Match against exponential weighted average of last samples, thus new values are more valuable as old ones. Two thresholds - rising and falling - produce hysteresis loop like in RMON alert subsystem. If the average reaches the "rising" threshold, matcher go to the "match" state and hold It until the average drops under the "falling" threshold.
Call the matcher with the following sequence:
type = matcher pattern = ExpLoss(hist => <hist>, rising=><rising> \ [,falling => <falling>] [,skip=><stat>] [,fast=><fast>])
hist - number of samples to weight against; weight will be disposed with
exponential decreasing manner from newest to oldest, so that the
oldest sample would have 1% significance;
rising - rising threshold for packet loss, 0-100%
falling - falling threshold for packet loss, default is <rising>
skip - skip <skip> number of samples after startup before "fire" alerts.
fast - use <fast> samples for fast transition: if the values of last <fast>
samples more then <rising> - take "match" state, if less then
<falling> - take "no match" state.
If the actual history is less then <hist> value then this value is taken
as the actual history.
Copyright (c) 2008 Veniamin Konoplev
Developed in cooperation with EU EGEE project
This program 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 2 of the License, or (at your option) any later version.
This program 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 this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Veniamin Konoplev <email@example.com>