version 1.3, 2018/05/29 06:55:21
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version 1.6, 2023/08/07 08:39:11
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*> \verbatim |
*> \verbatim |
*> |
*> |
*> DSYTRS_AA solves a system of linear equations A*X = B with a real |
*> DSYTRS_AA solves a system of linear equations A*X = B with a real |
*> symmetric matrix A using the factorization A = U*T*U**T or |
*> symmetric matrix A using the factorization A = U**T*T*U or |
*> A = L*T*L**T computed by DSYTRF_AA. |
*> A = L*T*L**T computed by DSYTRF_AA. |
*> \endverbatim |
*> \endverbatim |
* |
* |
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*> UPLO is CHARACTER*1 |
*> UPLO is CHARACTER*1 |
*> Specifies whether the details of the factorization are stored |
*> Specifies whether the details of the factorization are stored |
*> as an upper or lower triangular matrix. |
*> as an upper or lower triangular matrix. |
*> = 'U': Upper triangular, form is A = U*T*U**T; |
*> = 'U': Upper triangular, form is A = U**T*T*U; |
*> = 'L': Lower triangular, form is A = L*T*L**T. |
*> = 'L': Lower triangular, form is A = L*T*L**T. |
*> \endverbatim |
*> \endverbatim |
*> |
*> |
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*> The leading dimension of the array B. LDB >= max(1,N). |
*> The leading dimension of the array B. LDB >= max(1,N). |
*> \endverbatim |
*> \endverbatim |
*> |
*> |
*> \param[in] WORK |
*> \param[out] WORK |
*> \verbatim |
*> \verbatim |
*> WORK is DOUBLE array, dimension (MAX(1,LWORK)) |
*> WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)) |
*> \endverbatim |
*> \endverbatim |
*> |
*> |
*> \param[in] LWORK |
*> \param[in] LWORK |
*> \verbatim |
*> \verbatim |
*> LWORK is INTEGER, LWORK >= MAX(1,3*N-2). |
*> LWORK is INTEGER |
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*> The dimension of the array WORK. LWORK >= max(1,3*N-2). |
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*> \endverbatim |
*> |
*> |
*> \param[out] INFO |
*> \param[out] INFO |
*> \verbatim |
*> \verbatim |
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*> \author Univ. of Colorado Denver |
*> \author Univ. of Colorado Denver |
*> \author NAG Ltd. |
*> \author NAG Ltd. |
* |
* |
*> \date November 2017 |
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* |
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*> \ingroup doubleSYcomputational |
*> \ingroup doubleSYcomputational |
* |
* |
* ===================================================================== |
* ===================================================================== |
SUBROUTINE DSYTRS_AA( UPLO, N, NRHS, A, LDA, IPIV, B, LDB, |
SUBROUTINE DSYTRS_AA( UPLO, N, NRHS, A, LDA, IPIV, B, LDB, |
$ WORK, LWORK, INFO ) |
$ WORK, LWORK, INFO ) |
* |
* |
* -- LAPACK computational routine (version 3.8.0) -- |
* -- LAPACK computational routine -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* November 2017 |
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* |
* |
IMPLICIT NONE |
IMPLICIT NONE |
* |
* |
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* |
* |
IF( UPPER ) THEN |
IF( UPPER ) THEN |
* |
* |
* Solve A*X = B, where A = U*T*U**T. |
* Solve A*X = B, where A = U**T*T*U. |
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* |
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* 1) Forward substitution with U**T |
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* |
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IF( N.GT.1 ) THEN |
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* |
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* Pivot, P**T * B -> B |
* |
* |
* Pivot, P**T * B |
DO K = 1, N |
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KP = IPIV( K ) |
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IF( KP.NE.K ) |
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$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
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END DO |
* |
* |
DO K = 1, N |
* Compute U**T \ B -> B [ (U**T \P**T * B) ] |
KP = IPIV( K ) |
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IF( KP.NE.K ) |
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$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
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END DO |
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* |
* |
* Compute (U \P**T * B) -> B [ (U \P**T * B) ] |
CALL DTRSM('L', 'U', 'T', 'U', N-1, NRHS, ONE, A( 1, 2 ), |
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$ LDA, B( 2, 1 ), LDB) |
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END IF |
* |
* |
CALL DTRSM('L', 'U', 'T', 'U', N-1, NRHS, ONE, A( 1, 2 ), LDA, |
* 2) Solve with triangular matrix T |
$ B( 2, 1 ), LDB) |
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* |
* |
* Compute T \ B -> B [ T \ (U \P**T * B) ] |
* Compute T \ B -> B [ T \ (U**T \P**T * B) ] |
* |
* |
CALL DLACPY( 'F', 1, N, A( 1, 1 ), LDA+1, WORK( N ), 1) |
CALL DLACPY( 'F', 1, N, A( 1, 1 ), LDA+1, WORK( N ), 1) |
IF( N.GT.1 ) THEN |
IF( N.GT.1 ) THEN |
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CALL DGTSV( N, NRHS, WORK( 1 ), WORK( N ), WORK( 2*N ), B, LDB, |
CALL DGTSV( N, NRHS, WORK( 1 ), WORK( N ), WORK( 2*N ), B, LDB, |
$ INFO ) |
$ INFO ) |
* |
* |
* Compute (U**T \ B) -> B [ U**T \ (T \ (U \P**T * B) ) ] |
* 3) Backward substitution with U |
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* |
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IF( N.GT.1 ) THEN |
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* |
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* Compute U \ B -> B [ U \ (T \ (U**T \P**T * B) ) ] |
* |
* |
CALL DTRSM( 'L', 'U', 'N', 'U', N-1, NRHS, ONE, A( 1, 2 ), LDA, |
CALL DTRSM( 'L', 'U', 'N', 'U', N-1, NRHS, ONE, A( 1, 2 ), |
$ B( 2, 1 ), LDB) |
$ LDA, B( 2, 1 ), LDB) |
* |
* |
* Pivot, P * B [ P * (U**T \ (T \ (U \P**T * B) )) ] |
* Pivot, P * B -> B [ P * (U \ (T \ (U**T \P**T * B) )) ] |
* |
* |
DO K = N, 1, -1 |
DO K = N, 1, -1 |
KP = IPIV( K ) |
KP = IPIV( K ) |
IF( KP.NE.K ) |
IF( KP.NE.K ) |
$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
END DO |
END DO |
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END IF |
* |
* |
ELSE |
ELSE |
* |
* |
* Solve A*X = B, where A = L*T*L**T. |
* Solve A*X = B, where A = L*T*L**T. |
* |
* |
* Pivot, P**T * B |
* 1) Forward substitution with L |
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* |
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IF( N.GT.1 ) THEN |
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* |
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* Pivot, P**T * B -> B |
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* |
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DO K = 1, N |
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KP = IPIV( K ) |
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IF( KP.NE.K ) |
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$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
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END DO |
* |
* |
DO K = 1, N |
* Compute L \ B -> B [ (L \P**T * B) ] |
KP = IPIV( K ) |
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IF( KP.NE.K ) |
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$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
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END DO |
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* |
* |
* Compute (L \P**T * B) -> B [ (L \P**T * B) ] |
CALL DTRSM( 'L', 'L', 'N', 'U', N-1, NRHS, ONE, A( 2, 1 ), |
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$ LDA, B( 2, 1 ), LDB) |
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END IF |
* |
* |
CALL DTRSM( 'L', 'L', 'N', 'U', N-1, NRHS, ONE, A( 2, 1 ), LDA, |
* 2) Solve with triangular matrix T |
$ B( 2, 1 ), LDB) |
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* |
* |
* Compute T \ B -> B [ T \ (L \P**T * B) ] |
* Compute T \ B -> B [ T \ (L \P**T * B) ] |
* |
* |
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CALL DGTSV( N, NRHS, WORK( 1 ), WORK(N), WORK( 2*N ), B, LDB, |
CALL DGTSV( N, NRHS, WORK( 1 ), WORK(N), WORK( 2*N ), B, LDB, |
$ INFO) |
$ INFO) |
* |
* |
* Compute (L**T \ B) -> B [ L**T \ (T \ (L \P**T * B) ) ] |
* 3) Backward substitution with L**T |
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* |
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IF( N.GT.1 ) THEN |
* |
* |
CALL DTRSM( 'L', 'L', 'T', 'U', N-1, NRHS, ONE, A( 2, 1 ), LDA, |
* Compute (L**T \ B) -> B [ L**T \ (T \ (L \P**T * B) ) ] |
$ B( 2, 1 ), LDB) |
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* |
* |
* Pivot, P * B [ P * (L**T \ (T \ (L \P**T * B) )) ] |
CALL DTRSM( 'L', 'L', 'T', 'U', N-1, NRHS, ONE, A( 2, 1 ), |
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$ LDA, B( 2, 1 ), LDB) |
* |
* |
DO K = N, 1, -1 |
* Pivot, P * B -> B [ P * (L**T \ (T \ (L \P**T * B) )) ] |
KP = IPIV( K ) |
* |
IF( KP.NE.K ) |
DO K = N, 1, -1 |
$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
KP = IPIV( K ) |
END DO |
IF( KP.NE.K ) |
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$ CALL DSWAP( NRHS, B( K, 1 ), LDB, B( KP, 1 ), LDB ) |
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END DO |
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END IF |
* |
* |
END IF |
END IF |
* |
* |