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 $\text{"L"}$.

n

Type: System..::..Int32

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

Constraint: $\mathbf{n}\ge 1$.

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 $\mathbf{n}$.

On entry: the 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.

ap

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

An array of size [$\mathbf{n}\times \left(\mathbf{n}+1\right)/2$]

On exit: the $n$ by $n$ triangular matrix $A$, packed by columns.

More precisely,

• if $\mathbf{uplo}=\text{"U"}$, the upper triangle of $A$ is stored with element $A_{ij}$ in $\mathbf{ap}\left[i+j\left(j-1\right)/2\right]$ for $i\le j$;
• if $\mathbf{uplo}=\text{"L"}$, the lower triangle of $A$ is stored with element $A_{ij}$ in $\mathbf{ap}\left[i+\left(2n-j\right)\left(j-1\right)/2\right]$ for $i\ge j$.

info

Type: System..::..Int32%

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