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SUBROUTINE RSB(NM,N,MB,A,W,MATZ,Z,FV1,FV2,IERR)
C
INTEGER N,MB,NM,IERR,MATZ
DOUBLE PRECISION A(NM,MB),W(N),Z(NM,N),FV1(N),FV2(N)
LOGICAL TF
C
C THIS SUBROUTINE CALLS THE RECOMMENDED SEQUENCE OF
C SUBROUTINES FROM THE EIGENSYSTEM SUBROUTINE PACKAGE (EISPACK)
C TO FIND THE EIGENVALUES AND EIGENVECTORS (IF DESIRED)
C OF A REAL SYMMETRIC BAND MATRIX.
C
C ON INPUT
C
C NM MUST BE SET TO THE ROW DIMENSION OF THE TWO-DIMENSIONAL
C ARRAY PARAMETERS AS DECLARED IN THE CALLING PROGRAM
C DIMENSION STATEMENT.
C
C N IS THE ORDER OF THE MATRIX A.
C
C MB IS THE HALF BAND WIDTH OF THE MATRIX, DEFINED AS THE
C NUMBER OF ADJACENT DIAGONALS, INCLUDING THE PRINCIPAL
C DIAGONAL, REQUIRED TO SPECIFY THE NON-ZERO PORTION OF THE
C LOWER TRIANGLE OF THE MATRIX.
C
C A CONTAINS THE LOWER TRIANGLE OF THE REAL SYMMETRIC
C BAND MATRIX. ITS LOWEST SUBDIAGONAL IS STORED IN THE
C LAST N+1-MB POSITIONS OF THE FIRST COLUMN, ITS NEXT
C SUBDIAGONAL IN THE LAST N+2-MB POSITIONS OF THE
C SECOND COLUMN, FURTHER SUBDIAGONALS SIMILARLY, AND
C FINALLY ITS PRINCIPAL DIAGONAL IN THE N POSITIONS
C OF THE LAST COLUMN. CONTENTS OF STORAGES NOT PART
C OF THE MATRIX ARE ARBITRARY.
C
C MATZ IS AN INTEGER VARIABLE SET EQUAL TO ZERO IF
C ONLY EIGENVALUES ARE DESIRED. OTHERWISE IT IS SET TO
C ANY NON-ZERO INTEGER FOR BOTH EIGENVALUES AND EIGENVECTORS.
C
C ON OUTPUT
C
C W CONTAINS THE EIGENVALUES IN ASCENDING ORDER.
C
C Z CONTAINS THE EIGENVECTORS IF MATZ IS NOT ZERO.
C
C IERR IS AN INTEGER OUTPUT VARIABLE SET EQUAL TO AN ERROR
C COMPLETION CODE DESCRIBED IN THE DOCUMENTATION FOR TQLRAT
C AND TQL2. THE NORMAL COMPLETION CODE IS ZERO.
C
C FV1 AND FV2 ARE TEMPORARY STORAGE ARRAYS.
C
C QUESTIONS AND COMMENTS SHOULD BE DIRECTED TO BURTON S. GARBOW,
C MATHEMATICS AND COMPUTER SCIENCE DIV, ARGONNE NATIONAL LABORATORY
C
C THIS VERSION DATED AUGUST 1983.
C
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C