LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  dsbgst (VECT, UPLO, N, KA, KB, AB, LDAB, BB, LDBB, X, LDX, WORK, INFO) 
DSBGST 
subroutine dsbgst  (  character  VECT, 
character  UPLO,  
integer  N,  
integer  KA,  
integer  KB,  
double precision, dimension( ldab, * )  AB,  
integer  LDAB,  
double precision, dimension( ldbb, * )  BB,  
integer  LDBB,  
double precision, dimension( ldx, * )  X,  
integer  LDX,  
double precision, dimension( * )  WORK,  
integer  INFO  
) 
DSBGST
Download DSBGST + dependencies [TGZ] [ZIP] [TXT]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.
[in]  VECT  VECT is CHARACTER*1 = 'N': do not form the transformation matrix X; = 'V': form X. 
[in]  UPLO  UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. 
[in]  N  N is INTEGER The order of the matrices A and B. N >= 0. 
[in]  KA  KA is INTEGER The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KA >= 0. 
[in]  KB  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. 
[in,out]  AB  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 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. 
[in]  LDAB  LDAB is INTEGER The leading dimension of the array AB. LDAB >= KA+1. 
[in]  BB  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 the array. 
[in]  LDBB  LDBB is INTEGER The leading dimension of the array BB. LDBB >= KB+1. 
[out]  X  X is DOUBLE PRECISION array, dimension (LDX,N) If VECT = 'V', the nbyn matrix X. If VECT = 'N', the array X is not referenced. 
[in]  LDX  LDX is INTEGER The leading dimension of the array X. LDX >= max(1,N) if VECT = 'V'; LDX >= 1 otherwise. 
[out]  WORK  WORK is DOUBLE PRECISION array, dimension (2*N) 
[out]  INFO  INFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value. 
Definition at line 159 of file dsbgst.f.