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168 lines
5.3 KiB
C++
168 lines
5.3 KiB
C++
/**
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* Copyright (c) 2014, Timothy Stack
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* * Neither the name of Timothy Stack nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* @file log_accel.hh
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*/
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#ifndef __log_accel_h
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#define __log_accel_h
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#include <math.h>
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#include <stdint.h>
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#include <algorithm>
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#include "lnav_log.hh"
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/**
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* Helper class for figuring out changes in the log message rate.
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*/
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class log_accel {
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public:
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/*< The direction of the message rate: steady, accelerating, or decelerating */
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enum direction_t {
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A_STEADY,
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A_DECEL,
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A_ACCEL,
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};
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log_accel()
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: la_last_point_set(false),
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la_min_velocity(INT64_MAX),
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la_max_velocity(INT64_MIN),
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la_velocity_size(0) {
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};
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/**
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* Add a time point that will be used to compute velocity and then
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* acceleration. Points should be added in reverse order, from most
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* recent to oldest.
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*
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* @param point The point in time.
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* @return True if more points can be added.
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*/
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bool add_point(int64_t point) {
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require(this->la_velocity_size < HISTORY_SIZE);
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if (this->la_last_point_set) {
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// TODO Reenable this when we find the bug that causes some older
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// timestamps to show up after more recent ones.
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// require(this->la_last_point >= point);
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// Compute the message velocity.
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this->la_velocity[this->la_velocity_size] = (
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this->la_last_point - point);
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// Find the range of velocities so we can normalize.
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this->la_min_velocity = std::min(this->la_min_velocity,
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this->la_velocity[this->la_velocity_size]);
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this->la_max_velocity = std::max(this->la_max_velocity,
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this->la_velocity[this->la_velocity_size]);
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this->la_velocity_size += 1;
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}
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this->la_last_point = point;
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this->la_last_point_set = true;
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return this->la_velocity_size < HISTORY_SIZE;
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};
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/**
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* Get the average acceleration based on the time points we've received.
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*
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* @return The average message acceleration.
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*/
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double get_avg_accel() const {
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double avg_accel = 0, total_accel = 0;
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// Compute the range of values so we can normalize.
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double range = (double) (this->la_max_velocity - this->la_min_velocity);
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range = std::max(range, MIN_RANGE);
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for (int lpc = 0; lpc < (this->la_velocity_size - 1); lpc++) {
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double accel =
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(this->la_velocity[lpc] - this->la_velocity[lpc + 1]) / range;
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total_accel += accel;
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}
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if (this->la_velocity_size > 1) {
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avg_accel = total_accel / (double) (this->la_velocity_size - 1);
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}
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return avg_accel;
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};
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/**
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* Compute the message rate direction. If the average acceleration is less
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* than a certain threshold, then we consider the rate to be steady.
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* Otherwise, the message rate is increasing or decreasing.
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*
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* @return The direction of the message rate.
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*/
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direction_t get_direction() const {
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double avg_accel = this->get_avg_accel();
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direction_t retval;
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if (::fabs(avg_accel) <= THRESHOLD) {
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retval = A_STEADY;
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}
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else if (avg_accel < 0.0) {
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retval = A_ACCEL;
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}
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else {
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retval = A_DECEL;
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}
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return retval;
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};
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private:
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/**
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* The amount of historical data to include in the average acceleration
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* computation.
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*/
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static const int HISTORY_SIZE = 8;
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/**
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* The minimum range of velocities seen. This value should limit false-
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* positives for small millisecond level fluctuations.
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*/
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static const double MIN_RANGE;
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static const double THRESHOLD;
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int64_t la_last_point;
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bool la_last_point_set;
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int64_t la_min_velocity;
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int64_t la_max_velocity;
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int64_t la_velocity[HISTORY_SIZE];
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int la_velocity_size;
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};
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#endif
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