cgeev.f
SUBROUTINE CGEEV (A, LDA, N, E, V, LDV, WORK, JOB, INFO)
C***BEGIN PROLOGUE CGEEV
C***PURPOSE Compute the eigenvalues and, optionally, the eigenvectors
C of a complex general matrix.
C***LIBRARY SLATEC
C***CATEGORY D4A4
C***TYPE COMPLEX (SGEEV-S, CGEEV-C)
C***KEYWORDS EIGENVALUES, EIGENVECTORS, GENERAL MATRIX
C***AUTHOR Kahaner, D. K., (NBS)
C Moler, C. B., (U. of New Mexico)
C Stewart, G. W., (U. of Maryland)
C***DESCRIPTION
C
C Abstract
C CGEEV computes the eigenvalues and, optionally,
C the eigenvectors of a general complex matrix.
C
C Call Sequence Parameters-
C (The values of parameters marked with * (star) will be changed
C by CGEEV.)
C
C A* COMPLEX(LDA,N)
C complex nonsymmetric input matrix.
C
C LDA INTEGER
C set by the user to
C the leading dimension of the complex array A.
C
C N INTEGER
C set by the user to
C the order of the matrices A and V, and
C the number of elements in E.
C
C E* COMPLEX(N)
C on return from CGEEV E contains the eigenvalues of A.
C See also INFO below.
C
C V* COMPLEX(LDV,N)
C on return from CGEEV if the user has set JOB
C = 0 V is not referenced.
C = nonzero the N eigenvectors of A are stored in the
C first N columns of V. See also INFO below.
C (If the input matrix A is nearly degenerate, V
C will be badly conditioned, i.e. have nearly
C dependent columns.)
C
C LDV INTEGER
C set by the user to
C the leading dimension of the array V if JOB is also
C set nonzero. In that case N must be .LE. LDV.
C If JOB is set to zero LDV is not referenced.
C
C WORK* REAL(3N)
C temporary storage vector. Contents changed by CGEEV.
C
C JOB INTEGER
C set by the user to
C = 0 eigenvalues only to be calculated by CGEEV.
C neither V nor LDV are referenced.
C = nonzero eigenvalues and vectors to be calculated.
C In this case A & V must be distinct arrays.
C Also, if LDA > LDV, CGEEV changes all the
C elements of A thru column N. If LDA < LDV,
C CGEEV changes all the elements of V through
C column N. If LDA = LDV only A(I,J) and V(I,
C J) for I,J = 1,...,N are changed by CGEEV.
C
C INFO* INTEGER
C on return from CGEEV the value of INFO is
C = 0 normal return, calculation successful.
C = K if the eigenvalue iteration fails to converge,
C eigenvalues K+1 through N are correct, but
C no eigenvectors were computed even if they were
C requested (JOB nonzero).
C
C Error Messages
C No. 1 recoverable N is greater than LDA
C No. 2 recoverable N is less than one.
C No. 3 recoverable JOB is nonzero and N is greater than LDV
C No. 4 warning LDA > LDV, elements of A other than the
C N by N input elements have been changed
C No. 5 warning LDA < LDV, elements of V other than the
C N by N output elements have been changed
C
C***REFERENCES (NONE)
C***ROUTINES CALLED CBABK2, CBAL, COMQR, COMQR2, CORTH, SCOPY, XERMSG
C***REVISION HISTORY (YYMMDD)
C 800808 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890531 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C***END PROLOGUE CGEEV