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/**
* Copyright (c) 2014, Timothy Stack
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or otherlist materials provided with the distribution.
* * Neither the name of Timothy Stack nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* @file log_accel.hh
*/
#ifndef log_accel_h
#define log_accel_h
#include <cmath>
#include <stdint.h>
#include "base/lnav_log.hh"
/**
* Helper class for figuring out changes in the log message rate.
*/
class log_accel {
public:
/*< The direction of the message rate: steady, accelerating, or decelerating
*/
enum direction_t {
A_STEADY,
A_DECEL,
A_ACCEL,
};
/**
* Add a time point that will be used to compute velocity and then
* acceleration. Points should be added in reverse order, from most
* recent to oldest.
*
* @param point The point in time.
* @return True if more points can be added.
*/
bool add_point(int64_t point);
/**
* Get the average acceleration based on the time points we've received.
*
* @return The average message acceleration.
*/
double get_avg_accel() const;
/**
* Compute the message rate direction. If the average acceleration is less
* than a certain threshold, then we consider the rate to be steady.
* Otherwise, the message rate is increasing or decreasing.
*
* @return The direction of the message rate.
*/
direction_t get_direction() const;
private:
/**
* The amount of historical data to include in the average acceleration
* computation.
*/
static const int HISTORY_SIZE = 8;
/**
* The minimum range of velocities seen. This value should limit false-
* positives for small millisecond level fluctuations.
*/
static const double MIN_RANGE;
static const double THRESHOLD;
int64_t la_last_point{0};
bool la_last_point_set{false};
int64_t la_min_velocity{INT64_MAX};
int64_t la_max_velocity{INT64_MIN};
int64_t la_velocity[HISTORY_SIZE];
int la_velocity_size{0};
};
#endif
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