nalgebra/src/base/norm.rs

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#[cfg(all(feature = "alloc", not(feature = "std")))]
use alloc::vec::Vec;
use num::Zero;
use std::ops::Neg;
use crate::allocator::Allocator;
use crate::base::{DefaultAllocator, Dim, DimName, Matrix, Normed, OMatrix, OVector};
use crate::constraint::{SameNumberOfColumns, SameNumberOfRows, ShapeConstraint};
use crate::storage::{Storage, StorageMut};
use crate::{ComplexField, Scalar, SimdComplexField, Unit};
use simba::scalar::ClosedNeg;
use simba::simd::{SimdOption, SimdPartialOrd, SimdValue};
// TODO: this should be be a trait on alga?
/// A trait for abstract matrix norms.
///
/// This may be moved to the alga crate in the future.
pub trait Norm<T: SimdComplexField> {
/// Apply this norm to the given matrix.
fn norm<R, C, S>(&self, m: &Matrix<T, R, C, S>) -> T::SimdRealField
where
R: Dim,
C: Dim,
S: Storage<T, R, C>;
/// Use the metric induced by this norm to compute the metric distance between the two given matrices.
fn metric_distance<R1, C1, S1, R2, C2, S2>(
&self,
m1: &Matrix<T, R1, C1, S1>,
m2: &Matrix<T, R2, C2, S2>,
) -> T::SimdRealField
where
R1: Dim,
C1: Dim,
S1: Storage<T, R1, C1>,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R1, R2> + SameNumberOfColumns<C1, C2>;
}
/// Euclidean norm.
#[derive(Copy, Clone, Debug)]
pub struct EuclideanNorm;
/// Lp norm.
#[derive(Copy, Clone, Debug)]
pub struct LpNorm(pub i32);
/// L-infinite norm aka. Chebytchev norm aka. uniform norm aka. suppremum norm.
#[derive(Copy, Clone, Debug)]
pub struct UniformNorm;
impl<T: SimdComplexField> Norm<T> for EuclideanNorm {
#[inline]
fn norm<R, C, S>(&self, m: &Matrix<T, R, C, S>) -> T::SimdRealField
where
R: Dim,
C: Dim,
S: Storage<T, R, C>,
{
m.norm_squared().simd_sqrt()
}
#[inline]
fn metric_distance<R1, C1, S1, R2, C2, S2>(
&self,
m1: &Matrix<T, R1, C1, S1>,
m2: &Matrix<T, R2, C2, S2>,
) -> T::SimdRealField
where
R1: Dim,
C1: Dim,
S1: Storage<T, R1, C1>,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R1, R2> + SameNumberOfColumns<C1, C2>,
{
m1.zip_fold(m2, T::SimdRealField::zero(), |acc, a, b| {
let diff = a - b;
acc + diff.simd_modulus_squared()
})
.simd_sqrt()
}
}
impl<T: SimdComplexField> Norm<T> for LpNorm {
#[inline]
fn norm<R, C, S>(&self, m: &Matrix<T, R, C, S>) -> T::SimdRealField
where
R: Dim,
C: Dim,
S: Storage<T, R, C>,
{
m.fold(T::SimdRealField::zero(), |a, b| {
a + b.simd_modulus().simd_powi(self.0)
})
.simd_powf(crate::convert(1.0 / (self.0 as f64)))
}
#[inline]
fn metric_distance<R1, C1, S1, R2, C2, S2>(
&self,
m1: &Matrix<T, R1, C1, S1>,
m2: &Matrix<T, R2, C2, S2>,
) -> T::SimdRealField
where
R1: Dim,
C1: Dim,
S1: Storage<T, R1, C1>,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R1, R2> + SameNumberOfColumns<C1, C2>,
{
m1.zip_fold(m2, T::SimdRealField::zero(), |acc, a, b| {
let diff = a - b;
acc + diff.simd_modulus().simd_powi(self.0)
})
.simd_powf(crate::convert(1.0 / (self.0 as f64)))
}
}
impl<T: SimdComplexField> Norm<T> for UniformNorm {
#[inline]
fn norm<R, C, S>(&self, m: &Matrix<T, R, C, S>) -> T::SimdRealField
where
R: Dim,
C: Dim,
S: Storage<T, R, C>,
{
// NOTE: we don't use `m.amax()` here because for the complex
// numbers this will return the max norm1 instead of the modulus.
m.fold(T::SimdRealField::zero(), |acc, a| {
acc.simd_max(a.simd_modulus())
})
}
#[inline]
fn metric_distance<R1, C1, S1, R2, C2, S2>(
&self,
m1: &Matrix<T, R1, C1, S1>,
m2: &Matrix<T, R2, C2, S2>,
) -> T::SimdRealField
where
R1: Dim,
C1: Dim,
S1: Storage<T, R1, C1>,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R1, R2> + SameNumberOfColumns<C1, C2>,
{
m1.zip_fold(m2, T::SimdRealField::zero(), |acc, a, b| {
let val = (a - b).simd_modulus();
acc.simd_max(val)
})
}
}
/// # Magnitude and norms
impl<T: Scalar, R: Dim, C: Dim, S: Storage<T, R, C>> Matrix<T, R, C, S> {
/// The squared L2 norm of this vector.
#[inline]
#[must_use]
pub fn norm_squared(&self) -> T::SimdRealField
where
T: SimdComplexField,
{
let mut res = T::SimdRealField::zero();
for i in 0..self.ncols() {
let col = self.column(i);
res += col.dotc(&col).simd_real()
}
res
}
/// The L2 norm of this matrix.
///
/// Use `.apply_norm` to apply a custom norm.
#[inline]
#[must_use]
pub fn norm(&self) -> T::SimdRealField
where
T: SimdComplexField,
{
self.norm_squared().simd_sqrt()
}
/// Compute the distance between `self` and `rhs` using the metric induced by the euclidean norm.
///
/// Use `.apply_metric_distance` to apply a custom norm.
#[inline]
#[must_use]
pub fn metric_distance<R2, C2, S2>(&self, rhs: &Matrix<T, R2, C2, S2>) -> T::SimdRealField
where
T: SimdComplexField,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R, R2> + SameNumberOfColumns<C, C2>,
{
self.apply_metric_distance(rhs, &EuclideanNorm)
}
/// Uses the given `norm` to compute the norm of `self`.
///
/// # Example
///
/// ```
/// # use nalgebra::{Vector3, UniformNorm, LpNorm, EuclideanNorm};
///
/// let v = Vector3::new(1.0, 2.0, 3.0);
/// assert_eq!(v.apply_norm(&UniformNorm), 3.0);
/// assert_eq!(v.apply_norm(&LpNorm(1)), 6.0);
/// assert_eq!(v.apply_norm(&EuclideanNorm), v.norm());
/// ```
#[inline]
#[must_use]
pub fn apply_norm(&self, norm: &impl Norm<T>) -> T::SimdRealField
where
T: SimdComplexField,
{
norm.norm(self)
}
/// Uses the metric induced by the given `norm` to compute the metric distance between `self` and `rhs`.
///
/// # Example
///
/// ```
/// # use nalgebra::{Vector3, UniformNorm, LpNorm, EuclideanNorm};
///
/// let v1 = Vector3::new(1.0, 2.0, 3.0);
/// let v2 = Vector3::new(10.0, 20.0, 30.0);
///
/// assert_eq!(v1.apply_metric_distance(&v2, &UniformNorm), 27.0);
/// assert_eq!(v1.apply_metric_distance(&v2, &LpNorm(1)), 27.0 + 18.0 + 9.0);
/// assert_eq!(v1.apply_metric_distance(&v2, &EuclideanNorm), (v1 - v2).norm());
/// ```
#[inline]
#[must_use]
pub fn apply_metric_distance<R2, C2, S2>(
&self,
rhs: &Matrix<T, R2, C2, S2>,
norm: &impl Norm<T>,
) -> T::SimdRealField
where
T: SimdComplexField,
R2: Dim,
C2: Dim,
S2: Storage<T, R2, C2>,
ShapeConstraint: SameNumberOfRows<R, R2> + SameNumberOfColumns<C, C2>,
{
norm.metric_distance(self, rhs)
}
/// A synonym for the norm of this matrix.
///
/// Aka the length.
///
/// This function is simply implemented as a call to `norm()`
#[inline]
#[must_use]
pub fn magnitude(&self) -> T::SimdRealField
where
T: SimdComplexField,
{
self.norm()
}
/// A synonym for the squared norm of this matrix.
///
/// Aka the squared length.
///
/// This function is simply implemented as a call to `norm_squared()`
#[inline]
#[must_use]
pub fn magnitude_squared(&self) -> T::SimdRealField
where
T: SimdComplexField,
{
self.norm_squared()
}
/// Sets the magnitude of this vector.
#[inline]
pub fn set_magnitude(&mut self, magnitude: T::SimdRealField)
where
T: SimdComplexField,
S: StorageMut<T, R, C>,
{
let n = self.norm();
self.scale_mut(magnitude / n)
}
/// Returns a normalized version of this matrix.
#[inline]
#[must_use = "Did you mean to use normalize_mut()?"]
pub fn normalize(&self) -> OMatrix<T, R, C>
where
T: SimdComplexField,
DefaultAllocator: Allocator<T, R, C>,
{
self.unscale(self.norm())
}
/// The Lp norm of this matrix.
#[inline]
#[must_use]
pub fn lp_norm(&self, p: i32) -> T::SimdRealField
where
T: SimdComplexField,
{
self.apply_norm(&LpNorm(p))
}
/// Attempts to normalize `self`.
///
/// The components of this matrix can be SIMD types.
#[inline]
#[must_use = "Did you mean to use simd_try_normalize_mut()?"]
pub fn simd_try_normalize(&self, min_norm: T::SimdRealField) -> SimdOption<OMatrix<T, R, C>>
where
T: SimdComplexField,
T::Element: Scalar,
DefaultAllocator: Allocator<T, R, C> + Allocator<T::Element, R, C>,
{
let n = self.norm();
let le = n.clone().simd_le(min_norm);
let val = self.unscale(n);
SimdOption::new(val, le)
}
/// Sets the magnitude of this vector unless it is smaller than `min_magnitude`.
///
/// If `self.magnitude()` is smaller than `min_magnitude`, it will be left unchanged.
/// Otherwise this is equivalent to: `*self = self.normalize() * magnitude.
#[inline]
pub fn try_set_magnitude(&mut self, magnitude: T::RealField, min_magnitude: T::RealField)
where
T: ComplexField,
S: StorageMut<T, R, C>,
{
let n = self.norm();
if n > min_magnitude {
self.scale_mut(magnitude / n)
}
}
/// Returns a new vector with the same magnitude as `self` clamped between `0.0` and `max`.
#[inline]
#[must_use]
pub fn cap_magnitude(&self, max: T::RealField) -> OMatrix<T, R, C>
where
T: ComplexField,
DefaultAllocator: Allocator<T, R, C>,
{
let n = self.norm();
if n > max {
self.scale(max / n)
} else {
self.clone_owned()
}
}
/// Returns a new vector with the same magnitude as `self` clamped between `0.0` and `max`.
#[inline]
#[must_use]
pub fn simd_cap_magnitude(&self, max: T::SimdRealField) -> OMatrix<T, R, C>
where
T: SimdComplexField,
T::Element: Scalar,
DefaultAllocator: Allocator<T, R, C> + Allocator<T::Element, R, C>,
{
let n = self.norm();
let scaled = self.scale(max.clone() / n.clone());
let use_scaled = n.simd_gt(max);
scaled.select(use_scaled, self.clone_owned())
}
/// Returns a normalized version of this matrix unless its norm as smaller or equal to `eps`.
///
/// The components of this matrix cannot be SIMD types (see `simd_try_normalize`) instead.
#[inline]
#[must_use = "Did you mean to use try_normalize_mut()?"]
pub fn try_normalize(&self, min_norm: T::RealField) -> Option<OMatrix<T, R, C>>
where
T: ComplexField,
DefaultAllocator: Allocator<T, R, C>,
{
let n = self.norm();
if n <= min_norm {
None
} else {
Some(self.unscale(n))
}
}
}
/// # In-place normalization
impl<T: Scalar, R: Dim, C: Dim, S: StorageMut<T, R, C>> Matrix<T, R, C, S> {
/// Normalizes this matrix in-place and returns its norm.
///
/// The components of the matrix cannot be SIMD types (see `simd_try_normalize_mut` instead).
#[inline]
pub fn normalize_mut(&mut self) -> T::SimdRealField
where
T: SimdComplexField,
{
let n = self.norm();
self.unscale_mut(n.clone());
n
}
/// Normalizes this matrix in-place and return its norm.
///
/// The components of the matrix can be SIMD types.
#[inline]
#[must_use = "Did you mean to use simd_try_normalize_mut()?"]
pub fn simd_try_normalize_mut(
&mut self,
min_norm: T::SimdRealField,
) -> SimdOption<T::SimdRealField>
where
T: SimdComplexField,
T::Element: Scalar,
DefaultAllocator: Allocator<T, R, C> + Allocator<T::Element, R, C>,
{
let n = self.norm();
let le = n.clone().simd_le(min_norm);
self.apply(|e| *e = e.clone().simd_unscale(n.clone()).select(le, e.clone()));
SimdOption::new(n, le)
}
/// Normalizes this matrix in-place or does nothing if its norm is smaller or equal to `eps`.
///
/// If the normalization succeeded, returns the old norm of this matrix.
#[inline]
pub fn try_normalize_mut(&mut self, min_norm: T::RealField) -> Option<T::RealField>
where
T: ComplexField,
{
let n = self.norm();
if n <= min_norm {
None
} else {
self.unscale_mut(n.clone());
Some(n)
}
}
}
impl<T: SimdComplexField, R: Dim, C: Dim> Normed for OMatrix<T, R, C>
where
DefaultAllocator: Allocator<T, R, C>,
{
type Norm = T::SimdRealField;
#[inline]
fn norm(&self) -> T::SimdRealField {
self.norm()
}
#[inline]
fn norm_squared(&self) -> T::SimdRealField {
self.norm_squared()
}
#[inline]
fn scale_mut(&mut self, n: Self::Norm) {
self.scale_mut(n)
}
#[inline]
fn unscale_mut(&mut self, n: Self::Norm) {
self.unscale_mut(n)
}
}
impl<T: Scalar + ClosedNeg, R: Dim, C: Dim> Neg for Unit<OMatrix<T, R, C>>
where
DefaultAllocator: Allocator<T, R, C>,
{
type Output = Unit<OMatrix<T, R, C>>;
#[inline]
fn neg(self) -> Self::Output {
Unit::new_unchecked(-self.value)
}
}
// TODO: specialization will greatly simplify this implementation in the future.
// In particular:
// use `x()` instead of `::canonical_basis_element`
// use `::new(x, y, z)` instead of `::from_slice`
/// # Basis and orthogonalization
impl<T: ComplexField, D: DimName> OVector<T, D>
where
DefaultAllocator: Allocator<T, D>,
{
/// The i-the canonical basis element.
#[inline]
fn canonical_basis_element(i: usize) -> Self {
let mut res = Self::zero();
res[i] = T::one();
res
}
/// Orthonormalizes the given family of vectors. The largest free family of vectors is moved at
/// the beginning of the array and its size is returned. Vectors at an indices larger or equal to
/// this length can be modified to an arbitrary value.
#[inline]
pub fn orthonormalize(vs: &mut [Self]) -> usize {
let mut nbasis_elements = 0;
for i in 0..vs.len() {
{
let (elt, basis) = vs[..i + 1].split_last_mut().unwrap();
for basis_element in &basis[..nbasis_elements] {
*elt -= &*basis_element * elt.dot(basis_element)
}
}
if vs[i].try_normalize_mut(T::RealField::zero()).is_some() {
// TODO: this will be efficient on dynamically-allocated vectors but for
// statically-allocated ones, `.clone_from` would be better.
vs.swap(nbasis_elements, i);
nbasis_elements += 1;
// All the other vectors will be dependent.
if nbasis_elements == D::dim() {
break;
}
}
}
nbasis_elements
}
/// Applies the given closure to each element of the orthonormal basis of the subspace
/// orthogonal to free family of vectors `vs`. If `vs` is not a free family, the result is
/// unspecified.
// TODO: return an iterator instead when `-> impl Iterator` will be supported by Rust.
#[inline]
pub fn orthonormal_subspace_basis<F>(vs: &[Self], mut f: F)
where
F: FnMut(&Self) -> bool,
{
// TODO: is this necessary?
assert!(
vs.len() <= D::dim(),
"The given set of vectors has no chance of being a free family."
);
match D::dim() {
1 => {
if vs.is_empty() {
let _ = f(&Self::canonical_basis_element(0));
}
}
2 => {
if vs.is_empty() {
let _ = f(&Self::canonical_basis_element(0))
&& f(&Self::canonical_basis_element(1));
} else if vs.len() == 1 {
let v = &vs[0];
let res = Self::from_column_slice(&[-v[1].clone(), v[0].clone()]);
let _ = f(&res.normalize());
}
// Otherwise, nothing.
}
3 => {
if vs.is_empty() {
let _ = f(&Self::canonical_basis_element(0))
&& f(&Self::canonical_basis_element(1))
&& f(&Self::canonical_basis_element(2));
} else if vs.len() == 1 {
let v = &vs[0];
let mut a;
if v[0].clone().norm1() > v[1].clone().norm1() {
a = Self::from_column_slice(&[v[2].clone(), T::zero(), -v[0].clone()]);
} else {
a = Self::from_column_slice(&[T::zero(), -v[2].clone(), v[1].clone()]);
};
let _ = a.normalize_mut();
if f(&a.cross(v)) {
let _ = f(&a);
}
} else if vs.len() == 2 {
let _ = f(&vs[0].cross(&vs[1]).normalize());
}
}
_ => {
#[cfg(any(feature = "std", feature = "alloc"))]
{
// XXX: use a GenericArray instead.
let mut known_basis = Vec::new();
for v in vs.iter() {
known_basis.push(v.normalize())
}
for i in 0..D::dim() - vs.len() {
let mut elt = Self::canonical_basis_element(i);
for v in &known_basis {
elt -= v * elt.dot(v)
}
if let Some(subsp_elt) = elt.try_normalize(T::RealField::zero()) {
if !f(&subsp_elt) {
return;
};
known_basis.push(subsp_elt);
}
}
}
#[cfg(all(not(feature = "std"), not(feature = "alloc")))]
{
panic!("Cannot compute the orthogonal subspace basis of a vector with a dimension greater than 3 \
if #![no_std] is enabled and the 'alloc' feature is not enabled.")
}
}
}
}
}