On the LU factorization

Specific Domains Numerics
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1

What is wrong with my code ? It works well six years ago.
It is the case of a singular matrix.
I review the following exercise: Compute the LU factorization of the matrix
A=[1 2 -1 3 2;2 4 -2 5 1;-1 -2 1 -3 -4;3 6 2 10 7; 1 2 4 0 4].
The used code is:

using LinearAlgebra
A=[1 2 -1 3 2;2 4 -2 5 1;-1 -2 1 -3 -4;3 6 2 10 7; 1 2 4 0 4].
(L,U,p)=lu(A)
Error message: Error: SingularException

and
(L,U,p)=lu(A,check=false)
Error message: Failed factorization of type LU(Float64, Matrix(Float64))

When the matrix is not singular then the lu factorizarion works
without problem.

2

To force it to proceed for a singular A, you can use (L,U,p)=lu(A, check=false). Note that the U factor has a zero entry on the diagonal in this case, due to the fact that your matrix A is singular.