trsyl3(3) LAPACK trsyl3(3)

trsyl3 - trsyl3: Sylvester equation, level 3


subroutine ctrsyl3 (trana, tranb, isgn, m, n, a, lda, b, ldb, c, ldc, scale, swork, ldswork, info)
CTRSYL3 subroutine ztrsyl3 (trana, tranb, isgn, m, n, a, lda, b, ldb, c, ldc, scale, swork, ldswork, info)
ZTRSYL3

CTRSYL3

Purpose


CTRSYL3 solves the complex 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**H, and A and B are both upper 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.
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)
= 'C': op(A) = A**H (Conjugate transpose)

TRANB


TRANB is CHARACTER*1
Specifies the option op(B):
= 'N': op(B) = B (No transpose)
= 'C': op(B) = B**H (Conjugate 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 COMPLEX array, dimension (LDA,M)
The upper triangular matrix A.

LDA


LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,M).

B


B is COMPLEX array, dimension (LDB,N)
The upper triangular matrix B.

LDB


LDB is INTEGER
The leading dimension of the array B. LDB >= max(1,N).

C


C is COMPLEX 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.

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).

ZTRSYL3

Purpose


ZTRSYL3 solves the complex 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**H, and A and B are both upper 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.
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)
= 'C': op(A) = A**H (Conjugate transpose)

TRANB


TRANB is CHARACTER*1
Specifies the option op(B):
= 'N': op(B) = B (No transpose)
= 'C': op(B) = B**H (Conjugate 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 COMPLEX*16 array, dimension (LDA,M)
The upper triangular matrix A.

LDA


LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,M).

B


B is COMPLEX*16 array, dimension (LDB,N)
The upper triangular matrix B.

LDB


LDB is INTEGER
The leading dimension of the array B. LDB >= max(1,N).

C


C is COMPLEX*16 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 DOUBLE PRECISION
The scale factor, scale, set <= 1 to avoid overflow in X.

SWORK


SWORK is DOUBLE PRECISION 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).

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Fri Aug 9 2024 02:33:22 Version 3.12.0