trace-graph: Replace hash looping with a faster hash

Did a little more research and found a nice hash that is quick
and pretty powerful. Based off of Paul Hsieh's super fast hash:

  http://www.azillionmonkeys.com/qed/hash.html

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

1 files changed, 21 insertions, 16 deletions

diff --git a/trace-graph.c b/trace-graph.c
index 8692fe7..b70e27d 100644
--- a/trace-graph.c
+++ b/trace-graph.c
@@ -735,27 +735,32 @@ button_release_event(GtkWidget *widget, GdkEventMotion *event, gpointer data)
 
 static gint do_hash(gint val)
 {
-        int i, x, y;
-        int total = 0;
+        int hash, tmp;
 
+        /* idle always gets black */
         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;
-        }
+        hash = 12546869;        /* random prime */
+
+        /*
+         * The following hash is based off of Paul Hsieh's super fast hash:
+         *  http://www.azillionmonkeys.com/qed/hash.html
+         */
+
+        hash += (val & 0xffff);
+        tmp = (val >> 16) ^ hash;
+        hash = (hash << 16) ^ tmp;
+        hash += hash >> 11;
+
+        hash ^= hash << 3;
+        hash += hash >> 5;
+        hash ^= hash << 4;
+        hash += hash >> 17;
+        hash ^= hash << 25;
+        hash += hash >> 6;
 
-        return total;
+        return hash;
 }
 
 static void set_color_by_pid(GtkWidget *widget, GdkGC *gc, gint pid)