LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
Loading...
Searching...
No Matches

◆ sgtsv()

subroutine sgtsv ( integer n,
integer nrhs,
real, dimension( * ) dl,
real, dimension( * ) d,
real, dimension( * ) du,
real, dimension( ldb, * ) b,
integer ldb,
integer info )

SGTSV computes the solution to system of linear equations A * X = B for GT matrices

Download SGTSV + dependencies [TGZ] [ZIP] [TXT]

Purpose:
!>
!> SGTSV  solves the equation
!>
!>    A*X = B,
!>
!> where A is an n by n tridiagonal matrix, by Gaussian elimination with
!> partial pivoting.
!>
!> Note that the equation  A**T*X = B  may be solved by interchanging the
!> order of the arguments DU and DL.
!>
Parameters
[in]N
!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>
[in]NRHS
!>          NRHS is INTEGER
!>          The number of right hand sides, i.e., the number of columns
!>          of the matrix B.  NRHS >= 0.
!>
[in,out]DL
!>          DL is REAL array, dimension (N-1)
!>          On entry, DL must contain the (n-1) sub-diagonal elements of
!>          A.
!>
!>          On exit, DL is overwritten by the (n-2) elements of the
!>          second super-diagonal of the upper triangular matrix U from
!>          the LU factorization of A, in DL(1), ..., DL(n-2).
!>
[in,out]D
!>          D is REAL array, dimension (N)
!>          On entry, D must contain the diagonal elements of A.
!>
!>          On exit, D is overwritten by the n diagonal elements of U.
!>
[in,out]DU
!>          DU is REAL array, dimension (N-1)
!>          On entry, DU must contain the (n-1) super-diagonal elements
!>          of A.
!>
!>          On exit, DU is overwritten by the (n-1) elements of the first
!>          super-diagonal of U.
!>
[in,out]B
!>          B is REAL array, dimension (LDB,NRHS)
!>          On entry, the N by NRHS matrix of right hand side matrix B.
!>          On exit, if INFO = 0, the N by NRHS solution matrix X.
!>
[in]LDB
!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!>
[out]INFO
!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -i, the i-th argument had an illegal value
!>          > 0: if INFO = i, U(i,i) is exactly zero, and the solution
!>               has not been computed.  The factorization has not been
!>               completed unless i = N.
!>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.