forked from M-Labs/nalgebra
a52b079578
The previous implementation of try_inverse() used an approximate check of the determinant against 0 for small matrices to determine if the matrix was invertible. This is not a reliable test, and may fail for perfectly invertible matrices. This change simply makes the test criterion an exact comparison instead.
122 lines
4.6 KiB
Rust
122 lines
4.6 KiB
Rust
#[macro_use]
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extern crate approx;
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extern crate nalgebra as na;
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use na::{Matrix1, Matrix2, Matrix3, Matrix5};
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#[test]
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fn matrix1_try_inverse() {
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let a = Matrix1::new(3.0);
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, Matrix1::new(1.0 / 3.0));
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}
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#[test]
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fn matrix2_try_inverse() {
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let a = Matrix2::new( 5.0, -2.0,
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-10.0, 1.0);
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let expected_inverse = Matrix2::new(-0.2 / 3.0, -2.0 / 15.0,
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-2.0 / 3.0, -1.0 / 3.0);
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let a_inv = a.try_inverse()
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.expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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#[test]
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fn matrix3_try_inverse() {
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let a = Matrix3::new(-3.0, 2.0, 0.0,
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-6.0, 9.0, -2.0,
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9.0, -6.0, 4.0);
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let expected_inverse = Matrix3::new(-0.40, 0.4 / 3.0, 0.2 / 3.00,
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-0.10, 0.2, 0.10,
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0.75, 0.0, 0.25);
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let a_inv = a.try_inverse()
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.expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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#[test]
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fn matrix5_try_inverse() {
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// Dimension 5 is chosen so that the inversion
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// happens by Gaussian elimination
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// (at the time of writing dimensions <= 3 are implemented
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// as analytic formulas, but we choose 5 in the case that 4
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// also gets an analytic implementation)
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let a = Matrix5::new(-2.0, 0.0, 2.0, 5.0, -5.0,
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-6.0, 4.0, 4.0, 13.0, -15.0,
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4.0, 16.0, -14.0, -19.0, 12.0,
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12.0, 12.0, -22.0, -35.0, 34.0,
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-8.0, 4.0, 12.0, 27.0, -31.0);
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let expected_inverse = Matrix5::new(
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3.9333e+00, -1.5667e+00, 2.6667e-01, 6.6667e-02, 3.0000e-01,
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-1.2033e+01, 3.9667e+00, -1.1167e+00, 2.8333e-01, -1.0000e-01,
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-1.8233e+01, 5.7667e+00, -1.5667e+00, 2.3333e-01, -2.0000e-01,
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-4.3333e+00, 1.6667e+00, -6.6667e-01, 3.3333e-01, -4.6950e-19,
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-1.3400e+01, 4.6000e+00, -1.4000e+00, 4.0000e-01, -2.0000e-01);
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse, max_relative=1e-4);
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}
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#[test]
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fn matrix1_try_inverse_scaled_identity() {
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// A perfectly invertible matrix with
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// very small coefficients
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let a = Matrix1::new(1.0e-20);
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let expected_inverse = Matrix1::new(1.0e20);
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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#[test]
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fn matrix2_try_inverse_scaled_identity() {
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// A perfectly invertible matrix with
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// very small coefficients
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let a = Matrix2::new(1.0e-20, 0.0,
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0.0, 1.0e-20);
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let expected_inverse = Matrix2::new(1.0e20, 0.0,
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0.0, 1.0e20);
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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#[test]
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fn matrix3_try_inverse_scaled_identity() {
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// A perfectly invertible matrix with
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// very small coefficients
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let a = Matrix3::new(1.0e-20, 0.0, 0.0,
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0.0, 1.0e-20, 0.0,
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0.0, 0.0, 1.0e-20);
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let expected_inverse = Matrix3::new(1.0e20, 0.0, 0.0,
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0.0, 1.0e20, 0.0,
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0.0, 0.0, 1.0e20);
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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#[test]
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fn matrix5_try_inverse_scaled_identity() {
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// A perfectly invertible matrix with
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// very small coefficients
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let a = Matrix5::new(1.0e-20, 0.0, 0.0, 0.0, 0.0,
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0.0, 1.0e-20, 0.0, 0.0, 0.0,
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0.0, 0.0, 1.0e-20, 0.0, 0.0,
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0.0, 0.0, 0.0, 1.0e-20, 0.0,
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0.0, 0.0, 0.0, 0.0, 1.0e-20);
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let expected_inverse = Matrix5::new(1.0e+20, 0.0, 0.0, 0.0, 0.0,
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0.0, 1.0e+20, 0.0, 0.0, 0.0,
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0.0, 0.0, 1.0e+20, 0.0, 0.0,
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0.0, 0.0, 0.0, 1.0e+20, 0.0,
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0.0, 0.0, 0.0, 0.0, 1.0e+20);;
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let a_inv = a.try_inverse().expect("Matrix is invertible");
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assert_relative_eq!(a_inv, expected_inverse);
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}
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