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/* $Id: filter.c,v 1.2 2000/03/06 06:04:06 reinelt Exp $
*
* smooth and damp functions
*
* Copyright 1999, 2000 by Michael Reinelt (reinelt@eunet.at)
*
* 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, 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.
*
*
* $Log: filter.c,v $
* Revision 1.2 2000/03/06 06:04:06 reinelt
*
* minor cleanups
*
*
*/
/*
*
* exported fuctions:
*
* smooth (name, period, value)
* returns an average value over a given period
* uses global variable "tick"
*
* damp (name, value)
* damps a value with exp(-t/tau)
* uses global variable "tau"
*
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <sys/time.h>
#include "filter.h"
extern int tick;
extern int tau;
#define SLOTS 64
#define SECONDS(x) (x.tv_sec+x.tv_usec/1000000.0)
typedef struct {
char *name;
int slots;
struct timeval *time;
double *value;
} FILTER;
double smooth(char *name, int period, double value)
{
static FILTER *Filter=NULL;
static int nFilter=0;
struct timeval now;
double t, v;
int i, j;
gettimeofday (&now, NULL);
for (i=0; i<nFilter; i++) {
if (strcmp(name, Filter[i].name)==0)
break;
}
if (i==nFilter) {
int slots=(period+tick-1)/tick;
if (slots<2)
slots=2;
else if (slots>SLOTS)
slots=SLOTS;
nFilter++;
Filter=realloc(Filter, nFilter*sizeof(FILTER));
Filter[i].name=strdup(name);
Filter[i].slots=slots;
Filter[i].time=malloc(slots*sizeof(Filter[i].time[0]));
Filter[i].value=malloc(slots*sizeof(Filter[i].value[0]));
for (j=0; j<slots; j++) {
Filter[i].time[j]=now;
Filter[i].value[j]=value;
}
}
for (j=Filter[i].slots-1; j>0; j--) {
Filter[i].time[j]=Filter[i].time[j-1];
Filter[i].value[j]=Filter[i].value[j-1];
}
Filter[i].time[0]=now;
Filter[i].value[0]=value;
t = SECONDS(Filter[i].time[0]) - SECONDS(Filter[i].time[Filter[i].slots-1]);
v = Filter[i].value[0]-Filter[i].value[Filter[i].slots-1];
if (t==0.0 || v<0.0)
return 0;
else
return v/t;
}
double damp(char *name, double value)
{
static FILTER *Filter=NULL;
static int nFilter=0;
struct timeval now;
double max;
int i, j;
if (tau==0.0)
return value;
gettimeofday (&now, NULL);
for (i=0; i<nFilter; i++) {
if (strcmp(name, Filter[i].name)==0)
break;
}
if (i==nFilter) {
int slots=log(100)*tau/tick;
if (slots<1)
slots=1;
else if (slots>SLOTS)
slots=SLOTS;
nFilter++;
Filter=realloc(Filter, nFilter*sizeof(FILTER));
Filter[i].name=strdup(name);
Filter[i].slots=slots;
Filter[i].time=malloc(slots*sizeof(Filter[i].time));
Filter[i].value=malloc(slots*sizeof(Filter[i].value));
for (j=0; j<slots; j++) {
Filter[i].time[j]=now;
Filter[i].value[j]=0;
}
}
max=value;
for (j=Filter[i].slots-1; j>0; j--) {
double t = SECONDS(Filter[i].time[j]) - SECONDS(Filter[i].time[j-1]);
Filter[i].time[j]=Filter[i].time[j-1];
Filter[i].value[j]=Filter[i].value[j-1]*exp(-t/tau);
if (Filter[i].value[j]>max) max=Filter[i].value[j];
}
Filter[i].time[0]=now;
Filter[i].value[0]=value;
return max;
}
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