Split up the the long compute_assignment() function to make it easier
to reason about, particularly when it comes to what variables are used
later, and which aren't.
The grouping of "int" v.s. "int *" in function signatures is there to
make subsequent diffs smaller, if we're ever going to have a "nr"
member with a "size_t", but allocate e.g. "int *", and in anticipation
of the type names becoming longer than "int", which would require
re-wrapping.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
linear-assignment.c | 103 +++++++++++++++++++++++++++++++++-----------
linear-assignment.h | 3 +-
2 files changed, 79 insertions(+), 27 deletions(-)
diff --git a/linear-assignment.c b/linear-assignment.c
index 0c0786a63b6..7f85745e541 100644
--- a/linear-assignment.c
+++ b/linear-assignment.c
@@ -8,21 +8,12 @@
#define COST(column, row) cost[(column) + column_count * (row)]
-/*
- * The parameter `cost` is the cost matrix: the cost to assign column j to row
- * i is `cost[j + column_count * i].
- */
-void compute_assignment(int column_count, int row_count, int *cost,
- int *column2row, int *row2column)
+static void columns_reduction(int column_count, int row_count,
+ int *cost,
+ int *column2row, int *row2column,
+ int *v)
{
- int *v, *d;
- int *free_row, free_count = 0, saved_free_count, *pred, *col;
- int i, j, phase;
-
- assert(column_count > 1);
- memset(column2row, -1, sizeof(int) * column_count);
- memset(row2column, -1, sizeof(int) * row_count);
- ALLOC_ARRAY(v, column_count);
+ int i, j;
/* column reduction */
for (j = column_count - 1; j >= 0; j--) {
@@ -42,13 +33,21 @@ void compute_assignment(int column_count, int row_count, int *cost,
column2row[j] = -1;
}
}
+}
+
+static void reduction_transfer(int column_count, int row_count,
+ int *cost,
+ int *free_row, int *free_count,
+ int *column2row, int *row2column,
+ int *v)
+{
+ int i, j;
/* reduction transfer */
- ALLOC_ARRAY(free_row, row_count);
for (i = 0; i < row_count; i++) {
int j1 = row2column[i];
if (j1 == -1)
- free_row[free_count++] = i;
+ free_row[(*free_count)++] = i;
else if (j1 < -1)
row2column[i] = -2 - j1;
else {
@@ -59,21 +58,25 @@ void compute_assignment(int column_count, int row_count, int *cost,
v[j1] -= min;
}
}
+}
- if (free_count ==
- (column_count < row_count ? row_count - column_count : 0)) {
- free(v);
- free(free_row);
- return;
- }
+static void augmenting_row_reduction(int column_count,
+ int *cost,
+ int *column2row, int *row2column,
+ int *free_row, int *free_count, int *saved_free_count,
+ int *v)
+{
+ int phase;
/* augmenting row reduction */
for (phase = 0; phase < 2; phase++) {
+ int i;
int k = 0;
- saved_free_count = free_count;
- free_count = 0;
- while (k < saved_free_count) {
+ *saved_free_count = *free_count;
+ *free_count = 0;
+ while (k < *saved_free_count) {
+ int j;
int u1, u2;
int j1 = 0, j2, i0;
@@ -112,12 +115,24 @@ void compute_assignment(int column_count, int row_count, int *cost,
if (u1 < u2)
free_row[--k] = i0;
else
- free_row[free_count++] = i0;
+ free_row[(*free_count)++] = i0;
}
row2column[i] = j1;
column2row[j1] = i;
}
}
+}
+
+static void augmentation(int column_count,
+ int *cost,
+ int *column2row, int *row2column,
+ int *free_row, int free_count,
+ int *v)
+{
+ int i, j;
+ int *d;
+ int *pred, *col;
+ int saved_free_count;
/* augmentation */
saved_free_count = free_count;
@@ -197,6 +212,42 @@ void compute_assignment(int column_count, int row_count, int *cost,
free(col);
free(pred);
free(d);
+}
+
+/*
+ * The parameter `cost` is the cost matrix: the cost to assign column j to row
+ * i is `cost[j + column_count * i].
+ */
+void compute_assignment(int column_count, int row_count,
+ int *cost,
+ int *column2row, int *row2column)
+{
+ int *v;
+ int *free_row, free_count = 0, saved_free_count;
+
+ assert(column_count > 1);
+ memset(column2row, -1, sizeof(int) * column_count);
+ memset(row2column, -1, sizeof(int) * row_count);
+ ALLOC_ARRAY(v, column_count);
+
+ columns_reduction(column_count, row_count, cost, column2row,
+ row2column, v);
+
+ ALLOC_ARRAY(free_row, row_count);
+ reduction_transfer(column_count, row_count, cost, free_row,
+ &free_count, column2row, row2column, v);
+ if (free_count ==
+ (column_count < row_count ? row_count - column_count : 0))
+ goto cleanup;
+
+ augmenting_row_reduction(column_count, cost, column2row,
+ row2column, free_row, &free_count,
+ &saved_free_count,v);
+
+ augmentation(column_count, cost, column2row, row2column,
+ free_row, free_count, v);
+
+cleanup:
free(v);
free(free_row);
}
diff --git a/linear-assignment.h b/linear-assignment.h
index 1dfea766290..ef9946bdbfc 100644
--- a/linear-assignment.h
+++ b/linear-assignment.h
@@ -13,7 +13,8 @@
* assignments (-1 for unassigned, which can happen only if column_count !=
* row_count).
*/
-void compute_assignment(int column_count, int row_count, int *cost,
+void compute_assignment(int column_count, int row_count,
+ int *cost,
int *column2row, int *row2column);
/* The maximal cost in the cost matrix (to prevent integer overflows). */
--
2.34.1.930.g0f9292b224d
