--- rpl/lapack/lapack/dsytrs2.f 2011/07/22 07:38:12 1.3 +++ rpl/lapack/lapack/dsytrs2.f 2023/08/07 08:39:11 1.15 @@ -1,12 +1,138 @@ - SUBROUTINE DSYTRS2( UPLO, N, NRHS, A, LDA, IPIV, B, LDB, +*> \brief \b DSYTRS2 +* +* =========== DOCUMENTATION =========== +* +* Online html documentation available at +* http://www.netlib.org/lapack/explore-html/ +* +*> \htmlonly +*> Download DSYTRS2 + dependencies +*> +*> [TGZ] +*> +*> [ZIP] +*> +*> [TXT] +*> \endhtmlonly +* +* Definition: +* =========== +* +* SUBROUTINE DSYTRS2( UPLO, N, NRHS, A, LDA, IPIV, B, LDB, +* WORK, INFO ) +* +* .. Scalar Arguments .. +* CHARACTER UPLO +* INTEGER INFO, LDA, LDB, N, NRHS +* .. +* .. Array Arguments .. +* INTEGER IPIV( * ) +* DOUBLE PRECISION A( LDA, * ), B( LDB, * ), WORK( * ) +* .. +* +* +*> \par Purpose: +* ============= +*> +*> \verbatim +*> +*> DSYTRS2 solves a system of linear equations A*X = B with a real +*> symmetric matrix A using the factorization A = U*D*U**T or +*> A = L*D*L**T computed by DSYTRF and converted by DSYCONV. +*> \endverbatim +* +* Arguments: +* ========== +* +*> \param[in] UPLO +*> \verbatim +*> UPLO is CHARACTER*1 +*> Specifies whether the details of the factorization are stored +*> as an upper or lower triangular matrix. +*> = 'U': Upper triangular, form is A = U*D*U**T; +*> = 'L': Lower triangular, form is A = L*D*L**T. +*> \endverbatim +*> +*> \param[in] N +*> \verbatim +*> N is INTEGER +*> The order of the matrix A. N >= 0. +*> \endverbatim +*> +*> \param[in] NRHS +*> \verbatim +*> NRHS is INTEGER +*> The number of right hand sides, i.e., the number of columns +*> of the matrix B. NRHS >= 0. +*> \endverbatim +*> +*> \param[in,out] A +*> \verbatim +*> A is DOUBLE PRECISION array, dimension (LDA,N) +*> The block diagonal matrix D and the multipliers used to +*> obtain the factor U or L as computed by DSYTRF. +*> Note that A is input / output. This might be counter-intuitive, +*> and one may think that A is input only. A is input / output. This +*> is because, at the start of the subroutine, we permute A in a +*> "better" form and then we permute A back to its original form at +*> the end. +*> \endverbatim +*> +*> \param[in] LDA +*> \verbatim +*> LDA is INTEGER +*> The leading dimension of the array A. LDA >= max(1,N). +*> \endverbatim +*> +*> \param[in] IPIV +*> \verbatim +*> IPIV is INTEGER array, dimension (N) +*> Details of the interchanges and the block structure of D +*> as determined by DSYTRF. +*> \endverbatim +*> +*> \param[in,out] B +*> \verbatim +*> B is DOUBLE PRECISION array, dimension (LDB,NRHS) +*> On entry, the right hand side matrix B. +*> On exit, the solution matrix X. +*> \endverbatim +*> +*> \param[in] LDB +*> \verbatim +*> LDB is INTEGER +*> The leading dimension of the array B. LDB >= max(1,N). +*> \endverbatim +*> +*> \param[out] WORK +*> \verbatim +*> WORK is DOUBLE PRECISION array, dimension (N) +*> \endverbatim +*> +*> \param[out] INFO +*> \verbatim +*> INFO is INTEGER +*> = 0: successful exit +*> < 0: if INFO = -i, the i-th argument had an illegal value +*> \endverbatim +* +* Authors: +* ======== +* +*> \author Univ. of Tennessee +*> \author Univ. of California Berkeley +*> \author Univ. of Colorado Denver +*> \author NAG Ltd. +* +*> \ingroup doubleSYcomputational +* +* ===================================================================== + SUBROUTINE DSYTRS2( UPLO, N, NRHS, A, LDA, IPIV, B, LDB, $ WORK, INFO ) * -* -- LAPACK PROTOTYPE routine (version 3.3.1) -- +* -- LAPACK computational routine -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- -* -- April 2011 -- -* -* -- Written by Julie Langou of the Univ. of TN -- * * .. Scalar Arguments .. CHARACTER UPLO @@ -17,53 +143,6 @@ DOUBLE PRECISION A( LDA, * ), B( LDB, * ), WORK( * ) * .. * -* Purpose -* ======= -* -* DSYTRS2 solves a system of linear equations A*X = B with a real -* symmetric matrix A using the factorization A = U*D*U**T or -* A = L*D*L**T computed by DSYTRF and converted by DSYCONV. -* -* Arguments -* ========= -* -* UPLO (input) CHARACTER*1 -* Specifies whether the details of the factorization are stored -* as an upper or lower triangular matrix. -* = 'U': Upper triangular, form is A = U*D*U**T; -* = 'L': Lower triangular, form is A = L*D*L**T. -* -* N (input) INTEGER -* The order of the matrix A. N >= 0. -* -* NRHS (input) INTEGER -* The number of right hand sides, i.e., the number of columns -* of the matrix B. NRHS >= 0. -* -* A (input) DOUBLE PRECISION array, dimension (LDA,N) -* The block diagonal matrix D and the multipliers used to -* obtain the factor U or L as computed by DSYTRF. -* -* LDA (input) INTEGER -* The leading dimension of the array A. LDA >= max(1,N). -* -* IPIV (input) INTEGER array, dimension (N) -* Details of the interchanges and the block structure of D -* as determined by DSYTRF. -* -* B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) -* On entry, the right hand side matrix B. -* On exit, the solution matrix X. -* -* LDB (input) INTEGER -* The leading dimension of the array B. LDB >= max(1,N). -* -* WORK (workspace) REAL array, dimension (N) -* -* INFO (output) INTEGER -* = 0: successful exit -* < 0: if INFO = -i, the i-th argument had an illegal value -* * ===================================================================== * * .. Parameters .. @@ -118,7 +197,7 @@ * * Solve A*X = B, where A = U*D*U**T. * -* P**T * B +* P**T * B K=N DO WHILE ( K .GE. 1 ) IF( IPIV( K ).GT.0 ) THEN @@ -143,7 +222,7 @@ CALL DTRSM('L','U','N','U',N,NRHS,ONE,A,LDA,B,LDB) * * Compute D \ B -> B [ D \ (U \P**T * B) ] -* +* I=N DO WHILE ( I .GE. 1 ) IF( IPIV(I) .GT. 0 ) THEN @@ -195,7 +274,7 @@ * * Solve A*X = B, where A = L*D*L**T. * -* P**T * B +* P**T * B K=1 DO WHILE ( K .LE. N ) IF( IPIV( K ).GT.0 ) THEN @@ -220,7 +299,7 @@ CALL DTRSM('L','L','N','U',N,NRHS,ONE,A,LDA,B,LDB) * * Compute D \ B -> B [ D \ (L \P**T * B) ] -* +* I=1 DO WHILE ( I .LE. N ) IF( IPIV(I) .GT. 0 ) THEN @@ -242,7 +321,7 @@ END DO * * Compute (L**T \ B) -> B [ L**T \ (D \ (L \P**T * B) ) ] -* +* CALL DTRSM('L','L','T','U',N,NRHS,ONE,A,LDA,B,LDB) * * P * B [ P * (L**T \ (D \ (L \P**T * B) )) ]