# cggbak.f(3) [centos man page]

cggbak.f(3) LAPACK cggbak.f(3)NAME

cggbak.f-SYNOPSIS

Functions/Subroutines subroutine cggbak (JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO) CGGBAKFunction/Subroutine Documentation subroutine cggbak (characterJOB, characterSIDE, integerN, integerILO, integerIHI, real, dimension( * )LSCALE, real, dimension( * )RSCALE, integerM, complex, dimension( ldv, * )V, integerLDV, integerINFO) CGGBAK Purpose: CGGBAK forms the right or left eigenvectors of a complex generalized eigenvalue problem A*x = lambda*B*x, by backward transformation on the computed eigenvectors of the balanced pair of matrices output by CGGBAL. Parameters: JOB JOB is CHARACTER*1 Specifies the type of backward transformation required: = 'N': do nothing, return immediately; = 'P': do backward transformation for permutation only; = 'S': do backward transformation for scaling only; = 'B': do backward transformations for both permutation and scaling. JOB must be the same as the argument JOB supplied to CGGBAL. SIDE SIDE is CHARACTER*1 = 'R': V contains right eigenvectors; = 'L': V contains left eigenvectors. N N is INTEGER The number of rows of the matrix V. N >= 0. ILO ILO is INTEGER IHI IHI is INTEGER The integers ILO and IHI determined by CGGBAL. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. LSCALE LSCALE is REAL array, dimension (N) Details of the permutations and/or scaling factors applied to the left side of A and B, as returned by CGGBAL. RSCALE RSCALE is REAL array, dimension (N) Details of the permutations and/or scaling factors applied to the right side of A and B, as returned by CGGBAL. M M is INTEGER The number of columns of the matrix V. M >= 0. V V is COMPLEX array, dimension (LDV,M) On entry, the matrix of right or left eigenvectors to be transformed, as returned by CTGEVC. On exit, V is overwritten by the transformed eigenvectors. LDV LDV is INTEGER The leading dimension of the matrix V. LDV >= max(1,N). INFO INFO is INTEGER = 0: successful exit. < 0: if INFO =, the i-th argument had an illegal value. Author: Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. Date: November 2011 Further Details: See R.C. Ward, Balancing the generalized eigenvalue problem, SIAM J. Sci. Stat. Comp. 2 (1981), 141-152. Definition at line 148 of file cggbak.f.-iAuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 cggbak.f(3)

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CGGBAK(l)) CGGBAK(l)NAME

CGGBAK - form the right or left eigenvectors of a complex generalized eigenvalue problem A*x = lambda*B*x, by backward transformation on the computed eigenvectors of the balanced pair of matrices output by CGGBALSYNOPSIS

SUBROUTINE CGGBAK( JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO ) CHARACTER JOB, SIDE INTEGER IHI, ILO, INFO, LDV, M, N REAL LSCALE( * ), RSCALE( * ) COMPLEX V( LDV, * )PURPOSE

CGGBAK forms the right or left eigenvectors of a complex generalized eigenvalue problem A*x = lambda*B*x, by backward transformation on the computed eigenvectors of the balanced pair of matrices output by CGGBAL.ARGUMENTS

JOB (input) CHARACTER*1 Specifies the type of backward transformation required: = 'N': do nothing, return immediately; = 'P': do backward transformation for permutation only; = 'S': do backward transformation for scaling only; = 'B': do backward transformations for both permutation and scaling. JOB must be the same as the argument JOB supplied to CGGBAL. SIDE (input) CHARACTER*1 = 'R': V contains right eigenvectors; = 'L': V contains left eigenvectors. N (input) INTEGER The number of rows of the matrix V. N >= 0. ILO (input) INTEGER IHI (input) INTEGER The integers ILO and IHI determined by CGGBAL. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. LSCALE (input) REAL array, dimension (N) Details of the permutations and/or scaling factors applied to the left side of A and B, as returned by CGGBAL. RSCALE (input) REAL array, dimension (N) Details of the permutations and/or scaling factors applied to the right side of A and B, as returned by CGGBAL. M (input) INTEGER The number of columns of the matrix V. M >= 0. V (input/output) COMPLEX array, dimension (LDV,M) On entry, the matrix of right or left eigenvectors to be transformed, as returned by CTGEVC. On exit, V is overwritten by the transformed eigenvectors. LDV (input) INTEGER The leading dimension of the matrix V. LDV >= max(1,N). INFO (output) INTEGER = 0: successful exit. < 0: if INFO =, the i-th argument had an illegal value.-iFURTHER DETAILS

See R.C. Ward, Balancing the generalized eigenvalue problem, SIAM J. Sci. Stat. Comp. 2 (1981), 141-152.LAPACK version 3.015 June 2000 CGGBAK(l)