curious time overhead for vscales

[est hyperreal org]

Check this out if you might have insights (or concerns) about the
overhead of multiple updates to multiple vscales. :)

Eric

---- levels.c ----

/*

  This benchmark subjects 10 vscales to around a thousand
  modifications a second.  When given an argument (e.g., "./levels
  foo") it adjusts all 10 vscales to new values a hundred times a
  second.  When not given an argument ("./levels") it adjusts one of
  the vscales a hundred times every tenth of a second.  My
  understanding of GTK will be much improved when I understand why the
  first case seems to use dramatically less cpu than the second (as
  revealed by time and top).  It almost seems it should be the other
  way around. :)

*/


#include <gtk/gtk.h>

#define N 10

GtkObject *as[N];

int val = 0, idx = 0;

int
foo(void *v)
{
  int i;

  for (i = 0; i < N; i++)
    {
      gtk_adjustment_set_value(GTK_ADJUSTMENT(as[i]), val/100.0);
      val = (val + 1) % 101;
    }

  return 1;
}

int
bar(void *v)
{
  int i;

  for (i = 0; i < 101; i++)
    {
      gtk_adjustment_set_value(GTK_ADJUSTMENT(as[idx]), i/100.0);
      idx = (idx + 1) % N;
    }

  return 1;
}

void
delcb(GtkWidget *w, gpointer data)
{
  gtk_main_quit();
}

int
main(int argc, char **argv)
{
  GtkWidget *w, *h, *s;
  int i;

  gtk_init(&argc, &argv);

  w = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  gtk_signal_connect(GTK_OBJECT(w), "delete_event", 
		     GTK_SIGNAL_FUNC(delcb), GTK_OBJECT(w));

  h = gtk_hbox_new(0, 0);

  gtk_container_add(GTK_CONTAINER(w), h);

  for (i = 0; i < N; i++)
  {
    as[i] = gtk_adjustment_new(.5, 0, 1, .01, .1, 0);
    s = gtk_vscale_new(GTK_ADJUSTMENT(as[i]));
    gtk_scale_set_digits(GTK_SCALE(s), 2);
    gtk_box_pack_start(GTK_BOX(h), s, 0, 0, 0);
  }

  gtk_widget_show_all(w);

  if (argc > 1)
    gtk_timeout_add(10, foo, 0);
  else
    gtk_timeout_add(100, bar, 0);

  gtk_main();

  return 0;
}