table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dgtrfs.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dgtrfs.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dgtrfs.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine DGTRFS (trans, n, nrhs, dl, d, du, dlf, df, duf,
du2, ipiv, b, ldb, x, ldx, ferr, berr, work, iwork, info)
DGTRFS
Function/Subroutine Documentation¶
subroutine DGTRFS (character trans, integer n, integer nrhs, double precision, dimension( * ) dl, double precision, dimension( * ) d, double precision, dimension( * ) du, double precision, dimension( * ) dlf, double precision, dimension( * ) df, double precision, dimension( * ) duf, double precision, dimension( * ) du2, integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b, integer ldb, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( * ) ferr, double precision, dimension( * ) berr, double precision, dimension( * ) work, integer, dimension( * ) iwork, integer info)¶
DGTRFS
Purpose:
!> !> DGTRFS improves the computed solution to a system of linear !> equations when the coefficient matrix is tridiagonal, and provides !> error bounds and backward error estimates for the solution. !>
Parameters
TRANS
!> TRANS is CHARACTER*1 !> Specifies the form of the system of equations: !> = 'N': A * X = B (No transpose) !> = 'T': A**T * X = B (Transpose) !> = 'C': A**H * X = B (Conjugate transpose = Transpose) !>
N
!> N is INTEGER !> The order of the matrix A. N >= 0. !>
NRHS
!> NRHS is INTEGER !> The number of right hand sides, i.e., the number of columns !> of the matrix B. NRHS >= 0. !>
DL
!> DL is DOUBLE PRECISION array, dimension (N-1) !> The (n-1) subdiagonal elements of A. !>
D
!> D is DOUBLE PRECISION array, dimension (N) !> The diagonal elements of A. !>
DU
!> DU is DOUBLE PRECISION array, dimension (N-1) !> The (n-1) superdiagonal elements of A. !>
DLF
!> DLF is DOUBLE PRECISION array, dimension (N-1) !> The (n-1) multipliers that define the matrix L from the !> LU factorization of A as computed by DGTTRF. !>
DF
!> DF is DOUBLE PRECISION array, dimension (N) !> The n diagonal elements of the upper triangular matrix U from !> the LU factorization of A. !>
DUF
!> DUF is DOUBLE PRECISION array, dimension (N-1) !> The (n-1) elements of the first superdiagonal of U. !>
DU2
!> DU2 is DOUBLE PRECISION array, dimension (N-2) !> The (n-2) elements of the second superdiagonal of U. !>
IPIV
!> IPIV is INTEGER array, dimension (N) !> The pivot indices; for 1 <= i <= n, row i of the matrix was !> interchanged with row IPIV(i). IPIV(i) will always be either !> i or i+1; IPIV(i) = i indicates a row interchange was not !> required. !>
B
!> B is DOUBLE PRECISION array, dimension (LDB,NRHS) !> The right hand side matrix B. !>
LDB
!> LDB is INTEGER !> The leading dimension of the array B. LDB >= max(1,N). !>
X
!> X is DOUBLE PRECISION array, dimension (LDX,NRHS) !> On entry, the solution matrix X, as computed by DGTTRS. !> On exit, the improved solution matrix X. !>
LDX
!> LDX is INTEGER !> The leading dimension of the array X. LDX >= max(1,N). !>
FERR
!> FERR is DOUBLE PRECISION array, dimension (NRHS) !> The estimated forward error bound for each solution vector !> X(j) (the j-th column of the solution matrix X). !> If XTRUE is the true solution corresponding to X(j), FERR(j) !> is an estimated upper bound for the magnitude of the largest !> element in (X(j) - XTRUE) divided by the magnitude of the !> largest element in X(j). The estimate is as reliable as !> the estimate for RCOND, and is almost always a slight !> overestimate of the true error. !>
BERR
!> BERR is DOUBLE PRECISION array, dimension (NRHS) !> The componentwise relative backward error of each solution !> vector X(j) (i.e., the smallest relative change in !> any element of A or B that makes X(j) an exact solution). !>
WORK
!> WORK is DOUBLE PRECISION array, dimension (3*N) !>
IWORK
!> IWORK is INTEGER array, dimension (N) !>
INFO
!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value !>
Internal Parameters:
!> ITMAX is the maximum number of steps of iterative refinement. !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 206 of file dgtrfs.f.
Author¶
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