strsyl.f (3)  Linux Manuals
NAME
strsyl.f 
SYNOPSIS
Functions/Subroutines
subroutine strsyl (TRANA, TRANB, ISGN, M, N, A, LDA, B, LDB, C, LDC, SCALE, INFO)
STRSYL
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 MbyM and B is NbyN; the right hand side C and the solution X are MbyN; 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 1by1 and 2by2 diagonal blocks; each 2by2 diagonal block has its diagonal elements equal and its offdiagonal elements of opposite sign.
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)
TRANBTRANB 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)
ISGNISGN 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
MM is INTEGER The order of the matrix A, and the number of rows in the matrices X and C. M >= 0.
NN is INTEGER The order of the matrix B, and the number of columns in the matrices X and C. N >= 0.
AA is REAL array, dimension (LDA,M) The upper quasitriangular matrix A, in Schur canonical form.
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).
BB is REAL array, dimension (LDB,N) The upper quasitriangular matrix B, in Schur canonical form.
LDBLDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).
CC is REAL array, dimension (LDC,N) On entry, the MbyN right hand side matrix C. On exit, C is overwritten by the solution matrix X.
LDCLDC is INTEGER The leading dimension of the array C. LDC >= max(1,M)
SCALESCALE is REAL The scale factor, scale, set <= 1 to avoid overflow in X.
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith 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).
Author:

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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