 DTRTTP(3) copies a triangular matrix A from full format (TR) to standard packed format (TP)

## SYNOPSIS

SUBROUTINE DTRTTP(
UPLO, N, A, LDA, AP, INFO )

CHARACTER UPLO

INTEGER INFO, N, LDA

DOUBLE PRECISION A( LDA, * ), AP( * )

## PURPOSE

DTRTTP copies a triangular matrix A from full format (TR) to standard packed format (TP).

## ARGUMENTS

UPLO (input) CHARACTER
= 'U': A is upper triangular.
= 'L': A is lower triangular.
N (input) INTEGER
The order of the matrices AP and A. N >= 0.
A (input) DOUBLE PRECISION array, dimension (LDA,N)
On exit, the triangular matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
AP (output) DOUBLE PRECISION array, dimension (N*(N+1)/2
On exit, the upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value