dotgen: use a bit array for 'layerWidthInfo_t.removed'

By using a `bitarray_t` instead of an array of integers for this array of
boolean values, we swap a 32-bits-per-boolean representation for a
1-bit-per-boolean representation. This reduces heap pressure, and in the case of
smaller arrays avoids heap allocation altogether.

diff --git a/lib/dotgen/aspect.c b/lib/dotgen/aspect.c
index 46536cab65edd61ad6b98acd3c69d11a5fee19cb..9d09e30f14cbae051d93bfd6e0ae9c97a03f4569 100644 (file)
--- a/lib/dotgen/aspect.c
+++ b/lib/dotgen/aspect.c
@@ -8,7 +8,10 @@
  * Contributors: Details at https://graphviz.org
  *************************************************************************/
 
+#include <assert.h>
+#include <cgraph/bitarray.h>
 #include <dotgen/dot.h>
+#include <stddef.h>
 
 /*
  * Author: Mohammad T. Irfan
@@ -151,7 +154,7 @@ int countDummyNodes(graph_t * g)
 typedef struct layerWidthInfo_t {
     int layerNumber;
     nodeGroup_t **nodeGroupsInLayer;
-    int *removed;              /* is the node group removed? */
+    bitarray_t removed; // is the node group removed?
     int nNodeGroupsInLayer;
     int nDummyNodes;
     double width;
@@ -184,7 +187,7 @@ static void computeLayerWidths(graph_t * g)
                }
                free(layerWidthInfo[i].nodeGroupsInLayer);
            }
-           free(layerWidthInfo[i].removed);
+           bitarray_reset(&layerWidthInfo[i].removed);
        }
 
        free(layerWidthInfo);
@@ -198,7 +201,8 @@ static void computeLayerWidths(graph_t * g)
        layerWidthInfo[i].nodeGroupsInLayer =
            N_NEW(nNodeGroups, nodeGroup_t *);
 
-       layerWidthInfo[i].removed = N_NEW(nNodeGroups, int);
+       assert(nNodeGroups >= 0);
+       layerWidthInfo[i].removed = bitarray_new_or_exit((size_t)nNodeGroups);
 
        layerWidthInfo[i].layerNumber = i;
        layerWidthInfo[i].nNodeGroupsInLayer = 0;
@@ -368,7 +372,7 @@ static void reduceMaxWidth2(graph_t * g)
     w = 0;
 
     for (i = 0; i < limit + rem; i++) {
-       if (layerWidthInfo[maxLayerIndex].removed[i]) {
+       if (bitarray_get(layerWidthInfo[maxLayerIndex].removed, i)) {
            rem++;
            continue;
        }
@@ -409,7 +413,7 @@ static void reduceMaxWidth2(graph_t * g)
            /* the following code updates the layer width information. The 
             * update is not useful in the current version of the heuristic.
             */
-           layerWidthInfo[maxLayerIndex].removed[i] = 1;
+           bitarray_set(&layerWidthInfo[maxLayerIndex].removed, i, true);
            rem2++;
            layerWidthInfo[maxLayerIndex].nNodeGroupsInLayer--;
            /* SHOULD BE INCREASED BY THE SUM OF INDEG OF ALL NODES IN GROUP */