Parameters

uplo

Type: System..::..String

On entry: specifies whether $A$ is upper or lower triangular.

$\mathbf{uplo}=\text{"U"}$

$A$ is upper triangular.

$\mathbf{uplo}=\text{"L"}$

$A$ is lower triangular.

Constraint: $\mathbf{uplo}=\text{"U"}$ or $\text{"L"}$.

diag

Type: System..::..String

On entry: indicates whether $A$ is a nonunit or unit triangular matrix.

$\mathbf{diag}=\text{"N"}$

$A$ is a nonunit triangular matrix.

$\mathbf{diag}=\text{"U"}$

$A$ is a unit triangular matrix; the diagonal elements are not referenced and are assumed to be $1$.

Constraint: $\mathbf{diag}=\text{"N"}$ or $\text{"U"}$.

n

Type: System..::..Int32

On entry: $n$, the order of the matrix $A$.

Constraint: $\mathbf{n}\ge 0$.

a

Type: array<System..::..Double,2>[,](,)[,][,]

An array of size [dim1, dim2]

Note: dim1 must satisfy the constraint: $\mathrm{dim1}\ge \max \left(1,\mathbf{n}\right)$

Note: the second dimension of the array a must be at least $\max \left(1,\mathbf{n}\right)$.

On entry: the $n$ by $n$ triangular matrix $A$.

• If $\mathbf{uplo}=\text{"U"}$, $A$ is upper triangular and the elements of the array below the diagonal are not referenced.
• If $\mathbf{uplo}=\text{"L"}$, $A$ is lower triangular and the elements of the array above the diagonal are not referenced.
• If $\mathbf{diag}=\text{"U"}$, the diagonal elements of $A$ are assumed to be $1$, and are not referenced.

On exit: $A$ is overwritten by $A^{-1}$, using the same storage format as described above.

info

Type: System..::..Int32%

On exit: $\mathbf{info}=0$ unless the method detects an error (see [Error Indicators and Warnings]).