SUBROUTINE DTRTTP( UPLO, N, A, LDA, AP, INFO ) * * -- LAPACK routine (version 3.2) -- * -- Contributed by Fred Gustavson of the IBM Watson Research Center -- * -- and Julien Langou of the Univ. of Colorado Denver -- * -- November 2008 -- * * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. Scalar Arguments .. CHARACTER UPLO INTEGER INFO, N, LDA * .. * .. Array Arguments .. 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 * * ===================================================================== * * .. Parameters .. * .. * .. Local Scalars .. LOGICAL LOWER INTEGER I, J, K * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. * .. External Subroutines .. EXTERNAL XERBLA * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 LOWER = LSAME( UPLO, 'L' ) IF( .NOT.LOWER .AND. .NOT.LSAME( UPLO, 'U' ) ) THEN INFO = -1 ELSE IF( N.LT.0 ) THEN INFO = -2 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN INFO = -4 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'DTRTTP', -INFO ) RETURN END IF * IF( LOWER ) THEN K = 0 DO J = 1, N DO I = J, N K = K + 1 AP( K ) = A( I, J ) END DO END DO ELSE K = 0 DO J = 1, N DO I = 1, J K = K + 1 AP( K ) = A( I, J ) END DO END DO END IF * * RETURN * * End of DTRTTP * END