SSIEV(3)

SYNOPSIS
SUBROUTINE SSIEV (A, LDA, N, E, WORK, JOB, INFO)

NAME
ssiev - Compute the eigenvalues and, optionally, the eigenvectors of a real symmetric matrix.

LIBRARY
SLATEC

CATEGORY
D4A1

TYPE
SINGLE PRECISION (SSIEV-S, CHIEV-C)

KEYWORDS
COMPLEX HERMITIAN, EIGENVALUES, EIGENVECTORS, MATRIX, SYMMETRIC

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

DESCRIPTION
Abstract SSIEV computes the eigenvalues and, optionally, the eigenvectors of a real symmetric matrix. Call Sequence Parameters- (The values of parameters marked with * (star) will be changed by SSIEV.) A* REAL (LDA,N) real symmetric input matrix. Only the diagonal and upper triangle of A must be input, as SSIEV copies the upper triangle to the lower. That is, the user must define A(I,J), I=1,..N, and J=I,. On return from SSIEV, if the user has set JOB = 0 the lower triangle of A has been altered. = nonzero the N eigenvectors of A are stored in its first N columns. See also INFO below. LDA INTEGER set by the user to the leading dimension of the array A. N INTEGER set by the user to the order of the matrix A and the number of elements in E. E* REAL (N) on return from SSIEV, E contains the N eigenvalues of A. See also INFO below. WORK* REAL (2*N) temporary storage vector. Contents changed by SSIEV. JOB INTEGER set by user on input = 0 only calculate eigenvalues of A. = nonzero calculate eigenvalues and eigenvectors of A. INFO* INTEGER on return from SSIEV, the value of INFO is = 0 for normal return. = K if the eigenvalue iteration fails to converge. eigenvalues and vectors 1 through K-1 are correct. Error Messages- No. 1 recoverable N is greater than LDA No. 2 recoverable N is less than one

REFERENCES
(NONE)

ROUTINES CALLED
IMTQL2, TQLRAT, TRED1, TRED2, XERMSG

REVISION HISTORY (YYMMDD)
800808 DATE WRITTEN
890831 Modified array declarations. (WRB)
890831 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)