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strsyl.f(3) | LAPACK | strsyl.f(3) |
NAME¶
strsyl.f -SYNOPSIS¶
Functions/Subroutines¶
subroutine strsyl (TRANA, TRANB, ISGN, M, N, A, LDA, B, LDB, C, LDC, SCALE, INFO)
Function/Subroutine Documentation¶
subroutine strsyl (characterTRANA, characterTRANB, integerISGN, integerM, integerN, real, dimension( lda, * )A, integerLDA, real, dimension( ldb, * )B, integerLDB, real, dimension( ldc, * )C, integerLDC, realSCALE, integerINFO)¶
STRSYL Purpose:STRSYL 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.
TRANA
Author:
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*CM
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.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).
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Definition at line 164 of file strsyl.f.
Author¶
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