mirror of https://github.com/YosysHQ/abc.git
140 lines
3.2 KiB
C
140 lines
3.2 KiB
C
/*
|
||
* Revision Control Information
|
||
*
|
||
* $Source$
|
||
* $Author$
|
||
* $Revision$
|
||
* $Date$
|
||
*
|
||
*/
|
||
#include "mincov_int.h"
|
||
|
||
ABC_NAMESPACE_IMPL_START
|
||
|
||
|
||
static sm_matrix *build_intersection_matrix();
|
||
|
||
|
||
#if 0
|
||
/*
|
||
* verify that all rows in 'indep' are actually independent !
|
||
*/
|
||
static int
|
||
verify_indep_set(A, indep)
|
||
sm_matrix *A;
|
||
sm_row *indep;
|
||
{
|
||
register sm_row *prow, *prow1;
|
||
register sm_element *p, *p1;
|
||
|
||
for(p = indep->first_col; p != 0; p = p->next_col) {
|
||
prow = sm_get_row(A, p->col_num);
|
||
for(p1 = p->next_col; p1 != 0; p1 = p1->next_col) {
|
||
prow1 = sm_get_row(A, p1->col_num);
|
||
if (sm_row_intersects(prow, prow1)) {
|
||
return 0;
|
||
}
|
||
}
|
||
}
|
||
return 1;
|
||
}
|
||
#endif
|
||
|
||
solution_t *
|
||
sm_maximal_independent_set(A, weight)
|
||
sm_matrix *A;
|
||
int *weight;
|
||
{
|
||
register sm_row *best_row, *prow;
|
||
register sm_element *p;
|
||
int least_weight;
|
||
sm_row *save;
|
||
sm_matrix *B;
|
||
solution_t *indep;
|
||
|
||
indep = solution_alloc();
|
||
B = build_intersection_matrix(A);
|
||
|
||
while (B->nrows > 0) {
|
||
/* Find the row which is disjoint from a maximum number of rows */
|
||
best_row = B->first_row;
|
||
for(prow = B->first_row->next_row; prow != 0; prow = prow->next_row) {
|
||
if (prow->length < best_row->length) {
|
||
best_row = prow;
|
||
}
|
||
}
|
||
|
||
/* Find which element in this row has least weight */
|
||
if (weight == NIL(int)) {
|
||
least_weight = 1;
|
||
} else {
|
||
prow = sm_get_row(A, best_row->row_num);
|
||
least_weight = weight[prow->first_col->col_num];
|
||
for(p = prow->first_col->next_col; p != 0; p = p->next_col) {
|
||
if (weight[p->col_num] < least_weight) {
|
||
least_weight = weight[p->col_num];
|
||
}
|
||
}
|
||
}
|
||
indep->cost += least_weight;
|
||
(void) sm_row_insert(indep->row, best_row->row_num);
|
||
|
||
/* Discard the rows which intersect this row */
|
||
save = sm_row_dup(best_row);
|
||
for(p = save->first_col; p != 0; p = p->next_col) {
|
||
sm_delrow(B, p->col_num);
|
||
sm_delcol(B, p->col_num);
|
||
}
|
||
sm_row_free(save);
|
||
}
|
||
|
||
sm_free(B);
|
||
|
||
/*
|
||
if (! verify_indep_set(A, indep->row)) {
|
||
fail("sm_maximal_independent_set: row set is not independent");
|
||
}
|
||
*/
|
||
return indep;
|
||
}
|
||
|
||
static sm_matrix *
|
||
build_intersection_matrix(A)
|
||
sm_matrix *A;
|
||
{
|
||
register sm_row *prow, *prow1;
|
||
register sm_element *p, *p1;
|
||
register sm_col *pcol;
|
||
sm_matrix *B;
|
||
|
||
/* Build row-intersection matrix */
|
||
B = sm_alloc();
|
||
for(prow = A->first_row; prow != 0; prow = prow->next_row) {
|
||
|
||
/* Clear flags on all rows we can reach from row 'prow' */
|
||
for(p = prow->first_col; p != 0; p = p->next_col) {
|
||
pcol = sm_get_col(A, p->col_num);
|
||
for(p1 = pcol->first_row; p1 != 0; p1 = p1->next_row) {
|
||
prow1 = sm_get_row(A, p1->row_num);
|
||
prow1->flag = 0;
|
||
}
|
||
}
|
||
|
||
/* Now record which rows can be reached */
|
||
for(p = prow->first_col; p != 0; p = p->next_col) {
|
||
pcol = sm_get_col(A, p->col_num);
|
||
for(p1 = pcol->first_row; p1 != 0; p1 = p1->next_row) {
|
||
prow1 = sm_get_row(A, p1->row_num);
|
||
if (! prow1->flag) {
|
||
prow1->flag = 1;
|
||
(void) sm_insert(B, prow->row_num, prow1->row_num);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
return B;
|
||
}
|
||
ABC_NAMESPACE_IMPL_END
|
||
|