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bc27b094af
the topological sort. "make test" or "make tests" invokes the regression tests, "make valgrind" runs them under valgrind's watchful eyes. - fped.c (usage, main): added option -T to force batch mode (for regression testing) - Makefile, test/Common: added regression test infrastructure - test/tsort: test cases for the topological sort - README: added pointer to test/tsort git-svn-id: http://svn.openmoko.org/trunk/eda/fped@5943 99fdad57-331a-0410-800a-d7fa5415bdb3
163 lines
4.0 KiB
C
163 lines
4.0 KiB
C
/*
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* tsort.c - Topological sort
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*
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* Written 2010 by Werner Almesberger
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* Copyright 2010 by Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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/*
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* We use a slight variation of Kahn's algorithm. The difference is that we add
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* a priority. Edges with the highest priority get selected before edges with
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* lower priority.
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*
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* We maintain the initial list of nodes in the order in which they were added.
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* Therefore, the first node with inbound edges will always be sorted first.
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* E.g., the root frame.
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*
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* add_node and add_edge can be invoked multiple times with the same
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* parameters. In the case of add_node, simply the existing node is returned.
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* In the case of add_edge, the new edge's priority is added to the priority of
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* the previous edges.
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*
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* Priority is accumulated in a node until the node is output. If a node has
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* the "decay" flag set, it resets the priorities of all other nodes when
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* output. E.g., when outputting a vector, all priorities accumulated from
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* previous vectors (towards referencing them with ".") lose their effect.
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*
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* Last but not least, the algorithm is stable: a pre-existing order that
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* conflicts neither with the partial order nor the priorities is preserved.
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*
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* Thus, we have the following sorting criteria, in decreasing importance:
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* - the destination if an edge never precedes its origin
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* - higher priority comes before lower priority
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* - earlier add_node comes before later
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <limits.h>
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#include "util.h"
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#include "tsort.h"
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struct edge {
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struct node *to;
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int priority; /* edge priority */
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struct edge *next;
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};
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struct node {
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void *user;
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struct edge *edges; /* outbound edges */
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int incoming; /* number of incoming edges */
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int priority; /* cumulative node priority */
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int decay; /* all node prio. decay after issuing this */
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struct node *next;
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};
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struct tsort {
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struct node *nodes;
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struct node **next_node;
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int n_nodes;
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};
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void add_edge(struct node *from, struct node *to, int priority)
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{
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struct edge **edge;
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for (edge = &from->edges; *edge; edge = &(*edge)->next)
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if ((*edge)->to == to) {
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(*edge)->priority += priority;
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return;
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}
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*edge = alloc_type(struct edge);
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(*edge)->to = to;
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(*edge)->priority = priority;
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(*edge)->next = NULL;
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to->incoming++;
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}
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struct node *add_node(struct tsort *tsort, void *user, int decay)
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{
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struct node *node;
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for (node = tsort->nodes; node; node = node->next)
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if (node->user == user)
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return node;
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node = alloc_type(struct node);
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node->user = user;
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node->edges = NULL;
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node->incoming = 0;
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node->priority = 0;
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node->decay = decay;
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node->next = NULL;
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*tsort->next_node = node;
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tsort->next_node = &node->next;
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tsort->n_nodes++;
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return node;
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}
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struct tsort *begin_tsort(void)
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{
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struct tsort *tsort;
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tsort = alloc_type(struct tsort);
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tsort->nodes = NULL;
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tsort->next_node = &tsort->nodes;
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tsort->n_nodes = 0;
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return tsort;
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}
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void **end_tsort(struct tsort *tsort)
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{
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struct node **walk, **first, *node;
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struct edge *edge;
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void **res;
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int n = 0;
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res = alloc_size(sizeof(void *)*(tsort->n_nodes+1));
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while (1) {
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first = NULL;
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for (walk = &tsort->nodes; *walk; walk = &(*walk)->next) {
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if ((*walk)->incoming)
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continue;
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if (!first || (*first)->priority < (*walk)->priority)
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first = walk;
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}
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if (!first)
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break;
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if ((*first)->decay)
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for (node = tsort->nodes; node; node = node->next)
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node->priority = 0;
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node = *first;
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*first = node->next;
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res[n++] = node->user;
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while (node->edges) {
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edge = node->edges;
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edge->to->incoming--;
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edge->to->priority += edge->priority;
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node->edges = edge->next;
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free(edge);
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}
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free(node);
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}
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if (tsort->nodes) {
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fprintf(stderr, "cycle detected in partial order\n");
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abort();
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}
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free(tsort);
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res[n] = NULL;
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return res;
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}
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