nyx_space/propagators/error_ctrl.rs
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/*
Nyx, blazing fast astrodynamics
Copyright (C) 2018-onwards Christopher Rabotin <christopher.rabotin@gmail.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
use serde::{Deserialize, Serialize};
use crate::linalg::allocator::Allocator;
use crate::linalg::{DefaultAllocator, DimName, OVector, U3};
// This determines when to take into consideration the magnitude of the state_delta and
// prevents dividing by too small of a number.
const REL_ERR_THRESH: f64 = 0.1;
/// The Error Control manages how a propagator computes the error in the current step.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum ErrorControl {
/// An RSS state error control which effectively for the provided vector composed of two vectors of the same unit, both of size 3 (e.g. position + velocity).
RSSCartesianState,
/// An RSS step error control which effectively for the provided vector composed of two vectors of the same unit, both of size 3 (e.g. position + velocity).
RSSCartesianStep,
/// An RSS state error control: when in doubt, use this error controller, especially for high accurracy.
///
/// Here is the warning from GMAT R2016a on this error controller:
/// > This is a more stringent error control method than [`rss_step`] that is often used as the default in other software such as STK.
/// > If you set [the] accuracy to a very small number, 1e-13 for example, and set the error control to [`rss_step`], integrator
/// > performance will be poor, for little if any improvement in the accuracy of the orbit integration.
/// > For more best practices of these integrators (which clone those in GMAT), please refer to the
/// > [GMAT reference](https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/doc/help/src/Resource_NumericalIntegrators.xml#L1292).
/// > (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3004]
RSSState,
/// An RSS step error control which effectively computes the L2 norm of the provided Vector of size 3
///
/// Note that this error controller should be preferably be used only with slices of a state with the same units.
/// For example, one should probably use this for position independently of using it for the velocity.
/// (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3045]
RSSStep,
/// A largest error control which effectively computes the largest error at each component
///
/// This is a standard error computation algorithm, but it's arguably bad if the state's components have different units.
/// It calculates the largest local estimate of the error from the integration (`error_est`)
/// given the difference in the candidate state and the previous state (`state_delta`).
/// This error estimator is from the physical model estimator of GMAT
/// (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/PhysicalModel.cpp#L987]
LargestError,
/// A largest state error control
///
/// (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3018]
LargestState,
/// A largest step error control which effectively computes the L1 norm of the provided Vector of size 3
///
/// Note that this error controller should be preferably be used only with slices of a state with the same units.
/// For example, one should probably use this for position independently of using it for the velocity.
/// (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3033]
LargestStep,
}
impl ErrorControl {
/// Computes the actual error of the current step.
///
/// The `error_est` is the estimated error computed from the difference in the two stages of
/// of the RK propagator. The `candidate` variable is the candidate state, and `cur_state` is
/// the current state. This function must return the error.
pub fn estimate<N: DimName>(
self,
error_est: &OVector<f64, N>,
candidate: &OVector<f64, N>,
cur_state: &OVector<f64, N>,
) -> f64
where
DefaultAllocator: Allocator<N>,
{
match self {
ErrorControl::RSSCartesianState => {
if N::dim() >= 6 {
let err_radius = RSSState::estimate::<U3>(
&error_est.fixed_rows::<3>(0).into_owned(),
&candidate.fixed_rows::<3>(0).into_owned(),
&cur_state.fixed_rows::<3>(0).into_owned(),
);
let err_velocity = RSSState::estimate::<U3>(
&error_est.fixed_rows::<3>(3).into_owned(),
&candidate.fixed_rows::<3>(3).into_owned(),
&cur_state.fixed_rows::<3>(3).into_owned(),
);
err_radius.max(err_velocity)
} else {
RSSStep::estimate(error_est, candidate, cur_state)
}
}
ErrorControl::RSSCartesianStep => {
if N::dim() >= 6 {
let err_radius = RSSStep::estimate::<U3>(
&error_est.fixed_rows::<3>(0).into_owned(),
&candidate.fixed_rows::<3>(0).into_owned(),
&cur_state.fixed_rows::<3>(0).into_owned(),
);
let err_velocity = RSSStep::estimate::<U3>(
&error_est.fixed_rows::<3>(3).into_owned(),
&candidate.fixed_rows::<3>(3).into_owned(),
&cur_state.fixed_rows::<3>(3).into_owned(),
);
err_radius.max(err_velocity)
} else {
RSSStep::estimate(error_est, candidate, cur_state)
}
}
ErrorControl::RSSState => {
let mag = 0.5 * (candidate + cur_state).norm();
let err = error_est.norm();
if mag > REL_ERR_THRESH {
err / mag
} else {
err
}
}
ErrorControl::RSSStep => {
let mag = (candidate - cur_state).norm();
let err = error_est.norm();
if mag > REL_ERR_THRESH.sqrt() {
err / mag
} else {
err
}
}
ErrorControl::LargestError => {
let state_delta = candidate - cur_state;
let mut max_err = 0.0;
for (i, prop_err_i) in error_est.iter().enumerate() {
let err = if state_delta[i] > REL_ERR_THRESH {
(prop_err_i / state_delta[i]).abs()
} else {
prop_err_i.abs()
};
if err > max_err {
max_err = err;
}
}
max_err
}
ErrorControl::LargestState => {
let sum_state = candidate + cur_state;
let mut mag = 0.0f64;
let mut err = 0.0f64;
for i in 0..N::dim() {
mag += 0.5 * sum_state[i].abs();
err += error_est[i].abs();
}
if mag > REL_ERR_THRESH {
err / mag
} else {
err
}
}
ErrorControl::LargestStep => {
let state_delta = candidate - cur_state;
let mut mag = 0.0f64;
let mut err = 0.0f64;
for i in 0..N::dim() {
mag += state_delta[i].abs();
err += error_est[i].abs();
}
if mag > REL_ERR_THRESH {
err / mag
} else {
err
}
}
}
}
}
impl Default for ErrorControl {
fn default() -> Self {
Self::RSSCartesianStep
}
}
/// An RSS step error control which effectively computes the L2 norm of the provided Vector of size 3
///
/// Note that this error controller should be preferably be used only with slices of a state with the same units.
/// For example, one should probably use this for position independently of using it for the velocity.
/// (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3045]
#[derive(Clone, Copy)]
#[allow(clippy::upper_case_acronyms)]
struct RSSStep;
impl RSSStep {
fn estimate<N: DimName>(
error_est: &OVector<f64, N>,
candidate: &OVector<f64, N>,
cur_state: &OVector<f64, N>,
) -> f64
where
DefaultAllocator: Allocator<N>,
{
let mag = (candidate - cur_state).norm();
let err = error_est.norm();
if mag > REL_ERR_THRESH.sqrt() {
err / mag
} else {
err
}
}
}
/// An RSS state error control: when in doubt, use this error controller, especially for high accurracy.
///
/// Here is the warning from GMAT R2016a on this error controller:
/// > This is a more stringent error control method than [`rss_step`] that is often used as the default in other software such as STK.
/// > If you set [the] accuracy to a very small number, 1e-13 for example, and set the error control to [`rss_step`], integrator
/// > performance will be poor, for little if any improvement in the accuracy of the orbit integration.
/// > For more best practices of these integrators (which clone those in GMAT), please refer to the
/// > [GMAT reference](https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/doc/help/src/Resource_NumericalIntegrators.xml#L1292).
/// > (Source)[https://github.com/ChristopherRabotin/GMAT/blob/37201a6290e7f7b941bc98ee973a527a5857104b/src/base/forcemodel/ODEModel.cpp#L3004]
#[derive(Clone, Copy)]
#[allow(clippy::upper_case_acronyms)]
struct RSSState;
impl RSSState {
fn estimate<N: DimName>(
error_est: &OVector<f64, N>,
candidate: &OVector<f64, N>,
cur_state: &OVector<f64, N>,
) -> f64
where
DefaultAllocator: Allocator<N>,
{
let mag = 0.5 * (candidate + cur_state).norm();
let err = error_est.norm();
if mag > REL_ERR_THRESH {
err / mag
} else {
err
}
}
}