table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/strsyl3.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/strsyl3.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/strsyl3.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine STRSYL3 (trana, tranb, isgn, m, n, a, lda, b,
ldb, c, ldc, scale, iwork, liwork, swork, ldswork, info)
STRSYL3
Function/Subroutine Documentation¶
subroutine STRSYL3 (character trana, character tranb, integer isgn, integer m, integer n, real, dimension( lda, * ) a, integer lda, real, dimension( ldb, * ) b, integer ldb, real, dimension( ldc, * ) c, integer ldc, real scale, integer, dimension( * ) iwork, integer liwork, real, dimension( ldswork, * ) swork, integer ldswork, integer info)¶
STRSYL3
Purpose
!> !> STRSYL3 solves the real Sylvester matrix equation: !> !> op(A)*X + X*op(B) = scale*C or !> op(A)*X - X*op(B) = scale*C, !> !> where op(A) = A or A**T, and A and B are both upper quasi- !> triangular. A is M-by-M and B is N-by-N; the right hand side C and !> the solution X are M-by-N; and scale is an output scale factor, set !> <= 1 to avoid overflow in X. !> !> A and B must be in Schur canonical form (as returned by SHSEQR), that !> is, block upper triangular with 1-by-1 and 2-by-2 diagonal blocks; !> each 2-by-2 diagonal block has its diagonal elements equal and its !> off-diagonal elements of opposite sign. !> !> This is the block version of the algorithm. !>
Parameters
TRANA
!> TRANA is CHARACTER*1 !> Specifies the option op(A): !> = 'N': op(A) = A (No transpose) !> = 'T': op(A) = A**T (Transpose) !> = 'C': op(A) = A**H (Conjugate transpose = Transpose) !>
TRANB
!> TRANB is CHARACTER*1 !> Specifies the option op(B): !> = 'N': op(B) = B (No transpose) !> = 'T': op(B) = B**T (Transpose) !> = 'C': op(B) = B**H (Conjugate transpose = Transpose) !>
ISGN
!> ISGN is INTEGER !> Specifies the sign in the equation: !> = +1: solve op(A)*X + X*op(B) = scale*C !> = -1: solve op(A)*X - X*op(B) = scale*C !>
M
!> M is INTEGER !> The order of the matrix A, and the number of rows in the !> matrices X and C. M >= 0. !>
N
!> N is INTEGER !> The order of the matrix B, and the number of columns in the !> matrices X and C. N >= 0. !>
A
!> A is REAL array, dimension (LDA,M) !> The upper quasi-triangular matrix A, in Schur canonical form. !>
LDA
!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,M). !>
B
!> B is REAL array, dimension (LDB,N) !> The upper quasi-triangular matrix B, in Schur canonical form. !>
LDB
!> LDB is INTEGER !> The leading dimension of the array B. LDB >= max(1,N). !>
C
!> C is REAL array, dimension (LDC,N) !> On entry, the M-by-N right hand side matrix C. !> On exit, C is overwritten by the solution matrix X. !>
LDC
!> LDC is INTEGER !> The leading dimension of the array C. LDC >= max(1,M) !>
SCALE
!> SCALE is REAL !> The scale factor, scale, set <= 1 to avoid overflow in X. !>
IWORK
!> IWORK is INTEGER array, dimension (MAX(1,LIWORK)) !> On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK. !>
LIWORK
!> IWORK is INTEGER !> The dimension of the array IWORK. LIWORK >= ((M + NB - 1) / NB + 1) !> + ((N + NB - 1) / NB + 1), where NB is the optimal block size. !> !> If LIWORK = -1, then a workspace query is assumed; the routine !> only calculates the optimal dimension of the IWORK array, !> returns this value as the first entry of the IWORK array, and !> no error message related to LIWORK is issued by XERBLA. !>
SWORK
!> SWORK is REAL array, dimension (MAX(2, ROWS), !> MAX(1,COLS)). !> On exit, if INFO = 0, SWORK(1) returns the optimal value ROWS !> and SWORK(2) returns the optimal COLS. !>
LDSWORK
!> LDSWORK is INTEGER !> LDSWORK >= MAX(2,ROWS), where ROWS = ((M + NB - 1) / NB + 1) !> and NB is the optimal block size. !> !> If LDSWORK = -1, then a workspace query is assumed; the routine !> only calculates the optimal dimensions of the SWORK matrix, !> returns these values as the first and second entry of the SWORK !> matrix, and no error message related LWORK is issued by XERBLA. !>
INFO
!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value !> = 1: A and B have common or very close eigenvalues; perturbed !> values were used to solve the equation (but the matrices !> A and B are unchanged). !>
Definition at line 178 of file strsyl3.f.
Author¶
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