dsbgst.f (3)  Linux Manuals
NAME
dsbgst.f 
SYNOPSIS
Functions/Subroutines
subroutine dsbgst (VECT, UPLO, N, KA, KB, AB, LDAB, BB, LDBB, X, LDX, WORK, INFO)
DSBGST
Function/Subroutine Documentation
subroutine dsbgst (characterVECT, characterUPLO, integerN, integerKA, integerKB, double precision, dimension( ldab, * )AB, integerLDAB, double precision, dimension( ldbb, * )BB, integerLDBB, double precision, dimension( ldx, * )X, integerLDX, double precision, dimension( * )WORK, integerINFO)
DSBGST
Purpose:

DSBGST reduces a real symmetricdefinite banded generalized eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y, such that C has the same bandwidth as A. B must have been previously factorized as S**T*S by DPBSTF, using a split Cholesky factorization. A is overwritten by C = X**T*A*X, where X = S**(1)*Q and Q is an orthogonal matrix chosen to preserve the bandwidth of A.
Parameters:

VECT
VECT is CHARACTER*1 = 'N': do not form the transformation matrix X; = 'V': form X.
UPLOUPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored.
NN is INTEGER The order of the matrices A and B. N >= 0.
KAKA is INTEGER The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KA >= 0.
KBKB is INTEGER The number of superdiagonals of the matrix B if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KA >= KB >= 0.
ABAB is DOUBLE PRECISION array, dimension (LDAB,N) On entry, the upper or lower triangle of the symmetric band matrix A, stored in the first ka+1 rows of the array. The jth column of A is stored in the jth column of the array AB as follows: if UPLO = 'U', AB(ka+1+ij,j) = A(i,j) for max(1,jka)<=i<=j; if UPLO = 'L', AB(1+ij,j) = A(i,j) for j<=i<=min(n,j+ka). On exit, the transformed matrix X**T*A*X, stored in the same format as A.
LDABLDAB is INTEGER The leading dimension of the array AB. LDAB >= KA+1.
BBBB is DOUBLE PRECISION array, dimension (LDBB,N) The banded factor S from the split Cholesky factorization of B, as returned by DPBSTF, stored in the first KB+1 rows of the array.
LDBBLDBB is INTEGER The leading dimension of the array BB. LDBB >= KB+1.
XX is DOUBLE PRECISION array, dimension (LDX,N) If VECT = 'V', the nbyn matrix X. If VECT = 'N', the array X is not referenced.
LDXLDX is INTEGER The leading dimension of the array X. LDX >= max(1,N) if VECT = 'V'; LDX >= 1 otherwise.
WORKWORK is DOUBLE PRECISION array, dimension (2*N)
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 November 2011
Definition at line 159 of file dsbgst.f.
Author
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