.TH "SRC/ztgevc.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*- .ad l .nh .SH NAME SRC/ztgevc.f .SH SYNOPSIS .br .PP .SS "Functions/Subroutines" .in +1c .ti -1c .RI "subroutine \fBztgevc\fP (side, howmny, select, n, s, lds, p, ldp, vl, ldvl, vr, ldvr, mm, m, work, rwork, info)" .br .RI "\fBZTGEVC\fP " .in -1c .SH "Function/Subroutine Documentation" .PP .SS "subroutine ztgevc (character side, character howmny, logical, dimension( * ) select, integer n, complex*16, dimension( lds, * ) s, integer lds, complex*16, dimension( ldp, * ) p, integer ldp, complex*16, dimension( ldvl, * ) vl, integer ldvl, complex*16, dimension( ldvr, * ) vr, integer ldvr, integer mm, integer m, complex*16, dimension( * ) work, double precision, dimension( * ) rwork, integer info)" .PP \fBZTGEVC\fP .PP \fBPurpose:\fP .RS 4 .PP .nf ZTGEVC computes some or all of the right and/or left eigenvectors of a pair of complex matrices (S,P), where S and P are upper triangular\&. Matrix pairs of this type are produced by the generalized Schur factorization of a complex matrix pair (A,B): A = Q*S*Z**H, B = Q*P*Z**H as computed by ZGGHRD + ZHGEQZ\&. The right eigenvector x and the left eigenvector y of (S,P) corresponding to an eigenvalue w are defined by: S*x = w*P*x, (y**H)*S = w*(y**H)*P, where y**H denotes the conjugate transpose of y\&. The eigenvalues are not input to this routine, but are computed directly from the diagonal elements of S and P\&. This routine returns the matrices X and/or Y of right and left eigenvectors of (S,P), or the products Z*X and/or Q*Y, where Z and Q are input matrices\&. If Q and Z are the unitary factors from the generalized Schur factorization of a matrix pair (A,B), then Z*X and Q*Y are the matrices of right and left eigenvectors of (A,B)\&. .fi .PP .RE .PP \fBParameters\fP .RS 4 \fISIDE\fP .PP .nf SIDE is CHARACTER*1 = 'R': compute right eigenvectors only; = 'L': compute left eigenvectors only; = 'B': compute both right and left eigenvectors\&. .fi .PP .br \fIHOWMNY\fP .PP .nf HOWMNY is CHARACTER*1 = 'A': compute all right and/or left eigenvectors; = 'B': compute all right and/or left eigenvectors, backtransformed by the matrices in VR and/or VL; = 'S': compute selected right and/or left eigenvectors, specified by the logical array SELECT\&. .fi .PP .br \fISELECT\fP .PP .nf SELECT is LOGICAL array, dimension (N) If HOWMNY='S', SELECT specifies the eigenvectors to be computed\&. The eigenvector corresponding to the j-th eigenvalue is computed if SELECT(j) = \&.TRUE\&.\&. Not referenced if HOWMNY = 'A' or 'B'\&. .fi .PP .br \fIN\fP .PP .nf N is INTEGER The order of the matrices S and P\&. N >= 0\&. .fi .PP .br \fIS\fP .PP .nf S is COMPLEX*16 array, dimension (LDS,N) The upper triangular matrix S from a generalized Schur factorization, as computed by ZHGEQZ\&. .fi .PP .br \fILDS\fP .PP .nf LDS is INTEGER The leading dimension of array S\&. LDS >= max(1,N)\&. .fi .PP .br \fIP\fP .PP .nf P is COMPLEX*16 array, dimension (LDP,N) The upper triangular matrix P from a generalized Schur factorization, as computed by ZHGEQZ\&. P must have real diagonal elements\&. .fi .PP .br \fILDP\fP .PP .nf LDP is INTEGER The leading dimension of array P\&. LDP >= max(1,N)\&. .fi .PP .br \fIVL\fP .PP .nf VL is COMPLEX*16 array, dimension (LDVL,MM) On entry, if SIDE = 'L' or 'B' and HOWMNY = 'B', VL must contain an N-by-N matrix Q (usually the unitary matrix Q of left Schur vectors returned by ZHGEQZ)\&. On exit, if SIDE = 'L' or 'B', VL contains: if HOWMNY = 'A', the matrix Y of left eigenvectors of (S,P); if HOWMNY = 'B', the matrix Q*Y; if HOWMNY = 'S', the left eigenvectors of (S,P) specified by SELECT, stored consecutively in the columns of VL, in the same order as their eigenvalues\&. Not referenced if SIDE = 'R'\&. .fi .PP .br \fILDVL\fP .PP .nf LDVL is INTEGER The leading dimension of array VL\&. LDVL >= 1, and if SIDE = 'L' or 'l' or 'B' or 'b', LDVL >= N\&. .fi .PP .br \fIVR\fP .PP .nf VR is COMPLEX*16 array, dimension (LDVR,MM) On entry, if SIDE = 'R' or 'B' and HOWMNY = 'B', VR must contain an N-by-N matrix Z (usually the unitary matrix Z of right Schur vectors returned by ZHGEQZ)\&. On exit, if SIDE = 'R' or 'B', VR contains: if HOWMNY = 'A', the matrix X of right eigenvectors of (S,P); if HOWMNY = 'B', the matrix Z*X; if HOWMNY = 'S', the right eigenvectors of (S,P) specified by SELECT, stored consecutively in the columns of VR, in the same order as their eigenvalues\&. Not referenced if SIDE = 'L'\&. .fi .PP .br \fILDVR\fP .PP .nf LDVR is INTEGER The leading dimension of the array VR\&. LDVR >= 1, and if SIDE = 'R' or 'B', LDVR >= N\&. .fi .PP .br \fIMM\fP .PP .nf MM is INTEGER The number of columns in the arrays VL and/or VR\&. MM >= M\&. .fi .PP .br \fIM\fP .PP .nf M is INTEGER The number of columns in the arrays VL and/or VR actually used to store the eigenvectors\&. If HOWMNY = 'A' or 'B', M is set to N\&. Each selected eigenvector occupies one column\&. .fi .PP .br \fIWORK\fP .PP .nf WORK is COMPLEX*16 array, dimension (2*N) .fi .PP .br \fIRWORK\fP .PP .nf RWORK is DOUBLE PRECISION array, dimension (2*N) .fi .PP .br \fIINFO\fP .PP .nf INFO is INTEGER = 0: successful exit\&. < 0: if INFO = -i, the i-th argument had an illegal value\&. .fi .PP .RE .PP \fBAuthor\fP .RS 4 Univ\&. of Tennessee .PP Univ\&. of California Berkeley .PP Univ\&. of Colorado Denver .PP NAG Ltd\&. .RE .PP .PP Definition at line \fB217\fP of file \fBztgevc\&.f\fP\&. .SH "Author" .PP Generated automatically by Doxygen for LAPACK from the source code\&.