added new pseudo driver to log data generated by a prng with the random walk method

misc/controller/vzlogger/src/protocols/ltqnorm.c

@@ -0,0 +1,93 @@
+/**
+ * Lower tail quantile for standard normal distribution function.
+ *
+ * This function returns an approximation of the inverse cumulative
+ * standard normal distribution function.  I.e., given P, it returns
+ * an approximation to the X satisfying P = Pr{Z <= X} where Z is a
+ * random variable from the standard normal distribution.
+ *
+ * The algorithm uses a minimax approximation by rational functions
+ * and the result has a relative error whose absolute value is less
+ * than 1.15e-9.
+ *
+ * C implementation adapted from Peter's Perl version
+ *
+ * @author Peter John Acklam <jacklam@math.uio.no>
+ * @link http://www.math.uio.no/~jacklam
+ */
+
+#include <math.h>
+#include <errno.h>
+
+/* Coefficients in rational approximations. */
+static const double a[] = {
+	-3.969683028665376e+01,
+	 2.209460984245205e+02,
+	-2.759285104469687e+02,
+	 1.383577518672690e+02,
+	-3.066479806614716e+01,
+	 2.506628277459239e+00
+};
+
+static const double b[] = {
+	-5.447609879822406e+01,
+	 1.615858368580409e+02,
+	-1.556989798598866e+02,
+	 6.680131188771972e+01,
+	-1.328068155288572e+01
+};
+
+static const double c[] = {
+	-7.784894002430293e-03,
+	-3.223964580411365e-01,
+	-2.400758277161838e+00,
+	-2.549732539343734e+00,
+	 4.374664141464968e+00,
+	 2.938163982698783e+00
+};
+
+static const double d[] =
+{
+	7.784695709041462e-03,
+	3.224671290700398e-01,
+	2.445134137142996e+00,
+	3.754408661907416e+00
+};
+
+#define LOW 0.02425
+#define HIGH 0.97575
+
+double ltqnorm(double p) {
+	double q, r;
+
+	errno = 0;
+
+	if (p < 0 || p > 1) {
+		errno = EDOM;
+		return 0.0;
+	}
+	else if (p == 0) {
+		errno = ERANGE;
+		return -HUGE_VAL /* minus "infinity" */;
+	}
+	else if (p == 1) {
+		errno = ERANGE;
+		return HUGE_VAL /* "infinity" */;
+	}
+	else if (p < LOW) { /* Rational approximation for lower region */
+		q = sqrt(-2*log(p));
+		return (((((c[0]*q+c[1])*q+c[2])*q+c[3])*q+c[4])*q+c[5]) /
+			((((d[0]*q+d[1])*q+d[2])*q+d[3])*q+1);
+	}
+	else if (p > HIGH) { /* Rational approximation for upper region */
+		q  = sqrt(-2*log(1-p));
+		return -(((((c[0]*q+c[1])*q+c[2])*q+c[3])*q+c[4])*q+c[5]) /
+			((((d[0]*q+d[1])*q+d[2])*q+d[3])*q+1);
+	}
+	else { /* Rational approximation for central region */
+    		q = p - 0.5;
+    		r = q*q;
+		return (((((a[0]*r+a[1])*r+a[2])*r+a[3])*r+a[4])*r+a[5])*q /
+			(((((b[0]*r+b[1])*r+b[2])*r+b[3])*r+b[4])*r+1);
+	}
+}

misc/controller/vzlogger/src/protocols/random.c

@@ -0,0 +1,73 @@
+/**
+ * Generate pseudo random data series with a random walk
+ *
+ * @package vzlogger
+ * @copyright Copyright (c) 2011, The volkszaehler.org project
+ * @license http://www.gnu.org/licenses/gpl.txt GNU Public License
+ * @author Steffen Vogel <info@steffenvogel.de>
+ */
+/*
+ * This file is part of volkzaehler.org
+ *
+ * volkzaehler.org 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 of the License, or
+ * any later version.
+ *
+ * volkzaehler.org 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 volkszaehler.org. If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "../main.h"
+#include "../protocol.h"
+#include "random.h"
+
+/**
+ * Initialize prng
+ * @return random_state_t
+ */
+void * random_init(char *options) {
+	random_state_t *state;
+	state = malloc(sizeof(random_state_t));
+
+	srand(time(NULL));
+	
+	state->min = 0; // TODO parse from options
+	state->max = strtof(options, NULL);
+	state->last = state->max * ((float) rand() / RAND_MAX); /* start value */
+	
+	return (void *) state;
+}
+
+void random_close(void *handle) {
+	free(handle);
+}
+
+reading_t random_get(void *handle) {
+	random_state_t *state = (random_state_t *) handle;
+	reading_t rd;
+	
+	state->last += ltqnorm((float) rand() / RAND_MAX);
+	
+	/* check bounaries */
+	if (state->last > state->max) {
+		state->last = state->max;
+	}
+	else if (state->last < state->min) {
+		state->last = state->min;
+	}
+	
+	rd.value = state->last;
+	gettimeofday(&rd.tv, NULL);
+	
+	return rd;
+}

misc/controller/vzlogger/src/protocols/random.h

@@ -0,0 +1,41 @@
+/**
+ * Generate pseudo random data series with a random walk
+ *
+ * @package vzlogger
+ * @copyright Copyright (c) 2011, The volkszaehler.org project
+ * @license http://www.gnu.org/licenses/gpl.txt GNU Public License
+ * @author Steffen Vogel <info@steffenvogel.de>
+ */
+/*
+ * This file is part of volkzaehler.org
+ *
+ * volkzaehler.org 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 of the License, or
+ * any later version.
+ *
+ * volkzaehler.org 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 volkszaehler.org. If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+#ifndef _RANDOM_H_
+#define _RANDOM_H_
+
+#include "../protocol.h"
+
+typedef struct {
+	float min, max, last;
+} random_state_t;
+
+double ltqnorm(double p);
+
+void * random_init(char *port);
+void random_close(void *handle);
+reading_t random_get(void *handle);
+
+#endif /* _RANDOM_H_ */