Arguments

A

(input/output) REAL or COMPLEX square array, shape $(:,:)$.
On entry, the matrix $A$.
If ${\bf UPLO}$ = 'U', the upper triangular part of A contains the upper triangular part of the matrix $A$, and the strictly lower triangular part of ${\bf A}$ is not referenced.
If ${\bf UPLO}$ = 'L', the lower triangular part of ${\bf A}$ contains the lower triangular part of the matrix $A$, and the strictly upper triangular part of ${\bf A}$ is not referenced.
On exit, the block diagonal matrix $D$ and the multipliers used to obtain the factor $U$ or $L$ from the factorization of $A$.

B

(input/output) REAL or COMPLEX array, shape $(:,:)$ with $size({\bf B},1) = size({\bf A},1)$ or shape $(:)$ with $size({\bf B})=size({\bf A},1)$.
On entry, the matrix $B$.
On exit, the solution matrix $X$.

UPLO

Optional (input) CHARACTER(LEN=1)


Default value: 'U'.

IPIV

Optional (output) INTEGER array, shape $(:)$ with $size({\bf IPIV})=size({\bf A},1)$.
Details of the row and column interchanges and the block structure of $D$.
If ${\bf IPIV}_k > 0$, then rows and columns $k$ and ${\bf IPIV}_k$ were interchanged, and $D_{k,k}$ is a $1 \times 1$ diagonal block.
If ${\bf IPIV}_k < 0$, then there are two cases:

INFO

Optional (output) INTEGER


If INFO is not present and an error occurs, then the program is terminated with an error message.

References: [1] and [17,9,20,21].