1 files changed, 146 insertions, 0 deletions
diff --git a/src/misc/espresso/sparse.c b/src/misc/espresso/sparse.c
new file mode 100644
index 00000000..137ce7c1
--- /dev/null
+++ b/src/misc/espresso/sparse.c
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+/*
+ * Revision Control Information
+ *
+ * $Source$
+ * $Author$
+ * $Revision$
+ * $Date$
+ *
+ */
+/*
+    module: sparse.c
+
+    make_sparse is a last-step cleanup to reduce the total number
+    of literals in the cover.
+
+    This is done by reducing the "sparse" variables (using a modified
+    version of irredundant rather than reduce), followed by expanding
+    the "dense" variables (using modified version of expand).
+*/
+
+#include "espresso.h"
+
+pcover make_sparse(F, D, R)
+pcover F, D, R;
+{
+    cost_t cost, best_cost;
+
+    cover_cost(F, &best_cost);
+
+    do {
+    EXECUTE(F = mv_reduce(F, D), MV_REDUCE_TIME, F, cost);
+    if (cost.total == best_cost.total)
+        break;
+    copy_cost(&cost, &best_cost);
+
+    EXECUTE(F = expand(F, R, TRUE), RAISE_IN_TIME, F, cost);
+    if (cost.total == best_cost.total)
+        break;
+    copy_cost(&cost, &best_cost);
+    } while (force_irredundant);
+
+    return F;
+}
+
+/*
+    mv_reduce -- perform an "optimal" reduction of the variables which
+    we desire to be sparse
+
+    This could be done using "reduce" and then saving just the desired
+    part of the reduction.  Instead, this version uses IRRED to find
+    which cubes of an output are redundant.  Note that this gets around
+    the cube-ordering problem.
+
+    In normal use, it is expected that the cover is irredundant and
+    hence no cubes will be reduced to the empty cube (however, this is
+    checked for and such cubes will be deleted)
+*/
+
+pcover
+mv_reduce(F, D)
+pcover F, D;
+{
+    register int i, var;
+    register pcube p, p1, last;
+    int index;
+    pcover F1, D1;
+    pcube *F_cube_table;
+
+    /* loop for each multiple-valued variable */
+    for(var = 0; var < cube.num_vars; var++) {
+
+    if (cube.sparse[var]) {
+
+        /* loop for each part of the variable */
+        for(i = cube.first_part[var]; i <= cube.last_part[var]; i++) {
+
+        /* remember mapping of F1 cubes back to F cubes */
+        F_cube_table = ALLOC(pcube, F->count);
+
+        /* 'cofactor' against part #i of variable #var */
+        F1 = new_cover(F->count);
+        foreach_set(F, last, p) {
+            if (is_in_set(p, i)) {
+            F_cube_table[F1->count] = p;
+            p1 = GETSET(F1, F1->count++);
+            (void) set_diff(p1, p, cube.var_mask[var]);
+            set_insert(p1, i);
+            }
+        }
+
+        /* 'cofactor' against part #i of variable #var */
+        /* not really necessary -- just more efficient ? */
+        D1 = new_cover(D->count);
+        foreach_set(D, last, p) {
+            if (is_in_set(p, i)) {
+            p1 = GETSET(D1, D1->count++);
+            (void) set_diff(p1, p, cube.var_mask[var]);
+            set_insert(p1, i);
+            }
+        }
+
+        mark_irredundant(F1, D1);
+
+        /* now remove part i from cubes which are redundant */
+        index = 0;
+        foreach_set(F1, last, p1) {
+            if (! TESTP(p1, ACTIVE)) {
+            p = F_cube_table[index];
+
+            /*   don't reduce a variable which is full
+             *   (unless it is the output variable)
+             */
+            if (var == cube.num_vars-1 ||
+                 ! setp_implies(cube.var_mask[var], p)) {
+                set_remove(p, i);
+            }
+            RESET(p, PRIME);
+            }
+            index++;
+        }
+
+        free_cover(F1);
+        free_cover(D1);
+        FREE(F_cube_table);
+        }
+    }
+    }
+
+    /* Check if any cubes disappeared */
+    (void) sf_active(F);
+    for(var = 0; var < cube.num_vars; var++) {
+    if (cube.sparse[var]) {
+        foreach_active_set(F, last, p) {
+        if (setp_disjoint(p, cube.var_mask[var])) {
+            RESET(p, ACTIVE);
+            F->active_count--;
+        }
+        }
+    }
+    }
+
+    if (F->count != F->active_count) {
+    F = sf_inactive(F);
+    }
+    return F;
+}