CGEEV(3)

SYNOPSIS
SUBROUTINE CGEEV (A, LDA, N, E, V, LDV, WORK, JOB, INFO)

NAME
cgeev - Compute the eigenvalues and, optionally, the eigenvectors of a complex general matrix.

LIBRARY
SLATEC

CATEGORY
D4A4

TYPE
COMPLEX (SGEEV-S, CGEEV-C)

KEYWORDS
EIGENVALUES, EIGENVECTORS, GENERAL MATRIX

AUTHOR
Kahaner, D. K., (NBS) Moler, C. B., (U. of New Mexico) Stewart, G. W., (U. of Maryland)

DESCRIPTION
Abstract CGEEV computes the eigenvalues and, optionally, the eigenvectors of a general complex matrix. Call Sequence Parameters- (The values of parameters marked with * (star) will be changed by CGEEV.) A* COMPLEX(LDA,N) complex nonsymmetric input matrix. LDA INTEGER set by the user to the leading dimension of the complex array A. N INTEGER set by the user to the order of the matrices A and V, and the number of elements in E. E* COMPLEX(N) on return from CGEEV E contains the eigenvalues of A. See also INFO below. V* COMPLEX(LDV,N) on return from CGEEV if the user has set JOB = 0 V is not referenced. = nonzero the N eigenvectors of A are stored in the first N columns of V. See also INFO below. (If the input matrix A is nearly degenerate, V will be badly conditioned, i.e. have nearly dependent columns.) LDV INTEGER set by the user to the leading dimension of the array V if JOB is also set nonzero. In that case N must be .LE. LDV. If JOB is set to zero LDV is not referenced. WORK* REAL(3N) temporary storage vector. Contents changed by CGEEV. JOB INTEGER set by the user to = 0 eigenvalues only to be calculated by CGEEV. neither V nor LDV are referenced. = nonzero eigenvalues and vectors to be calculated. In this case A & V must be distinct arrays. Also, if LDA > LDV, CGEEV changes all the elements of A thru column N. If LDA < LDV, CGEEV changes all the elements of V through column N. If LDA = LDV only A(I,J) and V(I, J) for I,J = 1,...,N are changed by CGEEV. INFO* INTEGER on return from CGEEV the value of INFO is = 0 normal return, calculation successful. = K if the eigenvalue iteration fails to converge, eigenvalues K+1 through N are correct, but no eigenvectors were computed even if they were requested (JOB nonzero). Error Messages No. 1 recoverable N is greater than LDA No. 2 recoverable N is less than one. No. 3 recoverable JOB is nonzero and N is greater than LDV No. 4 warning LDA > LDV, elements of A other than the N by N input elements have been changed No. 5 warning LDA < LDV, elements of V other than the N by N output elements have been changed

REFERENCES
(NONE)

ROUTINES CALLED
CBABK2, CBAL, COMQR, COMQR2, CORTH, SCOPY, XERMSG

REVISION HISTORY (YYMMDD)
800808 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890531 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
900326 Removed duplicate information from DESCRIPTION section. (WRB)