) == edge_letter (dawg, edge_1) &&
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end_of_word (dawg, edge_2) == end_of_word (dawg, edge_1) &&
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eliminate_redundant_edges (dawg, node, edge_1, edge_2,
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max_num_edges, reserved_edges)) {
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reduced_nodes [next_node (dawg, edge_1)] = 0;
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fixed_one = TRUE;
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did_something = TRUE;
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}
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else {
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if (debug_1) printf (" .");
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fixed_one = FALSE;
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}
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if (debug_1) printf ("\n");
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} while (fixed_one ?
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edge_occupied (dawg, edge_2) :
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(! last_edge (dawg, edge_2++)));
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edge_1++;
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}
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if (! did_something) {
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if (last_edge (dawg, edge_1))
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return (FALSE);
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else
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*edge = edge_1;
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}
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return (TRUE);
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}
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/**********************************************************************
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* reduce_node_input
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*
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* Eliminate any redundant edges from this node in the DAWG.
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**********************************************************************/
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void reduce_node_input (EDGE_ARRAY dawg,
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NODE_REF node,
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NODE_MARKER reduced_nodes,
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inT32 max_num_edges,
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inT32 reserved_edges) {
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EDGE_REF edge_1;
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inT32 forward_edges = num_forward_edges (dawg, node);
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inT32 backward_edges = edges_in_node (dawg, node) - forward_edges;
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static inT32 num_nodes_reduced = 0;
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if (debug_1) {
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printf ("reduce_node_input (node=" REFFORMAT ")\n", node);
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print_dawg_node (dawg, node);
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}
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if (++num_nodes_reduced % 100 == 0) {
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printf ("%d nodes reduced\n", num_nodes_reduced);
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if (debug_1 && num_nodes_reduced % 1000 == 0) {
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write_full_dawg ("temp-save", dawg, max_num_edges);
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}
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}
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qsort ((void *) &edge_of (dawg, node + forward_edges),
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backward_edges,
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sizeof (EDGE_RECORD),
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letter_order);
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/* if (debug_1) {
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printf ("__________________________\n");
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print_dawg_node (dawg, node);
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}
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*/
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edge_1 = node + forward_edges;
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while (reduce_lettered_edges (dawg, &edge_1, node, reduced_nodes,
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max_num_edges, reserved_edges));
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reduced_nodes [node] = 1; /* Mark as reduced */
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if (debug_1) {
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printf ("After reduction:\n");
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print_dawg_node (dawg, node);
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}
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edge_1 = node + num_forward_edges (dawg, node); /* Reduce next level */
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if (backward_edge (dawg, edge_1)) {
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do {
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if (next_node (dawg, edge_1) &&
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reduced_nodes [next_node (dawg, edge_1)] == 0)
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reduce_node_input (dawg, next_node (dawg, edge_1), reduced_nodes,
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max_num_edges, reserved_edges);
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} edge_loop (dawg, edge_1);
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}
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}
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/**********************************************************************
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* same_output
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*
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* Check to see if these two nodes have identical output. If so then
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* they can be collapsed into a single node.
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**********************************************************************/
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inT32 same_output (EDGE_ARRAY dawg,
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NODE_REF node1,
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NODE_REF node2) {
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if (debug_1) printf ("Edge nodes = " REFFORMAT " , " \
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REFFORMAT " \n", node1, node2);
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if (num_forward_edges (dawg, node1) == 1 &&
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num_forward_edges (dawg, node2) == 1) {
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if (debug_1) printf (" * ");
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return (TRUE);
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}
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else {
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if (debug_1) {
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printf (" %d,%d \n",
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num_forward_edges (dawg, node1),
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num_forward_edges (dawg, node2));
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print_dawg_node (dawg, node1);
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print_dawg_node (dawg, node2);
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}
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return (FALSE);
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}
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}
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/**********************************************************************
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* trie_to_dawg
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*
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* Change a Trie data structure into a DAWG by eliminating the redund
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**********************************************************************/
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void trie_to_dawg (EDGE_ARRAY dawg,
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inT32 max_num_edges,
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inT32 reserved_edges) {
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NODE_MARKER reduced_nodes;
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inT32 x;
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max_new_attempts = 100000;
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compact_dawg (dawg, max_num_edges, reserved_edges);
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reduced_nodes = (NODE_MARKER) malloc (max_num_edges);
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for (x=0; x<max_num_edges; x++) reduced_nodes [x] = 0;
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reduce_node_input (dawg, 0, reduced_nodes, max_num_edges, reserved_edges);
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free (reduced_nodes);
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}
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