forked from M-Labs/nalgebra
61 lines
2.0 KiB
Rust
61 lines
2.0 KiB
Rust
use alga::general::Real;
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use core::{DefaultAllocator, SquareMatrix};
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use core::dimension::DimMin;
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use core::storage::Storage;
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use core::allocator::Allocator;
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use linalg::LU;
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impl<N: Real, D: DimMin<D, Output = D>, S: Storage<N, D, D>> SquareMatrix<N, D, S> {
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/// Computes the matrix determinant.
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///
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/// If the matrix has a dimension larger than 3, an LU decomposition is used.
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#[inline]
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pub fn determinant(&self) -> N
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where
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DefaultAllocator: Allocator<N, D, D> + Allocator<(usize, usize), D>,
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{
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assert!(
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self.is_square(),
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"Unable to compute the determinant of a non-square matrix."
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);
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let dim = self.shape().0;
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unsafe {
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match dim {
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0 => N::one(),
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1 => *self.get_unchecked(0, 0),
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2 => {
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let m11 = *self.get_unchecked(0, 0);
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let m12 = *self.get_unchecked(0, 1);
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let m21 = *self.get_unchecked(1, 0);
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let m22 = *self.get_unchecked(1, 1);
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m11 * m22 - m21 * m12
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}
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3 => {
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let m11 = *self.get_unchecked(0, 0);
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let m12 = *self.get_unchecked(0, 1);
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let m13 = *self.get_unchecked(0, 2);
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let m21 = *self.get_unchecked(1, 0);
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let m22 = *self.get_unchecked(1, 1);
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let m23 = *self.get_unchecked(1, 2);
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let m31 = *self.get_unchecked(2, 0);
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let m32 = *self.get_unchecked(2, 1);
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let m33 = *self.get_unchecked(2, 2);
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let minor_m12_m23 = m22 * m33 - m32 * m23;
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let minor_m11_m23 = m21 * m33 - m31 * m23;
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let minor_m11_m22 = m21 * m32 - m31 * m22;
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m11 * minor_m12_m23 - m12 * minor_m11_m23 + m13 * minor_m11_m22
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}
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_ => LU::new(self.clone_owned()).determinant(),
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}
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}
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}
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}
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