dsbgst.f(3) LAPACK dsbgst.f(3)
subroutine dsbgst (VECT, UPLO, N, KA, KB, AB, LDAB, BB, LDBB, X, LDX, WORK, INFO)
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 reduces a real symmetric-definite 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.
VECT is CHARACTER*1
= 'N': do not form the transformation matrix X;
= 'V': form X.
UPLO is CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N is INTEGER
The order of the matrices A and B. N >= 0.
KA is INTEGER
The number of superdiagonals of the matrix A if UPLO = 'U',
or the number of subdiagonals if UPLO = 'L'. KA >= 0.
KB is INTEGER
The number of superdiagonals of the matrix B if UPLO = 'U',
or the number of subdiagonals if UPLO = 'L'. KA >= KB >= 0.
AB 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
j-th column of A is stored in the j-th column of the array AB
if UPLO = 'U', AB(ka+1+i-j,j) = A(i,j) for max(1,j-ka)<=i<=j;
if UPLO = 'L', AB(1+i-j,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.
LDAB is INTEGER
The leading dimension of the array AB. LDAB >= KA+1.
BB 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
LDBB is INTEGER
The leading dimension of the array BB. LDBB >= KB+1.
X is DOUBLE PRECISION array, dimension (LDX,N)
If VECT = 'V', the n-by-n matrix X.
If VECT = 'N', the array X is not referenced.
LDX is INTEGER
The leading dimension of the array X.
LDX >= max(1,N) if VECT = 'V'; LDX >= 1 otherwise.
WORK is DOUBLE PRECISION array, dimension (2*N)
INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
Definition at line 159 of file dsbgst.f.
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 dsbgst.f(3)