53 lines
1.4 KiB
Rust
53 lines
1.4 KiB
Rust
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//! This module provides the matrix exponential (pow) function to square matrices.
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use std::ops::DivAssign;
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use crate::{allocator::Allocator, DefaultAllocator, DimMin, DimMinimum, MatrixN};
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use num::PrimInt;
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use simba::scalar::ComplexField;
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impl<N: ComplexField, D> MatrixN<N, D>
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where
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D: DimMin<D, Output = D>,
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DefaultAllocator: Allocator<N, D, D>
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+ Allocator<(usize, usize), DimMinimum<D, D>>
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+ Allocator<N, D>
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+ Allocator<N::RealField, D>
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+ Allocator<N::RealField, D, D>,
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{
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/// Raises a matrix to an integer power using exponentiation by squares.
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/// Returns `None` only when the matrix is non-invertible and raised to a
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/// negative power.
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pub fn pow<T: PrimInt + DivAssign>(&self, mut e: T) -> Option<Self> {
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let zero = T::zero();
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if e == zero {
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let mut i = self.clone();
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i.fill_with_identity();
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return Some(i);
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}
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let mut acc;
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if e < zero {
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acc = self.clone().try_inverse()?;
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} else {
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acc = self.clone();
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}
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let one = T::one();
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let two = T::from(2u8).unwrap();
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let mut multiplier = acc.clone();
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while e != zero {
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if e % two == one {
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acc *= &multiplier;
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}
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e /= two;
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multiplier *= multiplier.clone();
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}
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Some(acc)
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}
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}
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