The Jonker-Volgenant algorithm was implemented to answer questions such
as: given two different versions of a topic branch (or iterations of a
patch series), what is the best pairing of commits/patches between the
different versions?
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
Makefile | 1 +
hungarian.c | 205 ++++++++++++++++++++++++++++++++++++++++++++++++++++
hungarian.h | 19 +++++
3 files changed, 225 insertions(+)
create mode 100644 hungarian.c
create mode 100644 hungarian.h
diff --git a/Makefile b/Makefile
index 50da82b0169..96f2e76a904 100644
--- a/Makefile
+++ b/Makefile
@@ -829,6 +829,7 @@ LIB_OBJS += gpg-interface.o
LIB_OBJS += graph.o
LIB_OBJS += grep.o
LIB_OBJS += hashmap.o
+LIB_OBJS += hungarian.o
LIB_OBJS += help.o
LIB_OBJS += hex.o
LIB_OBJS += ident.o
diff --git a/hungarian.c b/hungarian.c
new file mode 100644
index 00000000000..346299a97d9
--- /dev/null
+++ b/hungarian.c
@@ -0,0 +1,205 @@
+/*
+ * Based on: Jonker, R., & Volgenant, A. (1987). <i>A shortest augmenting path
+ * algorithm for dense and sparse linear assignment problems</i>. Computing,
+ * 38(4), 325-340.
+ */
+#include "cache.h"
+#include "hungarian.h"
+#include <float.h>
+
+#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].
+ */
+int compute_assignment(int column_count, int row_count, double *cost,
+ int *column2row, int *row2column)
+{
+ double *v = xmalloc(sizeof(double) * column_count), *d;
+ int *free_row, free_count = 0, saved_free_count, *pred, *col;
+ int i, j, phase;
+
+ memset(column2row, -1, sizeof(int) * column_count);
+ memset(row2column, -1, sizeof(int) * row_count);
+
+ /* column reduction */
+ for (j = column_count - 1; j >= 0; j--) {
+ int i1 = 0;
+
+ for (i = 1; i < row_count; i++)
+ if (COST(j, i1) > COST(j, i))
+ i1 = i;
+ v[j] = COST(j, i1);
+ if (row2column[i1] == -1) {
+ /* row i1 unassigned */
+ row2column[i1] = j;
+ column2row[j] = i1;
+ } else {
+ if (row2column[i1] >= 0)
+ row2column[i1] = -2 - row2column[i1];
+ column2row[j] = -1;
+ }
+ }
+
+ /* reduction transfer */
+ free_row = xmalloc(sizeof(int) * row_count);
+ for (int i = 0; i < row_count; i++) {
+ int j1 = row2column[i];
+ if (j1 == -1)
+ free_row[free_count++] = i;
+ else if (j1 < -1)
+ row2column[i] = -2 - j1;
+ else {
+ double min = COST(!j1, i) - v[!j1];
+ for (j = 1; j < column_count; j++)
+ if (j != j1 && min > COST(j, i) - v[j])
+ min = COST(j, i) - v[j];
+ v[j1] -= min;
+ }
+ }
+
+ if (free_count ==
+ (column_count < row_count ? row_count - column_count : 0)) {
+ free(v);
+ free(free_row);
+ return 0;
+ }
+
+ /* augmenting row reduction */
+ for (phase = 0; phase < 2; phase++) {
+ int k = 0;
+
+ saved_free_count = free_count;
+ free_count = 0;
+ while (k < saved_free_count) {
+ double u1, u2;
+ int j1 = 0, j2, i0;
+
+ i = free_row[k++];
+ u1 = COST(j1, i) - v[j1];
+ j2 = -1;
+ u2 = DBL_MAX;
+ for (j = 1; j < column_count; j++) {
+ double c = COST(j, i) - v[j];
+ if (u2 > c) {
+ if (u1 < c) {
+ u2 = c;
+ j2 = j;
+ } else {
+ u2 = u1;
+ u1 = c;
+ j2 = j1;
+ j1 = j;
+ }
+ }
+ }
+ if (j2 < 0) {
+ j2 = j1;
+ u2 = u1;
+ }
+
+ i0 = column2row[j1];
+ if (u1 < u2)
+ v[j1] -= u2 - u1;
+ else if (i0 >= 0) {
+ j1 = j2;
+ i0 = column2row[j1];
+ }
+
+ if (i0 >= 0) {
+ if (u1 < u2)
+ free_row[--k] = i0;
+ else
+ free_row[free_count++] = i0;
+ }
+ row2column[i] = j1;
+ column2row[j1] = i;
+ }
+ }
+
+ /* augmentation */
+ saved_free_count = free_count;
+ d = xmalloc(sizeof(double) * column_count);
+ pred = xmalloc(sizeof(int) * column_count);
+ col = xmalloc(sizeof(int) * column_count);
+ for (free_count = 0; free_count < saved_free_count; free_count++) {
+ int i1 = free_row[free_count], low = 0, up = 0, last, k;
+ double min, c, u1;
+
+ for (j = 0; j < column_count; j++) {
+ d[j] = COST(j, i1) - v[j];
+ pred[j] = i1;
+ col[j] = j;
+ }
+
+ j = -1;
+ do {
+ last = low;
+ min = d[col[up++]];
+ for (k = up; k < column_count; k++) {
+ j = col[k];
+ c = d[j];
+ if (c <= min) {
+ if (c < min) {
+ up = low;
+ min = c;
+ }
+ col[k] = col[up];
+ col[up++] = j;
+ }
+ }
+ for (k = low; k < up; k++)
+ if (column2row[col[k]] == -1)
+ goto update;
+
+ /* scan a row */
+ do {
+ int j1 = col[low++];
+
+ i = column2row[j1];
+ u1 = COST(j1, i) - v[j1] - min;
+ for (k = up; k < column_count; k++) {
+ j = col[k];
+ c = COST(j, i) - v[j] - u1;
+ if (c < d[j]) {
+ d[j] = c;
+ pred[j] = i;
+ if (c == min) {
+ if (column2row[j] == -1)
+ goto update;
+ col[k] = col[up];
+ col[up++] = j;
+ }
+ }
+ }
+ } while (low != up);
+ } while (low == up);
+
+update:
+ /* updating of the column pieces */
+ for (k = 0; k < last; k++) {
+ int j1 = col[k];
+ v[j1] += d[j1] - min;
+ }
+
+ /* augmentation */
+ do {
+ if (j < 0)
+ BUG("negative j: %d", j);
+ i = pred[j];
+ column2row[j] = i;
+ k = j;
+ j = row2column[i];
+ row2column[i] = k;
+ } while (i1 != i);
+ }
+
+ free(col);
+ free(pred);
+ free(d);
+ free(v);
+ free(free_row);
+
+ return 0;
+}
diff --git a/hungarian.h b/hungarian.h
new file mode 100644
index 00000000000..e7cee4bb039
--- /dev/null
+++ b/hungarian.h
@@ -0,0 +1,19 @@
+#ifndef HUNGARIAN_H
+#define HUNGARIAN_H
+
+/*
+ * Compute an assignment of columns -> rows (and vice versa) such that every
+ * column is assigned to at most one row (and vice versa) minimizing the
+ * overall cost.
+ *
+ * The parameter `cost` is the cost matrix: the cost to assign column j to row
+ * i is `cost[j + column_count * i].
+ *
+ * The arrays column2row and row2column will be populated with the respective
+ * assignments (-1 for unassigned, which can happen only if column_count !=
+ * row_count).
+ */
+int compute_assignment(int column_count, int row_count, double *cost,
+ int *column2row, int *row2column);
+
+#endif
--
2.17.0.395.g6a618d6010f.dirty
