trace-graph: Add a little better pid hash function

This adds a little better pid hash function that will give a
better difference in colors for tasks than the previous hash
algorithm.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 23 insertions, 5 deletions

diff --git a/trace-graph.c b/trace-graph.c
index 7044fac..8692fe7 100644
--- a/trace-graph.c
+++ b/trace-graph.c
@@ -735,9 +735,27 @@ button_release_event(GtkWidget *widget, GdkEventMotion *event, gpointer data)
 
 static gint do_hash(gint val)
 {
-        return (val + (val << 4) + (val << 8) + (val << 12) + 
-                (val << 16) + (val << 20) + (val << 24) +
-                (val << 28)) * 3;
+        int i, x, y;
+        int total = 0;
+
+        if (!val)
+                return 0;
+
+        for (i = 0; i < 32; i++) {
+                y = 0;
+                if (val & (1 << i)) {
+                        for (x = 0; x < ((i+1) * 13); x++) {
+                                y |= 1 << ((x * 23) & 31);
+                        }
+                } else {
+                        for (x = 0; x < ((i+1) * 7); x++) {
+                                y |= 1 << ((x * 17) & 31);
+                        }
+                }
+                total += y;
+        }
+
+        return total;
 }
 
 static void set_color_by_pid(GtkWidget *widget, GdkGC *gc, gint pid)
@@ -901,9 +919,9 @@ static void draw_cpu(struct graph_info *ginfo, gint cpu,
 
                         last_x = x;
                         last_pid = pid;
-                }
 
-                set_color_by_pid(ginfo->draw, gc, pid);
+                        set_color_by_pid(ginfo->draw, gc, pid);
+                }
 
                 gdk_draw_line(ginfo->curr_pixmap, gc, // ginfo->draw->style->black_gc,
                               x, CPU_TOP(cpu), x, CPU_BOTTOM(cpu));