198 lines
4.6 KiB
C
198 lines
4.6 KiB
C
/* $Id$ */
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/*
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* Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com)
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* Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef __PJ_MATH_H__
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#define __PJ_MATH_H__
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/**
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* @file math.h
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* @brief Mathematics and Statistics.
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*/
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#include <pj/string.h>
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#include <pj/compat/high_precision.h>
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PJ_BEGIN_DECL
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/**
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* @defgroup pj_math Mathematics and Statistics
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* @ingroup PJ_MISC
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* @{
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*
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* Provides common mathematics constants and operations, and also standard
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* statistics calculation (min, max, mean, standard deviation). Statistics
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* calculation is done in realtime (statistics state is updated on time each
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* new sample comes).
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*/
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/**
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* Mathematical constants
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*/
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#define PJ_PI 3.14159265358979323846 /* pi */
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#define PJ_1_PI 0.318309886183790671538 /* 1/pi */
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/**
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* Mathematical macro
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*/
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#define PJ_ABS(x) ((x) > 0 ? (x) : -(x))
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#define PJ_MAX(x, y) ((x) > (y)? (x) : (y))
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#define PJ_MIN(x, y) ((x) < (y)? (x) : (y))
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/**
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* This structure describes statistics state.
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*/
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typedef struct pj_math_stat
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{
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int n; /* number of samples */
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int max; /* maximum value */
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int min; /* minimum value */
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int last; /* last value */
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int mean; /* mean */
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/* Private members */
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#if PJ_HAS_FLOATING_POINT
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float fmean_; /* mean(floating point) */
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#else
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int mean_res_; /* mean residu */
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#endif
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pj_highprec_t m2_; /* variance * n */
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} pj_math_stat;
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/**
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* Calculate integer square root of an integer.
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*
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* @param i Integer to be calculated.
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*
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* @return Square root result.
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*/
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PJ_INLINE(unsigned) pj_isqrt(unsigned i)
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{
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unsigned res = 1, prev;
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/* Rough guess, calculate half bit of input */
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prev = i >> 2;
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while (prev) {
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prev >>= 2;
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res <<= 1;
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}
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/* Babilonian method */
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do {
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prev = res;
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res = (prev + i/prev) >> 1;
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} while ((prev+res)>>1 != res);
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return res;
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}
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/**
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* Initialize statistics state.
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*
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* @param stat Statistic state.
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*/
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PJ_INLINE(void) pj_math_stat_init(pj_math_stat *stat)
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{
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pj_bzero(stat, sizeof(pj_math_stat));
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}
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/**
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* Update statistics state as a new sample comes.
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*
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* @param stat Statistic state.
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* @param val The new sample data.
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*/
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PJ_INLINE(void) pj_math_stat_update(pj_math_stat *stat, int val)
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{
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#if PJ_HAS_FLOATING_POINT
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float delta;
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#else
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int delta;
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#endif
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stat->last = val;
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if (stat->n++) {
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if (stat->min > val)
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stat->min = val;
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if (stat->max < val)
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stat->max = val;
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} else {
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stat->min = stat->max = val;
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}
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#if PJ_HAS_FLOATING_POINT
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delta = val - stat->fmean_;
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stat->fmean_ += delta/stat->n;
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/* Return mean value with 'rounding' */
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stat->mean = (int) (stat->fmean_ + 0.5);
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stat->m2_ += (int)(delta * (val-stat->fmean_));
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#else
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delta = val - stat->mean;
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stat->mean += delta/stat->n;
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stat->mean_res_ += delta % stat->n;
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if (stat->mean_res_ >= stat->n) {
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++stat->mean;
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stat->mean_res_ -= stat->n;
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} else if (stat->mean_res_ <= -stat->n) {
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--stat->mean;
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stat->mean_res_ += stat->n;
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}
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stat->m2_ += delta * (val-stat->mean);
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#endif
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}
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/**
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* Get the standard deviation of specified statistics state.
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*
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* @param stat Statistic state.
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*
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* @return The standard deviation.
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*/
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PJ_INLINE(unsigned) pj_math_stat_get_stddev(const pj_math_stat *stat)
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{
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if (stat->n == 0) return 0;
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return (pj_isqrt((unsigned)(stat->m2_/stat->n)));
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}
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/**
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* Set the standard deviation of statistics state. This is useful when
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* the statistic state is operated in 'read-only' mode as a storage of
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* statistical data.
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*
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* @param stat Statistic state.
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*
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* @param dev The standard deviation.
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*/
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PJ_INLINE(void) pj_math_stat_set_stddev(pj_math_stat *stat, unsigned dev)
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{
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if (stat->n == 0)
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stat->n = 1;
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stat->m2_ = dev*dev*stat->n;
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}
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/** @} */
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PJ_END_DECL
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#endif /* __PJ_MATH_H__ */
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