115 lines
3.2 KiB
FortranFixed
115 lines
3.2 KiB
FortranFixed
SUBROUTINE CTRTTP( UPLO, N, A, LDA, AP, INFO )
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*
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* -- LAPACK routine (version 3.2) --
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* -- Contributed by Fred Gustavson of the IBM Watson Research Center --
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* -- and Julien Langou of the Univ. of Colorado Denver --
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* -- November 2008 --
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*
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER INFO, N, LDA
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* ..
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* .. Array Arguments ..
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COMPLEX A( LDA, * ), AP( * )
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* ..
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*
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* Purpose
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* =======
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*
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* CTRTTP copies a triangular matrix A from full format (TR) to standard
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* packed format (TP).
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*
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* Arguments
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* =========
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*
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* UPLO (input) CHARACTER
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* = 'U': A is upper triangular;
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* = 'L': A is lower triangular.
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*
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* N (input) INTEGER
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* The order of the matrices AP and A. N >= 0.
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*
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* A (input) COMPLEX array, dimension (LDA,N)
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* On entry, the triangular matrix A. If UPLO = 'U', the leading
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* N-by-N upper triangular part of A contains the upper
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* triangular part of the matrix A, and the strictly lower
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* triangular part of A is not referenced. If UPLO = 'L', the
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* leading N-by-N lower triangular part of A contains the lower
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* triangular part of the matrix A, and the strictly upper
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* triangular part of A is not referenced.
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*
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* LDA (input) INTEGER
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* The leading dimension of the array A. LDA >= max(1,N).
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*
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* AP (output) COMPLEX array, dimension ( N*(N+1)/2 ),
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* On exit, the upper or lower triangular matrix A, packed
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* columnwise in a linear array. The j-th column of A is stored
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* in the array AP as follows:
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* if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
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* if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
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*
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* INFO (output) INTEGER
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* = 0: successful exit
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* < 0: if INFO = -i, the i-th argument had an illegal value
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*
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* =====================================================================
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*
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* .. Parameters ..
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* ..
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* .. Local Scalars ..
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LOGICAL LOWER
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INTEGER I, J, K
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* ..
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* .. External Subroutines ..
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EXTERNAL XERBLA
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* ..
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* .. Executable Statements ..
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*
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* Test the input parameters.
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*
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INFO = 0
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LOWER = LSAME( UPLO, 'L' )
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IF( .NOT.LOWER .AND. .NOT.LSAME( UPLO, 'U' ) ) THEN
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INFO = -1
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ELSE IF( N.LT.0 ) THEN
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INFO = -2
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ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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INFO = -4
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END IF
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'CTRTTP', -INFO )
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RETURN
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END IF
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*
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IF( LOWER ) THEN
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K = 0
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DO J = 1, N
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DO I = J, N
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K = K + 1
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AP( K ) = A( I, J )
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END DO
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END DO
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ELSE
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K = 0
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DO J = 1, N
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DO I = 1, J
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K = K + 1
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AP( K ) = A( I, J )
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END DO
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END DO
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END IF
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*
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*
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RETURN
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*
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* End of CTRTTP
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*
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END
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