From 4812c90424dfc40d26725244723887a2d16ddfd9 Mon Sep 17 00:00:00 2001
From: Alan Mishchenko <alanmi@berkeley.edu>
Date: Mon, 1 Oct 2007 08:01:00 -0700
Subject: Version abc71001

---
 src/misc/espresso/indep.c | 134 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 src/misc/espresso/indep.c

(limited to 'src/misc/espresso/indep.c')

diff --git a/src/misc/espresso/indep.c b/src/misc/espresso/indep.c
new file mode 100644
index 00000000..10b363a0
--- /dev/null
+++ b/src/misc/espresso/indep.c
@@ -0,0 +1,134 @@
+/*
+ * Revision Control Information
+ *
+ * $Source$
+ * $Author$
+ * $Revision$
+ * $Date$
+ *
+ */
+#include "mincov_int.h"
+
+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;
+}
-- 
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