- SD calc

diff --git a/src/testbed/standard_deviation.c b/src/testbed/standard_deviation.c
new file mode 100644 (file)
index 0000000..362b50b
--- /dev/null
+++ b/src/testbed/standard_deviation.c
@@ -0,0 +1,123 @@
+/*
+      This file is part of GNUnet
+      (C) 2008--2012 Christian Grothoff (and other contributing authors)
+
+      GNUnet is free software; you can redistribute it and/or modify
+      it under the terms of the GNU General Public License as published
+      by the Free Software Foundation; either version 3, or (at your
+      option) any later version.
+
+      GNUnet is distributed in the hope that it will be useful, but
+      WITHOUT ANY WARRANTY; without even the implied warranty of
+      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+      General Public License for more details.
+
+      You should have received a copy of the GNU General Public License
+      along with GNUnet; see the file COPYING.  If not, write to the
+      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+      Boston, MA 02111-1307, USA.
+ */
+
+#include <gnunet/platform.h>
+#include <gnunet/gnunet_common.h>
+
+struct SDHandle
+{
+  /**
+   * Squared sum of data values
+   */
+  unsigned long long sqsum;
+
+  /**
+   * Sum of the data values
+   */
+  unsigned long sum;
+
+  /**
+   * The average of data amounts
+   */
+  unsigned int avg;
+
+  /**
+   * The variance
+   */
+  unsigned int vr;
+
+  /**
+   * Number of data values
+   */
+  unsigned int cnt;
+};
+
+
+struct SDHandle *
+GNUNET_TESTBED_SD_init ()
+{
+  return GNUNET_malloc (sizeof (struct SDHandle));
+}
+
+void
+GNUNET_TESTBED_SD_destroy (struct SDHandle *h)
+{
+  GNUNET_free (h);
+}
+
+void
+GNUNET_TESTBED_SD_add_data (struct SDHandle *h, unsigned int amount)
+{
+  unsigned long sqavg;
+
+  h->sum += amount;
+  h->cnt++;
+  h->sqsum += ((unsigned long) amount) * ((unsigned long) amount);
+  h->avg = h->sum / h->cnt;
+  sqavg = h->avg * h->avg;
+  h->vr = (h->sqsum / h->cnt) - sqavg;
+}
+
+
+/**
+ * Returns the factor by which the given amount differs from the standard deviation
+ *
+ * @param h the SDhandle
+ * @param amount the value for which the deviation is returned
+ * @return the deviation from the average; GNUNET_SYSERR if the deviation cannot
+ *           be calculated
+ */
+int
+GNUNET_TESTBED_SD_deviation_factor (struct SDHandle *h, unsigned int amount)
+{
+  unsigned long diff;
+  unsigned int n;
+
+  if (h->cnt < 2)
+    return GNUNET_SYSERR;
+  if (amount > h->avg)
+    diff = amount - h->avg;
+  else
+    diff = h->avg - amount;
+  diff *= diff;
+  for (n = 1; n < 4; n++)
+    if (diff < (n * n * h->vr))
+      break;
+  return n;
+}
+
+
+int
+main ()
+{
+  struct SDHandle * h = GNUNET_TESTBED_SD_init ();
+  
+  GNUNET_TESTBED_SD_add_data (h, 40);
+  GNUNET_TESTBED_SD_add_data (h, 30);
+  GNUNET_TESTBED_SD_add_data (h, 40);
+  GNUNET_TESTBED_SD_add_data (h, 10);
+  GNUNET_TESTBED_SD_add_data (h, 30);
+  printf ("Average: %d\n", h->avg);
+  printf ("Variance: %d\n", h->vr);
+  printf ("Standard Deviation: %d\n", (int) sqrt (h->vr));
+  printf ("Deviation factor: %d\n", GNUNET_TESTBED_SD_deviation (h, 40));
+  GNUNET_TESTBED_SD_destroy (h);
+  return 0;
+}